Measurements at 0° of negatively charged particles and antinuclei produced in collisions of 14.6A GeV/c Si on Al, Cu, and Au targets

We report measurements of d¯, p¯, ${\mathit{K}}^{\mathrm{-}}$, and ${\mathrm{\pi }}^{\mathrm{-}}$ produced at 0° in collisions of 14.6A GeV/c ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ on Al, Cu, and Au targets. A beam-line focusing spectrometer was used to identify particles at rigidities from -2 to -8 GV. The ratio of d¯/p¯ invariant cross sections at midrapidity (y=1.7) is (1±0.7)×${10}^{\mathrm{-}5}$, larger than expected from a calculation of dd¯ direct production but smaller than predicted by a simple coalescence model. We also report limits on the production of exotic particles.