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Polarisation@RHIC and the “Spin” Structure of the Proton

Polarisation@RHIC and the “Spin” Structure of the Proton. E.C. Aschenauer. Content. 0 min. > 30 min. 25 min. t. pC Polarimeters : Operation in Run11/12 Preparation for Run 13+ Polarisation analysis Long term plans. Highlights from eRHIC Summary and Discussion.

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Polarisation@RHIC and the “Spin” Structure of the Proton

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  1. Polarisation@RHIC and the “Spin” Structure of the Proton E.C. Aschenauer

  2. Content 0 min > 30 min 25 min t • pCPolarimeters: • Operation in Run11/12 • Preparation for Run • 13+ • Polarisation analysis • Long term plans Highlights from eRHIC Summary and Discussion • RHIC Spin Program • What do we know today: • transverse spin phenomena • Future potentials: • understand AN • GPDs at RHIC • Beyond 2015 • RHIC Spin group • changes in the group • work on polarized pp/ep RHIC Polarimetry

  3. RHIC and Polarimetry Absolute Polarimeter (H jet) RHIC pC Polarimeters Siberian Snakes RHIC PHENIX (p) STAR (p) Siberian Snakes Spin Rotators Solenoid Snake LINAC BOOSTER Pol. Proton Source 500 mA, 400 ms AGS Warm Snake 200 MeV Polarimeter AC Dipole AGS pC CNI Polarimeter Cold Snake ANDY(p) Local Polarimeters STAR and PHENIX

  4. RHIC Polarimetry • Polarized hydrogen Jet Polarimeter (HJet) • Source of absolute polarization (normalization of other polarimeters) • Slow (low rates  needs looongtime to get precise measurements) • Proton-Carbon Polarimeter (pC) @ RHIC and AGS • Very fast  main polarization monitoring tool • Measures polarization profile (polarization is higher in beam center) and lifetime • Needs to be normalized to HJet • Local Polarimeters (in PHENIX and STAR experiments) • Defines spin direction in experimental area • Needs to be normalized to HJet All of these systems are necessary for the proton beam polarization measurements and monitoring

  5. RHIC Jet Results-Run12 Beam Polarisation at 250 GeV Analysis: A. Dion Analyzing Power 24 GeV Beam Polarisation at 100 GeV • Measured beam polarization at injection • Run-11 and Run-12: • Run-12 Yellow Beam: 0.63 +- 0.044 • have determined AN for pC in one year • with one setup Summary: extremely stable operation through the run

  6. Operation during RUN 11 and 12 Run 2009 • Rate effects: • Test pulse applied to all preamps ~500 Hz • Monitor pulse rate, amplitude for rate effects: Run 2011 total pC rate in Si for 72 ch test pulse rate ~ 5% rate loss ~ 40% rate loss test pulse amplitude NO amplitude loss amplitude loss • Saw significant rate effects during Run 9 250 GeV running • mitigation: • replaced charge sensitive pre-amps by current sensitive ones  solved the problem

  7. Rate corrections in the AGS CNI polarimeter (Run12) Analysis: Andrei Poblaguev In the 90 degree detectors the rate is strip dependent. It may be employed for experimental determination of the parameter k Rate dependence of signal detection efficiency (due to pileup) (r) = e-kr ≈ 1-kr results in systematic error of polarization measurements Pmeas. ≈ Ptrue × (1-kr) In AGS r ≈ 0.1-0.15 (Run12) Naive estimate: k ≈ 0.75 45U 90U 90D 45D Horizontal Polarization Profile Polarization in RHIC reference runs

  8. Operation during RUN 11 and 12 ~25nm ~7-10mm Analysis: W. Schmidke hard to remove this systematic contribution  need different target technology changed target shows clearly normalization per target needed ✔ • Saw significant rate effects during Run 9 250 GeV running • mitigation: • replaced charge sensitive pre-amps by current sensitive ones • solved the problem • The stable performance of pC allowed to study the non-statistical behaviour of B1/B2 and Y1/Y2 • Culprit: the carbon fiber targets • can move in their holding bracket • fiber can be twisted • measured C kin. energy does not correspond to the one during scattering Tdet < Tscat assuming wrong AN • mitigation: QA  stringent control of target width

