The Electron-Ion Collider at BNL: Capabilities and Physics Highlights

Transcription

1 Hadron 2011 Munich 1 The Electron-Ion Collider at BNL: Capabilities and Physics Highlights D. Leinweber J.H. Lee Brookhaven National Laboratory

2 Outline Why do we need electron-ion collider What can we do with e + (heavy) A high energy/luminosity polarized e + polarized p new opportunities for spectroscopy How can it be realized adding an electron accelerator at RHIC (or adding a hadron accelerator at CEBAF) design and status of erhic at BNL 2

3 QCD and Fundamental Structure of Matter QCD is THE theory of the strong interaction: Theory of the matter - quarks and gluons Hadronic constituent degree of freedom is governed by quarks, but gluons drive the baryonic structure (responsible for > 98% mass) and dominates the QCD vacuum structure Mastering matter requires the fundamental understanding of gluon dynamics beyond current knowledge: new frontier machine to deeply explore the regime where new degree of freedom emerges 3

4 Accessing gluonic structure Hadron-Hadron Probe interaction directly via gluons: Lacks the direct access to partonic kinematics Lepton-Hadron (DIS) Indirect access to gluons (electro(-weak) structure function) : High precision and access to partonic kinematics (x, Q 2 ) 4

5 em F 2 -log (x) ) d 2 σ ep ex dxdq Glue in Matter: What do we know xq 4 2 x= x= x= x= = 4πα2 x=6.32 e.m. -5 x= x= x= x= x= x= x= x= x= x= x=0.005 HERA F 2 x=0.008 x=0.013 x= ZEUS NLO QCD fit x=0.005 H1 PDF 2000 fit x=0.021 H H1 (prel.) 99/00 x=0.013 ZEUS 96/97 BCDMS E665 NMC 0 x= x=0.05 x=0.08 x=0.13 x=0.18 x=0.25 x=0. 4 x= d 2 σ ep ex dxdq 2 -log (x) em F y + y2 F 2 (x, Q 2 ) y2 2 F L(x, Q 2 HERA F Scaling violation: df 2 /dlnq 2 2 and ). ZEUS NLO QCD fit Q 2 (GeV 2 ) xf(x,q 2 ) How to Measure Glue? = 4πα2 e.m. xq 4 x= x= x= x= x= x= y + y2 2 x=0.008 H1 PDF 2000 fit x=0.021 H H1 (prel.) 99/00 ZEUS 96/97 BCDMS E665 NMC x=0.032 x=0.05 x=0.08 x=0.13 x=0.18 x=0.25 x=0. 4 x=0.65 Q 2 (GeV 2 ) xg (! 1 / 20 ) H1 PDF 2000 ZEUS-S PDF CTEQ6.1 xg (! 1 / 20 ) Q 2 = GeV x xd V strongly with xs Q 2 (! : 1 Simple / 20 ) quark-parton model Bjorken NLO QCD and the measurement broadly similar : limited 0success Gluons dominate at low-x, xbut the underlying F 2 (x, Q 2 ) y2 2 F L(x, Q 2 ) linear DGLAP Evolution! G(x,Q 2 ) xf(x,q 2 ) xs (! 1 / 20 ) H1 PDF 2000 ZEUS-S PDF CTEQ6.1 Q 2 = GeV 2 xu V xd V xu V For smaller values of x, structure function F2 rises scaling breaks dynamics and the evolution is not well established 5

6 ? How gluons grow Regimes of QCD Wave Function H1 Collaboration H1 MRST 02 vs CTEQ 6 Linear DGLAP evolution: requires safety dynamics to prevent unitarity violation More work needed; MS vs scheme-invariant evolution. Saturation F regime arises naturally through non-linear BK/JIMWLK evolution L (x, Q 2 ) could be decisive. in the Color Glass Condensate (CGC) framework J. Blümlein RECAPP, Allahabad February 2009 p.35 characterized by saturation momentum QS(x,A) Experimental establishment on the theoretical evidence of saturation regime is fundamentally important for understanding of gluonic dynamics - strong interaction 6

7 Estimating saturation scale Gluonic saturation/recombination number of gluons per unit of transverse area: ρ~xg(x,q 2 )/πr 2 cross-section for gluon recombination: σ~ αs/q 2 saturation occurs when 1 < ρσ Q 2 < Qs 2 (x) saturation Qs varies Qs x 1/3 (phenomenological geometrical scaling at HERA) Qs A 1/3 (Gluons act coherently) Nuclear enhanced saturation scale To access saturation: increase energy (~1/x) or increase Qs (~A 1/3 ) 7

