New anomalous exchange in Regge phenomenology and hard diffraction (original) (raw)
Exclusive Meson Electroproduction: GPDs, Regge and Dispersion Relations
Arxiv preprint arXiv:0904.3071, 2009
Exclusive pi0 electroproduction from nucleons at large photon virtuality can be described in terms of Generalized Parton Distributions, particularly the chiral odd subset. Chiral odd GPDs are related to transversity and can be accessed experimentally for various special choices of observables. This is accomplished by choosing C-parity odd and chiral odd combinations of t-channel exchange quantum numbers. These GPDs are calculated in a spectator model, and are constrained by boundary functions. Alternatively, the production amplitudes correspond to C-odd Regge exchanges with final state interactions. The helicity structure of the virtual photoproduction amplitudes provides relations between the partonic description via GPDs and the hadronic, Regge description of C-odd processes, all via quark helicity flip. GPDs, in general, are analytic functions of energy variables. Their integrals over unobservable parton momenta thereby satisfy Dispersion Relations (DR). Using DR's could allow the real part of the amplitudes, the integrated GPDs, to be extracted from the more easily measured imaginary parts. However, at non-zero momentum transfer DRs require integration over unphysical regions of the variables. We show that the relevant unphysical region of the non-forward DRs is considerable. This will vitiate the efforts to avoid the actual measurement of the real parts more directly.
Single-diffractive production of heavy mesons in pp collisions
2021
In this proceeding we present our theoretical results for the single-diffractive production of open heavy flavor mesons in 𝑝 𝑝 collisions. We estimate that this mechanism constitutes 0.5-2 per cent of the inclusive production of the same mesons in Tevatron and LHC kinematics. In Tevatron kinematics the theoretical expectations are in reasonable agreement with the available experimental data. In LHC kinematics the predicted cross-sections are sufficiently large and could be accessed experimentally. We also analyze the dependence of the cross-sections on multiplicity of coproduced hadrons, and find that it should be significantly lower than that of inclusive production of the same heavy mesons. If confirmed experimentally, this result would corroborate that multiplicity enhancement seen in inclusive production of different quarkonia states is related to multipomeron contributions, rather than other mechanisms.
Diffractive baryon production and the relation between reggeon and photon couplings
Nuclear Physics B, 1976
We illustrate how one can employ the ~-analogy hypothesis, introduced in a previous paper, which relates the couplings of the leading natural-parity reggeon exchanges, P, f and to, to those of the isoscalar part of the photon. It enables us to predict the differen-,5+ ,3tial cross sections for the diffractive processes pp ~ pN (3 , 1688), N (7 , 1520), and N*(~-, 2190) starting from Regge fits to pp elastic scattering, with just a single free parameter in each case. This success stems from an intimate relation between electromagnetic and hadronic couplings demanded by duality, scaling and vector dominance. We do not expect dips due to pole-cut interference in the N* production differential cross sections because of their more complicated helicity structure.
Physics Letters B - PHYS LETT B, 2010
We evaluate within the LO DGLAP approximation the dependence on energy of the cross section of the photo(electro)production of vector meson V (V=J/ψ,…) in the hard elastic processes off a parton γ∗+g→V+g as the function of momentum transfer t=(qγ−pV)2. We demonstrate that in the limit −t⩾mV2+Q2 the cross section does not contain double logarithmic terms in any order of the DGLAP approximation leading to the energy independent cross section. Thus the energy dependence of cross section γ∗+p→J/ψ+rapidity gap+X is governed at large t by the gluon distribution within a proton, i.e. it is unambiguously predicted within the DGLAP approximation including the stronger WγN dependence at larger −t. This prediction explains recent HERA data. The calculations which follow perturbative Pomeron logic predict opposite trend of a weaker WγN dependence at larger t. We explain that at the HERA energies double logarithmic terms characteristic for DGLAP approximation dominate in the hard processes as th...
The Phenomenology of Pomeron Enhancement
2009
Multi Pomeron interactions are the main source of high mass diffraction. Their role in high energy dynamics greatly influences the predictions for high energy cross sections and survival probabilities of hard diffraction channels, notably, diffractive Higgs production at the LHC. Our approach, is motivated by the fact that we obtain a very small value for the fitted slope of the Pomeron trajectory, which justifies the use of perturbative QCD for soft scattering. Our suggested model differs from the proposal of the Durham KMR group which is based on a parton model interpretation of the Reggeon calculus in the complex J-plane in which multi Pomeron vertices are arbitrarily defined. The theoretical input and predictions of the two groups, as well as their data analysis and procedures are compared and evaluated.
Diffraction and Vector Mesons: Summary
15th International Workshop on Deep-Inelastic Scattering and Related Subjects DIS 2007, 2007
We summarize recent experimental results and theoretical developments related to the topics of diffraction and vector mesons discussed at the DIS2007 Workshop.
Pseudoscalar and scalar meson photoproduction interpreted by Regge phenomenology
Physical Review C, 2023
We have evaluated pseudoscalar and scalar neutral pion photoproduction in γ p → π 0 p and a 0 0 p above the resonance region and within Regge phenomenology. Our fit, including GlueX pseudoscalar photoproduction data, shows that previous Stanford Linear Accelerator Center (SLAC) measurements for γ p → π 0 p above E γ = 4 GeV vary substantially from SLAC data with more recent measurements made by GlueX in the vicinity of E γ = 9 GeV. The Regge model predicts that the beam polarization asymmetry of the scalar meson is opposite to that of pseudoscalar meson photoproduction; however, the cross sections are similar. While the natural parity vector meson exchange is dominant in both cases, the contribution of the unnatural parity pseudovector meson exchange is very small. Using Regge phenomenology, we predicted high-energy behavior for double polarized observables E, F , G, and H for the reactions γ p → π 0 p and a 0 0 p.