arXiv subjects

A. Yu. Smirnov

Publications and source records attributed to A. Yu. Smirnov.

120 records · Page 7Linked to original sources

arXiv1995

Neutrinos and Structure of the Intermediate Mass Scale

Neutrino data lead via the see-saw mechanism to masses of the right handed neutrinos at the intermediate mass scale. Simple formalism is suggested which incorporates the quark - lepton symmetry and allows one to find properties of the intermediate scale (masses and mixing) from neutrino data. Averaged mass scale and the mass hierarchy parameter are introduced and fixed by the data. They determine natural ranges of masses and mixing at the intermediate scale. In particular, scenario which includes the MSW solution of the solar neutrino problem and tau neutrino as the hot component of Dark Matter of the Universe leads to $M_2 = (2 - 4) \cdot 10^{10}$ GeV and $M_3 = (4 - 8) \cdot 10^{12}$ GeV in agreement with the linear mass hierarchy. Strong deviations from the natural ranges imply fine tuning of parameters or/and certain symmetry of the Majorana mass matrix of the right handed neutrinos.

hep-ph↗

arXiv1995

Solar Neutrinos: Expecting 1996

These are remarks (mainly on the solar neutrinos) written in anticipation of 1996 - the year which can be crucial for the neutrino physics. Recent results on solar neutrinos are discussed. The topics include: (solar) model independent approach to the solar neutrino problem, status of different solutions of the problem, standard and non-standard scenarios of the lepton mixing, light singlet fermions and the neutrino phenomenology.

hep-ph↗

arXiv1995

Light Singlet Fermions and Neutrino Physics

The existence of a light singlet fermion mixed with the electron neutrino is hinted by the simultaneous explanation of various neutrino anomalies. We show that supersymmetry can provide a natural framework for the existence and the desired properties of such a fermion. Quasi Goldstone fermions (QGF) of spontaneously broken global symmetries like the Peccei-Quinn symmetry or lepton number can mix properly with the neutrinos provided the presence of the R-parity breaking term $\e LH_2$. The lightness of QGF can be a consequence of non-minimal Kähler potentials like that of no-scale supergravity. In order to keep R-parity, such a sterile component has to be placed in a new singlet superfield with no vacuum expectation value. In the context of the standard seesaw mechanism the lightness of such a singlet can be understood by imposing a $R$-symmetry.

hep-ph↗

arXiv1995

Quasi Goldstone Fermion As a Sterile Neutrino

The existence of sterile neutrino is hinted by simultaneous explanation of diverse neutrino anomalies. We suggest that the quasi Goldstone fermions (QGF) arising in supersymmetric theory as a result of spontaneous breaking of global symmetry like the Peccei-Quinn symmetry or the lepton number symmetry can play a role of the sterile neutrino. The smallness of mass of QGF ($m_S \sim 10^{-3}-10$ eV) can be related to the specific choice of superpotential or Kähler potential (e.g., no-scale kinetic terms for certain superfields). Mixing of QGF with neutrinos implies the $R$-parity violation. It can proceed via the coupling of QGF with the Higgs supermultiplets or directly with the lepton doublet. A model which accounts for the solar and atmospheric anomalies and the dark matter is presented.

hep-ph↗

arXiv1995

Solar Neutrinos and Lepton Mixing

With latest experimental data the solar neutrino problem enters new phase when crucial aspects of the problem can be formulated in an essentially (solar) model independent way. Original neutrino fluxes can be considered as free parameters to be found from the solar neutrino experiments. Resonance flavour conversion gives the best fit of all experimental results. Already existing data allow one to constraint both the neutrino parameters and the original neutrino fluxes. The reconciliation of the solution of the solar neutrino problem with other neutrino mass hints (atmospheric neutrino problem, hot dark matter etc.) may require the existence of new very light singlet fermion. Supersymmetry can provide a framework within which the desired properties of such a light fermion follow naturally. The existence of the fermion can be related to axion physics, mechanism of $μ$-term generation etc..

hep-ph↗

arXiv1995

Models of Light Singlet Fermion and Neutrino Phenomenology

We suggest that a singlet fermion $S$ exists beyond the standard see-saw structure. It mixes with light neutrinos via interactions with the right-handed neutrino components, so that $\n_e \to S$ conversion solves the solar neutrino problem. Supersymmetry endowed with R-symmetry is shown to give a natural framework for existence, mass scale and mixing ($\sin^22þ_{es} \sim (0.1-1.5)\cdot 10^{-2}$) of such a fermion. Models with an approximate horizontal symmetry are constructed, which embed the fermion $S$ and explain simultaneously solar, atmospheric, hot dark matter problems as well as may predict the oscillation $\bar{\n}_\m \to \bar{\n}_e$ in the region of sensitivity of KARMEN and LSND experiments.

