1 / 39

Transverse Spin at Results and Prospects

Transverse Spin at Results and Prospects. Columbia University. Christine Aidala. Transversity 2005, Como. September 2005. RHIC’s Experiments. Also pp2pp, pC, and polarized H jet polarimeters studying polarized elastic scattering. Transverse spin only (No rotators).

casey
Download Presentation

Transverse Spin at Results and Prospects

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

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

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

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

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

  5. The PHENIX Detector • Philosophy: • High rate capability & granularity • Good mass resolution and particle ID • Sacrifice acceptance • 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 C. Aidala, Transversity 2005, September 2005

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

  7. 2001-2 Transversely polarized p+p collisions Average polarization of ~15% Integrated luminosity 150 nb-1 Figure of merit (P2L) 3.38 nb-1 2003 Longitudinally polarized p+p collisions achieved Average polarization of ~27% Integrated luminosity 220 nb-1 Figure of merit (P4L) 1.17 nb-1 2004 5 weeks commissioning, 4 days data-taking Average polarization ~40% Integrated luminosity 75 nb-1 Figure of merit (P4L) 1.92 nb-1 2005 Average polarization ~48% Integrated longitudinal lumi 3.59 pb-1 Figure of merit (P4L) ~1.9 pb-1 Integ. transverse lumi 0.163 pb-1 Figure of merit (P2L) 0.038 pb-1 Spin Running at PHENIX So Far C. Aidala, Transversity 2005, September 2005

  8. Production Heavy Flavors Prompt Photon Proton Spin Structure at PHENIX ATT 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 xF > 0.2, BRAHMS xF > 0.15 • Potential contributions from multiple mechanisms • AN 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! C. Aidala, Transversity 2005, September 2005

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

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

  12. |h| < 0.35 hep-ex/0507073 Mid-rapidity Cross Section Measurements PRL 91, 241803 (2003) • NLO pQCD consistent with data within theoretical uncertainties. • PDF: CTEQ5M • Fragmentation functions: • Kniehl-Kramer-Potter (KKP) • Kretzer • Spectrum constrains D(gluon p) fragmentation function • Factorization applicable, with small scale dependence p0 |h| < 0.35 9.6% normalization error not shown C. Aidala, Transversity 2005, September 2005

  13. Mid-rapidity Partonic Processes Large asymmetries observed due to valence quarks? • Particle production at mid-rapidity at these transverse momentum values mostly from gluon scattering • AN 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 C. Aidala, Transversity 2005, September 2005

  14. Other (So Far Unpolarized) Mid-rapidity Measurements h — Fit to data Direct g’s (Published for pT < 7 GeV/c as Phys. Rev. D71:071102, 2005) PHENIX Preliminary C. Aidala, Transversity 2005, September 2005

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

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

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

  18. Diffractive-like process? Y p N*(D*)  n+X AN(X) < 0, AN(Y) > 0 Forward-Backward Neutrons and Charged Particles (cont.) • Inclusive forward charged particles (BBC): AN consistent with zero • Forward charged (BBC) in forward-neutron-tagged (ZDC) events: • Backward charged (BBC) in forward-neutron-tagged (ZDC) events: 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 p0, h+/- AN • More detailed study of forward and backward neutrons at 200 and 410 GeV • Forward and backward stopped hadrons (mostly pi and K) • AN of forward and backward muons C. Aidala, Transversity 2005, September 2005

  20. 2005 Expected Muon Measurements • Single inclusive muons from 2005 data • Mostly pion and kaon decays • pT 0.5-5.0 GeV/c • xF 0.02-0.11 GeV/c • More data in the future will allow access to higher xF • 1.2 < |h| < 2.4 • Eventually separate into prompt muons (heavy flavor) and muons from light meson decays • Decay muons have enhanced K/p ratio, K/p ~ 1 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 • L studies • AN of mid-rapidity single electrons—open charm • Forward-backward single muon studies to higher xF • Forward-backward J/Y AN (note forward cross section already published) • ATT 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 C. Aidala, Transversity 2005, September 2005

  22. Run03 -charged dn/d anti-aligned aligned 2 0  h Jet Asymmetry Due to Sivers Boer and Vogelsang, Phys.Rev.D69:094025,2004 • Non-zero Sivers function implies spin-dependence in kT distributions of partons within proton • Would lead to an asymmetry in Df 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-pT photon + away-side charged hadron (Schematic) C. Aidala, Transversity 2005, September 2005

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

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

  25. Summary • Final 2002 PHENIX results for mid-rapidity p0 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 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 C. Aidala, Transversity 2005, September 2005

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

  28. q(x1) Hard Scattering Process X g(x2) left right Single Transverse Collision C. Aidala, Transversity 2005, September 2005

  29. Unpolarized Results from Run03 p+p Boer and Vogelsang, PRD69:094025,2004 Run03 -charged dn/d 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) C. Aidala, Transversity 2005, September 2005

  30. p0  Obtaining the (Spin-Dependent) p0 Yields • 18M events used • Central spectrometer arms |h| < 0.35 • g, p0 via p0  gg • Electromagnetic calorimeter (EMCal) • Lead scintillator calorimeter (PbSc) • Lead glass calorimeter (PbGl) p0 width ~10-15 MeV/c2 C. Aidala, Transversity 2005, September 2005

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

  32. Handling Background in the p0 Asymmetry • Eliminate as much background as possible using EMCal cluster shower shape cut and charged veto • Calculate asymmetry of (signal + background) in the p0 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 Invariant mass (GeV/c2) - 50-MeV/c2 windows around the p0 peak (60-110 and 170-220 MeV/c2) - 250-450 MeV/c2 (between p0 and h) 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 PC3 PC3 DC DC BBC PC1 PC1 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+-, K0L) 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 pT > 9 GeV/c but that didn’t produce a hit in the RICH • < 5% in final sample C. Aidala, Transversity 2005, September 2005

  36. AN 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 p0 asymmetry • Integrate over different ranges of photon-pair invariant mass • Measure and subtract asymmetry of two different background invariant-mass regions C. Aidala, Transversity 2005, September 2005

  37. AN = 0.110±0.015 preliminary 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) C. Aidala, Transversity 2005, September 2005

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

More Related