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STAR Spin Analysis Update Stephen Trentalange

STAR Spin Analysis Update Stephen Trentalange. Beam-Beam Counters . - scintillator annulus installed around the beam pipe, on the east and west poletips of STAR magnet at ±3.74m from IR for detection of charged particles in forward region 2 < | h | < 5 .

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STAR Spin Analysis Update Stephen Trentalange

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  1. STAR Spin Analysis Update Stephen Trentalange

  2. Beam-Beam Counters - scintillator annulusinstalled around the beam pipe, on the east and west poletips of STAR magnet at ±3.74m from IR for detection of charged particles in forward region 2 < |h| < 5 Small hexagonal annulus: 18 pixels (16 PMT) covering 3.3<|h|< 5.0 and 0<j <2p - azimuthal segmentation ! ~2m A coincidence condition between BBC East and West - suppresses beam-gas background and used for: - triggering in pp (minimum bias, jet triggers), - (relative) luminosity measurements - local polarimetery ~0.5m ADC (PMT Sum) Data MC BBC cross section: s(BBC) ~ 50% of tot (pp) = 26 mb Large! - Van der Meer scans at RHIC ( Run2 and Run3 data) are consistent with Geant simulations for STAR Data and MC agree

  3. Transverse Single Spin Asymmetries Asymmetries measured for p+p -> A + X,where A – hit(s) in the BBC (small tiles, 3.3<|h|< 5.0) Number of counts from the BBC (L,R,T,B) sorted by beam polarization states Example:Polarized Yellow beam (sum over Blue beam polarization states) heads towards BBC East RHIC CNI polarimeter Zero at RHIC (Vertical pol) NL(R,T,B) -nr of counts from BBC East or West in Left, Right, Top, Bottom part counted every bunch crossing by scaler system ] + + Top Left Right X Bottom Interaction Vertex BBC East BBC West

  4. Local Polarimetry Rotators OFF ON CNI polarimeter non-zero non-zero BBC Left-Right ( vertical ) NON_ZERO ZERO BBC Top-Bottom ( radial ) zero zero e CNI (ON-LINE) eLR BBC= - 0.07(2) eTB BBC = - 0.04(2) e CNI (ON-LINE) eLR BBC = 0.13(2) eTB BBC = -0.24(2) Yellow beam, BBC East Blue beam, BBC West CNI CNI Measured asymmetry drop drop BBC BBC Run# Run# OFF Rotators ON OFF Rotators ON Spin rotators worked as designed and stable, BBC worked very well as a local polarimeter - vertical and radial polarization components smaller than 3% Longitudinal polarization for the first time! Joanna Kiryluk

  5. Transverse Single Spin Asymmetries – Preliminary Results Yellow Beam Blue Beam BBC East BBC West e (BBC) e (BBC) Ratio:e (BBC East)/e (CNI) consistent with e (BBC West)/e (CNI) We get: AN(BBC)=0.0066(8) Stat. error only! using: AN(CNI) = 0.0118 (10) from CNI online analysis Left-RightBBC asymmetry ( Vertical Pbeam component ) P~24% P~24% e (CNI) e (CNI) Yellow Beam Blue Beam BBC East BBC West e (BBC) • 5 s effect • may be a result of a broken snake? Consistent with zero - as expected for vertical polarization e (BBC) Top-BottomBBC asymmetry ( Radial Pbeam component ) Joanna Kiryluk e (CNI) e (CNI)

  6. Relative Luminosity - Motivation Double spin longitudinal asymmetry (e.g. p+p -> jet + X ) is defined as: P1,2 – beampolarization, from CNI polarimeter at RHIC N i where i=++, +- are spin dependent yields - relative luminosity of bunch crossings with different spin directions Assumption:ALL = 0.01 0.07 Relative luminosity - one of the dominant systematic errors in ALL measurement It must be known at (least) 10-3 level R=0.7 dALL / ALL Requirements for a luminosity process/detector: - high rates - small background - no (or small) spin dependence R=1.3 0.01 10-4 10-3

