Wigner Distributions Using Light-Front Wave Functions

We report on some recent advances in calculating the Wigner distributions for quarks and gluons, using overlaps of light-front wave functions.Comment: Talk given at the QCD Evolution Workshop, May 22-26, 2017, Jefferson Lab, US

Diffraction Patterns in Deeply Virtual Compton Scattering

We report on a calculation to show that the Fourier transform of the Deeply Virtual Compton Scattering (DVCS) amplitude with respect to the skewness variable \zeta at fixed invariant momentum transfer squared t gives results that are analogous to the diffractive scattering of a wave in optics. As a specific example, we utilize the quantum fluctuations of a fermion state at one loop in QED to obtain the behavior of the DVCS amplitude for electron-photon scattering. We then simulate the wavefunctions for a hadron by differentiating the above LFWFs with respect to M^2 and study the corresponding DVCS amplitudes in light-front longitudinal space.Comment: Presented at the 17 th International Spin Physics Symposium, Kyoto, Japan, October 2-7, 200

Jet Production in pppp Collisions: Dependence on Jet Algorithm

We report on a recent calculation of single-inclusive high-$p_T$ jet production in unpolarized and longitudinally polarized $pp$ collisions at RHIC, investigating the effect of the algorithm adopted to define the jets on the numerical results for cross sections and spin asymmetries.Comment: Prepared for the Third Workshop on the QCD Structure of the Nucleon : QCD N'12, 22-26 October, 2012, Bilbao, Spai

Linearly polarized gluons in charmonium and bottomonium production in color octet model

We study the possibility to probe the unpolarized and linearly polarized transverse momentum- dependent gluon distributions in unpolarized pp collision in charmonium and bottomonium produc- tion, employing non-relativistic QCD (NRQCD) based color octet model within transverse momentum dependent (TMD) factorization framework. The transverse momentum (p T ) and rapidity distributions of J/{\psi} and {\Upsilon}(1S) at LHCb, RHIC and AFTER energies are estimated. Significant modulations in transverse momentum spectrum of quarkonium in the low p T region is obtained when contributions of linearly polarized gluons inside an unpolarized proton are taken into account. The results of quarko- nium production in color octet model and color evaporation model are compared.Comment: Replaced with the revised version, to appear in PR

J/ψJ/\psi Production in Polarized and Unpolarized epep Collision and Sivers and cos⁡2ϕ\cos2\phi Asymmetries

We calculate the Sivers and $\cos2\phi$ azimuthal asymmetries in $J/\psi$ production in polarized and unpolarized semi-inclusive $ep$ collision respectively, using the formalism based on transverse momentum dependent parton distributions (TMDs). Non-relativistic QCD based color octet model is employed for calculating the $J/\psi$ production rate. The Sivers asymmetry in this process directly probes the gluon Sivers function. The estimated Sivers asymmetry at $z=1$ is negative which is in good agreement with COMPASS data. We also investigate the effect of TMD evolution on the Sivers asymmetry. The $\cos2\phi$ asymmetry is sizable and probes the linearly polarized gluon distribution in an unpolarized proton.Comment: 29 pages, 11 figures. Details of calculation adde

Jet production in (un)polarized pp collisions: dependence on jet algorithm

We investigate single-inclusive high-pT jet production in longitudinally polarized pp collisions at RHIC, with particular focus on the algorithm adopted to define the jets. Following and extending earlier work in the literature, we treat the jets in the approximation that they are rather narrow, in which case analytical results for the corresponding next-to-leading order partonic cross sections can be obtained. This approximation is demonstrated to be very accurate for practically all relevant situations, even at Tevatron and LHC energies. We confront results for cross sections and spin-asymmetries based on using cone- and kt-type jet algorithms. We find that jet cross sections at RHIC can differ significantly depending on the algorithm chosen, but that the spin asymmetries are rather robust. Our results are also useful for matching threshold-resummed calculations of jet cross sections to fixed-order ones.Comment: 11 pages, 7 figure

Accessing Linearly Polarized Gluon Distribution in J/ψJ/\psi Production at the Electron-Ion Collider

We calculate the $cos~2 \phi$ asymmetry in $J/\psi$ production in electron-proton collision for the kinematics of the planned electron-ion collider (EIC). This directly probes the Weisz\"acker-Williams (WW) type linearly polarized gluon distribution. Assuming generalized factorization, we calculate the asymmetry at next-to-leading-order (NLO) when the energy fraction of the $J/\psi$ satisfies $z<1$ and the dominating subprocess is $\gamma^* +g \rightarrow c + {\bar c}+g$. We use non-relativistic QCD based color singlet model for $J/\psi$ production. We investigate the small $x$ region which will be accessible at the EIC. We present the upper bound of the asymmetry, as well as estimate it using a (i) Gaussian type parametrization for the TMDs and (ii) McLerran-Venugopalan model at small $x$. We find small but sizable asymmetry in all the three cases.Comment: Version to appear in Phys. Rev.