  9. Operation during RUN 11 and 12 good channel bad channel • Run-12: During 100 GeV running problems with RF induced noise • mitigation during the run: • Stochastic cooling pickup: terminate one cable • shield pre-amp boxes (Al-wrapping) • install different RF screens in front of SI-detectors • setup test bench using old scattering chamber • develop automatic analysis procedure to cut “noisy” channels • mitigation during shutdown: • improve grounding (MUX, terminate unused channels, ….) • redesign pre-amp boxes to shield from RF • Remaining issue: • targets had a incredible death rate (installed twice new full set during run) • Investigate cause  heating through beam  full RF simulation of chamber • Possible solutions • different technologies • thicker targets • possible redesign of target holder

  10. Results from offline Analysis • Beam polarisation decays over the fill • polarisation lifetime similar for 100 and 250 GeV • basically constant over the years 250GeV Analysis: Dima Smirnov • Developed a “offline” online analysis for fast feedback • https://wiki.bnl.gov/rhicspin/Results • Determined the pC analyzing power at 24, 100 and 250 GeV • calibration pC to Jet: beam energy independent

  11. RHIC pC Results: Polarization Profile If polarization changes across the beam, the average polarization seen by Polarimeters and Experiments (in beam collision) is different H-Jet pC Collider Experiments ~1 mm 6-7 mm x=x0 P1,2(x,y) – polarization profile, I1,2(x,y) – intensity profile, for beam #1 and #2

  12. Correlation R-Slope and P-Decay 2009: 100 GeV 2012: 100 GeV 2012: 250 GeV ~4-10%/h R=0.04 ~2-15%/h R=0.07 ~3-5%/h R=0.25 Conclusion: Polarisation lifetime in a fill is strongly correlated to growth in R Important to correct for final polarisation numbers for experiments

  13. 2012 RHIC pC Results: Polarisation Profile 0.077+/-0.009 Injection Same pattern in Run-11 no difference between x & y profile see lifetime for R over the fill • Future Improvements: • pJet and pC: • move to commercial VME based readout electronics • tested 16ch 250 MHz fADC from Jlab  looked perfect • pC: • main theme for future work improve stability • better targets: movement and thickness stability • might be forced to change technology • still would like to move to commercial Si detectors • better E-resolution, cheaper, off the shelf • but saw issues with response from Hamatsu ones • pJet: • preventative maintenance • main goal improve statistical accuracy of measurement • new Si detectors (500 mm thick)  higher t • test detectors from Charles University • requires also new pre-amp & new ceramics • Longterm: unpolarised jet • need to carefully study the trade between • statistical accuracy and systematic uncertainties 100 GeV • Polarisation lifetime has • consequencesfor physics analysis • different physics triggers mix • over fill see different <P> • new information for experiments • correct each measurement Pi with Ri • fit P(t)=P0exp(-t/tp) • Provide experiments Po(SSA, DSA) • and t as well as <P> • basically ready for run-9,11 and 12 • http://www.phy.bnl.gov/cnipol/fills/ 0.11+/-0.009 250 GeV 0.25+/-0.011


  15. News from the Group Current size of the group: 4+1 PostDocs (2 DOE & 1 Director funds & 1 LDRD & 1 EIC Det. R&D) 4.5 physicists (3 tenured and 1.5 continuing appointment (0.5 Dr. W. Guryn) 2.5 tenure track scientist (0.5 Dr. M. Stratmann) + 1 PhD student from China + 3 undergrads from SBU • Changes in group personnel • Dr. A. Gordon (tenure track) left the group for a job at RENTEC Dec 2012 • Dr. Oleg Eyser from UC-Riverside (PHENIX) joined the group as tenure track in November 2011 • Spin PWG convenor at PHENIX • Dr. Alan Dion (H-Jet, STAR) left the group for a permanent position at SBU end of May 2012 • currently due to a funding not rehiring • Dr. B. Di Ruzza joined the group as PostDoc to work on the EIC Si-Pixel R&D based on MAPS (funded by an LDRD) • Hire on more postdoc through EIC Detector R&D funds is basically finalized, offer hopefully goes out this week • dedicated to detector and IR simulations and Detector R&D (tracking + PID)

