The Electron Ion Collider: Why? How? When?

Transcription

1 The Electron Ion Collider: Why? How? When? Abhay Deshpande March 27, 2012 JPS Meeting

2 2 Inclusive jet p T spectrum!! Extending the high p T limit beyond Tevatron reach!! Accessing the low p T part using different jet reconstruction algorithms!! Good agreement with NLO predictions 1/2π dσ/(dηdpt) [pb/gev] data / theory Combined MB Combined HT STAR, PRL 97 (2006), NLO QCD (Vogelsang) STAR p+p g jet + X s=200 GeV midpoint-cone r cone= <η<0.8 RHIC Systematic Uncertainty Theory Scale Uncertainty (a) (b) p T [GeV/c] [nb/(gev/c)] JET dp T JET! / dy 2 d JET < y <2.1 (" ) K T D=0.7-1 CDF data ( L = 1.0 fb ) Systematic uncertainties NLO: JETRAD CTEQ6.1M corrected to hadron level JET µ R = µ F = max p T / 2 = µ 0 PDF uncertainties JET 1.1< y <1.6 (" JET 0.7< y <1.1 JET 3 0.1< y <0.7 (" ) -3 ) JET 6 y <0.1 (" ) Tevatron JET p T [GeV/c] (pb/gev)!/dydp d 2 T CMS preliminary, 60 nb 11-1 NLO pqcd+np Exp. uncertainty R=0.5 PF Anti-k T s = 7 TeV y <0.5 ("24) 0.5# y <1.0 ("256) 1.0# y <1.5 ("64) 1.5# y <2.0 ("16) 2.0# y <2.5 ("4) 2.5# y <3.0 ("1) LHC p (GeV) T coverage of p T range com triggers with d thre experimental syst uncertainties dom by jet energy sca resolution, and luminosity measur Hard Probes 20 Hermine K. Wöhri : CMS results in pp c A. Deshpande, EIC: Why? How? When? 2

3 Gluons are the key ingredient in QCD that distinguish it from QED. What is their role in QCD at high energy? DO WE UNDERSTAND GLUONS? A. Deshpande, EIC: Why? How? When? 3

4 Measurement of Glue at HERA Scaling violations of F 2 (x,q 2 ) F 2 (x, Q 2 ) lnq 2 G(x, Q 2 ) NLO pqcd analyses: fits with linear DGLAP* equations Gluon dominates *Dokshitzer, Gribov, Lipatov, Altarelli, Parisi 4 A. Deshpande, EIC: Why? How? When?

5 Gluon distribution at low-x understood? xf H1 and ZEUS HERA I+II I+II I Combined PDF PDF Fit Fit xs (! 0.05) xg (! 0.05) xs (! 0.05) xg (! 0.05) xg (! 0.05) Q = 2 GeV GeV GeV HERAPDF1.5 (prel.) HERAPDF1.5 HERAPDF1.0 (prel.) exp. uncert. exp. uncert. model uncert. exp. uncert. parametrization uncert. model uncert. model uncert. xu v parametrization uncert. xu v parametrization uncert. HERAPDF xu v xd v xs (! 0.05) xd v xd v x 2 HERA Structure Functions Working Group July 20 x x 1 HERA Structure Functions Working Group July 20 Indefinite rise: Infinite high energy hadron cross section? Could this be an artifact of using of linear DGLAP in gluon extraction? How would we find out? Need theory development No higher energy e-p collider than HERA! Nuclei: naturally enhance the densities of partonic matter Why not use Nuclear DIS at high energy? Need experimental measurements at lower x! A. Deshpande, EIC: Why? How? When? 5

6 Physics at Low x & Color Glass Condensate See Ann. Rev. Nucl Part (60) 20 F. Gelis et al.,, arxiv: ) Kowalski, Teany PRD 68: Method of including non-linear effects McLerran & Venugopalan Small coupling, high gluon densities BK/JMWLK equations lead to a Saturation Scale Q S (Y) Wave function: Color Glass Condensate in infinite momentum frame Infinite Momentum Frame (IMF) BFKL (linear QCD) gluon splitting functions higher gluon density BK (non Could linear) be explored recombination cleanly of gluons in future with restricts a high gluon energy density At Q S gluon electron-nucleus emission balances Collider the recombination A. Deshpande, EIC: Why? How? When? 6

