Exclusive diffractive processes and the quark substructure of mesons

Pichowsky, M. A.; Lee, T.-S. H.

doi:10.1103/physrevd.56.1644

Cited by 77 publications

(76 citation statements)

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“…In model studies [ 5] the linear increase is dominant for masses as low as that of the s-quark. The approach has also been extensively employed in the study of scattering processes, and one example is the calculation [ 9] of the cross section for the diffractive electroproduction of vector mesons. This application makes the striking prediction, confirmed by recent data, that although two-orders of magnitude smaller than the ρ-meson cross section at the photoproduction point, the ψ-meson cross section is equal to that of the ρ-meson at Q 2 = 15 GeV 2 , Fig.…”

Section: Phenomenological Applicationsmentioning

confidence: 99%

Deconfinement and hadron properties at extremes of temperature and density

Blaschke

Roberts

1998

Nuclear Physics A

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After introducing essential, qualitative concepts and results, we discuss the application of Dyson-Schwinger equations to QCD at finite T and µ. We summarise the calculation of the critical exponents of two-light-flavour QCD using the chiral and thermal susceptibilities; and an algebraic model that elucidates the origin of an anticorrelation between the µ-and T -dependence of a range of meson properties. That model also provides an algebraic understanding of why the finite-T behaviour of bulk thermodynamic properties is mirrored in their µ-dependence, and why meson masses decrease with µ even though f π and − qq increase. The possibility of diquark condensation is canvassed. Its realisation is uncertain because it is contingent upon an assumption about the quark-quark scattering kernel that is demonstrably false in some applications; e.g., it predicts the existence of coloured diquarks in the strong interaction spectrum, which are not observed. DYSON-SCHWINGER EQUATIONSThe Dyson-Schwinger equations (DSEs) provide a Poincaré invariant, continuum approach to solving quantum field theories. There are many familiar examples, among them: the gap equation in superconductivity; and the Bethe-Salpeter equation (BSE) and covariant Fadde'ev equation, which describe relativistic 2-and 3-body bound states. The DSEs are a system of coupled integral equations and a truncation is necessary to obtain a tractable problem. The simplest truncation scheme is a weak-coupling expansion, which generates every diagram in perturbation theory. Hence, in the intelligent application of DSEs to QCD, there is always a tight constraint on the ultraviolet behaviour. That is crucial in extrapolating into the infrared, and in developing uniformly valid, efficacious, symmetry-preserving truncations.The task of development is not a purely numerical one, and neither is it always obviously systematic. For some, this last point diminishes the appeal of the approach. However, with growing community involvement and interest, the qualitatively robust results and intuitive understanding that the DSEs can provide is becoming clear. Indeed, those * A combined summary of two presentations,

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Section: Phenomenological Applicationsmentioning

confidence: 99%

Deconfinement and hadron properties at extremes of temperature and density

Blaschke

Roberts

1998

Nuclear Physics A

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“…In the diffractive region of high energies and low momentum transfers, this reaction is dominated by vector meson production generated by Pomeron exchange, and its theory is quite firm [1][2][3]. In the lower energies, the P -wave π + π − photoproduction was described in terms of the t-channel exchange of Reggeons [4,5].…”

Section: Introductionmentioning

confidence: 99%

Tensor meson photoproduction as a final state interaction effect

Bibrzycki

Kamiński

2013

Phys. Rev. D

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The model is presented to describe the f2(1270) meson photoproduction as a result of pionpion interactions in the final state. Treating tensor mesons as objects dynamically created due to final state interactions is a convenient and straightforward way to employ data from ππ scattering like phase shifts and inelasticities for description of (photo)production reactions while retaining proper analytical structure of amplitudes, two particle unitarity and crossing symmetry. The model presented here can provide experimentally testable quantities like differential cross sections and ππ mass distributions as well as the strengths of partial waves corresponding to various f2(1270) helicities which are essential for partial wave analyses. It can also be used to compute moments of angular distribution and spin density matrix elements where partial wave interference effects are important.PACS numbers: 13.60. Le, I. INTRODUCTIONDescription of the spectrum of resonances observed in the ππ (and KK) system and excited in photon nucleon collisions is one of the most challenging problems of hadron spectroscopy. In the diffractive region of high energies and low momentum transfers, this reaction is dominated by vector meson production generated by Pomeron exchange, and its theory is quite firm [1][2][3]. In the lower energies, the P -wave π + π − photoproduction was described in terms of the t-channel exchange of Reggeons [4,5]. Attempts have also been made to include the intermediate nucleon resonances through various s-channel and u-channel mechanisms [6][7][8]. For the photoproduction of the S-wave and D-wave resonances, the situation is not clear both experimentally and theoretically. Because of small photoproduction cross sections, they are very difficult to observe in mass distributions. So the method of choice is to analyze the interference patterns of the weak S-and D-wave amplitudes with dominant P -wave amplitude. The partial wave interference can be conveniently analyzed with moments of pion angular distribution or spin density matrix elements. Such an approach was employed in a recent analysis of the reaction γp → π + π − p performed by the CLAS group at Jefferson Laboratory, where the first observation of f 0 (980) photoproduction was reported [9]. The same experiment saw the f 2 (1270) signal, which previously was also observed by Hermes experiment at Deutsches ElektronenSynchrotron using similar methods [10]. The apparent sensitivity of moments analysis in the search for a sig- * Corresponding author.lukasz.bibrzycki@ifj.edu.pl † Corresponding author.robert.kaminski@ifj.edu.plnal of rare resonances has a reverse, however, namely, that it requires proper accounting for all relevant production mechanisms. Nevertheless this method has been successfully employed to extract the f 0 (980) and a 0 (980) from the photoproduced KK spectrum [11] and f 0 (980) from the π + π − spectrum [12]. The amplitude of f 2 (1270) photoproduction is the necessary ingredient in order to properly describe the partial wave interference pa...

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“…The coupling β 0 =2.0 GeV −1 was deduced [2] from pp scattering, while β 0 =2.35 GeV −1 was obtained [9] from an analysis of πp elastic scattering at high energies. The cut-off µ 0 can be fitted to photoproduction data.…”

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confidence: 99%