kth.sePublications
Change search
Link to record
Permanent link

Direct link
Ohlsson, Tommy, ProfessorORCID iD iconorcid.org/0000-0002-3525-8349
Alternative names
Publications (10 of 156) Show all publications
Abele, H., Blennow, M., Ohlsson, T. & Zou, Y. (2023). Particle physics at the European Spallation Source. Physics reports, 1023, 1-84
Open this publication in new window or tab >>Particle physics at the European Spallation Source
2023 (English)In: Physics reports, ISSN 0370-1573, E-ISSN 1873-6270, Vol. 1023, p. 1-84Article, review/survey (Refereed) Published
Abstract [en]

Presently under construction in Lund, Sweden, the European Spallation Source (ESS) will be the world's brightest neutron source. As such, it has the potential for a particle physics program with a unique reach and which is complementary to that available at other facilities. This paper describes proposed particle physics activities for the ESS. These encompass the exploitation of both the neutrons and neutrinos produced at the ESS for high precision (sensitivity) measurements (searches).

Place, publisher, year, edition, pages
Elsevier BV, 2023
Keywords
ESS, ESSnuSB, nEDM, Neutrons, NNBAR
National Category
Accelerator Physics and Instrumentation Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-334924 (URN)10.1016/j.physrep.2023.06.001 (DOI)001063474900001 ()2-s2.0-85166173118 (Scopus ID)
Note

QC 20230830

Available from: 2023-08-30 Created: 2023-08-30 Last updated: 2023-10-17Bibliographically approved
Ohlsson, T. (2023). Proton decay. Nuclear Physics B, 993, Article ID 116268.
Open this publication in new window or tab >>Proton decay
2023 (English)In: Nuclear Physics B, ISSN 0550-3213, E-ISSN 1873-1562, Vol. 993, article id 116268Article, review/survey (Refereed) Published
Abstract [en]

Proton decay is a hypothetical form of particle decay in which protons are assumed to decay into lighter particles. This form of decay has yet to be detected. In this contribution to the proceedings of Neutrino 2022, we review the current status of proton decay, covering both experimental results and theoretical models, including their predictions.

Place, publisher, year, edition, pages
Elsevier BV, 2023
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-333974 (URN)10.1016/j.nuclphysb.2023.116268 (DOI)001055396900001 ()2-s2.0-85162836778 (Scopus ID)
Note

QC 20230815

Available from: 2023-08-15 Created: 2023-08-15 Last updated: 2023-09-21Bibliographically approved
Alekou, A., Blennow, M., Choubey, S., Ohlsson, T., Zou, Y. & et al., . (2023). The ESSnuSB Design Study: Overview and Future Prospects. Universe, 9(8), Article ID 347.
Open this publication in new window or tab >>The ESSnuSB Design Study: Overview and Future Prospects
Show others...
2023 (English)In: Universe, E-ISSN 2218-1997, Vol. 9, no 8, article id 347Article, review/survey (Refereed) Published
Abstract [en]

ESSnuSB is a design study for an experiment to measure the CP violation in the leptonic sector at the second neutrino oscillation maximum using a neutrino beam driven by the uniquely powerful ESS linear accelerator. The reduced impact of systematic errors on sensitivity at the second maximum allows for a very precise measurement of the CP violating parameter. This review describes the fundamental advantages of measurement at the second maximum, the necessary upgrades to the ESS linac in order to produce a neutrino beam, the near and far detector complexes, and the expected physics reach of the proposed ESSnuSB experiment, concluding with the near future developments aimed at the project realization.

Place, publisher, year, edition, pages
MDPI AG, 2023
Keywords
CP violation, long baseline, neutrino, oscillation, precision, second maximum
National Category
Subatomic Physics Accelerator Physics and Instrumentation
Identifiers
urn:nbn:se:kth:diva-336790 (URN)10.3390/universe9080347 (DOI)001057758900001 ()2-s2.0-85169097154 (Scopus ID)
Note

QC 20230920

Available from: 2023-09-20 Created: 2023-09-20 Last updated: 2023-09-22Bibliographically approved
Lindestam, M., Ohlsson, T. & Pernow, M. (2022). Flavor symmetries in an SU(5) model of grand unification. Journal of High Energy Physics (JHEP) (1), Article ID 9.
Open this publication in new window or tab >>Flavor symmetries in an SU(5) model of grand unification
2022 (English)In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 1, article id 9Article in journal (Refereed) Published
Abstract [en]

