Subthreshold ρ0 photoproduction on 3He

M. A. Kagarlis et al. (TAGX Collaboration)
Phys. Rev. C 60, 025203 – Published 9 July 1999
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Abstract

A large reduction of the ρ0 mass in the nuclear medium is reported, inferred from dipion photoproduction spectra in the 1 GeV region, for the reaction 3He(γ,π+π)X with a 10% duty factor tagged-photon beam and the TAGX multiparticle spectrometer. The energy range spanned (800<~Eγ<~1120MeV) lies mostly below the free-ρ0 production threshold, a region which is believed to be sensitive to modifications of light vector-meson properties at nuclear-matter densities. The values of the ρ0 mass extracted from the Monte Carlo fitting of the data were mρ0*=642±40, 669±32, and 682±56MeV/c2 for Eγ in the 800–880, 880–960, and 960–1040 MeV regions, respectively. These values were independently corroborated in a qualitative fashion by a measured, assumption-free, kinematical observable. This mass shift, far exceeding current mean-field-driven theoretical predictions, may be suggestive of a nucleonic source of modification or of a bound state in the nuclear mean field.

  • Received 30 November 1998

DOI:https://doi.org/10.1103/PhysRevC.60.025203

©1999 American Physical Society

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Vol. 60, Iss. 2 — August 1999

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