8 Nuclear enhanced saturation ~x7 With e+p, requiring Q2 lever arm need s =1-2 TeV (HERA s=320 GeV) x~-3 in dau at RHIC (approaching saturation) ~x500 Saturation scale Qs increases with heavy-ion significantly: Well in reach with e+au at RHIC 8

9 Probing Saturation regime e+p e+a Staged option: begins to reach into the saturation regime for heavy nuclei HERA (ep) energy range higher, but G(x,Q 2 ) in the very limited reach of the saturation regime erhic (ea) will probe deeply into the saturation region 9

10 Two Concepts to Realize an Electron-Ion Collider (EIC) erhic = RHIC + ELIC = CEBAF + Electron Ring (ERL) Hadron Ring Both designs in 2 stages Stage 1: 5+0 GeV/n e+au ( s=45 GeV/n) Stage II: GeV/n e+au ( s=125 GeV/n) Stage I: GeV/n e+au ( s=42 GeV/n) Stage II: 20+0 GeV/n e+au ( s=89 GeV/n)

11 erhic Design Under Active Consideration All in-tunnel approach uses two energy recovery linacs and 6 recirculation passes to accelerate the electron beam Staging: the electron energy will be increased in stages: 5-30 GeV by increasing the linac length RHIC: 325 GeV p or 130 GeV/u Au with DX magnets removed Current design allows for: more IP s reusing infrastructure + detector components for STAR, PHENIX easier upgrade path from 5 GeV erhic-i minimal environmental impact concerns IR design to reach 34 luminosity 11

12 erhic: The complete QCD factory Versatile e +A, e +p, p +p, A+A (up to U) High luminosity: L (e+p) = 1.5x34 cm -2 s -1 (HERA L =5x 31 ) Electron Accelerator Unpolarized and polarized (80%) e -,e GeV RHIC Unpolarized and polarized (70%) protons (325) GeV Light Ions (d, Si, Cu), Heavy Ions (Au,U) 50-0 (130) GeV/u Polarized light ions (He 3 ) 215 GeV/u 12

13 Key measurements for characterizing glue in matter in high energy electron-ion collisions Precisely mapping momentum and space-time distribution of gluons in nuclei in wide kinematic range including saturation regime through: Inclusive measurements of structure functions (F2,FL): ea ex, ea ex+gap Semi-inclusive and correlation measurements of final state distributions: ea e{π,k,φ,d,j/ψ...}x Exclusive final states: ea e{ρ,φ,j/ψ,γ}a Multiple controls: x, Q2, t, M X 2 for light and heavy nuclei 13

14 Example of the key measurements: Gluon distribution from F L G Pb (x)/g d (x) Q 2 : LHC d 2 σ ep ex dxdq 2 HKM -3 Color Glass Condensate FGS x = 4πα2 e.m. xq 4 Statistical errors for Ldt = fb -1 2 year running -2 RHIC -1 1 y + y2 2 F L ~ αsg(x,q 2 ) Systematic studies of F L (A,x,Q 2 ) G(x,Q2 ) with great precision Distinguish between models Utilize wide range of s of erhic F 2 (x, Q 2 ) y2 2 F L(x, Q 2 ) erhic: GeV + 0 GeV/n - estimate for fb -1 14

15 Example of the key measurements: Imbalance in di-hadron correlations Dominguez, Xiao and Yuan (20) e Q 2 q jet-1 2 <p T 1 < 3 GeV 1 <p T 2 < 2 GeV Q 2 =4GeV 2 Au x 18.5 q jet-2 p A Au Suppression of away side peak and increase of width (decorrelation at ΔΦ=π) at large Q 2 in ea due to multiple interactions between partons and dense nuclear matter in the CGC frame work 15

16 Example of the key measurements: Characterizing saturation regime through exclusive diffractive vector e e e e A coherent gap A A A in-coherent p n gap ea e{ρ,φ,j/ψ,γ}a Novel strong probe to investigate gluonic structure of nuclei: color dipole coherent and 2 sum e+al 3 e+cu 6 e+au 2 5 incoherent diffractive 1 4 interaction: Sensitive to 2 ) t (GeV 2 ) -t (GeV 2 ) -t (GeV 2 ) saturation ( s,b,a) Access to spatial distribution of gluons 16

17 polarized e + p at erhic: Spin and 3d imaging of nucleon Important Extension of Nucleon Structure Studies at HERA, RHIC, JLab, DIS, photon-gluon fusion Probing gluon spin ΔG at small-x (x > few 4 ) SIDIS Flavor decomposition of sea in broad x range DIS at High Q 2 Electroweak probes of proton spin structure Polarized DVCS, exclusive reactions + Lattice QCD GPD s map low-x transverse position-dependent PDF s Proton tomography via exclusive reactions x < x ~ x ~ 17

