ω-radiation in high-energy nucleus-nucleus collisions

We study the bremsstrahlung of virtual ω-mesons due to the collective deceleration of nuclei at the initial stage of an ultrarelativistic heavy-ion collision. It is shown that electromagnetic decays of these mesons may give an important contribution to the observed yields of dileptons. Mass spectra of e + e − and µ + µ − pairs produced in central Au+Au collisions are calculated under some simplifying assumptions on the space-time variation of the baryonic current in a nuclear collision process. Comparison with the CERES data for 160 AGev Pb+Au collisions shows that the proposed mechanism gives a noticeable fraction of the observed e + e − pairs in the intermediate region of invariant masses. Sensitivity of the dilepton yield to the in-medium modification of masses and widths of vector mesons is demonstrated.

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“…ω-mesons. This leads to the following formulae for the momentum distribution of real ω-mesons emitted in a heavy-ion collision [12]…”

Section: Formulation Of the Modelmentioning

confidence: 99%

“…The ω * → 3π partial width is calculated assuming that it is proportional to the 3-pion phase space volume allowed by the kinematics [12]:…”

Section: Different Channels Of Virtual Meson Decay and Dilepton Produmentioning

confidence: 99%

Dilepton production by bremsstrahlung of meson fields in nuclear collisions

et al. 1998

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Vector meson radiation in relativistic heavy-ion collisions

Barmore

1997

Nuclear Physics A

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The sigma-omega model in mean-field approximation where the meson fields are treated classically, describes much of observed nuclear structure and has been employed to describe the nuclear equation of state up to the quark-gluon phase transition. The acceleration of the meson sources, for example, in relativistic heavy-ion collisions, should result in bremsstrahlung-like radiation of the meson fields. The many mesons emitted serve to justify the use of classical meson fields. The slowing of the nuclei during the collision is modeled here as a smooth transition from initial to final velocity. Under ultra-relativistic conditions, vector radiation dominates. The angular distribution of energy flux shows a characteristic shape. It appears that if the vector meson field couples to the conserved baryon current, independent of the baryonic degrees of freedom, this mechanism will contribute to the radiation seen in relativistic heavy-ion collisions. The possible influence of the quark-gluon plasma is also considered.Comment: 17 pages, 4 postscript figures. Uses elsart.sty and psfig.sty. Improved motivation and typographical corrections. Accepted for publication by Nuclear Physics

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Baryon-antibaryon pair production in time-dependent meson fields

et al. 1995

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Strong mean meson fields, which are known to exist in normal nuclei, experience a violent deformation in the course of a heavy-ion collision at relativistic energies. This may give rise to a new collective mechanism of the particle production, not reducible to the superposition of elementary nucleon-nucleon collisions. We study the baryon-antibaryon (NN, AA, . . . ) pair production under some simplifying assumptions about the space and time variation of meson fields in the nuclear collision process. The mutual deceleration of nuclei is described schematically by introducing the time-dependent relative velocity. For comparison the yield of NN pairs is also calculated within a convolution model assuming the same deceleration scenario. Due to the specific Lorentz structure, the vector meson field turns out to be more efficient for producing pairs than the scalar field. Within the perturbative approach we study two processes: the bremsstrahlung of a virtual meson and the fusion of two virtual mesons, both leading to the baryon-antibaryon final states. The calculated multiplicities of NN and AA pairs grow fast with the bombarding energy, reaching a saturation above the RHIC energy ( v s = 200A GeV). At lower energies the coherent production mechanism gives higher pair yields than predicted by microscopic cascade-like models. The rapidity spectra of antibaryons exhibit a characteristic two-hump structure which may serve as an observable signature of the bremsstrahlung mechanism. A strong sensitivity of the predicted yield to the baryon effective mass and the parameters characterizing the stopping power of nuclear matter is demonstrated.PACS number(s): 25.75.+r, 13.75.Cs, 13.85.Ni, 21.65.+f

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ω-radiation in high-energy nucleus-nucleus collisions

Cited by 4 publications

References 8 publications

Dilepton production by bremsstrahlung of meson fields in nuclear collisions

Dilepton production by bremsstrahlung of meson fields in nuclear collisions

Vector meson radiation in relativistic heavy-ion collisions

Baryon-antibaryon pair production in time-dependent meson fields

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