1. Recent PHENIX Spin Results Astrid Morreale University of California at Riverside On behalf of the collaboration WWND, April 12, 2008

2. 2 Outline  About polarized RHIC, PHENIX  The Proton Spin Structure via Asymmetries  Recent PHENIX results from polarized proton running (longitudinal, transverse if time permits)  Summary

3. 3 RHIC  Acceleration of polarized protons between 25 and 250 GeV  Up to 120 Bunches with 2*10 11 protons (100ns apart)  Polarization up to 70%  http://www-nh.scphys.kyoto-u.ac.jp/SPIN2006/SciPro/pres/plenary/MeiBai.ppt

4. 4 scattered proton recoil Carbon polarized beam Carbon target Polarimetry  “CNI”-Polarimeter measures left-right asymmetries in elastic pC collisions o Provides fast relative polarization measurement o Scan polarization over x and y range of the beam 270.352002003 * 400.122002004 * 48 55 49 Polarization [%] 0.0862.42006 * 7.52002006 * 3.42002005 * Luminosity [pb -1 ] (recorded)[GeV]Year Forward scattered proton proton target proton beam  “Jet” Polarimeter measures left-right asymmetries in elastic pp collisions o Uses the known polarization of H atoms from Atomic Beam Source o Absolute measurement o Integrating over beam profile o Run 6: total syst. polarization uncertainty  P B P Y /(P B P Y )=8.4%

5. 5 The PHENIX Detector for Spin Physics Central Detector Acceptance: (|  |  x  : High efficiency  trigger High efficiency  trigger    detection    detection – Electromagnetic Calorimeter: PbSc + PbGl,  < |0.35|,  = 2 x 90  PbSc + PbGl,  < |0.35|,  = 2 x 90          – Drift Chamber – Ring Imaging Čerenkov Detector(RHIC) Muon Arms (forward kinematics (~1.1<|  |<2.4) : J  J  – Muon ID/Muon Tracker (  )     – Electromagnetic Calorimeter (MPC) Global Detectors: Relative Luminosity Relative Luminosity – Beam-Beam Counter (BBC)  Zero-Degree Calorimeter (ZDC) Local Polarimetry - ZDC Local Polarimetry - ZDC

6. Intrinsic Spin Violates our intuition: How can an elementary particle such as the e¯ be point like and have perpetual angular momentum.? The Proton also violates our intuition. The Proton is composed of quarks, gluons and anti quarks. We should expect the proton's spin to be predominately carried by its 3 valence quarks 6

7. That nucleon has a large anomalous magnetic moment proves that this is not a fundamental spin1/2 Dirac particle. Within the nucleon: Quarks, gluons and their angular momentum caused by their high speed motion within the nucleon are contributors to the Nucleon's spin.

8. 8 Contributions to the Proton's Spin  Quarks and Gluons carry about 50%(each) of the longitudinal momentum  What about Spin? Valence Quarks (QPM) ~30% (QCD) Gluons, Sea Quarks: ~>, =,, =, <0? Orbital Angular Momentum ~?

9. 9 The Spin Structure of the Proton Longitudinal Spin Sum Rule: Transverse Spin Sum Rule? Double Spin Asymmetries (pp,SIDIS) W-production (pp) Exclusive processes (DVCS,etc) Chiral-odd Fragmentation functions (Collins,IFF,L) Sivers effect?? ΔG, Δq=are the probabilities of finding a parton with spin parallel or anti parallel to the spin of the nucleon.

10. 10 Accessing  g with Asymmetries I Hard subprocess asymmetries (LO) Increasing x, p T

11. 11 Asymmetries  For our  g program the tools are measurements of helicity cross section asymmetries A LL Bunch spin configuration alternates every 106 ns Data for all bunch spin configurations are collected at the same time  Possibility for false asymmetries are greatly reduced (N) Yield (R) Relative Luminosity BBC vs ZDC (P) Polarization RHIC Polarimeter (at 12 o’clock) Local Polarimeters (SMD&ZDC)

12. 12 Asymmetries  Accessing  g: Inclusive channels A LL (pp  AX) measurable at Phenix   0 : wide p T range, mixture with gg  X dominant at low p T  , similar to  0, different FF’s.   , mixture sensitive to qg  qX at high p T o Multiparticle clusters (parts of jets), correlated with  0,  o Direct photons: p T range 6-20+ GeV/c, dominated by qg  q  o J/ ,  , e  (gg  cc)   L z : Current k T,, D L, A N,UT, T measurements at Phenix o A N π 0 /π  / h , J/  forward neutrons o o D LL Anti-Λ Spin Transfer o k T azimuthal di-h  correlations