  7. Relative Luminosity - Measurement Yellow Blue STAR BBC Coinc. Rate Beam Crossing Number - RHIC filled with 55 - transversly polarized - proton bunches, - spin orientation related to the bunch crossing number 1-120, polarization pattern at STAR: Spin Up Spin Down Unpolarized Relative Luminosity abort gaps (beam-gas background) and time dependent! Run 4150010 1.0 BBC E.W coincidence counts Blue Yellow 05/16/03 05/30/03 bunch crossing# Time [Run Number] • integrated luminosity (number of BBC E.W counts ) recorded every 5 minutes - scaler board system • relative luminosities calculated for each STAR run, which typically lasts from a few minutes to ~ hour • statistical uncertainty d Rstat~ 10-4 – 10-3 Joanna Kiryluk

  8. Relative Luminosity – Systematics Beam-Gas Background Contribution Yellow beam-gas bg Blue beam-gas bg Bg/2 [%] 0.2 Run# Contribution to systematic uncertainty on R d R(sys) ~ 0.004 x 0.2 ~ 8 x 10-4 - must correct for background Joanna Kiryluk

  9. Summary • Single transverse spin asymmetry measured with the Beam Beam Counters in 2003 were found to be AN(BBC)=0.0066(8) using AN(CNI)=0.0118(10) from CNI online analysis. Systematic studies in progress. • The BBC was used to tune spin rotators needed to get longitudinally polarized beams at STAR IP and to monitor on-line transverse and radial beam polarization components. They are found to be small: Prad(vert) < 3%. • 3. The BBC in STAR is a good luminosity monitoring detector. The relative luminosity is known at the level of ~ 3 x10-3 • - statistical uncertainty: 10-4 –10 -3 • - (conservative) systematic uncertainty (BBC and ZDC comparison) ~ 3 x 10-3 • This needs further studies (background contribution) Joanna Kiryluk

  10. 2003 Detector Configuration STAR EMC (Half) Barrel EMC Full Barrel 2005 Full EndCap 2004 TPC BBC East BBC West EndCap EMC (1/3)

  11. Simulation based on Pythia • Use Fast TPC and EMC Simulators • EMC+TPC Jets Reconstructed using Cone Algorithm • Includes Jet-Patch Trigger ( ET > 5) covering the Full Half Barrel Calorimeter • ALL includes all jet processes (not a direct measure of delta G) Leading Jet Asymmetries are Sensitive to Gluon Max Allowed Gluon Polarization Best Fit to DIS Data Simulations by Les Bland

  12. pp Longitudinal Data Set

  13. jet parton proton proton Jet Finder (Mike Miller/Thomas Henry) For this Analysis, Jets are defined as a grouping of one or more (charged) Tracks measured in the TPC and satisfying the following requirements… • Using an Iterative, Midpoint, Cone Algorithm • Cone Angle = 0.7 in eta-phi • Seed Energy = 0.5 GeV • pT Track > 0.1 GeV • Track Range = +/- 1.6 • pT Jet > 5 GeV • Z = +/- 75 cm

  14. Eta Distribution TPC Jet Eta Phi Distribution TPC Jet Phi TPC Jet Raw Yield BEMC Preliminary Trigger Mask 32 PMTs Crate Failures • Goal: Measured ET --> Parton ET TPC Jet Characteristics – EMC Trigger Ratio of EMC to Charged Et • Select 0.2 < eta < 0.8 for Analysis Total TPC Tracks EMC points • Strong Trigger Bias at low ET

  15. Longitudinal Spin Asymmetries momentum spin Does Not Violate Parity Violates Parity REQUIRES luminosity ratios to be measured much more accurately than desired asymmetry

  16. TPC-Jet, Single-Spin Asymmetries Blue Beam Run (time) Yellow Beam Parity-Violating Asymmetries are Consistent with Zero Dylan Thein

  17. 2003 Outlook

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