Summary of subtopic Imaging QCD Matter : Generalized parton distributions and exclusive reactions

Transcription

1 Summary of subtopic Imaging QCD Matter : Generalized parton distributions and exclusive reactions of weeks 8 and 9 of the INT program Gluons and the quark sea at high energy: distributions, polarization, tomography V. Guzey On behalf of scientific coordinators: F. Sabatie and M. Burkardt Workshop on the Science case of an EIC Nov 18, 2010, Seattle, INT 1

2 Outline Agenda overview A road towards sea quark and gluon imaging at an EIC Golden GPD measurements Outlook 2

3 Agenda overview Weeks 8 and 9 were dedicated to Imaging QCD Matter, which for practical purposes means transverse momentum dependent distributions (TMDs) and semi inclusive DIS and generalized parton distributions (GPDs) and exclusive reactions TMD part coordinators: D. Hasch, M. Stratmann, F. Yuan GPD part coordinators: V. Guzey, F. Sabatie, M. Burkardt Wiki page for updates, discussions, simulations, additional material: 3

4 Agenda overview mixture of TMD (mostly week 8) and GPD (mostly week 9) talks 17 TMD talks and 11 GPD talks all talks and discussions online: 4

5 Agenda overview: discussed topics of the GPD part 1) Imaging in the b space: G. Miller, Techniques for imaging transverse distributions E. Aschenauer How to detect protons in exclusive processes M. Diehl, How well one needs to measure t for getting images in b space M. Burkardt, GPDs from DVCS? 2) DVCS, exclusive production of J\Psi, and phi mesons: phenomenology, models and MC simulations D. Müller, GPDs from deeply virtual exclusive processes (and beyond) P. Kroll, Hard exclusive photo and electroproduction of quarkonia S. Fazio, Simulations of DVCS with an EIC using MILOU M. Diehl, How large can GPDs Eq and Eg be? 3) Exclusive production of pseudoscalar mesons (pi, K) T. Horn, Imaging in exclusive processes S. Liuti, Partonic interpretation of GPDs 5 G. Goldstein, Limits on spin dependent GPDs from theory and experiment

6 Imaging QCD Matter (3D structure of the nucleon): digest of ideas discussed during the program talks by C. Weiss; M. Diehl; M. Burkardt Distributions in (x,kt): Distributions in (x,bt) TMDs GPDs and dipole amplitudes spin orbit correlations (kt vs. polariz.) indicate orbital angular momentum dynamics of gluons accompanying colored particles (physics of gauge links) probe interplay pert. and non pert. phenomena (kt matching) distribution of sea quarks and gluons at small kt largely unknown Summary by D. Hasch provide 1+2 image of the nucleon indicate large orbital momentum; give access to the total angular momentum (GPD E) parton correlations in nucleon wf chiral physics at large b T distributions for sea quarks and gluons are largely unknown important for pp and pa phenomenology (info on bt dependence) No model independent connection between TMDs and GPDs are known, but connected at the fundamental level via Wigner W(x,kT,bT) 6

7 A road towards sea quark and gluon imaging via GPDs at EIC (from presentations and discussions during the program) Golden measurements: DVCS, exclusive production of J\Psi, rho and phi mesons DVCS MC simulations talk by S. Fazio; F. Sabatie (to be done) using models/parameterizations of GPDs talks by D. Müller; P. Kroll Full extraction of GPDs H, E, H~ taking advantage of high accuracy, wide Q2 and L and T beam polarization EIC data talks by D. Müller, M. Burkardt; evaluation of moments of GPDs and Ji's spin sum rule, talk by M. Diehl Detector requirements: exclusivity and high resolution in t > Roman pots wide coverage in x,q2,t and lumi for multidim. binning talks by E. Aschenauer; S. Fazio Extraction image in b space on the cross over line talks by G. Miller; M. Diehl 7

8 Direct t measurement at EIC But is an indirect measurement of t really an issue for EIC? We ll get roman pots in the forward region at EIC! Silicon micro strips resolution: 0.5% for PL ; 5 MeV for PT L = pb 1 55 events (DVCS + BH) EIC lumi for erhic: * Ep/325 cm 2s 1 assuming 50% operations efficiency one week corresponds to: L(1 w)= 0.5 * (s in a week) * (1.4x1034 cm 2s 1) = 4*1039 cm 2 = 4000pb 1 + Roman Pots ~ 8000 events/week!! assuming the same acceptance ad LPS (~2%) Calculations are absolutely not rigorous! But give an idea Nov. 9, 2010 S. Fazio: INT workshop, Univ. of Washington, Seattle talk by S. Fazio8

9 t vs proton scattering angle t=(p4 p2)2 = 2[(mpin.mpout) (EinEout pzinpzout)] t=(p3 p1)2 = mρ2 Q2 2(Eγ*Eρ pxγ*pxρ pyγ*pyρ pzγ*pzρ) 4 GeV el x 50 GeV prot very strong correlation between t and recoiling proton angle Roman pots need to be very well integrated resolution on t! 4 x x Nov. 9, 2010 S. Fazio: INT workshop, Univ. of talk by S. Fazio Washington, Seattle 9

10 Can we detect exclusive protons lets see acceptance now beam angular spread 0.1mrad at IR Dipole +/ 10 mrad; geometric acceptance: +/ 11.5 cm Quads +/ 3 mrad acceptance; geometric acceptance: < 1.5cm Proton beam: p z> 0.9pz lets assume pz = pbeam maximal pt 100 GeV: ptmax < 1 GeV 50 GeV: ptmax < 0.8 GeV minimal pt assume 10σ distance of roman pot to beam 100 GeV: ptmin ~ 100 MeV 50 GeV: ptmin ~ 50 MeV cing a r t e ray l c i t r pa full o d d to e e n v I, n a h ing t s i m pro e r o ch m u m s Protons with pt >1 GeV in main detector Look Protons with 1 GeV > pt > 0.1 GeV by Poman Pots talk by E. Aschenauer E.C. Aschenauer EIC INT Program, Seattle 2010 Week 8 10