We investigate the options for imposing flavor symmetries on a minimal renormalizable non-supersymmetric SU(5) grand unified theory, without introducing additional flavor-related fields. Such symmetries reduce the number of free parameters in the model and therefore lead to more predictive models. We consider the Yukawa sector of the Lagrangian, and search for all possible flavor symmetries. As a result, we find 25 distinct realistic flavor symmetry cases, with DOUBLE-STRUCK CAPITAL Z(2), DOUBLE-STRUCK CAPITAL Z(3), DOUBLE-STRUCK CAPITAL Z(4), and U(1) symmetries, and no non-Abelian cases.

Place, publisher, year, edition, pages
Springer Nature, 2022
Keywords
Beyond Standard Model, GUT, Discrete Symmetries
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-307306 (URN)10.1007/JHEP01(2022)009 (DOI)000739950500003 ()2-s2.0-85122380528 (Scopus ID)
Note

QC 20220120

Available from: 2022-01-20 Created: 2022-01-20 Last updated: 2024-03-18Bibliographically approved
Ohlsson, T. & Pernow, M. (2022). One-loop matching conditions in neutrino effective theory. Nuclear Physics B, 978, Article ID 115729.
Open this publication in new window or tab >>One-loop matching conditions in neutrino effective theory
2022 (English)In: Nuclear Physics B, ISSN 0550-3213, E-ISSN 1873-1562, Vol. 978, article id 115729Article in journal (Refereed) Published
Abstract [en]

We investigate matching conditions and threshold corrections between full and effective theories based on the type I seesaw mechanism. In general, using an intuitive Feynman diagrammatical approach, we compute the amplitudes before and after integrating out heavy right-handed neutrinos at the matching scale. In particular, we derive the one-loop matching conditions between the full and the effective theories. The matching conditions of the parameters are influenced by one-loop corrections to the corresponding vertices as well as wave function corrections for the Higgs and the lepton fields. Our results are comparable to earlier results based on a functional approach.

Place, publisher, year, edition, pages
Elsevier BV, 2022
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-314229 (URN)10.1016/j.nuclphysb.2022.115729 (DOI)000793283800006 ()2-s2.0-85127339502 (Scopus ID)
Note

QC 20220617

Available from: 2022-06-17 Created: 2022-06-17 Last updated: 2022-06-25Bibliographically approved
Beiming, C., Grönroos, J. & Ohlsson, T. (2022). Phenomenological mass model for exotic hadrons and predictions for masses of non-strange dibaryons as hexaquarks. Nuclear Physics B, 974, 115616, Article ID 115616.
Open this publication in new window or tab >>Phenomenological mass model for exotic hadrons and predictions for masses of non-strange dibaryons as hexaquarks
2022 (English)In: Nuclear Physics B, ISSN 0550-3213, E-ISSN 1873-1562, Vol. 974, p. 115616-, article id 115616Article in journal (Refereed) Published
Abstract [en]

We investigate the mass spectra of exotic hadrons known as hexaquarks in the form of dibaryons. We use a phenomenological model based on an extended version of the Giirsey-Radicati mass formula for hadrons to include non-charmed baryons, charmed baryons, and non-strange dibaryons to be able to predict masses of potential dibaryon states. We perform six numerical fits of this model to input data for three different sets of masses of baryons and dibaryons. We find that the model can fit some of the data sets well, especially the sets including charmed baryons and non-strange dibaryons, and observe that the predicted mass of one of the dibaryons is close to the measured mass of the observed hexaquark candidate d * (2380) reported by the WASA-at-COSY experiment. The predicted mass of the deuteron is slightly larger than its measured mass. Finally, for the data sets including charmed baryon and non-strange dibaryon masses, we find that the predicted masses of potential dibaryon states are all in the range from 1900 MeV to 3700 MeV.

