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B Meson Semileptonic Form Factors Using Unquenched Lattice QCD

B Meson Semileptonic Form Factors Using Unquenched Lattice QCD
Author: Emel Gulez
Publisher:
Total Pages: 116
Release: 2006
Genre: B mesons
ISBN:
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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.

B Decays

B Decays
Author: Sheldon Stone
Publisher: World Scientific
Total Pages: 676
Release: 1994
Genre: Science
ISBN: 9789810218973
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This 2nd edition is an extensive update of "B Decays?. The revisions are necessary because of the extensive amount of new data and new theoretical ideas. This book reviews what is known about b-quark decays and also looks at what can be learned in the future.The importance of this research area is increasing, as evidenced by the approval of the luminosity upgrade for CESR and the asymmetric B factories at SLAC and KEK, and the possibility of experiments at hadron colliders.The key experimental observations made thus far, measurement of the lifetimes of the different B species, B0-B0 mixing, the discovery of ?Penguin? mediated decays, and the extraction of the CKM matrix elements Vub and Vcb from semileptonic decays, as well as more mundane results, are described in great detail by the experimentalists who have been closely involved with making the measurements. Theoretical progress in understanding b-quark decays using HQET and lattice gauge techniques are described by theorists who have developed and used these techniques.Synthesizing the experimental and theoretical information, several articles discuss the implications for the ?Standard Model? and how further tests can be done using measurements of CP violation in the B system.

Measurement of B -] D* Form Factors in the Semileptonic Decay B -] D* L Nu

Measurement of B -] D* Form Factors in the Semileptonic Decay B -] D* L Nu
Author:
Publisher:
Total Pages:
Release: 2004
Genre:
ISBN:
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The authors present a preliminary measurement of R[sub 1], and R[sub 2], and [rho][sup 2], which are the three parameters used to characterize the B [yields] D*[ell][bar [nu]][sub e] form factors (A[sub 1], V, and A[sub 2]). They use 85 x 10[sup 6] B[bar B]-pairs accumulated on the [Upsilon](4S) resonance at PEP-II. In this analysis they use the decay mode [bar B][sup 0] [yields] D[sup +]*e[sup -][bar [nu]] and its charge conjugate. The D*[sup +] is reconstructed in the channel D*[sup +] [yields] D[sup 0][pi][sup +] and the D[sup 0] in the channel D[sup 0] [yields] K[sup -][pi][sup +]. They parameterize the form factors in terms of their ratios (determined by the parameters R[sub 1] and R[sub 2]) and the common slope [rho][sup 2] in the variable w (a quantity related to the momentum transfer in the decay process). These parameters are determined via an unbinned maximum likelihood fit to the distributions in four kinematic variables (three decay angles and w). The results are R[sub 1] = 1.328 [+-] 0.055 [+-] 0.025 [+-] 0.025 and R[sub 2] = 0.920 [+-] 0.044 [+-] 0.020 [+-] 0.013 for the ratios and [rho][sup 2] = 0.769 [+-] 0.l039 [+-] 0.019 [+-] 0.032 for the slope. The stated errors are the statistical uncertainty from the data, statistical uncertainty from the size of the Monte Carlo sample and the systematic uncertainty, respectively.