Inclusive (p, ?0) reactions atE lab=200 MeV

Systematic of proton-induced pion production at subthreshold energies

“…In addition the energy scaling which was based on the excitation function obtained by the CHIC collaboration may need to be modified. Although the dependence of the 7r ~ probabilities of Bellini et al [8] follow" the mass dependence observed for the Orsay and TAPS data, they are larger by a factor 2. The decreasing probability as function of mass either indicates that for lighter targets scaling could be more proportional to the mass, or is due to a stronger reabsorption of pions in the heavier targets.…”

“…The n ~ cross section has been measured as low as 2 MeV above absolute threshold [11], the other two explicit measurements are the new data at 190 MeV [6] and the 200 MeV data of ref. [8], mentioned previously. A notable result is the consistent measurement of 13C (n +) and 1aN (n ~ recoils from pionic fusion [12].…”

“…The first comparison [8] between the inclusive charged and neutral pion cross sections lead to the surprising result that a~o > a~+ contrary to expectations based on isospin. Recently, the TAPS collaboration has measured 7r ~ cross sections at Eproton = 190 MeV for a number of targets [6,7].…”

“…The ~r ~ data are from ref. [8] (Be189, full circles) and from the TAPS collaboration [6,7] (open circles). The ~r + data are from the CHIC collaboration [3,4] (Jak97, full squares) and from measurements at Orsay, [16,17] (open squares).…”

“…Of course, now it is understood that the nuclear bremsstrahlung is still dominating the photon cross section in this energy region [6,7]. The first data set which required full 7r ~ identification by observing the proper correlation between two decay photons were obtained for Eproton = 200 MeV by Bellini et al [8]. Also detection of the lr-cross section is technically difficult due to its small cross section as compared to the 7r + cross section.…”