scholarly journals The Standard Model of Particle Physics with Diracian Neutrino Sector

Symmetry ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 994 ◽  
Author(s):  
Theodorus Maria Nieuwenhuizen
Keyword(s):  
Standard Model ◽  
Particle Physics ◽  
Mass Matrix ◽  
High Energy ◽  
Solar Neutrinos ◽  
Lepton Number ◽  
Double Beta Decay ◽  
Sterile Neutrinos ◽  
Neutrino Sector ◽  
The Standard Model

The minimally extended standard model of particle physics contains three right handed or sterile neutrinos, coupled to the active ones by a Dirac mass matrix and mutually by a Majorana mass matrix. In the pseudo-Dirac case, the Majorana terms are small and maximal mixing of active and sterile states occurs, which is generally excluded for solar neutrinos. In a “Diracian” limit, the physical masses become pairwise degenerate and the neutrinos attain a Dirac signature. Members of a pair do not oscillate mutually so that their mixing can be undone, and the standard neutrino model follows as a limit. While two Majorana phases become physical Dirac phases and three extra mass parameters occur, a better description of data is offered. Oscillation problems are worked out in vacuum and in matter. With lepton number –1 assigned to the sterile neutrinos, the model still violates lepton number conservation and allows very feeble neutrinoless double beta decay. It supports a sterile neutrino interpretation of Earth-traversing ultra high energy events detected by ANITA.

scholarly journals What Is Matter According to Particle Physics, and Why Try to Observe Its Creation in a Lab?

Universe ◽  
2021 ◽  
Vol 7 (3) ◽  
pp. 61
Author(s):  
Francesco Vissani
Keyword(s):  
Standard Model ◽  
Conservation Laws ◽  
Beta Decay ◽  
Particle Physics ◽  
Neutrinoless Double Beta Decay ◽  
Lepton Number ◽  
Double Beta Decay ◽  
Nuclear Process ◽  
The Standard Model ◽  
Technical Considerations

The standard model of elementary interactions has long qualified as a theory of matter, in which the postulated conservation laws (one baryonic and three leptonic) acquire theoretical meaning. However, recent observations of lepton number violations—neutrino oscillations—demonstrate its incompleteness. We discuss why these considerations suggest the correctness of Ettore Majorana’s ideas on the nature of neutrino mass and add further interest to the search for an ultra-rare nuclear process in which two particles of matter (electrons) are created, commonly called neutrinoless double beta decay. The approach of the discussion is mainly historical, and its character is introductory. Some technical considerations, which highlight the usefulness of Majorana’s representation of gamma matrices, are presented in the appendix.

scholarly journals Chiral anomaly in SU(2)R-axion inflation and the new prediction for particle cosmology

2021 ◽  
Vol 2021 (6) ◽  
Author(s):  
Azadeh Maleknejad
Keyword(s):  
Standard Model ◽  
Symmetry Breaking ◽  
Particle Physics ◽  
Cosmological Parameters ◽  
Chiral Anomaly ◽  
Dark Matter Candidate ◽  
Neutrino Sector ◽  
Matter Creation ◽  
The Standard Model ◽  
Non Gaussian

Abstract Upon embedding the axion-inflation in the minimal left-right symmetric gauge extension of the SM with gauge group SU(2)L × SU(2)R × U(1)B−L, [1] proposed a new particle physics model for inflation. In this work, we present a more detailed analysis. As a compelling consequence, this setup provides a new mechanism for simultaneous baryogenesis and right-handed neutrino creation by the chiral anomaly of WR in inflation. The lightest right-handed neutrino is the dark matter candidate. This setup has two unknown fundamental scales, i.e., the scale of inflation and left-right symmetry breaking SU(2)R × U(1)B−L→ U(1)Y. Sufficient matter creation demands the left-right symmetry breaking scale happens shortly after the end of inflation. Interestingly, it prefers left-right symmetry breaking scales above 1010 GeV, which is in the range suggested by the non-supersymmetric SO(10) Grand Unified Theory with an intermediate left-right symmetry scale. Although WR gauge field generates equal amounts of right-handed baryons and leptons in inflation, i.e. B − L = 0, in the Standard Model sub-sector B − LSM ≠ 0. A key aspect of this setup is that SU(2)R sphalerons are never in equilibrium, and the primordial B − LSM is conserved by the Standard Model interactions. This setup yields a deep connection between CP violation in physics of inflation and matter creation (visible and dark); hence it can naturally explain the observed coincidences among cosmological parameters, i.e., ηB ≃ 0.3Pζ and ΩDM ≃ 5ΩB. The new mechanism does not rely on the largeness of the unconstrained CP-violating phases in the neutrino sector nor fine-tuned masses for the heaviest right-handed neutrinos. The SU(2)R-axion inflation comes with a cosmological smoking gun; chiral, non-Gaussian, and blue-tilted gravitational wave background, which can be probed by future CMB missions and laser interferometer detectors.

scholarly journals Neutrinoless double-beta decay: A probe of physics beyond the Standard Model

2015 ◽  
Vol 30 (04n05) ◽  
pp. 1530001 ◽  
Author(s):  
S. M. Bilenky ◽  
C. Giunti
Keyword(s):  
Standard Model ◽  
Present Status ◽  
Majorana Neutrino ◽  
Lepton Number ◽  
Double Beta Decay ◽  
Neutrino Masses ◽  
Beyond The Standard Model ◽  
Β Decay ◽  
The Standard Model ◽  
Double Β Decay

