Tensor Pomeron and low- x deep inelastic scattering

Abstract

The tensor-pomeron model is applied to low-x deep-inelastic lepton-nucleon scattering and photoproduction. We consider c. m. energies in the range 6 -318 GeV and Q 2 < 50 GeV 2 . In addition to the soft tensor pomeron, which has proven quite successful for the description of soft hadronic high-energy reactions, we include a hard tensor pomeron. We also include f 2 -reggeon exchange which turns out to be particularly relevant for real-photon-proton scattering at c. m. energies in the range up to 30 GeV. The combination of these exchanges permits a description of the absorption cross sections of real and virtual photons on the proton in the same framework. In particular, a detailed comparison of this two-tensor-pomeron model with the latest HERA data for x < 0.01 is made. Our model gives a very good description of the transition from the small-Q 2 regime where the real or virtual photon behaves hadron-like to the large-Q 2 regime where hard scattering dominates. Our fit allows us, for instance, a determination of the intercepts of the hard pomeron as 1.3008 ( +73 −84 ), of the soft pomeron as 1.0935 ( +76 −64 ), and of the f 2 reggeon. We find that in photoproduction the hard pomeron does not contribute within the errors of the fit. We show that assuming a vector instead of a tensor character for the pomeron leads to the conclusion that it must decouple in real photoproduction.

Extracting the Pomeron-Pomeron- f2(1270) coupling in the pp→ppπ+

“…At the present stage these coupling constants g (j) PP f 2 should be fitted to experimental data. Considering the fictitious reaction of two "real tensor pomerons" annihilating to the f 2 meson, see Appendix A of [7], we find that we can associate the couplings (2.8)-(2.14) with the following (l, S) values 2 (0, 2), (2, 0) − (2, 2), (2, 0) + (2, 2), (2, 4), (4, 2), (4, 4), (6,4), respectively.…”

“…In [4] further strong evidence against the hypothesis of a vector character of the pomeron was given. It was shown there that a vector pomeron necessarily decouples in elastic photon-proton scattering and in the absorption cross sections of virtual photons on the proton, that is, in the structure functions of deep inelastic lepton-nucleon scattering.…”

The Tensor Pomeron and Small-x Deep Inelastic Scattering

“…But, of course, quantum field theory forbids negative cross sections. A further argument against a vector pomeron is that it does not give any contribution to photoproduction data, as we show in [1]. One may also ask about the possibility of a scalar coupling of the pomeron to external particles.…”

“…Here, we want to discuss deep inelastic scattering (DIS) in the context of such a Regge model. This presentation summarizes some of the key results of [1] to which we refer the reader for further details.…”

$\alpha_s$(2019) discussions summary

“…based on NNLO jets in DIS and in (anticipated) photoproduction studies, which will be included into the world average. A discussion followed on how to properly merge the novel DIS jets α s (m Z ) result together with the more inclusive structure function results [7]. The question was raised on what to do with novel NNLO hadron collider extractions, e.g.…”