References - Bogoliubov Laboratory of Theoretical Physics - JINR

SPIN PHYSICS AT NICA
A. Nagaytsev
Joint Institute for Nuclear Research, 141980 Dubna, Russia
Abstract
Recently JINR launched the project on constructing the new collider NICA
which will operate both in heavy ion collisions mode and in polarized protonproton
collisions mode. The aspects of the physical program of the latter option
(SPD/NICA) are considered. The preliminary estimations on rates and possible
layout of the spectrometer are presented.
Since the famous “spin crisis“ in 1987, the problem of the nucleon spin structure remains
one of the most intriguing puzzle of high energy physics. The central component
of this problem attracting for many years enormous both theoretical and experimental
efforts, is a search for answering the questions, how the spin of the proton is build up
from spins and orbital momenta of its constituents. The searches brought up a concept
of the parton distribution functions in nucleon, at the beginning two of them, one, f1
, for unpolarized and second , g1 , for polarized nucleons. Now we know that must be
about 50 different parton distributions functions for a complete description of the nucleon
structure. While today a part of the polarized distributions can be considered as
sufficiently well known, there is a number of PDFs which either are absolutely unknown,
or poorly known, especially the spin dependent ones, These are longitudinally polarized
distributions of valence light sea, strange quarks and gluons, both sea and valence transversely
polarized distributions of all flavours. This new class of PDFs, is characterized
by its the non-trivial dependence on a transverse quark momentum. The most significant
among them are Sivers and Boer-Mulders PDFs. The studies of these open questions of
the nucleon structure is the first priority task for the scientific program of the second IP
the NICA facility. The parameters of the NICA collider allows to perform the important
spin and polarization effects studies of:
- Drell-Yan (DY) processes with longitudinally and transversely polarized p and d
beams. Extraction of unknown (poor known) parton distribution functions (PDFs);
-PDFsfromJ/ψ production processes;
- Spin effects in baryon, meson and photon productions; Effects in various exclusive
reactions;
- Diffractive processes;
- Cross sections, helicity amplitudes and double spin asymmetries (Krisch effect) in
elastic reactions;
- Spectroscopy of quarkoniums.
To determine Boer-Mulders and Sivers PDFs at NICA the following measurements
must be performed:
– Unpolarized and single polarized Drell�Yan(DY)processeswithppand
pd collisions;
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