Highlights from RHIC Spin Program

Transcription

1 Highlights from RHIC Spin Program Ming Xiong Liu Los Alamos Na;onal Lab - Longitudinal spin program - Transverse spin program Ming X. Liu 5/31/2010 MENU2010 W&M 1

2 The Relativistic Heavy Ion Collider at Brookhaven National Laboratory BRAHMS R-HI New state of matter QGP De-confinement PHENIX STAR polarized proton Nucleon Spin Structure Spin Fragmentation pqcd RHIC is a QCD lab Ming X. Liu 5/31/2010 MENU2010 W&M 2

3 Highest Energy Polarized Proton Siberian Snakes Absolute Polarimeter H jet RHIC pc Polarimeters PHOBOS BRAHMS Siberian Snakes PHENIX STAR & pp2pp Spin Flipper Polarized Source Spin Rotators Strong Snake Par;al Snake Helical Par;al Snake Energy: up to 500GeV 200 MeV Polarimeter LINAC BOOSTER AGS Pol: 70% Rf Dipole AGS Internal Polarimeter AGS pc Polarimeter Ming X. Liu 5/31/2010 MENU2010 W&M 3

4 Ming X. Liu 5/31/2010 MENU2010 W&M 4 Experimental Observables = = L LL A A Asymmetries PHENIX and STAR: all BRAHMS: transverse beams only + + = = T TT A A

5 Philosophy: The PHENIX Detectors High rate capability to measure rare probes, limited acceptance. 2 central spectrometers Track charged par;cles and detect electromagne;c processes η < 2 forward muon spectrometers Iden;fy and track muons < η < 2.4 2π azimuth 2 forward calorimeters as of 2007! Measure forward pions 3.1 < η < 3.7 2π azimuth Rela;ve Luminosity Beam- Beam Counter BBC Zero- Degree Calorimeter ZDC azimuth Ming X. Liu 5/31/2010 MENU2010 W&M 5

6 The STAR Detectors PHENIX STAR PHOBOS RHIC 1.2 km BRAHMS &PP2PP Time Projection Chamber η <1.6 Forward TPC 2.5< η <4.0 Silicon Vertex Tracker η <1 Barrel EMC η <1 Endcap EMC 1.0< η <2.0 Forward Pion Detector 3.3< η <4.1 Forward Meson Spectr. 2.5 < η < 4 Ming X. Liu 5/31/2010 MENU2010 W&M 6

7 RHIC Spin Run History Pol Lpb^- 1 Results % 0.15 first pol. pp collisions! % 1.6 pi^0, photon cross seckon, A_LLpi^ % 3.0 absolute beam polarizakon with polarized H jet % 13 large gluon pol. ruled out P^4 x L = % 46 first long spin run P^4 x L = no spin running % 20 short run GeV/200GeV first W measurements Run9 500 GeV Ming X. Liu 5/31/2010 MENU2010 W&M 7

8 Part I: Longitudinal Spin Physics Program The proton is viewed as being a bag of bound quarks and gluons interacting via QCD Spins + orbital angular momentum need to give the observed spin 1/2 of proton 1 2 = 1 2 Δq + L z z q + Δg + L g Fairly well measured only ~30% of spin Beginning to be measured at RHIC A future challenge Ming X. Liu 5/31/2010 MENU2010 W&M 8

9 + + + A LL = = a,b,c Δf a Δf b a,b,c f a f b d ˆ f a f b f c X f a ˆ a f b f X c h LL D fc d ˆ f a f b f c X h D fc A LL a gg Δg 2 + a qg ΔqΔg + a qq ΔqΔq' The LO result for a LL is nonzero for all subprocesses Ming X. Liu 5/31/2010 MENU2010 W&M 9

10 Pion produc;on and NLO pqcd Ming X. Liu 5/31/2010 MENU2010 W&M 10

11 RHIC data and Δg STAR, PRL PHENIX pi0 STAR inclusive jets PHENIX, PRL Ming X. Liu 5/31/2010 MENU2010 W&M 11

12 Impact of RHIC- Spin Program on Δg Prior to RHIC- Spin Program, Δg = 1~2 expected at scale of 1GeV Restored consistency between data and quark model predic;ons Major impact of program such large values of Δg seem to be excluded DSSV 08 χ 2 distribu;on as Δg is varied w/in x- range constrained by the RHIC data. RHIC constraints It is interes;ng to note that the best fit has a zero- crossing at x 0.1. Ming X. Liu 5/31/2010 MENU2010 W&M 12

13 Future New Δg Polarized hadron collisions double longitudinal spin asymmetry A LL = Δf a + A x a,q 2 Δf b B x b,q 2 dδ cd ab dt leading- order gluon interac;ons direct- photon produc;on heavy- flavor produc;on Other channels light hadrons etc. proton beam or or proton beam gluon gluon heavy flavor proton beam or or proton beam gluon photon Ming X. Liu 5/31/2010 MENU2010 W&M 13

14 W ± Produc;on and A μ + Bunce G. et al, hep-ph/ ν μ - W A + L = + Δd x 1ux 2 Δux 1 dx 2 ux 1 dx 2 + d x 1 ux 2 ν A L W + : Δu u Δd and d. A W L : Δd d and Δu u. Ming X. Liu 5/31/2010 MENU2010 W&M 14

