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Advancing ΔG Measurement with Heavy Quark Production at PHENIX: Status, Probes, and Predictions

This paper discusses the measurement of ΔG (gluon polarization) through heavy quark production at PHENIX. Topics covered include the status of the measurement, probes for ΔG, experimental errors, background reduction strategies, and sensitivity analysis. Various models (GS-A, GS-B, GS-C) are used for prediction, and simulations with event generators like PYTHIA are employed. The study aims to estimate statistical and systematic errors and enhance the understanding of gluon spin.

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Advancing ΔG Measurement with Heavy Quark Production at PHENIX: Status, Probes, and Predictions

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  1. ΔGMeasurement with the Heavy Quark Production Hiroki Sato Kyoto Univ./RIKEN PHENIX November Core • ΔG Status and probes for it • Prediction of ALL in the PHENIX • ALL uncertainties and ΔG sensitivity • J/ • e pair • single electron • Reduction of electron background • Summary PHENIX November Core

  2. Status of ΔG Measurement quark spin gluon spin proton spin orbital angular moment ～0.3 1/2 = (1/2)+G+L+LG Polarized Deep Inelastic Scattering ΔG Altarelli. et.al (1997)Q2= E155(1999) Q2=5GeV2 SMC(1997) Q2=10GeV2 Large uncertainty for indirect measurement Direct measurement with polarized p-p collisions（RHIC） PHENIX November Core

  3. Gluon Compton High-pT prompt  Charmonium Production e+e-, +- Open Heavy Quark Production e+e-, +- ,e high-pT single e, eD, D simulation ALL G(x) ? Probes for ΔG Measurement Experiment PHENIX November Core

  4. Simulations • Purposes • ALL expectation with PHENIX using some models of G(GS-A,B,and C) • Yield and background study → estimation of statistical and systematic errors. • PYTHIA 5.7 with GRV94-LO and JETSET 7.3 for event generation. • s=200GeV • Simple acceptance cut (||<0.35 for Central Arms and 1.1<||<2.3 for Muon Arms) • normalization to 32 or 320pb-1 PHENIX November Core

  5. ALLpp→bbＸ ALL μ e ALL Prediction at PHENIX T.Gehmann and W.J.Stirling(1995) M.Karliner and R.W.Robinett(1993) aLL ΔG（ｘ） 1.71 1.63 1.02 1.5 2 5 x cos* GRV-94 LO for unpol.PDF GS-A GS-B GS-C Me(GeV) PHENIX November Core

  6. ALL Experimental Errors PB1,2Beam Polarization　～　0.7(RHIC) N++（N+－）Number of events L++（L+－）Luminosity • Statistical Error • Systematic Errors • PB１,2→ ALL/ALL ~20% • (L+－/L++) → ALL~10ｰ4 • Nbg/Nsig ,ALLbg +‐: Beam Helicity PHENIX November Core

  7. Dimuons 320pb-1 s=200GeV pT()>2GeV/c J/ （color singlet model） Yield per Bin(0.2GeV/c2) bottom /K M(GeV/c2) NJ/(pT>2GeV)~120k events →ALLJ/(stat.)~ 0.006 N/K/NJ/~ 0.15 ALL/K ~0.007 → ALL J/(syst.)~0.001 ALLJ/ production mechanism of the charmonium G PHENIX November Core

  8. e pairs 320pb-1 s=200GeV pTe,pT>1GeV/c total _ cc→e /K→e Yield per 1GeV/c2 _ bb→e • background of electrons (0Dalitz decay and  conversion) can be reduced • b/c separation is under studying → important because ALL is different Meμ Me(GeV/c2) Me(GeV/c2) Nbb→eμ~120k events→ ALL(stat.)~ 0.006 Ncc→eμ~100k events ALL(syst.)~0.006 N/K→eμ~60k events Sensitive enough to distinguish GS-A,B and C PHENIX November Core

  9. bbe (pTe,pT >1GeV/c) X2 P(GeV/c) e pairsxregion X2 X1 Central Arm ｂ→e proton x1P ｂ→ x2P Muon Arm Correlation is small because of decay kinematics PHENIX November Core

  10. bbe (pTe,pT >1GeV/c) ALL Stat. Error 0.031 0.014 0.012 0.014 0.017 GS-A GS-B GS-C e pairs sensitivity 320pb-1 s=200GeV Background reduction  • Smaller systematic error • Larger statistics with low pT events Meμ Systematic error is comparable to statistical error PHENIX November Core

