Measuring the Sivers Effect in the PHENIX Experiment at RHIC

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Date/Time:Thursday, 16 Apr 2009 from 4:10 pm to 5:10 pm
Location:Zaffarano Hall A401
Contact:
Phone:515-294-6952
Channel:Nuclear Physics
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Mr. Feng Wei (Iowa State University)

Experiments since 1989 have shown the spins of the quarks inside nucleons account for only 30% of the nucleons' overall spin. The later SIDIS experiments show anti-quarks mostly carry anti-aligned spin. The recent longitudinally polarized gluon measurements at RHIC show that gluons don't have significantly large contribution on the spin of the proton.

Mr. Feng Wei (Iowa State University)

Experiments since 1989 have shown the spins of the quarks inside nucleons account for only 30% of the nucleons' overall spin. The later SIDIS experiments show anti-quarks mostly carry anti-aligned spin. The recent longitudinally polarized gluon measurements at RHIC show that gluons don't have significantly large contribution on the spin of the proton. The source for the missing spin of the proton can only be from the orbital angular momentum of partons. So far people still have no good ideas how to measure the orbital angular momentum of partons. But most people believe that the Sivers effect could be related to the orbital angular momentum. To study the Sivers effect, we did analysis of leading di-hadron correlation at PHENIX mid-rapidity by using transversely polarized proton-proton collision run6(2006) data and got the result which is consistent with the results from other experiments. The analysis using run8 data on the single spin aysmmetry at forward-rapidity region is still going on and a larger asymmetry has been expected. Moreover there are two better channels for the future measurements on the Sivers effect, which are looking at photon-jet and W mesons production. Both of them only include initial-state interaction and have a larger asymmetry.