The STAR experiment reports new, high-precision measurements of the transverse single-spin asymmetries for π± within jets, namely the Collins asymmetries, from transversely polarized p↑p collisions at s=510 GeV. The energy-scaled distribution of jet transverse momentum, xT=2pT,jet/s, shows a remarkable consistency for Collins asymmetries of π± in jets between s=200 GeV and 510 GeV. This indicates that the Collins asymmetries are nearly energy independent, with, at most, a very weak scale dependence in p↑p collisions. These results extend to high-momentum scales (Q2≤3400 GeV2) and enable unique tests of evolution and universality in the transverse-momentum-dependent formalism, thus providing important constraints for the Collins fragmentation functions.
Energy Independence of the Collins Asymmetry in Collisions
S. Fazio;
2025-01-01
Abstract
The STAR experiment reports new, high-precision measurements of the transverse single-spin asymmetries for π± within jets, namely the Collins asymmetries, from transversely polarized p↑p collisions at s=510 GeV. The energy-scaled distribution of jet transverse momentum, xT=2pT,jet/s, shows a remarkable consistency for Collins asymmetries of π± in jets between s=200 GeV and 510 GeV. This indicates that the Collins asymmetries are nearly energy independent, with, at most, a very weak scale dependence in p↑p collisions. These results extend to high-momentum scales (Q2≤3400 GeV2) and enable unique tests of evolution and universality in the transverse-momentum-dependent formalism, thus providing important constraints for the Collins fragmentation functions.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.


