We show that precision measurement of (1) sum of neutrino masses by cosmological observation and (2) lifetime of neutrinoless double beta decay in ton-scale experiments, with supplementary use of (3) effective mass measured in single beta decay experiment, would allow us to obtain information on the Majorana phase of neutrinos. To quantify the sensitivity to the phase we use the CP exclusion fraction, a fraction of the CP phase parameter space that can be excluded for a given set of assumed input parameters, a global measure for CP violation. We illustrate the sensitivity under varying assumptions, from modest to optimistic ones, on experimental errors and theoretical uncertainty of nuclear matrix elements. Assuming that the latter can be reduced to a factor of ~1.5 we find that one of the two Majorana phases (denoted as alpha_(21)) can be constrained by excluding ~10-40% of the phase space at 2sigma CL even with the modest choice of experimental error for the lowest neutrino mass of 0.1 eV. The characteristic features of the sensitivity to alpha_(21), such as dependences on the true values of alpha_(21), are addressed.
We show that Majorana particles belong to the Wigner class of fermions in which the charge conjugation and the parity operators commute, rather than anticommute. Rigorously speaking, Majorana spinors do not satisfy the Dirac equation [a result originally due to M. Kirchbach, which we re-render here]. Instead, they satisfy a different wave equation, which we derive. This allows us to reconcile Stückelberg-Feynman interpretation with the Majorana construct. We present several new properties of neutral particle spinors and argue that discovery of Majorana particles constitutes dawn of a new era i…
It is well known, that R-parity violating supersymmetric models predict a non-zero magnetic moment for neutrinos. In this work we study the Majorana neutrino transition magnetic moments within an RpV modified minimal supergravity model. Specifically, we discuss the contributions coming from the charged Higgs bosons, higgsinos, leptons, sleptons, charged gauge bosons, and charginos. We use the experimental results from the MUNU collaboration to restrict the model's parameter space. A comparison with two other types of contributions (only trilinear RpV couplings and trilinear plus neutrino--neut…
Inspired by the experimental anomalies in neutrino physics and recent oscillation data from short baseline and another neutrino experiment, the realization of one extra neutrino flavor seem to be favoring. This extra flavor may change the observable, $|m_{ββ}|$ of currently data taking and next-generation $(ββ)_{0ν}$-decay experiments aim to probe and possibly look the Inverted Ordering region($|m_{ββ}| \simeq 10^{-2}$eV) of parameter space. This observation would allow establishing physics beyond the standard model and phenomena like lepton number violation and Majorana nature of neutrino. Th…
Assuming that neutrinos are Majorana particles, in a three generation framework, current and future neutrino oscillation experiments can determine six out of the nine parameters which fully describe the structure of the neutrino mass matrix. We try to clarify the interplay among the remaining parameters, the absolute neutrino mass scale and two CP violating Majorana phases, and how they can be accessed by future neutrinoless double beta ($0νββ$) decay experiments, for the normal as well as for the inverted order of the neutrino mass spectrum. Assuming the oscillation parameters to be in the ra…
We perform an up-to-date global fit of top quark effective theory to experimental data from the Tevatron, and from LHC Runs I and II. Experimental data includes total cross-sections up to 13 TeV, as well as differential distributions, for both single top and pair production. We also include the top quark width, charge asymmetries, and polarisation information from top decay products. We present bounds on the coefficients of dimension six operators, and examine the interplay between inclusive and differential measurements, and Tevatron / LHC data. All results are currently in good agreement wit…
We study the interface effects of quark-hadron mixed phase in compact stars. The properties of nuclear matter are obtained based on the relativistic-mean-field model. For the quark phase, we adopt perturbation model with running quark masses and coupling constant. At certain choices of parameter sets, it is found that varying the quark-hadron interface tension will have sizable effects on the radii ($ΔR \approx 600$ m) and tidal deformabilities ($ΔΛ/Λ\approx 50\%$) of hybrid stars. These provide possibilities for us to constrain the quark-hadron interface tension with future gravitational wave…
In this paper we use solar neutrino data to derive stringent bounds on Majorana neutrino transition moments (TMs). Should such be present, they would contribute to the neutrino--electron scattering cross section and hence alter the signal observed in Super-Kamiokande. Motivated by the growing robustness of the LMA-MSW solution of the solar neutrino problem indicated by recent data, and also by the prospects of its possible confirmation at KamLAND, we assume the validity of this solution, and we constrain neutrino TMs by using the latest global solar neutrino data. We find that all elements of …
We discuss constraints on a scenario of almost degenerate three-flavor neutrinos imposed by the solar and the atmospheric neutrino anomalies, hot dark matter, and neutrinoless double $β$ decays. It is found that in the Majorana version of the model the region with relatively large $θ_{13}$ is favored and a constraint on the CP violating phases is obtained.
