Coherent and incoherent particle production off nuclei at high energies

The Glauber-Gribov model for hadronnucleus scattering is extended to multiproduction processes by supplimenting it with the AGK cutting rules. In contrast to the standard Glauber approach neither smallness of the interaction radius compared to the nuclear radii nor Gaussian form of theh-N-interaction profile function are assumed. We consistently use the theory of superciritical Pomeron. However all the results are more general and do not depend on the specific parametrization of the Pomeron pole amplitude. The inelastic screening due to the low mass diffractive excitations is also included. The cross-sections of coherent and incoherent diffractive production of the low mass hadronic states are calculated. We comment on the novel features of particle-nucleus interactions at superhigh energies when the interaction region blows up to the nucleus size. Specifically, one encounters here the rapid rise of the coherent interaction cross-sections and strong suppression of incoherent quasielastic processes.     

Reggeon field theory: Formulation and use

We formulate and discuss Reggeon field theory, which enables one to systematically analyze the exchange of Regge poles and associated branch points in high energy hardron scattering. The field theory is first motivated by a consideration of hybrid Feynman graphs, and then a more general derivation from crossed-channel multiparticle unitarity relations is given. Rules for Reggeon interaction and propagation are formulated. We treat in some detail the problem of the Pomeron or vacuum pole which has α(0) = 1 and is responsible for diffractive processes. In particular the renormalization group analysis of Reggeon field theory is presented and the structure of Pomeron partial wave amplitudes is elucidated. Also the question of Pomeron or absorptive corrections to secondary trajectories (both fermion and boson) is considered. We make some comments on important problems yet remaining in Reggeon field theory; in particular, we stress the study of its s-channel content.     

Can a pomeron be really “supersoft”?

The low energy J/gf photoproduction cross-section has been studied on the basis of the Pomeron model. To incorporate the discrepancy between experimental data and predictions by conventional models, i.e. the sum of the soft Pomeron with intercept 1.08 and the hard Pomeron with intercept 1.418, a Regge trajectory associated with a scalar meson (f,a) exchange which we call “supersoft” Pomeron, is introduced additionally. To distinguish between the conventional model and this new additional Pomeron, observations related to other polarization observables in upcoming polarized experiments are discussed.     

On the factorization of the pomeranchuk singularity in the Mueller-Regge diagrams

It is shown that the j plane singularity (Pomeron) which leads to a rising total cross-section like (lns)^?, ? > 0. cannot be factorizable in the Mueller diagrams for inclusive production of particles with large rapidity differences. The relevance of this result for the theories of a renormalized Pomeron is discussed.     

Pairing with a delta interaction in the energy density nuclear mass formula

The variations of the average pairing strength in the (N, Z) plane are studied with a δ-interaction in the frame of the self-consistent energy density formalism. It is found that the same δ-interaction with constant strength can be used for protons and neutrons in spherical nuclei near the stability line. This interaction is used to study the extrapolation of the average pairing strength to deformed nuclei, to the superheavy region and to the regions of the drip lines. The consequences of the results for the stability of superheavy nuclei and for magic numbers far from the stability region are examined.     

Diffractive photoproduction of charm at the HERA ep collider

For various kinematical domains, the cross section for the diffractive photoproduction of D* mesons at the HERA ep collider is calculated within a model based on perturbation theory. The results obtained by using different models of the Pomeron are compared.     

Pomeron factorisation and the reaction γN → φN

Because of the suitability of γN → φN for studying the Pomeron, we systematically investigate the tests for Pomeron factorisation possible in this rather clean reaction, particularly from the more feasible experiment which measures the φ-density-matrix, and also an experiment measuring the recoil nucleon polarisation; the complete set of initial polarisation configurations has been considered.For any two-body parity-conserving process, a simple consequence of factorisation is M-purity which asymptotically corresponds to purely natural or purely unnatural parity in the crossed channel. Factorisation tests, therefore, include M-purity tests, but M-purity does not necessarily imply factorisation.For the φ-decay density-matrix we give all the possible factorisation tests, and show that our tests are exhaustive. A separate measurement of the recoil nucleon polarisation is shown to complement adequately the information obtained from the φ-decay density-matrix in the factorising case.For the φ-density matrix, some of the M-purity tests refer to dominant amplitudes and persist even if s-channel meson-helicity-conservation (which is experimentally true approximately) holds exactly. These tests should be easy to perform. The tests which invoke factorisation more crucially than only M-purity do not persist in that manner; these refer to the helicity nonconserving amplitudes. However, factorisation for such small amplitudes could be advantageously tested here, because of their being masked by the large amplitudes elsewhere.The factorisation tests for the φ-density-matrix can be used to distinguish a pure Regge pole type Pomeron from (a) an M-pure “cut-pole mixture” type Pomeron or an M-impure (hence nonfactorising) “cut-pole mixture” type Pomeron and also (b) a factorising “cut-pole mixture” type Pomeron or a nonfactorising “cut-pole mixture” type Pomeron. Here we have taken departure from relative reality of all amplitudes as the defining criterion for a “cut-pole mixture.” Such tests would require polarised photons and/or targets.Present γN → φN data are not adequate enough to allow firm conclusions about Pomeron factorisation, though they do indicate M-purity for the Pomeron, corresponding to pure natural parity. This is consistent with Pomeron factorisation, but M-purity is only a necessary consequence of factorisation. Better and more γN → φN data are needed to get a more complete picture of Pomeron factorisation.     

Two-muonic atoms

X-ray transition energies for two-muonic atoms are calculated. The basis are relativistic self-consistent-field calculations including the corrections normally known in muonic atoms plus the vacuum polarization, magnetic interaction and retardation in the μ-μ-interaction, the specific mass correction and the configuration interaction.     

