1 / 14

Transversity at STAR

Transversity at STAR. Akio Ogawa Penn State Univ for collaboration 2000 Sep 19 Future Transversity Measurements. Spin Physics at STAR. Gluon Polarization: Direct Photon Direct Photon + jet Jet Jet + Jet Quark / Anti-Quark Polarization :

read
Download Presentation

Transversity at STAR

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Transversity at STAR Akio Ogawa Penn State Univ for collaboration 2000 Sep 19 Future Transversity Measurements

  2. Spin Physics at STAR Gluon Polarization: Direct Photon Direct Photon + jet Jet Jet + Jet Quark / Anti-Quark Polarization : W production Transversity : Pion pair correlation Dijet? Parity Violating Asymmetry: Search for New Physics

  3. Nucleon’s Transversity Leading twist quark distribution Longitudinal Spin Distribution Transversity No gluon contribution Helicity flip Soffer Inequality Last missing piece at leading twist

  4. Need mass to have helicity flip Need chiral odd interaction to observe Experimentally, free from false asymmetry

  5. Two meson production f mass z Pt,h Phase Shift is known Fragmentation function }unknown Interference fragmentation function Schwartz Inequality

  6. Asymmetries predicted by Jian Tang for pp at sqrt(s) 200/500 GeV This model is an optimistic estimation: saturate Soffer & Schwartz inequality, mass=0.8 (at max asymmetry)

  7. STAR detector

  8. STAR detector for Transversity measurement Wide acceptance : Jet measurements ~25-30% Et resolution check Z dependence check Pt & Rapidity dependence Good invariant mass resolution: 2-5 % at 800MeV check invariant mass dependence STAR is a working detector! But slow: Need good triggers at high luminosity TPC has 40usec drift time : pile up events STAR-RCF bandwidth (20Mb/sec) : L3 data volume reduction No PID at high pt :~10% Kaon/proton

  9. A factor from Phase Shifts as function ofinvariant mass Invariant mass resolution of STAR for Pt = 2-10 GeV pair around mass ~ 0.8 GeV

  10. STAR Trigger Level 0 Trigger EMC 1.0(h) x 0.8(f) trigger patch see only 1/3 of total energy at L0 trigger bias towards EM rich events Look at the other side of triggered jet CTB/MWC multiplicity trigger Level 3 Trigger TPC tracking available DAQ to tape speed depends on data size Data size reduction at L3 Possibly selecting invariant mass , z , cosf

  11. Signal Estimation Cuts : Find jets (EM+charged hadrons) in -0.3 <h< 0.3 Any 2 opposite charged particle pairs within a jet Pt > 0.3GeV -1 < h < 1 0.5 < mass < 1.0GeV 60% Number of pairs / Event vs Z In average 1.2 pairs within the mass range There are 2 jets events 20% 1% z

  12. A scenario Year 2002 or 2003 L = 8 10^31 /cm^2/sec 1 week run, 50% machine time 32/pb L0 (EMC Jet) Trigger with threshold ~ 10GeV Only using north/south (not top/bottom) With L3 data size reduction ~15Hz to tape 300K sec Hz Total Jet Events 15 4.5M Beam Polarization 0.7 pt<10 2M cosf integral 0.5 10<pt<20 2M dilution factor 0.35 20<pt 0.5M 82K events = 1% error on A 2M events = 0.2% error on A Study dependence on cosf, mass , z, Pt_jet , h _jet

  13. Does it make sense to run in year 1? Year 2001 (Numbers here are even more rough) L = 1.25 10^30 /cm^2/sec 2 week run, 50% machine time CTB multiplicity trigger Only using north/south (not top/bottom) 30Hz(?) (L3 event selection on Jets / high z ? /mass ?) ~10Hz to tape(?) 600K sec Hz Total Min bias 30 Jet Events ~3 1.8 M Beam Polarization 0.5 5<pt<10 ~2.5 1.8 M cosf integral 0.5 10<pt<20 ~0.4 240K dilution factor 0.25 20<pt ~0.02 12K 160K events = 1% error on A 4M events = 0.2% error on A Single spin & transverse spin / false asym free / EMC is not must If we measure non-zero, it’s already something We should start looking at it, when we get collisions But require good polarization & luminosity to have “real” physics data

  14. Conclusion STAR can measure 2 pion asymmetry Can see dependence on mass , cosf, z, Pt_jet , h _jet Many handles to check models Fragmentation function is needed to extract transversity Analysis on LEP data is going on

More Related