Manifestation of Nonuniversality of Lepton Interactions in Spontaneously Violated Mirror Symmetry

Data from the LHCb experiments are indicative of a substantial distinction between the B → K (or K*) + e⁺e^? and B → K (or K*) + μ⁺μ^? branching ratios (April 2017). The branching ratio for the e+e? channel is substantially greater than that for the μ⁺μ^? channel, whereas Standard Model (SM) calculations require that they be equal to each other. The above distinction may suggest the existence of a new interaction changing generations and discriminating between leptons that has couplings that are much greater than and are inverse in strength to the SM fermion couplings to the Higgs boson. Under conditions of spontaneously violated mirror symmetry, the coupling of SM particles to the second Higgs scalar that is inevitably present there and which is in principle heavy possesses precisely these properties. An inverse character of this coupling and its strength are not an additional hypothesis but a necessary condition for qualitatively reproducing, in addition, the observed charged-lepton mass hierarchy and the structure of weak lepton mixing—the Pontecorvo–Maki–Nakagawa–Sakata (PMNS) matrix. Within the mirror model being considered, all properties of the new interaction, including its inverse character, are due to the hierarchical character of the quark and charged-lepton mass spectrum.     

Structures of the neutrino mass spectrum and of lepton mixing as results of mirror-symmetry breaking

The mechanism of broken mirror symmetry may be the reason behind the appearance of the observed weak-mixing matrix for leptons that has a structure involving virtually no visible regularities (flavor riddle). Special features of the Standard Model such as the particle-mass hierarchy and the neutrino spectrum deviating from the hierarchy prove here to be necessary conditions for reproducing a structure of this type. The inverse character of the neutrino spectrum and a small value of the mass m ₃ are also mandatory. The smallness of the angle θ ₁₃ is due precisely to the smallness of the mass ratios in the hierarchical lepton spectrum. The emergence of distinctions between the neutrino spectrum and the spectra of other Standard Model fermions is explained. The inverse character of the neutrino spectrum and the observed value of θ ₁₃ make it possible to estimate the absolute values of their masses as m ₁ ≈ m ₂ ≈ 0.05 eV and m ₃ ≈ 0.01 eV.     

The 3-3-1 model with <Emphasis Type="Italic">S</Emphasis><Subscript>4</Subscript> flavor symmetry

We construct a 3-3-1 model based on family symmetry S ₄ responsible for the neutrino and quark masses. The tribimaximal neutrino mixing and the diagonal quark mixing have been obtained. The new lepton charge \(\mathcal{L}\) related to the ordinary lepton charge L and a SU(3) charge by \(L=\frac{2}{\sqrt{3}}T_{8}+\mathcal{L}\) and the lepton parity P _l =(?) ^L known as a residual symmetry of L have been introduced which provide insights in this kind of model. The expected vacuum alignments resulting in potential minimization can origin from appropriate violation terms of S ₄ and \(\mathcal{L}\). The smallness of seesaw contributions can be explained from the existence of such terms too. If P _l is not broken by the vacuum values of the scalar fields, there is no mixing between the exotic and the ordinary quarks at tree level.     

Majorana neutrinos, <Emphasis Type="Italic">CP</Emphasis> violation,neutrinoless double beta and tritium beta decays

If the present or upcoming searches for neutrinoless double beta ((ββ)_0ν) decay give a positive result, the Majorana nature of massive neutrinos will be established. From the determination of the value of the (ββ)_0ν-decay effective Majorana mass parameter (|〈m〉|), it would be possible to obtain information on the type of neutrino mass spectrum. Assuming 3-ν mixing and massive Majorana neutrinos, we discuss the information that a measurement of, or an upper bound on, |〈m〉| can provide on the value of the lightest neutrino mass m₁. With additional data on the neutrino masses obtained in ³H β-decay experiments, it might be possible to establish whether the CP symmetry is violated in the lepton sector. This would require very high precision measurements. If CP invariance holds, the allowed patterns of the relative CP parities of the massive Majorana neutrinos would be determined.     

