Unintegrated parton distributions and prompt photon hadroproduction

Abstract

We introduce a general expression which enables the parton distribution, unintegrated over the parton transverse momentum, to be obtained from the conventional parton densities. We use the formalism to study the effects of the transverse momentum q t of the incoming partonic system on the calculation of the transverse momentum spectra of prompt photons produced in high energy pp and pp collisions. For the purposes of illustration, we use the double logarithm approximation. For large q t we calculate the effect directly from the perturbative formalism, whereas for small q t we bound the effect using two extreme hypotheses. In both q t domains we find that the shapes of the prompt photon spectra are not significantly modified, although the cross sections are enhanced.

Improved TMD factorization for forward dijet production in dilute-dense hadronic collisions

“…Essentially, this can be done by adding a µ 2 dependence to the unintegrated gluon distributions [29][30][31][51][52][53][54]. The equations that combine such effects with the small-x evolution [55,56] show a nontrivial interplay between the non-linearities and the µ 2 dependence and this may, in particular, weaken the saturation effects.…”

Collinear and TMD quark and gluon densities from parton branching solution of QCD evolution equations

“…The results in figures 6 and 7 imply that this approximation will not be valid for observables sensitive to the detailed structure in transverse momentum of the initial state. In particular, they emphasize the role of soft-gluon coherence effects leading to angular ordering in constructing well-defined TMD distributions even at low x [15][16][17][96][97][98][99].…”

The production of a diphoton resonance via photon-photon fusion

“…where ∆ = k ⊥ /(µ + k ⊥ ), see [42] for more details, and here we have adjusted the conditions (2.16) so that the virtual corrections corresponding to emission with momentum fraction z inside the veto region are resummed. In figure 2 (left) we show the ratio of the cross section with the veto applied and k c ⊥ = 15 GeV, µ = M R = 750 GeV, to the inclusive cross section for a range of δη values and for the γγ and gg-initiated processes.…”