Bremsstrahlung corrections to the decay b→sγb \to s \gamma

We calculate the O($\alpha_s$) gluon Bremsstrahlung corrections to the inclusive decay $b \rightarrow s \gamma$, involving the full operator basis $\hat O_1$ -- $\hat O_8$. Confirming and extending earlier calculations of Ali and Greub, we give formulas for the total decay width as well as the perturbative photon spectrum, regarding the former as a necessary part of the forthcoming complete NLO analysis. We explore in detail the renormalization scale dependence of our results and find it considerably increased.Comment: 23 pages, LaTeX, uses epsf.sty and rotate.sty. 4 figures (uuencoded postscript) appended as seperate file. A complete postscript version may be obtained from URL ftp://feynman.t30.physik.tu-muenchen.de/pub/preprints/tum-93-95.ps.gz Final version as to appear in Physical Review D. Some minor errors corrected, without changes in the numerical results. One reference adde

Two-loop matching of the dipole operators for b→sγb \to s \gamma and b→sgluonb \to s gluon

The order $\alpha_s$ corrections to the Wilson coefficients of the dipole operators ($O_7,O_8$) at the matching scale $\mu =m_W$ are a crucial ingredient for a complete next- to-leading logarithmic calculation of the branching ratio for $b \to s \gamma$. Given the phenomenological relevance and the fact that this two-loop calculation has been done so far only by one group [1], we present a detailed re-calculation using a different method. Our results are in complete agreement with those in ref. [1].Comment: 24 pages, latex, 6 figures include

The Resummed Rate for B -> X_s gamma

In this paper we investigate the effect of the resummation of threshold logs on the rate for B -> X_s gamma. We calculate the differential rate dGamma/dE_gamma including the infinite set of terms of the form alpha_s^n log^{n+1}(1-x) and alpha_s^n log^n(1-x) in the Sudakov exponent. The resummation is potentially important since these logs turn into log(2E_{cut}/m_b), when the rate is integrated from the lower cut x=2E_{cut}/m_b to 1. The resummed rate is then convolved with models for the structure function to study whether or not the logs will be enhanced due to the fermi motion of the heavy quark. A detailed discussion of the accuracy of the calculation with and without the inclusion of the non-perturbative effects dictated by the B meson structure function is given. We also investigate the first moment with respect to (1-x), which can be used to measure \bar\Lambda and lambda_1. It is shown that there are some two loop corrections which are just as large as the alpha_s^2 beta_0 term, which are usually expected to dominate. We conclude that, for the present energy cut, the threshold logs do not form a dominant sub-series and therefore their resummation is unnecessary. Thus, the prospects for predicting the rate for B -> X_s gamma accurately, given the present energy cut, are promising.Comment: 17 pages, 5 figure

B decay shape variables and the precision determination of |Vcb| and mb

We present expressions for shape variables of B decay distributions in several different mass schemes, to order $\alpha_s^2\beta_0$ and (Lambda_{QCD}/mb)^3. Such observables are sensitive to the b quark mass and matrix elements in the heavy quark effective theory, and recent measurements allow precision determinations of some of these parameters. We perform a combined fit to recent experimental results from CLEO, BABAR, and DELPHI, and discuss the theoretical uncertainties due to nonperturbative and perturbative effects. We discuss the possible discrepancy between the OPE prediction, recent BABAR results and the measured branching fraction to D and D* states. We find |Vcb| = (40.8 +- 0.9) x 10^{-3} and mb^{1S} = 4.74 +- 0.10 GeV, where the errors are dominated by experimental uncertainties.Comment: 23 pages, 3 figures, Version to appear in PR

Virtual O(\a_s) corrections to the inclusive decay b→sγb \to s \gamma

We present in detail the calculation of the O(\a_s) virtual corrections to the matrix element for b \to s \g. Besides the one-loop virtual corrections of the electromagnetic and color dipole operators $O_7$ and $O_8$, we include the important two-loop contribution of the four-Fermi operator $O_2$. By applying the Mellin-Barnes representation to certain internal propagators, the result of the two-loop diagrams is obtained analytically as an expansion in $m_c/m_b$. These results are then combined with existing O(\a_s) Bremsstrahlung corrections in order to obtain the inclusive rate for B \to X_s \g. The new contributions drastically reduce the large renormalization scale dependence of the leading logarithmic result. Thus a very precise Standard Model prediction for this inclusive process will become possible once also the corrections to the Wilson coefficients are available.Comment: 29 pages, uses epsfig.sty, 12 postscript figures include

