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Analyzing Power for Forward Jet Production in Polarized Proton Collisions at √ s = 500 GeV

Analyzing Power for Forward Jet Production in Polarized Proton Collisions at √ s = 500 GeV. Chris Perkins UC Berkeley/Space Sciences Laboratory Stony Brook University. For The A N DY Collaboration. DNP 2012. 10 / 26 /2012. Motivation to Measure Jet A N. s=200 GeV. from p  + p  p+ X.

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Analyzing Power for Forward Jet Production in Polarized Proton Collisions at √ s = 500 GeV

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  1. Analyzing Power for Forward Jet Production in Polarized Proton Collisions at √s = 500 GeV Chris Perkins UC Berkeley/Space Sciences Laboratory Stony Brook University For The ANDY Collaboration DNP 2012 10/26/2012

  2. Motivation to Measure Jet AN s=200 GeV from p+pp+X “new”Sivers function “old”Sivers function STAR arXiv:1103.1591 Left Right Expectations for Jet AN: Theory expectation (for Pions): Small asymmetries at high energies (Kane, Pumplin, Repko, PRL 41 (1978) 1689) √s=200 GeV Experiment (for Pions): E704 √s=20 GeV p+ p0 p- pjT(GeV) arXiv:1011.2692 √s = 500 GeV jets have 2.5x larger pT at the same xF relative to these predictions. Phys. Lett. B 261 (1991) 201 Phys. Lett. B 264 (1991) 462 PRL 101 (2008) 222001 Jets integrate over p+, p-, and p0; “Mirror” AN for p+ and p- leads to cancellations for jet AN Chris Perkins

  3. ANDY Experimental Setup and Data Sample Run 2011 Setup : Run 2012 Setup : HCal Left/Right modules used in Run-11 were modified into an annular 20x12 detector with a 2x2 hole for the beam pipe Run 2012 Data : Run 2011 Data : √s = 510 GeV 2.5 pb-1 Integrated Luminosity 55% Average Beam Polarization √s = 500 GeV 6.5 pb-1 Integrated Luminosity 52% Average Beam Polarization ECal was put on Thomson rails for 2012 and can be moved out of the way for HCal only jets Collisions at IP2 (ANDY) had minimal impact on collisions at IP6 (STAR) and IP8 (PHENIX) Beam-Beam Counter (BBC) for minimum-bias trigger and luminosity measurement (from PHOBOS) [NIM A474 (2001) 38] Zero-Degree Calorimeter (ZDC) and Shower Maximum Detector (ZDC-SMD) for luminosity measurement and local polarimetry (Not Shown) Hadron Calorimeter (HCal) L/R symmetric modules of 9x12 lead-scintillating fiber cells (10cm)2x 117 cm (from AGS-E864) 7 Hadronic Interaction Lengths (sees π+,π-, π0) [NIM 406 (1998) 227] Small Electromagnetic Calorimeter (ECal) 7x7 matrices of lead glass cells (4cm)2x 40 cm (borrowedfrom BigCal at Jlab) Preshower Detector two planes, 2.5 & 10 cm Chris Perkins

  4. Run 2011 ANDY Setup Trigger/DAQ electronics Left/right symmetric HCal Left/right symmetric ECal Blue-facing BBC Left/right symmetric preshower Beryllium vacuum pipe Chris Perkins

  5. Jet Reconstruction – Cone Jet Finder Trigger on HCal masked ADC Sum in L/R Modules Events look “Jetty” as expected • Cone Jet Finder Procedure : • High Tower in HCal masked region is taken as a seed • Seed must be in triggering region • Sum energy in a cone with radius = 0.7 in η-Φ space around the high tower. (For ETower > 0.25 GeV) • Compute energy-weighted averge <η>,<Φ> • Iterate until convergence: • Sum energy in cone of radius R about <ηN>,<ΦN> • Compute energy-weighted average <ηN+1>,<ΦN+1> • Impose acceptance cuts to accept/reject jet: |ηJ – 3.25| < 0.25 |ΦJ – ΦOff| < 0.50 where ΦOff= 0 for HCL ΦOff = π for HCR • Energy Cut : Ejet > 30 GeV Chris Perkins

  6. Jet Reconstruction – Anti-kT Jet Finder Trigger on HCal masked ADC Sum in L/R Modules arxiv : 0802.1189 arxiv : 1209.1785 Anti-kT algorithm splits some Cone jets but overall, jets are similar to Cone Algorithm • Anti-kTJet Finder Procedure : • Iteratively merge pairs of clusters until clusters cease to satisfy distance criteria • No Seed • Towers can be outside trigger region • Distance Criteria (clusters j,k) : • djk = min(k-2Tj,k-2Tk)(R2jk/R2) • R2jk = (ηj – ηk)2 + (Φj – Φk)2 • If djk < k-2Tj then merge clusters j,k • Use cone with radius = 0.7 in η-Φ space but cluster towers can fall outside of cone • Impose acceptance cuts to accept/reject jet: |ηJ – 3.25| < 0.25 |ΦJ – ΦOff| < 0.50 where ΦOff= 0 for HCL ΦOff= π for HCR • Energy Cut : Ejet > 30 GeV • Algorithm : Chris Perkins

