Neutrino quasielastic scattering on nuclear targets Parametrizing transverse enhancement (meson exchange currents)

We present a parametrization of the observed enhancement in the transverse electron quasielastic (QE) response function for nucleons bound in carbon as a function of the square of the four momentum transfer (Q ²) in terms of a correction to the magnetic form factors of bound nucleons. The parametrization should also be applicable to the transverse cross section in neutrino scattering. If the transverse enhancement originates from meson exchange currents (MEC), then it is theoretically expected that any enhancement in the longitudinal or axial contributions is small. We present the predictions of the “Transverse Enhancement” model (which is based on electron scattering data only) for the ν _μ , [`(n)]_m\bar{\nu}_{\mu} differential and total QE cross sections for nucleons bound in carbon. The Q ² dependence of the transverse enhancement is observed to resolve much of the long standing discrepancy in the QE total cross sections and differential distributions between low energy and high energy neutrino experiments on nuclear targets.     

Contributed report: Flavor anarchy for Majorana neutrinos

We argue that neutrino flavor parameters may exhibit features that are very different from those of quarks and charged leptons. Specifically, within the Proggatt-Nielsen (FN) framework, charged fermion parameters depend on the ratio between two scales, while for neutrinos a third scale — that of lepton number breaking — is involved. Consequently, the selection rules for neutrinos may be different. In particular, if the scale of lepton number breaking is similar to the scale of horizontal symmetry breaking, neutrinos may become flavor-blind even if they carry different horizontal charges. This provides an attractive mechanism for neutrino flavor anarchy.     

Deviation from Tetra-Maximal Neutrino Mixing Above the GUT scale

We consider non-renormalizable interaction term as perturbation of the conventional neutrino mass matrix. We assume that the neutrino masses and mixing arise through physics at a scale intermediate between Planck scale and the electroweak breaking scale. We also assume that, just above the electroweak breaking scale, neutrino masses are nearly degenerate and their mixing is tetra-maximal. Quantum gravity (Planck scale effects) lead to an effective SU(2) _L ×U(1) invariant dimension-5 Lagrangian involving neutrino and Higgs fields. On electroweak symmetry breaking, this operator gives rise to correction to the above masses and mixing. These additional term can be consider as a perturbation to the Tetra-maximal mass matrix. The nature of gravitational interaction demands that the element of this perturbation matrix should be independent of flavor indices. We compute the deviation of three neutrino mixing angles due to Planck scale effects. We find that there is no change in θ ₁₃ and θ ₂₃ but change in solar mixing angle θ ₁₂ is suppress by 3.0°.     

Renormalization of seesaw neutrino masses in the standard model with two-Higgs doublets

Using the theoretical ambiguities inherent in the seesaw mechanism, we derive the new analytic expressions for both quadratic and linear seesaw formulae for neutrino masses at low energies, with either up-type quark masses or charged lepton masses. This is possible through full radiative corrections arising out of the renormalizations of the Yukawa couplings, the coefficients of the neutrino-mass-operator in the standard model with two-Higgs doublets, and also the QCD-QED rescaling factors below the top-quark mass scale, at one-loop level. We also investigate numerically the unification of top-b-τ Yukawa couplings at the scale M ₁=0.59×10⁸ GeV for a fixed value of tan β=58.77, and then evaluate the seesaw neutrino masses which are too large in magnitude to be compatible with the presently available solar and atmospheric neutrino oscillation data. However, if we consider a higher but arbitrary value of M ₁=0.59×10¹¹ GeV, the predictions from linear seesaw formulae with charged lepton masses, can accommodate simultaneousely both solar atmospheric neutrino oscillation data.     

Energy and momentum losses in the process of neutrino scattering on plasma electrons in the presence of a magnetic field

The neutrino-electron scattering in a dense degenerate magnetized plasma under the conditions μ ² > 2eB ≫ μE is investigated. The volume density of the neutrino energy and momentum losses due to this process are calculated. The results we have obtained demonstrate that plasma in the presence of an external magnetic field is more transparent for neutrino than for non-magnetized plasma. It is shown that neutrino scattering under conditions considered does not lead to the neutrino force acting on plasma.     

Neutrino Mixing Matrix and Leptogenesis from Quantum Gravity

We consider non renormalization 1/M _x interaction term as a perturbation of the neutrino mass matrix. We find that for the degenerate neutrino mass spectrum. We assume that the neutrino masses and mixing arise through physics at a scale intermediate between Planck Scale and the electroweak scale. We also assume, above the electroweak breaking scale, neutrino masses are nearly degenerate and their mixing is bimaximal. The perturbation generates a non zero value of θ ₁₃, which is within reach of the high performance neutrino factory. In this paper, we find that the non zero value of θ ₁₃ due to Planck scale effects indicates the possibility of CP violation.     

