2000/04/18 by Nevio Grion
Physics and Astronomy · #nucl-ex
published as Hadrons in Dense Matter, Proc. of the International Workshop XXVIII on Gross Properties of Nuclei and Nuclear Excitations, Hirschegg, Austria, January 16-22, 2000 · 10 pages, 5 figures, PS format. Talk presented at the International Workshop XXVIII on Gross Properties of Nuclei and Nuclear Excitations, Hirschegg, Austria, January 16-22, 2000
arxiv created 2000/04/18 · arxiv updated 2009/12/01
The pion-production π+ A → π+π± A' reactions were studied on nuclei 2H, 12C, 40Ca and 208Pb at a pion energy of Tπ+=283 MeV using the CHAOS spectrometer. The experimental results are reduced to differential cross sections and compared to both theoretical predictions and reaction phase space. Near the 2mπ threshold pion pairs couple to (ππ)I=J=0 when produced in the π+→ π+π- reaction channel. The \cal CππA ratio between the π+π± invariant masses on nuclei and on the nucleon is also presented. The marked near-threshold enhancement of \cal Cπ+π-A is consistent with theoretical predictions addressing the partial restoration of chiral symmetry. On the opposite, nuclear matter weakly influences \cal Cπ+π+A.