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Publications (10 of 128) Show all publications
Boucenna, S. M., Kühnel, F., Ohlsson, T. & Visinelli, L. (2018). Novel constraints on mixed dark-matter scenarios of primordial black holes and WIMPs. Journal of Cosmology and Astroparticle Physics (7), Article ID 003.
Open this publication in new window or tab >>Novel constraints on mixed dark-matter scenarios of primordial black holes and WIMPs
2018 (English)In: Journal of Cosmology and Astroparticle Physics, ISSN 1475-7516, E-ISSN 1475-7516, no 7, article id 003Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
IOP PUBLISHING LTD, 2018
Keywords
dark matter theory, primordial black holes
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-232405 (URN)10.1088/1475-7516/2018/07/003 (DOI)000437299100003 ()2-s2.0-85051711141 (Scopus ID)
Note

QC 20180726

Available from: 2018-07-26 Created: 2018-07-26 Last updated: 2018-10-16Bibliographically approved
Huang, G.-y., Ohlsson, T. & Zhou, S. (2018). Observational constraints on secret neutrino interactions from big bang nucleosynthesis. Physical Review D: covering particles, fields, gravitation, and cosmology, 97(7), Article ID 075009.
Open this publication in new window or tab >>Observational constraints on secret neutrino interactions from big bang nucleosynthesis
2018 (English)In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 97, no 7, article id 075009Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
American Physical Society, 2018
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-228129 (URN)10.1103/PhysRevD.97.075009 (DOI)000429221900001 ()2-s2.0-85046723245 (Scopus ID)
Note

QC 20180518

Available from: 2018-05-18 Created: 2018-05-18 Last updated: 2018-10-31Bibliographically approved
Herrero-Garcia, J., Ohlsson, T., Riad, S. & Wirén, J. (2017). Full parameter scan of the Zee model: exploring Higgs lepton flavor violation. Journal of High Energy Physics (JHEP) (4), Article ID 130.
Open this publication in new window or tab >>Full parameter scan of the Zee model: exploring Higgs lepton flavor violation
2017 (English)In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 4, article id 130Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
Springer, 2017
Keywords
Neutrino Physics, Beyond Standard Model, Higgs Physics
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-207676 (URN)10.1007/JHEP04(2017)130 (DOI)000400007000001 ()2-s2.0-85018567259 (Scopus ID)
Note

QC 20170601

Available from: 2017-06-01 Created: 2017-06-01 Last updated: 2017-11-10Bibliographically approved
Meloni, D., Ohlsson, T. & Riad, S. (2017). Renormalization group running of fermion observables in an extended non-supersymmetric SO(10) model. Journal of High Energy Physics (JHEP) (3), Article ID 045.
Open this publication in new window or tab >>Renormalization group running of fermion observables in an extended non-supersymmetric SO(10) model
2017 (English)In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 3, article id 045Article in journal (Refereed) Published
Abstract [en]

We investigate the renormalization group evolution of fermion masses, mixings and quartic scalar Higgs self-couplings in an extended non-supersymmetric SO(10) model, where the Higgs sector contains the 10(H), 120(H), and 126(H) representations. The group SO(10) is spontaneously broken at the GUT scale to the Pati-Salam group and subsequently to the Standard Model (SM) at an intermediate scale MI. We explicitly take into account the effects of the change of gauge groups in the evolution. In particular, we derive the renormalization group equations for the different Yukawa couplings. We find that the computed physical fermion observables can be successfully matched to the experimental measured values at the electroweak scale. Using the same Yukawa couplings at the GUT scale, the measured values of the fermion observables cannot be reproduced with a SM-like evolution, leading to differences in the numerical values up to around 80%. Furthermore, a similar evolution can be performed for a minimal SO(10) model, where the Higgs sector consists of the 10(H) and 126(H) representations only, showing an equally good potential to describe the low-energy fermion observables. Finally, for both the extended and the minimal SO(10) models, we present predictions for the three Dirac and Majorana CP-violating phases as well as three effective neutrino mass parameters.