7 ? 1980s 1990/2000s EVOLUTION: OUR UNDERSTANDING OF THE NUCLEON SPIN: WHAT ROLE DO GLUONS PLAY? A. Deshpande, EIC: Why? How? When? 7

8 Status of Nucleon Spin Crisis Puzzle 1 2 = 1 2 Σ + L q + g + L g We know how to determine ΔΣ and Δg precisely: data+pqcd ½ (ΔΣ) ~ 0.15 : From fixed target pol. DIS experiments RHIC-Spin: Δg not large as anticipated in the 1990s, but measurements & precision needed at low & high x Run5 Run6 Run9 A. Deshpande, EIC: Why? How? When? 8

9 Q 2 = GeV 2 de Florian, Sassot, Stratmann & Vogelsang Global analysis: DIS, SIDIS, RHIC-Spin Uncertainly on ΔG large at low x Present Low x measurements =Opportunity! A. Deshpande, EIC: Why? How? When? 9

10 6D Dist. Wpu(x,kT,r ) Wigner distributions d3r d2kt drz TMD PDFs GPDs/IPDs f1u(x,kt),.. h1u(x,kt) 3D imaging d2kt PDFs f1u(x),.. h1u(x) A. Deshpande, EIC: Why? How? When? d2rt 1D dx & Fourier Transformation Form Factors GE(Q2), GM(Q2)

11 Do we really understand QCD? While there is no reason to doubt QCD, our level of understanding of QCD remains extremely unsatisfactory: both at low & high energy Can we explain basic properties of hadrons such as mass and spin from the QCD degrees of freedom at low energy? What are the effective degrees of freedom at high energy? How do these degrees of freedom interact with each other and with other hard probes? What can we learn from them about confinement & universal features of the theory of QCD? After ~20+ yrs of experimental & theoretical progress, we are only beginning to understand the many body dynamics of QCD A. Deshpande, EIC: Why? How? When? 11

12 The Proposal: Future DIS experiment at an Electron Ion Collider: A high energy, high luminosity (polarized) ep and ea collider and a suitably designed detector [2] [1] [3] Measurements: [1] Inclusive [1] and [2] or [3] Semi-Inclusiv [1] and [2] and [3] Exclusive Inclusive Exclusive Low High Luminosity Demanding Detector capabilities

13 EIC : Basic Parameters E e = GeV (5-30 GeV variable) E p =250 GeV ( GeV Variable) Sqrt(S ep ) = 0 (30-170) GeV X min = -4 ; Q 2 max = 4 GeV Beam pol. ~ 70% for e,p,d, 3 He Luminosity L ep = cm -2 s -1 Minimum Integrated luminosity: 50 fb -1 in yrs (0 x HERA) Possible with 33 cm -2 s -1 Recent projections much higher Nuclei: p->u; E A =20-0 GeV/N Sqrt(S ea/n ) = 14-1 GeV L ea /N = 33 cm -2 s -1 A. Deshpande, EIC: Why? How? When? 13

14 Machine Designs erhic at Brookhaven National Laboratory using the existing RHIC complex ELIC at Jefferson Laboratory using the Upgraded 12GeV CEBAF Both planned to be STAGED First stage: s = ~50-70 GeV DOE Guidance for Stage 1: $500M Upgrade: s = ~0-170 GeV

15 erhic at BNL 0.60 GeV New Detector? 5.50 GeV.4 GeV 15.3 GeV 20.2 GeV 25.1 GeV 30.0 GeV 30 GeV GeV 3.05 GeV 7.95 GeV GeV GeV GeV GeV BNL: add e - Energy Recovery Linac in RHIC tunnel; 6 vertically stacked recirc. passes; stage e - energy from 5 eventually to ~30 GeV by adding SRF cavities; reuse as much as possible of existing RHIC infrastructure estar Meets performance requirements & has straightforward upgrade path Vigorous R&D to demonstrate various novel apsects Stage 1 can fit in the DOE guidance Technical review in Aug. 11, Cost review in Spring 2012 A. Deshpande, EIC: Why? How? When? 15

