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Register a new user1/m_Q Corrections to B -> rho l nu Decay and |V_{ub}|
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In the heavy quark effective field theory of QCD, we analyze the order 1/m_Q contributions to heavy to light vector decays. Light cone sum rule method is applied with including the effects of 1/m_Q order corrections. We then extract |V_{ub}| from B -> rho l nu decay up to order of 1/m_Q corrections.
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B --> rho l nu decay is analyzed in the effective theory of heavy quark with infinite mass limit. The matrix element relevant to the heavy to light vector meson semileptonic decays is parametrized by a set of four heavy flavor-spin independent universal wave functions at the leading order of effective theory. The form factors are calculated at the leading 1/m_Q order using the light cone sum rule method in the framework of effective theory. |V_{ub}| is then extracted via B --> rho l nu decay mode.
Contributions to Bto pi l u decay from 1/m_Q order corrections are analyzed in the heavy quark effective field theory (HQEFT) of QCD. Transition wave functions of 1/m_Q order are calculated through light cone sum rule (LCSR) within the HQEFT framework. The results are compared with those from other approaches.
We revisit the experimental and theoretical status of $B to rho l bar{ u}$ and $B to omega l bar{ u}$ decays. We perform a combined fit of averaged spectra from Belle and Babar measurements with prior light cone sum rule calculations, in order to obtain more precise predictions over the full $q^2$ range. The extracted values of $|V_{ub}|$ from these combined fits exhibit smaller uncertainty compared to previous extractions from $B to rho l bar{ u}$ and $B to omega l bar{ u}$ decays and the central values are found to be smaller than values extracted from $B to pi l u$ or inclusive measurements. We use our fit results to obtain more precise predictions in and beyond the Standard Model for the lepton universality ratios $R(rho)$ and $R(omega)$, as well as several angular observables that are sensitive to the full $q^2$ distribution, such as the longitudinal polarization of the vector meson, the $tau$ polarization, and its forward-backward asymmetry.
We determine the CKM matrix element |Vcb| using a sample of 3.33 million BBbar events in the CLEO detector at CESR. We determine the yield of reconstructed B --> D*+ l nu decays as a function of w = v_B . v_D*, and from this we obtain the differential decay rate dGamma/dw. By extrapolating the differential decay rate to w=1, the kinematic point at which the D* is at rest relative to the B, we extract the product |Vcb| F(1), where F(1) is the form factor at w=1 and is predicted accurately by theory. We find |Vcb| F(1) = 0.0424 +- 0.0018(stat.) +- 0.0019(syst.). We also integrate the differential decay rate over w to obtain B(B --> D*+ l nu) = (5.66 +- 0.29 +- 0.33)%. All results are preliminary.
We investigate $ovar{B^0} to D_s^- pi^+$ decay in perturbative QCD approach which has recently been applied to $B$ meson decays. $ovar{B^0} to D_s^- pi^+$ decay (and its charge conjugated mode) can be one of the hopeful modes to determine $|V_{ub}|$ since it occurs through $b to u$ transition only. We estimate both factorizable and non-factorizable contribution, and show that the non-factorizable contribution is much less than the factorizable one. Our calculation gives ${BR}(ovar{B^0} to D_s^- pi^+) = (50 sim 70) times f_{Ds}^2|{V_{ub}}{V_{cs}}|^2$.
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