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Interference fragmention function measurements in PHENIX

Interference fragmention function measurements in PHENIX. Spin 2010 , Juelich , September 28 Ralf Seidl (RIKEN) for the collaboration. Quark distributions. q(x),G(x). Unpolarized distribution function q(x).

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Interference fragmention function measurements in PHENIX

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  1. Interference fragmention function measurements in PHENIX Spin 2010 , Juelich , September 28 Ralf Seidl (RIKEN) for the collaboration

  2. Quark distributions q(x),G(x) Unpolarized distribution function q(x) Difference of quarks with parallel and antiparallel polarization relative to longitudinally polarized proton (known from fixed target (SI)DIS experiments, gluons from RHIC) Dq(x), DG(x) Helicity distribution function Dq(x) Difference of quarks with parallel and antiparallel polarization relative to transversely polarized proton (first results from HERMES and COMPASS – with the help of Belle) dq(x) Transversity distribution function dq(x) Sum of quarks with parallel and antiparallel polarization relative to proton spin (well known from Collider DIS experiments) R.Seidl: PHENIX IFF results

  3. Helicity flip amplitude Chiral odd Since all interactions conserve chirality one needs another chiral odd object Does not couple to gluons adifferent QCD evolution than Dq(x) Valence dominateda Comparable to Lattice calculations, especially tensor charge Transversity properties Positivity bound: Soffer bound: R.Seidl: PHENIX IFF results

  4. How to access Transversity: another chiral-odd function Drell Yan: • Combine two Transversity distributions with each other SIDIS: • Combine Transversity distributions with chiral-odd fragmentation function (FF) • Total process is chiral-even: OK • Possible Partners: • Collins FF • Interference FF • Transverse L FF • Most require single spin asymmetries in the fragmentation R.Seidl: PHENIX IFF results

  5. Collins FF IFF _ _ + + _ _ + + Measurement of transversity in pp Drell-Yan IFF Collins Martin,Schafer,Stratmann,VogelsangPRD60:117502 (1999) Jaffe, Jin, Tang, PRL 80 (1999)1166 Yuan, PRD 77, 074019 (2008)  RHIC, FAIR (need very high L, P) RHIC RHIC R.Seidl: PHENIX IFF results

  6. h1 h2 Quark spin _   quark quark h1 h2 Collins fragmentation function h _   quark quark h (courtesy A. Bacchetta) Comparison of IFF and Collins FF Interference fragmentation function J. Collins, S.Heppelmann, G. Ladinsky, Nucl. Phys. B, 420 (1994) 565 Requires knowledge on quark kinematics J. Collins, Nucl. Phys. B396, (1993) 161 R.Seidl: PHENIX IFF results

  7. Both FFs measured at Belle PRD78:032011,2008 05.2975) arXiv:0912.0353 05.2975) Preliminary R.Seidl: PHENIX IFF results

  8. Transversity from di-hadron SSA Physics asymmetry Unpolarized quark distribution Known from DIS Transversity to be extracted Hard scattering cross sectionfrom pQCD IFFmeasured in e+e- Di-hadron FF measured in e+e- R.Seidl: PHENIX IFF results

  9. Why di-hadron SSA in p+p • Di-hadron vs single hadron • Collinear factorization is shown to be valid  TMD factorization is less certain in p+p (Rogers, Mulders, arXiv:1001.2977) • No model uncertainties from transverse momentum dependence of FF and PDF • No need to separate Sivers/Collins effects as in single hadron measurement • Completely independent measurement • Doesn’t need jet reconstruction • Di-hadron measurement in fixed target vs collider • At higher scale • sub-leading twist effects suppressed • factorization assumption better justified R.Seidl: PHENIX IFF results

  10. PHENIX detectors used for IFF analysis • Use 2 separate spectrometer arms at central rapidity, |h| < 0.35 • Azimuthal coverage: 90° + 90° • Electromagnetic Calorimeters • PbSC + PbGl • High granularity Dh  Df=0.01  0.01 • Tracking of charged particles • Drift chamber, pad chambers • Beam-beam counter as a luminosity monitor • Exploit good event selection capability, high bandwidth/event rate R.Seidl: PHENIX IFF results

  11. Event selection • Transversely polarized p+p data taken in 2006 and 2008 • Integrated luminosity 7.7 pb-1 • Average polarization 50%, in radial direction • Find charge-ordered pairs: (h+p0), (p0h-), (h+h-) • p0 • pT> 1 GeV/c • h+/- • 1 GeV/c < pT < 4.7 GeV/c • Assuming pion mass for all hadrons • Both particles come from the same detector arm (Dh  Df = 0.7 p/2) • One particle fires the trigger (EMCal cluster with energy > 1.4 GeV) • Calculate the asymmetry, extract the analyzing power R.Seidl: PHENIX IFF results

  12. Definition of Vectors and Angles Bacchetta and Radici, PRD70, 094032 (2004) R.Seidl: PHENIX IFF results

  13. from di-hadron production No significant asymmetries seen at mid-rapidity. Added statistics from 2008 running R.Seidl: PHENIX IFF results