The lepton number violating interactions generated by the light Majorana neutrinos can erase the primordial baryon asymmetry of the universe during the electroweak phase transition. The Majorana masses of the left-handed neutrinos are constrained to avoid this problem. These constraints do not depend on the $(B-L)$ symmetry breaking mechanism.
Constraining the Neutrino Mixing Matrix via Single-Sector Charged-Lepton Rotations in the JUNO Precision Era
INFN Sezione di Roma（意大利国家核物理研究所罗马分部）；Instituto de Física Corpuscular (CSIC-Universitat de València)（粒子物理研究所（西班牙高等科研理事会-瓦伦西亚大学））；Departament de Física Teòrica, Universitat de València（瓦伦西亚大学理论物理系）；Dipartimento di Matematica e Fisica, Universitá di Roma Tre（罗马第三大学数学与物理系）
We reexamine big bang nucleosynthesis with large-scale baryon density inhomogeneities when the length scale of the density fluctuations exceeds the neutron diffusion length ($\sim 10^7-10^8$ cm at BBN), and the amplitude of the fluctuations is sufficiently small to prevent gravitational collapse. In this limit, the final light element abundances can be determined by simply mixing the abundances from regions with different baryon/photon ratios without interactions. We examine gaussian, lognormal, and gamma distributions for the baryon/photon ratio, $η$. We find that the deuterium and lithium-7 …
The meV frontier of neutrinoless double beta decay in the JUNO era
INFN Sezione di Roma Tre（罗马第三大学INFN分部）；SISSA/INFN（的里雅斯特国际高等研究学校/意大利国家核物理研究所）；Kavli IPMU (WPI), UTIAS, The University of Tokyo（东京大学 Kavli宇宙粒子与天体物理前沿研究中心（WPI））；Institute of Nuclear Research and Nuclear Energy, Bulgarian Academy of Sciences（保加利亚科学院核研究与核能研究所）
We investigate the observables available in the angular distribution of B to K* mu+ mu- to identify those suitable for measurements in the first few years of LHC data taking. As experimental uncertainties will dominate, we focus on observables that are simple to measure, while maximizing the potential for discovery. There are three observables that may be extracted by counting signal events as a function of one or two decay angles and correspond to large features of the full angular distribution in the Standard Model: Afb, Fl, and S5. Two of these are well known in the experimental community; …
All existing data on neutrino oscillations (including those from the LSND experiment) imply a four neutrino scheme with six different allowed mass patterns. Some of the latter are shown to be disfavored by using a conservative upper bound on the $βbeta 0 ν$ nuclear decay rate, if neutrinos are assumed to be Majorana particles. Comparisons are also made with restrictions from tritium $β$-decay and cosmology.
