1 RSC2006—Sept. 30, 2006 Kieran Boyle Recent Results from PHENIX Longitudinal Spin Program Kieran Boyle (Stony Brook U.) for the PHENIX Collaboration Outline: Quick Physics overview RHIC and PHENIX, and A LL requirements Run5 and Run6 new Results

2 RSC2006—Sept. 30, 2006 Kieran Boyle Motivation g2g2 gqgq q2q2 Hard Scattering Process with  ~20%,  g,  L not well constrained How to measure  g: 00 ~ a gg *  g 2 + b gq *  g + c qq

3 RSC2006—Sept. 30, 2006 Kieran Boyle A LL Requirements  Helicity Dependent Particle Yields  (Local) Polarimetry  Relative Luminosity (R=L ++ /L +- )  A LL ++ same helicity +  opposite helicity

4 RSC2006—Sept. 30, 2006 Kieran Boyle RHIC BRAHMS & PP2PP (p) STAR (p) PHENIX (p) AGS LINAC BOOSTER Pol. Proton Source Spin Rotators Partial Siberian Snake Siberian Snakes 200 MeV Polarimeter AGS Internal Polarimeter Rf Dipoles RHIC CNI (pC) Polarimeters Absolute Polarimeter (H jet) Year[GeV]Luminosity [pb -1 ] (recorded)Polarization [%]Figure of Merit (P 4 L) 2005 * * * ** ** * Longitudinal ** Not yet finalized

5 RSC2006—Sept. 30, 2006 Kieran Boyle PHENIX Detector    detection Electromagnetic Calorimeter (PbSc/PbGl): High p T photon trigger to collect  0 's,  ’s,  ’s Acceptance:  x  High granularity (~10*10mrad2)     Drift Chamber (DC)/Ring Imaging Cherenkov Counter (RICH) High p T charged pions (p T >4.7 GeV). J  Muon Id/Muon Tracker Multiple muon triggers. Relative Luminosity Beam Beam Counter (BBC) Acceptance: 3.0<  3.9 Zero Degree Calorimeter (ZDC) Acceptance: ±2 mrad Local Polarimetry ZDC LvL2 data filter Filters “rare” events for fast analysis Dimuon for J/Y p T >2.5 GeV photon for  0 BBC ZDC

6 RSC2006—Sept. 30, 2006 Kieran Boyle Local Polarimetry at PHENIX 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. BLUE YELLOW Raw asymmetry  Idea: Use neutron asymmetry to study transversely polarized component. BLUE YELLOW Raw asymmetry 

7 RSC2006—Sept. 30, 2006 Kieran Boyle Measured Asymmetry During Longitudinal Running (2005) = 10.25±2.05(%) = 99.48±0.12±0.02(%) = 14.47±2.20(%) = 98.94±0.21±0.04(%)  2 /NDF = 88.1/97 p0 = ±  2 /NDF = 82.5/97 p0 = ± LR UD X F >0 X F <0  2 /NDF = 119.3/97 p0 = ±  2 /NDF = 81.7/97 p0 = ± Fill Number

8 RSC2006—Sept. 30, 2006 Kieran Boyle A TT Here A TT –azimuthally independent double transverse spin asymmetry. –A LL background. –expected to be small, but previously unmeasured. In Run5, PHENIX took a short transverse run specifically to measure A TT. Consistent with zero.

9 RSC2006—Sept. 30, 2006 Kieran Boyle Relative Luminosity Number of BBC triggered events used to calculate Relative Luminosity. For estimate of Uncertainty, fit where Limited by ZDC statistics. Year[GeV] RR  A LL 2005 *2001.0e-42.3e *2001.1e-41.5e * e-32.8e-3 * Longitudinal

10 RSC2006—Sept. 30, 2006 Kieran Boyle A LL From Run5 and Run6, we are currently studying an array of probes: –       – Direct photon –  – multiparticle “cone” –J/  g2g2 gqgq q2q2 Hard Scattering Process probe

