The STAR collaboration reports a measurement of the transverse single-spin asymmetries, AN, for neutral pions produced in polarized proton collisions with protons (pp), with aluminum nuclei (pAl) and with gold nuclei (pAu) at a nucleon-nucleon center-of-mass energy of 200 GeV. Neutral pions are observed in the forward direction relative to the transversely polarized proton beam, in the pseudorapidity region 2.7<3.8. Results are presented for π0s observed in the STAR forward meson spectrometer electromagnetic calorimeter in narrow Feynman x (xF) and transverse momentum (pT) bins, spanning the range 0.172.5 GeV/c. It is further observed that the value of AN is significantly larger for events with a large-pT isolated π0 than for events with a nonisolated π0 accompanied by additional jetlike fragments. The nuclear dependence r(A) is similar for isolated and nonisolated π0 events.
Comparison of transverse single-spin asymmetries for forward pi(0) production in polarized pp, pAl and pAu collisions at nucleon pair c.m. energy root s(NN)=200 GeV
Fazio, S.Membro del Collaboration Group
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2021-01-01
Abstract
The STAR collaboration reports a measurement of the transverse single-spin asymmetries, AN, for neutral pions produced in polarized proton collisions with protons (pp), with aluminum nuclei (pAl) and with gold nuclei (pAu) at a nucleon-nucleon center-of-mass energy of 200 GeV. Neutral pions are observed in the forward direction relative to the transversely polarized proton beam, in the pseudorapidity region 2.7<3.8. Results are presented for π0s observed in the STAR forward meson spectrometer electromagnetic calorimeter in narrow Feynman x (xF) and transverse momentum (pT) bins, spanning the range 0.172.5 GeV/c. It is further observed that the value of AN is significantly larger for events with a large-pT isolated π0 than for events with a nonisolated π0 accompanied by additional jetlike fragments. The nuclear dependence r(A) is similar for isolated and nonisolated π0 events.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.