Large, non-standard neutrino self-interactions have been shown to resolve the $\sim 4σ$ tension in Hubble constant measurements and a milder tension in the amplitude of matter fluctuations. We demonstrate that interactions of the necessary size imply the existence of a force-carrier with a large neutrino coupling ($> 10^{-4}$) and mass in the keV -- 100 MeV range. This mediator is subject to stringent cosmological and laboratory bounds, and we find that nearly all realizations of such a particle are excluded by existing data unless it carries spin 0 and couples almost exclusively to $τ$-flavor…
If the neutrino is Majorana type and the electroweak phase transition is second or weak first order, neutrino-induced interactions together with sphaleron transitions have the potential to erase a previously generated baryon asymmetry of the universe. Taking correctly into account the evolution of the vacuum expectation of the Higgs field the effective light neutrino masses are constrained to be lighter than order 10 MeV, while the effective heavy masses are constrained to be heavier than order 10^7 GeV.
If ultralight $(\ll$ eV), bosonic dark matter couples to right handed neutrinos, active neutrino masses and mixing angles depend on the ambient dark matter density. When the neutrino Majorana mass, induced by the dark matter background, is small compared to the Dirac mass, neutrinos are "pseudo-Dirac" fermions that undergo oscillations between nearly degenerate active and sterile states. We present a complete cosmological history for such a scenario and find severe limits from a variety of terrestrial and cosmological observables. For scalar masses in the "fuzzy" dark matter regime ($\sim 10^{…
I discuss a new Physics scenario, the 331 model, based on the gauge group $SU(3)_c \times SU(3)_L \times U(1)_X$. In particular, I elaborate on correlations between flavour observables in the $B_d$ and $B_s$ systems that can help constraining the model parameters.
We'll review our study of the constraints on the scales in the supersymmetric left-right model (SUSYLR). The conservation of color and electromagnetism in the ground state of the theory implies a relation between right-handed gauge boson mass and soft squark mass. Furthermore, in general for heavy $W_R$, $\tanα$ is larger than one, and the right-handed sneutrino VEV, responsible for spontaneous R-parity breaking, is at most of the order $M_{SUSY}/h_{Δ_R}$, where $M_{SUSY}$ is supersymmetry breaking scale and $h_{Δ_R}$ is the Yukawa coupling in Majorana mass term for right-handed neutrinos.
During a large period of time, the anomalous baryon number violating interactions are in equilibrium, when the $(B+L)$ asymmetry is washed out. If there is any lepton number violation during this period, that will also erase the $(B-L)$ asymmetry. As a result, survival of the baryon asymmetry of the universe pose strong constraints on lepton number violating interactions. We review here the constraints on the left-handed Majorana neutrino masses arising from this survival requirement of the baryon asymmetry of the universe. We then briefly review models of leptogenesis, where lepton number vio…
We revisit the hybrid inflation model gauged by $U(1)_{B-L}$ extension of the Minimal Supersymmetric Standard Model (MSSM) in a no-scale background. Considering a single predictive framework, we study inflation, leptogenesis, gavitino cosmology, and the stochastic background of gravitational waves produced by metastable cosmic strings. The spontaneous breaking of $U(1)_{B-L}$ at the end of inflation produces a network of metastable cosmic strings while, the interaction between $U(1)_{B-L}$ Higgs field and the neutrinos generate heavy Majorana masses for the right-handed neutrinos. The heavy Ma…
In the type-I seesaw mechanism, both the light Majorana neutrinos (ν_1, ν_2, ν_3) and the heavy Majorana neutrinos (N_1, ..., N_n) can mediate the neutrinoless double-beta (0νββ) decay. We point out that the contribution of ν_i to this 0νββprocess is also dependent on the masses M_k and the mixing parameters R_{ek} of N_k as a direct consequence of the exact seesaw relation, and the effective mass term of ν_i is in most cases dominant over that of N_i. We obtain a new bound |\sum R^2_{ek} M_k| < 0.23 eV (or < 0.85 eV as a more conservative limit) at the 2σlevel, which is much stronger than |\s…
We confront the R-parity violating MSSM model with the neutrino oscillation data. Investigating the 1-loop particle-sparticle diagrams with additional bilinear insertions on the external neutrino lines we construct the relevant contributions to the neutrino mass matrix. A comparison of the so-obtained matrices with the experimental ones assuming normal or inverted hierarchy and taking into account possible CP violating phases, allows to set constraints on the values of the bilinear coupling constants. A similar calculation is presented with the input from the Heidelberg-Moscow neutrinoless dou…
We introduce a dimension five CP violating coupling between the Ricci scalar and fermions. This operator splits the energy level between neutrinos and anti-neutrinos and can generate a lepton-asymmetry in the the radiation era if heavy Majorana neutrinos decouple at the GUT scale. This operator can also generate a lepton asymmetry during warm inflation if the light neutrinos have a Majorana mass m_ν\simeq 0.25 eV which is observable in double beta decay experiments.
