Transverse Spin and RHIC Probing Transverse Spin in p+p Collisions OUTLINE Features of RHIC for polarized p+p collisions Transverse single spin effects in p+p collisions at s=200 GeV Towards understanding forward p0 cross sections Plans for the future L.C. Bland Brookhaven National Laboratory Transverse Polarization in Hard Processes Como 7 September 2005

Developments for runs 2 (1/02), 3 (3/03  5/03) and 4 (4/04  5/03) Installed and commissioned during run 4 To be commissioned Installed/commissioned in run 5 Developments for runs 2 (1/02), 3 (3/03  5/03) and 4 (4/04  5/03) Helical dipole snake magnets CNI polarimeters in RHIC,AGS  fast feedback b*=1m operataion spin rotators  longitudinal polarization polarized atomic hydrogen jet target 7/29/2019 L.C.Bland, Como

RHIC Spin Physics Program Direct measurement of polarized gluon distribution using multiple probes Direct measurement of anti-quark polarization using parity violating production of W Transverse spin: Transversity & transverse spin effects: possible connections to orbital angular momentum? 7/29/2019 L.C.Bland, Como

Calendar Summary for RHICRun-5 p+p Run pp commissioning started on March 24, 2005 pp Physics running, for longitudinal polarization, started on April 19, 2005 410 GeV Collider dev. & data, was May 31st to June 3rd Transverse polarization was June 13th to June 16th Run ended on June 24, 2005 7/29/2019 L.C.Bland, Como

RHIC Run-5 Performance (nb-1) (nb-1) Total for run ~ 9.2 pb-1 delivered ~ 3.1 pb-1 smpled (nb-1) (nb-1) Delivered STAR 2005 Longitudinal Goal Sampled 7/29/2019 L.C.Bland, Como

PHENIX Detector Philosophy: 0 reconstruction and High rate capability & granularity Good mass resolution and particle ID 0 reconstruction and high pT photon trigger: EMCal: ||<0.38, = Granularity  = 0.010.01 Minimum Bias trigger and Relative Luminosity: Beam-Beam Counter (BBC): 3.0<||<3.9, =2 7/29/2019 L.C.Bland, Como

7/29/2019 L.C.Bland, Como

STAR detector layout TPC: -1.0 <  < 1.0 FTPC: 2.8 <  < 3.8 BBC : 2.2 <  < 5.0 EEMC:1 <  < 2 BEMC:0 <  < 1 FPD: || ~ 4.0 & ~3.7 7/29/2019 L.C.Bland, Como

First AN Measurement at STAR prototype FPD results STAR collaboration Phys. Rev. Lett. 92 (2004) 171801 Similar to result from E704 experiment (√s=20 GeV, 0.5 < pT < 2.0 GeV/c) Can be described by several models available as predictions: Sivers: spin and k correlation in parton distribution functions (initial state) Collins: spin and k correlation in fragmentation function (final state) Qiu and Sterman (initial state) / Koike (final state): twist-3 pQCD calculations, multi-parton correlations √s=200 GeV, <η> = 3.8 7/29/2019 L.C.Bland, Como

Why Consider Forward Physics at a Collider? Kinematics Deep inelastic scattering Hard scattering hadroproduction Can Bjorken x values be selected in hard scattering? Assume: Initial partons are collinear Partonic interaction is elastic  pT,1  pT,2  Studying pseudorapidity, h=-ln(tanq/2), dependence of particle production probes parton distributions at different Bjorken x values and involves different admixtures of gg, qg and qq’ subprocesses. 7/29/2019 L.C.Bland, Como

Simple Kinematic Limits Mid-rapidity particle detection: h10 and <h2>0  xq  xg  xT = 2 pT / s Large-rapidity particle detection: h1>>h2 xq  xT eh1  xF (Feynman x), and xg  xF e-(h1+h2) NLO pQCD (Vogelsang) 1.0 0.8 0.6 0.4 0.2 0.0 p+p  p0+X, s = 200 GeV, h=0 qq fraction qg gg 0 10 20 30 pT,p (GeV/c)  Large rapidity particle production and correlations involving large rapidity particle probes low-x parton distributions using valence quarks 7/29/2019 L.C.Bland, Como

