X(3872) as a molecular DD¯*

Abstract

We discuss the possibility that the X(3872) can be a DD * molecular bound state in the Bethe-Salpeter equation approach in the ladder and instantaneous approximations. We show that the DD * bound state with quantum numbers J P C = 1 ++ exists. We also calculate the decay width of X(3872) → γJ/ψ channel and compare our result with those from previous calculations.

π-N Drell-Yan Process in TMD Factorization

“…The scale dependence of the T-odd distributions, such as the Sivers function and the Boer-Mulders function, is more involved than that of the T-even distributions. This is because their collinear counterparts are the twist-3 multiparton correlation functions [39,64,84,113,114], for which the exact evolution equations are far more complicated than those for the unpolarized distribution function. In numerical calculation, some approximations on the evolution kernels are usually adopted.…”

“…A different choice was adopted in Ref. [114], where the homogenous terms of the exact evolution kernel for the Qiu-Sterman function [84,[115][116][117][118][119][120][121][122][123] were included to deal with the scale dependence of Qiu-Sterman function: with P f1 qq the evolution kernel of the unpolarized PDF…”

“…For a comparison, in Fig. 3 we plot the TMD evolution of the Sivers function for proton in b space and the k ⊥ space using the above mentioned two approaches [114]. In this estimate, the next leading order C-coefficients ∆C T q←i was adopted from Ref.…”

“…(57), the Sivers asymmetry A Siv UT as function of x p , x π , x F and q ⊥ in π − p ↑ → µ + µ − + X in the kinematics of COMPASS Collaboration was calculated in Ref. [114], as shown in Fig. 6.…”

“…. The Sivers asymmetry within TMD factorization for a π − scattering off transversely polarized proton Drell-Yan process as functions of xp (upper left), xπ (upper right), xF (lower left) and q ⊥ (lower right), compared with the COMPASS data[11].Figure fromRef [114]…”