In the Standard Model the total lepton number is conserved. Thus, neutrinoless double-β decay, in which the total lepton number is violated by two units, is a probe of physics beyond the Standard Model. In this review we consider the basic mechanism of neutrinoless double-β decay induced by light Majorana neutrino masses. After a brief summary of the present status of our knowledge of neutrino masses and mixing and an introduction to the seesaw mechanism for the generation of light Majorana neutrino masses, in this review we discuss the theory and phenomenology of neutrinoless double-β decay. We present the basic elements of the theory of neutrinoless double-β decay, our view of the present status of the challenging problem of the calculation of the nuclear matrix element of the process and a summary of the experimental results.

scholarly journals Neutrinoless Double-Beta Decay: Status and Prospects

2019 ◽  
Vol 69 (1) ◽  
pp. 219-251 ◽  
Author(s):  
Michelle J. Dolinski ◽  
Alan W.P. Poon ◽  
Werner Rodejohann
Keyword(s):  
Beta Decay ◽  
Half Life ◽  
Particle Physics ◽  
Nuclear Physics ◽  
Large Scale ◽  
Neutrinoless Double Beta Decay ◽  
Lepton Number ◽  
Double Beta Decay ◽  
Beyond The Standard Model ◽  
The Standard Model

Neutrinoless double-beta decay is a forbidden, lepton-number-violating nuclear transition whose observation would have fundamental implications for neutrino physics, theories beyond the Standard Model, and cosmology. In this review, we summarize the theoretical progress to understand this process, the expectations and implications under various particle physics models, and the nuclear physics challenges that affect the precise predictions of the decay half-life. We also provide a synopsis of the current and future large-scale experiments that aim to discover this process in physically well-motivated half-life ranges.

THE ELECTRON–ELECTRON VERSION OF THE LINEAR COLLIDER — A MILLENNIUM UPDATE

2000 ◽  
Vol 15 (16) ◽  
pp. 2347-2353
Author(s):  
CLEMENS A. HEUSCH
Keyword(s):  
Standard Model ◽  
Particle Physics ◽  
Linear Collider ◽  
Electron Beams ◽  
High Energy ◽  
Beyond The Standard Model ◽  
Technical Developments ◽  
Physics Community ◽  
Incoming Electron ◽  
The Standard Model

It has become a natural mandate to the particle physics community to look beyond presently active and approved high-energy accelerators for precision work at the edge of, and beyond, the Standard Model. We stress the mandate for complementary use of both charge modes of the Electron Collider, e+e- and e+e-. Choosing a few illustrative examples, we attempt to set the stage for technical developments needed to define and execute the key experiments using two incoming electron beams.

FROM NUCLEAR PHYSICS TO PHYSICS BEYOND THE STANDARD MODEL: FIRST EVIDENCE FOR LEPTON NUMBER VIOLATION AND THE MAJORANA CHARACTER OF NEUTRINOS

2004 ◽  
Vol 13 (10) ◽  
pp. 2107-2126 ◽  
Author(s):  
H. V. KLAPDOR-KLEINGROTHAUS
Keyword(s):  
Beyond Standard Model ◽  
Standard Model ◽  
Beta Decay ◽  
Neutrino Mass ◽  
Half Life ◽  
Nuclear Physics ◽  
High Energy ◽  
Lepton Number ◽  
Double Beta Decay ◽  
Boson Mass

Nuclear double beta decay provides an extraordinarily broad potential to search for beyond-standard-model physics. The occurrence of the neutrinoless decay(0νββ) mode has fundamental consequences: first, the total lepton number is not conserved, and second, the neutrino is a Majorana particle. Furthermore, the measured effective mass provides an absolute scale of the neutrino mass spectrum. In addition, double beta experiments yield sharp restrictions for other beyond-standard-model physics. These include SUSY models (R-parity breaking and conserving), leptoquarks (leptoquark-Higgs coupling), compositeness, left-right symmetric models (right-handed W boson mass), test of special relativity and of the equivalence principle in the neutrino sector and others. First evidence for neutrinoless double beta decay was reported by the HEIDELBERG–MOSCOW experiment in 2001. The HEIDELBERG–MOSCOW experiment is by far the most sensitive0νββ experiment since more than 10 years. It is operating 11 kg of enriched 76Ge in the GRAN SASSO Underground Laboratory. The analysis of the data taken from 2 August 1990–20 May 2003 is presented here. The collected statistics is 71.7 kg y. The background achieved in the energy region of the Q value for double beta decay is 0.11 events/kg y keV. The two-neutrino accompanied half-life is determined on the basis of more than 100,000 events to be [Formula: see text] years. The confidence level for the neutrinoless signal has been improved to a 4.2σ level. The half-life is [Formula: see text] years. The effective neutrino mass deduced is (0.2–0.6) eV (99.73% C.L.), with the consequence that neutrinos have degenerate masses. The sharp boundaries for other beyond SM physics, mentioned above, are comfortably competitive to the corresponding results from high-energy accelerators like TEVATRON, HERA, etc.

scholarly journals BARYON AND LEPTON NUMBER VIOLATION WITH SCALAR BILINEARS

2002 ◽  
Vol 17 (33) ◽  
pp. 2221-2228 ◽  
Author(s):  
H. V. KLAPDOR-KLEINGROTHAUS ◽  
ERNEST MA ◽  
UTPAL SARKAR
Keyword(s):  
Standard Model ◽  
Beta Decay ◽  
Neutrinoless Double Beta Decay ◽  
Proton Decay ◽  
Lepton Number ◽  
Double Beta Decay ◽  
Lepton Number Violation ◽  
The Standard Model ◽  
Number Violation ◽  
Lepton Number Violating

We consider all possible scalar bilinears, which couple to two fermions of the standard model. The various baryon and lepton number violating couplings allowed by these exotic scalars are studied. We then discuss which are constrained by limits on proton decay (to a lepton and a meson as well as to three leptons), neutron–antineutron oscillations, and neutrinoless double beta decay.

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