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Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
• 1. Agarwalla, S.K.
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik. KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik.
EUROnu-WP6 2010 Report2012Rapport (Övrigt vetenskapligt)

This is a summary of the work done by the Working Package 6 (Physics) of the EU project "EUROnu" during the second year of activity of the project.

• 2.
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik.
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik. KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik.
Comment on "Is Dark Matter with Long-Range Interactions a Solution to All Small-Scale Problems of Λ Cold Dark Matter Cosmology?"2013Ingår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 111, nr 19, s. 199001-Artikel i tidskrift (Refereegranskat)
• 3.
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik.
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik. KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik. KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik. KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik.
Stability and leptogenesis in the left-right symmetric seesaw mechanism2007Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, Vol. 4, s. 022-1-022-25Artikel i tidskrift (Refereegranskat)

We analyze the left-right symmetric type I+II seesaw mechanism, where an eight-fold degeneracy among the mass matrices of heavy right-handed neutrinos M-R is known to exist. Using the stability property of the solutions and their ability to lead to successful baryogenesis via leptogenesis as additional criteria, we discriminate among these eight solutions and partially lift their eight-fold degeneracy. In particular, we find that viable leptogenesis is generically possible for four out of the eight solutions.

• 4. Akhmedov, Evgeny
KTH, Tidigare Institutioner, Fysik.
T violation in neutrino oscillations in matter2001Ingår i: Nuclear Physics B, ISSN 0550-3213, E-ISSN 1873-1562, Vol. 608, nr 02-jan, s. 394-422Artikel i tidskrift (Refereegranskat)

We consider the interplay of fundamental and matter-induced T violation effects in neutrino oscillations in matter. After discussing the general features of these effects we derive a simple approximate analytic expression for the T-violating probability asymmetry DeltaP(ab)(T) for three-flavour neutrino oscillations in a matter with an arbitrary density profile in terms of the two-flavour neutrino amplitudes. Explicit examples are given for the cases of a two-layer medium and for the adiabatic Emit in the general case. We then discuss implications of the obtained results for long baseline experiments. We show, in particular, that asymmetric matter effects cannot hinder the determination of the fundamental CP- and T-violating phase delta (CP) in the long baseline experiments as far as the error in this determination is larger than 1% at 99% CL. Since there are no T-violating effects in the two-flavour case, and in the limits of vanishing theta (13) or Deltam(21)(2) the three-flavour neutrino oscillations effectively reduce to the two-flavour ones, studying the T-violating asymmetries ApT ab can in principle provide us with a complementary means of measuring theta (13) and Deltam(21)(2).

• 5. Akhmedov, Evgeny K.
KTH, Tidigare Institutioner, Fysik. KTH, Tidigare Institutioner, Fysik.
Series expansions for three-flavor neutrino oscillation probabilities in matter2004Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, Vol. 2004, nr 04, s. 078-Artikel i tidskrift (Refereegranskat)

We present a number of complete sets of series expansion formulas for neutrino oscillation probabilities in matter of constant density for three flavors. In particular, we study expansions in the mass hierarchy parameter alpha = Deltam(21)(2)/Deltam(31)(2) and mixing parameter s(13) = sin theta(13) up to second order and expansions only in alpha and only in s(13) up to first order. For each type of expansion we also present the corresponding formulas for neutrino oscillations in vacuum. We perform a detailed analysis of the accuracy of the different sets of series expansion formulas and investigate which type of expansion is most accurate in different regions of the parameter space spanned by the neutrino energy E, the baseline length L, and the expansion parameters alpha and s(13). We also present the formulas for series expansions in alpha and in s(13) up to first order for the case of arbitrary matter density profiles. Furthermore, it is shown that in general all the 18 neutrino and antineutrino oscillation probabilities can be expressed through just two independent probabilities.

• 6. Baussan, E.
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik. KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik.
A very intense neutrino super beam experiment for leptonic CP violation discovery based on the European spallation source linac2014Ingår i: Nuclear Physics B, ISSN 0550-3213, E-ISSN 1873-1562, Vol. 885, s. 127-149Artikel i tidskrift (Refereegranskat)

Very intense neutrino beams and large neutrino detectors will be needed in order to enable the discovery of CP violation in the leptonic sector. We propose to use the proton linac of the European Spoliation Source currently under construction in Lund, Sweden, to deliver, in parallel with the spoliation neutron production, a very intense, cost effective and high performance neutrino beam. The baseline program for the European Spoliation Source linac is that it will be fully operational at 5 MW average power by 2022, producing 2 GeV 2.86 ms long proton pulses at a rate of 14 Hz. Our proposal is to upgrade the linac to 10 MW average power and 28 Hz, producing 14 pulses/s for neutron production and 14 pulses/s for neutrino production. Furthermore, because of the high current required in the pulsed neutrino horn, the length of the pulses used for neutrino production needs to be compressed to a few mu s with the aid of an accumulator ring. A long baseline experiment using this Super Beam and a megaton underground Water Cherenkov detector located in existing mines 300-600 km from Lund will make it possible to discover leptonic CP violation at 5 sigma significance level in up to 50% of the leptonic Dirac CP-violating phase range. This experiment could also determine the neutrino mass hierarchy at a significance level of more than 3 sigma if this issue will not already have been settled by other experiments by then. The mass hierarchy performance could be increased by combining the neutrino beam results with those obtained from atmospheric neutrinos detected by the same large volume detector. This detector will also be used to measure the proton lifetime, detect cosmological neutrinos and neutrinos from supernova explosions. Results on the sensitivity to leptonic CP violation and the neutrino mass hierarchy are presented.

• 7.
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik.
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik. KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik. KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik.
Renormalization group running of neutrino parameters in the inverse seesaw model2010Ingår i: Physical Review D, ISSN 1550-7998, Vol. 81, nr 11, s. 116006-Artikel i tidskrift (Refereegranskat)

We perform a detailed study of the renormalization group equations in the inverse seesaw model. Especially, we derive compact analytical formulas for the running of the neutrino parameters in the standard model and the minimal supersymmetric standard model, and illustrate that, due to large Yukawa coupling corrections, significant running effects on the leptonic mixing angles can be naturally obtained in the proximity of the electroweak scale, perhaps even within the reach of the LHC. In general, if the mass spectrum of the light neutrinos is nearly degenerate, the running effects are enhanced to experimentally accessible levels, well suitable for the investigation of the underlying dynamics behind the neutrino mass generation and the lepton flavor structure. In addition, the effects of the seesaw thresholds are discussed, and a brief comparison to other seesaw models is carried out.

