scholarly journals Time Evolution of Lepton Number Carried by Majorana Neutrinos

2021 ◽  
Author(s):  
Apriadi Salim Adam ◽  
Nicholas J Benoit ◽  
Yuta Kawamura ◽  
Yamato Matsuo ◽  
Takuya Morozumi ◽  
...  
Keyword(s):  
Time Evolution ◽  
Charged Lepton ◽  
Mass Matrix ◽  
Mass Term ◽  
Big Bang ◽  
Mass Hierarchy ◽  
Majorana Mass ◽  
Cosmic Neutrino Background ◽  
Cosmic Neutrino ◽  
Lepton Family

Abstract We revisit the time evolution of the lepton family number for a SU(2) doublet consisting of a neutrino and a charged lepton. The lepton family number is defined through the weak basis of the SU(2) doublet, where the charged lepton mass matrix is real and diagonal. The lepton family number carried by the neutrino is defined by the left-handed current of the neutrino family. For this work we assume the neutrinos have Majorana mass. This Majorana mass term is switched on at time t = 0 and the lepton family number is evolved. Since the operator in the avor eigenstate is continuously connected to that of the mass eigenstate, the creation and annihilation operators for the two eigenstates are related to each other. We compute the time evolution of all lepton family numbers by choosing a specific initial avor eigenstate for a neutrino. The evolution is studied for relativistic and nonrelativistic neutrinos. The nonrelativistic region is of particular interest for the Cosmic Neutrino Background predicted from big bang models. In that region we find the lepton family numbers are sensitive to Majorana and Dirac phases, the absolute mass, and mass hierarchy of neutrinos.

scholarly journals Lepton number violation in a unified framework

2020 ◽  
Vol 2020 (9) ◽  
Author(s):  
Yuta Kawamura ◽  
Yamato Matsuo ◽  
Takuya Morozumi ◽  
Apriadi Salim Adam ◽  
Yusuke Shimizu ◽  
...  
Keyword(s):  
Time Evolution ◽  
Charged Lepton ◽  
Mass Matrix ◽  
Mass Term ◽  
Majorana Neutrino ◽  
Lepton Number ◽  
Mass Hierarchy ◽  
Unified Framework ◽  
Initial State ◽  
Lepton Family

Abstract We study the time evolution of lepton family number for a neutrino that forms an SU(2) doublet with a charged lepton. The lepton family number is defined through a weak basis of the SU(2) doublet in which the charged lepton mass matrix is a real and diagonal one. The lepton family number carried by the neutrino is defined with a left-handed current of the neutrino family. We study the time evolution of the lepton family number operator for the Majorana neutrino. To be definite, we introduce the mass term at $t=0$ and study the time evolution of the lepton family number for the later time. Since the operator in the flavor eigenstate is continuously connected to that of the mass eigenstate, the creation and annihilation operators for the flavor eigenstates are related to those of the mass eigenstates. The total lepton number of the Majorana neutrino is conserved. By choosing a specific flavor eigenstate of the neutrino as an initial state, we compute the time evolution of all lepton family numbers. They are sensitive to Majorana and Dirac phases and are also sensitive to the absolute mass and mass hierarchy of neutrinos.

scholarly journals Can one measure the Cosmic Neutrino Background?

2017 ◽  
Vol 26 (01n02) ◽  
pp. 1740008 ◽  
Author(s):  
Amand Faessler ◽  
Rastislav Hodák ◽  
Sergey Kovalenko ◽  
Fedor Šimkovic
Keyword(s):  
Rest Mass ◽  
Big Bang ◽  
Electron Neutrino ◽  
Electron Neutrinos ◽  
Cosmic Neutrino Background ◽  
Cosmic Neutrino ◽  
The Moment ◽  
Katrin Experiment ◽  
The Big Bang ◽  
Neutrino Background