We use solar neutrino data to derive stringent bounds on Majorana neutrino transition moments (TMs). Such moments, if present, would contribute to the neutrino-electron scattering cross section and hence alter the signal observed in Super-Kamiokande. Using the latest solar neutrino data, combined with the results of the reactor experiment KamLAND, we perform a simultaneous fit of the oscillation parameters and TMs. Furthermore, we include data from the reactor experiments Rovno, TEXONO and MUNU in our analysis, improving significantly the current constraints on TMs. A comparison with previous …
We obtain a relation between right-handed gauge boson mass and soft squark mass in naturally R-parity conserving general supersymmetric left-right models. This relation implies that either ${W_R}$ is lighter than twice the soft squark mass, or a ratio of vacuum expectation values (VEVs) in the model, denoted by $\tanα$, is close to its value of unity in the limit of vanishing D-terms. Generally, we find that for heavy $W_R$ $\tanα$ is larger than one, and that the right-handed sneutrino VEV, responsible for spontaneous R-parity breaking, is at most of the order $M_{SUSY}/h_{Δ_R}$, where $M_{SU…
In the inhomogeneous Universe, the cosmological conversion of dark photons into ordinary photons (and vice versa) may happen at a great number of resonance redshifts. This alters the CMB observed energy spectrum and degree of small-scale anisotropies. We utilize results from the EAGLE simulation to obtain the conversion probability along random line-of-sights to quantify these effects. We then apply our results to the case where dark photons are sourced by dark matter decay and their high-redshift conversion into ordinary photons modify the global 21 cm signal expected from the cosmic dawn era…
The recent IceCube observation of ultra-high-energy astrophysical neutrinos has begun the era of neutrino astronomy. In this work, using the unitarity of leptonic mixing matrix, we derive nontrivial unitarity constraints on the flavor composition of astrophysical neutrinos detected by IceCube. Applying leptonic unitarity triangles, we deduce these unitarity bounds from geometrical conditions, such as triangular inequalities. These new bounds generally hold for three flavor neutrinos, and are independent of any experimental input or the pattern of leptonic mixing. We apply our unitarity bounds …
In this addendum we complement the remarks made in ref[1] constraining the value of the cosmological constant $Λ_4$ in terms of neutrino masses. Those were based on a sharpened version of the Weak Gravity Conjecture as applied to compactifications of the SM to lower dimensions. We argue that the same line of reasoning implies that for fixed values of $Λ_4$ and the Yukawa coupling of the lightest neutrino $Y_{ν_1}$, the EW scale is bounded above. This is a trivial consequence of neutrino masses depending on the Higgs vev. In the case of massive Majorana neutrinos with a see-saw mechanism associ…
Dark matter (DM) direct detection experiments are entering the multiple-ton era and will be sensitive to the coherent elastic neutrino nucleus scattering (CE$ν$NS) of solar neutrinos, enabling the possibility to explore contributions from new physics with light mediators at the low energy range. In this paper we consider light mediator models (scalar, vector and axial vector) and the corresponding contributions to the solar neutrino CE$ν$NS process. Motivated by the current status of new generation of DM direct detection experiments and the future plan, we study the sensitivity of light mediat…
In a recent work, it has been proposed that the recent cosmic passage to a cosmic acceleration era is the result of the existence of small anti-gravity sources in each galaxy and clusters of galaxies. In particular, a swiss-cheese cosmology model which relativistically integrates the contribution of all these anti-gravity sources on galactic scale has been constructed assuming the presence of an infrared fixed point for a scale dependent cosmological constant. The derived cosmological expansion provides explanation for both the fine tuning and the coincidence problem. The present work relaxes …