  14. from di-hadron production No significant asymmetries seen at mid-rapidity. Added statistics from 2008 running R.Seidl: PHENIX IFF results

  15. Future sensitivity • Plan: accumulate ~40pb-1 in the next years at 200 GeV with transverse polarization • Sensitivity sufficient to see also asymmetries at mid-rapidity R.Seidl: PHENIX IFF results

  16. Moving forward • Central rapidity is dominated by lower x: • Transversity not so large • Large contribution by gluons in denominator of asymmetry • Move to more forward rapidities to obtain larger signal • MPC is most forward, but mostly sensitive to neutrals • 99.9% of hadrons are absorbed before muon arms • hadronic decays into muons are suitable R.Seidl: PHENIX IFF results

  17. Muon arm IFF • Hadronic decays before muon arms are suitable for IFF measurements • Momentum is mostly maintained by muons • Some smearing due to decay will result in smeared invariant masses, PT, but • Belle sees no sign change of IFF  some smearing ok • Ongoing study: • Understand the composition of decay muons (p/K composition changes) • Understand amount of smearing • Will need pK Iffs from Belle R.Seidl: PHENIX IFF results

  18. Summary • Di-hadron single spin asymmetries measured at Mid-Rapidity in PHENIX • Asymmetries consistent with zero, but expected due to x coverage, unpol cross section • More forward di-hadron SSA measurements ongoing utilizing muons arms • Smearing and composition study ongoing • Results expected soon R.Seidl: PHENIX IFF results

  19. Future measurements • With additional detectors obtain capability to detect forward jets • Possibility to also measure Collins asymmetries at PHENIX • With IFF and Collins two ways to access Transversity • Long term: Improve forward DY capabilities in PHENIX to study Sivers Function, Boer Mulders and Transversity (sea quarks) R.Seidl: PHENIX IFF results

  20. DY transversity measurements at RHIC, JPARC and FAIR RHIC @ √s=200GeV Q=15GeV Q= 8GeV Q= 5GeV Q= 3GeV JPARC @ √s=10GeV Kawamura et. al Nucl.Phys.B777:203-225,2007. Assuming Soffer bound DY transverse double spin asymmetries golden channel to Transversity: Requires both (anti)- protons transversely polarized For mostly sensitive to u-quark transversity For pp smaller asymmetries due to sea transversity , but for tensor charge absolutely necessary R.Seidl: PHENIX IFF results

  21. R.Seidl: PHENIX IFF results

  22. Transverse spin: Insights to QCD • Sivers effect: • Requires Orbital angular momentum of quarks or gluons • Is direct consequence of Gauge invariance in correlator • “Rescattering “ is either attractive (DIS) or repulsive (Drell Yan)  Gauge invariance leads to prediction of sign change of Sivers effect R.Seidl: PHENIX IFF results

  23. Transverse spin: Insights to QCD J.C. Collins, Nucl. Phys. B396, 161(1993) Single spin asymmetry q Artru/Mehkfi : String fragmentation Collins Effect: Fragmentation with of a quark qwith spin sqinto a spinless hadron h carries an azimuthal dependence: π+ picks up L=1 to compensate for the pair S=1 and is emitted to the right. String breaks and a dd-pair with spin -1 is inserted. • Collins effect: R.Seidl: PHENIX IFF results

  24. Transverse future • Measure di-hadron back-to-back asymmetires over large rapidity intervals • Disentangle contributions to large single spin asymmetries • Collins asymmetries (hadrons within jets) • Siverse asymmetries (jet asymmetries) • Test Sivers sign change by Drell Yan: ASIVDIS = - ASIVDY • Sivers flavor decomposition via W AN measurements (Kwang, Qiu) R.Seidl: PHENIX IFF results

  25. Single pion production at midrapidity • Quark –gluon scattering dominates R.Seidl: PHENIX IFF results

  26. Future improvements • Vertex Detectors (2011-2012) Large acceptance precision tracking • Heavy flavor tagging • Jets • Drell-Yan • Electrons from charm decays and beauty decays separately • c,b-Jet Correlations • Forward Calorimetery (2012-2013) Proposed PHENIX Upgrade ( 1 < eta < 3 ) • AN Pi0, Direct Photon, Gamma-Jet • Full detector simulations in progressIn correspondence with theorists R.Seidl: PHENIX IFF results

  27. Alexei Prokudin, DIS2008, update of Anselmino et al: hep-ex 0701006 Global transversity analysis First global analsys of the HERMES data, the COMPASS deuteron data and the final Belle data tensor charge slightly smaller than model and lattice predictions Open questions: evolution of Collins fragmentation function New Compass data not yet included R.Seidl: PHENIX IFF results

  28. Interference Fragmentation – “f0“ method jR2 p-jR1 • Similar to previous method • Observe angles j1R+j2R between the event-plane (beam, two-pion-axis) and the two two-pion planes. • Theoretical guidance by Boer,Jakob,Radici R.Seidl: PHENIX IFF results

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