1. Columbia University Christine Aidala September 2005 Transverse Spin at Results and Prospects Transversity 2005, Como

2. C. Aidala, Transversity 2005, September 2005 2 RHIC’s Experiments Transverse spin only (No rotators) Longitudinal or transverse spin Also pp2pp, pC, and polarized H jet polarimeters studying polarized elastic scattering

3. C. Aidala, Transversity 2005, September 2005 3 AGS LINAC BOOSTER Polarized Source Spin Rotators 200 MeV Polarimeter AGS Internal Polarimeter Rf Dipole RHIC pC Polarimeters Absolute Polarimeter (H jet) P HENIX P HOBOS B RAHMS & PP2PP S TAR AGS pC Polarimeter Partial Snake Siberian Snakes Helical Partial Snake Strong Snake Spin Flipper RHIC as a Polarized p-p Collider Various equipment to maintain and measure beam polarization through acceleration and storage

4. C. Aidala, Transversity 2005, September 2005 4 The PHENIX Collaboration 13 Countries; 62 Institutions; 550 Participants as of 3/05

5. C. Aidala, Transversity 2005, September 2005 5 The PHENIX Detector 2 central spectrometers - Track charged particles and detect electromagnetic processes 2 forward spectrometers - Identify and track muons 2 global detectors - Determine when there’s a collision Philosophy: High rate capability & granularity Good mass resolution and particle ID  Sacrifice acceptance

6. C. Aidala, Transversity 2005, September 2005 6 PHENIX Detector (cont.) Central arms Photons, electrons, identified charged hadrons |  | < 0.35  = 180 degrees Forward muon arms Track and identify muons 1.2 < |  | < 2.4 Beam-beam counters Charged particles 3.0 < |  | < 3.9 Zero-degree calorimeters Neutrons 4.7 < |  | < 5.6

7. C. Aidala, Transversity 2005, September 2005 7 Spin Running at PHENIX So Far 2001-2 –Transversely polarized p+p collisions –Average polarization of ~15% –Integrated luminosity 150 nb -1 –Figure of merit (P 2 L) 3.38 nb -1 2003 –Longitudinally polarized p+p collisions achieved –Average polarization of ~27% –Integrated luminosity 220 nb -1 –Figure of merit (P 4 L) 1.17 nb -1 2004 –5 weeks commissioning, 4 days data-taking –Average polarization ~40% –Integrated luminosity 75 nb -1 –Figure of merit (P 4 L) 1.92 nb -1 2005 –Average polarization ~48% –Integrated longitudinal lumi 3.59 pb -1 –Figure of merit (P 4 L) ~1.9 pb -1 –Integ. transverse lumi 0.163 pb -1 –Figure of merit (P 2 L) 0.038 pb -1

8. C. Aidala, Transversity 2005, September 2005 8 A TT Proton Spin Structure at PHENIX Prompt Photon Production Heavy Flavors

9. C. Aidala, Transversity 2005, September 2005 9 Current Context for Transverse Measurements at PHENIX STAR and BRAHMS measurements at 200 GeV –Non-zero asymmetries for forward pions Coverage: STAR x F > 0.2, BRAHMS x F > 0.15 –Potential contributions from multiple mechanisms –A N consistent with zero for backward pions and forward protons HERMES and COMPASS Sivers and Collins results BELLE measurement of non-zero Collins FF for pions –Input for further interpretation of observed and future asymmetries!

10. C. Aidala, Transversity 2005, September 2005 10 ANAN x F *100 Transverse single-spin asymmetries for  +,  -, and proton production at BRAHMS Preliminary x F < 0 Raw asym Preliminary Raw asym p T (GeV/c) protons

11. C. Aidala, Transversity 2005, September 2005 11 A N of Mid-rapidity Neutral Pions and Charged Hadrons: Final Results hep-ex/0507073 Submitted to PRL |  | < 0.35 A N for both charged hadrons and neutral pions at mid-rapidity consistent with zero to within a few percent.

12. C. Aidala, Transversity 2005, September 2005 12 NLO pQCD consistent with data within theoretical uncertainties. PDF: CTEQ5M Fragmentation functions: Kniehl-Kramer-Potter (KKP)Kniehl-Kramer-Potter (KKP) Kretzer Spectrum constrains D(gluon  ) fragmentation function Factorization applicable, with small scale dependence hep-ex/0507073 |  | < 0.35 Mid-rapidity Cross Section Measurements 9.6% normalization error not shown PRL 91, 241803 (2003) |  | < 0.35 00

13. C. Aidala, Transversity 2005, September 2005 13 Mid-rapidity Partonic Processes Particle production at mid-rapidity at these transverse momentum values mostly from gluon scattering –A N results should constrain gluon Sivers (U. d’Alesio’s discussion) Future measurements reaching higher pT dominated by quark scattering, thus more sensitive to transversity + Collins Large asymmetries observed due to valence quarks?