• 8.
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik.
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik. KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik.
Constraining new physics with a positive or negative signal of neutrino-less double beta decay2011Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, Vol. 2011, nr 05, s. 122-Artikel i tidskrift (Refereegranskat)

We investigate numerically how accurately one could constrain the strengths of different short-range contributions to neutrino-less double beta decay in effective field theory. Depending on the outcome of near-future experiments yielding information on the neutrino masses, the corresponding bounds or estimates can be stronger or weaker. A particularly interesting case, resulting in strong bounds, would be a positive signal of neutrino-less double beta decay that is consistent with complementary information from neutrino oscillation experiments, kinematical determinations of the neutrino mass, and measurements of the sum of light neutrino masses from cosmological observations. The keys to more robust bounds are improvements of the knowledge of the nuclear physics involved and a better experimental accuracy.

• 9.
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik.
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik.
Unparticle self-interactions at the Large Hadron Collider2009Ingår i: Physical Review D. Particles, fields, gravitation and cosmology, ISSN 1550-7998, Vol. 80, nr 11, s. 115014-Artikel i tidskrift (Refereegranskat)

We investigate the effect of unparticle self-interactions at the Large Hadron Collider (LHC). Especially, we discuss the three-point correlation function, which is determined by conformal symmetry up to a constant, and study its relation to processes with four-particle final states. These processes could be used as a favorable way to look for unparticle physics, and for weak enough couplings to the standard model, even the only way. We find updated upper bounds on the cross sections for unparticle-mediated 4 gamma final states at the LHC and novel upper bounds for the corresponding 2 gamma 2l and 4l final states. The size of the allowed cross sections obtained are comparably large for large values of the scaling dimension of the unparticle sector, but they decrease with decreasing values of this parameter. In addition, we present relevant distributions for the different final states, enabling the possible identification of the unparticle scaling dimension if there was to be a large number of events of such final states at the LHC.

• 10.
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik.
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik. KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik.
Threshold effects on renormalization group running of neutrino parameters in the low-scale seesaw model2011Ingår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 698, nr 4, s. 297-305Artikel i tidskrift (Refereegranskat)

We show that, in the low-scale type-I seesaw model, renormalization group running of neutrino parameters may lead to significant modifications of the leptonic mixing angles in view of so-called seesaw threshold effects. Especially, we derive analytical formulas for radiative corrections to neutrino parameters in crossing the different seesaw thresholds, and show that there may exist enhancement factors efficiently boosting the renormalization group running of the leptonic mixing angles. We find that, as a result of the seesaw threshold corrections to the leptonic mixing angles, various flavor symmetric mixing patterns (e.g., bi-maximal and tri-bimaximal mixing patterns) can be easily accommodated at relatively low energy scales, which is well within the reach of running and forthcoming experiments (e.g., the LHC).

• 11. Bergström, Lars
Botner, OlgaCarlson, PerHulth, Per OlofOhlsson, TommyKTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik.
Neutrino Physics: Proceedings of Nobel Symposium 1292006Proceedings (redaktörskap) (Refereegranskat)

PREFACE

Nobel Symposium 129 on Neutrino Physics was held at Haga Slott in Enköping, Sweden during August 19–24, 2004. Invited to the symposium were around 40 globally leading researchers in the field of neutrino physics, both experimental and theoretical. In addition to these participants, some 30 local researchers and graduate students participated in the symposium.

The dominant theme of the lectures was neutrino oscillations, which after several years were recently verified by results from the Super-Kamiokande detector in Kamioka, Japan and the SNO detector in Sudbury, Canada. Discussion focused especially on effects of neutrino oscillations derived from the presence of matter and the fact that three different neutrinos exist. Since neutrino oscillations imply that neutrinos have mass, this is the first experimental observation that fundamentally deviates from the standard model of particle physics. This is a challenge to both theoretical and experimental physics. The various oscillation parameters will be determined with increased precision in new, specially designed experiments. Theoretical physics is working intensively to insert the knowledge that neutrinos have mass into the theoretical models that describe particle physics. It will probably turn out that the discovery of neutrino oscillations signifies a breakthrough in the description of the very smallest constituents of matter. The lectures provided a very good description of the intensive situation in the field right now. The topics discussed also included mass models for neutrinos, neutrinos in extra dimensions as well as the `seesaw mechanism', which provides a good description of why neutrino masses are so small.

Also discussed, besides neutrino oscillations, was the new field of neutrino astronomy. Among the questions that neutrino astronomy hopes to answer are what the dark matter in the Universe consists of and where cosmic radiation at extremely high energies comes from. For this purpose, large neutrino telescopes are built deep in the Antarctic ice, in the Baikal Lake, and in the Mediterranean Sea.

Among prominent unanswered questions, highlighted as one of the most important, was whether neutrinos are Dirac or Majorana particles. By studying neutrino double beta decay, researchers hope to answer this question, but it will put very large demands on detectors.

The programme also included ample time for lively and valuable discussions, which cannot normally be held at ordinary conferences.

The symposium concluded with a round-table discussion, where participants discussed the future of neutrino physics.Without a doubt, neutrino physics today is moving toward a very exciting and interesting period.

An important contribution to the success of the symposium was the wonderful setting that the Haga Slott manor house hotel and conference center offered to the participants.

• 12. Bilenky, Samoil M.
KTH, Tidigare Institutioner, Fysik.
Tests of CPT invariance at neutrino factories2002Ingår i: Physical Review D. Particles and fields, ISSN 0556-2821, E-ISSN 1089-4918, Vol. 65, nr 7, s. 073024-1-073024-6Artikel i tidskrift (Refereegranskat)

We investigate possible tests of CPT invariance on the level of event rates at neutrino factories. We do not assume any specific model but phenomenological differences in the neutrino-antineutrino masses and mixing angles in a Lorentz invariance preserving context, such as could be induced by physics beyond the standard model. We especially focus on the muon neutrino and antineutrino disappearance channels in order to obtain constraints on the neutrino-antineutrino mass and mixing angle differences; we found, for example, that the sensitivity \m(3)-(m) over bar (3)\less than or similar to1.9x10(-4) eV could be achieved.

• 13.
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik.
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik. KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik. KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik.
A combined study of source, detector and matter non-standard neutrino interactions at DUNE2016Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, Vol. 2016, nr 8, artikel-id 90Artikel i tidskrift (Refereegranskat)

We simultaneously investigate source, detector and matter non-standard neutrino interactions at the proposed DUNE experiment. Our analysis is performed using a Markov Chain Monte Carlo exploring the full parameter space. We find that the sensitivity of DUNE to the standard oscillation parameters is worsened due to the presence of non-standard neutrino interactions. In particular, there are degenerate solutions in the leptonic mixing angle θ23 and the Dirac CP-violating phase δ. We also compute the expected sensitivities at DUNE to the non-standard interaction parameters. We find that the sensitivities to the matter non-standard interaction parameters are substantially stronger than the current bounds (up to a factor of about 15). Furthermore, we discuss correlations between the source/detector and matter non-standard interaction parameters and find a degenerate solution in θ23. Finally, we explore the effect of statistics on our results.