Place, publisher, year, edition, pages
Springer, 2017
Keywords
Beyond Standard Model, GUT, Neutrino Physics
National Category
Other Physics Topics
Identifiers
urn:nbn:se:kth:diva-205465 (URN)10.1007/JHEP03(2017)045 (DOI)000397672700005 ()2-s2.0-85014946783 (Scopus ID)
Note

QC 20170522

Available from: 2017-05-22 Created: 2017-05-22 Last updated: 2017-11-13Bibliographically approved
Kuhnel, F. & Ohlsson, T. (2017). Signatures of compact halos of sterile-neutrino dark matter. Physical Review D: covering particles, fields, gravitation, and cosmology, 96(10), Article ID 103020.
Open this publication in new window or tab >>Signatures of compact halos of sterile-neutrino dark matter
2017 (English)In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 96, no 10, article id 103020Article in journal (Refereed) Published
Abstract [en]

We investigate compact halos of sterile-neutrino dark matter and examine observable signatures with respect to neutrino and photon emission. Primarily, we consider two cases: primordial black-hole halos and ultracompact minihalos. In both cases, we find that there exists a broad range of possible parameter choices such that detection in the near future with x-ray and gamma-ray telescopes might be well possible. In fact, for energies above 10 TeV, the neutrino telescope IceCube would be a splendid detection machine for such macroscopic dark-matter candidates.

Place, publisher, year, edition, pages
American Physical Society, 2017
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-220271 (URN)10.1103/PhysRevD.96.103020 (DOI)000416315600003 ()2-s2.0-85037061947 (Scopus ID)
Funder
Swedish Research Council, 638-2013-8993
Note

QC 20180110

Available from: 2018-01-10 Created: 2018-01-10 Last updated: 2018-01-10Bibliographically approved
Ohlsson, T. (2016). Non-Hermitian neutrino oscillations in matter with PT symmetric Hamiltonians. Europhysics letters, 113(6), Article ID 61001.
Open this publication in new window or tab >>Non-Hermitian neutrino oscillations in matter with PT symmetric Hamiltonians
2016 (English)In: Europhysics letters, ISSN 0295-5075, E-ISSN 1286-4854, Vol. 113, no 6, article id 61001Article in journal (Refereed) Published
Abstract [en]

We introduce and develop a novel approach to extend the ordinary two-flavor neutrino oscillation formalism in matter using a non-Hermitian PT symmetric effective Hamiltonian. The condition of PT symmetry is weaker and less mathematical than that of hermicity, but more physical, and such an extension of the formalism can give rise to sub-leading effects in neutrino flavor transitions similar to the effects by so-called non-standard neutrino interactions. We derive the necessary conditions for the spectrum of the effective Hamiltonian to be real as well as the mappings between the fundamental and effective parameters. We find that the real spectrum of the effective Hamiltonian will depend on all new fundamental parameters introduced in the non-Hermitian PT symmetric extension of the usual neutrino oscillation formalism and that either i) the spectrum is exact and the effective leptonic mixing must always be maximal or ii) the spectrum is approximate and all new fundamental parameters must be small.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2016
National Category
Other Physics Topics
Identifiers
urn:nbn:se:kth:diva-187277 (URN)10.1209/0295-5075/113/61001 (DOI)2-s2.0-84963847170 (Scopus ID)
Note

QC 20160519

Available from: 2016-05-19 Created: 2016-05-19 Last updated: 2017-11-30Bibliographically approved
Wildner, E., Baussan, E., Blennow, M., Bogomilov, M., Burgman, A., Bouquerel, E., . . . Vassilopoulos, N. (2016). The Opportunity Offered by the ESSnuSB Project to Exploit the Larger Leptonic CP Violation Signal at the Second Oscillation Maximum and the Requirements of This Project on the ESS Accelerator Complex. Advances in High Energy Physics, Article ID 8640493.
Open this publication in new window or tab >>The Opportunity Offered by the ESSnuSB Project to Exploit the Larger Leptonic CP Violation Signal at the Second Oscillation Maximum and the Requirements of This Project on the ESS Accelerator Complex
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2016 (English)In: Advances in High Energy Physics, ISSN 1687-7357, E-ISSN 1687-7365, article id 8640493Article in journal (Refereed) Published
Abstract [en]

The European Spallation Source (ESS), currently under construction in Lund, Sweden, is a research center that will provide, by 2023, the world's most powerful neutron source. The average power of the proton linac will be 5 MW. Pulsing this linac at higher frequency will make it possible to raise the average total beam power to 10 MW to produce, in parallel with the spallation neutron production, a very intense neutrino Super Beam of about 0.4 GeV mean neutrino energy. This will allow searching for leptonic CP violation at the second oscillation maximum where the sensitivity is about 3 times higher than at the first. The ESS neutrino Super Beam, ESSnuSB operated with a 2.0 GeV linac proton beam, together with a large undergroundWater Cherenkov detector located at 540 km from Lund, will make it possible to discover leptonic CP violation at 5 sigma. significance level in 56% (65% for an upgrade to 2.5 GeV beam energy) of the leptonic CP-violating phase range after 10 years of data taking, assuming a 5% systematic error in the neutrino flux and 10% in the neutrino cross section. The paper presents the outstanding physics reach possible for CP violation with ESSnuSB obtainable under these assumptions for the systematic errors. It also describes the upgrade of the ESS accelerator complex required for ESSnuSB.

