APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th 2004 RHIC SPIN: Experimental Issues o Physics Goals o PDFs from hadron collisions? o A new experimental technique: Polarized proton-proton collisions at high energies! o First Results from RHIC o Upgrades o Summary Matthias Grosse Perdekamp, UIUC and RBRC

APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th 2004 (well known) (moderately well known) (unknown) (moderately well known) (unknown) Nucleon Structure Quark and Gluon (parton) Distribution Functions What is the origin of the Proton Spin?

APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th 2004 Gluon polarization Flavor separation of quark polarizations Transverse spin struc- ture of the Nucleon Proton Spin Structure at Hard Scales Physics Channels Inclusive jets, hadrons, heavy flavor, direct photons, in STAR and PHENIX Single lepton asymmetries A L (e,μ) in W-production in STAR and PHENIX A N in STAR, PHENIX and BRAHMS back to back correlations, A T in Collins- and interference fragmentation and A TT in Drell Yan in STAR and PHENIX. What is unique at RHIC? o Robust extraction of spin dep. pdfs from pQCD analysis o Broad x-range: 0.001<x<0.3 o Multiple channels: good control of of sys. and theor. uncertainties  determine G(x) and ∫∆G(x)dx ! o direct and theoretically clean flavor separation of spin dependent pdfs o sufficient statistical resolution  sea quark spin vs gluon spin o high precision measurements of multiple single and double spin asymmetries at hard scales aim at a separation of Sivers and Transversity contributions

APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th 2004 Can Gluon Distributions be Extracted from Hadron Collisions? I) Let’s take a look at G(x,Q 2 ) II) NLO pQCD vs RHIC data

APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th 2004 Global QCD Analysis for G(x,Q 2 ) and q(x,Q 2 ): J. Pumplin et.al JEHP 0207:012 (2002) x gluon down up-quarks anti-down Quark and Gluon Distributions error on G(x,Q 2 ) error for u(x,Q 2 ) +/- 10% +/- 5% error for d(x,Q 2 ) x CTEQ6: use DGLAP Q 2 -evolution of quark and gluon distributions to extract q(x,Q 2 ) and G(x,Q 2 ) from global fit to data sets at different scales Q 2. H1 + Zeus F 2 CDF + D0 Jets CTEQ5M1 CTEQ6M Ratio to CTEQ

APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th 2004 G(x,Q 2 ) and q(x,Q 2 ) + pQCD beautifully agree with HERA + Tevatron! J. Pumplin et.al JEHP 0207:012 (2002) D0 Jet Cross Section ZEUS F 2

APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th 2004 and RHIC ? q(x,Q 2 ), G(x,Q 2 ) and D(z,Q 2 ) + pQCD nicely consistent with experiment! o Good agreement between NLO pQCD calculations and experiment  can use a NLO pQCD analysis to extract spin dependent quark and gluon distributions from RHIC data! PHENIX π 0 cross section a |η|<0.35 Phys.Rev.Lett.91:241803,2003 STAR π 0 cross section a 3.4<η<4.0 Phys.Rev.Lett.92:171801,2004 gluon fragmentation !?

APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th 2004 Direct Photons: NLO pQCD vs RHIC data NLO-pQCD calculation –Private communication with W.Vogelsang –CTEQ6M PDF. –direct photon + fragmentation photon –Set Renormalization scale and factorization scale p T /2,p T,2p T The theory calculation shows good agreement with our result. Kensuke Okada’s SPIN 2004 talk

APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th years of spin dependent DIS Helicity difference distribution quarks ∆q(x) : moderately well known gluons ∆G(x) : unknown Helicity flip (transversity) distribution quarks δq(x) : unknown Current Experiments on Nucleon Structure (as reported at DIS 2004) Field started with polarized electron sources and targets Yale/SLAC mid 70s SLAC, CERN, DESY J. Ashman et al., Phys.Lett.B206:364,1988  “Proton Spin Crisis” > 1200 citations on SPIRES

APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th 2004 AGS LINAC BOOSTER Polarized Source Spin Rotators Partial Snake Siberian Snakes 200 MeV Polarimeter AGS Internal Polarimeter Rf Dipole RHIC pC Polarimeters Absolute Polarimeter (H jet) P HENIX P HOBOS B RAHMS & PP2PP S TAR Siberian Snakes Run 04 achieved: P b ~45%, 55 bunches New working point with long beam and polarization lifetimes Run 05 planned: Time to tune accelerator complex Measure: A LL (jets), A LL (π 0 ) Commission strong supercon- ducting AGS snake AGS pC Polarimeter A New Experimental Tool for Proton Spin Structure High Energy Polarized Proton Beams and Collisions Helical Partial Snake Strong Snake Spin Flipper Spin 2004: M. Bai, H. Huang, V. Ptitsyn, T. Roser A. Bravar, P. Cameron, D. Sviridia, A. Zelenski, T. Wise, W. McKay

APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th 2004 An Example: High Energy Proton Polarimeters for p= GeV/c High Energy Polarimeter Requirement for RHIC Spin  Absolute RHIC polarimeter  Fast relative RHIC and AGS polarimeters for monitoring and tuning  Local Polarimeters to confirm spin orientation at collision point RHIC polarimetery relies on newly observed spin asymmetries: o Sizeable elastic proton-Carbon spin asymmetries at high energies  J. Tojo et al. Phys. Rev. Lett. 89:052302, 2002 o Very forward neutron asymmetries  A. Bazilevsky et al. AIP Conf. Proc. 675: , 2003 o Spin asymmetries in forward multiplicity production as seen by beam-beam counters in STAR  J. Kiryluk, AIP Conf. Proc. 675, 424 (2003)

APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th 2004 Run 04: The Polarized Jet Target for RHIC Polarized Hydrogen Gas Jet Target thickness of > p/cm 2 polarization > 93% (+1 −2)%! no depolarization from beam wake fields Silicon recoil spectrometer to measure The left-right asymmetry A N in pp elastic scattering in the CNI region to  A N < accuracy. Transfer this to the beam polarization Calibrate the p-Carbon polarimeters For 2004 we expect to measure P B to 10% Courtesy Sandro Bravar, STAR and Yousef Makdisi, CAD

APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th 2004 Hor. pos. of Jet cts. = 2.5 mm Number of elastic pp events Jet profile FWHM ~ 6 mm As designed Data collected in this run: 100 GeV ~ 700,000 events at the peak of the analyzing power (~ 3 x 10 6 total useful pp elastic events) 24 GeV ~ 120,000 events at the peak of the analyzing power (~ 5 x 10 5 total useful pp elastic events) TDC: 1 ct = 1.2 ns ADC: 1 ct = 40 keV CNI peak A N 1 < E REC < 2 MeV Recoil protons elastic pp  pp scattering prompt events and beam gas  source calibration

APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th 2004 Local Polarimetry in PHENIX: Transverse Neutron Asymmetry in ZDC Yellow Blue Rotators on--> radial polarization Rotators on --> vertical polarization

APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th 2004 First Results: A N o Experiments are ready for spin measurements at low luminosity  relative luminosity ~ 5x10 -4  trigger  polarization analysis  data analysis PHENIX A N (π 0 ) and A N (π0) at |η|<0.35 C. Aidala, DIS 2004, to be published STAR A N (π 0 ) at 3.4<η<4.0 Phys.Rev.Lett.92:171801,2004 Run 02, ∫Ldt ~ 0.2pb -1, P~0.15 o First spin results from RHIC  A N sizeable in forward X F  A N compatible with 0 at η~0 (as expected from pQCD)

APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th 2004 Run3+4 B.Jager et al., PRD67, (2003) First results on longitudinal double spin asymmetries from RHIC  consistent with DIS sample  result disfavors large ∆G  if ∫Ldt = 3pb -1 and P-0.4 (2005) errors will reduce by factor 8 Experiments are ready for spin measurements at low to moderate luminosities!  relative luminosity ~5x10 -4  trigger  polarization analysis  data analysis First Results: A LL Run 3 and 4 combined ∆G(x)=G(x) GRSV ∆G(x)

APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th 2004 Schedule for RHIC Spin …. example: STAR 32 week scenario  all schedules subject to further advances in RHIC operations and/or funding! pp  156pb -1 √s= ……………………… GeV ………………… | P= …………………………………………. Inclusive hadrons + Jets Transverse Physics Charm Physics direct photons Bottom physics W-physics A LL (hadrons, Jets)A LL (charm) A LL (γ) AL(W)AL(W) L= 6x10 30 cm -2 s -1 8x10 31 cm -2 s -1

APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th 2004 Gluon Polarization at Low Luminosity: Inclusive Jets and Hadrons: (1pb -1 < ∫Ldt < 30pb -1, 0.4<P<0.6) GRSV standard ∆G(x)  Gluon distribution from NLO pQCD fit to DIS data on A 1, Gluck Reya, Stratmann, Vogelsang Phys. Rev. D63:094005, 2001 A LL in inclusive π 0 production (PHENIX) A LL ( π 0 ) ∫Ldt=3pb -1 P=0.4 Vogelsang hep-ph/ Input: ∆G(x)=G(x) GRSV: standard ∆G(x) ∆G(x)=0 ∆G(x)= -G(x) A LL in inclusive jet production (STAR) Jager, Stratmann, Vogelsang hep-ph/ A LL (Jets) ∫Ldt=3pb -1 P=0.4 Input: ∆G(x)=G(x) GRSV: standard ∆G(x) ∆G(x)= -G(x) ∆G(x)=0 p T [GeV/c] Expected in run 05: ∫Ldt =5pb -1 P =0.5 All required instrumentation in STAR and PHENIX is in place!

APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th 2004 Gluon Polarization at Moderate Luminosity: Charm Production: ( ∫Ldt > 30pb -1, P>0.6) A LL for single electrons in PHENIX from Wei Xie, PHENIX --- ∫Ldt=32pb ∫Ldt=320pb -1 GS-A/B/C: ∆G(x g ) parametrization from Gehrmann and Stirling Phys.Rev. D ,1996 ∫G A (x)dx =1.8 ∫G B (x)dx =1.6 ∫G C (x)dx =0.2 Silicon Vertex Detector Upgrade!

APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th 2004 Sensitivity to Gluon Polarization at RHIC from Les Bland, STAR x gluon Good control of experimental and theoretical uncertainties! PHENIX and STAR are sensitive to ∆G through several independent channels: Inclusive photons, inclusive jets, jet- photon, J/ψ production, heavy flavor production GS-A/B/C: ∆G(x g ) parametrization from Gehrmann and Stirling Phys.Rev. D ,1996 ∫G A (x)dx =1.8 ∫G B (x)dx =1.6 ∫G C (x)dx =0.2

APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th 2004 Sensitivity to Gluon Polarization at RHIC SMC, B. Adeva et al. hep-ex/ HERMES Phys. Rev.Lett.84: ,2000 (II) RHIC spans a broad range of x gluon  Determine first moment ∫∆G(x)dx = gluon contribution to the proton spin! RHIC data at hard scale  pQCD applicable for the extraction of polarized pdfs. (I) Assumes data sample of 320pb -1 at √s=200 GeV and 800pb -1 at √s=500 GeV; P=0.7. (This is baseline spin!) Upgrades extending kinematic coverage to low x decrease error on ∫∆G(x)dx (low x behavior has been critical in proton spin structure in the past: SLAC E80/E130 vs EMC  spin crisis) (IV) (III) from F.-H. Heinsius, DIS 2004

APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th 2004 W Z W Production in Polarized pp Collisions Single Spin Asymmetry in the naive Quark Parton Model Experimental Requirements:  tracking at high p T  event selection for muons difficult due to hadron decays and beam backgrounds. Parity violation of the weak interaction in combination with control over the proton spin orientation gives access to the flavor spin structure in the proton!

APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th 2004 Can We Connect Observables: inclusive A L (lepton) with quark polarizations?  Access to quark polarizations through measurements of inclusive longitudinal measurements of inclusive longitudinal single spin asymmetry? single spin asymmetry? –Yes! Complete theoretical treatment from first principles by Nadolsky and Yuan at NLO pQCD (Nucl. Phys.B 666(2003) 31). p T   GeV]  Machine and detector requirements: –∫Ldt=800pb-1, P=0.7 at √s=500 GeV –Upgrades: o Muon trigger in PHENIX o Forward tracking in STAR

APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th 2004 Quark Polarization: RHIC vs HERMES –W-production at RHIC No fragmentation ambiguity x-range limited –Semi-inclusive DIS Wide x-range Limited sensitivity to sea flavors Fragmentation functions poorly known at low scales (HERMES) from Naohito Saito, PHENIX

APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th 2004 (A) Physics Channels for Low Luminosity Transverse Spin at RHIC STAR Phys. Rev. Lett. 92:171801, 2004 Boer and Vogelsang (hep-ph/ ): azimuthal back to back correlation between hadrons in opposite hemisphere jets: Separation of intrinsic transverse quark spin (transversity) from trans- verse momentum effects (Sivers)? Clean channel for Sivers effect! STAR, PHENIX and BRAHMS STAR and PHENIX (I) (II)

APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th 2004 (B) Physics Channels for high L Transverse Spin at RHIC J.C. Collins, Nucl. Phys. B396, 161(1993) R. Jaffe, X.Jin, J. Tang Phys. Rev. D57 (1999)5920 J. Collins, S. Heppelmann, G. Ladinsky, Nucl.Phys. B420 (1994)565 Statistical sensitivity for A T with 32pb -1 HERMES, COMPASS and Jefferson Lab Separate transverse quark spin (transversity) and transverse momentum contributions (Sivers) in semi- inclusive deep Inelastic scattering: o low scale leads to significant theoretical ambiguities o Final data set from HERMES available in mid 2005 Brahms A N measurements from 2004 and 2005 polarized proton runs! Brief PHENIX and STAR runs on A N and back-to-back correlations as ∫ Ldt/week>1pb -1 /week (2006?) Brief PHENIX and STAR runs on A T as ∫ Ldt/week>10pb-1/week Spin Rotators: Give flexibility! STAR and PHENIX Transverse Spin Physics Elsewhere

APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th 2004 Upgrades and RHIC Spin I) Upgrades required for core spin program flavor separation of spin dependent quark distribution in W-production STAR: integrated forward tracking PHENIX: muon trigger II)Upgrades aimed at a precision measurement of the first moment ∫∆G(x)dx  constrain orbital angular mometum? STAR: micro vertex detector PHENIX: Silicon Vertex Detector, nose cone calorimeter

APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th 2004 prompt photon GS95 Measurement of the first moment ∫∆G(x)dx   G at low x  Silicon Tracker +NCC Upgrades extends the range of x G for the prompt-  measurement down to X G ~0.001 at  s =200 GeV Measurement of ∫∆G(x)dx over a wide x range will be essential in constraining spin sum 1/2∆ Σ + ∆G+L z Sensitivity to shape of polarized gluon distribution over a large x range (important input in fixing the shape and extrapolation to low x in global QCD analysis aimed at extracting ∆G)

APS Topical Group on Hadronic Physics RHIC Spin Fermilab, October 26 th 2004 Summary: Polarized Proton Collisions o A new experimental method has been successfully developed and we are beginning to exploit a truly novel experimental tool on proton spin structure. o Fixed target DIS experiments are carried out at comparably soft scales and are subject to various theoretical uncertainties. Leader- ship in the field will shift from DIS experiments to RHIC spin. o First physics results are available from exploratory runs promises to be the first spin physics run at RHIC. o Integrated forward tracking (STAR) and muon trigger upgrades (PHENIX) are necessary for W-physics. o Measurement of gluon spin (first moment) contribution to the proton spin requires larger kinematic range  eg. nose-cone calorimeter in PHENIX