662 research outputs found

    Probing neutrino mass with multilepton production at the Tevatron in the simplest R-parity violation model

    Get PDF
    We analyze the production of multileptons in the simplest supergravity model with bilinear violation of R parity at the Fermilab Tevatron. Despite the small R-parity violating couplings needed to generate the neutrino masses indicated by current atmospheric neutrino data, the lightest supersymmetric particle is unstable and can decay inside the detector. This leads to a phenomenology quite distinct from that of the R-parity conserving scenario. We quantify by how much the supersymmetric multilepton signals differ from the R-parity conserving expectations, displaying our results in the m0m1/2m_0 \otimes m_{1/2} plane. We show that the presence of bilinear R-parity violating interactions enhances the supersymmetric multilepton signals over most of the parameter space, specially at moderate and large m0m_0.Comment: 26 pages, 23 figures. Revised version with some results corrected and references added. Conclusions remain the sam

    On Forward J/\psi Production at Fermilab Tevatron

    Full text link
    The D0 Collaboration has recently reported the measurement of J/\psi production at low angle. We show here that the inclusion of color octet contributions in any framework is able to reproduce this data.Comment: 1 page, Revtex, uses epsfig.sty, 2 postscript figure

    Comment on DsDsπ0D_s^* \to D_s \pi^0 Decay

    Full text link
    We calculate the rate for DsDsπ0D_s^* \rightarrow D_s \pi^0 decay using Chiral Perturbation Theory. This isospin violating process results from π0\pi^0 - η\eta mixing, and its amplitude is proportional to (mdmu)/(ms(mu+md)/2)(m_d - m_u)/\bigl(m_s-(m_u+m_d)/2 \bigr). Experimental information on the branching ratio for DsDsπ0D_s^* \rightarrow D_s \pi^0 can provide insight into the pattern of SU(3)SU(3) violation in radiative DD^* decays.Comment: 7 pages with 2 figures not included but available upon request, CALT-68-191

    Testing Color Evaporation in Photon-Photon Production of J/Psi at CERN LEP II

    Full text link
    The DELPHI Collaboration has recently reported the measurement of J/Psi production in photon-photon collisions at LEP II. These newly available data provide an additional proof of the importance of colored c bar{c} pairs for the production of charmonium because these data can only be explained by considering resolved photon processes. We show here that the inclusion of color octet contributions to the J/Psi production in the framework of the color evaporation model is able to reproduce this data. In particular, the transverse-momentum distribution of the J/Psi mesons is well described by this model.Comment: 10 pages, 5 Figures, Revtex

    Soft Color Enhancement of the Production of J/psi's by Neutrinos

    Get PDF
    We calculate the production of J/psi mesons by neutrino-nucleon collisions in fixed target experiments. Soft color, often referred to as color evaporation effects, enhance production cross sections due to the contribution of color octet states. Though still small, J/\psi production may be observable in present and future experiments like NuTeV and muon colliders.Comment: 7 pages, Revtex, 4 postscript figures, uses epsfig.st

    Open Heavy Flavor Production in QCD -- Conceptual Framework and Implementation Issues

    Full text link
    Heavy flavor production is an important QCD process both in its own right and as a key component of precision global QCD analysis. Apparent disagreements between fixed-flavor scheme calculations of b-production rate with experimental measurements in hadro-, lepto-, and photo-production provide new impetus to a thorough examination of the theory and phenomenology of this process. We review existing methods of calculation, and place them in the context of the general PQCD framework of Collins. A distinction is drawn between scheme dependence and implementation issues related to quark mass effects near threshold. We point out a so far overlooked kinematic constraint on the threshold behavior, which greatly simplifies the variable flavor number scheme. It obviates the need for the elaborate existing prescriptions, and leads to robust predictions. It can facilitate the study of current issues on heavy flavor production as well as precision global QCD analysis.Comment: 13 pages, 10 figures, Proceedings of Ringberg Workshop: New Trends in HERA Physics 2001, Munich, German

    Decay constants, semi-leptonic and non-leptonic decays in a Bethe-Salpeter Model

    Full text link
    We evaluate the decay constants for the B and DD mesons and the form factors for the semileptonic decays of the B meson to DD and DD^* mesons in a Bethe-Salpeter model. From data we extract Vcb=0.039±0.002V_{cb}=0.039 \pm 0.002 from BˉDlνˉ{\bar B} \to D^* l {\bar{\nu}} and Vcb=0.037±0.004V_{cb}=0.037 \pm 0.004 from BˉDlνˉ{\bar B} \to D l {\bar{\nu}} decays. The form factors are then used to obtain non-leptonic decay partial widths for BDπ(K) B\to D \pi (K) and BDD(Ds)B \to D D (D_s) in the factorization approximation.Comment: 15 Pages, 3 Postscript figures (available also from [email protected]

    Phase separation transition in liquids and polymers induced by electric field gradients

    Full text link
    Spatially uniform electric fields have been used to induce instabilities in liquids and polymers, and to orient and deform ordered phases of block-copolymers. Here we discuss the demixing phase transition occurring in liquid mixtures when they are subject to spatially nonuniform fields. Above the critical value of potential, a phase-separation transition occurs, and two coexisting phases appear separated by a sharp interface. Analytical and numerical composition profiles are given, and the interface location as a function of charge or voltage is found. The possible influence of demixing on the stability of suspensions and on inter-colloid interaction is discussed.Comment: 7 pages, 3 figures. Special issue of the J. Phys. Soc. Ja
    corecore