Summary of subtopic “Imaging QCD Matter”: Generalized · PDF fileGeneralized...
Transcript of Summary of subtopic “Imaging QCD Matter”: Generalized · PDF fileGeneralized...
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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
Workshop on the Science case of an EICNov 18, 2010, Seattle, INT
On behalf of scientific coordinators: F. Sabatie and M. Burkardt
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Outline
● Agenda overview
● A road towards sea quark and gluon imaging at an EIC
● Golden GPD measurements
● Outlook
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Agenda overview
● Weeks 8 and 9 were dedicated to “Imaging QCD Matter”, which for practical purposes means transverse momentum dependent distributions (TMDs) and semiinclusive 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:https://wiki.bnl.gov/eic/index.php/Nucleon_Spin_and_Imaging
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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: http://www.int.washington.edu/talks/WorkShops/int_10_3/
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Agenda overview: discussed topics of the GPD part
1) Imaging in the bspace:● 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”● G. Goldstein, “Limits on spin dependent GPDs from theory and experiment”
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Imaging QCD Matter (3D structure of the nucleon): digest of ideas discussed during the program
Distributions in (x,kT):TMDs
● spinorbit correlations (kT vs. polariz.)● indicate orbital angular momentum● dynamics of gluons accompanying colored particles (physics of gauge links)● probe interplay pert. and nonpert. phenomena (kT matching)● distribution of sea quarks and gluons at small kT largely unknown
Distributions in (x,bT)GPDs and dipole amplitudes
● 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 bT● distributions for sea quarks and gluons are largely unknown● important for pp and pA phenomenology (info on bT dependence)
No modelindependent connection between TMDs and GPDs are known, but connected at the fundamental level via Wigner W(x,kT,bT)
Summary by D. Hasch
talks by C. Weiss;M. Diehl; M. Burkardt
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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 GPDstalks by D. Müller; P. Kroll
Detector requirements:● exclusivity and high resolution in t > Roman pots ● wide coverage in x,Q2,t and lumi for multidim. binningtalks by E. Aschenauer; S. Fazio
Extraction image in bspace on the crossover linetalks by G. Miller; M. Diehl
Full extraction of GPDs H, E, H~ taking advantage of highaccuracy, wideQ2 and L and T beampolarization EIC datatalks by D. Müller, M. Burkardt;evaluation of moments of GPDs and Ji's spin sum rule, talk by M. Diehl
Direct t measurement at EICBut… is an indirect measurement of t really an issue for EIC?
We’ll get roman pots in the forward region at EIC!
L = 27.77 pb1
55 events (DVCS + BH)
for eRHIC: 1.4 1034* Ep/325 cm2s1 assuming 50% operations efficiency one week corresponds to:L(1 w)= 0.5 * 604800(s in a week) * (1.4x1034 cm2s1) = 4*1039 cm2 = 4000pb1
+ Roman Pots ~ 8000 events/week !! assuming the same acceptance ad LPS (~2%)Calculations are absolutely not rigorous! But give an idea…
Silicon microstripsresolution: 0.5% for PL ; 5 MeV for PT
Nov. 9, 2010 8S. Fazio: INTworkshop, Univ. of
Washington, Seattle
EIC lumi
talk by S. Fazio
t vs proton scattering angle
Nov. 9, 2010 S. Fazio: INTworkshop, Univ. of Washington, Seattle
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4 GeV el x 50 GeV prot 4 x 100
4 x 250
very strong correlation between t and “recoiling” proton angle Roman pots need to be very well integrated resolution on t!
t=(p4p2)2 = 2[(mpin.mp
out)(EinEout pzinpz
out)]
t=(p3–p1)2 = mρ2Q2 2(E *γ Eρpx
*γ pxρpy
*γ pyρpz
*γ pzρ)
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talk by S. Fazio
Can we detect “exclusive” protonsCan we detect “exclusive” protons
E.C. AschenauerE.C. Aschenauer EIC INT Program, Seattle 2010 Week 8EIC INT Program, Seattle 2010 Week 8 1010
lets see acceptance nowlets see acceptance now beam angular spread 0.1mrad at IRbeam angular spread 0.1mrad at IR Dipole +/ 10 mrad; geometric acceptance: +/ 11.5 cm Dipole +/ 10 mrad; geometric acceptance: +/ 11.5 cm Quads +/ 3 mrad acceptance; geometric acceptance: < 1.5cm Quads +/ 3 mrad acceptance; geometric acceptance: < 1.5cm Protonbeam: p’Protonbeam: p’zz> 0.9p> 0.9pz z lets assume p lets assume pzz = p = pbeambeam
maximal pmaximal ptt
100 GeV: p100 GeV: pttmaxmax < 1 GeV < 1 GeV
50 GeV: p50 GeV: pttmaxmax < 0.8 GeV < 0.8 GeV
minimal pminimal ptt assume 10 assume 10σσ distance of roman pot to beam distance of roman pot to beam 100 GeV: p100 GeV: ptt
minmin ~ 100 MeV ~ 100 MeV 50 GeV: p50 GeV: ptt
minmin ~ 50 MeV ~ 50 MeV
Looks much more promising than vI, need to do full particle ray tracing
Looks much more promising than vI, need to do full particle ray tracing
talk by E. Aschenauer
Protons with pT >1 GeV in main detectorProtons with 1 GeV > pT > 0.1 GeV by Poman Pots
Nov. 9, 2010S. Fazio: INTworkshop, Univ. of
Washington, Seattle11
txsec (ep > γp)FFS 30 X 325
by roman pots!
