We use the scale of neutrinomass and naturalness considerations to obtain model-independent expectations for the magnitude of possible contributions to muon decay Michel parameters from new physics above the electroweak symmetry-breaking scale. Focusing on Dirac neu- trinos, we obtain a complete basis of effective dimension four and dimension six operators that are invariant under the gauge symmetry of the Standard Model and that contribute to both muon decay and neutrinomass. We show that—in the absence of fine tuning—the most stringent neutrinomass naturalness bounds on chirality-changing vector operators rel- evant to muon decay arise from one-loop operator mixing. The bounds we obtain on their contributions to the Michel parameters are two orders of magnitude stronger than bounds previously obtained in the literature. In addition, we analyze the implications of one-loop matching considerations and find that the expectations for the size of various scalar and tensor contributions to the Michel parameters are considerably smaller than those derived from previous estimates of two-loop operator mixing. We also show, however, that there exist gauge-invariant operators that generate scalar and tensor contributions to muon de- cay but whose flavor structure allows them to evade neutrinomass naturalness bounds. We discuss the implications of our analysis for the interpretation of muon decay experiments.
cal (NH) and Inverted Hierarchical (IH), are discussed in our earlier work [14,15]. Out of these three models which model can give good prediction to the neutrino oscilla- tion is also a topical question in recent neutrino physics. In this work we analyze on Quasi-degenerate neutrinomass model (NH and IH) with different mixing pattern as discussed above. In Section 2, we shown neutrinos are quasi-degenerate (NH and IH) in nature considering neu- trinos are mixed tribimaximally. Next in Section 3, dif- ferent neutrinomass models with BM and HM consider- ing neutrinos are quasi-degenerate in nature are discussed. Then with the help of charged lepton correction how these mixing can predict new mixing which are consis- tent with recent experimental data along with non-zero
In this article an idea is presented, which allows for the explanation of superluminal muon neutrinos. It is based on the introduction of a new superluminal, massless gauge boson coupling to the neutrino only, but not to other standard mod- el particles. The model is discussed with regard to the Supernova 1987 (SN 1987) velocity bound on electron antineu- trinos and the Cohen-Glashow constraint on superluminal neutrino propagation. The latter can be circumvented if— within the framework of the model—a sterile neutrinomixing with the active neutrinomass eigenstates is introduced. The suggestion of a sterile neutrino accounting for superluminal neutrinos has already been proposed in several papers. It is possible to choose mixing angles with the sterile neutrino sector such that the model respects both the SN 1987 bound and the muon neutrino travels superluminally.
Recently, two other options have been put forward , which allow for significant suppression of sterile neutrino production in the early Universe which still goes mostly through the active-sterile mixing. The first option exploits the very light free scalar field, which is frozen at high value in the early Universe. Then coupling (9) makes sterile neutrino superheavy in the early Universe, which kinematically suppresses all possible oscillations. The scalar remains frozen until the Hubble param- eter drops to the value of the scalar mass. Then the field starts to oscillate with decreasing amplitude and by the present epoch the scalar contribution to the sterile neutrinomass (9) can be neglected. Some amount of sterile neutrinos can be produced in neutrino oscillations while the scalar amplitude drops. However, by choosing the scalar parameters one can make this amount as small as possible.
This work is based on the talk given at the XXth International Seminar “Quarks-2018”, which was based on my part of work in yet unpublished paper , written in co-authorship with Timofey Grigorin-Ryabov. The goal of this paper is to study the dependence of minimal mixing, consistent with the seesaw mechanism, on CP-violating phases, unaccounted before in Ref. . During this research it also became obvious that the role of lightest active neutrinomass can be essential. The obtained results can be used to estimate the sensitivity of future experiments required to fully explore the parameter space of type I seesaw models with sterile neutrinos in the interesting mass range.
The effects of CP-phases on the three absolute quasi-degenerate Majorana neutrino (QDN) masses are stud- ied with neutrinomass matrices obeying µ – τ symmetry for normal as well as inverted hierarchical mass patterns. We have made further investigations on 1) the prediction of solar mixing angle which lies below tri-bimaximal mixing value in consistent with neutrino oscillation observational data, 2) the prediction on absolute neutrinomass parameter (m ee ) in 0νββ decay, and 3) cosmological bound on the sum of the three
Neutrino oscillation data so far tell us about differences in the squared masses of the neutrinomass states, and about the sign of the mass-squared difference between two of the states, but not about the difference of those with respect to the third, which may be heavier (normal ordering) or lighter (inverted ordering) than the other two. Resolving this neutrinomass hierarchy ambiguity, along with precise measurements of neutrinomixing angles, would have significant theoretical, cosmological and experimental implications. One important consequence of mass hierarchy deter- mination, in particular, would be the impact on future experiments designed to determine whether — uniquely among the fundamental fermions — neutrinos are their own antiparticles, so-called Majorana particles. Though long suspected, this hypothesis that neutrinos are Majorana particles has yet to be either established or ruled out. Strong evidence for the inverted hierarchy would estab- lish conditions required by the next generation of neutrinoless double-beta decay searches to settle this question even with a null result (no observation). Because the forward scattering of neutrinos in matter alters the oscillation pattern in a hierarchy-dependent way, the long baseline of LBNE — with the neutrinos traveling through the Earth’s mantle — enables a decisive determination of the hierarchy, independent of the value of δ CP .
