First-order perturbative and improved leading-logarithmic corrections to the weak decay B -41 are calculated. The color-singlet model for the I + ! J is used and is shown to avoid a previously encountered ambiguity in the leading-logarithm approximation. Overall the corrections reduce the predicted rate to a level consistent with experiment.
We evaluate in closed form the parity-violating one-loop six-point function with external gauge bosons in type-I superstring theory. The amplitude is proven finite for arbitrary internal symmetry. The axial-vector anomaly is obtained for general internal symmetry and is shown to vanish in the case of SO(32).
First-order perturbative and leading-logarithmic QCD corrections to the weak decay B -qcX are calculated. The color-singlet model for the q, is used. Results are similar to the corresponding calculation of B --$X, but are not as sensitive to the value of a,.In an earlier paper1 (designated I in the following), we presented the results of a calculation of QCD corrections to the semi-inclusive decay B -$1 J + unobserved particles.The calculation included both the leading-logarithmic corrections and also the nonleading perturbative contributions. We present here the results of a companion calculation, the QCD corrections to B -q, +anything. The calculations are very similar and the reader should refer to I for details.Our calculations differ from earlier results2 in their treatment of the leading-logarithm approximation. We first project out the color-singlet part of the quark-antiquark (cF) state in our amplitude, and then find the leading-logarithm correction to this amplitude. Kiihn and co-workers2 perform these steps in the reverse order, and obtain rather ambiguous results. The ramifications of our approach are under further investigation.We assume the decay is governed by the quark process b -cFs. In making the change from JlJI to q, production, the only substantive change at the amplitude level is in selecting the pseudoscalar, rather than the vector, portion of the cF states. We use the zero-binding approximation, giving the c and F quarks equal four-momenta p = P,/2. The explicit substitution we use is ( N = 3 = number of colors.) For Ilr(0) we use the same value as for the JIJI, namely (for cr,=0.22),This value includes first-order QCD correction^.^ We use throughout this calculation the same values for the quark masses as in I, even though the 77, mass is somewhat lower than that of the J / + . The calculation proceeds along the same lines as I, and affords an opportunity to check some of the results in that paper. No new problems arise other than the challenge presented by the y-matrix algebra. This was checked by each author. Use of the program REDUCE^ facilitated the calculation.The first-order virtual QCD corrections are divided into the categories of vertex and box diagrams. To this are added the bremsstrahlung contributions. Pauli-Villars ultraviolet regularization was used and infrared singularities were regularized by giving the gluon a small mass A , which ultimately is set to zero. We ignore terms in the amplitude of order q 4 / @ , where m, is any quark mass and M is the mass of the W boson. We do not neglect the strange-quark mass in this calculation. For other details, the reader is referred to I.The analytic results we obtain are rather lengthy and are omitted here. The numerical results, for a, -0.22, are presented in Table I. For comparison purposes we present the first-order QCD corrections T(') divided by the BornAZ is a mixing-angle expression which cancels in the branching ratio.As was the case in the b--JI calculation, the two "crossed" box diagrams are about four times as large (and ...
We consider a mechanism for psi hadroproduction involving the fusion of a gluon from the beam hadron with two gluons from the target or vice versa. The matrix element is obtained by crossing from the charmonium decay amplitude. A model for the joint distribution function of two gluons in a hadron is constructed based on the counting-rule form for the single-gluon distribution function. Particularly strong effects are found in psi production from heavy nuclei, in agreement with recent experimental results. -PSI PRODUCTION THROUGH THREE-GLUON FUSION 613
In the charmonium-based color-singlet model, we consider the contribution to inclusive $ hadroproduction induced by the parton-level subprocess quark +gluon+4+ quark+gluon.
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