Run 15 EM-jet A_N using FMS and EEMC: Preliminary Plots

Title: Transverse Single-Spin Asymmetry for Electromagnetic Jets at Forward Rapidities in p+p Collisions at  = 200 GeV at STAR

PAs: Latiful Kabir, Chong Kim, Ken Barish, Mriganka M Mondal, TBD 

Abstract: There have been various attempts, both experimentally and theoretically, to understand the origin of the unexpectedly large transverse single-spin asymmetries (AN) for inclusive hadron production at forward rapidity in p+p collisions that persist from low to high center-of-mass energies. Two proposed potential sources are the twist-3 contributions in the collinear factorization and the transverse-momentum-dependent contributions from either the initial-state quark and gluon Sivers functions or the final-state Collins fragmentation function. Jet AN is sensitive to the initial state effect and can provide access to Sivers functions. AN for jets of different substructures can help better understand the underlying mechanism for the observed large AN. Transversely polarized p+p collisions at RHIC are ideal to disentangle the initial and final state effects. The STAR Forward Meson Spectrometer (FMS) and Endcap Electromagnetic Calorimeter (EEMC), having pseudo-rapidity coverages of 2.6 - 4.2 and 1.1 - 2.0 respectively, can be used to detect photons, neutral pions, and eta mesons. We present preliminary results of AN for electromagnetic jets in FMS and EEMC using p+p collisions at s = 200 GeV where we explore the dependences of AN on photon multiplicity inside the jet, jet transverse momentum, and jet energy.

Plots in pdf: Fig1, Fig2, Fig3
Plots in png: Fig1, Fig2, Fig3

Plots in eps: zip file
All plots in a pdf: Link

Numerical table for the plots: Figure 1 (xF > 0), Figure 1 (xF < 0), Figure 2, Figure 3 (xF >0), Figure 3 (xF <0)

Presentation with analysis details: Link
Run list: FMS-stream (for FMS), Physics-stream (for EEMC)
PWG presentation on systematics: Link
PWG presentation on FMS simulation: Link
 
Figure 1: AN for EM-jet in FMS sorted by photon multiplicity inside the jet and different pt and energy bins.

FMS EM-jet A_N
Figure 2: FMS EM-jet AN for the cases - photon multiplicity < = 2, photon multiplicity = 3 and photon multiplicity >= 4.

FMS EM-jet A_N for n <= 2 and n > 2
Figure 3: EM-jet AN in EEMC as a function of pt sorted by EM-jet photon multiplicity.
EM-jet A_N in EEMC