scholarly journals HEAVY MAJORANA NEUTRINOS AND BARYOGENESIS

1999 ◽  
Vol 14 (12) ◽  
pp. 1811-1857 ◽  
Author(s):  
APOSTOLOS PILAFTSIS
Keyword(s):  
Z Boson ◽  
Lepton Number ◽  
Cpt Invariance ◽  
Boltzmann Equations ◽  
Lepton Flavor ◽  
Particle Mixing ◽  
Majorana Neutrinos ◽  
Electron Electric Dipole Moment ◽  
Z Boson Decays ◽  
The Universe

The scenario of baryogenesis through leptogenesis is reviewed in models involving heavy Majorana neutrinos. The various mechanisms of CP violation occurring in the out-of-equilibrium lepton-number-violating decays of heavy Majorana neutrinos are studied within a resummation approach to unstable-particle mixing. It is explicitly demonstrated how the resummation approach preserves crucial field-theoretic properties such as unitarity and CPT invariance. Predictions of representative scenarios are presented after solving numerically the Boltzmann equations describing the thermodynamic evolution of the Universe. The phenomenological consequences of loop effects of heavy Majorana neutrinos on low-energy observables, such as lepton-flavor and/or lepton-number nonconservation in τ and Z-boson decays and electron electric dipole moment, are discussed.

scholarly journals Complete leading-order standard model corrections to quantum leptogenesis

2020 ◽  
Vol 2020 (9) ◽  
Author(s):  
Paul Frederik Depta ◽  
Andreas Halsch ◽  
Janine Hütig ◽  
Sebastian Mendizabal ◽  
Owe Philipsen
Keyword(s):  
Standard Model ◽  
Gauge Coupling ◽  
Thermal Bath ◽  
Leading Order ◽  
Boltzmann Equations ◽  
The Standard Model ◽  
Majorana Neutrinos ◽  
Infinite Loop ◽  
First Time ◽  
The Universe

Abstract Thermal leptogenesis, in the framework of the standard model with three additional heavy Majorana neutrinos, provides an attractive scenario to explain the observed baryon asymmetry in the universe. It is based on the out-of-equilibrium decay of Majorana neutrinos in a thermal bath of standard model particles, which in a fully quantum field theoretical formalism is obtained by solving Kadanoff-Baym equations. So far, the leading two-loop contributions from leptons and Higgs particles are included, but not yet gauge corrections. These enter at three-loop level but, in certain kinematical regimes, require a resummation to infinite loop order for a result to leading order in the gauge coupling. In this work, we apply such a resummation to the calculation of the lepton number density. The full result for the simplest “vanilla leptogenesis” scenario is by $$ \mathcal{O} $$ O (1) increased compared to that of quantum Boltzmann equations, and for the first time permits an estimate of all theoretical uncertainties. This step completes the quantum theory of leptogenesis and forms the basis for quantitative evaluations, as well as extensions to other scenarios.

scholarly journals Predictive S4 flavon model with TM1 mixing and baryogenesis through leptogenesis

2020 ◽  
Vol 2020 (9) ◽  
Author(s):  
Mainak Chakraborty ◽  
R. Krishnan ◽  
Ambar Ghosal
Keyword(s):  
Neutrino Mass ◽  
Parameter Space ◽  
Mass Matrix ◽  
Mass Scale ◽  
Baryon Asymmetry ◽  
Approximate Analytic Solution ◽  
Boltzmann Equations ◽  
Majorana Neutrinos ◽  
Cp Symmetry ◽  
The Universe

Abstract We use S4 discrete group to construct a neutrino flavour model which leads to T M1 mixing and is consistent with the neutrino oscillation data. Using the model’s constrained parameter space, we predict the values of Dirac C P phase and the light neutrino mass as −1 < sin δ < −0.9 and 1.7 < m1(meV) < 5.5 respectively. We thoroughly examine the usefulness of this model in explaining the observed baryon asymmetry of the Universe. Near-maximal breaking of CP symmetry (arising due to the TM1 constraint) helps us in generating adequate baryon asymmetry through leptogenesis. We study the evolution of the asymmetry (generated due to the decay of the heavy Majorana neutrinos) starting from the primordial Universe in two different ways (i)explicitly solving network of Boltzmann equations, (ii) using approximate analytic solution and we have shown the extent of their equivalence. Nearly accurate analytical fits are used thereafter to evaluate baryon asymmetry for the whole parameter space allowed by 3σ global fit of oscillation data and to impose a constraint on the yet unbounded mass scale parameter of Dirac neutrino mass matrix. Furthermore, significant contribution of N2 decay in the context of flavoured leptogenesis is also estimated.

scholarly journals LEPTON FLAVOR CONSERVING Z BOSON DECAYS AND SCALAR UNPARTICLE

2009 ◽  
Vol 24 (05) ◽  
pp. 377-392 ◽  
Author(s):  
E. O. ILTAN
Keyword(s):  
Standard Model ◽  
Z Boson ◽  
Branching Ratios ◽  
Heavy Lepton ◽  
Lepton Flavor ◽  
Z Boson Decays ◽  
Scaling Dimension

We predict the contribution of scalar unparticle to the branching ratios of the lepton flavor conserving Z → l+l- decays and we study the discrepancy between the experimental and the QED corrected standard model branching ratios. We observe that these decays are sensitive to the unparticle scaling dimension du for its small values, especially for heavy lepton flavor output.

