Abstract
Transverse single-spin asymmetries of very forward neutral pions generated in polarized p+p collisions allow us to understand the production mechanism in terms of perturbative and nonperturbative strong interactions. During 2017, the RHICf Collaboration installed an electromagnetic calorimeter in the zero-degree region of the STAR detector at the Relativistic Heavy Ion Collider (RHIC) and measured neutral pions produced at pseudorapidity larger than 6 in polarized p+p collisions at sqrt[s]=510 GeV. The large nonzero asymmetries increasing both in longitudinal momentum fraction x_{F} and transverse momentum p_{T} have been observed at low transverse momentum p_{T}<1 GeV/c for the first time, at this collision energy. The asymmetries show an approximate x_{F} scaling in the p_{T} region where nonperturbative processes are expected to dominate. A non-negligible contribution from soft processes may be necessary to explain the nonzero neutral pion asymmetries.
Highlights
Counts00 50 100 150 200 250 300 Mγγ (MeV/c2)contributes to this tail and the actual NB=NS can be smaller than the one estimated by the fitting, due to these π0 events
The STAR experiment reported, for π0 production, a multiplicity dependence of AN with the number of detected photons [13]. It showed that the AN decreases as the event complexity increases and jetlike events show small asymmetries
The present study investigates the asymmetries in the region where soft processes dominate by measuring AN of π0 at very forward rapidities and small pT
Summary
[9,10,11] in an initial or final state effect combined with the transverse motions of quarks and gluons. The STAR experiment reported, for π0 production, a multiplicity dependence of AN with the number of detected photons [13] It showed that the AN decreases as the event complexity increases and jetlike events show small asymmetries. The present study investigates the asymmetries in the region where soft processes dominate by measuring AN of π0 at very forward rapidities and small pT. The RHICf detector consists of the two position-sensitive sampling calorimeters with square shape in the transverse plane, called TS
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