Gemma experiment: Three years of the search for the neutrino magnetic moment

The result of the 3-year neutrino magnetic moment measurement at the Kalinin Nuclear Power Plant (KNPP) with the GEMMA spectrometer is presented. Antineutrino-electron scattering is investigated. A high-purity germanium detector of 1.5 kg placed at a distance of 13.9 m from the 3 GW_th reactor core is exposed to the antineutrino flux of 2.7 × 10¹³ cm⁻² s⁻¹. The scattered electron spectra taken in (5184 + 6798) and (1853 + 1021) h for the reactor ON and OFF periods are compared. The upper limit for the neutrino magnetic moment μ_v < 3.2 × 10⁻¹¹μ _B at 90% CL is derived from the data processing.     

Change of confinement scale in nuclei and the EMC effect

We study a model in which the confinement scale of quarks in a nucleus of massA changes asA ^1/3. This explains theA dependence of structure functions (emc effect) as seen in muon, electron and antineutrino deep inelastic scattering from nuclear targets. We also investigate a prediction of this model—anA dependence of theqcd scale parameter A.     

Isospin breaking in <Emphasis Type="BoldItalic">K</Emphasis><Subscript><Emphasis Type="BoldItalic">l4</Emphasis></Subscript> decays

Data on K _e4 decays allow one to extract experimental information on the elastic π π scattering amplitude near threshold, and to confront the outcome of the analysis with predictions made in the framework of QCD. These predictions concern an isospin symmetric world, while experiments are carried out in the real world, where isospin-breaking effects—generated by electromagnetic interactions and by the mass difference of the up and down quarks—are always present. We discuss the corrections required to account for these, so that a meaningful comparison with the predictions becomes possible. In particular, we note that there is a spectacular isospin-breaking effect in K _e4 decays. Once it is taken into account, the previous discrepancy between NA48/2 data on K _e4 decays and the prediction of π π scattering lengths disappears.     

Dynamic symmetry breaking in kscn: A 39K and 14N NMR study

Abstract

The ³⁹K ½ → ?½ NMR angular rotation patterns in KSCN show no symmetry change on going through T_c . We have directly determined with ¹⁴N NMR the SCN head-tail flipping rate. The results show that the absence of a symmetry change in ³⁹K angular rotation patterns is due to the fact that the time scale for the SCN fluctuations is much longer than the characteristic time scale of this experiment. The same is true for the diffuse neutron scattering data where both above and below T_c the SCN groups appear ordered and static and disorder is restricted to domain boundaries. KSCN thus seems to be the first known example where a structural phase transition can be observed in the slow motion and not in the fast motion regime and where a dynamic breaking of the symmetry of the high temperature phase takes place.     

Quasi-elastic neutrino-nucleus reactions

The quasi-elastic contribution of the nuclear inclusive electron scattering model developed in [A. Gil, J. Nieves, and E. Oset: Nucl. Phys. A 627 (1997) 543] is extended to the study of electroweak charged current induced nuclear reactions at intermediate energies of interest for future neutrino oscillation experiments. The model accounts for long-range nuclear (RPA) correlations, final state interaction and Coulomb corrections. RPA correlations are shown to play a crucial role in the whole range of neutrino energies, up to 500 MeV, studied in this work. Predictions for inclusive muon capture for different nuclei, and for the reactions ¹²C(ν _μ , μ ₋)X and ¹²C(ν _e, e⁻)X near threshold are also given. Presented by M. Valverde at the Workshop on calculation of double-beta-decay matrix elements (MEDEX’05), Corfu, Greece, September 26–29, 2005.     

Magnetic neutrino scattering on atomic electrons revisited

We reexamine the role of electron binding effects in the inelastic neutrino–atom scattering induced by the neutrino magnetic moment. The differential cross section of the process is presented as a sum of the longitudinal and transverse components, according to whether the force that the neutrino magnetic moment exerts on electrons is parallel or perpendicular to momentum transfer. The atomic electrons are treated nonrelativistically. On this basis, the recent theoretical predictions concerning the magnetic neutrino-impact ionization of atoms are critically discussed. Numerical calculations are performed for ionization of a hydrogenlike Ge⁺³¹ ion by neutrino impact.     

Vacuum solutions of neutrino anomalies through a softly broken U(1) symmetry

We discuss an extended model which naturally leads to mass scales and mixing angles relevant for understanding both the solar and atmospheric neutrino anomalies in terms of the vacuum oscillations of the three known neutrinos. The model uses a softly broken –– symmetry and contains a heavy scale GeV. The –– symmetric neutrino masses solve the atmospheric neutrino anomaly while breaking of –– generates the highly suppressed radiative mass scale needed for the vacuum solution of the solar neutrino problem. All the neutrino masses in the model are inversely related to , thus providing seesaw-type of masses without invoking any heavy right-handed neutrinos. The possible embedding of the model into an SU(5) grand unified theory is discussed. Received: 5 August 1999 / Revised version: 18 November 1999 / Published online: 6 April 2000     

Axial mass in quasielastic antineutrino-nucleon scattering accompanied by strange-hyperon production

Reactions of quasielastic Λ-, Σ⁻-, and Σ⁰-hyperon production in antineutrino-nucleon interactions are studied. An axial-mass (M _A ) value that agrees with a fit to all accelerator data on exclusive and inclusive νN and νN reactions was extracted from a global statistical analysis of experimental data on differential and total cross sections for ΔY = 0 and 1 quasielastic reactions of neutrino and antineutrino scattering on various nuclear targets.     