A connection between inclusive semileptonic decays of bound and free heavy quarks

A relativistic constituent quark model, formulated on the light-front, is used to derive a new parton approximation for the inclusive semileptonic decay width of the B-meson. A simple connection between the decay rate of a free heavy-quark and the one of a heavy-quark bound in a meson or in a baryon is established. The main features of the new approach are the treatment of the b-quark as an on-mass-shell particle and the inclusion of the effects arising from the b-quark transverse motion in the B-meson. In a way conceptually similar to the deep-inelastic scattering case, the B-meson inclusive width is expressed as the integral of the free b-quark partial width multiplied by a bound-state factor related to the b-quark distribution function in the B-meson. The non-perturbative meson structure is described through various quark-model wave functions, constructed via the Hamiltonian light-front formalism using as input both relativized and non-relativistic potential models. A link between spectroscopic quark models and the B-meson decay physics is obtained in this way. Our predictions for the B -> X_c l nu_l and B -> X_u l nu_l decays are used to extract the CKM parameters |V_cb| and |V_ub| from available inclusive data. After averaging over the various quark models adopted and including leading-order perturbative QCD corrections, we obtain |V_cb| = (43.0 +/- 0.7_exp +/- 1.8_th) 10^-3 and |V_ub| = (3.83 +/- 0.48_exp +/- 0.14_th) 10^-3, implying |V_ub / V_cb| = 0.089 +/- 0.011_exp +/- 0.005_th, in nice agreement with existing predictions.Comment: revised version with pQCD corrections included, to appear in Physical Review

Nonresonant Semileptonic Heavy Quark Decay

In both the large N_c limit and the valence quark model, semileptonic decays are dominated by resonant final states. Using Bjorken's sum rule in an "unquenched" version of the quark model, I demonstrate that in the heavy quark limit nonresonant final states should also be produced at a significant rate. By calculating the individual strengths of a large number of exclusive two-body nonresonant channels, I show that the total rate for such processes is highly fragmented. I also describe some very substantial duality-violating suppression factors which reduce the inclusive nonresonant rate to a few percent of the total semileptonic rate for the finite quark masses of B decay, and comment on the importance of nonresonant decays as testing grounds for very basic ideas on the structure, strength, and significance of the quark-antiquark sea and on quark-hadron duality in QCD.Comment: 51 pages, 2 Postscript figure

Comparison of the beef empire days index with carcass pricing for ranking beef carcasses

Our study evaluated the effectiveness of the Beef Empire Days carcass index in ranking beef carcasses compared to rankings based on carcass prices. Two price sets were used: the average prices between January 1998 and June 2001, and a short-range price determined from the average prices between April and September of 2001. Additionally, carcass data from the top live-placing cattle were compared to the data of the highest indexing carcasses. The live show judges were very accurate in selecting for ribeye size. However, they selected cattle that were fatter, but did not marble as well as the high indexing carcasses. Changes that might improve the index are identified. However, the Beef Empire Days index ranked carcasses moderately well compared to the pricing system

Effects of Trenbolone Acetate and Zeranol implants on performance, carcass, and meat traits of young bulls and steers

Implanting young bulls and steers with trenbolone acetate and zeranol (Ralgro ®) resulted in increased slaughter weights and carcasses that tended to have more marbling than those of control bulls. Furthermore, steaks from both implanted bulls and implanted steers tended to have less detectable connective tissue. Control bulls had larger scrotal circumferences and heavier testicle weights than implanted bulls. Other secondary sex characteristics were not affected, but in these bulls slaughtered at an average age of 13.6 months, sexual development was minimal. Implanting steers with trenbolone acetate and zeranol resulted in performance and carcass and meat quality slightly superior to control bulls