What can we learn about the Regge plane from pp cross sections?

We have analysed pp total and different cross sections from s = 10 (GeV)² upwards in terms of singularities in the Regge plane. The data can be fitted by poles alone but a considerably more continuous discontinuity structure is possible. An interpretation of the pole residues in terms of expected Regge poles runs into difficulties at some values of t.     

Shackless on linear absorption models

We examine the fundamental constraints that all Linear Absorption Models must possess, independent of the rescattering amplitude. These constraints are most direct in impact parameter space, where the re-scattering appears simply as a multiplicative factor. It is a crucial test of such models that the ratio of two exchanges — for example vector and tensor exchanges — is completely specified in b-space by the ratio of input Regge pole amplitudes. Amplitude analysis exist for vector π exchange, in π⁻p→π^On. Lacking experimental A₂ tensor amplitudes, we use the Linear Absorption Models constraint to calculate A₂ exchange from ? input, and compare the results with π⁻p→η^On data. Both simplicity and duality assumptions for Regge pole couplings are considered. The results suggest that Linear Absorption Models constraint is not fully consistent with data.     

Symmetries of Regge-Regge cuts

Regge-Regge cuts are shown to satisfy strong symmetry constraints in any model which incorporates Finkelstein's cut selection rule, SU(3) symmetry of Regge residues, and exchange degeneracy of trajectories and residues. These imply, amongst other things, the strong suppression of Regge-Regge cuts in pion-nucleon charge exchange, arising from a cancellation between ?-P′ and A₂-ω cuts. Therefore if Finkelstein's selection rule is valid, the πN change amplitudes cannot be understood by adding Regge-Regge cuts to an absorbed ? pole amplitude.     

DipoleA 2 meson and the high-energy reaction π+ → πN 2 3/*

On the basis of a dipole model for theA ₂ meson, we describe the angular distribution of the high-energy reactionπ ⁺ p→ηN ₂ ^3/* . Our results are qualitatively compared with the existing experimental data and with the predictions of the usual Regge pole model.     

Kaon-nucleon finite energy sum rules revisited

Kaon-nucleon finite energy and continuous moment sum rule integrals are evaluated using recent phase-shift solutions to extract the t-channel exchange amplitudes and the results are compared with Regge pole models. The exchange degeneracy breaking previously observed in the ? and A₂ amplitudes is confirmed, and it is suggested that this may be due to an exotic P₀₁ KN resonance. Regge trajectories are extracted from the integrals and are in good agreement with those found from direct fits to high-energy data.     

The structure of t-channel exchanges in KN scattering

Recent phase-shift solutions are used to evaluate KN FESR integrals in order to examine zeros and phases of the t-channel exchange amplitudes in the most model-independent way. The results suggest that the line reversal breaking in KN CEX observed for pL ? 5.5 GeV/c is due to a large EXD breaking component in the A₂ exchange flip amplitude. The ? exchange flip amplitude is well described by a Regge pole amplitude with NWSZ at ?t ≈ 0.5 (GeV/c)². The imaginary parts of ? and ω exchange non-flip amplitudes are both peripheral.     

Finite energy sum rules for π-N backward scattering

Finite energy sum rules for the A and S,π-N scattering amplitudes are saturated in the region ?0.4 GeV²< u <0 with a number of s andt channel resonances. It turns out that one needs a rather large π—π s wave contribution, to get agreement with the high energy Regge pole analysis, which explains the dip structure in π⁺p scattering atu ₀=?0.15 GeV² by a zero in theN _α contribution. The coupling of theN _α trajectory seems to be much stronger than the coupling of theN _γ andΔ _δ trajectories.     

Regge theory and QCD in large-angle scattering

We argue that exclusive processes whose cross-sections are determined by Regge pole trajectory exchanges, α(t), at small momentum transfers (t), are controlled by these same exchanges at very large |t| too. The analysis is based on a Reggeized version of the constituent interchange model (CIM), which predicts that α(t)→?1 ast→?∞, and that the asymptotic form of the Regge residues is fixed by the dimensional counting rules and CIM constraints. Between the two regimes of soft and hard scattering there is an intermediate region where Regge cuts are important, but these higher-twist effects die away as |t| is increased. We show that this hypothesis is consistent with high energy nucleon-nucleon and pion-nucleon scattering at all angles.     

