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Baryon and Lepton Numbers in Particle Physics beyond the Standard Model


Arnold, Jonathan Mark (2014) Baryon and Lepton Numbers in Particle Physics beyond the Standard Model. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/74JV-BN09.


The works presented in this thesis explore a variety of extensions of the standard model of particle physics which are motivated by baryon number (B) and lepton number (L), or some combination thereof. In the standard model, both baryon number and lepton number are accidental global symmetries violated only by non-perturbative weak effects, though the combination B-L is exactly conserved. Although there is currently no evidence for considering these symmetries as fundamental, there are strong phenomenological bounds restricting the existence of new physics violating B or L. In particular, there are strict limits on the lifetime of the proton whose decay would violate baryon number by one unit and lepton number by an odd number of units.

The first paper included in this thesis explores some of the simplest possible extensions of the standard model in which baryon number is violated, but the proton does not decay as a result. The second paper extends this analysis to explore models in which baryon number is conserved, but lepton flavor violation is present. Special attention is given to the processes of μ to e conversion and μ → eγ which are bound by existing experimental limits and relevant to future experiments.

The final two papers explore extensions of the minimal supersymmetric standard model (MSSM) in which both baryon number and lepton number, or the combination B-L, are elevated to the status of being spontaneously broken local symmetries. These models have a rich phenomenology including new collider signatures, stable dark matter candidates, and alternatives to the discrete R-parity symmetry usually built into the MSSM in order to protect against baryon and lepton number violating processes.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Baryon number, lepton number, beyond the standard model
Degree Grantor:California Institute of Technology
Division:Physics, Mathematics and Astronomy
Major Option:Physics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Wise, Mark B.
Group:Caltech Theory
Thesis Committee:
  • Wise, Mark B. (chair)
  • Patterson, Ryan B.
  • Carroll, Sean M.
  • Cheung, Clifford W.
Defense Date:1 May 2014
Record Number:CaltechTHESIS:05022014-140735377
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:8211
Deposited By: Jonathan Arnold
Deposited On:20 May 2014 16:40
Last Modified:26 Oct 2021 17:55

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