Rapidity loss, spin, and angular asymmetries in the scattering of a quark from the color field of a proton or nucleus

Abstract

We calculate the helicity amplitudes for scattering of a quark from both large and small x gluons of a target proton or nucleus using spinor helicity formalism. We show that scattering from large x gluons of the target results in nonzero spin asymmetry at intermediate p t as well as rapidity loss of the projectile quark. We comment on how this can also generate angular asymmetries in particle production in high energy collisions.

Quarks at next-to-eikonal accuracy in the CGC I: Forward quark-nucleus scattering

“…A similar idea is also proposed in [66] where a formulation for unintegrated gluon distributions that interpolates between the small and moderate values of energy is studied. A different approach based on exchanging longitudinal momentum during the scattering to go beyond eikonal accuracy is pursued in [67][68][69]. Also, NEik corrections are computed in the context of soft gluon exponentiation for example in [70][71][72].…”

Photon-jet production cross section and angular correlations in high energy proton-nucleus collisions

“…In [4] we calculated the cross section for scattering of a quark from both small and large gluons of the target. Specifically, we considered scattering of a projectile parton of a given helicity [7] on the unpolarized target and showed that inclusion of large parton of the target leads to a spin asymmetry in the production cross section.…”

“…To remedy this it is essential to generalize the CGC formalism to include large partons of the target. In [4] we proposed a new formalism which includes scattering from both small and large partons of the target.…”

Lensing mechanism meets small- x physics: Single transverse spin asymmetry in p↑+p and p

“…(47) and (44) into Eq. (14), performing the substitution (17), and integrating out r with the help of the delta function yields [cf. Eq.…”

“…The recent decade and a half saw a surge of research activity at the intersection of small-x and spin physics in quantum chromodynamics (QCD) [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. Topics receiving attention include both the longitudinal [10,11,15,[18][19][20][21][22][23] and transverse [7,[24][25][26][27][28][29][30] spin physics of the proton.…”