Breaking of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi>k</mml:mi><mml:mo>⊥</mml:mo></mml:msub></mml:math>factorization for single jet production off nuclei

The linear ${k}_{\ensuremath{\perp}}$ factorization is part and parcel of the perturbative QCD description of high-energy hard processes off free nucleons. In the case of heavy nuclear targets the very concept of nuclear parton density becomes ill-defined as exemplified by the recent derivation [N. N. Nikolaev, W. Sch\"afer, B. G. Zakharov, and V. R. Zoller, J. Exp. Theor. Phys. 97, 441 (2003).] of nonlinear nuclear ${k}_{\ensuremath{\perp}}$ factorization for forward dijet production in deep inelastic scattering off nuclei. Here we report a derivation of the related breaking of ${k}_{\ensuremath{\perp}}$ factorization for single-jet processes. We present a general formalism and apply it to several cases of practical interest: open-charm and quark and gluon-jet production in the central to beam fragmentation region of ${\ensuremath{\gamma}}^{*}p$, ${\ensuremath{\gamma}}^{*}A$, $pp$, and $pA$ collisions. We show how the pattern of ${k}_{\ensuremath{\perp}}$ factorization breaking and the nature and number of exchanged nuclear pomerons do change within the phase space of produced quark and gluon jets. As an application of the nonlinear ${k}_{\ensuremath{\perp}}$ factorization we discuss the Cronin effect. Our results are also applicable to the ${p}_{\ensuremath{\perp}}$ dependence of the Landau-Pomeranchuk-Migdal effect for, and nuclear quenching of, jets produced in the proton hemisphere of $pA$ collisions.

Перевод пока недоступен