Proton Diffractive Dissociation Research Articles

Investigation of Single Proton Dissociation

We consider the single proton diffraction dissociation at low missing masses focusing on the interplay between diffractive processes and resonance production. The model incorporates the concept of duality, where the observed cross sections are explained by both smooth background processes and discrete resonance contributions. At low missing masses MX, this approach leverages the Regge proton trajectory to account for the role of resonances in the cross section. Recent experimental data are used to refine model parameters, enhancing the accuracy of predictions for the differential cross section behavior in the resonance region.

Regge Models of Proton Diffractive Dissociation Based on Factorisation and Structure Functions.

Recent results by the authors on proton diffractive dissociation (single, double and central) in the low-mass resonance region with emphasis on the LHC kinematics are reviewed and updated. Based on the previous ideas that the contribution of the inelastic proton–Pomeron vertex can be described by the proton structure function, the contribution of the inelastic Pomeron–Pomeron vertex appearing in central diffraction is now described by a Pomeron structure function.

Diffractive dissociation re-visited for predictions at the LHC

We describe the formalism, and present the results, for a triple-Regge analysis of the available pp and p\bar{p} high-energy data which explicitly accounts for absorptive corrections. In particular, we allow for the gap survival probability, S^2, in single proton diffractive dissociation. Since for pp scattering the value of S^2 is rather small, the triple-Pomeron vertex obtained in this analysis is larger than that obtained in the old analyses where the suppression caused by the absorptive corrections was implicitly included in an effective vertex. We show that the bare triple-Pomeron coupling that we extract from the pp and p\bar{p} data is consistent with that obtained in a description of the gamma p -> J/psi + Y HERA data. The analyses of the data prefer a zero slope, corresponding to the small size of the bare vertex, giving the hope of a smooth matching to the perturbative QCD treatment of the triple-Pomeron coupling.

Triple Pomeron and proton diffraction dissociation

We consider proton diffraction dissociation in the dipole Pomeron model, where the Pomeron is represented by a double pole in the $J-$plane, and show that unitarity can be satisfied without decoupling of the triple Pomeron vertex. Differential and total diffractive cross sections for the reaction $\bar{p}+p \to \bar{p}+X$ are analyzed and reproduced in this model.

Search for exotic baryons with hidden strangeness in diffractive production processes

Experimental results of the SPHINX Collaboration on studying proton diffractive production processes are presented. Evidences for new baryon states with masses ≳2 GeV were obtained in hyperon-kaon effective mass spectra in several reactions. Unusual properties of these massive states (small enough decay widths, large branching ratios for their decays with strange particles in final states) make them serious candidates for cryptoexotic pentaquark baryons with hidden strangeness |qqqs s ̄ 〉 . New results for these states are presented here, as well as recent data on large violation of the OZI rule in proton diffractive dissociation.

J/ψ Production at HERA

In this report we summarize the experimental situation about J/ψ production at the HERA collider. Data will be shown on elastic, on proton diffractive dissociation and on inelastic production mechanisms. The experimental results will be compared with the existing theoretical models.

Proton dissociative $\rho$ and elastic $\phi$ electroproduction at HERA

The electroproduction of rho mesons with proton diffractive dissociation for Q^2 > 7 GeV^2 and the elastic electroproduction of Phi mesons for Q^2 > 6 Gev^2 are studied in e^+ p collisions at HERA with the H1 detector, for an integrated luminosity of 2.8 pb-1. The dependence of the cross sections on P_t^2 and Q^2 is measured, and the vector meson polarisation obtained. The cross section ratio between proton dissociative and elastic production of rho mesons is measured and discussed in the framework of the factorisation hypothesis of diffractive vertices. The ratio of the elastic cross section for Phi and rho meson production is investigated as a function of Q^2.

Factorization properties of the diffraction dissociation of longitudinal photons

We develop the pQCD description of the diffraction dissociation (DD) of longitudinal protons. We demonstrate that the longitudinal diffractive structure function does not factor into the flux of pomerons and the partonic structure function of the pomeron, thus defying the usually assumed Regge factorization. In contrast to DD of the transverse photons, DD of the longitudinal photons is strongly peaked at β = 1. We comment on duality properties of DD in deep inelastic scattering.