Diffractive photoproduction of the ϱ-meson

?^o photoproduction is analyzed in the framework of the Regge pole model, considering only pomeron exchange and assuming coservation of the photon helicity in the s-channel for small momentum transfer (∣t∣ < 0.3 (GeV/c)²). The main features of ?^o photoproduction are well described.     

Single Regge pole model for large angle elasticp-p scattering at high energies

The elastic proton-proton angular distribution at large momentum transfers (?t?8 (GeV/c)²) and energies above 10 GeV laboratory momentum can be understood in the framework of a single Regge pole model.     

K 0 regeneration in nuclei

Recent data onK ⁰ regeneration are critically analysed by means of both dispersion relations and a Regge pole model for kaon-nucleon scattering. Theoretical limits on the precision level are established.     

High-mass diffraction and Regge behavior of total cross sections

We consider a modified two-component model of particle production in which diffractive excitation into high mass states gives a contribution to K^±p, π^±p and pp total cross sections of sufficient magnitude and with the proper associated threshold to be a possible explanation of deviations of σ_tot from Regge pole model fits at Serpukhov energies. We present tests of the model. for K⁺p scattering by extrapolating σ_tot to National Accelerator Laboratory energies and by calculating the high mass diffraction contribution to the forward peak in inclusive reactions. The consistency of this scheme is discussed in relation to the pomeron intercept and the form of the triple-pomeron coupling.     

ϱ dominance and Regge coupling in inclusive reactions

The ? Regge pole residues are calculated under the assumption of ? dominance of the isovector, even G parity component of inclusive reactions. The calculated residues compare well with total cross section data and allow successful predictions of the charge dependence of pion production in the central region. Serious difficulties are encountered with the assumption of P + f dominance of the isoscalar even G parity component.     

Double Regge exchange phenomenology

We construct a double Regge exchange amplitude which has the proper analytic structure and which is phenomenologically viable. The various couplings involved can be estimated using pole extrapolation techniques which are successful in two-body scattering. We explicitly calculate the double Regge exchange contributions to the well-measured, and related, processes K^±p → K⁰π^±p and π^?p → K^?K⁰p. In this way the observed features of the dimeson partial-wave production amplitudes are used to text the double-exchange approach.     

Application of K-matrix CMSR'S to single charged pion photoproduction

The background terms, required in addition to Regge poles with some definite properties, in order to describe the high energy behavior of the t-channel single pion photoproduction amplitudes F_t^(?)(v, t), i = 1, …, 4, are investigated in the framework of a reggeized K-matrix model. To this end continuous moment sum rules (CMSR's) are applied, not to the full amplitudes, but just to the two-particle K-matrix amplitudes assumed to show pure Regge pole asymptotic behavior. The K-matrix amplitudes are defined by taking into account in the Heitler equation the elastic (πN) intermediate state alone. Such a definition corresponds to a weak-cut model with only final-state interactions included. It turns out that strong background contributions are still present on the high energy side of the K-matrix CMSR's. The Regge cut contributions generated within our formalism are found to be too weak to account for the background terms in the full amplitudes. This is presumably to a great extent due to the neglect of the (?N) diffraction-dissociation intermediate state in the definition of the K-matrix amplitudes.     

Non-diffractive production of meson resonances

We study the peripheral cross sections of resonances that cannot be produced by π-exchange. In particular, we concentrate on the four meson nonets expected as L = 1 quark states (i.e., the J^P = 0⁺π_N(980); J^P = 1⁺ A₁, B; J^P = 2⁺ A₂). We use SU(3), Regge poles, factorization, exchange degeneracy, pole extrapolation, and the vector-meson-photon analogy. We predict the cross sections in both photoproduction and non-diffractive hadronic reactions. In passing, we discuss the large unnatural-parity (B, K?Q_B) exchange contributions and even the possibility of studying ππ → πω while avoiding the B production background.     

A possible non-Regge behaviour of the πN amplitude at high energies

The total cross sections up to 65 GeV/c and the experimental real parts of the isospin evenπN forward amplitude are compatible with the dispersion relation. However the arguments which led to the introduction of theP′ Regge pole (α _p′≈0.5) are not valid. The data are compatible with the existence of the integral in Lehmann's sum rule, which implies a finite real partD ⁺(∞) at infinity. — The isospin odd combinationσ ^? is still consistent with the reggeizedρ-exchange model and with Pomeranchuk's theorem.