11 RSC2006—Sept. 30, 2006 Kieran Boyle Calculating  0 A LL 1.Calculate A LL (  +BG) and A LL (BG) separately. 2.Get background ratio (w BG ) from fit of all data. 3.Subtract A LL (BG) from A LL (  +BG): A LL (  +BG) = w  · A LL (  ) + w BG · A LL (BG) This method is also used for other probes with two particle decay mode: , J/ 

12 RSC2006—Sept. 30, 2006 Kieran Boyle  0 in Run6 In Run6, there were two separate longitudinal running periods: –April 27-June  s=200 GeV –June 12-June  s=62.4 GeV  s=62.4 GeV –Due to the small size of the  s=62 GeV data set, we were able to finish production and measure  0 A LL.  s=200 GeV –As was mentioned earlier, PHENIX filters data for rare signals. –In Run6, we have also used this filtered data (here, for high p T photons) to produce a high p T  0 A  s=200 GeV with much improved uncertainties compared to Run5.

13 RSC2006—Sept. 30, 2006 Kieran Boyle 62 GeV Initial, 62 GeV p+p was needed for heavy ion comparison. Thanks to CAD, we were able to get longitudinally polarized beam at PHENIX.

14 RSC2006—Sept. 30, 2006 Kieran Boyle But why? By definition: Measuring  0 A LL at  s=62.4 GeV allows us to test a higher x T range with lower statistics than currently possible at  s=200 GeV. As stated earlier, uncertainty in A 62 GeV due to relative luminosity is 2.8x10 -3, which is less than our statistical uncertanty.

15 RSC2006—Sept. 30, 2006 Kieran Boyle 62 GeV: Local Polarimetry Forward Neutron asymmetry reduced at 62 GeV, but still measurable. xpos Red : transverse data Blue : longitudinal data Blue Forward Blue Backward Yellow Backward Yellow Forward BLUE0.065 ± YELLOW0.132 ± BLUE ± YELLOW ± P L BLUE 100% – 2.3% P L YELLOW 100% – 2.2%

16 RSC2006—Sept. 30, 2006 Kieran Boyle 62 GeV Results A TT still to be measured with short transverse data set taken during rotator commisioning. –Assume remaining transverse component ~21% – A TT ~ 0.04A TT contribution to measured A LL  0 unpolarized cross section at  s=62 GeV is not yet finished. –Unclear how well NLO pQCD describes our data. –Validity of comparison with expected A LL theory curves calculated from NLO pQCD is NOT clear. –Result expected soon

17 RSC2006—Sept. 30, 2006 Kieran Boyle  0  s=62 GeV As there is no cross section at  s=62 GeV, we do not calculate confidence levels. Grey band is systematic uncertainty from relative luminosity, which is independent of p T. GRSV: M. Gluck, E. Reya, M. Stratmann, and W. Vogelsang, Phys. Rev. D 53 (1996) 4775.

18 RSC2006—Sept. 30, 2006 Kieran Boyle Comparison with 200 GeV Converting to x T, we can get a better impression of the significance of the  s=62 GeV data set, when compared with the Run5 preliminary data set. Awaits the unpolarized cross section for estimating 62 GeV significance.

19 RSC2006—Sept. 30, 2006 Kieran Boyle 200 GeV As shown earlier, the Run6 longitudinal data set had a figure of merit 7.5 times that of Run5. Use data filtered for high p T photon. –Due to low efficiency in our filter at medium p T  0 ’s data for p T <5 GeV is statistically limited. We only show data with p T >5 GeV. Uncertainty from relative luminosity for the sqrt(s)=200 GeV longitudinal running period gives an uncertainty in A LL of 1.5e-4. For local polarimetry, we need full production. –Currents for Rotator and Main magnets for both STAR and PHENIX are monitored during the run –Enough historical evidence exists for understanding spin direction and magnet current correlation. –Conclude that spin orientation is fine.

20 RSC2006—Sept. 30, 2006 Kieran Boyle Run5  0 Cross Section Consistent with previous results. Extends previous results to p T of 20 GeV/c. Theory is consistent with data over nine orders of magnitude.