L = 0.54 fb1
EIC lumi: 4 fb1/month @ 30x325 • Precision enormously improved
• Roman pots acceptance not yet included in the simulation
• 1.5 < Q2 < 100 GeV2
• 104 < x < 0.1• 0.01 < y < 0.8
talk by S. Fazio
Gluon imaging: gluon vs. singlet quark size
Tanja Horn, Imaging in Exclusive Processes, INT103, Seattle
Detailed differential image of nucleon’s partonic structure
• EIC: gluon size from J/ψ, singlet quark size from DVCS
– xdependence: quark vs. gluon diffusion in wave function
– Detailed analysis: LO NLO [Mueller et al.]
• Do singlet quarks and gluons have the same transverse distribution?
– Hints from HERA:
– Dynamical models predict difference: pion cloud, constituent quark picture [Strikman, Weiss 09]
– No difference assumed in present pp MC generators for LHC!
Area qq Area g
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talk by T. Horn
Gluon Imaging: Valence Gluons
• Imaging requires– Full tdistribution for Fourier transform– Nonexponential? Powerlike at |t|>1 GeV2?– Electroproduction with Q2>10 GeV2: test
reaction mechanism, compare different channels, control systematics
Tanja Horn, Imaging in Exclusive Processes, INT103, Seattle
• Transverse imaging of valence gluons through exclusive J/ψ, φ
• Experimentally need:– Recoil detection for exclusivity, wide
coverage in t with high resolution– Luminosity ~ 1034, electroproduction, hight
First gluon images of the nucleon at large x!Hyde, Weiss ‘09
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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
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Accuracy and methods of transverse imaging
extrapolation to large t
extrapolation to small t
talk by M. Diehl
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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
+Nucleon transverse densities (valence quarks) known very well
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Towards reconstruction of full GPDs
Main method: Take advantage of wide Q2 coverage (DGLAP evolution)
Main tool:Modern flexible parameterizations of GPDs
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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 Dterm), and Etilde (only pion pole)● Sea quarks and gluons in the MellinBarns representation● Valence quarks using double distribution model + dispersion relation
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EIC potential for DVCS
talk by D. Müller
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Exclusive production of quarkonia (J\Psi and Y) to probe gluon GPDs H and E, talk by P. Kroll
● NLO calculations● Nonrel. model for meson wave function● DD model for GPDs
Photoproduction(to be extended to electroproduction)
Asymmetry with transv.polarized protonprobes gluon GPD E:
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“Silver” (2ndtier) measurements:exclusive production of pseudoscalar mesons (pi,K)
DVCS MC simulations talk by T. Horn
Requirements:● Q2 > 10 GeV2 for pointlike 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 bspace the same as in DVCS case
Model calculationstalks by S. Liuti; G. Goldstein;KrollGoloskokov model
∆Θ = 5 ∆Θ = 1.3 ∆Θ = 1.3
∆Θ = 0.3 ∆Θ = 0.3 δt/t ~ t/Ep
Wider recoil neutron distribution at lower Ep
Better t resolution
(Tanja Horn)
Want 0 < t < 1 GeV
4 on 12 5 on 50 10 on 50
4 on 250 10 on 250
Deep Exclusive – recoil baryon kinematics
[Tanja Horn]
ep → e'π+n
Tanja Horn, Imaging in Exclusive Processes, INT103, SeattleExclusive processes at x>0.01: better prospect with lowerenergy and more
symmetric kinematics 22
talk by T. Horn
[Tanja Horn, Antje Bruell, Christian Weiss]
• New territory for collider!
• Spatial structure of nonperturbative sea– Closely related to JLab 12 GeV
o Quark spin/flavor separationso 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
Tanja Horn, Imaging in Exclusive Processes, INT103, Seattle
EIC: Transverse sea quark imagingEIC: Transverse sea quark imaging
ep → e'π+n
• Lower and more symmetric energies essential to ensure exclusivity
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Transverse spatial structure of nonperturbative sea quarks!
talk by T. Horn
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Outlook
● Our main goal is the program writeup.
● 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 bspace from the pseudodata ● estimate what is needed for “full GPD experiment” (flavor separation)● produce image at the crossover 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!