Realistic hadronic matrix element approach to color transparency.

Color transparency occurs if a small-sized wave packet, formed in a high momentum transfer process, escapes the nucleus before expanding. The time required for the expansion depends on the masses of the baryonic components of the wave packet. Measured proton diffractive dissociation and electron deep inelastic scattering cross sections are used to examine and severely constrain the relevant masses. These constraints allow significant color transparency effects to occur at experimentally accessible momentum transfers.

Experimental results on proton diffractive dissociation

Properties of proton diffractive dissociation have been investigated for four-prong final states in proton-proton reactions at 360 GeV/c, in particular forpp→ppπ +π− mπ 0(m=0,1,2). Mass distributions and decay angular distributions are given. The decay of the diffractive system is seen to be very anisotropic, and largep T is suppressed at higher masses. It is found that the “pomeron” couples with a single valence quark of the incident proton, but indications for a diquark-pomeron coupling are also found. Similarities with fragmentation in lepton-hadron deep inelastic scattering are underlined.

Study of polarized proton diffraction dissociation in the reactionp↑p→pπ+π−p at 11.75 GeV/c

We present angular distributions and, for the first time, single-spin correlations in the diffraction-dissociation reaction ${p}_{\ensuremath{\uparrow}}$p\ensuremath{\rightarrow}p${\ensuremath{\pi}}^{+}$${\ensuremath{\pi}}^{\mathrm{\ensuremath{-}}}$p, for small momentum transfers between the polarized beam and the (p${\ensuremath{\pi}}^{+}$${\ensuremath{\pi}}^{\mathrm{\ensuremath{-}}}$) system, at 11.75 GeV/c. The only structures seen in our 2\ifmmode\times\else\texttimes\fi{}${10}^{6}$-event sample turn out to be the well-known threshold enhancement in \ensuremath{\Delta}\ensuremath{\pi} and the N(1700), which appears to involve both \ensuremath{\Delta}\ensuremath{\pi} and N(1520)\ensuremath{\pi}. The production process exhibits a slope-mass correlation and patterns of helicity nonconservation seen in higher-energy diffractive processes. We also see evidence for a complex helicity structure in the spin correlations. We show that the threshold enhancement is unambiguously S wave in character, while the N(1700) appears to be a mix of states. The overall similarities between our data and those at higher energies, together with the rich structures contained in the angular-distribution correlations (we measure 315 joint moments in each mass and t bin), make our data base highly relevant for theoretical analysis of exclusive diffraction.

Observation of longitudinal event structure in proton diffractive dissociation at the ISR

We study the internal structure of a forward-going pπ + π − π + π − system, with invariant mass in the range 2.5-4 GeV, produced through diffractive dissociation of a beam proton at the ISR. The shape of the system, as seen in its center-of-mass, deviates strongly from isotropic phase space and possesses, rather, a longitudinal structure with a major axis along the incoming proton direction. The final state proton momentum is aligned in the direction of the incoming proton, an effect which becomes more pronounced with increasing diffractive mass.

Unusual production features of isoscalar mesons in proton diffractive dissociation at the CERN-ISR

D(1285) and E/iota(1422) are observed in the diffractive dissociation process, pp→(pK 0K +-π ±)p, with √ s=63Gev. The D(1285) is produced with dominant ±1 helicity. Several unusual features of the data suggest that the mesonic states result from gluonic interactions in the collision.

Diffractive proteon fragmentation in 16, 32, and 110 GeV/cK − p interactions and the diffractive production of heavy quarks $$(s\bar s,c\bar c)$$

The inclusive proton diffraction dissociation cross sections in 16, 32, and 110 GeV/cK−p interactions are determined from the spike nearx=1 in the inclusive negative particle spectra and are compared to those obtained inK−p interactions using other selection methods at various energies. The same procedure is applied to events containing aV0 in order to obtain the cross section for diffractive\(s\bar s\) production. While the total cross section for proton diffraction is found to be approximately constant in the energy range studied here, proton diffraction yielding an\(s\bar s - pair\) is found to increase significantly. In particular it is almost constant at 85 μb forΛ0 and Σ production but for\(NK\bar K\) it rises from zero at 16 GeV.c to about 200 μb at 110 GeV/c. From the result for\(s\bar s\) diffractive production an estimate for the\(c\bar c\) diffractive production cross section of approximately 1–10 μb at 110 GeV/c is obtained.

