2,102 research outputs found

    Application of M\"ossbauer-Type Sum Rules for BB Meson Decays

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    Sum rules originally derived for the M\"ossbauer Effect are applied to weak semileptonic B decays. The sum rules follow from assuming that the decay by electroweak boson emission of an unstable nucleus or heavy quark in a bound system is described by a pointlike coupling to a current which acts only on the decaying object, that the Hamiltonian of the bound state depends on the momentum of the decaying object only in the kinetic energy and that the boson has no final state interactions. The decay rate and the first and second moments of the boson energy spectrum for fixed momentum transfer are shown to be the same as for a noninteracting gas of such unstable objects with a momentum distribution the same as that of the bound state. B meson semileptonic decays are shown to be dominated by the lowest-lying states in the charmed meson spectrum.Comment: 9 page

    Duality-Violating 1/m_Q Effects in Heavy Quark Decay

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    I identify a source of \Lambda_{QCD}/m_Q corrections to the assumption of quark-hadron duality in the application of heavy quark methods to inclusive heavy quark decays. These corrections could substantially affect the accuracy of such methods in practical applications and in particular compromise their utility for the extraction of the Cabibbo-Kobayashi-Maskawa matrix element V_{cb}.Comment: 16 pages, 5 figures, an abbreviated version of hep-ph/9809279, the original JLAB-THY-98-03 ``Duality in Inclusive Semileptonic Heavy Quark Decay

    Semileptonic Decay of BB-Meson into DD^{**} and the Bjorken Sum Rule

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    We study the semileptonic branching fraction of BB-meson into higher resonance of charmed meson DD^{**} by using the Bjorken sum rule and the heavy quark effective theory(HQET). This sum rule and the current experiment of BB-meson semileptonic decay into DD and DD^* predict that the branching ratio into DlνlD^{**}l\nu_l is about 1.7\%. This predicted value is larger than the value obtained by the various theoretical hadron models based on the HQET.Comment: 10 pages, LaTex, to be published in Phys. Lett.

    Negative Parity N* Resonances in an Extended GBE

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    In this paper, we calculate the masses and mixing angles of L=1 negative parity N* resonances in an extended GBE (Goldstone-boson-exchange model) with harmonic-oscillator wave functions. By using those mixing angles, we get their photoproduction amplitudes, and compare them with experimental data and the results of OPE (one-pion-exchange model), OPsE (only pseudoscalar meson exchange model), and OGE (one-gluon-exchange model). We find that the extended GBE gives right internal wave functions. It is essential to extend GBE to include not only pseudoscalar meson exchanges but also vector meson exchanges.Comment: 11 pages, no figure, accepted by Nucl. Phys.

    Hadron Electromagnetic Structure: Shedding Light on Models and their Mechanisms

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    Strange quark contributions to the proton magnetic moment are estimated from a consideration of baryon magnetic moment sum rules. The environment sensitivity of quark contributions to baryon moments is emphasized. Pion cloud contributions to proton charge radii are examined in the framework of Chiral Perturbation Theory. The absence of scalar-diquark clustering in the nucleon is discussed.Comment: Lattice '93 presentation. UU-File is a single postscript file of a 3 page manuscript including figures. Ohio State U. PP #93-112

    Meson-like Baryons and the Spin-Orbit Puzzle

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    I describe a special class of meson-like \Lambda_Q excited states and present evidence supporting the similarity of their spin-independent spectra to those of mesons. I then examine spin-dependent forces in these baryons, showing that predicted effects of spin-orbit forces are small for them for the same reason they are small for the analogous mesons: a fortuitous cancellation between large spin-orbit forces due to one-gluon-exchange and equally large inverted spin-orbit forces due to Thomas precession in the confining potential. In addition to eliminating the baryon spin-orbit puzzle in these states, this solution provides a new perspective on spin-orbit forces in all baryons.Comment: 24 pages, 4 figure

    Why N*'s are Important

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    The study of N*'s can provide us with critical insights into the nature of QCD in the confinement domain. The keys to progress in this domain are the identification of its important degrees of freedom and the effective forces between them. I report on the growing evidence in support of the flux tube model, and comment on the connection between this model and spontaneous chiral symmetry breaking, on the spin-dependence of the long-range confining potential, on the evidence for short-range one gluon exchange, on instantons, and on the one pion exchange model.Comment: Overview talk at N*2000, 20 pages, 4 figure

    Electroproduction of K* mesons at CLAS

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    The electroproduction of K0^{*0} mesons using the CLAS detector is described. Data for two electron beam energies, 4.056 and 4.247 GeV, were measured and the normalized yields are compared.Comment: 4 pages, 3 figures, HYP2003 Proceeding

    Hyperfine Mass Splittings of Baryons Containing a Heavy Quark in Large N QCD

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    The hyperfine mass splittings of baryons containing a heavy quark are derived at leading order in large NN QCD. Hyperfine splittings either preserve or violate heavy quark spin symmetry. Previous work proves that the splittings which preserve heavy quark spin symmetry are proportional to J2{\bf J}^2 at order 1/N1/N, where JJ is the angular momentum of the light degrees of freedom of the baryon. This work proves that the splittings which violate heavy quark spin symmetry are proportional to JSQ{\bf J} \cdot {\bf S_Q} at order 1/(NmQ)1/(N m_Q) in the 1/N1/N and 1/mQ1/m_Q expansions.Comment: (8 pages, no figures, uses harvmac), UCSD/PTH 93-2

    Beyond the Adiabatic Approximation: the impact of thresholds on the hadronic spectrum

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    In the adiabatic approximation, most of the effects of quark-antiquark loops on spectroscopy can be absorbed into a static interquark potential. I develop a formalism which can be used to treat the residual nonadiabatic effects associated with the presence of nearby hadronic thresholds for heavy quarks. I then define a potential which includes additional high energy corrections to the adiabatic limit which would be present for finite quark masses. This "improved" potential allows a systematic low energy expansion of the impact of thresholds on hadronic spectra.Comment: 16 pages, a more rapidly converging "improved potential" is define
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