However, despite this success, few physicists believe that the SM is valid up to arbitrarily high energies; the SM contains 19 free parameters (not including neutrino masses and mixing angles!) which currently must be put in by hand, does not explain why fermions seem to come in three flavors or predict their masses, and requires the existence of a Higgs boson with a mass not too far from the weak scale, even though radiative corrections would be expected to push its mass up to the Planck scale. Additionally, as the SM does not address the issue of neutrinomass at all, does not explain the matter-antimatter asymmetry in the universe, and fails miserably to explain the cosmological constant, we now have conclusive evidence of physics beyond the SM.
The Standard Model (SM)  is the name given in the 1970s to a theory of fundamental particles and how they interact. The SM is very successful at energies up to about hundred GeV. The SM has passed numerous experimental tests. However, despite its tremendous successes, no one …nds the SM satisfactory, and it is widely expected that there is physics beyond the SM, with new characteristic mass scale(s), perhaps up to, ultimately, a string scale. In the absence of any direct evidence for their mass, neutrinos were introduced in the SM as truly massless fermions for which no gauge-invariant renormalizable mass term can be constructed. Consequently, in the SM there is no mixing in the lepton sector. However, the evidences of neutrino oscillations were found in the Super-Kamiokande , SNO , KamLAND , and other solar [6, 7, 8, 9] and atmospheric [10, 11] neutrino experiments of neutrino oscillations. Observation of neutrino oscillations gives us the …rst sign of physics beyond the SM. New physics seems to have manifested itself in the form of neutrino masses and lepton mixing. In this way, neutrino masses can be connected to other new physics.
the SM of particle physics. The data obtained in neutrino oscillation experi- ments may provide key information on nature of the New Physics beyond the SM. Neutrino physics might even open up the possibility to study more funda- mental questions with respect to the origins of flavour, i.e. what is the source of the patterns we observe in both quark and lepton masses and mixing. These open questions may also imply that the SM is merely an effective low-energy theory of some yet unknown complete high-energy theory. Explaining both the smallness of neutrino masses relative to the charged lepton masses and the large leptonic mixing compared to the mixing in the quark sector sets the main goal for model building in the neutrino sector, different approaches to which will be reviewed in section 3.1. Note that many New Physics settings are defined at high energy scales, whereas experimental oscillation data are measured at low energies. Since the parameters of a theory change with the energy scale under consideration (as will be discussed in section 4.1), it is important to consis- tently derive the settings’ low-energy predictions to compare to experimental oscillation data. As already touched upon above, neutrino oscillations are by far not the only avenue towards unravelling the nature of neutrino physics or, even more general, of physics beyond the SM. Since neutrino oscillations have established lepton flavour violation (LFV), New Physics models have a tendency to introduce additional LFV (and sometimes even LNV) physics, pro- viding a rich phenomenology of both charged LFV and LNV processes. 11 To fully exploit the complementarity and constrain the free input parameters of a respective New Physics model, we need to combine the bounds from neutrino oscillation experiments with those derived from the model being sensitive to experimental probes from both indirect and direct searches at different energy scales. For these purposes, the theoretical treatment of relevant (LFV and LNV) processes and the accurate derivation of predictions for the measurable quantities are crucial. These points are, in fact, the motivation for the research projects presented in chapters 5 and 6, on which this thesis is based.
In particular, right-handed neutrinos constitute a com- mon new physics proposal, usually linked to the genera- tion of neutrino masses. This is particularly interesting nowadays, ever since we gathered compelling evidence that neutrinos do have masses, that they lie well below the other fermions’ ones, and that their mixing patterns differ extraordinarily from those of the quark sector (for a review on the matter of neutrino masses see, for exam- ple, ). The most straightforward way to construct a mass term for the neutrinos within the SM is just to rely on the Higgs mechanism, and so to write the corre- sponding Yukawa couplings; for that aim, one needs some fermionic felds which carry no SM charge: right- handed neutrinos. However, we do not know whether neutrinos are Dirac or Majorana.