14. C. Aidala, Transversity 2005, September 2005 14 Other (So Far Unpolarized) Mid-rapidity Measurements Direct  ’s (Published for p T < 7 GeV/c as Phys. Rev. D71:071102, 2005) PHENIX Preliminary  — Fit to data

15. C. Aidala, Transversity 2005, September 2005 15 Mid-rapidity Cross Sections (cont.) Non-photonic electrons

16. C. Aidala, Transversity 2005, September 2005 16 Forward-Backward Neutrons and Charged Particles Zero-degree calorimeters (ZDC) –Hadronic calorimeters –Neutrons, 4.7 < |  | < 5.6 Beam-beam counters (BBC) –Quartz Cherenkov detectors –Charged particles, 3.0 < |  | < 3.9

17. C. Aidala, Transversity 2005, September 2005 17 Forward neutrons (ZDC) at 200 and 410 GeV: A N ~ -11% Backward neutrons (ZDC): A N consistent with zero Neutron Asymmetry vs.   (Raw Asymmetry) / (beam pol.) Vertical polarization  Radial polarization

18. C. Aidala, Transversity 2005, September 2005 18 Inclusive forward charged particles (BBC): A N consistent with zero Forward charged (BBC) in forward-neutron- tagged (ZDC) events: Backward charged (BBC) in forward-neutron- tagged (ZDC) events: Forward-Backward Neutrons and Charged Particles (cont.) p N*(  *)  n+X Y Diffractive-like process? A N (X) 0

19. C. Aidala, Transversity 2005, September 2005 19 Upcoming Transverse Spin Measurements at PHENIX 2005 data –Similar transverse statistics to 2001-02, but ~3x higher polarization –Improved mid-rapidity measurements of  0, h +/- A N –More detailed study of forward and backward neutrons at 200 and 410 GeV –Forward and backward stopped hadrons (mostly pi and K) –A N of forward and backward muons

20. C. Aidala, Transversity 2005, September 2005 20 2005 Expected Muon Measurements Single inclusive muons from 2005 data –Mostly pion and kaon decays –p T 0.5-5.0 GeV/c –x F 0.02-0.11 GeV/c More data in the future will allow access to higher x F –1.2 < |  | < 2.4 –Eventually separate into prompt muons (heavy flavor) and muons from light meson decays Decay muons have enhanced K/  ratio, K/  ~ 1

21. C. Aidala, Transversity 2005, September 2005 21 Upcoming Transverse Spin Measurements at PHENIX (cont.) 2006 or 2007: Expect long spin run at RHIC –PHENIX anticipates 5-20(?) pb -1 transverse data, 60-70% polarization Depends on machine performance 2006 Beam-Use Proposal under development this month  studies A N of mid-rapidity single electrons—open charm Forward-backward single muon studies to higher x F Forward-backward J/  A N (note forward cross section already published) A TT measurements possible (but not yet for DY) Back-to-back jets to probe Sivers –Because of PHENIX central arm acceptance, better to run with radial than vertical polarization

22. C. Aidala, Transversity 2005, September 2005 22 Jet Asymmetry Due to Sivers Non-zero Sivers function implies spin- dependence in k T distributions of partons within proton Would lead to an asymmetry in  of back- to-back jets Trigger doesn’t have to be a jet or leading particle, but does have to be a good jet proxy –Studies being done for high-p T photon + away- side charged hadron 00 22  h Boer and Vogelsang, Phys.Rev.D69:094025,2004 anti-aligned aligned Run03  -charged dn/d  (Schematic)

23. C. Aidala, Transversity 2005, September 2005 23 Di-Hadrons vs. Di-Jets up down unpolarized away side parton ANAN di-hadron di-jet Don’t reconstruct jets fully—use di-hadron correlations to measure jet . Smears out di-hadron A N relative to the di-jet A N, with smearing function g (assumed here to be a gaussian, with  jT =0.35). Broadens and slightly lowers asymmetry, but still measurable

24. C. Aidala, Transversity 2005, September 2005 24 PHENIX Detector Upgrades (longitudinal) Also: silicon endcaps covering muon arm acceptance (1.2 < |  | < 2.4) - forward-backward charm and B physics hadron-blind detector for 2  electron coverage at mid-rapidity - open charm, electronic decays of J/ , ,... Transverse spin possibilities with planned upgrades not yet fully explored!

25. C. Aidala, Transversity 2005, September 2005 25 Summary Final 2002 PHENIX results for mid-rapidity  0 and charged hadron asymmetries now available (hep-ex/0507073) –consistent with zero within a few percent PHENIX forward neutron asymmetry of -11% observed at 200 and 400 GeV –Backward neutron asymmetry consistent with zero Significant non-zero results for forward and backward charged particles in events with a forward neutron

26. C. Aidala, Transversity 2005, September 2005 26 Summary (cont.) Muon arm results expected from 2005 data Di-jet Sivers measurement expected 2006 or 2007 Forward upgrades will improve access to kinematic region where large asymmetries have been observed Mid-rapidity upgrades will improve jet measurements Present RHIC results at forward, backward, and mid- rapidity suggest large SSA’s a valence quark effect? –Significance of BRAHMS zero proton asymmetries? Some overlapping, some complementary coverage and capabilities of PHENIX with other experiments should allow upcoming measurements to gradually put together a cohesive picture of proton transverse spin structure

