117975255
QCD factorization for $\Lambda_b^0\to\Lambda_c^+\pi^-$
We prove that in the limit $m_b, m_c\to\infty$ with $m_c/m_b$ fixed, factorization holds at order $\alpha_s$ for the decay $\Lambda_b^0\to\Lambda_c^+\pi^-$. This proof is done in the infinite-momentum frame in which the momenta of $\pi$, $\Lambda_c$, and $\Lambda_b$ go to infinity. Our result is renormalization scale and scheme independent at $\mathcal{O}(\alpha_s)$. This is the same as QCD factorization for $B \to D \pi$.
1562870
Weak semileptonic decays of heavy baryons containing two heavy quarks
In the heavy quark limit a heavy baryon which contains two heavy quarks is believed to be composed of a heavy diquark and a light quark. Based on this picture, we evaluate the weak semileptonic decay rates of such baryons. The transition form factors between two heavy baryons are associated with those between two heavy mesons by applying superflavor symmetry. The effective vertices of the W boson and two heavy diquarks are obtained in terms of the Bethe-Salpeter equation. Numerical predictions on these semileptonic decay widths are presented and they will be tested in future experiments. [S0556-2821(98)00721-8].
120908811
Mass spectra of doubly heavy mesons in Regge phenomenology
In Regge phenomenology, we first study the spectra of charmonium and bottomonium in the (n, M-2) plane and predict masses of some charmonium and bottomonium states which have not been observed now. Then, with the aid of the additivity of intercepts and inverse slopes, we calculate the masses of ground S-wave and P-wave c (b) over bar meson states and their first radial excited states. The predictions are in reasonable agreement with the existing experimental data and those suggested in many other approaches. The predictions may be useful for the discovery of the unobserved c (c) over bar, b (b) over bar, c (b) over bar mesons and the J(P) assignment of these states.
123500440
Solution of the Schwinger-Dyson Equation Involving the Gluon condensate Kernel*
The form of the quantum chromodynamic Schwinger-Dyson (SD) equation modified by the nonperturbative kernel associated with the gluon condensate is obtained. It is shown that the solution for the renormalization group invariant quark condensate from the SD equation is in agreement with that obtained from the consistent equation for quark condensate when the leading behavior of the dynamical quark mass is concerned. It is also found that the gluon condensate kernel makes the critical coupling constant above which the chiral symmetry breaks smaller and increases the value of the quark condensate.
119535783
A dynamical mechanism for the hairpin diagram
SummaryBased on the nonvalence quark-antiquark and gluon constituent structure of mesons we give a reasonable dynamical mechanism which can induce the hairpin diagram without violating the well-observed OZI rule. We calculate the hairpin amplitudes of
$$D^0 \to \overline K ^0 \eta $$
 and
$$\overline K ^0 \eta '$$
 normalized by
$$D^0 \to \overline K ^0 \pi ^0 $$
 and have found that the hairpin diagram can give rise to substantial contributions to the decays where a meson with aSU(3) flavor singlet component is involved in the final state. In this scenario, we also obtain the branching ratio of
$$D^0 \to \overline K ^0 \phi $$
 as 0.55% in comparison with the experimental data of 0.83%.
119271994
$CP$ violation for $B^{0}\rightarrow \rho^{0}(\omega)\rho^{0}(\omega) \rightarrow \pi^+\pi^-\pi^+\pi^-$ in QCD factorization
In the QCD factorization (QCDF) approach we study the direct $CP$ violation in $\bar{B}^{0}\rightarrow\rho^0(\omega)\rho^0(\omega)\rightarrow\pi^+\pi^-\pi^+\pi^-$ via the $\rho-\omega$ mixing mechanism. We find that the $CP$ violation can be enhanced by double $\rho-\omega$ mixing when the masses of the $\pi^+\pi^-$ pairs are in the vicinity of the $\omega$ resonance, and the maximum $CP$ violation can reach 28{\%}. We also compare the results from the naive factorization and the QCD factorization.
16134313
The Leading power corrections to the structure functions
We show that when Bjorken $x_B$ is large, the leading order twist-four contributions to the structure functions can be expressed in terms of the derivatives of the normal twist-two parton distributions. Our analytical results are not only consistent with the parameterized power corrections extracted from the data, but also predict the flavor dependence of the power corrections. We also discuss the impact of our analytical results on the extraction and the flavor separation of the parton distributions at large $x$.
29148516
Multiple parton scattering in nuclei: Parton energy loss
Abstract Multiple parton scattering and induced parton energy loss are studied in deeply inelastic scattering (DIS) off nuclei. The effect of multiple scattering of a highly off-shell quark and the induced parton energy loss is expressed in terms of the modification to the quark fragmentation functions. We derive such modified quark fragmentation functions and their QCD evolution equations in DIS using the generalized factorization of higher twist parton distributions. We consider double-hard and hard-soft parton scattering as well as their interferences in the same framework. The final result, which depends on both the diagonal and off-diagonal twist-four parton distributions in nuclei, demonstrates clearly the Landau–Pomeranchuk–Migdal interference features and predicts a unique nuclear modification of the quark fragmentation functions.
12485364
Jet broadening in deeply inelastic scattering
In deeply inelastic lepton-nucleus scattering (DIS), the average jet transverse momentum is broadened because of the multiple scattering in the nuclear medium. The size of jet broadening is proportional to the multi-parton correlation functions inside nuclei. We show that at leading order, jet broadening in DIS and nulcear enhancement in di-jet momentum imbalance and Drell-Yan $ $ share the same four-parton correlation functions. We argue that jet broadening in DIS provide an indenpendent measurement of the four-parton correlation functions and a test of QCD treatment of multiple scattering.
14220177
Leading Soft Gluon Production in High Energy Nuclear Collisions
The leading soft gluon pT distribution in heavy ion collisions was ob-tained by Kovner, McLerran, and Weigert after solving classical Yang-Mills equations. I show explicitly this result can be understood in terms of conventional QCD perturbation theory. I also demonstrate that the key logarithm in their result represents the logarithm in DGLAP evolution equations.
16223404
Gluon minijet production in nuclear collisions at high energies
We show explicitly that the leading soft gluon p{sub T} distribution, predicted by Kovner, McLerran, and Weigert after solving classical Yang-Mills equations, can be understood in terms of conventional QCD perturbation theory. We also demonstrate that the key logarithm in their result represents the logarithm in DGLAP evolution equations. {copyright} {ital 1999} {ital The American Physical Society}