Central exclusive diffractive production of pp¯ pairs in proton-proton collisions at high energies

Abstract

We consider the central exclusive production of the pp in the continuum and via resonances in protonproton collisions at high energies. We discuss the diffractive mechanism calculated within the tensorPomeron approach including Pomeron, Odderon, and Reggeon exchanges. The theoretical results are discussed in the context of existing WA102 and Intersecting Storage Rings experimental data, and predictions for planned or current experiments at the Relativistic Heavy Ion Collider and the LHC are presented. The distribution in y diff , the rapidity distance between the proton and antiproton, is particularly interesting. We find a dip at y diff ¼ 0 for the pp production, in contrast to the π þ π − and K þ K − production. We predict also the pp invariant-mass distribution to be less steep than for the pairs of pseudoscalar mesons. We argue that these specific differences for the pp production with respect to the pseudoscalar meson pair production can be attributed to the proper treatment of the spin of produced particles. We discuss asymmetries that are due to the interference of C ¼ þ1 and C ¼ −1 amplitudes of pp production. We have also calculated the cross section for the pp → ppΛΛ reaction. Here, the cross section is smaller, but the characteristic feature for dσ=dy diff is predicted to be similar to pp production. The presence of resonances in the pp channel may destroy the dip at y diff ¼ 0. This opens the possibility to study diffractively produced resonances. We discuss the observables suited for this purpose.

Tensor pomeron, vector odderon and diffractive production of meson and baryon pairs in proton-proton collisions

“…has only an effect of less than 0.5 %. In [18] we have discussed a first qualitative attempt to "reproduce" the experimentally observed behavior of the pp invariant mass (M 34 ) spectra observed in [29,30]. Our calculation shows that the diffractive production of pp through the s-channel f 0 (2100) resonance leads to an enhancement at low M 34 and that the resonance contribution is concentrated at |y di f f | < 1.…”

“…Recently, in [18] we discussed exclusive production of pp and ΛΛ pairs in proton-proton collisions. At the present stage, we have taken into account mainly the diffractive production of the pp continuum.…”

“…In [17], the exclusive diffractive production of the K + K − in the continuum and via the dominant scalar f 0 (980), f 0 (1500), f 0 (1710), and tensor f 2 (1270), f ′ 2 (1525) resonances, as well as the K + K − photoproduction contributions, were discussed in detail. In [18] the pp → pppp reaction was studied. Also the central exclusive π + π − π + π − production via the intermediate σσ and ρ 0 ρ 0 states in pp collisions was studied in [19].…”

Central exclusive production of K+K− pairs in proton-proton collisions

“…In our recent paper [30] we have analysed the central exclusive production (CEP) of K + K − pairs in proton-proton collisions at high energies. We have taken into account purely diffractive and diffractive photoproduction mechanisms.…”

Production of $p\bar {p}$ Pairs in UPC at the LHC

“…Central exclusive diffractive production of the pp pairs was also studied recently in proton-proton collisions [12].…”