  11. pTe>1GeV/c 0->eX Assuming MVD efficiency is 90% 0 Dalitz reduction with the isolation cut with MVD • Another charged particle (pT>10MeV) in the cone of an electron → regard it as a 0 e+ or e- cc->eX 85% reduction can be achieved by the 10 degree cone cut for pTe>1GeV/c Detector simulation is needed for more realistic study PHENIX November Core

  12. 2229 601 1214 487  conversion reduction Akiba, 1997 Akiba 1997 • Comparable to Dalitz decay contribution • Origin • beam pipe (26%) - can be reduced by the isolation cut with MVD • MVD (53%) • inner barrel - reject 2-MIP events • outer barrel - require hits in the inner shell • MVD shell (21%) - require hits in MVD cm PHENIX November Core

  13. SingleElectrons Akiba,1996 Arbitrary unit With 32pb-1 luminosity (10% of full) and pTe>1GeV/c, • Charm 3.1M, min.bias 12M →1.8M(0 reduction) events • ALL(stat.)~0.001, ALL(syst.)~0.001 (ALL(GS-A)~ -0.04) →excellent measurement! 0 Dalitz charm pT in GeV/c PHENIX November Core

  14. Other probes • Di-electrons • Small Dalitz decay background • ~100k J/’s (pTe>0.4GeV/c) at 320pb-1 with the color-singlet model • open c/b is possible? • eD (D) pairs • identified with eK coincidence (peak in K invariant mass) • 31k events with 320pb-1 (pTe>0.4GeV/c) • strong charm ID → confirmation of open charm yield • Single muons • large statistics, but it’s crucial to reject decay hadrons before the nosecone. PHENIX November Core

  15. Summary and Conclusion • We can get many inputs on the gluon polarization from the asymmetry for heavy quarks using their (semi)leptonic decay channels. • Future Work • Separation of bottom/charm → important for e pairs (pTe,>1GeV/c). • Full simulation is needed for more realistic estimation of the Dalitz/conversion background reduction. • Electron trigger is needed → Ken Barish (UCR) and Matthias G.-Perdekamp(RBRC) work on this from spin side *with color octet model PHENIX November Core

  16. ...Backup slides... PHENIX November Core

  17. Muon Arm Performance • 1.1<||<2.4, absorber~10λint (pz cut~2GeV/c) • Detector acceptance~0.7 • Muon Tracking Chambers in Muon Magnet • 3 stations • x~100m →Δp/p~3% (@3~10GeV/c) • Muon Identifier • hadron rejection with 5 layers of Iarocci tubes and Steel Iarocci tube PHENIX November Core

  18. MuID Performance Test@KEK • Hadron rejection = Central Magnet MuID For 5GeV/c pions, 0.0050.04(South)= 210-4 < 210-3 (Decay before Central Magnet) Fraction of remainingp PHENIX November Core

  19. PHENIX Muon Simulation • Purpose • Estimation of signal and background • Evaluation of the detector response and reconstructionperformance • Procedure • Event generation(PYTHIA) p p s = 200GeV • Detector simulation Full GEANT • Reconstruction • Normalized to RHIC Luminosity • 32pb-1(year2000) • 320pb-1（year2001） PHENIX November Core

  20. Single  320pb-1 → • Contribution of  decay and b-quark is comparable for pT>6 GeV/c. • Uncertainty of the cross section of heavy quarks → measurement may be possible. c→ b→ PHENIX November Core

  21. Dielectrons Akiba 1996 PHENIX November Core

  22. PYTHIA charm PYTHIA bottom s=200GeV Open Heavy Quark Production 200b • PYTHIA(GRV-94LO) agrees with experimental data at lower energies (s < 50GeV) • Large theoretical uncertainties (30b<(cc)<3mb and 0.7b<(bb)<5b at s=200GeV) 0.7b 。 E789 PHENIX November Core

  23. Open heavy cross section II( higher s) • For b-quark production, PYTHIA agrees with D0 data within factor 2 ( at s=1.8TeV) • (pp→bbX),s=630GeV UA110.23.3b PYTHIA(GRV94-LO) 7.3b PHENIX November Core

  24. Invariant cross section of charged hadrons in pp collisions at s=200GeV Charged Hadron Production • PYTHIA(GRV94-LO) and UA1 data are consistent within factor two. PHENIX November Core

  25. PYTHIA / ratio • ~104 at pT=2GeV/c hadrons c→ b→ PHENIX November Core

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