On the measurement of the antineutron mass

This chapter shows how to perform a measurement of M-n with a precision of some 10-6 with a dedicated apparatus by means of a kinematical reconstruction of the charge-exchange reaction -p + p→-n + n induced by low-energy antiprotons (-p). The threshold of the reactive is at 5.103 MeV (98 MeV/c). The measuring apparatus consists of two detector arrays, one for n's, the other for -n's, with a useful area of 1 m2 each, placed at some meters from the production target and with their centers aligned at symmetrical angles with respect to the incident beam. In the presented example, the distance between the target and the detectors is 4 m and T-p=10 MeV (p-p=137.352 MeV/c), in which the angle for the symmetrical kinematics in 34.7060. Includes a drawing showing the neutron detector with a coding system for the read-out of the elements