Do they work for forward rapidity? How can one infer the dynamics of particle production? Particle production and correlations near h0 in p+p collisions at s = 200 GeV Inclusive p0 cross section Two particle correlations (h) STAR STAR, Phys. Rev. Lett. 90 (2003), nucl-ex/0210033 At √s = 200GeV and mid-rapidity, both NLO pQCD and PYTHIA explains p+p data well, down to pT~1GeV/c, consistent with partonic origin Do they work for forward rapidity? Phys. Rev. Lett. 91, 241803 (2003) hep-ex/0304038 7/29/2019 L.C.Bland, Como

Forward p0 production in hadron collider Ep p0 p d EN qq qp p Au xgp xqp qg EN (collinear approx.) Large rapidity p production (hp~4) probes asymmetric partonic collisions Mostly high-x valence quark + low-x gluon 0.3 < xq< 0.7 0.001< xg < 0.1 <z> nearly constant and high 0.7 ~ 0.8 Large-x quark polarization is known to be large from DIS Directly couple to gluons = A probe of low x gluons <z> <xq> <xg> NLO pQCD Jaeger,Stratmann,Vogelsang,Kretzer 7/29/2019 L.C.Bland, Como

xF and pT range of FPD data STAR xF and pT range of FPD data 7/29/2019 L.C.Bland, Como

ppp0X cross sections at 200 GeV The error bars are point-to-point systematic and statistical errors added in quadrature The inclusive differential cross section for p0 production is consistent with NLO pQCD calculations at 3.3 < η < 4.0 The data at low pT are more consistent with the Kretzer set of fragmentation functions, similar to what was observed by PHENIX for p0 production at midrapidity. D. Morozov (IHEP), XXXXth Rencontres de Moriond - QCD, March 12 - 19, 2005 NLO pQCD calculations by Vogelsang, et al. 7/29/2019 L.C.Bland, Como

STAR -FPD Preliminary Cross Sections Similar to ISR analysis J. Singh, et al Nucl. Phys. B140 (1978) 189. 7/29/2019 L.C.Bland, Como

PYTHIA: a guide to the physics Forward Inclusive  Cross-Section: Subprocesses involved: q+g g+g and q+g  q+g+g STAR FPD Soft processes PYTHIA prediction agrees well with the inclusive 0 cross section at 3-4 Dominant sources of large xF  production from: q + g  q + g (22)   + X q + g  q + g + g (23)   + X q g  q  g 7/29/2019 L.C.Bland, Como

Single Spin Asymmetry Definitions dσ↑(↓) – differential cross section of p0 then incoming proton has spin up(down) Two measurements: Single arm calorimeter: R – relative luminosity (by BBC) Pbeam – beam polarization Two arms (left-right) calorimeter: No relative luminosity needed π0, xF<0 π0, xF>0 Left Right p  p positive AN: more p0 going left to polarized beam 7/29/2019 L.C.Bland, Como

Run 3 Preliminary Result. -More Forward angles. -FPD Detectors. Caveats: -RHIC CNI Absolute polarization still preliminary. -Result Averaged over azimuthal acceptance of detectors. -Positive XF (small angle scattering of the polarized proton). Run 2 Published Result. Run 3 Preliminary Result. -More Forward angles. -FPD Detectors. - ~0.25 pb-1 with Pbeam~27% Run 3 Preliminary Backward Angle Data. -No significant Asymmetry seen. (Presented at Spin 2004: hep-ex/0502040) 7/29/2019 L.C.Bland, Como

New Physics at high gluon density Figure 3 Diagram showing the boundary between possible “phase” regions in the t=ln(1/x) vs ln Q2 plane . New Physics at high gluon density Shadowing. Gluons hiding behind other gluons. Modification of g(x) in nuclei. Modified distributions needed by codes that hope to calculate energy density after heavy ion collision. Saturation Physics. New phenomena associated with large gluon density. Coherent gluon contributions. Macroscopic gluon fields. Higher twist effects. “Color Glass Condensate” Edmond Iancu and Raju Venugopalan, review for Quark Gluon Plasma 3, R.C. Hwa and X.-N. Wang (eds.), World Scientific, 2003 [hep-ph/0303204]. 7/29/2019 L.C.Bland, Como

 Dependence of RdAu y=0 As y grows Kharzeev, Kovchegov, and Tuchin, Phys. Rev. D 68 , 094013 (2003) G. Rakness (Penn State/BNL), XXXXth Rencontres de Moriond - QCD, March 12 - 19, 2005 See also J. Jalilian-Marian, Nucl. Phys. A739, 319 (2004) From isospin considerations, p + p  h is expected to be suppressed relative to d + nucleon  h at large  [Guzey, Strikman and Vogelsang, Phys. Lett. B 603, 173 (2004)] Observe significant rapidity dependence similar to expectations from a “toy model” of RpA within the Color Glass Condensate framework. 7/29/2019 L.C.Bland, Como