  16. The RHIC SPIN Group STAR PHENIX ANDY Polarimetry eRHIC/EIC • Elke-C. Aschenauer • Alan Dion < May 2012 • Oleg Eyser > now • William B. Schmidke • Dimitri Smirnov • A. Kirleis (undergrad) • Hardware responsibilities: • pCpolarimeters, • H-Jet detectors • Improvements of the • Polarimeters • DAQ • Physics goals: • Offline analysis of • polarimeter data • final polarization • for experiments • Fast feedback to CAD to • improve polarization • in RHIC Les Bland Akio Ogawa Remaining Physics goals: analyze data from run-11 Alexander Bazilevsky Oleg Eyser Hardware responsibilities A. Bazilevsky: Trigger coordinator Run11&12 ePHENIX sPHENIX forward upgrade Physics goals: DG & cross section via p0, AL W-physics Drell-Yan in pp transverse physics observables O. Eyser Spin PWG convener Elke-C. Aschenauer Thomas P Burton Salvatore Fazio Benedetto di Ruzzo + ! postdoc Liang Zheng (PhD) + 2 undergrads Responsibilities: Detector Design & IR integration hadronpolarimetry “Roman Pots” Software tools EIC-White-Paper Physics goals: ep: Spin, TMDs, GPDs eA: determine initial andfinal state effects/conditions ECA Co-convener of the BNL EIC-TF Les Bland Akio Ogawa WlodzimierzGuryn Thomas P Burton Salvatore Fazio William B. Schmidke E.-C. Aschenauer Dimitri Smirnov Since 2011 E.-C. Aschenauer Hardware responsibilities BBC, FMS-Calib. FGT Roman Pots of pp2pp Forward Upgrade Physics goals: Forward Physics in dAu gluon saturation  CGC Single Spin Asymmetries AN  Jet, W, Di-jet GPDs pp2pp: diffractive physics & glueball searches • Postdocs: funded by LDRDs and Director’s Funds • Postdocs: funded by DOE ME

  17. Group Achievements • Papers: • STAR: • 1 paper published + 3 submitted • 2 with contributions from the RHIC spin group • PheniX: • 1 published + 1 submitted • 1 with contributions from the RHIC Spin Group • several Papers not on RHIC from earlier involvements • HERMES, Zeus, D0, CDF, …. • ~40 Seminars and Presentations on Conferences and Workshops


  19. Collected Luminosity with longitudinal Polarization

  20. Dq: W Production Basics u d Since W is maximally parity violating  W’s couple only to one partonhelicity large Δuand Δdresult inlarge asymmetries. No Fragmentation ! high Q2 Similar expression for W- to get Δ and Δd…

  21. The polarisation of the Sea Quarks Current Results:

  22. What Can Be Expected With a 15 week run in 2013 equally fantastic as the one in 2012, we can come close to the required ∫ luminosity Δχ2 = 2% uncertainty bands of DSSV analysis • allows for flavor separation for 0.07 < x < 0.04 All W-related upgrades will be or have been already installed for Run 13. PHENIX: RPC and m-Trigger have been completed before RUN 12 STAR:FGT will be fully installed Δχ2 = 2% uncertainty bands with RHIC data

  23. DG: what Do We KNOW World DIS Data & RHIC till 2006 • First time significant non zero Dg(x) 0.01<x<0.2 • What now: • try to go to terra incognita • lower x • the ultimate answer only from eRHIC terra incognita DIS RHIC consistent with p0 data

  24. DG what will come uncertainties decrease by ~20% if Run 12+13 are combined After run-14 we will have a nice set of high statistics data to determine Dg(x) for x > 0.01 and started measurements to explore lower x x>0.001 uncertainties decrease by ~1.4 if Run 12+13 are combined of course many other channels both from PHENIX and STAR but with less statistical power

  25. Collected Luminosity with transverse Polarization

  26. Transverse Polarization Effects @ RHIC Left Right midrapidity: maybe gluon Sivers???? Big single spin asymmetries in pp !! Naive pQCD (in a collinear picture) predicts AN ~ asmq/sqrt(s) ~ 0 What is the underlying process? Sivers / Twist-3 or Collins or .. no answer yet Do they survive at high √s ? ✔ Is pt dependence as expected from p-QCD? NO

  27. Transversely Polarized Proton MC • Developed by Tom Burton also for eRHIC • Sivers and Collins asymmetries included • IFF and DY/ W AN need to be still included • Details: http://drupal.star.bnl.gov/STAR/system/files/burtonAnalysisMeeting20110418.pdf Collins with positivity bounds as input Sivers Mechanism • Fast smearing generator tool to smear generator particle responses in p and energy and to include PID responses, “detectors” can be flexible defined in the acceptance

  28. What else do we know • Collins / Transversity: • conserve universality in hadron hadron interactions • FFunf = - FFfavand du ~ -2dd • evolve ala DGLAB, but soft because no gluon contribution (i.e. non-singlet) • Sivers, Boer Mulders, …. • do not conserve universality in hadron hadron interactions • kt evolution  can be strong • till now predictions did not account for evolution • FF should behave as DSS, but with ktdependence unknown till today • u and d Siversfct. opposite sign d >~ u • Sivers and twist-3 are correlated • global fits find sign mismatch, possible explanations, like node in kt or x don’t work