Place, publisher, year, edition, pages
Hindawi Publishing Corporation, 2016
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-198997 (URN)10.1155/2016/8640493 (DOI)000387385000001 ()2-s2.0-84994652587 (Scopus ID)
Note

QC 20170116

Available from: 2017-01-16 Created: 2016-12-22 Last updated: 2017-11-29Bibliographically approved
Blennow, M., Choubey, S., Ohlsson, T. & Raut, S. K. (2015). Exploring source and detector non-standard neutrino interactions at ESS nu SB. Journal of High Energy Physics (JHEP) (9), Article ID 096.
Open this publication in new window or tab >>Exploring source and detector non-standard neutrino interactions at ESS nu SB
2015 (English)In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 9, article id 096Article in journal (Refereed) Published
Abstract [en]

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.

Keywords
Beyond Standard Model, Neutrino Physics
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-177422 (URN)10.1007/JHEP09(2015)096 (DOI)000363539300002 ()2-s2.0-84942519481 (Scopus ID)
Note

QC 20151124

Available from: 2015-11-24 Created: 2015-11-20 Last updated: 2017-12-01Bibliographically approved
Ohlsson, T. & Zhou, S. (2015). Extrinsic and intrinsic CPT asymmetries in neutrino oscillations. Nuclear Physics B, 893, 482-500
Open this publication in new window or tab >>Extrinsic and intrinsic CPT asymmetries in neutrino oscillations
2015 (English)In: Nuclear Physics B, ISSN 0550-3213, E-ISSN 1873-1562, Vol. 893, p. 482-500Article in journal (Refereed) Published
Abstract [en]

We reconsider the extrinsic and possible intrinsic CPT violation in neutrino oscillations, and point out an identity, i.e., A(alpha beta)(CP) = A(beta alpha)(CPT) + A(alpha beta)(T), among the CP, T, and CPT asymmetries in oscillations. For three-flavor oscillations in matter of constant density, the extrinsic CPT asymmetries A(ee)(CPT), A(e mu)(CPT), A(mu e)(CPT), and A(mu mu)(CPT) caused by Earth matter effects have been calculated in the plane of different neutrino energies and baseline lengths. It is found that two analytical conditions can be implemented to describe the main structure of the contours of vanishing extrinsic CPT asymmetries. Finally, without assuming intrinsic CPT symmetry in the neutrino sector, we investigate the possibility to constrain the difference of the neutrino CF-violating phase and the antineutrino one (delta) over bar using a low-energy neutrino factory and the super-beam experiment ESS nu SB. We find that \delta - (delta) over bar\ less than or similar to 0.35 pi in the former case and \delta - (delta) over bar\ less than or similar to 0.7 pi in the latter case can be achieved at the 3 sigma confidence level if delta = (delta) over bar = pi/2 is assumed.

National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-166500 (URN)10.1016/j.nuclphysb.2015.02.015 (DOI)000352045000022 ()2-s2.0-84923359840 (Scopus ID)
Funder
Swedish Research Council
Note

QC 20150518

Available from: 2015-05-18 Created: 2015-05-11 Last updated: 2017-12-04Bibliographically approved
Choubey, S., Ghosh, A., Ohlsson, T. & Tiwari, D. (2015). Neutrino physics with non-standard interactions at INO. Journal of High Energy Physics (JHEP), 2015(12), 1-22
Open this publication in new window or tab >>Neutrino physics with non-standard interactions at INO
2015 (English)In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, Vol. 2015, no 12, p. 1-22Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
Springer, 2015
Keywords
Neutrino Physics, Solar and Atmospheric Neutrinos
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-181848 (URN)10.1007/JHEP12(2015)126 (DOI)2-s2.0-84951871859 (Scopus ID)
Note

QC 20160209

Available from: 2016-02-09 Created: 2016-02-05 Last updated: 2017-11-30Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0002-3525-8349

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