219 research outputs found

    Phenomenology of SUSY-models with spontaneously broken R-parity

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    We review the consequences of spontaneously broken R-parity in present and planned lepton-lepton colliders. In the left-right models the R-parity, R=(−1)3(B−L)+2SR=(-1)^{3(B-L)+2S}, is preserved due to the gauge symmetry, but it must be spontaneously broken in order to the scalar spectrum to be physically consistent. The spontaneous breaking is generated via a non-vanishing VEV of at least one of the sneutrinos, which necessarily means non-conservation of lepton number LL. The R-parity violating couplings are parametrized in terms of mixing angles, whose values depend on model parameters. Combined with the constraints derived from low-energy measurements this yields allowed ranges for various R-parity breaking couplings. The R-parity breaking allows for the processes in which a single chargino or neutralino is produced, subsequently decaying at the interaction point to non-supersymmetric particles.Comment: 6 pages, Latex, talk given in Beyond the Standard Model V in Balholm, Norwa

    Effects of degenerate sterile neutrinos on the supernova neutrino flux

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    We consider the possibility that there exist sterile neutrinos which are closely degenerate in mass with the active neutrinos and mixed with them. We investigate the effects of this kind of active-sterile neutrino mixing on the composition of supernova neutrino flux at the Earth. If an adiabatic MSW-transition between active and sterile neutrinos takes place, it could dramatically diminish the electron neutrino flux.Comment: 12 pages. Final version to be published in Phys. Lett.

    Testing neutrino instability with active galactic nuclei

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    Active galactic nuclei and gamma ray bursts at cosmological distances are sources of high-energy electron and muon neutrinos and provide a unique test bench for neutrino instability. The typical lifetime-to-mass ratio one can reach there is τ/m∼500Mpc/cEν∼500\tau/m\sim 500 Mpc/cE_{\nu}\sim 500 s/eV. We study the rapid decay channel νi→νj+ϕ\nu_i\to\nu_j+\phi, where ϕ\phi is a massless or very light scalar (possibly a Goldstone boson), and point out that one can test the coupling strength of gijνiνjg_{ij}\nu_i\nu_j down to g_{ij}\lsim 10^{-8} eV/m by measuring the relative fluxes of νe\nu_{e}, νμ\nu_{\mu} and ντ\nu_{\tau}. This is orders of magnitude more stringent bound than what one can obtain in other phenomena, e.g. in neutrinoless double beta decay with scalar emission.Comment: 3 page

    Vector boson pair production in e-e- collisions with polarized beams

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    The WW-boson pair production in e−e−e^-e^- collisions with polarized beams is investigated. The helicity amplitudes are derived for general couplings and the conditions for a good high-energy behaviour of the cross-section are given. The results are applied to the heavy vector boson production in the context of the left-right symmetric model. The Ward identities and the equivalence theorem are also discussed.Comment: 17 pages+ 8 figures(uuencoded compressed ps-file appended), HU-SEFT R 1994-09 (the original version of the file was unreproducable in some computers

    Supersymmetric Left-Right Model and its Tests in Linear Colliders

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    We investigate phenomenological implications of a supersymmetric left-right model based on SU(2)L×SU(2)R×U(1)B−L SU(2)_L\times SU(2)_R\times U(1)_{B-L}\, gauge symmetry testable in the next generation linear colliders. We concentrate in particular on the doubly charged SU(2)RSU(2)_R triplet higgsino Δ~\tilde\Delta, which we find very suitable for experimental search. We estimate its production rate in e+e−e^+e^-, e−e−e^-e^-, e−γe^-\gamma and γγ\gamma\gamma collisions and consider its subsequent decays. These processes have a clear discovery signature with a very low background from other processes.Comment: 23 pages + 11 pages of figures (available on request), HU-SEFT R 1993-1

    Sterile neutrino signals from supernovae

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    We investigate the effects of a mixing of active and sterile neutrinos on the ratios of supernova electron neutrino flux (FeF_e) and antineutrino flux (FeˉF_{\bar e}) to the total flux of the other neutrino and antineutrino flavours (FaF_a). We assume that the heaviest (in the normal hierarchy) Standard Model neutrino ν3\nu_3 mixes with a sterile neutrino resulting in a pair of mass eigenstates with a small mass gap. Using the density matrix formalism we solve numerically the the evolution of neutrino states in the envelope of a supernova and determine the flux ratios Fe/FaF_e/F_a and Feˉ/FaF_{\bar{e}}/F_a as a function of the active-sterile mixing angle and for the experimentally allowed range of the standard active-active mixing angle θ13\theta_{13}.Comment: 5 pages, 3 figures. This is the corrected version to be published in Physical Review
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