A test of the validity of the extraction ofK ? ?? scattering in the reactionK ? p ?K ????++ in the framework of the one-pion-exchange model

In a study of the reactionK−p →K-π−π+p at 10 and 16 GeV/c the one-pion-exchange model was tested by attempting to extract on this basis the angular distributions for π+p elastic scattering and comparing to real π+p scattering. In thes-channel frame high order moments already appeared at relatively low mass. In general there are large discrepancies in both thes- andt-channel frames which remain after extrapolation to the pion pole and are related toQ− production. The structure of the decay angular distribution of theK−K- π- system produced in association with Δ++ is dominated by proton diffractive dissociation into Δ++π-.

Coherent proton diffraction dissociation on helium from 46 to 400 GeV

Inclusive coherent proton diffraction dissociation on helium has been measured in the four-momentum transfer and missing-mass region 0.04

Inclusive single and double diffractive dissociations inK + p interactions at 32 GeV/c

We study single and double inclusive diffractive production in a 32 GeV/c K+p experiment in MIRABELLE at the Serpukhov accelerator. From reactionsK+p→K++X+ andK+p→X++p we determine the total proton and kaon single diffractive dissociation cross sections\(\sigma (p\xrightarrow{{K^ + }}p_D ) = 0.90 \pm 0.12 mb\) and\(\sigma (K^ + \xrightarrow{p}K_D^ + ) = 0\). 90±0.17 mb, respectively. In either case the only notable contributions come from dissociations into 1 and 3 charged particles. Kaon dissociation exhibits a pronounced slope-mass correlation. The search for double diffractive production in reactionsK+p→(K+π−π+)+X+ andK+p→(pπ+π−)+X+ leads in either case to an estimated total double diffractive cross section σ(K+p→K D + pD) of ≅220 μb. The double dissociation differential cross section exhibits a large slope of ≅10GeV−2 in the nearthreshold mass region, rapidly decreasing to ≅4 GeV−2 with increasing excitation mass. At our c.m. energy\((\sqrt s \simeq 8 GeV)\) the ratio σinel dif/σel is 0.85±0.10, the total diffractive cross section σdif≡σel+σinel dif=4.41±0.24 mb and the fraction σdif(K+p)/σtot(K+p) is 25±2%. TheK+ andK− diffractive excitation mass spectra, differential cross sections and total diffractive cross sections are very similar for both single and double dissociations.

Analysis of single and coherent nucleon diffraction dissociation at ISR energies

We present the analysis of a combined measurement of neutron and proton diffraction dissociation into (Nπ) and (Nππ) final states, both on proton and deuteron targets. The experiment was performed at the CERN Intersecting Storage Rings with the Split Field Magnet detector using proton and deuteron colliding beams. Mass spectra and decay angular distributions are compared with the predictions of a dual-reggeized Deck model. Strong decay angular correlations are observed in all cases. Pronounced structures observed in the differential cross sections of the coherent diffractive processes for small produced masses are interpreted in terms of constructive interference between the single- and double-scattering terms in a Glauber analysis. These interference effects cannot be reproduced by a central dissociation mechanism and require a peripheral description of the elementary nucleon-nucleon diffractive production amplitudes.

Diffraction Dissociation of High-Energy Protons on Hydrogen and Deuterium Targets.

Diffraction Dissociation of High-Energy Protons on Hydrogen and Deuterium Targets.

Diffraction Dissociation of High-Energy Protons on Hydrogen and Deuterium Targets

We report results from a measurement of the inclusive processes pp ..-->.. Xp and pd ..-->.. Xd in the range 5 < M/sub x//sup ts2//s < 0.1, 0.01 9 or approx. = 0.1 (GeV/c)/sup 2/, and incident proton momenta of 65, 154, and 372 GeV/c. Both pp and pd data show an exponential t dependence and a dominant 1/M/sub x//sup ts2/ behavior for M/sub x//sup ts2//s 9 or approx. = 0.05. By comparing pp and pd data we test factorization and, using the Glauber model, we measure the XN total cross section, sigma/sub X N/ = 43 +- 10 mb.