The Cosmic Microwave Background (CMB) yields information about our Universe at around 380,000 years after the Big Bang (BB). Due to the weak interaction of the neutrinos with matter, the Cosmic Neutrino Background (CNB) should give information about a much earlier time of our Universe, around one second after the BB. Probably, the most promising method to “see” the CNB is the capture of the electron neutrinos from the Background by Tritium, which then decays into 3He and an electron with the energy of the the [Formula: see text]-value [Formula: see text] 18.562[Formula: see text]keV plus the electron neutrino rest mass. The “KArlsruhe TRItium Neutrino” (KATRIN) experiment, which is in preparation, seems presently the most sensitive proposed method for measuring the electron antineutrino mass. At the same time, KATRIN can also look by the reaction [Formula: see text]. The capture of the Cosmic Background Neutrinos (CNB) should show in the electron spectrum as a peak by the electron neutrino rest mass above [Formula: see text]. Here, the possibility to see the CNB with KATRIN is studied. A detection of the CNB by KATRIN seems not to be possible at the moment. But KATRIN should be able to determine an upper limit for the local electron neutrino density of the CNB.

Detection prospects of the cosmic neutrino background

2015 ◽  
Vol 30 (12) ◽  
pp. 1530031 ◽  
Author(s):  
Yu-Feng Li
Keyword(s):  
Direct Detection ◽  
High Energy ◽  
Big Bang ◽  
Observational Evidence ◽  
Future Prospects ◽  
Cosmic Neutrino Background ◽  
Cosmic Neutrino ◽  
Massive Neutrinos ◽  
Neutrino Background ◽  
Excitation Method

The existence of the cosmic neutrino background (CνB) is a fundamental prediction of the standard Big Bang cosmology. Although current cosmological probes provide indirect observational evidence, the direct detection of the CνB in a laboratory experiment is a great challenge to the present experimental techniques. We discuss the future prospects for the direct detection of the CνB, with the emphasis on the method of captures on beta-decaying nuclei and the PTOLEMY project. Other possibilities using the electron-capture (EC) decaying nuclei, the annihilation of extremely high-energy cosmic neutrinos (EHECνs) at the Z-resonance, and the atomic de-excitation method are also discussed in this review (talk given at the International Conference on Massive Neutrinos, Singapore, 9–13 February 2015).

scholarly journals Relating lepton mixing angles with lepton mass hierarchy

2016 ◽  
Vol 31 (04n05) ◽  
pp. 1650002
Author(s):  
Debasish Borah
Keyword(s):  
Neutrino Mass ◽  
Charged Lepton ◽  
Mass Matrix ◽  
Neutrino Masses ◽  
Mass Hierarchy ◽  
Mixing Angle ◽  
Mixing Angles ◽  
Mass Matrices ◽  
Model Independent ◽  
The Difference

We revisit the possibility of relating lepton mixing angles with lepton mass hierarchies in a model-independent way. Guided by the existence of such relations in the quark sector, we first consider all the mixing angles, both in charged lepton and neutrino sectors to be related to the respective mass ratios. This allows us to calculate the leptonic mixing angles observed in neutrino oscillations as functions of the lightest neutrino mass. We show that for both normal and inverted hierarchical neutrino masses, this scenario does not give rise to correct leptonic mixing angles. We then show that correct leptonic mixing angles can be generated with normal hierarchical neutrino masses if the relation between mixing angle and mass ratio is restricted to 1–2 and 1–3 mixing in both charged lepton and neutrino sectors leaving the 2–3 mixing angles as free parameters. We then restrict the lightest neutrino mass as well as the difference between 2–3 mixing angles in charged lepton and neutrino sectors from the requirement of producing correct leptonic mixing angles. We constrain the lightest neutrino mass to be around 0.002 eV and leptonic Dirac CP phase [Formula: see text] such that [Formula: see text]. We also construct the leptonic mass matrices in terms of 2–3 mixing angles and lightest neutrino mass and briefly comment on the possibility of realizing texture zeros in the neutrino mass matrix.

scholarly journals SEESAW AND LEPTOGENESIS: A TRIANGULAR ANSATZ

2011 ◽  
Vol 26 (18) ◽  
pp. 1375-1379 ◽  
Author(s):  
D. FALCONE
Keyword(s):  
Charged Lepton ◽  
Mass Matrix ◽  
Triangular Matrix ◽  
Unitary Matrix ◽  
Seesaw Mechanism ◽  
Dirac Mass ◽  
Majorana Mass ◽  
Dirac Matrix