Place, publisher, year, edition, pages
Elsevier BV, 2022
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-306763 (URN)10.1016/j.nuclphysb.2021.115616 (DOI)000729500200003 ()2-s2.0-85119529360 (Scopus ID)
Note

QC 20211230

Available from: 2021-12-30 Created: 2021-12-30 Last updated: 2022-06-25Bibliographically approved
Alekou, A., Baussan, E., Bhattacharyya, A. K., Kraljevic, N. B., Blennow, M., Bogomilov, M., . . . Zou, Y. (2022). The European Spallation Source neutrino super-beam conceptual design report. The European Physical Journal Special Topics, 231(21), 3779-3955
Open this publication in new window or tab >>The European Spallation Source neutrino super-beam conceptual design report
Show others...
2022 (English)In: The European Physical Journal Special Topics, ISSN 1951-6355, E-ISSN 1951-6401, Vol. 231, no 21, p. 3779-3955Article in journal (Refereed) Published
Abstract [en]

A design study, named ESS νSB for European Spallation Source neutrino Super Beam, has been carried out during the years 2018–2022 of how the 5 MW proton linear accelerator of the European Spallation Source under construction in Lund, Sweden, can be used to produce the world’s most intense long-baseline neutrino beam. The high beam intensity will allow for measuring the neutrino oscillations near the second oscillation maximum at which the CP violation signal is close to three times higher than at the first maximum, where other experiments measure. This will enable CP violation discovery in the leptonic sector for a wider range of values of the CP violating phase δCP and, in particular, a higher precision measurement of δCP. The present Conceptual Design Report describes the results of the design study of the required upgrade of the ESS linac, of the accumulator ring used to compress the linac pulses from 2.86 ms to 1.2 μs, and of the target station, where the 5 MW proton beam is used to produce the intense neutrino beam. It also presents the design of the near detector, which is used to monitor the neutrino beam as well as to measure neutrino cross sections, and of the large underground far detector located 360 km from ESS, where the magnitude of the oscillation appearance of νe from νμ is measured. The physics performance of the ESS νSB research facility has been evaluated demonstrating that after 10 years of data-taking, leptonic CP violation can be detected with more than 5 standard deviation significance over 70% of the range of values that the CP violation phase angle δCP can take and that δCP can be measured with a standard error less than 8° irrespective of the measured value of δCP. These results demonstrate the uniquely high physics performance of the proposed ESS νSB research facility. 

Place, publisher, year, edition, pages
Springer Nature, 2022
National Category
Accelerator Physics and Instrumentation
Identifiers
urn:nbn:se:kth:diva-329013 (URN)10.1140/epjs/s11734-022-00664-w (DOI)000884643800003 ()2-s2.0-85142170052 (Scopus ID)
Note

Correction in European Physical Journal: Special Topics, DOI:10.1140/epjs/s11734-022-00729-w, Scopus:2-s2.0-85159309766

QC 20230921

Available from: 2023-06-14 Created: 2023-06-14 Last updated: 2023-09-21Bibliographically approved
Ohlsson, T. & Zhou, S. (2021). Density-matrix formalism for PT-symmetric non-Hermitian Hamiltonians with the Lindblad equation. Physical Review A: covering atomic, molecular, and optical physics and quantum information, 103(2), Article ID 022218.
Open this publication in new window or tab >>Density-matrix formalism for PT-symmetric non-Hermitian Hamiltonians with the Lindblad equation
2021 (English)In: Physical Review A: covering atomic, molecular, and optical physics and quantum information, ISSN 2469-9926, E-ISSN 2469-9934, Vol. 103, no 2, article id 022218Article in journal (Refereed) Published
Abstract [en]

In the presence of Lindblad decoherence, i.e., dissipative effects in an open quantum system due to interaction with an environment, we examine the transition probabilities between the eigenstates in the two-level quantum system described by non-Hermitian Hamiltonians with the Lindblad equation, for which the parity-time-reversal (PT) symmetry is conserved. First, the density matrix formalism for PT-symmetric non-Hermitian Hamiltonian systems is developed. It is shown that the Lindblad operators L-j are pseudo-Hermitian, namely, eta L-j eta(-1) = L-j(up arrow) with eta being a linear and positive-definite metric, and respect the PT symmetry as well. We demonstrate that the generalized density matrix rho(G)(t) rho(t )eta, instead of the normalized density matrix rho(N)(t) rho(t )/tr[rho(t)], should be implemented for the calculation of the transition probabilities in accordance with the linearity requirement. Second, the density matrix formalism is used to derive the transition probabilities in general cases of PT-symmetric non-Hermitian Hamiltonians. In some concrete examples, we calculate compact analytical formulas for the transition probabilities and explore their main features with numerical illustrations. We also make a comparison between our present results and our previous ones using state vectors in the absence of Lindblad decoherence.

