240 research outputs found

    Novel sources of Flavor Changed Neutral Currents in the 331RHN331_{RHN} model

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    Sources of Flavor Changed Neutral Currents (FCNC) naturally emerge from a well motivated framework called 3-3-1 with right-handed neutrinos model, 331RHN331_{RHN} for short, mediated by an extra neutral gauge boson Zâ€ČZ^{\prime}. Following previous works we calculate these sources and in addition we derive new ones coming from CP-even and -odd neutral scalars which appear due to their non-diagonal interactions with the physical standard quarks. Furthermore we show that bounds related to the neutral mesons systems KL−KSK_L-K_S and D10−D20D_1^0 - D_2^0 may be significantly strengthened in the presence of these new interactions allowing us to infer stronger constraints on the parameter space of the model.Comment: Published version. 10 pages, 6 figure

    Relativistic Description of Exclusive Semileptonic Decays of Heavy Mesons

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    Using quasipotential approach, we have studied exclusive semileptonic decays of heavy mesons with the account of relativistic effects. Due to more complete relativistic description of the ss quark more precise expressions for semileptonic form factors are obtained. Various differential distributions in exclusive semileptonic decays of heavy mesons are calculated. It is argued that consistent account of relativistic effects and HQET motivated choice of the parameters of quark-antiquark potential allow to get reliable value for the ratio A2(0)/A1(0)A_2(0)/A_1(0) in the D→K∗lÎœlD\to K^*l\nu_l decay as well as the ratio~Γ(D→K∗lÎœl)/Γ(D→KlÎœl)\Gamma(D\to K^*l\nu_l)/\Gamma(D\to Kl\nu_l). All calculated branching ratios are in accord with available experimental data.Comment: 18 pages, LATEX, 2 figures inclosed + 4 Postscript figure

    Left-right symmetry in 5D and neutrino mass in TeV scale gravity models

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    We construct a left-right symmetric model based on the gauge group SU(2)L×SU(2)R×U(1)B−LSU(2)_L\times SU(2)_R\times U(1)_{B-L} in five dimensions where both the gauge bosons and fermions reside in all five dimensions. The orbifold boundary conditions are used not only to break the gauge symmetry down to SU(2)L×U(1)Y×U(1)Yâ€ČSU(2)_L\times U(1)_Y\times U(1)_{Y'} but also to ``project'' the right handed neutrino out of the zero mode part of the spectrum, providing a new way to understand the small neutrino masses without adding (singlet) bulk neutrinos. This formulation of the left-right model has also two new features: (i) it avoids most existing phenomenological bounds on the scale of the right handed WRW_R boson allowing for the possibility that the right handed gauge bosons could have masses under a TeV, and (ii) it predicts a stable lepton with mass of order of the inverse radius of the fifth dimension.Comment: 20 pages; some new materials and references adde

    Leptonic and Semileptonic Decays of Charm and Bottom Hadrons

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    We review the experimental measurements and theoretical descriptions of leptonic and semileptonic decays of particles containing a single heavy quark, either charm or bottom. Measurements of bottom semileptonic decays are used to determine the magnitudes of two fundamental parameters of the standard model, the Cabibbo-Kobayashi-Maskawa matrix elements VcbV_{cb} and VubV_{ub}. These parameters are connected with the physics of quark flavor and mass, and they have important implications for the breakdown of CP symmetry. To extract precise values of ∣Vcb∣|V_{cb}| and ∣Vub∣|V_{ub}| from measurements, however, requires a good understanding of the decay dynamics. Measurements of both charm and bottom decay distributions provide information on the interactions governing these processes. The underlying weak transition in each case is relatively simple, but the strong interactions that bind the quarks into hadrons introduce complications. We also discuss new theoretical approaches, especially heavy-quark effective theory and lattice QCD, which are providing insights and predictions now being tested by experiment. An international effort at many laboratories will rapidly advance knowledge of this physics during the next decade.Comment: This review article will be published in Reviews of Modern Physics in the fall, 1995. This file contains only the abstract and the table of contents. The full 168-page document including 47 figures is available at http://charm.physics.ucsb.edu/papers/slrevtex.p

    Polarization phenomena in open charm photoproduction processes

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    We analyze polarization effects in associative photoproduction of pseudoscalar (Dˉ\bar{D}) charmed mesons in exclusive processes γ+N→Yc+Dˉ\gamma+ N\to Y_c +\bar{D}, Yc=Λc+Y_c=\Lambda_c^+, Σc\Sigma_c. Circularly polarized photons induce nonzero polarization of the YcY_c-hyperon with xx- and zz-components (in the reaction plane) and non vanishing asymmetries Ax{\cal A}_x and Az{\cal A}_z for polarized nucleon target. These polarization observables can be predicted in model-independent way for exclusive Dˉ\bar{D}-production processes in collinear kinematics. The T-even YcY_c-polarization and asymmetries for non-collinear kinematics can be calculated in framework of an effective Lagrangian approach. The depolarization coefficients DabD_{ab}, characterizing the dependence of the YcY_c-polarization on the nucleon polarization are also calculated.Comment: 36 pages 13 figure