27. C. Aidala, Transversity 2005, September 2005 27 Extra Slides

28. C. Aidala, Transversity 2005, September 2005 28 Single Transverse Collision Hard Scattering Process X q(x 1 ) g(x 2 ) left right

29. C. Aidala, Transversity 2005, September 2005 29 Unpolarized Results from Run03 p+p anti-aligned aligned Asymmetry numerator is difference between aligned and anti-aligned  dist’s, where aligned means trigger jet and spin in same direction denominator is simply unpolarized  distribution On left are some theoretical guesses on expected magnitude of AN from Siver’s On right are gamma-charged hadron  dist’s from Run03 p+p 2.25 GeV gamma’s as jet trigger, 0.6-4.0 GeV charged hadrons to map out jet shape Dotted lines are schematic effect on away side  dist due to Siver’s Fn (not to scale) Run03  -charged dn/d  Boer and Vogelsang, PRD69:094025,2004

30. C. Aidala, Transversity 2005, September 2005 30    Obtaining the (Spin-Dependent)  0 Yields 18M events used Central spectrometer arms |  | < 0.35 –  0 via  0  –Electromagnetic calorimeter (EMCal) Lead scintillator calorimeter (PbSc) Lead glass calorimeter (PbGl)  0 width ~10-15 MeV/c 2

31. C. Aidala, Transversity 2005, September 2005 31 EMCal-RICH Trigger 2x2 tower non- overlapping energy sum Threshold ~ 0.8 GeV Also used in conjunction with RICH to form an electron trigger 2x2 Trigger in 2001-2002 run. 

32. C. Aidala, Transversity 2005, September 2005 32 Handling Background in the  0 Asymmetry Invariant mass (GeV/c 2 ) - 50-MeV/c 2 windows around the  0 peak (60-110 and 170-220 MeV/c 2 ) - 250-450 MeV/c 2 (between  0 and  ) Eliminate as much background as possible using EMCal cluster shower shape cut and charged veto Calculate asymmetry of (signal + background) in the  0 mass window Calculate the asymmetry of two different background regions as an estimate of the asymmetry of the background under the peak Subtract the asymmetries

33. C. Aidala, Transversity 2005, September 2005 33 Obtaining Charged Hadron Yields 13M events used Event vertex from BBC’s Track reconstruction from –vertex –drift chamber –pad chambers BBC PC1 PC3 DC

34. C. Aidala, Transversity 2005, September 2005 34 Background in h + /h - Sample Note that tracking detectors in PHENIX are outside the magnetic field Assume track originates at event vertex, then measure momentum based on deflection angle observed at drift chamber Low-momentum tracks that don’t originate from the vertex may be misreconstructed with higher momentum –Conversion electrons –Decay products from long-lived particles (K +-, K 0 L )

35. C. Aidala, Transversity 2005, September 2005 35 Background in h + /h - Sample (cont.) RICH veto to eliminate electrons –Electron threshold 0.017 GeV/c –Pion threshold 4.7 GeV/c –< 1% electron contamination in final sample Estimate decay background from long-lived particles from tracks with reconstructed p T > 9 GeV/c but that didn’t produce a hit in the RICH –< 5% in final sample

36. C. Aidala, Transversity 2005, September 2005 36 A N of Neutral Pions and Charged Hadrons: Systematic Checks Independent results from two polarized beams Independent results from two detector arms (luminosity formula) Comparison of square-root and luminosity formulas Fill-by-fill stability of asymmetry Effects of background on  0 asymmetry –Integrate over different ranges of photon-pair invariant mass –Measure and subtract asymmetry of two different background invariant-mass regions

37. C. Aidala, Transversity 2005, September 2005 37 Forward Neutron Asymmetry at RHIC Large and negative (-11%) Observed at 200 and 410 GeV ~Zero for backward neutrons Why large asymmetry for forward neutrons but not forward protons?? (But admittedly not same kinematics) A N =  0.110±0.015 preliminary

38. C. Aidala, Transversity 2005, September 2005 38 BBC Asymmetry Forward neutron, forward BBC, left-right -  9  ! Forward neutron, backward BBC, left-right - No significant asymmetry in backward ZDC tagged data or in top-bottom asymmetry. Systematic error doesn’t include A N CNI error. K.Tanida p N*(  *)  n+X Y Diffractive-like process A N (X) 0 p n X kick-out/recoil picture A N (X) > 0, A N (Y)??

39. C. Aidala, Transversity 2005, September 2005 39 Converter subtraction method We defined as P : the yield of the photonic component N : the yield of the non-photonic component A : All electron yield in the non-converter data set C : All electron yield in the converter data set Rsim : the ratio of the photonic electron in converter to non-converter data set The following relation holds between those variables C = Rsim * P + N A = P + N Therefore P and N can be determined as P = ( C – A ) / ( Rsim – 1) N = ( Rsim * A – C ) / ( Rsim – 1) ** All parameter have pt dependence.