  29. AN: How to get to underlying Physics Transversity x Collins SIVERS • AN for jets in mid to forward • rapidity • AN for direct photons in • mid to forward rapidity • AN for heavy flavour gluon • p+/-p0 azimuthal distribution in jets • mid to forward rapidity • Interference fragmentation function •  mid to forward rapidity AN for p0 and hin FMS with increased pt coverage STAR: Combine 2011 transverse 500 GeV data and 2012 transverse 200 GeV data Powerful dataset to attack AN mystery and it will help us to optimize forward upgrades planned by PHENIX and STAR

  30. STAR: Mid-rapidity Surprise IFF Asymmetry Exploratory Analysis from 200 GeV Transverse Running in 2006 show first clear signal of transversity in pp collisions at RHIC! Collins IFF

  31. The famous sign change of the Siversfct. Intermediate QT Q>>QT/pT>>LQCD Transverse momentum dependent Q>>QT>=LQCD Q>>pT Collinear/ twist-3 Q,QT>>LQCD pT~Q Efremov, Teryaev; Qiu, Sterman Siversfct. critical test for our understanding of TMD’s and TMD factorization QCD: DIS: attractive FSI Drell-Yan: repulsive ISI QT/PT LQCD Q QT/PT << << SiversDIS = -SiversDY/ SiversW

  32. Background rejection • Electrons and positrons from hard QCD processes are uncorrelated • Opening angles are comparable to Drell Yan: detector acceptance • Lepton energies of Drell Yan decays are large • Energy cut removes QCD background at small minv • Large masses in QCDbackground favor mid-rapidity • Energy asymmetry hasnot been instrumented yet Study: O. Eyser

  33. Drell-Yan at forward rapidities • Parametrized fast MC for detectorsmearing • Drell Yan signal • 3 – 10 GeV/c2 • Energy cut • E1,2 > 2 GeV • Forward rapidities • Effectively no background left • Statistically limited • Drell Yanfor minv < 3 GeV/c2 not physical (PYTHIA settings)

  34. The polarized DY/W ANcHallenge Need to see how things develop ! If this strong evolution effect is really true ? • HP-13: Test unique QCD predictions for relations • between single-transverse spin phenomena in p-p scattering • and those observed in deep-inelastic lepton scattering. • Can we do it ? Yes we can ! • Many accessible observables Anjet, Ang with very clear predictions • basedon SIDIS measurements • AN(DY/W): Sign change and evolution are strong prediction of • “TMD-formalism” need to measure to see predictions are true • Caveat: kt evolution of TMDs • First results from evolution workshop at Jlab http://www.jlab.org/conferences/qcd2012/program.html

  35. THE RHIC SPIN Program > 2015 • going forward • map out transverse spin effects • potential to get the first glimpse of GPD E for gluons • low-x gluons

  36. From pp to gp/A • Get quasi-real photon from one proton • Ensure dominance of g from one identified proton • by selecting very small t1, while t2 of “typical hadronic • size” • small t1 large impact parameter b (UPC) • Final state lepton pair  timelikecompton scattering • timelikeCompton scattering: detailed access to GPDs • including Eq;gif have transv. target pol. • Challenging to suppress all backgrounds • Final state lepton pair not from g* but from J/ψ • Done already in AuAu • Estimates for J/ψ (hep-ph/0310223) • transverse target spin asymmetry  calculable with GPDs • information on helicity-flip distribution E for gluons • golden measurement for eRHIC Z2 A2 Gain in statistics doing polarized p↑A

  37. Forward Proton Tagging at STAR/RHIC at 55-58m at 15-17m J.H. Lee Study: JH Lee & W. Guryn • Roman Pot detectors to measure forward scattered protons in diffractive processes • Staged implementation to cover wide kinematic coverage • Phase I (Installed): for low-t coverage • Phase II (planned) : for higher-t coverage • 8(12) Roman Pots at ±15 and ±17m • 2π coverage in φ will be limited due to • machine constraint (incoming beam) • No special b* running needed any more •  250 GeV to 100 GeV • scale t-range by 0.16

  38. STAR Forward Instrumentation Possibilities FMS >2016 ~ 6 GEM disks Tracking: 2.5 < η < 4 HCal SPACAL Preshower 1/2” Pb radiator Shower “max” Threshold Cerenkov p+/- ID proton nucleus