The precise knowledge of the Standard Model Higgs boson and top quark masses and couplings are crucial to understand the physics beyond it. SM like Higgs boson having mass in the range of 123-127 GeV squeezes the parameters for beyond standard model. In recent LHC era many TeV scale neutrino mass models have earned much attention as they pose many interesting phenomenological aspects. We have contemplated B-L extended models which are theoretically well motivated and phenomenologically interesting, and successfully explain neutrino mass generation. In this article we have analysed the detailed…
Interactions of heavy Majorana neutrinos in the thermal phase of the early universe may be the origin of the cosmological matter-antimatter asymmetry. This mechanism of baryogenesis implies stringent constraints on light and heavy Majorana neutrino masses. We derive an improved upper bound on the CP asymmetry in heavy neutrino decays which, together with the kinetic equations, yields an upper bound on all light neutrino masses of 0.1 eV. Lepton number changing processes at temperatures above the temperature T_B of baryogenesis can erase other, pre-existing contributions to the baryon asymmetry…
We analyze the lepton number violating (LNV) meson decays that arise in a TeV scale Left Right Symmetry model. The right handed Majorana neutrino $N$ along with the right handed or Standard Model gauge bosons mediate the meson decays and provide a resonant enhancement of the rates if the mass of $N$ ($M_N$) lies in the range $\sim (100\, \rm{MeV}-5\, \rm{GeV})$. Using the expected upper limits on the number of events for the LNV decay modes $M_{1}^{+} \to\ell^{+}\ell^{+}π^{-}$~($M_{1}=B, D, D_{s}, K$), we derive constraints plausible on the mass of the right handed charged gauge boson by futur…
We investigate in a model-independent way to what extent one can perturb tri-bimaximal mixing in order to generate a sizable value of |U_{e3}|, while at the same time keeping solar neutrino mixing near its measured value, which is close to sin^2 theta_{12} = 1/3. Three straightforward breaking mechanisms to generate |U_{e3}| of about 0.1 are considered. For charged lepton corrections, the suppression of a sizable contribution to sin^2 theta_{12} can be achieved if CP violation in neutrino oscillations is almost maximal. Generation of the indicated value of |U_{e3}| of about 0.1 through renorma…
We study a type I seesaw model of neutrino masses within the framework of $A_4$ flavor symmetry. Incorporating the presence of both singlet and triplet flavons under $A_4$ symmetry, we construct the leptonic mass matrices involved in type I seesaw mechanism. We then construct the light neutrino mass matrix using the $3σ$ values of neutrino oscillation parameters keeping the presently undetermined parameters namely, the lightest neutrino mass $m_{\text{lightest}}$, one Dirac CP phase $δ$ and two Majorana phases $α, β$ as free parameters. Comparing the mass matrices derived using $A_4$ parameter…
The decays $B_d\toπ^+π^-$ and $B_s\to K^+K^-$ provide an interesting strategy to extract the CKM angle $γ$ at ``second-generation'' $B$-physics experiments of the LHC era. A variant for ``first-generation'' experiments can be obtained, if $B_s\to K^+K^-$ is replaced by $B_d\toπ^\mp K^\pm$. We show that the most recent experimental results for the CP-averaged $B_d\toπ^+π^-$ and $B_d\toπ^\mp K^\pm$ branching ratios imply a rather restricted range for the corresponding penguin parameters, and upper bounds on the direct CP asymmetries $A_{CP}^{dir}(B_d\toπ^+π^-)$ and $A_{CP}^{dir}(B_d\toπ^\mp K^\p…
Two-neutrino double-beta decay of certain nuclear isotopes is one of the rarest Standard Model processes observed in nature. Its neutrinoless counterpart is an exotic lepton-number nonconserving process that is widely searched for to determine if the neutrinos are Majorana fermions. In order to connect the rate of these processes to the Standard Model and beyond the Standard Model interactions, it is essential that the corresponding nuclear matrix elements are constrained reliably from theory. Lattice quantum chromodynamics (LQCD) and low-energy effective field theories (EFTs) are expected to …
We introduce a CP violating coupling between the Ricci curvature and the heavy right handed neutrinos. This splits the Majorana masses of the left and the right handed heavy neutrinos. When the heavy neutrinos decay, their decay rates are different into left and right chirality light neutrinos. A time varying non-zero Ricci curvature can give rise to a net lepton asymmetry. The source of a non-zero curvature in a radiation era is the quantum fluctations of primordial fields.