The study of various symmetries and symmetry breaking effects is always an interesting topic for research in the area of nuclear physics. Such research is potentially important to understand the underlying physics of strong interactions. The charge symmetry is such a symmetry which is broken by small amount at the quark level and consequently it is also broken at the hadronic level ,,. Because of the up (u) and down (d) quarks mass difference (𝑚 − 𝑚 ≠ 0) various neutral
In order to attain the desired energy resolution to disentangle the two mass hierarchies, the JUNO Collaboration paid a particular attention to the photomultiplier system, that consists of 17000 large PMTs, with a diameter of 20 inches, interspersed with 25000 smaller ones, of 3 inches. This large number of PMTs will allow a powerful event reconstruction and will offer an internal cross check, that should help in reducing the non stochastic uncertainty and improving the high precision oscillation parameter measurement. The total coverage is about 80%, corresponding to about 1200 photo-electrons/MeV.
Finally, the model of section 3 predicts the significant extensition of available parameter region consistent with all cosmological and astrophysical constraints. In some range of sterile neutrino masses active-sterile mixing can reach even the direct bounds from current particle physics experiments. Mixing at the level of (8) can also explain small active neutrino masses in the scope of the suggested model. Latter possibility can be tested by presently developing ground-based experiments, see  for details.
Going beyond the standard model of particle physics, we first consider that the neutrinos are Dirac particles which get their tiny mass from a small Yukawa coupling. Upon introducing three right-chiral neutrino fields, in order to fill out the missing components of the neutrino Dirac spinor, the gravitational anomaly in lepton number is vanishing, because the contributions from left- and right-chiral leptons cancel. Nevertheless, gravitational leptogenesis is still a viable explanation of the matter-antimatter asymmetry. Although the growing gravitational wave chirality does not generate a net lepton number, it does generate equal and opposite lepton asymmetries in the active and sterile neutrinos. Since the neutrino Yukawa coupling is extremely tiny, the interactions it mediates are out of equilibrium, and the lepton number carried by the sterile neutrinos is effectively sequestered from the lepton number in the standard model sector. Consequently, the predictions of gravitational leptogenesis are unaffected by the presence of the sterile neutrinos, and the resultant baryon asymmetry FIG. 5. The effect of varying the mass scale of the heavy
Simulations of the formation and evolution of large- scale structure through gravitational collapse provide us with rich predictions for the expected matter dis- tribution within a given cosmology (Evrard et al. 2002; Springel et al. 2005). These predictions include not only first-order features, like the halo mass function n(M,z), but higher-order correlations as well, like the precise way in which galaxy clusters are themselves clustered as a function of mass. Comparisons of these theoretical pre- dictions to the observed Universe provide an excellent op- portunity to test our understanding of cosmology and the formation of large-scale structure. The weak point in this chain is that simulations most reliably predict the dark matter distribution, while observations are most directly sensitive to luminous galaxies and gas. Connections be- tween observable properties and theoretical predictions for dark matter have often been made through simplify- ing assumptions that are hard to justify a priori.
Note that their center of mass is that of the nucleon they originate from, an indispensable feature to allow for structure formation in the universe with light HDM particles which is otherwise not possible . This concept does not only allow for calculating the evolution of the characteristics of the universe but also results in specific predictions of, among others, the masses of the dark matter particles themselves. In addition to this main assumption, the universe is consi- dered flat today with the possibility to vary towards the past and the Hubble constant, as obtained from measurements in the local universe, is taken as an input.
A direct measurement of the neutrinomass via beta decay spectroscopy is also neces- sary for a conclusive interpretation of current and future neutrinoless double beta decay experiments. If the neutrinomass is known, then upper and lower limits can be set on |m ββ | by taking the most extreme values for the Majorana phases. If neutrinoless double beta decay experiments exclude this region, then that would be conclusive evidence that neutrinos are Dirac particles. If neutrinos are indeed Majorana particles and the possible region has not yet been experimentally excluded, then this would guide future neutrinoless double beta decay experiments as to what sensitivity is required to finally settle the issue. As for cosmology, comparison between cosmological and direct measurements of the total neutrinomass would be a significant test of the ΛCDM model. To achieve either of these goals requires that we know the neutrinomass more precisely through direct experiments than the indirect techniques of cosmology and neutrinoless double beta decay. Thus, beta decay spectroscopy measurements of the neutrinomass are a significant physics goal in the next decade.
In this work I make first a short review on the challenges encountered in the computation of the PSF and NME, the two key ingredients in the study of the 0νββ decay mode. Then, I present new constraints of the neutrinomass parameters associated with the "light" and "heavy" neutrino exchange mechanisms of occurrence of the 0νββ decay mode. The NME and PSF for three isotopes, 48 Ca, 76 Ge and 82 S e, are calculated with advanced codes developed by our group, while the most recent
We do not provide here the concrete realisation of the hidden sector but list several requirements which help the reader to formulate such a theory. Firstly, the phase transition should be fast enough. Secondly, it will be more preferably if interactions in the hidden sector are in the weak coupling regime. And finally, the Yukawa term (9) should not destroy the usual oscillation picture, so the rate of sterile neutrino scattering in the hidden sector must be much smaller than Γ A .