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Run-12 Transverse Jets: New Look at Sivers

Updated on Tue, 2013-11-05 10:09. Originally created by drach09 on 2013-11-04 18:07.

Thus far, we have focused our Sivers analyses on inclusive jet asymmetries. The size of the effects indicates a negligible Sivers effect at mid-rapidity for a combination of quarks and gluons. One other way to look at the Sivers asymmetry--with possibly a more clear path to constrain the quark Sivers effect--is to tag jets with leading charged pions. Below, I look at the Sivers asymmetry for jets whose leading (highest-z) fragmentation particle is a charged pion. I bin the asymmetries as a function of leading-pion z. A signal may offer insight into u and d-quark Sivers functions. Plots are not corrected for polarization.

pT > 9.9 GeV/c

Figure 1

xF > 0 (π+) xF < 0 (π+)
xF > 0 (π-) xF < 0 (π-)

The leading pion asymmetries are quite small, much like the inclusive jet asymmetries.

Figure 2

In Fig. 2 I show the results of a constant fit to the leading pion asymmetries as a function of η, relative to the direction of the polarized beam. Note that the asymmetries in Fig. 2 have not been corrected for polarization.

Table 1

η-Range Charge AUT Error χ2/ν
0 < η < 1 + -0.0009998 0.000846 4.965/6
0 < η < 0.5 + -0.00147 0.00105 8.233/6
0.5 < η < 1 + -7.015e-05 0.00143 6.969/6
-1 < η < 0 + -0.00145 0.000846 4.041/6
-0.5 < η < 0 + -0.00139 0.00105 3.318/6
-1 < η < -0.5 + -0.00157 0.00143 3.947/6
0 < η < 1 - 0.00107 0.000884 2.183/6
0 < η < 0.5 - 0.000183 0.00109 2.723/6
0.5 < η < 1 - 0.00279 0.00150 3.154/6
-1 < η < 0 - -0.00201 0.000884 2.276/6
-0.5 < η < 0 - -0.00247 0.00109 3.991/6
-1 < η < -0.5 - -0.00121 0.00150 2.500/6

Table 1 shows the results of the constant fits.

pT < 9.9 GeV/c

Figure 3

xF > 0 (π+) xF < 0 (π+)
xF > 0 (π-) xF < 0 (π-)

The leading pion asymmetries are quite small, much like the inclusive jet asymmetries.

Figure 4

In Fig. 4 I show the results of a constant fit to the leading pion asymmetries as a function of η, relative to the direction of the polarized beam. Note that the asymmetries in Fig. 4 have not been corrected for polarization.

Table 2

η-Range Charge AUT Error χ2/ν
0 < η < 1 + -0.000896 0.000492 5.057/7
0 < η < 0.5 + -0.000712 0.000614 1.947/7
0.5 < η < 1 + -0.00109 0.000826 10.64/6
-1 < η < 0 + 0.000363 0.000492 3.147/7
-0.5 < η < 0 + 0.000112 0.000614 5.448/7
-1 < η < -0.5 + 0.000717 0.000826 6.565/6
0 < η < 1 - -0.000295 0.000502 0.639/7
0 < η < 0.5 - -0.000464 0.000624 4.165/7
0.5 < η < 1 - 1.894e-05 0.000851 8.584/7
-1 < η < 0 - 0.000790 0.000502 5.234/7
-0.5 < η < 0 - 0.000338 0.000624 5.961/7
-1 < η < -0.5 - 0.00168 0.000851 7.259/7

Table 2 shows the results of the constant fits.

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