13900650
Nuclear dependence in the Drell-Yan transverse momentum distribution
We calculate the nuclear enhancement in the Drell-Yan transverse momentum distribution in hadron-nucleus collisions. In terms of the multiple scattering picture, we compute the contributions from double scattering. Applying the generalized factorization theorem, we express the nuclear enhancement in terms of twist-4 nuclear parton correlation functions. Using the known information on these twist-4 parton correlation functions, we estimate the nuclear enhancement for Drell-Yan pairs in the large q{sub T} region. We also discuss the source of nuclear suppression in the small q{sub T} region. {copyright} {ital 1998} {ital The American Physical Society}
17569178
Nuclear enhanced power corrections to DIS structure functions
Abstract We calculate nuclear enhanced power corrections to structure functions measured in deeply inelastic lepton–nucleus scattering in Quantum Chromodynamics (QCD). We find that the nuclear medium enhanced power corrections at order of O ( α s / Q 2 ) enhance the longitudinal structure function  F L , and suppress the transverse structure function  F 1 . We demonstrate that strong nuclear effects in σ A / σ D and R A / R D , recently observed by HERMES Collaboration, can be explained in terms of the nuclear enhanced power corrections.
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.
42222465
Universality in the nuclear dependence coefficient alpha(q(T))
We derive the nuclear dependence coefficient alpha(q(T)) for Drell-Yan and J/psi production. We show that at small q(T), alpha(q(T)) is given by a universal functional form: alpha(q(T)) = a+bq(2)(T), and the parameters a and b are completely determined by either perturbatively calculable or independently measurable quantities. This universal functional form alpha(q(T)) is insensitive to A, and is consistent with existing data.
15964205
Probing Multiparton Correlation Functions In Deeply Inelastic Scattering
We derive the transverse momentum broadening of the leading pions in deeply inelastic lepton-nucleus collisions. We argue that the measurement of such transverse momentum broadening can provide direct information on the multiple-parton correlation functions inside a nucleus. We also estimate the numerical values of such broadening at different values of xB and Q 2. 11.80.La, 12.38.Bx, 13.85.Ni, 24.80.-x Typeset using REVTEX
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.
15904299
Chiral Extrapolation of Lattice Data for Heavy Meson Hyperfine Splittings
Abstract.We investigate the chiral extrapolation of the lattice data for the light-heavy meson hyperfine splittings D*-D and B*-B to the physical region for the light quark mass. The chiral loop corrections providing a non-analytic behavior in mπ are consistent with the chiral perturbation theory for heavy mesons. Since chiral loop corrections tend to decrease the already too low splittings obtained from linear extrapolation, we investigate two models to guide the form of the analytic background behavior: the constituent quark potential model, and the covariant model of QCD based on the ladder-rainbow truncation of the Dyson-Schwinger equations. The extrapolated hyperfine splittings remain clearly below the experimental values even allowing for the model dependence in the description of the analytic background.
2572489
Chiral extrapolation of lattice data for the hyperfine splittings of heavy mesons
Hyperfine splittings between the heavy vector ${(D}^{*}{,B}^{*})$ and pseudoscalar $(D,B)$ mesons have been calculated numerically in lattice QCD, where the pion mass (which is related to the light quark mass) is much larger than its physical value. Naive linear chiral extrapolations of the lattice data to the physical mass of the pion lead to hyperfine splittings which are smaller than experimental data. In order to extrapolate these lattice data to the physical mass of the pion more reasonably, we apply the effective chiral perturbation theory for heavy mesons, which is invariant under chiral symmetry when the light quark masses go to zero and heavy quark symmetry when the heavy quark masses go to infinity. This leads to a phenomenological functional form with three parameters to extrapolate the lattice data. It is found that the extrapolated hyperfine splittings are even smaller than those obtained using linear extrapolation. We conclude that the source of the discrepancy between lattice data for hyperfine splittings and experiment must lie in non-chiral physics.
119492681
Heavy meson decay constants to 1/m(Q)
We introduce the vector meson contributions in heavy-light chiral perturbation theory (HLCPT) and construct the Lagrangian and current to the order 1/mQ. With this, to the order (Λcsb is the chiral symmetry breaking scale) we calculate corrections to fD and fB arising from coupled-channel effects to the orders 1/mc, and 1/mb. At the tree level in HLCPT, using the relativistic Bethe–Salpeter (BS) equation with the kernel containing a confinement term and a gluon exchange term in a covariant generalization of the coulomb gauge we calculate and when mQ → ∞ as well as the 1/mQ corrections. HLCPT and the heavy quark effective theory (HQET) are matched at the scale Λcsb. Adding the perturbative and nonperturbative contributions we give the values for fD and fB, respectively. It is found that our result is in agreement with the relation fD = fB from lattice calculations.
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%.
119299313
CP violation in $B^{\pm} \rightarrow \pi^{\pm}\pi^{+}\pi^{-}$ in the region with low invariant mass of one $\pi^{+}\pi^{-}$ pair
Recently, the large CP asymmetries in B → πππ decays were found by the LHCb Collaboration to localize in the region m π+π− < 0.4 GeV. We find such large localized CP asymmetries may be due to the interference between a light scalar and ρ(770) intermediate resonances. Consequently, we argue that the distribution of CP asymmetries in the Dalitz plots of three-body B decays could be very helpful for identifying the presence of the scalar resonance.