sPHENIX cold QCD topical group

[David Morrison <morrison AT bnl.gov>]

Dear cold-QCD'ers,

If you happen to be at BNL, the seminar announcement below might be of
interest.

Dave

Nuclear Theory/RIKEN Seminar
"Forward particle production in pA: implementing the NLO hybrid formalism"
Friday, April 21, 2017, 2:00 pm
Small Seminar Room, Bldg. 510
Presented by Tuomas Lappi, University of Jyväskylä
Hosted by: 'Heikki Mantysaari'
Single inclusive particle production cross sections in high energy
hadron collisions at forward rapidity are an important benchmark process
for the CGC picture of small x QCD. The process can be calculated in the
"hybrid formalism", where a collinear large-x quark or gluon scatters
off the dense color field of the target. Recent calculations at
next-to-leading order in perturbation theory have not led to a stable
physical result for the single inclusive cross section at high
transverse momenta. The problem with these NLO calculations lies in the
subtraction procedure for the soft "rapidity" divergence which must be
absorbed into BK renormalization group evolution of the target. This
talk discusses recent work to understand and resolve the problems with
the subtraction procedure. In particular, we have recently implemented
numerically the quark channel production cross section using a new
rapidity factorization procedure proposed by Iancu et al. For a fixed
coupling one does indeed obtain a physically meaningful cross section
which is positive and reduces in a controlled way to previous leading
order calculations. However, it is not yet clear how to generalize this
to running coupling in a way that is fully consistent with previous
leading order calculations in coordinate space.

-- 
David Morrison  Brookhaven National Laboratory  phone: 631-344-5840
                Physics Department, Bldg 510 C    fax: 631-344-3253
                          Upton, NY 11973-5000  email: dave AT bnl.gov