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HK: Hadronen und Kerne
HK 66: Hadronic Probes VII, Bremsstrahlung
HK 66.2: Group Report
Thursday, March 19, 1998, 14:30–15:00, G
Measurements of the virtual bremsstrahlung in the nucleon-nucleon system — •J.C.S. Bacelar1, M.J. van Goethem1,2, M.N. Harakeh1, M. Hoefman1,2, H. Huisman1, N. Kalantar-Nayestanaki1, A. Kugler3,2, H. Löhner1,2, J.G. Messchendorp1, R.W. Ostendorf1,2, S. Schadmand1, R. Simon4,2, R. Turrisi1,2, M. Volkerts1, V. Wagner3,2, H.W. Wilschut1,2, and A. van der Woude1 — 1KVI, Groningen — 2for the TAPS collaboration — 3NPI, Řež u Prahy — 4GSI, Darmstadt
The virtual (e+e−) bremsstrahlung process in nucleon-nucleon (NN) scattering is an exclusive probe of the NN potential. By measuring the full leptonic phase space, the nuclear currents are decomposed into transverse (T), longitudinal (L) and the interference (TT, LT) terms. In the case of p+p → p+p+e+e− there are six independent response functions [1]: WT, WTT, W′TT, WL, WLT and W′LT.
The results from a pilot experiment studying the reaction p+p → p+p+e++e−, with a polarized proton beam of 190 MeV, obtained from AGOR, will be presented. The two protons were detected with the Small-Angle Large-Acceptance Detector (SALAD), in azimuthally symmetric geometry for laboratory angles between 5∘ and 19∘, and the two leptons were detected with the Two-Arm Photon Spectrometer (TAPS). Differential cross sections were measured for photon invariant masses up to 80 MeV/c2. The data is found to be in reasonable agreement with calculations [1], using the low-energy theorem approximation. For the first time the WT,WTT and W′TT response functions were extracted as a function of the invariant mass of the virtual photon.
The virtual bremsstrahlung program at KVI will be extended by using the Plastic Ball. This is a 4π, highly segmented detector system allowing to cover most of the dilepton phase-space. Simulations show that with these second-generation experiments the remaining response functions (WL, WLT) are within reach.
[1] A. Yu. Korchin and O. Scholten, Nucl. Phys. A581, 493 (1995)