11 t xsec (ep > γp) FFS 30 X 325 by roman pots! 1.5 < Q2 < 100 GeV < x < < y < 0.8 L = 0.54 fb 1 EIC lumi: 4 fb 30x325 Nov. 9, 2010 S. Fazio: INT workshop, Univ. of Washington, Seattle Precision enormously improved Roman pots acceptance not yet included in the simulation 11 talk by S. Fazio

12 Gluon imaging: gluon vs. singlet quark size Do singlet quarks and gluons have the same transverse distribution? Hints from HERA: Area q q Area g Dynamical models predict difference: pion cloud, constituent quark picture [Strikman, Weiss 09] No difference assumed in present pp MC generators for LHC! EIC: gluon size from J/ψ, singlet quark size from DVCS x dependence: quark vs. gluon diffusion in wave function Detailed analysis: LO NLO [Mueller et al.] Detailed differential image of nucleon s partonic structure talk by T. Horn Tanja Horn, Imaging in Exclusive Processes, INT10 3, Seattle 12

13 Gluon Imaging: Valence Gluons Transverse imaging of valence gluons through exclusive J/ψ, φ Imaging requires Full t distribution for Fourier transform Non exponential? Power like at t >1 GeV2? Electroproduction with Q2>10 GeV2: test reaction mechanism, compare different channels, control systematics Experimentally need: Recoil detection for exclusivity, wide coverage in t with high resolution Luminosity ~ 1034, electroproduction, high t Hyde, Weiss 09 First gluon images of the nucleon at large x! Tanja Horn, Imaging in Exclusive Processes, INT10 3, Seattle talk by T. Horn 13

14 Accuracy and methods of transverse imaging Measure cross section as a function of t, take square root and make Fourier In real life, cannot measure for too small and too large need to extrapolate 14

15 Accuracy and methods of transverse imaging extrapolation to large t extrapolation to small t 15 talk by M. Diehl

16 Novel method for transverse imaging Finite Range Approximation, talk by G. Miller Convenient for estimation of experimental uncertainties and finite range in Q2 Experimental uncertainty + uncertainty of series truncation (n=30) as estimate of finite range in t 16 Nucleon transverse densities (valence quarks) known very well

17 Towards reconstruction of full GPDs Main method: Take advantage of wide Q2 coverage (DGLAP evolution) Main tool: Modern flexible parameterizations of GPDs 17

18 An example of such parameterization, talk by D. Muller LO, NLO, NNLO parameterization for sea quark and gluon and valence quark GPDs(x,x,t) H, Htilde, E (only D term), and Etilde (only pion pole) Sea quarks and gluons in the Mellin Barns representation Valence quarks using double distribution model + dispersion relation 18

19 EIC potential for DVCS talk by D. Müller 19

20 Exclusive production of quarkonia (J\Psi and Y) to probe gluon GPDs H and E, talk by P. Kroll Photoproduction (to be extended to electroproduction) NLO calculations Non rel. model for meson wave function DD model for GPDs Asymmetry with transv. polarized proton probes gluon GPD E: 20

21 Silver (2nd tier) measurements: exclusive production of pseudoscalar mesons (pi,k) DVCS MC simulations talk by T. Horn Model calculations talks by S. Liuti; G. Goldstein; Kroll Goloskokov model Requirements: Q2 > 10 GeV2 for point like dominace more symmetric kinematics and lower energies for better angular and momentum resolution L/T separation wide kinem. coverage and highest luminosity Extraction image in b space the same as in DVCS case 21

22 Deep Exclusive recoil baryon kinematics 4 on 12 5 on 50 (Tanja Horn) Θ = 1.3 Θ = 1.3 Θ = 5 Want 0 < t < 1 GeV 10 on 50 4 on 250 Θ = on 250 Θ = 0.3 ep e'π+n δt/t ~ t/ep Wider recoil neutron distribution at lower Ep Better t resolution talk by T. Horn [Tanja Horn] Exclusive processes at x>0.01: better prospect with lower energy and more Tanja Horn, Imaging in Exclusive Processes, INT10 3, Seattle symmetric kinematics 22

23 EIC: Transverse sea quark imaging ep e'π+n New territory for collider! Spatial structure of non perturbative sea Closely related to JLab 12 GeV o Quark spin/flavor separations o Nucleon/meson structure Simulation for π+ production assuming 100 days at a luminosity of 1034 with 5 on 50 GeV (s=1000 GeV2) V. Guzey, C. Weiss: Regge model T. Horn: empirical π+ parameterization Lower and more symmetric energies essential to ensure exclusivity [Tanja Horn, Antje Bruell, Christian Weiss] Transverse spatial structure of non perturbative sea quarks! talk by T. Horn Tanja Horn, Imaging in Exclusive Processes, INT10 3, Seattle 23

24 Outlook Our main goal is the program write up. We (organizers, conveners, participants) had many useful discussions of golden experiments and worked out the course of action for next two months. Our general strategy: finalize and extend DVCS, pi, and Kaon MC simulations attempt of J/Psi and rho MC simulations assess feasibility of imaging in b space from the pseudo data estimate what is needed for full GPD experiment (flavor separation) produce image at the cross over line GPD(x,x,t) (step 1 of imaging) [from existing models and parameterizations] be brave and attempt to restore full GPD(x,xi,t) (step 2) Plans are concrete and lots of work to do in next two months! 24