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Recent Results from the PHENIX Detector at RHIC

Recent Results from the PHENIX Detector at RHIC. Kieran Boyle (Stony Brook U.). Outline: Motivation RHIC and the PHENIX Detector A LL measurements ( D g) from Longitudinal Polarization Requirements Results Transverse Spin Physics Results. Hard Scattering Process. p 0. D g 2. D g D q.

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Recent Results from the PHENIX Detector at RHIC

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  1. Recent Results from the PHENIX Detector at RHIC Kieran Boyle (Stony Brook U.) • Outline: • Motivation • RHIC and the PHENIX Detector • ALL measurements (Dg) from Longitudinal Polarization • Requirements • Results • Transverse Spin Physics Results

  2. Hard Scattering Process p0 Dg2 DgDq Dq2 N++ - RN+- L++ 1 , R= N++ + RN+- L+- +- = + = ++ + P2 Double Helicity Spin Asymmetry with DS ~25%, Dg not well constrained DL ? Various channels can be used to probe Dg: • p0, p+, p- • direct photon • jets • Heavy flavor = agg * Dg2 + bgq * Dg Dq + cqq Dq2 P=polarization N = particle yield L = Luminosity

  3. RHIC BRAHMS & PP2PP (p) PHENIX (p) STAR (p) RHIC CNI (pC) Polarimeters Absolute Polarimeter (H jet) Siberian Snakes Spin Rotators Partial Siberian Snake LINAC BOOSTER Pol. Proton Source AGS AGS Internal Polarimeter 200 MeV Polarimeter Rf Dipoles * Longitudinal ** Not yet finalized

  4. PHENIX Detector BBC ZDC ZDC EMCal p0/g/h detection • Electromagnetic Calorimeter (PbSc/PbGl): • High pT photon trigger to collect p0's, h’s, g’s • Acceptance: |h|<0.35, f = 2 x p/2 • High granularity (~10*10mrad2) p+/ p- • Drift Chamber (DC) for Charged Tracks • Ring Imaging Cherenkov Detector (RICH) • High pT charged pions (pT>4.7 GeV). Relative Luminosity • Beam Beam Counter (BBC) • Acceptance: 3.0< h<3.9 • Zero Degree Calorimeter (ZDC) • Acceptance: ±2 mrad Local Polarimetry • ZDC LvL2 data filter • Filters “rare” events for fast analysis • pT>2.5 GeV photon for p0

  5. Relative Luminosity • Number of BBC triggered events used to determine Relative Luminosity. • For estimate of Uncertainty, fit where • Limited by ZDC statistics. * Longitudinal

  6. Use Zero Degree Calorimeter (ZDC) to measure a L-R and U-D asymmetry in forward neutrons (Acceptance: ±2 mrad). When transversely polarized, we see clear asymmetry. When longitudinally polarized, there should be no asymmetry. Local Polarimetry at PHENIX Raw asymmetry Raw asymmetry YELLOW BLUE f f Raw asymmetry Raw asymmetry YELLOW BLUE f f Idea: Use neutron asymmetry to study transversely polarized component.

  7. Measured Asymmetry During Longitudinal Running (2005) LR c2/NDF = 82.5/97 p0 = 0.00423±0.00057 c2/NDF = 88.1/97 p0 = -0.00323±0.00059 UD <PT/P>= 10.25±2.05(%) <PL/P> = 99.48±0.12±0.02(%) XF>0 XF>0 UD c2/NDF = 119.3/97 p0 = 0.00056±0.00063 LR c2/NDF = 81.7/97 p0 = -0.00026±0.00056 <PT/P>= 14.47±2.20(%) <PL/P> = 98.94±0.21±0.04(%) XF<0 XF<0 Fill Number Fill Number

  8. p0 Cross Section • Consistent with previous PHENIX results. • Extends previous results to pT of 20 GeV/c. • NLO pQCD Theory is consistent with data over nine orders of magnitude. • As theory agrees well with our data, we can use it to interpret our results in terms of Dg

  9. Calculating ALL • Calculate ALL(p0+BG) and ALL(BG) separately. • Get background ratio (wBG) from fit of all data. • Subtract ALL(BG) from ALL(p0+BG): ALL(p0+BG) = wp0· ALL(p0) + wBG · ALL(BG) Invariant Mass Spectrum p0+BG region : ±25 MeV around p0peak BG region : two 50 MeV regions around peak

  10. p0 ALL (s=200 GeV) • Run6 Data set from 2.0-2.7 times improvement on statistical uncertainties from Run5. • Variation due to LvL2 “turn on.” • Due to unreleased absolute polarizations, which scale ALL and which contain correlated and uncorrelated parts, we have not combined the two data sets. • Theoretical uncertainties are not taken into account (for now). • Run 6 rules out maximal gluon scenarios. • Expect clearer statement when lower pT data from Run6 is available Confidence Levels GRSV: M. Gluck, E. Reya, M. Stratmann, and W. Vogelsang, Phys. Rev. D 63 (2001) 094005.

  11. p0 ALL (s=62 GeV) • Converting to xT, we can get a better impression of the significance of the s=62 GeV data set, when compared with the Run5 preliminary data set. • dALL|R = 2.8x10-3. • p0 unpolarized cross section at s=62 GeV is not yet finished. • Not clear how well NLO pQCD describes our data. • Validity of comparison with expected ALL theory curves calculated from NLO pQCD is NOT clear. • Cross section result expected soon GRSV: M. Gluck, E. Reya, M. Stratmann, and W. Vogelsang, Phys. Rev. D 53 (1996) 4775.

