487 research outputs found

    Fit to Moments of Inclusive B->Xc lv and B-> Xs gamma Decay Distributions using Heavy Quark Expansions in the Kinetic Scheme

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    We present a fit to measured moments of inclusive distributions in B->Xc lv and B-> Xs gamma decays to extract values for the CKM matrix element |Vcb|, the b- and c-quark masses, and higher order parameters that appear in the Heavy Quark Expansion. The fit is carried out using theoretical calculations in the kinetic scheme and includes moment measurements of the Babar, Belle, CDF, CLEO and DELPHI collaborations for which correlation matrices have been published. We find |Vcb| = (41.96 +- 0.23(exp) +- 0.35(HQE) +- 0.59(Gamma_SL)) 10^-3 and m_b = 4.590 +- 0.025(exp) +- 0.30(HQE) GeV where errors are experimental and theoretical respectively. We also derive values for the heavy quark distribution function parameters m_b and \mu_\pi^2 in different theoretical schemes that can be used as input for the determination of |Vub|.Comment: 13 pages, 6 figures. v3: Fig 1+2 show absolute values for moments and fit rather than the difference. Updated some references. v2: Updated to include Belle photon moments and PDG 2005 lifetime. Included extrapolation factors for the BR(B->Xs gamma) to 1.6 Gev based on the HQE parameters from the fit and added an updated OPE expression for |Vub

    Signals for Vector Leptoquarks in Hadronic Collisions

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    We analyze systematically the signatures of vector leptoquarks in hadronic collisions. We examine their single and pair productions, as well as their effects on the production of lepton pairs. Our results indicate that a machine like the CERN Large Hadron Collider (LHC) will be able to unravel the existence of vector leptoquarks with masses up to the range of 22--33 TeV.Comment: 15 pages and 5 figures (available upon request or through anonymous ftp), revtex3, IFUSP-P 108

    Introduction to the CMS contribution

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    Leptogenesis with "Fuzzy Mass Shell" for Majorana Neutrinos

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    We study the mixing of elementary and composite particles. In quantum field theory the mixing of composite particles originates in the couplings of the constituent quarks and for neutrinos in self-energy diagrams. In the event that the incoming and outgoing neutrinos have different masses, the self-energy diagrams vanish because energy is not conserved but the finite decaying widths make the mixing possible. We can consider the neutrinos to be "fuzzy" states on their mass shell and the mixing is understood as the overlap of two wavefunctions. These considerations restrict the mass difference to be approximately equal to or smaller than the largest of the two widths: abs(M_i - M_j) lessorequal max(Gamma_i, Gamma_j).Comment: 11 pages, 1 figur

    Single Leptoquark Production at e+ee^+e^- and γγ\gamma\gamma Colliders

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    We consider single production of leptoquarks (LQ's) at e+ee^+e^- and γγ\gamma\gamma colliders, for two values of the centre-of-mass energy, s=500\sqrt{s}=500 GeV and 1 TeV. We find that LQ's which couple within the first generation are observable for LQ masses almost up to the kinematic limit, both at e+ee^+e^- and γγ\gamma\gamma colliders, for the LQ coupling strength equal to αem\alpha_{em}. The cross sections for single production of 2nd2^{nd}- and 3rd3^{rd}-generation LQ's at e+ee^+e^- colliders are too small to be observable. In γγ\gamma\gamma collisions, on the other hand, 2nd2^{nd}-generation LQ's with masses much larger than s/2\sqrt{s}/2 can be detected. However, 3rd3^{rd}-generation LQ's can be seen at γγ\gamma\gamma colliders only for masses at most s/2\sim\sqrt{s}/2, making their observation more probable via the pair production mechanism.Comment: plain TeX, 14 pages, 6 figures (not included but available on request), some minor changes to the text, one reference added, figures and conclusions unchanged, UdeM-LPN-TH-93-152, McGill-93/2

    Signal and Backgrounds for Leptoquarks at the LHC

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    We study the potentiality of the CERN Large Hadron Collider (LHC) to unravel the existence of first generation scalar leptoquarks. Working with the most general SU(2)LU(1)YSU(2)_L \otimes U(1)_Y invariant leptoquark interactions, we analyze in detail the signals and backgrounds that lead to a final state containing a pair e+ee^+e^- and jets. Our results indicate that a machine like the LHC will be able to discover leptoquarks with masses up to 2--3 TeV depending on their couplings.Comment: 37 pages, revtex, uses epsfig.sty (included), 15 figures (included

    Signal and Backgrounds for Leptoquarks at the LHC II: Vector Leptoquarks

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    We perform a detailed analyses of the CERN Large Hadron Collider (LHC) capability to discover first generation vector leptoquarks through their pair production. We study the leptoquark signals and backgrounds that give rise to final states containing a pair e+e- and jets. Our results show that the LHC will be able to discover vector leptoquarks with masses up to 1.3-2.1 TeV depending on their couplings to fermions and gluons.Comment: 18 pages, 3 figures, REVTe

    The Singlet Majoron Model with Hidden Scale Invariance

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    We investigate an extension of the Singlet Majoron Model in which the breaking of dilatation symmetry by the mass parameters of the scalar potential is removed by means of a dilaton field. Starting from the one-loop renormalization group improved potential, we discuss the ground state of the theory. The flat direction in the classical potential is lifted by quantum corrections and the true vacua are found. Studying the finite temperature potential, we analyze the cosmological consequences of a Jordan-Brans-Dicke dilaton and show that the lepton number is spontaneously broken after the electroweak phase transition, thus avoiding any constraint coming from the requirement of the preservation of the baryon asymmetry in the early Universe. We also find that, contrary to the Standard Model case, the dilaton cosmology does not impose any upper bound on the scale of the spontaneous breaking of scale invariance.Comment: 22 pages, SISSA-5/93/A and DFPD/93/TH/0

    Signal and Backgrounds for the Single Production of Scalar and Vector Leptoquarks at the LHC

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    We perform a detailed analysis of the potentiality of the CERN Large Hadron Collider to study the single production of leptoquarks via ppe±qpp \to e^\pm q\to leptoquark e±q\to e^\pm q, with e±e^\pm generated by the splitting of photons radiated by the protons. Working with the most general SU(2)LU(1)YSU(2)_L \otimes U(1)_Y invariant effective lagrangian for scalar and vector leptoquarks, we analyze in detail the leptoquark signals and backgrounds that lead to a final state containing an e±e^\pm and a hard jet with approximately balanced transverse momenta. Our results indicate that the LHC will be able to discover leptoquarks with masses up to 2--3 TeV, depending on their type, for Yukawa couplings of the order of the electromagnetic one.Comment: Revtex, 23 pages, 11 postscript files. Uses axodraw.sty (included) and epsfig.sty. Typos corrected. To be published in Phys. Rev.

    Multilepton Signatures for Leptoquarks

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    The production of third generation leptoquarks can give rise to multilepton events accompanied by jets and missing transverse energy. In this work we study the signals of these leptoquarks at the CERN Large Hadron Collider and compare them with the ones expected in supersymmetric models.Comment: 13 pages, 4 figure
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