Here I am documenting some details of the pi0 Collins asymmetries analysis on FMS.

I followed the procedure as outlined in Renee's write-up to caluclate Collins asymmetries.

A_UT vs jet energy

1) diphoton mass with different Z_{#pi0}^{jet} cuts at each energy bin

I found that previously when I fit the diphoton mass distributions I was not using the correct
mass histograms. Now I have made sure all the cuts are correctly implemented I tried different
z cuts to calculate the asymmetries vs energy.

The following plots compare the mass distributions with 0 < z < 0.9 cut to those with
0.3 < z < 0.9 cuts.

                      
                                    0 < z < 0.9                                                                                                         0.3 < z < 0.9
 

  

  

   

 

 

 
                                                                      Figure 1. mass distributions with different z cuts

So with 0.3 < z < 0.9 cut the significance of the pi0 signal has improved, but it comes with the price of reudced statistics.

2). Signal fractions in the signal region ( 0.1 < M < 0.2 GeV) and side-bands (0 < M < 0.1 and 0.2 < M < 0.3 GeV)

Figure 2 shows an example of comparing the signal fractions vs fill index for the above z cuts. The comparison for all 7 energy bins can be found
here for 0 < z < 0.9 and here for 0.3 < z < 0.9.

 

             Figure 2 a). signal fraction vs fill index for 0 < z < 0.9                                                    Figure 2 b). signal fraction vs fill index for 0.3 < z < 0.9

The signal fractions in side-bands can be found at here for 0 < z < 0.9, and here for 0.3 < z < 0.9.


3). Background subtracted asymmetries vs jet energy

fill-by-fill total asymmetries in the signal region (for 0 < z < 0.9) can be found at,

http://www.star.bnl.gov/protected/spin/yuxip/pi0jet/ebins/z0to0.9/z0to0.9TotAsySigVsFill_7ebins.pdf


and total asymmetries in the side-bands (for 0 < z < 0.9),

http://www.star.bnl.gov/protected/spin/yuxip/pi0jet/ebins/z0to0.9/z0to0.9TotAsyBkgVsFill_7ebins.pdf

Figure 3 shows the fill averaged total asymmetries in the signal region and sidebands,

   
         Figure 3 a). total asy. in signal region (0.1 < M < 0.2 GeV)                         Figure 3 b). total asy. in sidebands ( 0 < M < 0.1 U 0.2 < M < 0.3GeV)


Finally the fill-by-fill  background subtracted asymmetries for each energy bin can be found at,

http://www.star.bnl.gov/protected/spin/yuxip/pi0jet/ebins/z0to0.9/AnVsFill_7ebins.pdf for 0 < z < 0.9

and,

http://www.star.bnl.gov/protected/spin/yuxip/pi0jet/ebins/z0.3to0.9/AnVsFill_7ebins.pdf for 0.3 < z < 0.9.


 
                        Figure 4 a). A_UT vs jet energy with 0 < z < 0.9 cut                                          Figure 4 b). A_UT vs jet energy with 0.3 < z < 0.9 cut




A_UT vs z_{#pi^{0}}^{jet}

Due to the overwhelming combinatorial background at low z I only looked at A_UT for z above 0.4, with jet pT > 2.0 GeV,  2.8 < jet eta < 4.0.

Figure 4 shows the corresponding mass distributions for 5 z bins from 0.4 to 0.9.

 

 



                                                         Figure 5). mass distributions for different z cuts


The signal fraction in signal region vs fill index can be found at,

http://www.star.bnl.gov/protected/spin/yuxip/pi0jet/zbins/SigFracVsFill_zbins.pdf

and the signal fraction in side-band is at,

http://www.star.bnl.gov/protected/spin/yuxip/pi0jet/zbins/SbFracVsFill_zbins.pdf

Background substracted asy. vs fill can be found at,

http://www.star.bnl.gov/protected/spin/yuxip/pi0jet/zbins/AnVsFill_zbins.pdf

Figure 5 shows the background subtracted Collins asymmetry vs z,


                                                     Figure 6). A_UT vs z