16247339
Where do we stand with solar neutrino oscillations
We determine parameters for MSW and vacuum oscillations (active and sterile neutrinos) that are allowed by separate, and collective, imposition of the constraints from total event rates in the chlorine, GALLEX, SAGE, and SuperKamiokande experiments (504 days), the SuperKamiokande energy spectrum, and the SuperKamiokande zenith-angle dependence. The small mixing angle MSW solution is acceptable at 7% C.L. (8% for sterile \ensuremath{\nu}'s) and the vacuum solution is acceptable at 6% C.L. The best-fit global MSW solution for active neutrinos is $\ensuremath{\Delta}{m}^{2}=5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}{\mathrm{eV}}^{2},$ ${\mathrm{sin}}^{2}2\ensuremath{\theta}=5.5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$ (and for sterile neutrinos $\ensuremath{\Delta}{m}^{2}=4\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}{\mathrm{eV}}^{2},$ ${\mathrm{sin}}^{2}2\ensuremath{\theta}=7\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}).$ For vacuum oscillations, the best-fit solution is $\ensuremath{\Delta}{m}^{2}=6.5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}11}{\mathrm{eV}}^{2},$ ${\mathrm{sin}}^{2}2\ensuremath{\theta}=0.75.$ An arbitrary combination of undistorted (no oscillations) $pp,$ ${}^{7}\mathrm{Be},$ ${}^{8}\mathrm{B},$ and CNO neutrino fluxes is inconsistent with the combined data sets at the 3.5\ensuremath{\sigma} C.L., independent of astrophysical considerations. We use improved calculations of solar model fluxes, neutrino absorption cross sections and energy spectra, and a detailed evaluation of regeneration effects.
59164737
Recent developments in neutrino phenomenology
The first phase of studies of the neutrino mass and mixing is essentially over. The outcome is the discovery of non-zero neutrino mass and determination of the dominant structure of the lepton mixing matrix. In some sense this phase was very simple, and nature was very collaborative with us: Two main effects - the vacuum oscillations and the adiabatic conversion in matter (the MSW-effect) - provide complete interpretation of the experimental results. Furthermore, with the present accuracy of measurements the $3\nu-$mixing analysis is essentially reduced to the $2\nu$ consideration. I will present a concise and comprehensive description of this first phase. The topics include: (i) the concept of neutrino mixing in vacuum and matter; (ii) physics of the oscillations and adiabatic conversion; (iii) the experimental evidences of the flavor transformations and determination of the oscillation parameters. Some implications of the obtained results are discussed. Comments are given on the next phase of the field that will be much more involved.
18492548
Pontecorvo's original oscillations revisited
Abstract We show that a left-handed neutrino ν L can oscillate into its CPT -conjugate state ν R with maximal amplitude, in direct analogy with K 0 − K 0 oscillations. Peculiarities of such oscillations under different conditions are studied.
119540272
Self-induced spectral splits in supernova neutrino fluxes
In the dense-neutrino region above the neutrino sphere of a supernova (r < or approx. 400 km), neutrino-neutrino refraction causes collective flavor transformations. They can lead to 'spectral splits' where an energy E{sub split} splits the transformed spectrum sharply into parts of almost pure but different flavors. Unless there is an ordinary MSW resonance in the dense-neutrino region, E{sub split} is determined by flavor-lepton number conservation alone. Spectral splits are created by an adiabatic transition between regions of large and small neutrino density. We solve the equations of motion in the adiabatic limit explicitly and provide analytic expressions for a generic example.
115887973
Solar neutrinos: Theoretical aspects
31519375
Multiple spectral splits of supernova neutrinos.
Collective oscillations of supernova neutrinos swap the spectra f(nu(e))(E) and f(nu[over ](e))(E) with those of another flavor in certain energy intervals bounded by sharp spectral splits. This phenomenon is far more general than previously appreciated: typically one finds one or more swaps and accompanying splits in the nu and nu[over ] channels for both inverted and normal neutrino mass hierarchies. Depending on an instability condition, swaps develop around spectral crossings (energies where f(nu(e))=f(nu(x)), f(nu[over ](e))=f(nu[over ](x)) as well as E-->infinity where all fluxes vanish), and the widths of swaps are determined by the spectra and fluxes. Washout by multiangle decoherence varies across the spectrum and splits can survive as sharp spectral features.