Here we give a brief review on the current bounds on the general Majorana transition neutrino magnetic moments (TNMM) which cover also the conventional neutrino magnetic moments (NMM). Leptonic CP phases play a key role in constraining TNMMs. While the Borexino experiment is the most sensitive to the TNMM magnitudes, one needs complementary information from reactor and accelerator experiments in order to probe the complex CP phases.
In this paper we study the Lepton Flavor Violating $Z$ boson decays $Z \to τμ$ and $Z \to τe$ in the context of low scale seesaw models with new heavy Majorana neutrinos whose masses could be reachable at the LHC. Our computations of the decay rates are done in the particular realization given by the Inverse Seesaw Model with six extra heavy neutrinos which are quasi-degenerate in three pseudo-Dirac pairs. In particular, we focus on scenarios that are built ad-hoc to produce suppressed rates in all the processes involving $μ$-$e$ transitions, given the fact that these are by far the most stron…
It is known that there are AdS vacua obtained from compactifying the SM to 2 or 3 dimensions. The existence of such vacua depends on the value of neutrino masses through the Casimir effect. Using the Weak Gravity Conjecture, it has been recently argued by Ooguri and Vafa that such vacua are incompatible with the SM embedding into a consistent theory of quantum gravity. We study the limits obtained for both the cosmological constant $Λ_4$ and neutrino masses from the absence of such dangerous 3D and 2D SM AdS vacua. One interesting implication is that $Λ_4$ is bounded to be larger than a scale …
We prove that taking correctly into account the lepton flavour dependence of the CP asymmetries and washout processes, it is possible to obtain successful thermal leptogenesis from the decays of the second right-handed neutrino. The asymmetries in the muon and tau-flavour channels are then not erased by the inverse decays of the lightest right-handed neutrino, N_1. In this way, we reopen the possibility of ``thermal leptogenesis'' in models with a strong hierarchy in the right-handed Majorana masses that is typically the case in models with up-quark--neutrino Yukawa unification.
The thermal history of the universe before the epoch of nucleosynthesis is unknown. The maximum temperature in the radiation-dominated era, which we will refer to as the reheat temperature, may have been as low as 0.7 MeV. In this paper we show that a low reheat temperature has important implications for many topics in cosmology. We show that weakly interacting massive particles (WIMPs) may be produced even if the reheat temperature is much smaller than the freeze-out temperature of the WIMP, and that the dependence of the present abundance on the mass and the annihilation cross section of the…
The question of whether neutrino masses are Dirac or Majorana is one of the most important, and most difficult, questions remaining in the neutrino sector. Searches for neutrinoless double beta-decay may help to resolve this question, but are also sensitive to new, higher dimension Delta L=2 operators. In this paper we place two phenomenological constraints on these operators at dimension d<=11. First, we require that the operators obey the quark flavor symmetries of the Standard Model, with any violation of the symmetries being due to Yukawa interactions, a scheme known as Minimal Flavor Viol…
