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in creator/contributor: "Neubert, Matthias"  
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Analysis of Br(anti-B ---> X(s gamma)) at NNLO With a Cut on Photon Energy

Description: By combining a recent estimate of the total {bar B} {yields} X{sub s}{gamma} branching fraction at O({alpha}{sub s}{sup 2}) with a detailed analysis of the effects of a cut E{sub {gamma}} {ge} 1.6 GeV on photon energy, a prediction for the partial {bar B} {yields} X{sub s}{gamma} branching fraction at next-to-next-to-leading order in renormalization-group improved perturbation theory is obtained, in which contributions from all relevant scales are properly factorized. The result Br({bar B} {yie… more
Date: October 1, 2006
Creator: Becher, Thomas & Neubert, Matthias
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Exploring the Weak Phase Gamma in B+- -> pi K Decays

Description: Measurements of the rates for the hadronic decays B{sup {+-}} {r_arrow} {pi}K along with the CP-averaged B{sup {+-}} {r_arrow} {pi}{sup {+-}} {pi}{sup 0} branching ratio can be used to bound and extract the weak phase {gamma} = arg(V{sub ub}*). Using preliminary CLEO data, we obtain the bounds {vert_bar}{gamma}{vert_bar} > 93{degree} at 1 {sigma}, and {vert_bar}{gamma}{vert_bar} > 71{degree} at 90% confidence level.
Date: April 15, 1999
Creator: Neubert, Matthias
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Borel Summation and Momentum-Plane Analyticity in Perturbative QCD

Description: We derive a compact expression for the Borel sum of a QCD amplitude in terms of the inverse Mellin transform of the corresponding Borel function. The result allows us to investigate the momentum-plane analyticity properties of the Borel-summed Green functions in perturbative QCD. An interesting connection between the asymptotic behavior of the Borel transform and the Landau singularities in the momentum plane is established. We consider for illustration the polarization function of massless qua… more
Date: February 5, 1999
Creator: Neubert, Matthias
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

QCD Factorization for B {r_arrow} {pi}{pi} Decays: Strong Phases and CP Violation in the Heavy Quark Limit

Description: We show that, in the heavy quark limit, the hadronic matrix elements that enter B meson decays into two light mesons can be computed from first principles, including ''non-factorizable'' strong interaction corrections, and expressed in terms of form factors and meson light-cone distribution amplitudes. The conventional factorization result follows in the limit when both power corrections in 1/m{sub b} and radiative corrections in {alpha}{sub s} are neglected. We compute the order-{alpha}{sub s}… more
Date: May 14, 1999
Creator: Neubert, Matthias
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

B {r_arrow} X{sub u} {ell} {bar {nu}}{sub {ell}} decay distributions to order {alpha}{sub s}

Description: An analytic result for the O({alpha}{sub s}) corrections to the triple differential B {r_arrow} X{sub u} {ell} {bar {nu}}{sub {ell}} decay rate is presented, to leading order in the heavy-quark expansion. This is relevant for computing partially integrated decay distributions with arbitrary cuts on kinematic variables. Several double and single differential distributions are derived, most of which generalize known results. In particular, an analytic result for the O({alpha}{sub s}) corrections … more
Date: May 17, 1999
Creator: Neubert, Matthias
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Factorization in B ---> V Gamma Decays

Description: The factorization properties of the radiative decays B {yields} V{gamma} are analyzed at leading order in 1/m{sub b} using the soft-collinear effective theory. It is shown that the decay amplitudes can be expressed in terms of a B {yields} V form factor evaluated at q{sup 2} = 0, light-cone distribution amplitudes of the B and V mesons, and calculable hard-scattering kernels. The renormalization-group equations in the effective theory are solved to resum perturbative logarithms of the different… more
Date: March 1, 2005
Creator: Becher, Thomas; Hill, Richard J. & Neubert, Matthias
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Factorization and Momentum-Space Resummation in Deep-Inelastic Scattering

Description: Renormalization-group methods in soft-collinear effective theory are used to perform the resummation of large perturbative logarithms for deep-inelastic scattering in the threshold region x {yields} 1. The factorization theorem for the structure function F{sub 2}(x,Q{sup 2}) for x {yields} 1 is rederived in the effective theory, whereby contributions from the hard scale Q{sup 2} and the jet scale Q{sup 2}(1 - x) are encoded in Wilson coefficients of effective-theory operators. Resummation is ac… more
Date: July 1, 2006
Creator: Becher, Thomas; Neubert, Matthias & Pecjak, Ben D.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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