Constraining the x-values probed in hadronic scattering Log10(xGluon) Gluon TPC Barrel EMC FTPC FPD For 22 processes Guzey, Strikman, and Vogelsang, Phys. Lett. B 603, 173 (2004). Log10(xGluon) Collinear partons: x+ = pT/s (e+h1 + e+h2) x = pT/s (eh1 + eh2) FPD: ||  4.0 TPC and Barrel EMC: || < 1.0 Endcap EMC: 1.0 <  < 2.0 FTPC: 2.8 <  < 3.8 CONCLUSION: Measure two particles in the final state to constrain the x-values probed 7/29/2019 L.C.Bland, Como

Back-to-back Azimuthal Correlations with large  Beam View Top View Fit LCP normalized distributions and with Gaussian+constant Trigger by forward   ] E > 25 GeV   4 ] Coicidence Probability [1/radian] Midrapidity h tracks in TPC -0.75 < < +0.75 Leading Charged Particle(LCP) pT > 0.5 GeV/c LCP S = Probability of “correlated” event under Gaussian B = Probability of “un-correlated” event under constant s = Width of Gaussian 7/29/2019 L.C.Bland, Como

Statistical errors only STAR PYTHIA (with detector effects) predicts “S” grows with <xF> and <pT,> “s” decrease with <xF> and <pT,> PYTHIA prediction agrees with p+p data Larger intrinsic kT required to fit data STAR Preliminary 25<E<35GeV 45<E<55GeV STAR Preliminary Statistical errors only 7/29/2019 L.C.Bland, Como

Plans for the Future 7/29/2019 L.C.Bland, Como

STAR Forward Meson Spectrometer NSF Major Research Initiative (MRI) Proposal submitted January 2005 [hep-ex/0502040] 7/29/2019 L.C.Bland, Como

STAR detector layout with FMS TPC: -1.0 <  < 1.0 FTPC: 2.8 <  < 3.8 BBC : 2.2 <  < 5.0 EEMC:1 <  < 2 BEMC:-1 <  < 1 FPD: || ~ 4.0 & ~3.7 7/29/2019 L.C.Bland, Como

Three Highlighted Objectives In FMS Proposal (not exclusive) A d(p)+Aup0p0+X measurement of the parton model gluon density distributions xg(x) in gold nuclei for 0.001< x <0.1. For 0.01<x<0.1, this measurement tests the universality of the gluon distribution. Characterization of correlated pion cross sections as a function of Q2 (pT2) to search for the onset of gluon saturation effects associated with macroscopic gluon fields. (again d-Au) Measurements with transversely polarized protons that are expected to resolve the origin of the large transverse spin asymmetries in reactions for forward  production. (polarized pp) 7/29/2019 L.C.Bland, Como

Frankfurt, Guzey and Strikman, J. Phys. G27 (2001) R23 [hep-ph/0010248]. constrain x value of gluon probed by high-x quark by detection of second hadron serving as jet surrogate. span broad pseudorapidity range (-1<h<+4) for second hadron  span broad range of xgluon provide sensitivity to higher pT for forward p0  reduce 23 (inelastic) parton process contributions thereby reducing uncorrelated background in Df correlation. 7/29/2019 L.C.Bland, Como Pythia Simulation

Sivers mechanism asymmetry is present for forward jet or g Disentangling Dynamics of Single Spin Asymmetries Spin-dependent particle correlations Collins/Hepplemann mechanism requires transversity and spin-dependent fragmentation Sivers mechanism asymmetry is present for forward jet or g Large acceptance of FMS will enable disentangling dynamics of spin asymmetries 7/29/2019 L.C.Bland, Como

Loaded On a Rental Truck for Trip To BNL New FMS Calorimeter Lead Glass From FNAL E831 804 cells of 5.8cm5.8cm60cm Schott F2 lead glass Loaded On a Rental Truck for Trip To BNL 7/29/2019 L.C.Bland, Como

FPD++ Physics for Run6 Run-7 FMS Run-6 FPD++ Run-5 FPD We intend to stage a large version of the FPD to prove our ability to detect direct photons. 7/29/2019 L.C.Bland, Como