  39. The sPHENIX forward Upgrade

  40. What pHe3 can teach us Therefore combining pp and pHe3 data will allow a full quark flavor separation u, d, ubar, dbar • Two physics trusts for a polarized pHe3 program: • Measuring the sea quark helicity distributions through W-production • Access to Ddbar • Caveat maximum beam energy for He-3: 166 GeV • Need increased luminosity to compensate for lower W-cross section • Measuring single spin asymmetries AN for pion production and Drell-Yan • expectations for AN (pions) • similar effect for π± (π0 unchanged) 3He: helpful input for understanding of transverse spin phenomena Critical to tag spectator protons from 3He with roman pots • Polarized He-3 is an effective neutron target  d-quark target • Polarized protons are an effective u-quark target

  41. The same RP configuration with the current RHIC optics (at z ~ 15m between DX-D0) Acceptance ~ 98% Spectator proton from 3He with the current RHIC optics • Momentum smearing mainly due to Fermi motion + Lorentz boost • Angle <~3mrad (>99.9%) Angle [rad] Study: JH Lee generated Passed DX aperture Accepted in RP


  43. the path to imaging quarks and gluons compelling questions transverse plane • how are quarks and gluons spatially distributed • how do they move in the transverse plane • do they orbit and do we have access to spin-orbit correlations unpolarizedpolarized • PDFs do not resolve transverse momenta or positions in the nucleon • fast moving nucleon turns into a `pizza’ but transverse size remains about 1 fm How areGPDs characterized? quantum numbers of final state select different GPD conserve nucleon helicity flip nucleon helicity not accessible in DIS vector mesons pseudo-scaler mesons DVCS

  44. DVCS at eRHIC ~ e g H, H, E, E (x,ξ,t) gL* (Q2) x+ξ x-ξ ~ e’ Fourier Transform DVCS data at end of HERA D. Mueller, K. Kumericki S. Fazio, M. Diehl and ECA t p’ p needs 100 fb-1 large t small t needs 10 fb-1 + Roman Pots DVCS: Golden channel theoretically clean wide range of observables (s, AUT, ALU, AUL, AC) to disentangle different GPDs

  45. What will we learn about 2d+1 structure of the proton GPD H and E as function of t, x and Q2 GPD H and E 1d+1 Plots from D. Mueller GPD H and E 2d structure for quarks • A global fit over all mock data was done, based on the GPDs-based model: • [K. Kumerički, D Müller, K. Passek-Kumerički 2007] • Known values q(x), g(x) are assumed for Hq, Hg (at =0, t=0 forward limits Eq, Egare unknown) • Excellent reconstruction of Hsea, Hseaand good reconstruction of Hg(from dσ/dt) shift due to GPD E

  46. impact of EIC data on helicity PDFs Study: M. Stratmann, R. Sassot, ECA • DIS scaling violations mainly determine • Δg at small x • SIDIS data provide detailed flavor separation of quark sea • can be pushed to x=10-4 with 20 x 250 GeV data

  47. impact of EIC data on helicity PDFs DIS scaling violations mainly determine Δg at small x ( SIDIS scaling violations add to this) in addition, SIDIS data provide detailed flavor separation of quark sea • includes only “stage-1 data” • [even then Q2min can be 2-3 GeV2] • can be pushed to x=10-4 with • 20 x 250 GeV data • [still one can play with Q2min ] • uncertainties determined with • both Lagrange mult. & Hessian “issues”: • (SI)DIS @ EIC limited by • systematic uncertainties • need to control rel. lumi, polarimetry, • detector performance, … very well • QED radiative corrections • need to “unfold” true x,Q2 • well known problem (HERA) • BNL-LDRD project to sharpen tools

  48. progress towards spin sum rule • combined correlated uncertainties for ΔΣ and Δg “Helicity sum rule” ✔ gluon spin • results obtained with two • Lagrange multipliers • Hessian method consistent access through Twist-3 GPDs more theoretical work needed current data ✔ angular momentum total quark spin “X. Jisum rule” • similar improvement • for 0.0001-1 moments • needs 20 x 250 GeV data ✔ difficult, but should be possible in GPD models w/ EIC data • can expect approx. 5-10% • uncertainties on ΔΣ and Δg • but need to control systematics

  49. SummarY DG SqLq Lg SqDq SqDq Lg SqLq dq DG dq HP-8 2013 Where do we stand to unravel the internal structure of protons HP-13 2015 HP-12 2013 RHIC spin active program with many new developments in theory and experiments! On track to achieve milestones

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