Pomeron factorization in general dual models

We demonstrate that in each ghost-free dual model with one minor restriction, there exists a critical dimensionality of space-time in which the pomeron singularity becomes a factorizable Regge pole. In each model when this dimensionality is chosen, the pomeron emerges with twice the intercept and half the slope of the leading secondary (f) trajectory. We explicitly construct the pomeron propagator and the operator coupling the pomeron to the reggeon sector for the general dual model, including the lower-lying negative-G-parity pomeron in the Neveu-Schwarz model. Gauge identities and physical states in the pomeron sector are also investigated. In all of the dual models the pomeron form factors exhibit a generalized f dominance and modified Wu-Yang behavior.     

Inelastic shadow correction for hadron-deuteron elastic scattering

We calculate the inelastic screening effect in hadron-deuteron elastic scattering, using a new technique. The main idea is to calculate explicitly the complex cut integral in the M² plane, using an ansatz for the asymptotic behaviour of the six-point amplitude. In the hypothesis of pomeron dominance that contribution is real and small.     

Regge cuts and large-|t| pp scattering

It is shown that recent measurements of the large-|t| pp elastic-scattering differential cross section at FNAL and CERN-ISR agree with earlier predictions based on the dominance of a pomeron pole(P) with αp(t) = 1.067 + 0.10 t, and a P ? P cut, out to the largest measured |t| values (12 GeV²). Some of the problems raised by this success are discussed.     

A one-dimensional approximation for the pomeron in the dual unitarity scheme

Using a one-dimensional approximation, the pomeron in the dual unitarity scheme is examined analytically in a multiperipheral cluster model. Clusters have negative short range correlations due to the t_min effect. In dual models, the pomeron has a crossing odd part, especially in B$\text{B}$ and BB scattering. By taking all reggeon loops into account, we show explicitly in our approximation that the crossing-odd part has only lower-lying singularities in the j-plane (typically complex poles with $\text{Re}\text{α?0.2}$) whereas the crossing-even part has the leading singularity at j = α_P (we imposed α_P = 1). The dual unitarity scheme leads to a modified version of the f-dominance of the pomeron. We calculate the SU(3) breaking of the pomeron due to the SU(3) breaking among Regge trajectories without additional assumptions on the SU(3) property of the pomeron.     

The problem of the relation between double pomeron exchange in inclusive and exclusive experiments

The pionization region of the inclusive single-particle spectrum is accounted for by double pomeron exchange in the absorptive part of a six-point amplitude. In this paper a multiperipheral model for the six-point amplitude with double pomeron exchange is used for continuation by crossing and analyticity to the physical region of the exclusive two particle → four particle production process. The cross section for π^? p → π^?(π⁺π^?)p in the double-Regge region is then calculated and compared with the experimental analysis of Lipes, Zweig and Robertson which sets an upper bound to the strength of the double pomeron exchange coupling. This upper bound, coupled with the model for continuation to the inclusive cross section, is shown to give too small a magnitude for the double pomeron exchange in the pionization region. Further avenues for investigation are discussed.     

Search for glue balls in a pomeron pomeron scattering experiment

The exclusive reactionpp→ppπ⁺ π^? has been studied using the SFM spectrometer at ISR energies of \(\sqrt s = 24\) and 63 GeV. The cross section in the double pomeron exchange region defined by |x _p |>0.9, |y _π |<1 is 28±6, 23(+13, ?6) and 29(+29, ?10)μb, respectively. The ππ mass spectrum is dominated by an 1/m _ππ ² part, as expected for pomeron pomeron scattering. In addition, thef(1, 270) resonance is clearly distinguished. There are no further resonance signals, which could be assigned to glueball candidates expected in the 1,000 MeV region. Compared to photon photon scattering, the ratio of continuum tof-resonance production cross sections is significantly larger in pomeron pomeron scattering.     