• 14.
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik.
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik. Harish-Chandra Research Institute, Chhatnag Road, Jhunsi, Allahabad, India. KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik. KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik.
Exploring source and detector non-standard neutrino interactions at ESS nu SB2015Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 9, artikel-id 096Artikel i tidskrift (Refereegranskat)

We investigate source and detector non-standard neutrino interactions at the proposed ESS nu SB experiment. We analyze the effect of non-standard physics at the probability level, the event-rate level and by a full computation of the ESS nu SB setup. We find that the precision measurement of the leptonic mixing angle theta(23) at ESS nu SB is robust in the presence of non-standard interactions, whereas that of the leptonic CP-violating phase delta is worsened at most by a factor of two. We compute sensitivities to all the relevant source and decector non-standard interaction parameters and find that the sensitivities to the parameters epsilon(s)(mu e) and epsilon(d)(mu e) are comparable to the existing limits in a realistic scenario, while they improve by a factor of two in an optimistic scenario. Finally, we show that the absence of a near detector compromises the sensitivity of ESS nu SB to non-standard interactions.

• 15.
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik.
Fysikum, Stockholm University. KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik.
Neutrinos from WIMP annihilations in the Sun including neutrino oscillations2011Ingår i: The Proceedings of the 22nd International Conference on Neutrino Physics and Astrophysics / [ed] Geoffrey Mills, Steve Elliott, Terrence Goldman, and Thomas Bowles, Elsevier, 2011, Vol. 221, s. 37-38Konferensbidrag (Refereegranskat)

The prospects to detect neutrinos from the Sun arising from dark matter annihilations in the core of the Sun are reviewed. Emphasis is placed on new work investigating the effects of neutrino oscillations on the expected neutrino fluxes.

• 16.
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik.
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik.
Neutrinos from WIMP annihilations in the Sun including neutrino oscillations2006Ingår i: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T127, s. 19-21Artikel i tidskrift (Refereegranskat)

The prospects for detecting neutrinos from the Sun arising from dark matter annihilations in the core of the Sun are reviewed. Emphasis is placed on new work investigating the effects of neutrino oscillations on the expected neutrino fluxes.

• 17.
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik.
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik.
Neutrinos from WIMP annihilations obtained using a full three-flavor Monte Carlo approach2008Ingår i: Journal of Cosmology and Astroparticle Physics, ISSN 1475-7516, E-ISSN 1475-7516, Vol. 2008, nr 01, s. 021-Artikel i tidskrift (Refereegranskat)

Weakly interacting massive particles (WIMPs) are one of the main candidates for making up the dark matter in the Universe. If these particles make up the dark matter, then they can be captured by the Sun or the Earth, sink to the respective cores, annihilate, and produce neutrinos. Thus, these neutrinos can be a striking dark matter signature at neutrino telescopes looking towards the Sun and/or the Earth. Here, we improve previous analyses on computing the neutrino yields from WIMP annihilations in several respects. We include neutrino oscillations in a full three-flavor framework as well as all effects from neutrino interactions on the way through the Sun (absorption, energy loss, and regeneration from tau decays). In addition, we study the effects of non-zero values of the mixing angle theta(13) as well as the normal and inverted neutrino mass hierarchies. Our study is performed in an event-based setting which makes these results very useful both for theoretical analyses and for building a neutrino telescope Monte Carlo code. All our results for the neutrino yields, as well as our Monte Carlo code, are publicly available. We find that the yield of muontype neutrinos from WIMP annihilations in the Sun is enhanced or suppressed, depending on the dominant WIMP annihilation channel. This effect is due to an effective favor mixing caused by neutrino oscillations. For WIMP annihilations inside the Earth, the distance from source to detector is too small to allow for any significant amount of oscillations at the neutrino energies relevant for neutrino telescopes.

• 18.
Max-Planck-Institut für Physik.
Department of Physics, Stockholm University. KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik.
WIMP neutrinos from the Sun and the Earth2008Ingår i: : idm2008, SISSA , 2008, s. 4p-Konferensbidrag (Refereegranskat)

We discuss the propagation treatment of the indirect dark matter detection using WIMP annihilations in the Sun and the Earth. In particular, we focus on treating neutrino interactions and oscillations in a consistent framework, including tau neutrino regeneration and a full three-flavor neutrino oscillation framework. We also discuss the equivalence of using a Monte Carlo approach - suited for inclusion in neutrino telescope Monte Carlos - and the density matrix formalism.

• 19.
Max-Planck-Institut für Physik (Werner-Heisenberg-Institut), München, Germany.
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik. KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik.
Neutrinos from Kaluza-Klein dark matter in the Sun2010Ingår i: Journal of Cosmology and Astroparticle Physics, ISSN 1475-7516, Vol. 2010, nr 01, s. 018-Artikel i tidskrift (Refereegranskat)

We investigate indirect neutrino signals from annihilations of Kaluza-Klein dark matter in the Sun. Especially, we examine a five- as well as a six-dimensional model, and allow for the possibility that boundary localized terms could affect the spectrum to give different lightest Kaluza-Klein particles, which could constitute the dark matter. The dark matter candidates that are interesting for the purpose of indirect detection of neutrinos are the first Kaluza-Klein mode of the U(1) gauge boson and the neutral component of the SU(2) gauge bosons. Using the DarkSUSY and WimpSim packages, we calculate muon fluxes at an Earth-based neutrino telescope, such as IceCube. For the five-dimensional model, the results hat we obtained agree reasonably well with the results that have previously been presented in the literature, whereas for the six-dimensional model, we find that, at tree-level, the results are the same as for the five-dimensional model. Finally, if the first Kaluza-Klein mode of the U(1) gauge boson constitutes the dark matter, IceCube can constrain the parameter space. However, in the case that the neutral component of the SU(2) gauge bosons is the LKP, the signal is too weak to be observed.

• 20.
Max-Planck-Institut für Physik (Werner-Heisenberg-Institut), München, Germany.
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik. KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik. KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik.
Non-unitary neutrino mixing from an extra-dimensional seesaw model2010Manuskript (preprint) (Övrigt vetenskapligt)

We study the generation of light neutrino masses in an extra-dimensional model, where right-handed neutrinos are allowed to propagate in the extra dimension, while the Standard model (SM) particles are confined to a brane. Motivated by the fact that extra-dimensional models are non-renormalizable, we truncate the Kaluza–Klein (KK) towers at a maximal KK index. The structure of the bulk Majorana mass term, motivated by the Sherk–Schwarz mechanism, implies that the right-handed KK neutrinos pair to form Dirac neutrinos, except for a number of unpaired Majorana neutrinos at the top of each tower. These heavy Majorana neutrinos are the only sources of lepton number breaking in the model, and similarly to the type-I seesaw mechanism, they naturally generate small masses for the left-handed neutrinos. The lower KK modes mix with the light neutrinos, and the mixing effects are not suppressed with respect to the light neutrino masses. Compared to conventional fermionic seesaw models, the non-unitary effects induced by such mixing are quite significant. We study the signals of this model at the Large Hadron Collider (LHC), and find that the current bounds on the non-unitarity parameters are strong enough to exclude an observation.