13. 13  0 cross section measurement  Agreement between data and pQCD theory  Shows that pQCD and unpolarized PDFs determined in DIS can describe pp data  Choice of fragmentation function crucial (dominated by gluon fragmentation)  Scale uncertainty still large at lower p T <5 GeV PHENIX:  0 mid-rapidity, 200GeV hep-ex-0704.3599

14. 14 Measured asymmetries for pp  0 X from Run 5,Run 6 Run3,4,5: PRL 93, 202002; PRD 73, 091102; hep-ex-0704.3599  0 Asymmetries  Asymmetry of combinatorial background estimated from sidebands and subtracted Initial state parton configurations contributing to unpolarized cross section (Fractions) W. Vogelsang et al.  Dominated by gg for p T <3, qg for 3<p T <10 GeV

15. 15 Information from  0 Asymmetries vs. x T =2p T /  S  Inclusive  0 A LL cannot access  g(x) directly oOnly sensitive to an average over a wide x range oNo conclusions about moment of  g(x) possible without a model for its shape  More (indirect) information from varying cms energies oHigher (500 GeV)  lower x oSmaller (62 GeV)  higher x (and larger scale uncertainty)

16. 16  +,- Asymmetries  New set from M. Stratmann et al. is the first to use charged separated  data from SIDIS for fragmentation functions Charged pions above 4.7 GeV identified with RICH. At higher p T, qg interactions become dominant:  q  g term. A LL becomes significant allowing access to the sign of  G A LL becomes significant allowing access to the sign of  G Fraction of pion production

17. 17 Information from  +,- Asymmetries  Inclusive  +,-,0 A LL has access to sign  g(x) directly   “Model independent” conclusion possible once enough data is available.

18. 18   Recent preliminary extraction of fragmentation functions,   Eta has (slightly) enhanced sensitivity to gg (when compared to the  0 ) Observation of difference in asymmetries could help disentangle the contributions from the different quarks and the gluons.

19. 19   Asymmetries Dominated by qg Compton: - Small uncertainty from FFs - Better access to sign of  G (  q  G) -Clean “Golden Channel” :-) -Luminosity Hungry :-(

20. 20 Information from  e +,- Asymmetries  Provide access different x range o Thresholds o J/  range (forward arms) o Prompt  : no fragmentation z=1 o Rare channels with large background o Need more luminosity prompt photon cc  eX bb  e  X J/  x  G(x)

21. 21  G(x) Global Analysis  Results from various channels combined into single results for  G(x)  Correlations with other PDFs for each channel properly accounted  Every single channel result is usually smeared over x  global analysis can do deconvolution (map of  G vs x) based on various channel results  NLO pQCD framework can be used  Global analysis framework already exist for pol. DIS data and being developed to include RHIC pp data, by different groups One of the attempts of global analysis by AAC Collaboration using PHENIX  0 -Preliminary data Now Run5-Final and Run6-Preliminary  0 data are available

22. 22  G(x) Global Analysis Latest Results Global Analysis of Helicity Parton Densities and Their Uncertainties (de Florian, Sassot, Stratmann and Wogelsang) ArXiv:0804.0422 (April 2008) -Flavor dependence of the sea -SU3 symmetry breaking?. “We also find that the SIDIS data give rise to a Robust pattern for the sea polarizations, clearly deviating from SU(3) symmetry, which awaits further clarification from the upcoming W boson Program at RHIC”

23. 23  G(x) Global Analysis Latest Results ArXiv:0804.0422 (April 2008) -A first demonstration that p-p data can be included in a consistent way in a NLO pQCD calculation. -RHIC data set significantly constraints on the gluon helicity distribution -”Inclusion of theoretical uncertainties and the treatment of experimental ones should and will be improved”

24. hep-ex/0507073(hep-ex/0507073) Transverse Spin (Collins effect) spin-dependent fragmentation functions (Sivers effect) transversely asymmetric k t quark distributions (Twist-3) quark gluon field Interference

25. Mid-rapidity data at small p T sensitive to gluons, constrains magnitude of gluon Sivers function (Anselmino et al., PRD 74, 2006) What happens if qq sets in (valence quarks) at high pT? process contribution to  0,  =0,  s=200 GeV PLB 603,173 (2004) p  +p  0 +X at  s=200 GeV/c 2 PRL 95, 202001 (2005) Transverse Spin Mid-rapidity A N of  0 and h  for y~0 at  s=200GeV  A N is 0 within 1%  interesting contrast with forward  A N : h + /h -

26. 26 Transverse Spin  0 A N at large x F 3.0<  <4.0 p  +p  0 +X at  s=62.4 GeV Asymmetry seen in yellow beam (positive x F ), but not in blue (negative x F ) Large asymmetries at forward x F  Valence quark effect? x F, p T,  s, and  dependence provide quantitative tests for theories process contribution to  0,  =3.3,  s=200 GeV PLB 603,173 (2004)

27. 27 Transverse Spin A N of J/  at  s=200GeV  Sensitive to gluon Sivers as produced through g-g fusion  Charm theory prediction is available o How does J/  production affect prediction?