Charge asymmetry ratio as a probe of quark flavour couplings of resonant particles at the LHC

We show how a precise knowledge of parton distribution functions, in particular those of the u and d quarks, can be used to constrain a certain class of New Physics models in which new heavy charged resonances couple to quarks and leptons. We illustrate the method by considering a left–right symmetric model with a W′ from a SU(2) _R gauge sector produced in quark–antiquark annihilation and decaying into a charged lepton and a heavy Majorana neutrino. We discuss a number of quark and lepton mixing scenarios, and simulate both signals and backgrounds in order to determine the size of the expected charge asymmetry. We show that various quark–W′ mixing scenarios can indeed be constrained by charge asymmetry measurements at the LHC, particularly at \(\sqrt{s}= 14\) TeV.     

Twin-unified <Emphasis Type="Italic">SU</Emphasis>(5) × <Emphasis Type="Italic">SU</Emphasis>(5)′ GUT and phenomenology

In this article, after a short introduction, grand unified SU(5)×SU(5)^′ model augmented by D₂ parity has been discussed. The latter turns out to be important for phenomenology. Specific pattern of the GUT symmetry breaking causes new strong dynamics at low energies. Consequently, the Standard Model leptons, along with right-handed /sterile neutrinos, come out as composite states. Issues of the gauge coupling unification, generation of the charged fermion and neutrino masses will be presented. Also, various phenomenological implications and constraints will be discussed.     

Spontaneous CP violating phase as the phase in PMNS matrix

We study the possibility of identifying the CP violating phases in the PMNS mixing matrix in the lepton sector and also that in the CKM mixing matrix in the quark sector with the phase responsible for the spontaneous CP violation in the Higgs potential, and some implications. Since the phase in the CKM mixing matrix is determined by experimental data, the phase in the lepton sector is also fixed. The mass matrix for neutrinos is constrained, leading to constraints on the Jarlskog CP violating parameter J, and the effective mass 〈m _ββ 〉 for neutrinoless double beta decay. The Yukawa couplings are also constrained. Different ways of identifying the phases have different predictions for \(\mu\to e e\bar{e}\) and \(\tau\to l_{1} l_{2} \bar{l}_{3}\). Future experimental data can be used to distinguish different models.     

Dark matter from the SU(4) model

The left-right symmetric Pati-Salam model of the unification of quarks and leptons is based on the SU(4) and SU(2)×SU(2) symmetry groups. These groups are naturally extended to include the classification of families of quarks and leptons. We assume that the family group (the group which unites the families) is also the SU(4) group. The properties of the fourth generation of fermions are the same as those of the ordinary-matter fermions in the first three generations except for the family charge of the SU(4)_F group: F=(1/3, 1/3, 1/3, ?1), where F=1/3 for fermions of ordinary matter and F=?1 for the fourth-generation fermions. The difference in F does not allow mixing between ordinary and fourth-generation fermions. Because of the conservation of the Fcharge, the creation of baryons and leptons in the process of electroweak baryogenesis must be accompanied by the creation of fermions of the fourth generation. As a result, the excess n _B of baryons over antibaryons leads to the excess n_4ν=N?N? of neutrinos over antineutrinos in the fourth generation with n_4ν=n _B . This massive neutrino may form nonbaryonic dark matter. In principle, the mass density of the fourth neutrino n_4νm _N in the Universe can make the main contribution to dark matter, since the lower bound on the neutrino mass m _N from the data on decay of the Z bosons is m _N <m _Z /2. The straightforward prediction of this model leads to the amount of cold dark matter relative to baryons, which is an order of magnitude higher than allowed by observations. This inconsistency may be avoided by nonconservation of the F charge.     