• 21. Blennow, Mattias
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik. KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik.
Renormalization group running of the neutrino mass operator in extra dimensions2011Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, Vol. 2011, nr 04, s. 052-Artikel i tidskrift (Refereegranskat)

We study the renormalization group (RG) running of the neutrino masses and the leptonic mixing parameters in two different extra-dimensional models, namely, the Universal Extra Dimensions (UED) model and a model, where the Standard Model (SM) bosons probe an extra dimension and the SM fermions are confined to a four-dimensional brane. In particular, we derive the beta function for the neutrino mass operator in the UED model. We also rederive the beta function for the charged-lepton Yukawa coupling, and confirm some of the existing results in the literature. The generic features of the RG running of the neutrino parameters within the two models are analyzed and, in particular, we observe a power-law behavior for the running. We note that the running of the leptonic mixing angle theta(12) can be sizable, while the running of theta(23) and theta(13) is always negligible. In addition, we show that the tri-bimaximal and the bimaximal mixing patterns at a high-energy scale are compatible with low-energy experimental data, while a tri-small mixing pattern is not. Finally, we perform a numerical scan over the low-energy parameter space to infer the high-energy distribution of the parameters. Using this scan, we also demonstrate how the high-energy theta(12) is correlated with the smallest neutrino mass and the Majorana phases.

• 22. Blennow, Mattias
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik. KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik.
RG running in a minimal UED model in light of recent LHC Higgs mass bounds2012Ingår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 712, nr 4-5, s. 419-424Artikel i tidskrift (Refereegranskat)

We study how the recent ATLAS and CMS Higgs mass bounds affect the renormalization group running of the physical parameters in universal extra dimensions. Using the running of the Higgs self-coupling constant, we derive bounds on the cutoff scale of the extra-dimensional theory itself. We show that the running of physical parameters, such as the fermion masses and the CKM mixing matrix, is significantly restricted by these bounds. In particular, we find that the running of the gauge couplings cannot be sufficient to allow gauge unification at the cutoff scale.

• 23. Blennow, Mattias
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik. KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik. KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik.
Signatures from an extra-dimensional seesaw model2010Ingår i: Physical Review D, ISSN 1550-7998, Vol. 82, nr 4, s. 045023-Artikel i tidskrift (Refereegranskat)

We study the generation of small neutrino masses in an extra-dimensional model, where singlet fermions are allowed to propagate in the extra dimension, while the standard model particles are confined to a brane. Motivated by the fact that extra-dimensional models are nonrenormalizable, we truncate the Kaluza-Klein towers at a maximal Kaluza-Klein number. This truncation, together with the structure of the bulk Majorana mass term, motivated by the Sherk-Schwarz mechanism, implies that the Kaluza-Klein modes of the singlet fermions pair to form Dirac fermions, except for a number of unpaired Majorana fermions at the top of each tower. These heavy Majorana fermions are the only sources of lepton number breaking in the model, and similarly to the type-I seesaw mechanism, they naturally generate small masses for the left-handed neutrinos. The lower Kaluza-Klein modes mix with the light neutrinos, and the mixing effects are not suppressed with respect to the light-neutrino masses. Compared to conventional fermionic seesaw models, such mixing can be more significant. We study the signals of this model at the Large Hadron Collider, and find that the current low-energy bounds on the nonunitarity of the leptonic mixing matrix are strong enough to exclude an observation.

• 24.
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik.
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik. KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik.
Non-standard interactions using the OPERA experiment2008Ingår i: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 56, nr 4, s. 529-536Artikel i tidskrift (Refereegranskat)

We investigate the implications of non-standard interactions on neutrino oscillations in the OPERA experiment. In particular, we study the non-standard interaction parameter epsilon(mu tau) . We show that the OPERA experiment has a unique opportunity to reduce the allowed region for this parameter compared with other experiments such as the MINOS experiment, mostly due to the higher neutrino energies in the CNGS beam compared to the NuMI beam. We find that OPERA is mainly sensitive to a combination of standard and non-standard parameters and that a resulting anti-resonance effect could suppress the expected number of events. Furthermore, we show that running OPERA for five years each with neutrinos and anti-neutrinos would help in resolving the degeneracy between the standard parameters and epsilon(mu tau) . This scenario is significantly better than the scenario with a simple doubling of the statistics by running with neutrinos for ten years.

• 25. Blennow, Mattias
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik.
Approximative two-flavor framework for neutrino oscillations with nonstandard interactions2008Ingår i: Physical Review D, ISSN 1550-7998, Vol. 78, nr 9, s. 093002-1-093002-9Artikel i tidskrift (Refereegranskat)

In this paper, we develop approximative two-flavor neutrino oscillation formulas including subleading nonstandard interaction effects. Especially, the limit when the small mass-squared difference approaches zero is investigated. The approximate formulas are also tested against numerical simulations in order to determine their accuracy and they will probably be most useful in the GeV energy region, which is the energy region where most upcoming neutrino oscillation experiments will be operating. Naturally, it is important to have analytical formulas in order to interpret the physics behind the degeneracies between standard and nonstandard parameters.

• 26.
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik.
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik.
Effective neutrino mixing and oscillations in dense matter2005Ingår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 609, nr 3-4, s. 330-338Artikel i tidskrift (Refereegranskat)

We investigate the effective case of two-flavor neutrino oscillations in infinitely dense matter by using a perturbative approach. We begin by briefly summarizing the conditions for the three-flavor neutrino oscillation probabilities to take on the same form as the corresponding two-flavor probabilities. Then, we proceed with the infinitely dense matter calculations. Finally, we study the validity of the approximation of infinitely dense matter when the effective matter potential is large, but not infinite, this is done by using both analytic and numeric methods.

• 27.
KTH, Tidigare Institutioner, Fysik.
KTH, Tidigare Institutioner, Fysik.
Exact series solution to the two flavor neutrino oscillation problem in matter2004Ingår i: Journal of Mathematical Physics, ISSN 0022-2488, E-ISSN 1089-7658, Vol. 45, nr 11, s. 4053-4063Artikel i tidskrift (Refereegranskat)

In this paper, we present a real nonlinear differential equation for the two flavor neutrino oscillation problem in matter with an arbitrary density profile. We also present an exact series solution to this nonlinear differential equation. In addition, we investigate numerically the convergence of this solution for different matter density profiles such as constant and linear profiles as well as the Preliminary Reference Earth Model describing the Earth's matter density profile. Finally, we discuss other methods used for solving the neutrino flavor evolution problem.