15 First W ± Measurements from Run9 500 pp! Ming X. Liu 5/31/2010 MENU2010 W&M 15

16 Part II: Transverse Spin Physics Program RHIC 20,000 GeV beam Large Transverse Single Spin Asymmetry SSA in forward meson produc;on persists up to RHIC energy. FNAL 200 GeV beam AGS 22 GeV beam ZGS 12 GeV beam PRL 2004 PRD65, PLB261, PLB264, PRL36, Non-Perturbative cross section Perturbative cross section Ming X. Liu 5/31/2010 MENU2010 W&M 16

17 Theory: K T vs Collinear Factoriza;on Tran. Mom. Dep. Funs Sivers Fun Collins Fun f a q FF q h f b X Twist- 3 collinear Quark- gluon correl. Gluon- gluon correl. A N TMD Collinear/Twist- 3 pt Ming X. Liu 5/31/2010 MENU2010 W&M 17

18 A N P T Dependence Remains as a Challenge A N vs p T A N vs x F Run8 A N p T ~ p T p T 2 + Δ 2? Ming X. Liu 5/31/2010 MENU2010 W&M 18

19 Charm SSA to Probe Gluon Sivers Distribu;on D meson Single- Spin Asymmetry: Produc;on dominated by gluon- gluon fusion Sensi;ve to gluon Sivers distribu;on PHENIX data ruled out the max. gluon Sivers Much improved results expected Run A N µ Kang, Qiu, Yuan, Vogelsang, Phys. Rev. D 78, Ming X. Liu 5/31/2010 MENU2010 W&M 19

20 Future Transverse Spin Physics: A N Drell- Yan - >μ + μ - Transverse- Spin Drell- Yan Physics at RHIC h}p://spin.riken.bnl.gov/rsc/write- up/dy_final.pdf Important test at RHIC of recent fundamental QCD predic;ons for the Sivers effect, demonstra;ng ahrackve vs repulsive color charge forces Sivers Amplitude HERMES x Ming X. Liu 5/31/2010 MENU2010 W&M 20

21 Summary and Outlook Spin puzzle Gluon polariza;on Large Δg ruled out New probes, direct- photon, open charm Larger x- range in the future Sea quark polariza;on First W asymmetry observed Much improved results in the future Transverse spin physics Large SSAs observed at RHIC New study of QCD dynamics Charm SSA Drell- Yan SSA RHIC constraints Ming X. Liu 5/31/2010 MENU2010 W&M 21

22 backup Ming X. Liu 5/31/2010 MENU2010 W&M 22

23 Ming X. Liu 5/31/2010 MENU2010 W&M 23

24 but rising P T dependence is not predicted by the same fits Gordon AGS/RHIC 2008 X F >0.4 Admixture of Collins and Sivers? Current data can extend P T reach of measurements B.I. Abelev et al. STAR [arxiv:hep-ex/ v1],, submitted to PRL Data broken out in X F bins Ming X. Liu 5/31/2010 MENU2010 W&M 24

25 Attractive vs Repulsive Sivers Effects Unique Prediction of Gauge Theory! DIS: attractive Drell-Yan: repulsive Ming X. Liu 5/31/2010 MENU2010 W&M 25

26 Cri;cal Role of VTX/FVTX for Drell- Yan Tracking muons with MuTr+FVTX Prompt muons from DY Displaced tracks from π/k and heavy quark decays ϒ DCA < 1 cut: Increase DY/bb ~ 5 Ming X. Liu 5/31/2010 MENU2010 W&M 26

27 Transverse Physics W +/- & Z 0 Latest theore;cal progress Test ;me- reversal universality of Sivers func;ons with W/Z Expect large asymmetry from DIS fit Kang & Qiu PRL 103, Flavor- iden;fied Sivers Funs W +/- Expected GeV W +/- μ +/- ~20K Z 0 - > μ + μ - ~ 1K Z 0 Kang & Qiu arx Ming X. Liu 5/31/2010 MENU2010 W&M 27

28 RHIC/PHENIX Spin Run History and Prospect RHIC- RUN Pol% Lpb - 1 Results % 0.15 first pol p+p run@rhic! Transverse % 0.35 π 0 cross sec;on, A LL π % 0.12 Pol H- Jet, absolute beam polariza;on % 3.5 A LL π 0 ruled out large Δg, GRSV- Max- Like % 7.5 first dedicated long spin run 2.7 Transverse run NO spin run % 5.2 short run for HI baseline pp physics % 14 first 500GeV run! 55% GeV CAD Delivered Run9@500GeV CAD : From Run9 experience, reduced the enhanced design goals: P=70%, L = cm - 2 s - 1 or 7.5 pb - 1 /week at s = 200 GeV 12- week Run Delivered: 90pb - 1 PHENIXε=1/3 = 30pb - 1 With hardware upgrade, expect to achieve: 18~83 pb - 1 /week@500gev 12- week Run Delivered: 220~1000pb - 1 Goals 800pb - 300pb - 300pb - 70pb - PHENIXε=1/2 = 100~500pb - 1 Ming X. Liu 5/31/2010 MENU2010 W&M 28

29 Δq and Δq through W ± decay DOE Milestone HP8, 2013 W A + L = + Δd x ux Δux dx ux 1 dx 2 + d x 1 ux 2 A L W + : Δu u Δd and d. A W L : Δd d Δu and u. Ming X. Liu 5/31/2010 MENU2010 W&M 29

30 Daniel de Florian, RSC 09 Ming X. Liu 5/31/2010 MENU2010 W&M 30