Overview of A N DY L.C.Bland Brookhaven National Laboratory BNL Review of the A N DY Proposal 30 March 2012

3/30/2012AnDY Overview2 Where is the spin of the proton? Proton characterized by basic properties of mass, spin, size, … Global fits to Parton Distribution Functions find that ~50% of the momentum of the proton is carried by gluons Polarized deep inelastic scattering finds that quarks account for only ~1/3 of the proton spin:  =0.33  0.03 (stat)  0.05 (syst) d’Hose (INT, 2012) RHIC spin addresses this question Overall, RHIC is addressing the role of color e.g. INT Workshop INT-12-49W Orbital Angular Momentum in QCD 6-17 February 2012

3/30/2012AnDY Overview3 arXiv: RHIC Spin (2006) Highlights New insights from RHIC after 30 years of polarized deep inelastic scattering Where is the spin of the proton? Gluon polarization is not large… If not from gluons, then is the spin from orbital motion? STAR PRL 101 (2008)

3/30/2012AnDY Overview4 Why polarized Drell Yan? Best answer: RBRC workshop in May, 2011 had 31 talks and ~80 participants from all over the world due to the intense interest in measuring transverse SSA, and other aspects, for Drell-Yan production John Collins, in his Workshop Summary, concluded with these words…

3/30/2012AnDY Overview5 Simple QED example: DIS: attractive Drell-Yan: repulsive Same in QCD: As a result: Attractive vs Repulsive Sivers Effects Unique Prediction of Gauge Theory ! Transverse Spin Drell-Yan Physics at RHIC (2007)

3/30/2012AnDY Overview6 Why A N DY?

3/30/2012AnDY Overview7 Modeling an Experiment Run-11 goals… What is the impact of a third IR on polarized proton operations at RHIC? Can the hadron calorimeter planned for ANDY be robustly calibrated?

3/30/2012AnDY Overview8 Run-11 A N DY Left/right symmetric HCal Left/right symmetric ECal Left/right symmetric preshower Trigger/DAQ electronics Blue-facing BBC Beryllium vacuum pipe

3/30/2012AnDY Overview9 Impact of Collisions at IP2 The anatomy of initiating collisions at IP2 Early after a RHIC store is set up, beams are colliding at IP6 (STAR) and IP8 (PHENIX). Beams are transversely separated at IP2 (A N DY). The arrow indicates when collisions begin at IP2 After the beam intensity decays to a threshold (here, 1.3  ions/bunch), collisions begin at IP2. There is loss of beam in the Yellow ring. The beam loss is monitored. The spikes in the Blue ring are due to insertions of carbon ribbons for measuring the beam polarization. Beam- beam tune shift causes loss of ions in Yellow when collisions begin at IP2. This loss typically decays with time, as shown. Luminosity at IP6 (STAR) and IP8 (PHENIX) is mostly constant when collisions are initiated at IP2 (A N DY).

3/30/2012AnDY Overview10 Impact of IP2 Collisions IP2 collisions have begun <3 hours after physics ON with minimal impact on IP6,IP8. Adequate luminosity for A N DY (10 pb -1 /week for  s=500 GeV polarized proton collisions) is projected for subsequent runs. Minimal impact on STAR,PHENIX Fri. 8 April 1.50  /bunch

3/30/2012AnDY Overview11 HCal Calibration Reconstruction of    from HCal clusters sets the energy scale of the calorimeter The mass distribution from data is compared to reconstruction of PYTHIA/GEANT events, and agrees well in shape and magnitude

3/30/2012AnDY Overview12 Shower maximum detector 7x7 array of “Yerevan” lead glass from BigCal Towards Dileptons from Run-11 Run-11 configuration was supplemented by loan of 120 detectors from BigCal in October, A primary purpose was to establish color-trapping center development in glass at IP2. Transparency before/after run- 11 was the same to within 10% Readout triggered on ECal was a “test trigger” in run-11, but ECal clusters paired with “HCal-EM” clusters have mass extending to >4 GeV/c 2. Background dominantly from photon pairs

