Semileptonic Decays of the B[subscript]c Meson in the Quark Meson Effective Theory [microform] PDF Download

Author: Matthew A. (Matthew Alton) Nobes
Publisher: National Library of Canada = Bibliothèque nationale du Canada
ISBN: 9780612514348
Category : Lepton interactions
Languages : en
Pages : 174

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Languages : en
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Languages : en
Pages : 293

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We use the heavy quark effective theory to investigate the form factors that describe the semileptonic decays of a B meson into excited daughter mesons. For an excited daughter meson with charm, a single form factor is needed at leading order, while five form factors and two dimensionful constants are needed to order 1/m(sub)c in the heavy quark expansion. For non-charmed final states, a total of four form factors are needed at leading order. For the process B ->D^(*)Xlv, four form factors are also needed at leading order.

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Category :
Languages : en
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This thesis presents first measurements of moments of the hadronic n_X^2 distribution measured in inclusive semileptonic decays of B mesons to final states containing a charm quark, B->Xc l nu. The variable n_X^2 is a combination of the invariant mass of the charmed meson m_X, its energy in the B-meson rest-frame E_X, and a constant \tilde{\Lambda} = 0.65 GeV, n_X^2 = m_X^2 c^4 - 2 \tilde{\Lambda} E_X + \tilde{\Lambda}^2. The moments n_X^k with k=2,4,6 are measured as proposed by theory to constrain assumptions made in the theoretical description of inclusive observables in semileptonic B-meson decays. This description uses Heavy Quark Expansion (HQE), an effective QCD combined with an Operator Product Expansion. The measurement is based on a sample of 231.6 million e+e- -> Y(4S) -> B\bar{B} events recorded with the BABAR experiment at the PEP-II e+e--storage rings at SLAC. We reconstruct the semileptonic decay by identifying a charged lepton in events tagged by a fully reconstructed hadronic decay of the second B meson. Correction procedures are derived from Monte Carlo simulations to ensure an unbiased measurement of the moments of the n_X^2 distribution. All moments are measured requiring minimum lepton momenta between 0.8 GeV/c and 1.9 GeV/c in the rest frame of the B meson. Performing a simultaneous fit to the measured moments n_X^k up to order k=6 combined with other measurements of moments of the lepton-energy spectrum in decays B->Xc l nu and moments of the photon-energy spectrum in decays B->Xs gamma, we determine the quark-mixing parameter |V_{cb}|, the bottom and charm quark masses, the semileptonic branching fraction BR(B->X l nu), and four non-perturbative heavy quark parameters. Using HQE calculations in the kinetic scheme up to order 1/m_b^3 we find |V_{cb}| = (41.65 +- 0.43 +- 0.40 +- 0.58) x 10^{-3} and m_b = (4.570 \pm 0.033 \pm 0.043)GeV/c^2, where the first uncertainty refe.

Author: Gordon Donald
Publisher:
ISBN:
Category : Fermions
Languages : en
Pages : 135

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Author: Suzanne Lorraine Jones
Publisher:
ISBN:
Category :
Languages : en
Pages : 216

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Author: Emel Gulez
Publisher:
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Category : B mesons
Languages : en
Pages : 116

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Abstract: We present state-of-the-art unquenched lattice QCD results for B meson semileptonic decay, B [rightarrow] [pi]lv, form factors. We use gauge configurations prepared by the MILC collaboration, which include the effects of the sea quarks, the s quark and two very light quarks (u and d). We employ the nonrelativistic NRQCD action to simulate the heavy b quark and a highly improved staggered quark action (AsqTad) to simulate the sea and valence light quarks. To reduce the uncertainties, we perform matching of the heavy-light current with these highly improved actions through one loop. The perturbative matching accounts for the effects of mixing with dimension 4 operators that are O(1/M) and O(a). We extrapolate the form factors f+(q2) and f0(q2) to their values at the physical pion mass using chiral perturbation theory formulas. Integrating this result, we obtain [integral] [from] 16 GeV2 [to] q2_max [d[gamma]/dq2]d2 (V_ub)2 = 1.46(35) ps−1. Combining this with a preliminary average by the Heavy Flavor Averaging Group (HFAG'05) of recent branching fraction data for exclusive B semileptonic decays from the BaBar, Belle and CLEO collaborations, leads to V_ub = 4.22(30)(51) x 10−3.

Author: Krishna Kingkar Pathak
Publisher: LAP Lambert Academic Publishing
ISBN: 9783659622885
Category :
Languages : en
Pages : 120

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The book deals with an introductory idea of Leptonic and semileptonic decay of Heavy-Light mesons. It also highlight the application of a specific QCD potential model in this area of physics. Specifically, it also addresses the application of quantum mechanical perturbation method and explicitly the Dalagarno method of perturbation in this context. The necessity of modification of the model within the constraints of QCD and the model itself is explained and also improved accordingly. Out of the five chapters, the second and third chapters address the leptonic decay of B and D mesons whereas in the last two chapters, the study of semileptonic decay in terms of the universal form factor, Isgur-Wise function is well explained.

Author: Mauricio Garcia-Sciveres
Publisher:
ISBN:
Category :
Languages : en
Pages : 338

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Author: Muneyuki Ishida
Publisher:
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Category :
Languages : en
Pages : 10

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