A basic guide for the glueball spotter

After a brief review of the theoretical and phenomenological motivation for the existence of gluonic resonances, we examine the expected properties of such states, and consider possible tests for their presence in the hadronic spectrum below 1.5 GeV in mass. The scalar mesons can be classified as an approximately ideally mixed nonet with an additional isoscalar, the S¹, with all the expected properties of a scalar glueball. It is suggested that the η′ contains a large proportion of glue as well as strange quarks and that, if the E(1420) is not a pseudoscalar, two further pseudoscalars await discovery in the low-lying meson spectrum. The pomeron, a narrow resonance in the ππ D-wave, must be found with a mass around or slightly below that of the S¹. If the pomeron has a daughter vector glueball which, as has been argued, is fairly close to the φ mass, then it should also have a mother 3^?? glueball with a similar mass. The D(1285) may well be a 2^?+ glueball.     

Photoproduction of heavy vector mesons: The ϒ(9.4)

The predictions based on the vector meson dominance model (VMD) and the tensor-coupled pomeron for the photoproduction of heavy vector mesons are revised, and corrections to the model are proposed as suggested by the experimental data for the light vector mesons and the ψ (3100). In particular, the string model is used to predict the Regge trajectories of the heavy vector mesons (ψ, ?, …) which results in a correction to the predicted heavy vector meson-nucleon total cross section in agreement with the ψ data. The q² dependence of VMD is also discussed. The cross section for the photoproduction of the ? (9.4) is estimated within this framework.     

Asymptotic-planarity prediction of a pomeron-like unnatural parity trajectory

The asymptotic-planarity argument that explains the pomeron as a cylinder-shifted f, when applied to unnatural parity, predicts near t = 0 a high-lying small-slope H trajectory, with the corresponding I = 0, 1⁺, C = ? meson mass near 1 GeV. H couplings near t = 0 will be close to pure SU₃ singlet.     

Pomeron structure function and diffraction dissociation of virtual photons in perturbative QCD

We study scaling properties of the diffraction dissociation of virtual photons in a deep inelastic scattering. We concentrate on the total diffraction dissociation rate, diffraction excitation mass spectrum and the pomeron structure function to the lowest order in perturbative QCD. We calculate the valence structure function and the strangeness and charm content of the pomeron and estimate the ocean structure function using the pomeron factorization property. We find that quarks carry ≈ 10% of pomeron's momentum. Differential cross section of the (virtual) photon-pomeron scattering is found to exhibit features typical of the hadronic two-body reactions, supporting a treatment of the Pomeron as a particle, whereas the flavor dependence of structure functions does not support the particle treatment of the pomeron. Diffraction dissociation of photons is predicted to make ≈ 15% of the total deep inelastic scattering rate at smallx and largeQ ². Detailed predictions for the mass spectrum and angular distribution of jets produced on the valence component of the pomeron are presented.     

The content of unitarity constraints on a pomeron pole of intercept one

We present a consistent picture of a pomeron pole with intercept one, together with its cuts, which evades the decoupling arguments. We use the reggeon cut discontinuity formulae to introduce Gribov's reggeon calculus as an exact solution of multiparticle t-channel unitarity. We show how, within the calculus, two-pomeron iterations of a singular kernel can be responsible for the zero in the triple-pomeron vertex. Using the concept of a bare pomeron pole as a multiperipheral production process which is subsequently renormalised by other effects, we apply the reggeon calculus analysis to inclusive cross sections. We find that the inclusive sum rule decoupling arguments are avoided because of the addition of enhanced absorptive corrections to the conventional Regge pole contributions. However, we show that in this picture the combined pole and two-pomeron cut contribution to the total cross section factories to order (ln s)^?2.We also show that, when the correct helicity structure of the pomeron is taken into account, the s-channel unitarity condition for pomeron scattering amplitudes does not lead to any serious decouplings.     

