Abstract
We numerically investigate the impact of scale evolution on double parton distributions, which are needed to compute multiple hard scattering processes. Assuming correlations between longitudinal and transverse variables or between the parton spins to be present at a low scale, we study how they are affected by evolution to higher scales, i.e. by repeated parton emission. We find that generically evolution tends to wash out correlations, but with a speed that may be slow or fast depending on kinematics and on the type of correlation. Nontrivial parton correlations may hence persist in double parton distributions at the high scales relevant for hard scattering processes.
Highlights
DPDs depend on a scale, which in a physical process is given by the typical scale of the hard scattering, just as for parton distribution functions (PDFs)
We numerically investigate the impact of scale evolution on double parton distributions, which are needed to compute multiple hard scattering processes
DPDs depend on a scale, which in a physical process is given by the typical scale of the hard scattering, just as for PDFs
Summary
The cross section for a double parton scattering process can be written as dσ dx dx2 dx dx4. The cross section differences σ∆a∆b for longitudinal polarization in jet production are nonzero for most combinations a, b of quarks, antiquarks and gluons, and the same holds for prompt photon production (see e.g. table 4.1 in [25]). This will impact the overall rate of DPS as well as the transverse-momentum and rapidity distributions of the jets if there are longitudinal spin correlations between two partons in the proton. We see that a number of important DPD channels will be impacted by spin correlations of partons in the proton
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