    Measurement of the form-factor ratios for D+ --> K* l nu

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    The form factor ratios rv=V(0)/A1(0), r2=A2(0)/A1(0) and r3=A3(0)/A1(0) in the decay D+ --> K* l nu, K* -->K-pi+ have been measured using data from charm hadroproduction experiment E791 at Fermilab. From 3034 (595) signal (background) events in the muon channel, we obtain rv=1.84+-0.11+-0.09, r2=0.75+-0.08+-0.09 and, as a first measurement of r3, we find 0.04+-0.33 +-0.29. The values of the form factor ratios rv and r2 measured for the muon channel are combined with the values of rv and r2 that we have measured in the electron channel. The combined E791 results for the muon and electron channels are rv=1.87+-0.08+-0.07 and r2=0.73+-0.06+-0.08.Comment: 9 pages + 3 figures ; submitted to PL

    Vector meson production and nucleon resonance analysis in a coupled-channel approach for energies m_N < sqrt(s) < 2 GeV I: pion-induced results and hadronic parameters

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    We present a nucleon resonance analysis by simultaneously considering all pion- and photon-induced experimental data on the final states gamma N, pi N, 2 pi N, eta N, K Lambda, K Sigma, and omega N for energies from the nucleon mass up to sqrt(s) = 2 GeV. In this analysis we find strong evidence for the resonances P_{31}(1750), P_{13}(1900), P_{33}(1920), and D_{13}(1950). The omega N production mechanism is dominated by large P_{11}(1710) and P_{13}(1900) contributions. In this first part, we present the results of the pion-induced reactions and the extracted resonance and background properties with emphasis on the difference between global and purely hadronic fits.Comment: 54 pages, 26 figures, discussion extended, typos corrected, references updated, to appear in Phys. Rev.

    The Renormalization Group with Exact beta-Functions

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    The perturbative ÎČ\beta-function is known exactly in a number of supersymmetric theories and in the 't Hooft renormalization scheme in the ϕ44\phi_4^4 model. It is shown how this allows one to compute the effective action exactly for certain background field configurations and to relate bare and renormalized couplings. The relationship between the MS and SUSY subtraction schemes in N=1N = 1 super Yang-Mills theory is discussed

    Heavy quarkonium: progress, puzzles, and opportunities

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    A golden age for heavy quarkonium physics dawned a decade ago, initiated by the confluence of exciting advances in quantum chromodynamics (QCD) and an explosion of related experimental activity. The early years of this period were chronicled in the Quarkonium Working Group (QWG) CERN Yellow Report (YR) in 2004, which presented a comprehensive review of the status of the field at that time and provided specific recommendations for further progress. However, the broad spectrum of subsequent breakthroughs, surprises, and continuing puzzles could only be partially anticipated. Since the release of the YR, the BESII program concluded only to give birth to BESIII; the BB-factories and CLEO-c flourished; quarkonium production and polarization measurements at HERA and the Tevatron matured; and heavy-ion collisions at RHIC have opened a window on the deconfinement regime. All these experiments leave legacies of quality, precision, and unsolved mysteries for quarkonium physics, and therefore beg for continuing investigations. The plethora of newly-found quarkonium-like states unleashed a flood of theoretical investigations into new forms of matter such as quark-gluon hybrids, mesonic molecules, and tetraquarks. Measurements of the spectroscopy, decays, production, and in-medium behavior of c\bar{c}, b\bar{b}, and b\bar{c} bound states have been shown to validate some theoretical approaches to QCD and highlight lack of quantitative success for others. The intriguing details of quarkonium suppression in heavy-ion collisions that have emerged from RHIC have elevated the importance of separating hot- and cold-nuclear-matter effects in quark-gluon plasma studies. This review systematically addresses all these matters and concludes by prioritizing directions for ongoing and future efforts.Comment: 182 pages, 112 figures. Editors: N. Brambilla, S. Eidelman, B. K. Heltsley, R. Vogt. Section Coordinators: G. T. Bodwin, E. Eichten, A. D. Frawley, A. B. Meyer, R. E. Mitchell, V. Papadimitriou, P. Petreczky, A. A. Petrov, P. Robbe, A. Vair
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