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 non-zero 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.
Highlights
The color glass condensate (CGC) is an effective theory of small x gluons in a proton or nucleus, valid in the limit x → 0 where QCD cross sections are dominated by small x kinematics and gluon saturation is expected to be the dominant dynamics [1]
While higher order corrections are invaluable for precision studies of CGC, they are still limited to the small x kinematics where x ≤ 0.01
Recalling the kinematic relation between transverse momentum and rapidity of a produced particle in high energy collisions and the Bjorken x of the gluons of the target probed in the scattering given by x pptffi s e−y we see that production of high pt particles is necessarily dominatedpbffiffiy large x kinematics
Summary
The color glass condensate (CGC) is an effective theory of small x gluons in a proton or nucleus, valid in the limit x → 0 where QCD cross sections are dominated by small x kinematics and gluon saturation is expected to be the dominant dynamics [1]. To help clarify the contribution of gluon saturation to these processes, higher order (in αs) corrections [3] to various particle production cross sections have been computed which improve the precision of CGC calculations in the small x kinematics, commonly taken to be x ≤ 0.01. Z dxxGðx; Q2Þ Á Á Á ≃ xminGðxmin; Q2Þ; ð1Þ xmin where Á Á Á stands for the rest of the collinearly factorized cross section While this kind of an approximation may be fine for making parametric estimates or even for semiquantitative analysis of the data it cannot be expected to be precise as the above approximation disregards contribution of the larger x (x ≥ 0.01) kinematics.. While this kind of an approximation may be fine for making parametric estimates or even for semiquantitative analysis of the data it cannot be expected to be precise as the above approximation disregards contribution of the larger x (x ≥ 0.01) kinematics. making
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