• 28.
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik.
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik. KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik.
Effects of non-standard interactions in the MINOS experiment2008Ingår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 660, nr 5, s. 522-528Artikel i tidskrift (Refereegranskat)

We investigate the effects of non-standard interactions on the determination of the neutrino oscillation parameters Delta m(31)(2), theta(23), and theta(13) in the MINOS experiment. We show that adding non-standard interactions to the analysis lead to an extension of the allowed parameter space to larger values of Delta m(31)(2) and smaller theta(23), and basically removes all predictability for theta(13). In addition, we discuss the sensitivities to the non-standard interaction parameters of the MINOS experiment alone. In particular, we examine the degeneracy between theta(13) and the non-standard interaction parameter epsilon(e tau). We find that this degeneracy is responsible for the removal of the theta(13) predictability and that the possible bound on vertical bar epsilon(e tau)vertical bar is competitive with direct bounds only if a more stringent external bound on theta(13) is applied.

• 29.
KTH, Tidigare Institutioner, Fysik.
KTH, Tidigare Institutioner, Fysik. KTH, Tidigare Institutioner, Fysik.
Day-night effect in solar neutrino oscillations with three flavors2004Ingår i: Physical Review D. Particles and fields, ISSN 0556-2821, E-ISSN 1089-4918, Vol. 69, nr 7, s. 073006-1-073006-9Artikel i tidskrift (Refereegranskat)

We investigate the effects of a nonzero leptonic mixing angle theta(13) on the solar neutrino day-night asymmetry. Using a constant matter density profile for the Earth and well-motivated approximations, we derive analytical expressions for the nu(e) survival probabilities for solar neutrinos arriving directly at the detector and for solar neutrinos which have passed through the Earth. Furthermore, we numerically study the effects of a nonzero theta(13) on the day-night asymmetry at detectors and find that they are small. Finally, we show that if the uncertainties in the parameters theta(12) and Deltam(2) as well as the uncertainty in the day-night asymmetry itself were much smaller than they are today, this effect could, in principle, be used to determine theta(13).

• 30.
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik.
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik. KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik.
Solar Neutrino Day-Night Effect2005Ingår i: NEUTRINO 2004 / [ed] Jacques Dumarchez, Thomas Patzak, François Vannucci, Elsevier Science B.V. , 2005, s. 578-578Konferensbidrag (Refereegranskat)

We summarize the results of Ref. [M. Blennow, T. Ohlsson and H. Snellman, Phys. Rev. D 69 (2004) 073006, hep-ph/0311098] in which we determine the effects of three flavor mixing on the day-night asymmetry in the flux of solar neutrinos. Analytic methods are used to determine the difference in the day and night solar electron neutrino survival probabilites and numerical methods are used to determine the effect of three flavor mixing at detectors.

• 31.
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik.
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik. School of Natural Sciences, Institute for Advanced Study, Princeton, United States.
Damping signatures in future neutrino oscillation experiments2005Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, Vol. 2005, nr 06, s. 049-Artikel i tidskrift (Refereegranskat)

We discuss the phenomenology of damping signatures in the neutrino oscillation probabilities, where either the oscillating terms or the probabilities can be damped. This approach is a possibility for tests of damping effects in future neutrino oscillation experiments, where we mainly focus on reactor and long-baseline experiments. We extensively motivate different damping signatures due to small corrections by neutrino decoherence, neutrino decay, oscillations into sterile neutrinos, or other mechanisms, and classify these signatures according to their energy ( spectral) dependencies. We demonstrate, at the example of short baseline reactor experiments, that damping can severely alter the interpretation of results, e. g., it could fake a value of sin(2)(2 theta(13)) smaller than the one provided by Nature. In addition, we demonstrate how a neutrino factory could constrain different damping models with emphasis on how these different models could be distinguished, i.e., how easily the actual type of effect could be identified. We find that the damping models cluster in different categories, which can be much better distinguished from each other than models within the same cluster.

• 32.
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik.
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik. School of Natural Sciences, Institute for Advanced Study, Princeton, United States.
Non-standard Hamiltonian effects on neutrino oscillations2007Ingår i: The European Physical Journal C, ISSN 1434-6044, Vol. 49, nr 4, s. 1023-1039Artikel i tidskrift (Refereegranskat)

We investigate non-standard Hamiltonian effects on neutrino oscillations, which are effective additional contributions to the vacuum or matter Hamiltonian. Since these effects can enter in either the flavor or mass basis, we develop an understanding of the difference between these bases representing the underlying theoretical model. In particular, the simplest of these effects are classified as "pure" flavor or mass effects, where the appearance of such a "pure" effect can be quite plausible as a leading non-standard contribution from theoretical models. Compared to earlier studies investigating particular effects, we aim for a top-down classification of a possible "new physics" signature at future long-baseline neutrino oscillation precision experiments. We develop a general framework for such effects with two neutrino flavors and discuss the extension to three neutrino flavors, and we demonstrate the challenges for a neutrino factory to distinguish the theoretical origin of these effects with a numerical example as well. We find how the precision measurements of neutrino oscillation parameters can be altered by non-standard effects alone (not including non-standard interactions in the creation and detection processes) and that the non-standard effects on Hamiltonian level can be distinguished from other non-standard effects (such as neutrino decoherence and decay) if we consider the specific imprint of the effects on the energy spectra of several different oscillation channels at a neutrino factory.

• 33.
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik.
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik. KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik. KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik.
Monoenergetic gamma rays from nonminimal Kaluza-Klein dark matter annihilations2012Ingår i: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 85, nr 4, s. 043524-Artikel i tidskrift (Refereegranskat)

We investigate monoenergetic gamma-ray signatures from annihilations of dark matter comprised of Z(1), the first Kaluza-Klein (KK) excitation of the Z boson in a nonminimal universal extra dimensions (UED) model. The self interactions of the non-Abelian Z(1) gauge boson give rise to a large number of contributing Feynman diagrams that do not exist for annihilations of the Abelian gauge boson B-1, which is the standard Kaluza-Klein dark matter (KKDM) candidate. We find that the annihilation rate is indeed considerably larger for the Z(1) than for the B-1. Even though relic density calculations indicate that the mass of the Z(1) should be larger than the mass of the B-1, the predicted monoenergetic gamma fluxes are of the same order of magnitude. We compare our results to existing experimental limits, as well as to future sensitivities, for image air Cherenkov telescopes, and we find that the limits are reached already with a moderately large boost factor. The realistic prospects for detection depend on the experimental energy resolution.