  7. Jet Definitions and Correlations Cone Jet Finder p, K… q, g Anti-kTJet Finder PYTHIA/GEANT Simulations show correlation between parton and reconstructed tower jets. (Both direction and energy) p p Correlation between particle jet energy and tower jet energy Correlations in h and j between reconstructed tower-jet and parton Chris Perkins

  8. Jet Kinematics and Shape Cone Jet Finder Anti-kT Jet Finder Jet pT and xF are calculated ignoring mass xF pT xF pT Jet Shape: Distribution of fraction of energy in the jet as a function of distance in η-Φ space from the jet center. Energy Fraction in Jet Energy Fraction in Jet R R Good agreement between data and simulations above trigger threshold for both algorithms Chris Perkins

  9. Trigger Bias for Forward Jets ECal Trigger Threshold ~ 22 GeV HCal Trigger Threshold ~ 35 GeV 30 < Ejet< 50 GeV 30 < Ejet< 50 GeV 50 < Ejet< 70 GeV 50 < Ejet< 70 GeV 70 < Ejet< 90 GeV 70 < Ejet< 90 GeV Tower Multiplicity Tower Multiplicity • ECal trigger biases jets, and the bias extends well beyond the trigger threshold • The trigger bias imposed by ECal likely prefers jets that fragment to a hard neutral pion Chris Perkins

  10. HCal Triggered Forward Jet AN Cone Jet Finder Anti-kT Jet Finder Jet AN is small (~10-3) and positive (up to ~6σ) for xF > 0 xF > 0 Jet AN is similar between the two jet algorithms Jet AN is close to zero for xF < 0 xF < 0 Fill dependence is consistent with statistics for both xF> 0 and xF < 0 Chris Perkins

  11. Systematic Uncertainty Studies • Bunch Shuffling : • Check that spin asymmetry (εphys) depends on actual polarization patterns. • For unpolarized collisions εphys must be zero, unless there is some systematic effect. Randomly reverse spin direction for half of the filled bunch crossings Only use distinct patterns with small effective polarization Mean values of distributions provides one estimate of systematics Further studies of systematic uncertainties are in progress (For uncertainty band on AN) • RMS of distributions compatible with statistical errors • Mean values are consistent with zero • Statistical Uncertainties are larger than systematic errors Chris Perkins

  12. Conclusions and Outlook • Measurements of full jets (HCal triggered) and ECal triggered jets have been made. • Trigger on electromagnetic energy biases jets • First measurements of the jet analyzing power show that forward jets have a positive AN that is small. • Conclusions are robust for multiple jet algorithms. • Systematic uncertainties are smaller than statistical uncertainties • Further studies of systematic uncertainties are in progress. • Hadronic final states are complicated and hard to describe. • Drell-Yan production is believed to be best understood by theory for transverse momentum-dependent effects, and there is a fundamental prediction about sign change to test by experiment. Chris Perkins

  13. Backup Slides Chris Perkins

  14. Calibration - ECal p+p, √s=510 GeV • Calibration based on p0 gg reconstruction – iterative procedure to scale the gain • to put the peak at the known • p0 mass • Event selection: • Nγ ≥ 2; • 15 GeV < Eγγ< 40 GeV; • zγγ < 0.8; • fiducialvolume cut 1/2 cell. Clear p0 signal with the peak at the right place; cell-by-cell calibration of the matrices is known at the level of ~2%. Di-photon invariant mass distribution in ECal modules

  15. Calibration - HCal • Relative calibration of HCal cells by cosmic ray muons • Absolute energy scale is set by: • slope matching of energy distributions from minimum-bias data and simulation; • 2) reconstruction of p0gg from • HCalclusters • Cuts applied to select “electromagnetic” clusters: • (1) 1-tower clusters; (2) Ecl > 1.8 GeV; • (3) Epair > 5 GeV; (4) zpair< 0.5; • (5) |x|>50 cm to avoid ECal shadow • Corrections to HCal calibration for hadron showers still need to be • evaluated (expected ~20% from • simulations) • Neutral pions set the energy scale for the jets Cluster pair mass distributions in HCalmodules from minimum-bias run-11 data and simulations (absolute normalization)

  16. Tower Multiplicity Cone Jet Finder Anti-kT Jet Finder Chris Perkins

  17. Fill Dependence of Jet AN Cone Jet Finder xF > 0 xF < 0 Fill dependence is consistent with statistics Chris Perkins

  18. ECal Triggered Jet Shape HCal Triggered ECal Triggered Distribution of fraction of energy in the jet as a function of distance in eta-phi space from the jet center (jet shape) Chris Perkins

  19. ECal Triggered Forward Jet AN ECal-biased jet AN at xF>0is positive, AN at xF<0 is generally consistent with zero Chris Perkins

  20. HCal acceptance in (h,j)-space

  21. Letter of Intent submitted 24 May 2010: http://www.bnl.gov/npp/docs/pac0610/Crawford_LoI.100524.v1.pdf PAC presentation:http://www.bnl.gov/npp/docs/pac0610/aschenauer_DY-collider_june10.pdf Proposal to 2011 PAC: http://www.bnl.gov/npp/docs/pac0611/DY_pro_110516_final.2.pdf 2011 PAC recommendations: http://www.bnl.gov/npp/docs/pac0610/Final recommendations.pdf Proposal for funding review 30 March 2012: http://hena.lbl.gov/IP2/Business/review/0-proposal_120229.pdf Review report 10 May 2012

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