16 MEIC : Medium Energy EIC medium-energy IPs polarimetry low-energy IP Exists Three compact rings: 3 to 11 GeV electron Up to 12 GeV/c proton (warm) Up to 60 GeV/c proton (cold) A. Deshpande, EIC: Why? How? When? 16

17 Forward / Backward Spectrometers: Detector Concepts Similar! Central detector Solenoid yoke + Muon Detector TOF BNL EIC Task Force (not to scale) 4-5m EM Calorimeter HTCC RICH or DIRC/LTCC Tracking Solenoid yoke + Hadronic Calorimeter RICH EM Calorimeter Hadron Calorimeter Muon Detector JLab EIC WG 2m 3m 2m A. Deshpande, EIC: Why? How? When? 17

18 A set of meetings on the Physics of EIC: An International Group met at the INT September December 20 to define: The Science of EIC Golden Measurements Institute of Nuclear Theory (INT) at U. of Washington: Sep-Nov 20 Organizers: D. Boer, M. Diehl, R. Milner, R. Venugopalan, W. Vogelsang See the INT WebPage for details of all studies: INT Workshop Write-up: A. Deshpande, EIC: Why? How? When? 18

19 Science of EIC: Precise Investigations of the Glue & Sea Quarks Understanding the proton structure including its spin & flavor: Nucleon spin (polarized parton distribution functions) Transverse Momentum Distributions of quarks & gluons Momentum correlated Spatial distributions of quarks and gluons (orbital angular momenta) through Generalized Parton Distributions Understanding the structure and partonic dynamics in nuclei Parton correlations, their propagation, energy loss in colored fields, fragmentation/hadronization in cold nuclear matter Understanding QCD at the highest possible gluon density, does a Color Glass Condensate exist? High energy, beam polarization, and a full acceptance detector: why not explore precision electroweak physics and EW (spin) structure functions A. Deshpande, EIC: Why? How? When? 19

20 Golden Measurements Matrix A. Deshpande, EIC: Why? How? When? 20

21 Golden Measurement Matrix A. Deshpande, EIC: Why? How? When? 21

22 Nucleon Spin: Precision measurement of ΔG Sassot & Stratmann Yellow band (left) reduces to the band shown with red dashed line (right) A. Deshpande, EIC: Why? How? When? 22

23 GPDs Orbital Angular Momenta? Nonviolent collisions: Nucleon Spin = 1 2 = J quark + J gluons J q = 1 2 Σ + L q J q = xdx [H(x, t, ζ)+e(x, t, ζ)] GP Ds : H, E, H,Ẽ 0 Similar expression for gluon J g total spin contribution through DVVM Needs measurements over a wide range in each of the variables Simulations & impact studies: underway in BNL & JLab EIC groups A. Deshpande, EIC: Why? How? When? 23

24 Transverse Parton Imaging & GPDs Fourier transform of momentum transfer x ~ x < 0.1 x ~ 0.3 x ~ 0.8 EIC: 1) x < 0.1: gluons! 2) ξ ~ 0 the take out and d x - ξ x + ξ put back gluons act coherently.,γ A. Deshpande, EIC: Why? How? When? 24

25 Measurement of Gluons at Low x Diffractive cross section F 2 (x,q 2 ) and its scaling violations of Nucleons & Nuclei Structure function F L (x,q 2 ) Q 2 = Sxy Quarks and anti-quarks Gluon momentum distribution Needs change of beam energies to directly measure F L A. Deshpande, EIC: Why? How? When? 25