How do we detect direct photons? Isolate photons by having sensitivity to partner in decay of known particles: π0 M=0.135 GeV BR=98.8% K0  π0π0   0.497 31%   0.547 39%  π0    0.782 8.9% Detailed simulations underway 7/29/2019 L.C.Bland, Como

Where do decay partners go? m = p0(h) di-photon parameters zgg = |E1-E2|/(E1+E2) fgg = opening angle Mm = 0.135 GeV/c2 (p0) Mm=0.548 GeV/c2 (h) Gain sensitivity to direct photons by making sure we have high probability to catch decay partners This means we need dynamic range, because photon energies get low (~0.25 GeV), and sufficient area (typical opening angles few degrees at our h ranges). 7/29/2019 L.C.Bland, Como

Sample decays on FPD++ With FPD++ module size and electronic dynamic range, have >95% probability of detecting second photon from p0 decay. 7/29/2019 L.C.Bland, Como

Ongoing progress on developing luminosity and polarization Timeline for the Baseline RHIC Spin Program Ongoing progress on developing luminosity and polarization Research Plan for Spin Physics at RHIC (2/05) Program divides into 2 phases: s=200 GeV with present detectors for gluon polarization (g) at higher x & transverse asymmetries; s=500 GeV with detector upgrades for g at lower x & W production 7/29/2019 L.C.Bland, Como

Summary / Outlook Large transverse single spin asymmetries are observed for large rapidity p0 production for polarized p+p collisions at s = 200 GeV AN grows with increasing xF for xF>0.35 AN is zero for negative xF Large rapidity p0 cross sections for p+p collisions at s = 200 GeV is in agreement with NLO pQCD, unlike at lower s. Particle correlations are consistent with expectations of LO pQCD (+ parton showers). Large rapidity p0 cross sections and particle correlations are suppressed in d+Au collisions at sNN=200 GeV, qualitatively consistent with parton saturation models. Plan partial mapping of AN in xF-pT plane in RHIC run-5 Propose increase in forward calorimetry in STAR to probe low-x gluon densities and establish dynamical origin of AN (complete upgrade by 10/06). 7/29/2019 L.C.Bland, Como

Backups 7/29/2019 L.C.Bland, Como

Towards establishing consistency between FPD (p0)/BRAHMS(h-) Extrapolate xF dependence at pT=2.5 GeV/c to compare with BRAHMS h- data. Issues to consider: <h> of BRAHMS data for 2.3<pT<2.9 GeV/c bin. From Fig. 1 of PRL 94 (2005) 032301 take <h>=3.07  <xF>=0.27 p-/h- ratio? Results appear consistent but have insufficient accuracy to establish p+pp-/p0 isospin effects 7/29/2019 L.C.Bland, Como

Systematics Measurements utilizing independent calorimeters consistent within uncertainties Systematics: Normalization uncertainty = 16%: position uncertainty (dominant) Energy dependent uncertainty = 13% - 27%: energy calibration to 1% (dominant) background/bin migration correction kinematical constraints 7/29/2019 L.C.Bland, Como

FPD Detector and º reconstruction robust di-photon reconstructions with FPD in d+Au collisions on deuteron beam side. average number of photons reconstructed increases by 0.5 compared to p+p data. 7/29/2019 L.C.Bland, Como

d+Au  p0+p0+X, pseudorapidity correlations with forward p0 HIJIING 1.381 Simulations increased pT for forward p0 over run-3 results is expected to reduce the background in Df correlation detection of p0 in interval -1<h<+1 correlated with forward p0 (3<h<4) is expected to probe 0.01<xgluon<0.1  provides a universality test of nuclear gluon distribution determined from DIS detection of p0 in interval 1<h<4 correlated with forward p0 (3<h<4) is expected to probe 0.001<xgluon<0.01  smallest x range until eRHIC at d+Au interaction rates achieved at the end of run-3 (Rint~30 kHz), expect 9,700200 (5,600140) p0-p0 coincident events that probe 0.001<xgluon<0.01 for “no shadowing” (“shadowing”) scenarios. 7/29/2019 L.C.Bland, Como

STAR Forward Calorimetry Recent History and Plans Prototype FPD proposal Dec 2000 Approved March 2001 Run 2 polarized proton data (published 2004 spin asymmetry and cross section) FPD proposal June 2002 Review July 2002 Run 3 data pp dAu (Preliminary An Results) FMS Proposal: Complete Forward EM Coverage (hep-ex/0502040). 7/29/2019 L.C.Bland, Como

Students prepare cells at test Lab at BNL 7/29/2019 L.C.Bland, Como