What can we do with 200GeV polarized pp in 2011

GPDs What? WHY? WHERE? and the future !!E.C. Aschenauer RHIC-AGS Users Metting, June 20101How do the partons form the spin of protonsE.C. Aschenauer RHIC-AGS Users Metting, June 20102

SqDq

DG

Lg

SqLq

dq

SqDqDGLgSqLqdq

Is the proton looking like this?Helicity sum rule in IMF

total u+d+squark spinangular momentumgluonspinWhere do we standsolving the spin puzzle ?

KretzerKKPc2DISc2SIDISDuvDuDdvDdDsDgDS2062062252310.940.70-0.26-0.340.087-0.049-0.11-0.055-0.045-0.0510.310.28DSSV0.813-0.4580.036-0.115-0.0570.242-0.0840.5740.680What do we know: NLO Fit to World DataE.C. Aschenauer RHIC-AGS Users Metting, June 20103 includes all world data from DIS, SIDIS and pp Kretzer FF favor SU(3) symmetric sea, not so for KKP, DSS DS ~25-30% in all casesD. De Florian et al. arXiv:0804.0422NLO @ Q2=10 GeV2But how do we access Lq and Lg in the IMF ???3Beyond form factors and quark distributions4Generalized Parton DistributionsProton form factors, transverse charge & current densities

Structure functions,quark longitudinalmomentum & helicity distributions

X. Ji, D. Mueller, A. Radyushkin (1994-1997)Correlated quark momentum and helicity distributions in transverse space - GPDsE.C. Aschenauer RHIC-AGS Users Metting, June 2010The Hunt for Lq5E.C. Aschenauer RHIC-AGS Users Metting, June 2010

Study of hard exclusive processes allows to access a new class of PDFsGeneralized Parton Distributions

possible way to accessorbital angular momentumexclusive: all reaction products are detected missing energy (DE) and missing Mass (Mx) = 0DIS: ~0.3

Spin Sum Rule in PRF:5GPDs IntroductionE.C. Aschenauer RHIC-AGS Users Metting, June 20106How are GPDs characterized?unpolarized polarized

conserve nucleon helicity

flip nucleon helicitynot accessible in DISDVCS

quantum numbers of final state select different GPD

pseudo-scaler mesons

vector mesons

02u+d, 9g/42u-d, 3g/4fs, g+u-dJ/gp02Du+Ddh2Du-Dd Q2= 2EeEe(1-cosqe) xB = Q2/2Mn n=Ee-Ee

x+, x- long. mom. fract. t = (p-p)2 x xB/(2-xB)accessing GPDs: some caveatsE.C. Aschenauer RHIC-AGS Users Metting, June 20107

apart from cross-over trajectory (x=x) GPDs not directly accessible: deconvolution needed ! (model dependent) but only x and t accessible experimentally

x is not acessible (integrated over): GPD moments cannot be directly revealed, extrapolations t 0 are model dependent

cross sections & beam-charge asymmetry ~ Re(T DVCS )beam or target-spin asymmetries ~ Im(T DVCS )t=0q(x)x=0 q(x)7factorization of forward Compton scattering

related to total cross section via optical theorem

final-state obtained by cutting the diagram lower blob represents standard universal PDF upper blob denotes hard interaction

factorization of DVCS

exclusive cross section is square of amplitude

final-state proton has different momentum difference of long. momentum is called skewness lower blob represents generalized PDFs upper blob denotes hard interaction

inclusive vs exclusive processes

8E.C. Aschenauer RHIC-AGS Users Metting, June 2010 distinguish two kinematical regimes:

partons emitted and reabsorbedreduce to PDFs in forward limitprobes emission of mesonic d.o.f.no PDF counterpartphysics of generalized parton densities

Q2 evolution depends on x region (technically rather involved)

generalization ofDGLAP to

evolution as formeson distribution ampl.(ERBL regime) GPDs in impact parameter space = localization of partons

e.g.wheregives distribution of quarks with longitudinal momentum fraction x transverse distance b from proton centerBurkardtfind, e.g.: dyn. relation of GPD E with Sivers effect & link to spin-orbit correlations9E.C. Aschenauer RHIC-AGS Users Metting, June 201010E.C. Aschenauer RHIC-AGS Users Metting, June 2010M. Burkardt, M. Diehl 2002FT (GPD) : momentum space impact parameter space:probing partons with specified long. momentum @transverse position b T

polarized nucleon:[x=0]from lattice

GPDs in impact parameter space

d-quarku-quark10Sivers function and OAM11E.C. Aschenauer RHIC-AGS Users Metting, June 2010Anselmino et al. arXiv:0809.2677Extremely Model dependent statement:

anomalous magnetic moment:ku = +1.67kd = -2.03

xSivers fct. from fit to

M. Burkardt et al.Lattice: QCDSF collaborationlowest moment of distribution of unpol. q in transverse pol. protonand transverse pol. quarks in unpol. proton