28. 28 Transverse Spin Other asymmetries at  s=200GeV neutron charged particles Run 5  Strange quark Components via Spin Transfer  In PHENIX the Self-analyzing decay channel (anti-Λ) has been found to be sensitive to the polarization of the anti-strange sea of the nucleon (See: hep-ph/0511061)  Probing Orbital angular Momentum with k T Asymmetries (See:  Probing Orbital angular Momentum with k T Asymmetries (See: Phys. Rev. D 74, 072002 (2006)  Neutron asymmetries. (See: AIP Conf.Proc.915:689-692,2007 ) Results for 

29. 29 Summary  PHENIX is well suited to the study of spin physics with a wide variety of probes. oInclusive  0 data for A LL has reached statistical significance to constrain ΔG in a limited x-range (~0.02-0.3).  Need more statistics (RHIC running time) to explore different (rare) channels for oDifferent gluon kinematics oDifferent mixtures of subprocesses  Global Analysis of many channels together with DIS, SIDIS data will give us a more accurate picture of  g(x)  Upcoming W program will give more information about quarks  PHENIX has an upgrade program that will give us the triggers and vertex information that we need for precise future measurements of  G,  q and new physics at higher luminosity and energy of  G,  q and new physics at higher luminosity and energy

30. We Think That We Understand the Concept of “Rotational Motion“... but how does it workout at scales of about one fermi? (Marco Stratman. Lectures on the Longitudinal Spin Structure of the Nucleon, Wako, Japan) We Should Measure it and find out!! THANK YOU For Listening

31. 31 Extras

32. Phys Rev D41 (1990) 83; Phys Rev D43 (1991) 261 Top view Quark transverse momentum in transversely polarized proton. Front view Initial state Sivers effect: Initial state of the polarized nucleon x is longitudinal momentum fraction.

33. Collins Heppelmann effect: Final state of fragmentation hadrons : Example: Polarization of struck quark which fragments to hadrons. Nucl Phys B396 (1993) 161, Nucl Phys B420 (1994) 565

34. Sivers effect and/or Collins- Heppelmann effect? Theoretical approaches to explain huge SSAs:  Sivers effect ( is connected to quark orbital angular momentum).  Collins effect (Analyzer of transversity  q).  Twist3 effect which is related to both initial and final states. Relation of Twist3 to Sivers effect is introduced. Twist3Sivers effect Relevance of Twist3 and Sivers effect is studied. PRL97, 082002 (2006) PRD73, 094017 (2006) Available Probes at RHIC 1 p  +p  h+X Both mix 2 p  +p  di-jet+X Sivers? 3 p  +p  h+h+X (far side) Separate ? 4 p  +p  h+h+X (near side) p  +p  jet+X CollinsSivers 5 p  +p  direct  +X Sivers 6 p  +p  l + l  (Drell-Yan) Sivers

35. Collins function: analyzer of “Transversity” Transversity: : Probability to observe parton whose pol. vector is “with” or “against” the proton pol. vector with the renormalization scale .  q(x,  ) has not been measured experimentally. Lattice QCD calculates the first moments of  q(x,  ) for u,d, s quarks and the sum at  2 =2 GeV 2. “with” “against”

36. 36 Relative Luminosity  Use BBCs at  1.5 m from the interaction point to measure bunch-by-bunch luminosity o L i =N i /(  Efficiency),  Eff.=const.=22.9mb  9.7%  Use independent measurement from ZDCs (  18m) to check for intrinsic luminosity asymmetry  For Run 6 (200 GeV):   A LL (BBC-ZDC)=3.8  1.6*10 -4 (>2 standard deviations)   A LL =5.4*10 -4 o Sizeable asymmetry compared to stat. error of low p T data o Can be instrumental or physics effect  need to find out

37. 37 PHENIX:  0 mid-rapidity, 200GeV hep-ex-0704.3599 PHENIX: hep-ex-0704.3599  0 cross section and soft Physics  Exponent (e -  pT ) describes pion cross section at p T <  1 GeV/c (dominated by soft physics):   =5.56  0.02 (GeV/c) -1   2 /NDF=6.2/3  Assume that exponent describes soft physics contribution also at higher p T  soft physics contribution at p T >2 GeV/c is 2 GeV/c is <10%