Diffractive excitation of heavy flavors: Leading twist mechanisms

Abstract

Diffractive production of heavy flavors is calculated within the light-cone dipole approach. Novel leading twist mechanisms are proposed, which involve both short and long transverse distances inside the incoming hadron. Nevertheless, the diffractive cross section turns out to be sensitive to the primordial transverse momenta of projectile gluons, rather than to the hadronic size. Our calculations agree with the available data for diffractive production of charm and beauty, and with the observed weak variation of the diffraction-to-inclusive cross section ratios as function of the hard scale.

Higgs hadroproduction at large Feynman x

“…This behavior also has been obtained in explicit perturbative calculations [14]. However, the 1 m 2 Q suppression in the intrinsic heavy quark probability is effectively compensated by the Higgs coupling to the heavy quark, which is of order G F m 2 Q in the rate.…”

Diffractive dijet production inp¯pcollisions ats=1.96 TeV

“…At −t ∼ 2 GeV 2 , the measured event-rate for the inclusive-event sample is a factor of ∼ 10 larger than the DL-model prediction normalized to the data distribution in the region of −t ≤ 0.5 GeV 2 . The relatively flat xp Bj distribution and the small Q 2 dependence of the diffractive to non-diffractive ratios, combined with the Q 2 independence of the t distributions, favor models of hard diffractive production in which the hard scattering is controlled by the partondistribution-function of the recoil antiproton while the rapidity-gap formation is governed by a color-neutral soft exchange [45]- [48].…”

“…Such behavior favors models in which the hard scattering is controlled by the low-x parton distribution function of the recoiling antiproton, just as in ND interactions, while a color-neutral soft exchange allows the antiproton to escape intact forming the rapidity gap (see, for example, Refs. [45]- [48]). …”

Hard hadronic diffraction is not hard

“…The leading twist contributions to diffractive QQ production come from both sources: when both exchanged gluons couple to the valence quark which gives rise to the QQ pair, and when one of the gluons is coupled to another spectator quark not participating in the hard scattering as is shown in Fig. 9, right [39] (for more details, see Ref. [3]).…”

“…A detailed analysis of various contributions into the diffractive QQ production from both diffractive gluon and quark excitations has been performed in Ref. [39]. For example, in the case of diffractive quark excitation q+g → (QQ)+q the dynamics of inclusive heavy flavor production is characretized by five distinct topologies which can be classified as: (i) bremsstrahlung (like in DY), and (ii) production mechanisms as illustrated by the Feynman graphs in Fig.…”