Abstract
A large reduction of the mass in the nuclear medium is reported, inferred from dipion photoproduction spectra in the 1 GeV region, for the reaction with a 10% duty factor tagged-photon beam and the TAGX multiparticle spectrometer. The energy range spanned lies mostly below the free- 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 mass extracted from the Monte Carlo fitting of the data were and for 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