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Title: Toward a NNLO calculation of the anti-B ---> X(s) gamma decay rate with a cut on photon energy. II. Two-loop result for the jet function

Abstract

The complete two-loop expression for the jet function J(p{sup 2},{mu}) of soft-collinear effective theory is presented, including non-logarithmic terms. Combined with our previous calculation of the soft function S({omega},{mu}), this result provides the basis for a calculation of the effect of a photon-energy cut in the measurement of the {bar B} {yields} X{sub s}{gamma} decay rate at next-to-next-to-leading order in renormalization-group improved perturbation theory. The jet function is also relevant to the resummation of Sudakov logarithms in other hard QCD processes.

Authors:
; ; ;
Publication Date:
Research Org.:
Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
892345
Report Number(s):
FERMILAB-PUB-06-057-T
Journal ID: ISSN 0370-2693; PYLBAJ; arXiv eprint number hep-ph/0603140; TRN: US0701276
DOE Contract Number:
AC02-76CH03000
Resource Type:
Journal Article
Resource Relation:
Journal Name: Phys.Lett.B637:251-259,2006; Journal Volume: 637
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; DECAY; GAMMA DECAY; PERTURBATION THEORY; PHOTONS; QUANTUM CHROMODYNAMICS; Phenomenology-HEP

Citation Formats

Becher, Thomas, /Fermilab, Neubert, Matthias, and /Cornell U., CIHEP. Toward a NNLO calculation of the anti-B ---> X(s) gamma decay rate with a cut on photon energy. II. Two-loop result for the jet function. United States: N. p., 2006. Web. doi:10.1016/j.physletb.2006.04.046.
Becher, Thomas, /Fermilab, Neubert, Matthias, & /Cornell U., CIHEP. Toward a NNLO calculation of the anti-B ---> X(s) gamma decay rate with a cut on photon energy. II. Two-loop result for the jet function. United States. doi:10.1016/j.physletb.2006.04.046.
Becher, Thomas, /Fermilab, Neubert, Matthias, and /Cornell U., CIHEP. Wed . "Toward a NNLO calculation of the anti-B ---> X(s) gamma decay rate with a cut on photon energy. II. Two-loop result for the jet function". United States. doi:10.1016/j.physletb.2006.04.046. https://www.osti.gov/servlets/purl/892345.
@article{osti_892345,
title = {Toward a NNLO calculation of the anti-B ---> X(s) gamma decay rate with a cut on photon energy. II. Two-loop result for the jet function},
author = {Becher, Thomas and /Fermilab and Neubert, Matthias and /Cornell U., CIHEP},
abstractNote = {The complete two-loop expression for the jet function J(p{sup 2},{mu}) of soft-collinear effective theory is presented, including non-logarithmic terms. Combined with our previous calculation of the soft function S({omega},{mu}), this result provides the basis for a calculation of the effect of a photon-energy cut in the measurement of the {bar B} {yields} X{sub s}{gamma} decay rate at next-to-next-to-leading order in renormalization-group improved perturbation theory. The jet function is also relevant to the resummation of Sudakov logarithms in other hard QCD processes.},
doi = {10.1016/j.physletb.2006.04.046},
journal = {Phys.Lett.B637:251-259,2006},
number = ,
volume = 637,
place = {United States},
year = {Wed Mar 01 00:00:00 EST 2006},
month = {Wed Mar 01 00:00:00 EST 2006}
}
  • 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} {yields} X{sub s}{gamma}) = (2.98 {+-} 0.26) {center_dot} 10{sup -4} is about 1.4{sigma} lower than the experimental world average. This opens a window for significant New Physicsmore » contributions in rare radiative B decays.« less
  • By combining a recent estimate of the total 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}}{>=}1.6 GeV on photon energy, a prediction for the partial 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 factorized. The result B(B{yields}X{sub s}{gamma})=(2.98{+-}0.26)x10{sup -4} is about 1.4{sigma} lower than the experimental world average. This opens a window for significant new physics contributions in rare radiative B decays.
  • We investigate two-loop gluino corrections to the effective Lagrangian for b{yields}s+{gamma}(g) in the minimal supersymmetric extension of the standard model (MSSM) at large tan{beta}, including the contributions in which quark flavor change is mediated by charginos. Using the translation invariance of loop momenta and the Ward-Takahashi identities that are required by the SU(3){sub c}xU(1){sub em} gauge invariance, we simplify our expressions to concise forms. As an example, we discuss two-loop gluino corrections to the CP asymmetry of inclusive B{yields}X{sub s}{gamma} decay in CP violating MSSM.
  • The photon spectrum in B{yields}X{sub s}{gamma} decay, where X{sub s} is any strange hadronic state, is studied using a data sample of 88.5x10{sup 6} e{sup +}e{sup -}{yields}{upsilon}(4S){yields}BB decays collected by the BABAR experiment at the Stanford Linear Accelerator Center. The partial branching fraction, {delta}B(B{yields}X{sub s}{gamma})=(3.67{+-}0.29(stat){+-}0.34(syst){+-}0.29(model))x10{sup -4}, the first moment <E{sub {gamma}}>=2.288{+-}0.025{+-}0.017{+-}0.015 GeV, and the second moment <E{sub {gamma}}{sup 2}>=0.0328{+-}0.0040{+-}0.0023{+-}0.0036 GeV{sup 2} are measured for the photon energy range 1.9 GeV<E{sub {gamma}}<2.7 GeV. They are also measured for narrower E{sub {gamma}} ranges. The moments are then fit to recent theoretical calculations to extract the heavy quark expansion parameters m{sub b} andmore » {mu}{sub {pi}}{sup 2} and to extrapolate the partial branching fraction to E{sub {gamma}}>1.6 GeV. In addition, the direct CP asymmetry A{sub CP}(B{yields}X{sub s+d}{gamma}) is measured to be -0.110{+-}0.115(stat){+-}0.017(syst)« less