The asymptotic behaviour of a non-planar orientable dual two-loop amplitude

Both the s- and t-channel asymptotic behaviour of a non-planar orientable two-loop four-point amplitude are investigated. A factorized expression for the iterated pomeron singularity, contributing to the s-channel behaviour, has been obtained with an internal pomeron blob closely related to the off-shell “propagator” of Cremmer and Scherk. These results suggest an interpretation in terms of a renormalization scheme of the pomeron. For t-channel asymptotics Regge-cut behaviour arises. Remarks are also made for the corresponding six-point case. Direct expansions of all the relevant functions in terms of group parameters as well as a thorough study of Jacobi's transformation in the double parabolic limit are of crucial importance to prove these results.     

A generalized reggeon field theory incorporating hard scattering effects

Guided by the parton interpretation of RFT and by QCD, we propose an RFT where the pomeron field depends both onb and onQ ², the bare propagator describing an inhomogenous random walk inb and in lnQ ². Here,Q ² measures the virtuality of the inelastic processes which generate the pomeron exchange amplitude as their shadow. The asymptotic behaviour of such a theory should be different from that of standard RFT, at and above the critical point. Arguments are given in favour of a supercritical pomeron.     

Reggeon phases and the dual bootstrap program

Analyticity requirements lead to complex Regge vertices in multiparticle production amplitudes. Their effect is discussed within a dual, unitary and exchange-degenerate multi-Regge model. A resulting complex Regge vertex is incorporated in fixed-t model calculations of the reggeon bootstrap and the topological pomeron. The bootstrap condition for particle-particle scattering is unaffected but new j-plane singularities appear in Regge-Regge scattering amplitudes. The pomeron and reggeon intercepts determine the two parameters of our Regge vertex and admit two possible solutions: one is close to the naive phase rule (real vertex) and the other is complex and leads to a high lying non-leading pole in the pomeron channel.     

Characteristics of double-pomeron exchange

A detailed kinematic study is made of the cross section for double-pomeron exchange. We consider reactions of the type a + b → c + d + (h₁ + h₂ + …) where a → c and b → d are quasi-elastic transitions with limited momentum transfer and (h₁ + h₂ + …) is a centrally produced hadron cluster. The dependence of the cross section on the relative azimuthal angle φ between the final hadrons c and d provides an important test for double-pomeron exchange. We calculate this φ-dependence for all cases of interest, using a model in which pomeron exchange is represented by an effective current-current interaction. For limited momentum transfer, where the pomeron spin is nearly equal to one, this model is equivalent to Reggeized pomeron exchange. We give a complete formalism for the partial-wave analysis of the double-pomeron reaction ab → cd + h₁₂ which differs from the one given by Rushbrooke and Webber. Furthermore, we discuss the two-pomeron vertex, and the construction of detailed and realistic models for double-pomeron reactions.     

Models for the pomeron and low energy K+p scattering

Using a simple s-channel unitarity model for the pomeron, abstracted from a number of more ambitious schemes, we compute the pomeron contribution using low-energy data in K⁺p scattering. The agreement with experiment obtained is qualitatively fair but in detail substantial discrepancies appear. Possible reasons for these discrepancies and suggestions for their future investigation are presented.     

The bootstrap condition for many reggeized gluons and the photon structure function at lowx andN c����

The bootstrap condition is generalized ton reggeized gluons. As a result it is demonstrated that the intercept generated byn reggeized gluons cannot be lower than the one forn=2. Arguments are presented that in the limitN _c???? the bootstrap condition reduces then gluon chain with interacting neighbours to a single BFKL pomeron. In this limit the contribution fromn gluons leading at high energies corresponds ton/2 non-interacting BFKL pomerons (then/2 pomeron cut). The sum overn leads to a unitary??*?? amplitude of the eikonal form.     

Evolution of high-mass diffraction from the light quark valence component of the Pomeron

We analyze the contribution from excitation of the \((q\bar q)(f\bar f), (q\bar q)g_1 \cdots g_n (f\bar f)\) Fock states of a photon to high-mass diffraction in DIS. We show that the large-Q² behavior of this contribution can be described by DLLA evolution from the nonperturbative \(f\bar f\) valence state of the pomeron. Although of higher order in pQCD, the new contribution to high-mass diffraction is comparable to that from the excitation of the \(q\bar qg\) Fock state of the photon.