The spectral function in a relativistic resonance model

Post, M.; Leupold, Stefan; Mosel, U.

doi:10.1016/s0375-9474(00)00613-8

Cited by 77 publications

(98 citation statements)

References 51 publications

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“…However, we have rather different shapes for the neutron showing a bump structure in the backward scattering region −1 ≤ cos θ ≤ −0.5. We verified 2 We note that there have been several methods to remedy this unitarity breaking problem including the Blatt-Weisskopf penetration factor and introducing phenomenological off-shell parameters [19,30,31,32].…”

Section: /2mentioning

confidence: 58%

η-meson photoproduction andN* resonances

Choi

Nam

Kim

2008

J. Phys. G: Nucl. Part. Phys.

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We investigate the η photoproduction using the effective Lagrangian approach at the tree level. We focus on the new nucleon resonance N * (1675), which was reported by the GRAAL, CB-ELSA and Tohoku LNS, testing its possible spin and parity states theoretically (J P = 1/2 ± , 3/2 ± ). In addition, we include six nucleon resonances, D 13 (1520), S 11 (1535), S 11 (1650), D 15 (1675), P 11 (1710), P 13 (1720) as well as the possible background contributions. We calculate various cross sections including beam asymmetries for the neutron and proton targets. We find noticeable isospin asymmetry in transition amplitudes for photon and neutron targets. This observation may indicate that the new resonance can be identified as a non-strangeness member of the baryon antidecuplet.

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Section: /2mentioning

confidence: 58%

η-meson photoproduction andN* resonances

Choi

Nam

Kim

2008

J. Phys. G: Nucl. Part. Phys.

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“…To make further progress, however, we need some phenomenological input. In [12,14,15] the influence of baryonic resonances on the in-medium properties of the ρ-meson were thoroughly discussed. It is shown there that the most important in-medium change for ρ-mesons at rest is caused by the excitation of the D 13 (1520) resonance (see also [16]).…”

Section: Hadronic In-medium Changes At Large Ncmentioning

confidence: 99%

QCD sum rules at finite density in the large- limit: the coupling of the ρ-nucleon system to the

Leupold¹,

Post²

2005

Nuclear Physics A

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QCD sum rules are studied for the vector-isovector current at finite baryon density in the limit of large number of colors Nc. For the condensate side it is shown that in this limit the four-quark condensate factorizes also for the finite density case. At the hadronic side the medium dependence is expressed in terms of the current-nucleon forward scattering amplitude. Generalizing vector meson dominance we allow for a direct coupling of the current to the nucleon as well as a coupling via the ρ meson. We discuss the Nc dependence of (a) modifications of the pion cloud of the ρ meson, (b) mixing with other mesons (in particular a1 and ω) and (c) resonance-hole excitations R N −1 . We show that only the last effect survives in the large-Nc limit. Saturating the sum rules with a simple hadronic ansatz which allows for the excitation of the D13(1520) we determine the coupling of the latter to the ρ-nucleon and the photon-nucleon system. These couplings are hard to determine from vacuum physics alone.

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“…In such a way, the uncertainties of ReT V N become milder since m V (n) is then mainly determined by the QSR. Neglecting the energy dependence of ReT V N one discards a potentially rich structure of S (V ) , such as, for instance, a double peak structure obtained in [12] for the ω meson or in [11] for the ρ meson. Afterwards the importance of ReT V N is checked.…”

Section: Finite Width Effectsmentioning

confidence: 99%

Finite-width QCD sum rules for ρ and ω mesons

Kämpfer

Zschocke

2004

Progress in Particle and Nuclear Physics

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We present a combined analysis of the in-medium behavior of ρ and ω mesons within the Borel QCD sum rule taking into account finite widths. IntroductionThe experiments at the High-Acceptance Di-Electron Spectrometer HADES [1] are aimed at verifying predictions of the behavior of light vector mesons in nuclear matter. Due to the decay channel V → e + e − a measurement of the escaping di-electrons can reveal directly the properties of the parent mesons, V = ρ, ω, · · ·, since the interaction probability of the e ± with the ambient strongly interacting medium is small.In relativistic heavy-ion collisions temperature effects play an important role, which also cause a change of the properties of vector mesons. Indeed, the experiments of the CERES collaboration at the CERN-SPS [2] can only be explained by assuming strong medium effects, in particular for the ρ meson (cf. [3,4] and further references therein). This seems to be confirmed at higher beam energies, as delivered by the Relativistic Heavy Ion Collider, since the ρ meson, as measured via the π + π − decay channel, suffers some modification [5]. In contrast, in heavy-ion collisions at typical SIS18 energies, i.e., at beam energies around 1 AGeV, the in-medium behavior of vector mesons in compressed nuclear matter can be studied, where temperature effects are small and may be neglected. Complementary to heavy-ion collisions one can seek for in-medium modifications in reactions of hadronic projectiles [6] or real and virtual photons [7] at nuclei, as already at nuclear saturation density sizeable modifications of vector mesons are predicted.There exists a vastly extended literature on the in-medium modification of hadrons. We mention here only the Brown-Rho scaling hypothesis, according to which a mass shift of a vector meson is directly interrelated to a change of the chiral condensate [8], and the vector manifestation [9], the effective Lagrangian approach [10], purely hadronic approaches [11,12], and QCD sum rules [13,14,15,16]. QCD sum rules [17] follow the idea of duality (cf. [18]) by relating quantities expressed by partonic (quark and gluon) degrees of freedom with hadronic observables. We take here the attitude to assume that the partonic quantities are given and examine the QCD sum rule to elucidate the in-medium change of the ρ and ω meson on a common footing. The corresponding current operators, expressed by the interpolating quark field operators u and d have the form J ρ µ = 1 2 (ūγ µ u−dγ µ d) and J ω µ = 1 2 (ūγ µ u+dγ µ d), * Dedicated to the memory of O.P. Pavlenko

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The spectral function in a relativistic resonance model

Cited by 77 publications

References 51 publications

η-meson photoproduction andN* resonances

η-meson photoproduction andN* resonances

QCD sum rules at finite density in the large- limit: the coupling of the ρ-nucleon system to the

Finite-width QCD sum rules for ρ and ω mesons

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