3/30/2012AnDY Overview13 Dileptons from Run 11 Data A N DY profiling methods were applied to a limited data sample (L int =0.5 / pb) of run-11 ECal triggered data. Dominant backgrounds are now from , and are suppressed by using MIP response of beam-beam counters to tag clusters. Individual detector    calibration for HCal was an essential step to reconstruct J/  Limited granularity of BBC and poor position resolution of HCal-EM cluster results in less photon suppression than expected for final A N DY apparatus (project ~100x better suppression) Hadron suppression is not yet required, but will be in going from dileptons to DY J/  e+e- peak has ~120 events with 5.4  statistical significance. PYTHIA with NRQCD expects 420 events in the run-11 acceptance, approximately consistent with observation after crude efficiency correction. From PYTHIA 6.425, DY with M>4 GeV/c 2 is 170x smaller in this acceptance. J/  is a window to heavy flavor via B  J/  K and  b  J/  p  that would help quantify intrinsic b from proton backgrounds to DY

3/30/2012AnDY Overview14 Dileptons from Run 11 Data versus Simulation Compare run-11 mass distribution to model used to make background estimates for DY Large-mass background found to be well-represented by fast-simulator model in both magnitude and shape

3/30/2012AnDY Overview15 A N DY Run-13 elements and their purpose ECal – primary detector for detecting dielectrons HCal – hadron rejection Preshower – hadron rejection and photon/electron discrimination Tracking – the value of accurate space points / deflections through magnet DY relative to reducible backgrounds DY relative to irreducible backgrounds

3/30/2012AnDY Overview16 Projected precision for proposed A N DY apparatus Goal of A N DY Project Measure the analyzing power for forward Drell-Yan production to test the predicted change in sign from semi-inclusive deep inelastic scattering to DY associated with the Sivers function GEANT model of proposed A N DY apparatus (run-13)

17 arXiv: Proposed A N DY ECal 1596-element TF1 lead-glass calorimeter borrowed from JLab, with return date of July, 2014 ECal dimensions are driven by optimizing the acceptance for forward DY production A N DY ECal has similar scope to earlier projects completed by the proponents Full GEANT response of ~18X 0 and ~1 hadronic interaction length glass can be parameterized for fast simulation of detector response

3/30/2012AnDY Overview18 ECal HCal Side View Top View Proposed A N DY HCal Primary purpose of A N DY HCal is to veto hadrons that deposit  E=fE in ECal, by observing (1-f)E in HCal Full GEANT simulations of ECal+HCal show 82% hadron rejection with 99% electron retention. Uses existing E864 detectors (117-cm long / 47x47 scintillating fiber matrix embedded into lead)  Proposed run-13 configuration requires borrowing 60 additional detectors from PHENIX

3/30/2012AnDY Overview19 A N DY Preshower HCal rejection of hadrons that deposit f>0.7 of their energy in ECal is not very effective A preshower+converter detector upstream of the ECal rejects 86% of hadrons while retaining 98% of the electrons and positrons First component of preshower (prior to converter) is needed for discrimination between photons and electrons. 98% of photons are vetoed here while retaining 98% of electrons Segmenation of proposed preshower minimizes multiple occupancy in a PS detector

3/30/2012AnDY Overview20 Tracking + Split-Dipole Prior experience with ECal shows (x,y) position localization to ~1/10 cell size, or ~4mm. A single tracking station provides space point of resolution better than 0.2mm  robust z vertex and robust ECal/PS association even without magnet Split-dipole magnet is planned for RHIC run 14. Radial deflections through split- dipole result in effective shift of z vertex from tracking, relative to true value, that depends on charge sign Charge sign discrimination can determine if hadronic backgrounds are suppressed

3/30/2012AnDY Overview21 Strategy for Estimates Experience with run-11 analysis, shows that full PYTHIA/GEANT required ~2.5 weeks to generate 0.5 pb -1 of QCD background simulation. We are exploring the possibility of using NSERC for GEANT simulations. Until then, use fast simulator, benchmarked to run-11 data Reducible backgrounds: QCD hadron + photons Irreducible backgrounds: heavy quarks

3/30/2012AnDY Overview22 Reducible Backgrounds

3/30/2012AnDY Overview23 Irreducible Backgrounds

3/30/2012AnDY Overview24 A N DY Projections Projected precision for proposed A N DY apparatus

3/30/2012AnDY Overview25 Outlook Low-x physics at RHIC There’s more to Drell Yan than just the sign change There’s more to forward physics than just DY From RHIC-DY to EIC