Measurement of the top quark mass in dileptonic top quark pair decays with √s = 7 TeV ATLAS data

The top quark mass in dileptonic top quark pair decays was measured using 4.7 fb^–1 of √s = 7 TeV proton-proton (pp) collision data recorded by the ATLAS experiment at the LHC in 2011. The event topology is characterized by the presence of two charged leptons, at least two neutrinos and several jets, two of which originate from bottom quarks. Using the template method and the m _?b observable, defined as the average invariant mass of the two charged lepton plus b-jet pairs in each event, the top quark mass is measured to be 173.09 ± 0.64(stat) ± 1.50(syst) GeV. This proceeding is based on a preliminary result, which has been superseded meanwhile.     

Interference effects in nuclear fission

Various interference effects governing the character of angular distributions of binary and ternary nuclear fission products and P-odd, P-even, and T-odd asymmetries in these angular distributions have been studied within the quantum theory of spontaneous and low-energy induced nuclear fission.     

Neutrino Oscillations with Three Active and Three Sterile Neutrinos

This is an extension of estimates of the probability of μ to e neutrino oscillation with one sterile neutrino to three sterile neutrinos, using a 6x6 matrix. Since the mixing angle for only one sterile neutrino has been experimentally determined, we estimate the μ to e neutrino oscillation probability with different mixing angles for two of the sterile neutrinos.     

The discrete family symmetries as the possible solution to the flavour problem

In order to explain the fermions’ masses and mixing parameters appearing in the lepton sector of the Standard Model, one proposes the extension of its symmetry. A discrete, non-Abelian subgroup of U(3) is added to the gauge group SU(3) _C × SU(2) _L × U(1) _Y . Apart from that, one assumes the existence of one extra Higgs doublet. This article focuses mainly on the mathematical theorems and computational techniques which brought us to the results.     

Lithium experiment on solar neutrinos to weight the CNO cycle

The measurement of the flux of beryllium neutrinos with an accuracy of about 10% and CNO neutrinos with an accuracy of 20–30% will enable one to find the flux of pp neutrinos in the source with an accuracy better than 1% using the luminosity constraint. The future experiments on νe^? scattering will enable one to measure with very good accuracy the flux of beryllium and pp neutrinos on the Earth. The ratio of the flux of pp neutrinos on the Earth and in the source will enable one to find with very good accuracy a mixing angle θ_⊙. A lithium detector has high sensitivity to CNO neutrinos and can find the contribution of the CNO cycle to the energy generated in the Sun. This will be a stringent test of the theory of stellar evolution and combined with other experiments will provide a precise determination of the flux of pp neutrinos in the source and a mixing angle θ_⊙. The work on the development of the technology of a lithium experiment is now in progress.     

<Emphasis Type="Italic">T</Emphasis>-odd angular asymmetry in nuclear reactions involving sequential particle emission

A triple T-odd angular correlation is considered in the kinematically similar reactions ¹⁰B(n, αγ) and ²³³U(n, αf) induced by cold polarized neutrons. It is shown that, in the former reaction, this correlation is suppressed by the double parity-conservation selection rule due to the two-step character of the process; however, T invariance does not impose any specific constraints on this correlation. The mechanism through which the T-odd correlation found in ternary-fission reactions is formed seems to be closely related to a nearly simultaneous disintegration of the nucleus involved into two fission fragments and an alpha particle.     

Lepton-number violating decays of heavy mesons

The experimental observation of lepton-number violating processes would unambiguously indicate the Majorana nature of neutrinos. Various ΔL=2 processes for pseudoscalar meson M ₁ decays to another pseudoscalar meson M ₂ and two charged leptons ? ₁, ? ₂ (\(M_{1}^{+}\rightarrow \ell_{1}^{+}\ell_{2}^{+}M_{2}^{-}\)) have been studied extensively. Extending the existing literature on the studies of these kinds of process, we consider the rare decays of heavy mesons to a vector meson or a pseudoscalar meson. These processes have not been searched for experimentally, while they may have sizable decay rates. We calculate their branching fractions and propose to search for these decay modes in the current and forthcoming experiments, in particular at the LHCb.     