26 F 2,L sensitivity studies ECA & MS + BNL Task Force A. Deshpande, EIC: Why? How? When? 26

27 Di-Hadron correlations: forward p-p, RHIC Hadron suppression factor 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 ± J/ψ, 0-20% h+π 0, 60-88%, PHENIX Preliminary h+π 0, 0-20%, PHENIX Preliminary s = 200 GeV d +Au/p+p -2 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 -1 A. Deshpande, EIC: Why? How? When? 27 Inferred momentum fraction of sampled gluons arxiv: v1 STAR: Disappearance of away-side jet in central d-au collisions can be well described by CGC inspired calculations, but not by pqcd. PHENIX: Suppression h+π 0 & J/Ψ in central but not peripheral, but not in peripheral also hints to the same physics

28 Measure Di-Jets in e-p vs. e-a A golden measurement at the EIC $! " # # %$&'( %$&'" A ) φ!"#$%&'"( Dominguez, Xiao, Yuan 11 "#)#* +,- #)#.#&'( -#)#* +," #)#"#&'( :'#$#.3#&'( */02#-33#&'( 2456'47#-33#&'(82 "#9#2456'47#-33#&'(! " #$#%#&'( " L. Zheng & T. Ullrich Realistic detector simulation Assume only 30% suppression Minimal (7 minutes) of EIC operation Shows detection suppression Dominguez, Xiao, Yuan 11 ea/ep without smear no suppression ea/ep with smear & 30% suppression 0.81±0.03 and 0.56±0.02 A. Deshpande, EIC: Why? How? When? 28

29 EIC Project status and plans A collaboration of highly motivated people: EIC Collaboration Web Page: 0+ dedicated physicists from 20+ institutes Task Forces at BNL (Aschenauer & Ullrich) and at Jefferson Laboratory (Ent) EIC Project co-ordinators/contacts persons: R. Milner & A. Deshpande EIC International Advisory Committee formed by the BNL & Jlab Management to steer this project to realization: W. Henning (ANL/RIKEN, Chair), J. Bartels (DESY),A. Caldwell (MPI, Munich) A. De Roeck (CERN), R. Gerig (ANL), D. Hetrzog (U of W), X. Ji (Maryland), R. Klanner (Hamburg), A. Mueller (Columbia), S. Nagaitsev (FNAL), N. Saito (J-PARC), Robert Tribble (Texas A&M), U. Wienands (SLAC), V. Shiltev (FNAL) A White for NSAC Long Range Plan 2012/2013 to be produced by Spring 2012 Writing Group: E; Aschenauer, M. Diehl, H. Gao, A. Hutton, T. Horn, K. Kumar, Y. Kovchegov, M. Ramsey-Musolf, T. Roser, F. Sabatie, E. Sichtermann, T. Ullrich, W. Vogelsang, F. Yuan Senior Advisors: A. Mueller, R. Holt Co-Chairs/Editors: A. Deshpande, J. Qiu, Z.E. Meziani A. Deshpande, EIC: Why? How? When? 29

30 H. Montgomery, Jeff. Laboratory Director EIC Realization Possible Time Line Activity Name Gev Upgrade FRIB EIC Physics Case NSAC LRP CD0 Machine Design/R&D CD1/D nselect erhic operation Could begin CD2/CD3 Construction Construction Schedule Highly Site Dependent A. Deshpande, EIC: Why? How? When? 30

31 Concluding remarks: The science case for EIC: Understand QCD: Precision study of the role of gluons & sea quarks in QCD through systematic study of nucleons and nuclei over a wide range in energy and kinematics and a comprehensive detector EIC will study the 3D structure (structure and dynamics) of the partons in protons and nuclei, as no other facility in the world EIC s machine parameters, their flexibility & a well integrated detector will be crucial to achieve this goal Physics of EIC: Gluons/sea quarks complimentary to future JLab12 & COMPASS EIC HERA HERA (protons) not polarized, did not have nuclei, and EIC will be 0-00 times more luminous. Detectors well-integrated in to machine lattice. The EIC Collaboration & the BNL+Jlab managements are moving (together) towards realization: 1 st Milestone: NSAC approval 2013/14 A. Deshpande, EIC: Why? How? When? 31