abstract

The spin polarization of \({\mit \Lambda }\) hyperons produced in inclusive reactions with unpolarized protons on unpolarized targets has been studied for almost 40 years. The NA61/SHINE experiment at the CERN SPS has a great potential to study transverse polarization in \(p\)–\(p\) and \(p\)–\(A\) collisions. In this work, we discuss the impact of magnetic field and limited detector acceptance on the possible polarization measurement by this experiment. Our analysis shows that the magnetic field impact on the \({\mit \Lambda }\) polarization due to precession is one order of magnitude smaller than the detector acceptance-based polarization bias, and the identification of an experimental signal similar to that observed before by other experiments is possible.

abstract

We compute amplitudes for the \(g^* g^* \to q \bar q V^*\) process (two virtual gluons into a quark, an antiquark, and a boson) at the tree level using the spinor-helicity formalism. The resulting analytic expressions are much shorter than squared amplitudes obtained using trace methods. Our results can be used to expedite numerical calculations in phenomenological studies of the Drell–Yan process in high-energy factorization framework.