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تسجيل مستخدم جديدLimit on a Right-Handed Admixture to the Weak $b to c$ Current from Semileptonic Decays
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Robert Feger
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We determine an upper bound for a possible right-handed $b{to}c$ quark current admixture in semileptonic $bar{B} to X_{c} ell^{-} bar{ u}$ decays from a simulateous fit to moments of the lepton-enery and hadronic-mass distribution measured as a function of the lower limit on the lepton energy, using data measured by the babar detector. The right-handed admixture is parametrized by a new parameter $c_R$ as coefficient of computed moments with right-handed quark current. For the standard model part we use the prediction of the heavy-quark expansion (HQE) up to order $1/m_b^3$ and perturbative corrections and for the right-handed contribution only up to order $1/m_b^2$ and perturbative corrections. We find $cR=0.05asympm{+0.33}{-0.50}$ in agreement with the standard-model prediction of zero. Additionally, we give a contraint on a possible right-handed admixture from exclusive decays, which is with a value of $cR =0.01{pm}0.03$ more restrictive than our value from the inclusive fit. The difference in Vcb between the inclusive and exclusive extraction is only slightly reduced when allowing for a right-handed admixture in the range of $cR=0.01 {pm} 0.03$.
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