  12. High pT Charged Pion Hard Scattering Process p+, p- Fraction of pion production Dg2 DgDq Dq2 • First “Proof of concept” measurement • Charged pions begin firing the RICH at pT~4.7 GeV, which is used for particle ID. • Expect Dg>0, then: ALL(p+)>ALL(p0)>ALL(p-)

  13. h ALL h Dg2 DgDq Dq2 • Independent measure for gluon polarization. • Analysis similar to p0 • h fragmentation function not available, so no expected ALL curves have been calculated.

  14. Run6 Projections p0 p— p+ h g

  15. Transverse Physics left right • Large Asymmetries at large xF at s~20 GeV from E704. • Large asymmetries remain at s=200 GeV for large xF . • Cause? • Sivers effect • left-right asymmetry in transverse momentum distribution of partons (“kT”) inside the transversely polarized nucleon • Transversity • transverse polarization of partons inside the transversely polarized nucleon • Higher Twist s = 200 GeV s = 19.4 GeV Phys.Rev.Lett. 92(2004) 171801

  16. AN of p0 and h± for h~0at Ös=200GeV π0 (2001/02) |h| < 0.35 Run 2 pt (GeV/c) pt (GeV/c) PRL 95(2005)202001 • P=15%, ~0.15pb-1 in Run2, P=47% in Run5 May provide information on gluon-Sivers effect • gg and qg processes are dominant (with small xB)

  17. New calorimeter added in Run6. 3.1 < |h| < 3.65 Only south arm in Run6, north just installed. Asymmetry seen in yellow beam (positive xF), but not in blue (negative xF) Only 10% of total statistics from 62 GeV Transverse Run Forward p0 at Ös=62 GeV Raw Asym. Raw Asym. XF>0 XF<0 f f

  18. Conclusions • At PHENIX, we are exploring proton spin through both transversely and longitudinally polarized proton collisions. • Longitudinal • p0 ALL at s=200 GeV excludes maximal gluon scenarios. • p0 ALL at s=62 GeV will allow us to probe a higher xT region • Many complementary analyses are on the way. • Transverse • Midrapidity p0 and charged hadron data may provide information on the gluon Sivers effect. • Significant Run6 transverse data. • L = 2.7 pb-1 • P = 57 % • FoM = LP2 =880nb-1 • Results expected soon.

  19. Backups

  20. Photon Trigger Efficiency

  21. Minimum Bias (BBC |z|<30) • Minimum Bias in coincidence with High Energy Photon trigger (Cluster Energy>1.4GeV)

  22. 200 GeV p0 ATT • Here • ATT • azimuthally independent double transverse spin asymmetry. • ALL background. • expected to be small, but previously unmeasured. • In Run5, PHENIX took a short transverse run specifically to measure ATT. • Consistent with zero.

  23. 62 GeV: Local Polarimetry Red : transverse data Blue : longitudinal data • Forward Neutron asymmetry reduced at 62 GeV, but still measurable. Blue Forward Blue Backward xpos xpos Yellow Forward Yellow Backward xpos xpos

  24. Direct photon g DgDq DqDq RUN5 hep-ex/0609031 signal isolated pi0 photon • First step, direct photon cross section using isolation cut. • Isolation cut: • ETot<0.1Ecandidate within 0.5 rad. • Background from merged p0 removed by shower shape (calibrated with test beam). • Background from isolated p0 photon <15% above 10 GeV. Gluon-photon compton dominant Asymmetry analysis underway. Results expected soon. Isolation cut R=0.5, f=0.1 minE=0.15GeV Pmin=0.2GeV Pmax=15GeV

  25. AN of J/yat Ös=200GeV • Transverse running in Run6: • L = 2.7 pb-1 • P = 57 % • FoM = LP2 =880nb-1 • J/y may be sensitive to gluon Sivers as produced through g-g fusion • Charm theory prediction is available • Open Question: How does J/y production affect prediction?

  26. Charged Pion pT spectrum

  27. Charged pion—Background • Use Power law fit. Conservative estimate of backgrounds.

  28. January 2006 MPC South Installation May 11, 1st0 peak • Muon Piston Calorimeter (MPC) Run06 Summary • Only South Side Installed, 192 PbWO4 crystals with APD readout • About 12 crystals did not function • Some problems with noisy crystals and electronics • Cannot fix since they are in an inaccessible region of the detector • Better than 80% of the acceptance is good.

  29. Forward neutrons charged particles neutron Run 5 • Discussed previously in terms of local polarimetry. • Forward neutron cross section in good agreement with ISR data. • Forward asymmetry calculated as a function of XF

  30. Uncertainty of ALL = +- = + = ++ + N++ - RN+- P=polarization N = particle yield L = Luminosity 1 • For ALL, detector efficiencies and acceptance cancel out. • Relative luminosity: • Polarization: • 20% relative uncertainty per beam—scales ALL and dALL similarly • Remaining transverse component can contribute to ALL as • From transverse asymmetry in forward neutron production, estimate Run5, both beams were ~99% longitudinally polarizede2<0.03 • ATT consistent with zero—Possible systematic contribution to ALL<0.05dATT. N++ + RN+- P2 * Longitudinal

  31. Di-Hadron Azimuthal Correlations Possible helicity dependence • We may observe net effect (after averaging over impact factor) Spin-correlated transverse momentum (orbital angular momentum) may contribute to jet kT. Run 5

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