Measurements of x-rays from antiprotonic helium

Precision measurement of antiprotonic hydrogen and deuterium X-rays

“…We have now established that this was a spurious effect due to a normalization error in the deuterium run of [9]. Therefore, we now find agreement with an earlier experiment [16][17][18] and recent cascade calculations by Reifenr6ther and Klempt [19,20]. A particular strong width of the 3 d state is no longer needed to fit the cascade data in antiprotonic deuterium.…”

Antiprotonic helium

“…These fall close to the theoretically expected repulsive Re t and are comparable to the repulsive S wave NN scattering lengths. The absorptive part is within the range of phenomenological fits to heavier nuclei [1][2][3] and also agrees with the theoretical estimates relating Im t to a cumulative effect of the S and P wave N N absorption [4, 7, The calculation, with the same values of t and ro, that is equivalent to the optical potential (entry -Equivalent Optical Potential) produces much smaller 2 p shifts and widths. The difference is due to the multiple scattering terms.…”

“…Precise measurements of the 2p and 3d atomic levels and lifetimes in antiprotonic helium, obtained recently at LEAR [1], are consistent with a series of previous values [2]. However, these results seem to disagree with calculations based on parameters extracted from similar measurements in heavier antiprotonic atoms.…”

“…These potentials determine directly the level shifts and widths. It is customary to use such potentials of the form v-2 t-Ap(0, (1.1) that are linear in the nuclear density with depths determined by a phenomenological length t -referred to as a in [1][2][3]. The standard fits to the data in the oxygen region are obtained with t~-1.0+0.5-i(2.5_+0.5)fm.…”

“…The standard fits to the data in the oxygen region are obtained with t~-1.0+0.5-i(2.5_+0.5)fm. On the other hand, the best fit to the 3He, 4He data yields t(He)~0+l-i(7__2)fm, whereas the standard values of t produce widths and shifts that are systematically too small [1][2][3]. There now arises the question of the origin of the enhanced absorption.…”