arXiv subjects
Publications and source records attributed to Jian-Ping Ma.
The hadron-energy evolution (Collins and Soper) equation for all the leading-twist transverse-momentum and spin dependent parton distributions is derived in the impact parameter space. Based on the result, we present resummation formulas for the spin structure functions in the semi-inclusive deep inelastic scattering.
Based on a recent work on the quantum chromodynamic (QCD) factorization for semi-inclusive deep-inelastic scattering (DIS), we present a set of factorization formulas for the spin-dependent DIS and Drell-Yan cross sections at low transverse momentum.
We present a leading-order pQCD calculation of the helicity-flip $Δ\to Nγ^*$ matrix element $G_0$ (Coulomb quadrupole amplitude $C2$), taking into account the transverse momenta of the quarks and the contribution from the gluons. In the large $Q^2$ limit, its scaling behavior acquires a double-logarithmic correction $\log^2{(Q^2/Λ^2)}$ compared with the standard scaling analysis, due to the contribution from the orbital motion of the small-$x$ partons. Based on this and on the latest JLab experimental results of the $C2-M1$ ratio $R_{SM}$ at $Q^2$ = 3 $\sim$ 4 GeV$^2$, we make a phenomenological prediction for the latter at higher values of $Q^2$.
The quark recombination mechanism is proposed to explain the asymmetry between production rates of $D^+$ and of $D^-$ in their inclusive productions, and also asymmetries for other charmed hadrons. These asymmetries are observed in experiment and are called as leading particle effects. In this work we give a general analysis for contributions of quark recombination to these asymmetries. The contributions consist of a perturbative- and nonperturbative part. We perform two types of factorization by considering the produced hadron with large transverse momentum and by taking charm quark as a heavy quark, respectively. In the case of large transverse momentum the effect of quark recombination is the standard twist-4 effect. We find that the contributions are parameterized with four nonperturbative functions, defined with four quark operators at twist-4, for initial hadrons without polarization. By taking charm quark as a heavy quark the factorization can be performed with the heavy quark effective theory(HQET). The effect of quark recombination is in general parameterized by eight nonperturbative parameters which are defined as integrals with matrix elements of four quark operators defined in HQET. For unpolarized hadrons in the initial state, the parameters can effectively be reduced to four. Perturbative parts in the two types of factorization are calculated at tree-level.
We classify the hadron light-cone wave-function amplitudes in terms of parton helicity, orbital angular momentum, and quark flavor and color symmetries. We show in detail how this is done for the pion, $ρ$ meson, nucleon, and delta resonance up to and including three partons. For the pion and nucleon, we also consider four-parton amplitudes. Using the scaling law derived recently, we show how these amplitudes scale in the limit that all parton transverse momenta become large.
We introduce a systematic way to write down the Fock components of a hadronic light-cone wave function with $n$ partons and orbital angular momentum projection $l_z$. We show that the wave function amplitude $ψ_n(x_i,k_{i\perp},l_{zi})$ has a leading behavior $1/(k^2_\perp)^{[n+|l_z|+{\rm min}(n'+|l_z'|)]/2-1}$ when all parton transverse momenta are uniformly large, where $n'$ and $l_z'$ are the number of partons and orbital angular momentum projection, respectively, of an amplitude that mixes under renormalization. The result can be used as a constraint in modeling the hadronic light-cone wave functions. We also derive a generalized counting rule for hard exclusive processes involving parton orbital angular momentum and hadron helicity flip.
We study the three-quark light-cone amplitudes of the proton including quarks' transverse momenta. We classify these amplitudes using a newly-developed method in which light-cone wave functions are constructed from a class of light-cone matrix elements. We derive the constraints on the amplitudes from parity and time-reversal symmetries. We use the amplitudes to calculate the physical observables which vanish when the quark orbital angular momentum is absent. These include transverse-momentum dependent parton distributions $Δq_T(x, k_\perp)$, $q_T(x, k_\perp)$, $δq(x, k_\perp)$, and $δq_L(x,k_\perp)$, twist-three parton distributions $g_T(x)$ and $h_L(x)$, helicity-flip generalized parton distributions $E(x, ξ=0, Q^2)$ and its associates, and the Pauli form factor $F_2(Q^2)$.