Behaviour of the proton-proton total cross section at ISR energies in the reggeon calculus

We study the behaviour of σ^pp_T at ISR energies in the Reggeon calculus with a bare triple Pomeron coupling non vanishing at q² = 0. The parameters are determined from elastic and inclusive data. A sizable increase of σ_T with s can only be obtained when the bare Pomeron intercept is such that the renormalized Pomeron singularity is above one, in the forward direction.     

Unitarity,phenomenology, and the bare Pomeron

The possibility of utilizing the multifireball expansion and a bare Pomeron at $\text{α}\text{?}{}_{\mathrm{o}}\text{=0.85}$ as an approximation to a solution of the s-channel unitarity equations explicitly connecting 2-body and inelastic phenomenology is discussed. A scale for Pomeron renormalization effects is inferred.     

Theory of interacting Pomerons

The quantitative theory of Pomeron interaction is developed on the basis of strong coupling methods and ?-expansion. The theory is consistent with all unitarity conditions. At asymptotic energy total cross section increases as (ln s)^η, the multiplicity as (lns)^η+1, and diffraction cone shrinks as (lns)^?ν, where $\text{η ≈}\text{1}\text{6}\text{, ν ≈}\text{13}\text{21}$. At modern energy the theory gives small corrections to the Regge model.     

f-Dominance of the Pomeron in Reggeon Field Theory

A Reggeon Field Theory (RFT) which incorporates the Pomeron and thef-pole is presented. The constrains on the renormalization group β-functions imposed by thef-dominance of the Pomeron are derived. We show that these constrains are satisfied by the RFT at least up to third order in the coupling constants.     

The triple regge limit of diffractive dissociation in deep inelastic scattering

We derive, within perturbative QCD, a formula for the inclusive cross section of the diffractive dissociation of the deep inelastic photon γ^*+q→X+q in the triple Regge limits?M ²?Q ²?Λ ². We use the leading ln(s/M ², ln(M ²/Q ²) approximation and derive an, expression for the triple Pomeron vertex. The Pomeron above this vertex is found to be of higher order than the BFKL Pomeron. The resulting formula for the cross section is infrared finite. We show that the Abramovsky-Gribov-Kanchelli cutting rules are satisfied, and we discuss implications for the Pomeron structure function.     

Elastic peak and hadron size from at-channel viewpoint

A consistent approach for understanding hadron size and the elastic diffraction peak from at-channel viewpoint is presented. Our approach is orthogonal to that of ans-channel additive quark model. We consider the problem of determining the elastic amplitude as the shadow of multiparticle production in the framework of dual topological unitarization (DTU), when pion exchanges are included in addition to the usual vector-tensor exchanges which generate the Pomeron. The inclusion of pion exchange does not affect the Pomeron trajectory substantially, but plays an important role in the computation of Pomeron residues to external particles. Good agreement with elastic data as well as total cross sections is obtained.     

Constraint on anomalous 4ν interaction

The features of a hypothetical 4ν interaction considered as the possible reason for massive-neutrino instability required in the cosmological scenario that involve neutrino dark matter are discussed. New constraints on the 4ν-interaction constant G _χ are obtained: G _χ<(15–42)G _F for m _χ>G _Z (G _F is the Fermi constant of weak interaction; m _χ is the mass of the 4ν-interaction gauge boson, also known as χ boson; and m _Z is the Z-boson mass) and G _χ<(2.8–5.6)G _F for m _χ?G _Z . These constraints virtually rule out the 4ν interaction as a possible version of solution to the cosmological neutrino-instability problem.     

Strong interactions at high energies in the Reggeon approach

A brief survey of the development of Reggeon theory at ITEP and its application to hadron interactions at high energies is given. Basic properties of Regge poles and moving branch points and their relation to multiparticle hadron production are discussed. The one-pion-exchange model for describing exclusive and inclusive processes is considered. Basic properties of the model of quark-gluon strings and its applications are described. Reggeon field theory, its various asymptotic regimes, and its relation to diffractive phenomena are examined. The important role of Pomeron interactions in the theory of the supercritical Pomeron and their manifestations in the theory of deep-inelastic electron scattering and in heavy-ion collisions are discussed.     

Infrared behaviour and the bare Pomeron intercept in a Reggeon Field Theory including the Pomeron and thef-pole

An extension of the critical Reggeon Field Theory that includes both the Pomeron and thef-Reggeon fields is constructed. The quantum numbers of thef-Reggeon allows specific Reggeon-Pomeron couplings that have not been considered previously in standard works on secondary trajectories. We show the existence of a single fully stable fixed point among a total of 11 points. Unfortunately this point does not satisfy the factorization requirements imposed by thef-dominance of the Pomeron hypothesis and, in consequence, the critical Pomeron can not bef-dominated in aP+f model. We have also evaluated the value of the intercept of the bare critical Pomeron, using the method of integral representations of the propagators. The value obtained is clearly higher than the one previously obtained without thef-Pomeron interplay. With an adequate choice of the values of the bare coupling constants its value is in good agreement with the phenomenological one.     

Absorptive corrections to multihadron production and the unit intercept of the Pomeron

We propose a simple absorptive model for multihadron production in which the zero strength limit (g → 0) of the strong interactions is a vector theory, the Pomeron intercept is predicted to be at α_p=1 for any value of g, and the leading non-Pomeron singularity is at $\text{α}{}_{\mathrm{<mtext>R</mtext>}}\text{=1?}\text{g}\text{2}$. Themodel can accommodate correlations and incorporates the unitarity (Froissart) bound. Other properties of the model are discussed.