A triangular ansatz for the seesaw mechanism and baryogenesis via leptogenesis is explored. In a basis where both the charged lepton and the Majorana mass matrix are diagonal, the Dirac mass matrix can generally be written as the product of a unitary times a triangular matrix. We assume the unitary matrix to be the identity and then an upper triangular Dirac matrix. Constraints from bilarge lepton mixing and leptogenesis are studied.

scholarly journals Neutrino interactions in the late universe

2021 ◽  
Vol 2021 (11) ◽  
Author(s):  
Daniel Green ◽  
David E. Kaplan ◽  
Surjeet Rajendran
Keyword(s):  
Dark Matter ◽  
Big Bang ◽  
Late Time ◽  
Beyond The Standard Model ◽  
Neutrino Sector ◽  
Cosmic Neutrino Background ◽  
Wide Range ◽  
Cosmic Neutrino ◽  
Near Term ◽  
The Impact

Abstract The cosmic neutrino background is both a dramatic prediction of the hot Big Bang and a compelling target for current and future observations. The impact of relativistic neutrinos in the early universe has been observed at high significance in a number of cosmological probes. In addition, the non-zero mass of neutrinos alters the growth of structure at late times, and this signature is a target for a number of upcoming surveys. These measurements are sensitive to the physics of the neutrino and could be used to probe physics beyond the standard model in the neutrino sector. We explore an intriguing possibility where light right-handed neutrinos are coupled to all, or a fraction of, the dark matter through a mediator. In a wide range of parameter space, this interaction only becomes important at late times and is uniquely probed by late-time cosmological observables. Due to this coupling, the dark matter and neutrinos behave as a single fluid with a non-trivial sound speed, leading to a suppression of power on small scales. In current and near-term cosmological surveys, this signature is equivalent to an increase in the sum of the neutrino masses. Given current limits, we show that at most 0.5% of the dark matter could be coupled to neutrinos in this way.

scholarly journals LEPTON FAMILY SYMMETRY AND NEUTRINO MASS MATRIX

2004 ◽  
Vol 19 (08) ◽  
pp. 577-582 ◽  
Author(s):  
ERNEST MA
Keyword(s):  
Standard Model ◽  
Neutrino Mass ◽  
Solar Neutrino ◽  
Charged Lepton ◽  
Mass Matrix ◽  
Neutrino Mass Matrix ◽  
Diagonal Form ◽  
Family Symmetry ◽  
The Standard Model ◽  
Lepton Family

The standard model of leptons is extended to accommodate a discrete Z3×Z2 family symmetry. After rotating the charged-lepton mass matrix to its diagonal form, the neutrino mass matrix reveals itself as very suitable for explaining atmospheric and solar neutrino oscillation data. A generic requirement of this approach is the appearance of three Higgs doublets at the electroweak scale, with observable flavor violating decays.

scholarly journals A SOLUTION TO THE STRONG CP PROBLEM TRANSFORMING THE THETA ANGLE TO THE KM CP-VIOLATING PHASE

2010 ◽  
Vol 25 (32) ◽  
pp. 5897-5911 ◽  
Author(s):  
JOSÉ BORDES ◽  
HONG-MO CHAN ◽  
SHEUNG TSUN TSOU
Keyword(s):  
Mass Matrix ◽  
Fermion Mass ◽  
Mass Hierarchy ◽  
Order Unity ◽  
Ckm Matrix ◽  
Cp Violations ◽  
Fermion Mass Matrix

It is shown that in the scheme with a rotating fermion mass matrix (i.e. one with a scale-dependent orientation in generation space) suggested earlier for explaining fermion mixing and mass hierarchy, the theta angle term in the QCD action of topological origin can be eliminated by chiral transformations, while giving still nonzero masses to all quarks. Instead, the effects of such transformations get transmitted by the rotation to the CKM matrix as the KM phase giving, for θ of order unity, a Jarlskog invariant typically of order 10-5, as experimentally observed. Strong and weak CP violations appear then as just two facets of the same phenomenon.

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