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      Perturbative Corrections to \(\Lambda_b \to \Lambda\) Form Factors from QCD Light-Cone Sum Rules

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          Abstract

          We compute radiative corrections to \(\Lambda_b \to \Lambda\) from factors, at next-to-leading logarithmic accuracy, from QCD light-cone sum rules with \(\Lambda_b\)-baryon distribution amplitudes. Employing the diagrammatic approach factorization of the vacuum-to-\(\Lambda_b\)-baryon correlation function is justified at leading power in \(\Lambda/m_b\), with the aid of the method of regions. Hard functions entering the factorization formulae are identical to the corresponding matching coefficients of heavy-to-light currents from QCD onto soft-collinear effective theory. The universal jet function from integrating out the hard-collinear fluctuations exhibits richer structures compared with the one involved in the factorization expressions of the vacuum-to-\(B\)-meson correlation function. Based upon the QCD resummation improved sum rules we observe that the perturbative corrections at \({\cal O}(\alpha_s)\) shift the \(\Lambda_b \to \Lambda\) from factors at large recoil significantly and the dominant contribution originates from the next-to-leading order jet function instead of the hard coefficient functions. Having at hand the sum rule predictions for the \(\Lambda_b \to \Lambda\) from factors we further investigate several decay observables in the electro-weak penguin \(\Lambda_b \to \Lambda \, \ell^{+} \ell^{-}\) transitions in the factorization limit (i.e., ignoring the "non-factorizable" hadronic effects which cannot be expressed in terms of the \(\Lambda_b \to \Lambda\) from factors), including the invariant mass distribution of the lepton pair, the forward-backward asymmetry in the dilepton system and the longitudinal polarization fraction of the leptonic sector.

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          Journal
          10.1007/JHEP02(2016)179
          1511.09036

          High energy & Particle physics
          High energy & Particle physics

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