Possible alternatives to tri-bimaximal mixing

Possible alternatives to tri-bimaximal mixing are presented based on other symmetry principles, and their predictions for |U _e3|, sin ² θ ₁₂ and sin ² θ ₂₃ are compared to the present neutrino mixing data. In some cases perturbations are required to give better agreement with the data, and the use of a minimal approach is illustrated. Precise experimental determinations of the mixing parameters will be required to decipher the correct mixing pattern and to pin down the appropriate flavor symmetry.     

General SU(2)L × SU(2)R × U(1)EM Sigma Model with External Sources, Dynamical Breaking and Spontaneous Vacuum Symmetry Breaking

We give a general SU(2) _L × SU(2) _R × U(1) _EM sigma model with external sources, dynamical breaking and spontaneous vacuum symmetry breaking, and present the general formulation of the model. It is found that σ and π⁰ without electric charges have electromagnetic interaction effects coming from their internal structures. A general Lorentz transformation relative to external sources is derived, using the general Lorentz transformation and the four-dimensional current of nuclear matter of the ground state with J _gauge = 0, we give the four-dimensional general relations between the different currents of nuclear matter systems with J _gauge≠ 0 and those with J _gauge = 0. The relation of the density’s coupling with external magnetic field is derived, which conforms well to dense nuclear matter in a strong magnetic field. We show different condensed effects in strong interaction about fermions and antifermions, and give the concrete scalar and pseudoscalar condensed expressions of σ₀ and π₀ bosons. About different dynamical breaking and spontaneous vacuum symmetry breaking, the concrete expressions of different mass spectra are obtained in field theory. This paper acquires the running spontaneous vacuum breaking value σ′₀, and obtains the spontaneous vacuum breaking in terms of the running σ′₀, which make nucleon, σ and π particles gain effective masses. We achieve both the effect of external sources and nonvanishing value of the condensed scalar and pseudoscalar paticles. It is deduced that the masses of nucleons, σ and π generally depend on different external sources. PACA numbers: 24.10.-i, 11.30.Qc     

Phenomenology of asymptotically free theories in deep inelastic scattering: (II). Neutrino scattering

The current neutrino inelastic charged current scattering data are shown to be in reasonable agreement with the predictions of simple four-flavour quark models with parameters determined from electroproduction. The data is consistent with the scale-breaking effects from asymptotic freedom that are included in the calculations. We discuss the uncertainty in the neutrino predictions coming from different parametrizations of electroproduction, the ambiguous extrapolation of the theory to low Q² and the effects of a non-zero value of R = σ_L/σ_T.     

Spin flip of neutrinos with magnetic moment in core-collapse supernova

Neutrinos with magnetic moment experience chirality flips while scattering off charged particles. It is known that if neutrino is a Dirac fermion, then such chirality flips lead to the production of sterile right-handed neutrinos inside the core of a star during the stellar collapse, which may facilitate the supernova explosion and modify the supernova neutrino signal. In the present paper we reexamine the production of right-handed neutrinos during the collapse using a dynamical model of the collapse. We refine the estimates of the values of the Dirac magnetic moment which are necessary to substantially alter the supernova dynamics and neutrno signal. It is argued in particular that Super-Kamiokande will be sensitive at least to μ _{ν Dirac} = 10⁻¹³μ_B in case of a galactic supernova explosion. Also we briefly discuss the case of Majorana neutrino magnetic moment. It is pointed out that in the inner supernova core spin flips may quickly equilibrate electron neutrinos with nonelectron antineutrinos if μ _{ν Majorana} ≳ 10⁻¹²μ_B. This may lead to various consequences for supernova physics.     

The Unified SU(2) × U(1) × U′(1)-models of Electroweak Interaction of Leptons

The possible variants of the unified models of electroweak interaction of leptons in the framework of the broken gauge SU(2) × U(1) × U′(1)-symmetry are constructed. In the first part analysis of SU(2) × U(1) × U′(1)-symmetry breaking by the different combinations of two types of Goldstone-Higgs fields: isodoublet φ and isosinglet Φ complex isovector ξ and Φ φ and ξ is considered. The second part is devoted to the construction of the feasible leptonic models in which the masses of the introduced leptons can be generated by symmetry breaking due to the fields considered in the first part. In the third part acceptability of these models from the point of view of available experimental data of cross-sections of muonic neutrino and antineutrino scattering on electron has been investigated.