21 RSC2006—Sept. 30, 2006 Kieran Boyle Run6  0 A LL (200 GeV) Run6 Data set from times improvement on statistical uncertainties from Run5. Variation due to LvL2 “turn on.” Due to unreleased absolute polarizations, which act a scale factor in A LL and which contain correlated and uncorrelated part, we have not combined the two data sets. For confidence levels, assume complete correlation. GRSV: M. Gluck, E. Reya, M. Stratmann, and W. Vogelsang, Phys. Rev. D 53 (1996) 4775.

22 RSC2006—Sept. 30, 2006 Kieran Boyle What about  g? Confidence levels from a simple  2 test between our data and the four curves plotted. Theoretical uncertainties are not taken into account. C.L. (%) Theory modelRun5Run6Run5&Run6 GRSV-std *GRSV-max (  g=g) *GRSV  g= *GRSV  g=−g Run 6 rules out maximal gluon scenarios. Expect clearer statement when lower p T data from Run6 is available.

23 RSC2006—Sept. 30, 2006 Kieran Boyle What about  g? To remove possibility that soft physics is influencing the result through the pT<2 data, we calculated confidence levels excluding this point. Theoretical uncertainties are not taken into account. C.L. (%) Theory modelRun5Run6Run5&Run6Run5&Run6 (p T >2 GeV) GRSV-std *GRSV-max (  g=g) *GRSV  g= *GRSV  g=−g No significant difference seen. Expect clearer statement when lower p T data from Run6 is available. More detailed analysis of  g constraint underway.

24 RSC2006—Sept. 30, 2006 Kieran Boyle High p T Charged Pion g2g2 gqgq q2q2 Hard Scattering Process  +,  - First “Proof of concept” measurement Charged pions begin firing the RICH at p T ~4.7 GeV, which is used for particle ID. Higher p T more sensitive to gluon polarization. See A. Moreale’s talk

25 RSC2006—Sept. 30, 2006 Kieran Boyle p+p   + X Similar analysis technique as with  0, using two photon decay channel. Independent measure for gluon polarization. See F. Ellinghaus’ talk later today. g2g2 gqgq q2q2 Hard Scattering Process 

26 RSC2006—Sept. 30, 2006 Kieran Boyle Multiparticle A LL Definition of p T cone: sum of p T measured by EMCal and tracker with R =  (|  | 2 +|  | 2 ) < 0.3 rad. Relationship between p T cone and p T jet is evaluated with PYTHIA and GEANT. See K. Nakano’s talk. Hard Scattering Process g2g2 gqgq q2q2

27 RSC2006—Sept. 30, 2006 Kieran Boyle J/  (Run5 & Run6) New Run6 result from LvL2 filtered data –LvL2 filters data on defined rare condition –Here, LvL2 uses dimuon event. Shows clear improvement over Run5. Second year in which J/  has been measured using LvL2 filtered data. See M. Liu’s talk

28 RSC2006—Sept. 30, 2006 Kieran Boyle Direct photon First step, direct photon cross section using isolation cut. Isolation cut: –E Tot <0.1E candidate within 0.5 rad. Isolation cut R=0.5, f=0.1 minE=0.15GeV Pmin=0.2GeV Pmax=15GeV gqgq Hard Scattering Process  qqqq Gluon-photon compton dominant hep-ex/ RUN5

29 RSC2006—Sept. 30, 2006 Kieran Boyle Direct photon Background from merged  0 removed by shower shape (calibrated with test beam). Background from isolated  0 photon <15% above 10 GeV. Asymmetry analysis underway. Results expected soon. See T. Horaguchi’s talk. isolated pi0 photon signal

30 RSC2006—Sept. 30, 2006 Kieran Boyle Conclusions PHENIX is well positioned to constrain  g with a new significantly better data set from Run6. Many other complimentary analyses are on the way. 62 GeV data give information at higher x T, and may give powerful independent constraint on  g.