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Run 15 diffractive EM jet A_N preliminary request

Updated on Thu, 2024-04-04 14:06. Originally created by liangxl on 2022-04-13 11:44.

 Title: Transverse Single-Spin Asymmetry for Diffractive Electromagnetic Jets at FMS in p+p Collisions at \sqrt{s}  = 200 GeV at STAR

 PA: Xilin Liang, Latif Kabir, Kenneth Barish (supervisor)

 PA email address: xilin.liang@email.ucr.edu

 Abstract: There have been numerous attempts, both theoretical and experimental, to understand the origin of the unexpectedly large transverse single spin asymmetry ($A_{N}$) for the inclusive hadron production at forward rapidities observed in p^{\uparrow} + p collisions at various center-of-mass energies. The twist-3 contributions in the collinear factorization framework and the transverse-momentum-dependent contributions from the initial-state quark and gluon Sivers functions and/or final-state Collins fragmentation functions are potential explanations to this puzzle. Previous analyses of $A_{N}$ for forward \pi^{0} and electromagnetic jets in p^{\uparrow} + p collisions at STAR indicated that there might be non-trivial contributions to the large $A_{N}$ from diffractive processes.

 The STAR Forward Meson Spectrometer (FMS) can detect photons, neutral pions, and eta mesons in the forward direction, with pseudo-rapidity coverages of 2.6 < \eta < 4.2. In this talk, we will present the latest preliminary results and analysis updates on $A_{N}$ for diffractive electromagnetic jets in the FMS using p^{\uparrow} + p data at \sqrt{s}=200 GeV collected at STAR.

Part 1: Semi-exclusive EM-jet A_N

 runlist

  Preliminary request presentation.

  Systematic uncertainty presentation.


  Plot data points in txt. (B means blue beam, in the plot is xF > 0; Y means yellow beam, in the plot is xF < 0)

  
Figure: Run 15 diffractive EM jet A_N with FMS. Blue/Yellow points are the polarized/unpolarized beam A_N with statistics and systematic uncertainty. 

Note1: All red points shift -0.005 in x-axis. 

Note2: The last point is for 0.3 < xF < 0.45 range.

A constant fit are applied for the A_N points (not shown in the picture)
 

Blue beam A_{N} with constant fit:-0.051+/-0.015  ; value/error ratio: 3.36
 
Yellow beam A_{N} with constant fit:-0.011+/-0.016 ; value/error ratio: 0.70
 
 

  Part 2: Single diffractive EM-jet A_N and rapidity gap event A_N

  Preliminary request slide

  Event selection and analysis details slide 

  Data points for single diffractive process and Rapidity gap events

  Analysis note for single diffractive process for preliminary request.

   Preliminary plot 1: A_N for rapidity gap process

    

     
    Figure 2.1: A_N for rapidity gap events as a function of x_F for 3 different photon multiplicity cases: all photon multiplicity (top), 1 or 2 photon multiplicity (middle), and 3 or more photon multiplicity (bottom). The A_N for x_F < 0 (red points) shifts -0.013 along the x-axis. 

 
  Preliminary plot 2: A_N for single diffractive process

  

   Figure 2.2: A_N for single diffractive events as a function of x_F for 3 different photon multiplicity cases: all photon multiplicity (top), 1 or 2 photon multiplicity (middle), and 3 or more photon multiplicity (bottom). The A_N for x_F < 0 (red points) shifts -0.013 along the x-axis. 

 
    Preliminary plot 3: Comparison plot of A_N for inclusive, single diffractive, and rapidity gap events

    Figure 2.3: A_N as a function of x_F for 3 processes for the case of photon multiplicity 1 or 2 (top panel) and photon multiplicity 3 or more (bottom panel): inclusive process (red), single diffractive process (blue), and the rapidity gap events (magenta)

 
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