The role of leptons in electroweak baryogenesis
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Springer
Received: December 11, 2018 Accepted: March 19, 2019 Published: April 3, 2019
The role of leptons in electroweak baryogenesis
a
Amherst Center for Fundamental Interactions, Department of Physics, University of Massachusetts, Amherst, MA 01003, U.S.A. b RIKEN BNL Research Center, Brookhaven National Laboratory, Upton, NY 11973-5000, U.S.A. c Nikhef, Theory Group, Science Park 105, 1098 XG, Amsterdam, The Netherlands
E-mail: [email protected], [email protected], [email protected] Abstract: We investigate the role of leptons in electroweak baryogenesis by studying a relatively simple framework inspired by effective field theory that satisfies all Sakharov conditions. In particular, we study the effectiveness of CP-violating source terms induced by dimension-six Yukawa interactions for quarks and charged leptons. Despite the relatively small Yukawa coupling, CP-violating source terms involving taus are quite effective and can account for the observed matter-antimatter asymmetry. We obtain analytical and numerical expressions for the total baryon asymmetry, the former providing important insight into what makes lepton CP violation relatively effective compared to quark CP violation. Leptons also play an important role if the CP-violating source involves top quarks. While the tau Yukawa coupling in the Standard Model is small, it significantly enhances the baryon asymmetry by transferring the chiral asymmetry in quarks, which is washed out by strong sphalerons, to a chiral asymmetry in leptons. We conclude that leptons should not be ignored even if CP violation is limited to the quark sector. The role of leptons can be further increased in scenarios of new physics with additional chiral-symmetry-breaking interactions between quarks and leptons, as can happen in models with additional Higgs bosons or leptoquarks. Finally, we study CP-violating dimension-six Yukawa interactions for lighter quarks and leptons but conclude that these lead to too small baryon asymmetries. Keywords: Cosmology of Theories beyond the SM, Beyond Standard Model, CP violation ArXiv ePrint: 1811.11104
c The Authors. Open Access, Article funded by SCOAP3 .
https://doi.org/10.1007/JHEP04(2019)024
JHEP04(2019)024
Jordy de Vries,a,b Marieke Postmac and Jorinde van de Visc
Contents 1 Introduction
1 4 4 5 7 9 11 12 13
3 Baryogenesis with a tau-lepton source 3.1 Analytical approximation 3.2 Comparison of approximations 3.3 Parameter dependence 3.4 Producing the universal baryon asymmetry with a tau source
14 14 15 16 20
4 Baryogenesis with a quark source 4.1 Top source 4.2 Producing the universal baryon asymmetry with a top source 4.3 Bottom source
20 21 24 25
5 Consequences of additional quark-lepton interactions
27
6 Discussion and conclusions
28
A Benchmark values
31
B Weak sphalerons B.1 Two-step approach B.2 One-step approach
31 32 33
C Numerical method
34
1
Introduction
Understanding the prevalence of matter over antimatter in our universe is one of the great challenges in particle physics and cosmology. The ba
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