• 34.
KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik. AlbaNova Univ Ctr, Oskar Klein Ctr Cosmoparticle Phys, Roslagstullsbacken 21, SE-10691 Stockholm, Sweden.
KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik. AlbaNova Univ Ctr, Oskar Klein Ctr Cosmoparticle Phys, Roslagstullsbacken 21, SE-10691 Stockholm, Sweden. KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik. AlbaNova Univ Ctr, Oskar Klein Ctr Cosmoparticle Phys, Roslagstullsbacken 21, SE-10691 Stockholm, Sweden;Univ Iceland, Sci Inst, Dunhaga 3, IS-107 Reykjavik, Iceland. AlbaNova Univ Ctr, Oskar Klein Ctr Cosmoparticle Phys, Roslagstullsbacken 21, SE-10691 Stockholm, Sweden.;Stockholm Univ, AlbaNova Univ Ctr, Dept Phys, Roslagstullsbacken 21, SE-10691 Stockholm, Sweden.;NORDITA, AlbaNova Univ Ctr, Roslagstullsbacken 23, SE-10691 Stockholm, Sweden.
Novel constraints on mixed dark-matter scenarios of primordial black holes and WIMPs2018Ingår i: Journal of Cosmology and Astroparticle Physics, ISSN 1475-7516, E-ISSN 1475-7516, nr 7, artikel-id 003Artikel i tidskrift (Refereegranskat)

We derive constraints on mixed dark-matter scenarios consisting of primordial black holes (PBHs) and weakly interacting massive particles (WIMPs). In these scenarios, we expect a density spike of the WIMPs that are gravitationally bound to the PBHs, which results in an enhanced annihilation rate and increased indirect detection prospects. We show that such scenarios provide strong constraints on the allowed fraction of PBHs that constitutes the dark matter, depending on the WIMP mass m(x) and the velocity-averaged annihilation cross-section <sigma v >. For the standard scenario with m(x) = 100 GeV and <sigma v > = 3 x 10(-26) cm(3)/s, we derive bounds that are stronger than all existing bounds for PBHs with masses 10(-12) M-circle dot less than or similar to M-BH less than or similar to 10(4) where M-circle dot, is the solar mass, and mostly so by several orders of magnitude.

• 35.
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik. Harish-Chandra Research Institute, Chhatnag Road, Jhunsi, Allahabad, India.
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik.
Neutrino physics with non-standard interactions at INO2015Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, Vol. 2015, nr 12, s. 1-22Artikel i tidskrift (Refereegranskat)

Abstract: Non-standard neutrino interactions (NSI) involved in neutrino propagation inside Earth matter could potentially alter atmospheric neutrino fluxes. In this work, we look at the impact of these NSI on the signal at the ICAL detector to be built at the India-based Neutrino Observatory (INO). We show how the sensitivity to the neutrino mass hierarchy of ICAL changes in the presence of NSI. The mass hierarchy sensitivity is shown to be rather sensitive to the NSI parameters ϵeμ and ϵeτ , while the dependence on ϵμτ and ϵτ τ is seen to be very mild, once the χ2 is marginalised over oscillation and NSI parameters. If the NSI are large enough, the event spectrum at ICAL is expected to be altered and this can be used to discover new physics. We calculate the lower limit on NSI parameters above which ICAL could discover NSI at a given C.L. from 10 years of data. If NSI were too small, the null signal at ICAL can constrain the NSI parameters. We give upper limits on the NSI parameters at any given C.L. that one is expected to put from 10 years of running of ICAL. Finally, we give C.L. contours in the NSI parameter space that is expected to be still allowed from 10 years of running of the experiment.

• 36.
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik. Harish-Chandra Research Institute, India .
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik.
Bounds on non-standard neutrino interactions using PINGU2014Ingår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 739, s. 357-364Artikel i tidskrift (Refereegranskat)

We investigate the impact of non-standard neutrino interactions (NSIs) on atmospheric neutrinos using the proposed PINGU experiment. In particular, we focus on the matter NSI parameters epsilon(mu tau) and vertical bar epsilon(tau tau)-epsilon(mu mu)vertical bar that have previously been constrained by the Super-Kamiokande experiment. First, we present approximate analytical formulas for the difference of the muon neutrino survival probability with and without the above-mentioned NSI parameters. Second, we calculate the atmospheric neutrino events at PINGU in the energy range (2-100) GeV, which follow the trend outlined on probability level. Finally, we perform a statistical analysis of PINGU. Using three years of data, we obtain bounds from PINGU given by -0.0043 (-0.0048) < epsilon(mu tau) < 0.0047 (0.0046) and -0.03 (-0.016) < epsilon(tau tau) < 0.017 (0.032) at 90% confidence level for normal (inverted) neutrino mass hierarchy, which improve the Super-Kamiokande bounds by one order of magnitude. In addition, we show the expected allowed contour region in the epsilon-ettplane if NSIs exist in Nature and the result suggests that there is basically no correlation between epsilon(mu tau) and epsilon(tau tau).

• 37.
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik.
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik. KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik.
Establishing analogies between the physics of extra dimensions and carbon nanotubes2012Ingår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 714, nr 1, s. 44-47Artikel i tidskrift (Refereegranskat)

We point out a conceptual analogy between the physics of extra spatial dimensions and the physics of carbon nanotubes which arises for principle reasons, although the corresponding energy scales are at least ten orders of magnitude apart. For low energies, one can apply the Kaluza-Klein description to both types of systems, leading to two completely different but consistent interpretations of the underlying physics. In particular, we discuss in detail the Kaluza-Klein description of armchair and zig-zag carbon nanotubes. Furthermore, we describe how certain experimental results for carbon nanotubes could be re-interpreted in terms of the Kaluza-Klein description. Finally, we present ideas for new measurements that could allow to probe concepts of models with extra spatial dimensions in table-top experiments, providing further links between condensed matter and particle physics.

• 38. Edgecock, T. R.
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik. KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik.
High intensity neutrino oscillation facilities in Europe2013Ingår i: Physical Review Special Topics. Accelerators and Beams, ISSN 1098-4402, E-ISSN 1098-4402, Vol. 16, nr 2, s. 021002-Artikel i tidskrift (Refereegranskat)

The EUROnu project has studied three possible options for future, high intensity neutrino oscillation facilities in Europe. The first is a Super Beam, in which the neutrinos come from the decay of pions created by bombarding targets with a 4 MW proton beam from the CERN High Power Superconducting Proton Linac. The far detector for this facility is the 500 kt MEMPHYS water Cherenkov, located in the Frejus tunnel. The second facility is the Neutrino Factory, in which the neutrinos come from the decay of mu(+) and mu(-) beams in a storage ring. The far detector in this case is a 100 kt magnetized iron neutrino detector at a baseline of 2000 km. The third option is a Beta Beam, in which the neutrinos come from the decay of beta emitting isotopes, in particular He-6 and Ne-18, also stored in a ring. The far detector is also the MEMPHYS detector in the Frejus tunnel. EUROnu has undertaken conceptual designs of these facilities and studied the performance of the detectors. Based on this, it has determined the physics reach of each facility, in particular for the measurement of CP violation in the lepton sector, and estimated the cost of construction. These have demonstrated that the best facility to build is the Neutrino Factory. However, if a powerful proton driver is constructed for another purpose or if the MEMPHYS detector is built for astroparticle physics, the Super Beam also becomes very attractive.