Parity-nonconservation effects in the photodisintegration of polarized deuterons

P-odd correlations in deuteron photodisintegration are considered. It is shown that, in the case of unpolarized deuterons, π-meson exchanges do not contribute to these correlations. For polarized deuterons, the contribution of π-meson exchanges to the P-odd correlation is about 0.3×10^?8. The contribution to P-odd effects from weak interactions at short distances substantially exceeds the contribution from π-meson exchanges.     

Light Higgs boson in the two-doublet model featuring explicit <Emphasis Type="Italic">CP</Emphasis> violation

The most general form of an effective two-doublet Higgs potential whose parameters are complex-valued and whose CP invariance is violated explicitly in the minimal supersymmetric model caused by Higgs boson interaction with third-generation squarks is considered. Higgs boson states are obtained and their masses are calculated, along with the decay widths of the lightest Higgs boson and the cross section for its production, in the case of substantial mixing between the CP-even states h and H and the CP-odd state A.     

Multiple exchanges in lepton pair production in high-energy heavy ion collisions

As an archetype reaction for pQCD multigluon hard processes in collisions of ultrarelativistic nuclei, we analyze generic features of lepton pair production via multiphoton processes in peripheral heavy ion scattering. We report explicit results for collisions of two photons from one nucleus with two photons from the other nucleus, 2γ + 2γ → l⁺l^?. The results suggest that the familiar eikonalization of Coulomb distortions breaks down for oppositely moving Coulomb centers. The breaking of eikonalization in QED suggests that multigluon pQCD processes cannot be described in terms of collective nuclear gluon distributions. We discuss a logarithmic enhancement of the contribution from the 2γ + 2γ → l⁺l^? process to production of lepton pairs with large transverse momentum; similar enhancement is absent for the nγ + mγ → l⁺l^? processes with m, n > 2. We comment on the general structure of multiphoton collisions and properties of higher-order terms that cannot be eikonalized.     

Oscillation properties of active and sterile neutrinos and neutrino anomalies at short distances

A generalized phenomenological (3 + 2 + 1) model featuring three active and three sterile neutrinos that is intended for calculating oscillation properties of neutrinos for the case of a normal activeneutrino mass hierarchy and a large splitting between the mass of one sterile neutrino and the masses of the other two sterile neutrinos is considered. A new parametrization and a specific form of the general mixing matrix are proposed for active and sterile neutrinos with allowance for possible CP violation in the lepton sector, and test values are chosen for the neutrino masses and mixing parameters. The probabilities for the transitions between different neutrino flavors are calculated, and graphs representing the probabilities for the disappearance of muon neutrinos/antineutrinos and the appearance of electron neutrinos/antineutrinos in a beam of muon neutrinos/antineutrinos versus the distance from the neutrino source for various values of admissible model parameters at neutrino energies not higher than 50 MeV, as well as versus the ratio of this distance to the neutrino energy, are plotted. It is shown that the short-distance accelerator anomaly in neutrino data (LNSD anomaly) can be explained in the case of a specific mixing matrix for active and sterile neutrinos (which belongs to the a₂ type) at the chosen parameter values. The same applies to the short-distance reactor and gallium anomalies. The theoretical results obtained in the present study can be used to interpret and predict the results of ground-based neutrino experiments aimed at searches for sterile neutrinos, as well as to analyze some astrophysical observational data.     

Compton polarimetry detection of small circularly and linearly polarized impurities in Mössbauer 8.4 keV (3/2-1/2) M1 γ-transition of 169Tm

The arrangement of an experiment to detect the P?odd and P, T?odd polarized part of the Mössbauer (⁺3/2– ⁺1/2) gamma transition of a deformed ¹⁶⁹Tm nucleus with an energy of 8.4 keV by Compton polarimetry is discussed. Tm ₂O₃ single crystal with a quadrupolarly split Mössbauer spectrum is proposed as a resonance polarizer. A Be-scatterer-based Compton polarimeter and a synchronously detecting system will be used to measure the P-odd circular polarization P_Cand P, T-odd linear polarization P_L.The expected accuracy of measuring the relative magnitude of the P, T-odd contribution is about 1% of the magnitude of usual weak nucleon–nucleon interaction.