18 Summary The new proposed versatile and high-luminosity electron-ion collider (erhic) is to study one of the outstanding fundamental questions in QCD: Establish and explore new degree of freedom of gluonic property of matter - saturation regime by systematically studying the unprecedentedly accessed kinematic regime. Deeply extend the current understanding of nucleon structure: spin and 3d landscape. 18

19 erhic: New Opportunities also for Hadron Spectroscopy High luminosity (~5 fb-1 /year) Detector and machine designs to accommodate from exclusive photo-production to semiinclusive DIS over a wide kinematic range with excellent particle reconstruction and PID Broad range of reactions and energies with polarization Spectroscopy programs being developed: searches for Exotics, heavy quark spectroscopy... Join us... 19

20 Thank you erhic-detector 12:00 o clock 4T Solenoid -%*(&%.# /"#$%&.012"*%$.)(,($ 34!2"*%$.)(,($ 562/ /.7!18!$(9!%*#12($(&:%; <652!"#$%&!'(") *(+,%&!'(") 8$"0:.&7 erhic e PHENIX 8:00 o clock LINAC RF 4:00 o clock e STAR 6:00 o clock NSRL EBIS Booster AGS ERL Test Facility Tandems E.C. Aschenauer Seminar at Indiana University, April

21 Thank you erhic-detector 12:00 o clock 4T Solenoid -%*(&%.# /"#$%&.012"*%$.)(,($ 34!2"*%$.)(,($ 562/ /.7!18!$(9!%*#12($(&:%; <652!"#$%&!'(") *(+,%&!'(") 8$"0:.&7 erhic e PHENIX 8:00 o clock LINAC RF 4:00 o clock e STAR 6:00 o clock NSRL EBIS Booster AGS ERL Test Facility Tandems E.C. Aschenauer Seminar at Indiana University, April

22 Back-up slides 21

23 ea Science Matrix From Fall 20 INT Workshop 22

24 ep Spin Physics Matrix Science Deliverable Basic Measurement Uniqueness and Feasibility Requirements spin structure at small x contribution of Δg, ΔΣ to spin sum rule inclusive DIS minimal large x,q 2 coverage about C - 1 full flavor separation in large x,q 2 range strangeness, s(x)- s(x) semi- inclusive DIS very similar to DIS particle ID improved FFs (Belle,LHC) electroweak probes of proton structure flavor separation electroweak parameters inclusive DIS at high Q 2 some unp. results from HERA 20x250 to 30x325 positron beam polarized 3 He beam treatment of heavy flavors in pqcd DIS (g 1, F 2, and F L ) with tagged charm some results from HERA large x,q 2 coverage charm tag (un)polarized γ PDFs relevant for γγ physics at an ILC photoproduction of inclusive hadrons, charm, jets unp. not completely unknown tag low Q 2 events about C

25 Saturation at RHIC p y p y x x q q Uncorrected Coincidence Probability (rad -1 ) p+p π 0 π 0 + X, s = 200 GeV d+au π 0 π 0 + X, s = 200 GeV d+au π 0 π 0 + X, s = 200 GeV p T,L > 2 GeV/c, 1 GeV/c < p T,S < p T,L η L =3.2, η S =3.2 p+p STAR Preliminary Peaks Δφ σ ± 0.01 π 0.68 ± p T,L > 2 GeV/c, 1 GeV/c < p T,S < p T,L η L =3.2, η S =3.2 p T,L > 2 GeV/c, 1 GeV/c < p T,S < p T,L η L =3.1, η S =3.2 CGC+offset Peaks Peaks d+au peripheral Δφ σ d+au central Δφ σ ± ± 0.02 STAR Preliminary π 0.99 ± 0.06 STAR Preliminary π 1.63 ± Δφ Δφ Δφ Multiple scattering in the dense nucleus at forward in dau lead to mono-jet (decorrelation at ΔΦ=π) in CGC frame work ( J. Albacete and C. Marquet, to appear in PRL 20) Estimated x A ~ -3 24

26 Implication on understanding initial dynamics at RHIC t Expanding Flux Tubes freeze out hadrons 1/Q s gluons & quarks in eq. gluons & quarks out of eq. strong fields z E or B, or E&B Shattering CGC sheets provides the initial conditions for QGP evolution: Glasma Considerable success describing Rapid thermalization Long range rapidity correlation (ridge at RHIC and CMS) 25