17035129
CHIRAL COLOR SYMMETRY AND POSSIBLE G′-BOSON EFFECTS AT THE TEVATRON AND LHC
A gauge model with chiral color symmetry is considered and possible effects of the color G′-boson octet predicted by this symmetry are investigated in dependence on two free parameters, the mixing angle θG and G′ mass mG′. The allowed region in the mG'–θG plane is found from the Tevatron data on the cross section and forward–backward asymmetry of the production. The mass limits for the G′-boson are shown to be stronger than those for the axigluon. A possible effect of the G′-boson on the production at the LHC is discussed and the mass limits providing for the G′-boson evidence at the LHC are estimated in dependence on θG.
118355424
Chiral color symmetry and $G'$-boson mass limit from Tevatron data on $t \bar t$-production
A gauge model with chiral color symmetry of quarks is considered and possible effects of the color $G'$-boson octet predicted by this symmetry are investigated. The contributions of the $G'$-boson to the cross section $\sigma_{t\bar{t}}$ and to the forward-backward asymmetry $A_{\rm FB}^{p \bar p}$ of $t\bar{t}$ production at the Tevatron are calculated and analysed in dependence on two free parameters of the model, the mixing angle $\theta_G$ and $G'$ mass $m_{G'}$. The $G'$-boson contributions to $\sigma_{t\bar{t}}$ and $A_{\rm FB}^{p \bar p}$ are shown to be consistent with the Tevatron data on $\sigma_{t\bar{t}}$ and $A_{\rm FB}^{p \bar p}$, the allowed region in the $m_{G'} - \theta_G$ plane is discussed and around $m_{G'}=1.2 \, TeV, \; \theta_G=14^\circ $ the region of $1 \sigma$ consistency is found.
123279554
Chiral color quark symmetry and possible constraints on the G′-boson mass from tevatron and LHC data
A gauge model featuring a chiral color symmetry of quarks was considered, and possible manifestations of this symmetry in proton-antiproton and proton-proton collisions at the Tevatron and LHC energies were studied. The cross section $$\sigma _{t\bar t}$$ for the production of $$t\bar t$$ quark pairs at the Tevatron and the forward-backward asymmetry $$A_{FB}^{p\bar p}$$ in this process were calculated and analyzed with allowance for the contributions of the G′-boson predicted by the chiral color symmetry of quarks, the G′-boson massmG′ and the mixing angle θG being treated as free parameters of the model. Limits on mG′ versus θG were studied on the basis of data from the Tevatron on $$\sigma _{t\bar t}$$ and $$A_{FB}^{p\bar p}$$, and the region compatible with these data within one standard deviation was found in the mG′-θG plane. The region ofmG′-mass values that is appropriate for observing the G′-boson at LHC is discussed.
73596822
Transverse laser cooling by synchro-betatron coupling
Transverse laser cooling with the use of a synchrobetatron coupling is being carried out at S-LSR. Bunched 40 keV Mg beams are cooled by a co-propagating laser with a wavelength of 280 nm. Synchrotron oscillation and horizontal betatron oscillation are coupled by an RF drifttube at a finite dispersive section (D = 1.1 m) in order to transmit longitudinal cooling force to the horizontal degree of freedom. The time evolution of horizontal beam size during laser cooling are measured by a CCD camera. The measured beam size after 35 s is reduced to 0.55 mm on the resonance, compared to 0.85 mm measured or larger at non-resonance conditions. Momentum spreads are 1.7 × 10−4 on the resonance otherwise 1.2 × 10−4. These results indicate that the horizontal heat is connected to the longitudinal direction by the synchro-betatron coupling, which is cooled down by a longitudinal bunched beam laser cooling.
122714200
Limits on the scalar-leptoquark and scalar-gluon masses from the parameters S, T, and U in the minimal model based on four-color symmetry
The contributions to the parameters S, T, and U of radiative corrections from the doublets of scalar leptoquarks and scalar gluons are analyzed within the minimal model based on four-color symmetry of the Pati-Salam type. It is shown that current experimental data on the parameters S, T, and U admit the existence of relatively light scalar leptoquarks and scalar gluons (of mass lower than 1 TeV), the best fit to experimental data being attained at mass values not greater than 400 GeV. In particular, the existence of scalar leptoquarks of mass below 300 GeV is found to be compatible with data on the parameters S, T, and U at χ2 < 3.1 (3.2) for mH = 115 (300) GeV as against χSM2 = 3.5 (5.0) in the Standard Model. The mass of the lightest scalar gluon is then predicted to be less than 850 (720) GeV. It is emphasized that the aforementioned doublets of scalar leptoquarks and scalar gluons can play a significant role in processes involving a t quark at LHC.