• 39. Freund, Martin
KTH, Tidigare Institutioner, Fysik.
Matter enhanced neutrino oscillations with a realistic earth density profile2000Ingår i: Modern Physics Letters A, ISSN 0217-7323, E-ISSN 1793-6632, Vol. 15, nr 13, s. 867-874Artikel i tidskrift (Refereegranskat)

We have investigated matter enhanced neutrino oscillations with a mantle-core-mantle step function and a realistic Earth matter density profile in both a two- and a three-neutrino scenario. We found that the realistic Earth matter density profile can be well approximated with the mantle-core-mantle step function and that there could be an influence on the oscillation channel nu(mu) --> nu(tau) due to resonant enhancement of one of the mixing angles.

• 40. Girardi, Ivan
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik. KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik.
Constraining sterile neutrinos using reactor neutrino experiments2014Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 8Artikel i tidskrift (Refereegranskat)

Models of neutrino mixing involving one or more sterile neutrinos have resurrected their importance in the light of recent cosmological data. In this case, reactor antineutrino experiments offer an ideal place to look for signatures of sterile neutrinos due to their impact on neutrino flavor transitions. In this work, we show that the high-precision data of the Daya Bay experiment constrain the 3+1 neutrino scenario imposing upper bounds on the relevant active-sterile mixing angle sin(2) 2 theta(14) less than or similar to 0.06 at 3 sigma confidence level for the mass-squared difference Delta m(41)(2) in the range (10(-3), 10(-1)) eV(2). The latter bound can be improved by six years of running of the JUNO experiment, sin(2) 2 theta(14) less than or similar to 0.016, although in the smaller mass range Delta m(41)(2) is an element of(10(-4), 10(-3)) eV(2). We have also investigated the impact of sterile neutrinos on precision measurements of the standard neutrino oscillation parameters theta(13) and Delta m(31)(2) (at Daya Bay and JUNO), theta(12) and Delta m(21)(2) (at JUNO), and most importantly, the neutrino mass hierarchy (at JUNO). We find that, except for the obvious situation where Delta m(41)(2) similar to Delta m(31)(2), sterile states do not affect these measurements substantially.

• 41. Hagedorn, Claudia
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik. KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik.
Unification of gauge couplings in radiative neutrino mass models2016Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 9, artikel-id 111Artikel i tidskrift (Refereegranskat)

We investigate the possibility of gauge coupling uni fi cation in various radiative neutrino mass models, which generate neutrino masses at one-and/or two-loop level. Renormalization group running of gauge couplings is performed analytically and numerically at one-and two-loop order, respectively. We study three representative classes of radiative neutrino mass models: (I) minimal ultraviolet completions of the dimension-7 Delta L = 2 operators which generate neutrino masses at one-and/or two-loop level without and with dark matter candidates, (II) models with dark matter which lead to neutrino masses at one-loop level and (III) models with particles in the adjoint representation of SU(3). In class (I), gauge couplings unify in a few models and adding dark matter amplifies the chances for uni fi cation. In class (II), about a quarter of the models admits gauge coupling uni fi cation. In class (III), none of the models leads to gauge coupling uni fi cation. Regarding the scale of uni fi cation, we find values between 10(14) GeV and 10(16) GeV for models belonging to class (I) without dark matter, whereas models in class (I) with dark matter as well as models of class (II) prefer values in the range 5.10(10) - 5.10(14) GeV.

• 42.
KTH, Skolan för teknikvetenskap (SCI), Fysik.
KTH, Skolan för teknikvetenskap (SCI), Fysik, Teoretisk partikelfysik. KTH, Skolan för teknikvetenskap (SCI), Fysik. KTH, Skolan för teknikvetenskap (SCI), Fysik.
Full parameter scan of the Zee model: exploring Higgs lepton flavor violation2017Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 4, artikel-id 130Artikel i tidskrift (Refereegranskat)

We study the general Zee model, which includes an extra Higgs scalar doublet and a new singly-charged scalar singlet. Neutrino masses are generated at one-loop level, and in order to describe leptonic mixing, both the Standard Model and the extra Higgs scalar doublets need to couple to leptons (in a type-III two-Higgs doublet model), which necessarily generates large lepton flavor violating signals, also in Higgs decays. Imposing all relevant phenomenological constraints and performing a full numerical scan of the parameter space, we find that both normal and inverted neutrino mass orderings can be fitted, although the latter is disfavored with respect to the former. In fact, inverted ordering can only be accommodated if theta(23) turns out to be in the first octant. A branching ratio for h -> tau mu of up to 10(-2) is allowed, but it could be as low as 10(-6). In addition, if future expected sensitivities of tau -> mu gamma are achieved, normal ordering can be almost completely tested. Also, mu e conversion is expected to probe large parts of the parameter space, excluding completely inverted ordering if no signal is observed. Furthermore, non-standard neutrino interactions are found to be smaller than 10(-6), which is well below future experimental sensitivity. Finally, the results of our scan indicate that the masses of the additional scalars have to be below 2.5 TeV, and typically they are lower than that and therefore within the reach of the LHC and future colliders.

• 43.
Chinese Acad Sci, Inst High Energy Phys, Beijing 100049, Peoples R China.;Univ Chinese Acad Sci, Sch Phys Sci, Beijing 100049, Peoples R China..
KTH, Skolan för teknikvetenskap (SCI), Fysik, Teoretisk partikelfysik. Univ Iceland, Sci Inst, Dunhaga 3, IS-107 Reykjavik, Iceland.. Chinese Acad Sci, Inst High Energy Phys, Beijing 100049, Peoples R China.;Univ Chinese Acad Sci, Sch Phys Sci, Beijing 100049, Peoples R China.;Peking Univ, Ctr High Energy Phys, Beijing 100871, Peoples R China..
Observational constraints on secret neutrino interactions from big bang nucleosynthesis2018Ingår i: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 97, nr 7, artikel-id 075009Artikel i tidskrift (Refereegranskat)

We investigate possible interactions between neutrinos and massive scalar bosons via g(phi)(nu) over bar nu phi (or massive vector bosons via g(V)(nu) over bar gamma(mu)nu V-mu) and explore the allowed parameter space of the coupling constant g phi (or g(V)) and the scalar (or vector) boson mass m(phi) (or m(V)) by requiring that these secret neutrino interactions (SNIs) should not spoil the success of big bang nucleosynthesis (BBN). Incorporating the SNIs into the evolution of the early Universe in the BBN era, we numerically solve the Boltzmann equations and compare the predictions for the abundances of light elements with observations. It turns out that the constraint on g(phi) and m(phi) in the scalar-boson case is rather weak, due to a small number of degrees of freedom (d.o.f.). However, in the vector-boson case, the most stringent bound on the coupling g(V) less than or similar to 6 x 10(-10) at 95% confidence level is obtained for m(V) similar or equal to 1 MeV, while the bound becomes much weaker g(V) less than or similar to 8 x 10(-6) for smaller masses m(V) less than or similar to 10(-4) MeV. Moreover, we discuss in some detail how the SNIs affect the cosmological evolution and the abundances of the lightest elements.

