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Phenomenology of SO(10) Grand Unified Theories
KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
2019 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Although the Standard Model (SM) of particle physics describes observations well, there are several shortcomings of it. The most crucial of these are that the SM cannot explain the origin of neutrino masses and the existence of dark matter. Furthermore, there are several aspects of it that are seemingly ad hoc, such as the choice of gauge group and the cancellation of gauge anomalies.

These shortcomings point to a theory beyond the SM. Although there are many proposed models for physics beyond the SM, in this thesis, we focus on grand unified theories based on the SO(10) gauge group. It predicts that the three gauge groups in the SM unify at a higher energy into one, which contains the SM as a subgroup. We focus on the Yukawa sector of these models and investigate the extent to which the observables such as fermion masses and mixing parameters can be accommodated into different models based on the SO(10) gauge group. Neutrino masses and leptonic mixing parameters are particularly interesting, since SO(10) models naturally embed the seesaw mechanism.

The difference in energy scale between the electroweak scale and the scale of unification spans around 14 orders of magnitude. Therefore, one must relate the parameters of the SO(10) model to those of the SM through renormalization group equations. We investigate this for several different models by performing fits of SO(10) models to fermion masses and mixing parameters, taking into account thresholds at which heavy right-handed neutrinos are integrated out of the theory. Although the results are in general dependent on the particular model under consideration, there are some general results that appear to hold true. The observ- ables of the Yukawa sector can in general be accommodated into SO(10) models only if the neutrino masses are normally ordered and that inverted ordering is strongly disfavored. We find that the observable that provides the most tension in the fits is the leptonic mixing angle θ2l3, whose value is consistently favored to be lower in the fits than the actual value. Furthermore, we find that numerical fits to the data favor type-I seesaw over type-II seesaw for the generation of neutrino masses.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2019. , p. 84
Series
TRITA-SCI-FOU ; 2019;38
Keywords [en]
Grand unified theories, Renormalization group equations, Neutrino masses, Gauge coupling unification
National Category
Subatomic Physics
Identifiers
URN: urn:nbn:se:kth:diva-259605ISBN: 978-91-7873-269-2 (print)OAI: oai:DiVA.org:kth-259605DiVA, id: diva2:1352459
Presentation
2019-10-17, FB42, Roslagstullsbacken 21, AlbaNova universitetscentrum, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

Examinator: Professor Mark Pearce, Fysik, KTH

Available from: 2019-09-19 Created: 2019-09-18 Last updated: 2019-09-19Bibliographically approved
List of papers
1. Running of fermion observables in non-supersymmetric SO(10) models
Open this publication in new window or tab >>Running of fermion observables in non-supersymmetric SO(10) models
2018 (English)In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 11, article id 028Article in journal (Refereed) Published
Abstract [en]

We investigate the complete renormalization group running of fermion observables in two different realistic non-supersymmetric models based on the gauge group SO(10) with intermediate symmetry breaking for both normal and inverted neutrino mass orderings. Contrary to results of previous works, we find that the model with the more minimal Yukawa sector of the Lagrangian fails to reproduce the measured values of observables at the electroweak scale, whereas the model with the more extended Yukawa sector can do so if the neutrino masses have normal ordering. The difficulty in finding acceptable fits to measured data is a result of the added complexity from the effect of an intermediate symmetry breaking as well as tension in the value of the leptonic mixing angle theta 23

Place, publisher, year, edition, pages
SPRINGER, 2018
Keywords
Beyond Standard Model, GUT
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-239786 (URN)10.1007/JHEP11(2018)028 (DOI)000449809000004 ()2-s2.0-85056110172 (Scopus ID)
Note

QC 20190108

Available from: 2019-01-08 Created: 2019-01-08 Last updated: 2019-09-18Bibliographically approved
2. A minimal non-supersymmetric SO(10) model with Peccei-Quinn symmetry
Open this publication in new window or tab >>A minimal non-supersymmetric SO(10) model with Peccei-Quinn symmetry
2019 (English)In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 792, p. 251-257Article in journal (Refereed) Published
Abstract [en]

We present a minimal non-supersymmetric SO(10) GUT breaking directly to the Standard Model gauge group. Precise gauge coupling unification is achieved due to the presence of two color-octet scalars, one of which is accessible to LHC searches. Proton lifetime is predicted to be below 4.5 x 10(34) years, which is within the projected five-year sensitivity of the proposed Hyper-Kamiokande experiment. We find that the Standard Model observables are reproduced to a reasonable accuracy in a numerical fit, which also predicts the unknown neutrino parameters. Finally, the two scalar representations stabilize the electroweak vacuum and the dark matter is comprised of axions.

Place, publisher, year, edition, pages
Elsevier, 2019
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-251700 (URN)10.1016/j.physletb.2019.03.045 (DOI)000466802100038 ()2-s2.0-85063758281 (Scopus ID)
Note

QC 20190520

Available from: 2019-05-20 Created: 2019-05-20 Last updated: 2019-09-18Bibliographically approved
3. Fits to non-supersymmetric SO(10) models with type I and II seesaw mechanisms using renormalization group evolution
Open this publication in new window or tab >>Fits to non-supersymmetric SO(10) models with type I and II seesaw mechanisms using renormalization group evolution
2019 (English)In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 6, article id 085Article in journal (Refereed) Published
Abstract [en]

We consider numerical fits to non-supersymmetric SO(10)-based models in which neutrino mass is generated by the type-I or type-II seesaw mechanism or a combination of both. The fits are performed with a sophisticated top-down procedure, taking into account the renormalization group equations of the gauge and Yukawa couplings, integrating out relevant degrees of freedom at their corresponding mass scales, and using recent data for the Standard Model observables. We find acceptable fits for normal neutrino mass ordering only and with neutrino mass generated by either type-I seesaw only or a combination of types I and II seesaw in which type-I seesaw is dominant. Furthermore, we find predictions from the best fit regarding the small neutrino masses, the effective neutrinoless double beta decay mass, and the leptonic CP-violating phase. Finally, we show that the fits are rather insensitive to the chosen value of the unification scale.

Place, publisher, year, edition, pages
SPRINGER, 2019
Keywords
Beyond Standard Model, GUT, Neutrino Physics
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-255188 (URN)10.1007/JHEP06(2019)085 (DOI)000472210600002 ()2-s2.0-85067629668 (Scopus ID)
Note

QC 20190904

Available from: 2019-09-04 Created: 2019-09-04 Last updated: 2019-09-18Bibliographically approved

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