hep-ph↗

arXiv1995

Neutrino spin-flip effects in collapsing stars

We study the spin-flavor transitions of neutrinos in the magnetic fields of a collapsing star. For the neutrino mass squared difference (10^{-10} - 10) eV^2 the transitions take place in almost isotopically neutral region of the star, where the effective matter density is suppressed up to 3 - 4 orders of magnitude. This suppression is shown to increase the sensitivity of the neutrino bursts studies to the magnetic moment of neutrino by 1.5 - 2 orders of magnitude, and for realistic magnetic field the observable effects may exist for (2 - 3)10^{-14} Bohr magneton. In the isotopically neutral region the jumps of the effective potential exist which influence the probabilities of transitions. The experimental signatures of the spin-flavor transitions are discussed. In particular, in the case of direct mass hierarchy, the spin-flip effects result in a variety of modifications of the electron antineutrino spectrum. Taking this into account, we estimated the upper bounds on the magnetic moment from the SN1987A data. In the isotopically neutral region the effects of possible twist of the magnetic field on the way of neutrinos can be important, inducing distortion of the neutrino energy spectra and further increasing the sensitivity. However, if the total rotation angle is restricted the absolute change of probabilities is small.

hep-ph↗

arXiv1994

Boron neutrino flux and the MSW solution of the solar neutrino problem

There are large uncertainties in the predictions of the boron neutrino flux from the Sun which cannot be considered as being of purely statistical origin. We treat the magnitude of this flux, $Φ_B$, as a parameter to be found from experiment. The properties of the MSW solution to the solar neutrino problem for different values of $Φ_B$ are studied. Present data give the bounds: $0.38 < Φ_B/ Φ_B^0 < 3.1$ (2$σ$), where $Φ_B^0 \equiv 5.7 \cdot 10^6$ cm$^{-2}$s$^{-1}$ is the flux in the reference SSM. The variations of the flux in this interval enlarge the allowed region of mixing angles: $\sin^2 2θ= 8\cdot 10^{-4} ÷2\cdot 10^{-2}$ (small mixing solutions) and $\sin^2 2θ= 0.2 ÷0.85$ (large mixing solution). If the value of the original boron neutrino flux is about that measured by Kamiokande, a consistent description of the data is achieved for $\sin^2 2θ\sim (0.8 ÷2)\cdot 10^{-3}$ (``very small mixing solution"). The solution is characterized by a strong suppression of the beryllium neutrino line, a weak distortion of the high energy part of the boron neutrino spectrum and a value of the double ratio $(CC/NC)^{exp}/(CC/NC)^{SSM}$ at $E > 5$ MeV close to 1. We comment on the possibility to measure the neutrino parameters and the original boron neutrino flux in future experiments.

hep-ph↗

arXiv1994

Neutrino Masses and $b-τ$ unification in the Supersymmetric Standard Model

There are several indications that the Majorana masses of the right-handed neutrino components, $M_R,$ are at the intermediate scale: $M_R\sim (10^{10}-10^{12})$ GeV or even lighter. The renormalization effects due to large Yukawa couplings of neutrinos from region of momenta $M_R \ltap q \ltap M_G$ are studied in the supersymmetric standard model. It is shown that neutrino renormalization effect can increase the $m_b/m_τ$ ratio up to $(10÷15)\%.$ This strongly disfavours $m_b-m_τ$ unification for low values of $\tanβ< 10$ especially at large values of $α_s.$ Lower bounds on $M_R$ and $\tanβ$ from the $b-τ$ unification condition were found. The implications of the results to the see-saw mechanism of the neutrino mass generation are discussed.

hep-ph↗

arXiv1993

Neutrinoless Double Beta Decay and the Solar Neutrino Problem

The MSW or vacuum oscillation solution of the solar neutrino problem can be reconciled with possible existence of the $(ββ)_{0ν}$ decay with a half-life corresponding to an effective Majorana mass of the electron neutrino $|m_{ee}| \cong (0.1 - 1.0)~$eV. The phenomenological consequences of such a possibility are analyzed and the implications for the mechanisms of neutrino mass generation are considered.

hep-ph↗

arXiv1993

Pontecorvo's Original Oscillations Revisited

We show that a left-handed neutrino $ν_L$ can oscillate into its $CP$- conjugated state $\barν_R$ with maximal amplitude, in direct analogy with $K^0-\bar{K}^0$ oscillations. Peculiarities of such oscillations under different conditions are studied.

hep-ph↗

arXiv1993

Neutrinos with Mixing in Twisting Magnetic Fields

Transitions in a system of neutrinos with vacuum mixing and magnetic moments, propagating in matter and transverse magnetic field, are considered. It is shown that in the realistic case of magnetic field direction varying along the neutrino path qualitatively new phenomena become possible: permutation of neutrino conversion resonances, appearance of resonances in the neutrino-antineutrino ($ν_{lL}\leftrightarrow\barν_{lR}$) transition channels, neutrino-antineutrino resonant conversion, large amplitude $ν_{lL}\leftrightarrow\barν_{lR}$ oscillations, merging of different resonances (triple resonances). Possible phenomenological implications of these effects are briefly discussed.

hep-ph↗