Subthreshold ρ0 photoproduction on 3He

M. A. Kagarlis, Z. Papandreou, G. M. Huber, G. J. Lolos, A. Shinozaki, E. J. Brash, F. Farzanpay, M. Iurescu, A. Weinerman, G. Garino, K. Maruyama, O. Konno, K. Maeda, T. Terasawa, H. Yamazaki, T. Emura, H. Hirosawa, K. Niwa, H. Yamashita, S. EndoK. Miyamoto, Y. Sumi, A. Leone, R. Perrino, T. Maki, A. Sasaki, J. C. Kim

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18 Citations (Scopus)

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≤1120 MeV) 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 m*ρ0=642±40, 669±32, and 682±56 MeV/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.

Original languageEnglish
Article number025203
Pages (from-to)252031-2520317
Number of pages2268287
JournalPhysical Review C - Nuclear Physics
Volume60
Issue number2
Publication statusPublished - 1999 Aug

ASJC Scopus subject areas

  • Nuclear and High Energy Physics

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