• 44.
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik.
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik. KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik.
Triplet leptogenesis in left-right symmetric seesaw models2008Ingår i: Journal of Cosmology and Astroparticle Physics, ISSN 1475-7516, E-ISSN 1475-7516, Vol. 2008, nr 01, s. 014-Artikel i tidskrift (Refereegranskat)

We discuss scalar triplet leptogenesis in a specific left-right symmetric seesaw model. We show that the Majorana phases that are present in the model can be effectively used to saturate the existing upper limit on the CP-asymmetry of the triplets. We solve the relevant Boltzmann equations and analyze the viability of triplet leptogenesis. It is known for this kind of scenario that the efficiency of leptogenesis is maximal if there exists a hierarchy between the branching ratios of the triplet decays into leptons and Higgs particles. We show that triplet leptogenesis typically favors branching ratios with not too strong hierarchies, since maximal efficiency can only be obtained at the expense of suppressed CP-asymmetries.

• 45.
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik.
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik.
Indirect detection of Kaluza-Klein dark matter from latticized universal dimensions2006Ingår i: Journal of Cosmology and Astroparticle Physics, ISSN 1475-7516, E-ISSN 1475-7516, Vol. 2006, nr 06, s. 014-Artikel i tidskrift (Refereegranskat)

We consider Kaluza-Klein dark matter from latticized universal dimensions. We investigate two different lattice models, where the models differ in the choice of boundary conditions. The models reproduce relevant features of the continuum model for Kaluza-Klein dark matter. For the model with simple boundary conditions, this is the case even for a model with only a few lattice sites. We study the effects of the latticization on the differential flux of positrons from annihilation of Kaluza-Klein dark matter in the galactic halo. We find that for different choices of the compactification radius, the differential positron flux rapidly converges to the continuum model results as a function of the number of lattice sites. In addition, we consider the prospects for upcoming space-based experiments such as PAMELA and AMS-02 to probe the latticization effect.

• 46.
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Matematisk fysik.
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Teoretisk partikelfysik. Department of Physics, Oklahoma State University.
Neutrino oscillations in deconstructed dimensions2005Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, Vol. 2005, nr 02, s. 049-Artikel i tidskrift (Refereegranskat)

We present a model for neutrino oscillations in the presence of a deconstructed non-gravitational large extra dimension compactified on the boundary of a two-dimensional disk. In the deconstructed phase, sub-mm lattice spacings are generated from the hierarchy of energy scales between similar to 1 TeV and the usual B - L breaking scale similar to 10(15) GeV. Here, short-distance cutoffs down to similar to 1eV are motivated by the strong coupling behavior of gravity in local discrete extra dimensions. This could make it possible to probe the discretization of extra dimensions and non-trivial field configurations in theory spaces which have only a few sites, i.e., for coarse latticizations. Thus, the model has relevance to present and future precision neutrino oscillation experiments.

• 47. Jacobson, Magnus
KTH, Tidigare Institutioner, Fysik.
Extrinsic CPT violation in neutrino oscillations in matter2004Ingår i: Physical Review D. Particles and fields, ISSN 0556-2821, E-ISSN 1089-4918, Vol. 69, nr 1, s. 013003-Artikel i tidskrift (Refereegranskat)

We investigate matter-induced (or extrinsic) CPT violation effects in neutrino oscillations in matter. Especially, we present approximate analytical formulas for the CPT-violating probability differences for three flavor neutrino oscillations in matter with an arbitrary matter density profile. Note that we assume that the CPT invariance theorem holds, which means that the CPT violation effects arise entirely because of the presence of matter. As special cases of matter density profiles, we consider constant and step-function matter density profiles, which are relevant for neutrino oscillation physics in accelerator and reactor long baseline experiments as well as neutrino factories. Finally, the implications of extrinsic CPT violation on neutrino oscillations in matter for several past, present, and future long baseline experiments are estimated.

• 48. Jacobsson, Björn
KTH, Tidigare Institutioner, Fysik. KTH, Tidigare Institutioner, Fysik.
Effects of random matter density fluctuations on the neutrino oscillation transition probabilities in the Earth2002Ingår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 532, nr 04-mar, s. 259-266Artikel i tidskrift (Refereegranskat)

In this Letter, we investigate the effects of random fluctuations of the Earth matter density for long baselines on the neutrino oscillation transition probabilities. We especially identify relevant parameters characterizing the matter density noise and calculate their effects by averaging over statistical ensembles of a large number of matter density profiles. For energies and baselines appropriate to neutrino factories, absolute errors on the relevant appearance probabilities are at the level of \DeltaP(alphabeta)\ similar to 10(-4) (with perhaps \P-mue similar to 1% for neutrinos), whereby a modest improvement in understanding of the geophysical data should render such effects unimportant.

• 49.
KTH, Tidigare Institutioner, Fysik.
KTH, Tidigare Institutioner, Fysik. KTH, Tidigare Institutioner, Fysik.
The effects of matter density uncertainties on neutrino oscillations in the Earth2003Ingår i: Journal of Physics G: Nuclear and Particle Physics, ISSN 0954-3899, E-ISSN 1361-6471, Vol. 29, nr 8, s. 1873-1875Artikel i tidskrift (Refereegranskat)

We compare three different methods of evaluating uncertainties in the Earth's matter density profile, which are relevant to long baseline experiments, such as neutrino factories.

• 50.
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik.
KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik.
The effective matter potential for highly relativistic neutrinos2006Ingår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 634, nr 03-feb, s. 267-271Artikel i tidskrift (Refereegranskat)

We investigate matter effects on highly relativistic neutrinos. The self-energy of neutrinos is determined in an electron or neutrino background taking into account resonance and finite width effects of the gauge bosons. We find minor changes compared to the formerly used formula for the propagator function and large deviations of the effective width from the decay width of the gauge bosons considering higher moments of the electron or neutrino distribution function.

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