Place, publisher, year, edition, pages
American Physical Society (APS), 2021
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-291776 (URN)10.1103/PhysRevA.103.022218 (DOI)000620345100002 ()2-s2.0-85101768240 (Scopus ID)
Note

QC 20210322

Available from: 2021-03-22 Created: 2021-03-22 Last updated: 2022-06-25Bibliographically approved
Choubey, S., Ghosh, M., Kempe, D. & Ohlsson, T. (2021). Exploring invisible neutrino decay at ESSnuSB. Journal of High Energy Physics (JHEP), 2021(5), Article ID 133.
Open this publication in new window or tab >>Exploring invisible neutrino decay at ESSnuSB
2021 (English)In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, Vol. 2021, no 5, article id 133Article in journal (Refereed) Published
Abstract [en]

We explore invisible neutrino decay in which a heavy active neutrino state decays into a light sterile neutrino state and present a comparative analysis of two baseline options, 540 km and 360 km, for the ESSnuSB experimental setup. Our analysis shows that ESSnuSB can put a bound on the decay parameter tau (3)/m(3) = 2.64 (1.68) x 10(-11) s/eV for the baseline option of 360 (540) km at 3 sigma. The expected bound obtained for 360 km is slightly better than the corresponding one of DUNE for a charged current (CC) analysis. Furthermore, we show that the capability of ESSnuSB to discover decay, and to measure the decay parameter precisely, is better for the baseline option of 540 km than that of 360 km. Regarding effects of decay in delta (CP) measurements, we find that in general the CP violation discovery potential is better in the presence of decay. The change in CP precision is significant if one assumes decay in data but no decay in theory.

Place, publisher, year, edition, pages
Springer Nature, 2021
Keywords
Beyond Standard Model, Neutrino Physics, CP violation
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-296653 (URN)10.1007/JHEP05(2021)133 (DOI)000656977200003 ()2-s2.0-85106336528 (Scopus ID)
Note

QC 20210629

Available from: 2021-06-29 Created: 2021-06-29 Last updated: 2022-06-25Bibliographically approved
Ohlsson, T. & Pernow, M. (2021). Flavor symmetries in the Yukawa sector of non-supersymmetric SO(10): numerical fits using renormalization group running. Journal of High Energy Physics (JHEP) (9), Article ID 111.
Open this publication in new window or tab >>Flavor symmetries in the Yukawa sector of non-supersymmetric SO(10): numerical fits using renormalization group running
2021 (English)In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 9, article id 111Article in journal (Refereed) Published
Abstract [en]

We consider a class of SO(10) models with flavor symmetries in the Yukawa sector and investigate their viability by performing numerical fits to the fermion masses and mixing parameters. The fitting procedure involves a top-down approach in which we solve the renormalization group equations from the scale of grand unification down to the electroweak scale. This allows the intermediate scale right-handed neutrinos and scalar triplet, involved in the type I and II seesaw mechanisms, to be integrated out at their corresponding mass scales, leading to a correct renormalization group running. The result is that, of the 14 models considered, only two are able to fit the known data well. Both these two models correspond to Z(2) symmetries. In addition to being able to fit the fermion masses and mixing parameters, they provide predictions for the sum of light neutrino masses and the effective neutrinoless double beta decay mass parameter, which are both within current observational bounds.

Place, publisher, year, edition, pages
Springer Nature, 2021
Keywords
Beyond Standard Model, Discrete Symmetries, GUT, Neutrino Physics
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-303051 (URN)10.1007/JHEP09(2021)111 (DOI)000697366300001 ()2-s2.0-85115219413 (Scopus ID)
Note

QC 20211005

Available from: 2021-10-05 Created: 2021-10-05 Last updated: 2022-06-25Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-3525-8349

Search in DiVA

Show all publications