scholarly journals Search for Lepton-Flavor Violation in Z -Boson Decays with τ Leptons with the ATLAS Detector

2021 ◽  
Vol 127 (27) ◽  
Author(s):  
G. Aad ◽  
B. Abbott ◽  
D. C. Abbott ◽  
A. Abed Abud ◽  
K. Abeling ◽  
...  
Keyword(s):  
Z Boson ◽  
Atlas Detector ◽  
Lepton Flavor Violation ◽  
Lepton Flavor ◽  
Flavor Violation ◽  
Z Boson Decays

scholarly journals Search for decays of the 125 GeV Higgs boson into a Z boson and a ρ or ϕ meson

2020 ◽  
Vol 2020 (11) ◽  
Author(s):  
A. M. Sirunyan ◽  
◽  
A. Tumasyan ◽  
W. Adam ◽  
F. Ambrogi ◽  
...  
Keyword(s):  
Higgs Boson ◽  
Z Boson ◽  
Branching Fractions ◽  
Proton Collision ◽  
Data Set ◽  
Proton Proton ◽  
Decay Channels ◽  
Decay Products ◽  
Upper Limits ◽  
Z Boson Decays

Abstract Decays of the 125 GeV Higgs boson into a Z boson and a ρ0(770) or ϕ(1020) meson are searched for using proton-proton collision data collected by the CMS experiment at the LHC at $$ \sqrt{s} $$ s = 13 TeV. The analysed data set corresponds to an integrated luminosity of 137 fb−1. Events are selected in which the Z boson decays into a pair of electrons or a pair of muons, and the ρ and ϕ mesons decay into pairs of pions and kaons, respectively. No significant excess above the background model is observed. As different polarization states are possible for the decay products of the Z boson and ρ or ϕ mesons, affecting the signal acceptance, scenarios in which the decays are longitudinally or transversely polarized are considered. Upper limits at the 95% confidence level on the Higgs boson branching fractions into Zρ and Zϕ are determined to be 1.04–1.31% and 0.31–0.40%, respectively, where the ranges reflect the considered polarization scenarios; these values are 740–940 and 730–950 times larger than the respective standard model expectations. These results constitute the first experimental limits on the two decay channels.

scholarly journals NEUTRINO COUPLING TO COSMOLOGICAL BACKGROUND: A REVIEW ON GRAVITATIONAL BARYO/LEPTOGENESIS

2013 ◽  
Vol 22 (12) ◽  
pp. 1330030 ◽  
Author(s):  
GAETANO LAMBIASE ◽  
SUBHENDRA MOHANTY ◽  
ARAGAM R. PRASANNA
Keyword(s):  
Field Theory ◽  
Gravitational Field ◽  
Thermal Equilibrium ◽  
Energy Levels ◽  
Lepton Number ◽  
Cpt Symmetry ◽  
Cosmological Background ◽  
The Universe ◽  
General Conditions ◽  
Lepton Number Violating

In this paper, we review the theories of origin of matter–antimatter asymmetry in the universe. The general conditions for achieving baryogenesis and leptogenesis in a CPT conserving field theory have been laid down by Sakharov. In this review, we discuss scenarios where a background scalar or gravitational field spontaneously breaks the CPT symmetry and splits the energy levels between particles and antiparticles. Baryon or Lepton number violating processes in proceeding at thermal equilibrium in such backgrounds gives rise to Baryon or Lepton number asymmetry.

scholarly journals NEUTRINO MASSES, LEPTON FLAVOR MIXING AND LEPTOGENESIS IN THE MINIMAL SEESAW MODEL

2007 ◽  
Vol 16 (01) ◽  
pp. 1-50 ◽  
Author(s):  
WAN-LEI GUO ◽  
ZHI-ZHONG XING ◽  
SHUN ZHOU
Keyword(s):  
Beta Decay ◽  
Neutrino Mass ◽  
Mass Matrix ◽  
Majorana Neutrino ◽  
Double Beta Decay ◽  
Neutrino Mixing ◽  
Lepton Flavor ◽  
Seesaw Model ◽  
Flavor Mixing ◽  
Majorana Neutrinos

We present a review of neutrino phenomenology in the minimal seesaw model (MSM), an economical and intriguing extension of the Standard Model with only two heavy right-handed Majorana neutrinos. Given current neutrino oscillation data, the MSM can predict the neutrino mass spectrum and constrain the effective masses of the tritium beta decay and the neutrinoless double-beta decay. We outline five distinct schemes to parameterize the neutrino Yukawa-coupling matrix of the MSM. The lepton flavor mixing and baryogenesis via leptogenesis are investigated in some detail by taking account of possible texture zeros of the Dirac neutrino mass matrix. We derive an upper bound on the CP-violating asymmetry in the decay of the lighter right-handed Majorana neutrino. The effects of the renormalization-group evolution on the neutrino mixing parameters are analyzed, and the correlation between the CP-violating phenomena at low and high energies is highlighted. We show that the observed matter-antimatter asymmetry of the Universe can naturally be interpreted through the resonant leptogenesis mechanism at the TeV scale. The lepton-flavor-violating rare decays, such as μ→e+γ, are also discussed in the supersymmetric extension of the MSM.

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