QCD factorization at forward rapidities

0486803 - ÚJF 2018 IT eng C - Konferenční příspěvek (zahraniční konf.)
Nemchik, J. - Šumbera, Michal
QCD factorization at forward rapidities.
35th International Conference of High Energy Physics (ICHEP 2010). Trieste: SISSA, 2010, č. článku 354..
[35th International Conference of High Energy Physics (ICHEP 2010). Paris (FR), 22.07.2010-28.07.2010]
Institucionální podpora: RVO:61389005
Klíčová slova: suppression * collisions
Obor OECD: Nuclear physics

We analyze several reactions on nuclear targets at forward rapidities and different energies (at smallest experimentally accessible Bjorken x(2) in the target). Nuclear effects are then usually interpreted as a result of shadowing or the Color Glass Condensate. QCD factorization of soft and hard interactions requires the nucleus to be an universal filter for different Fock components of the projectile hadron. We demonstrate, however, that this is not the case in the vicinity of the kinematic limit, Feynman x(F) -> 1, where sharing of energy between the projectile constituents becomes an issue. The rise of suppression with x(F) is confirmed by the E772 and E886 data on the Drell-Yan and heavy quarkonium production. We show that this effect can be treated alternatively as an effective energy loss proportional to initial energy. This leads to a nuclear suppression at any energy, and predicts x(F) scaling of the suppression. We demonstrate also that the same kinematic limit can be approached in transverse momentum when the Cronin enhancement of particle production at medium-high p(T) switches to a suppression at larger p(T) violating thus QCD factorization. Such an unexpected effect seems to be confirmed by the RHIC data for pion production in d+A collisions, and even for direct photons in Au+Au collisions.
Trvalý link: http://hdl.handle.net/11104/0281528