E.C. Aschenauer RHIC-AGS Users Metting, June 2010

mp2 [GeV2] HERMES valueLHPC hep-lat/0705.4295 disconnecteddiagrams not yet included OAM can beaccessed as wellfind: Du > 0 and Lu < 0; Dd < 0 and Ld > 0 but in any quark model Lu > 0, Ld < 0sign due to strong scale evolution of Lq ? Myhrer, ThomasLu + Ld ~ 0 contribution from disconnected diagrams?if Dg ~ 0, does this leave us with gluon OAM as culprit in spin audit?note: using AdS/CFT nucleon spin comes entirely from OAM Hatta, Ueda, Xiao arXiv:0905.24931st moments can be computed on the lattice

12manifest gauge invariant local operatorscontain interactions interpretation ?Lq+ Dq/2, Jg GPDs (DVCS)intuitive; partonic interpretationDg, L0q,g local only in A+= 0 gaugehow to determine L0q,g experimentally ?

JiJaffe, Manohar;Bashinsky, Jaffeambiguities arise when decomposing proton spin in gauge theories reshuffling of ang. momentumbetween matter and gauge degreesonly DS unchanged lattice results for Lq are for Jis sum rule and cannot be mixed with Dg num. difference between Lq and Lq can be sizable Burkardt, BC arXiv:0812.1605 latest twist:3rd decomposition: like Jaffe, Manohar but w/ manifest gauge inv. operatorsphysical interpretation? requires new def. of PDFs relation to experiment? Chen, Lu, Sun, Wang, Goldman arXiv:0806.3166; 0904.0321complication: different spin sum rules

E.C. Aschenauer RHIC-AGS Users Metting, June 201013LqLgDSDGLqJgDS

photoproduction of VM at HERAsoft interactionW described by Regge theoryhard interactionW governed by small x evolutionof gluon distributionexclusive processes: from soft to hard

14E.C. Aschenauer RHIC-AGS Users Metting, June 2010W & t dependences: probe transition from soft hard regime

VM production @ small x

rfJ/YUs ~ Wd steep energy dependence of s in presence of the hard scales ~ e-b|t|

universality of b-slope parameter: point-like configurations dominate 15E.C. Aschenauer RHIC-AGS Users Metting, June 20101516E.C. Aschenauer RHIC-AGS Users Metting, June 2010HERMES / JLAB kinematics: BH >> DVCSDeeply Virtual Compton Scattering: DVCStwo experimentally undistinguishable processes:DVCSBethe-Heitler (BH)

p + D

isolate BH-DVCS interference term non-zero azimuthal asymmetries

most clean channel for interpretation in terms of GPDs

can measure DVCS cross section and I1617E.C. Aschenauer RHIC-AGS Users Metting, June 2010DsUT ~ sinfIm{k(H - E) + }DsC ~ cosf Re{ H + xH + }~DsLU ~ sinfIm{H + xH + kE}~DsUL ~ sinfIm{H + xH + }~ polarization observables: DsUTbeam target kinematically suppressedH HH, E~ different charges: e+ e- (only @HERA!):HDVCS ASYMMETRIESx = xB/(2-xB ) k = t/4M2

17Exclusivity: How is it constrainedE.C. Aschenauer RHIC-AGS Users Metting, June 201018missing mass (energy) technique background estimated by MC

MCassociated BHBethe-Heitler+ data Hermes & H1 and Zeusfor most of the datano recoil detectionet(Q2)egL*x+ x- H, H, E, E (x,,t)~~gppe+/e-

27.5 GeVPb=55%

1819E.C. Aschenauer RHIC-AGS Users Metting, June 2010HERMES: combined analysis of charge & polarization dependent data separation of interference term + DVCS2DVCS: Hydrogen Target

Beam Charge Asymmetry

higher twisthigher twist

Beam Spin Asymmetry

DVCS1920E.C. Aschenauer RHIC-AGS Users Metting, June 2010observables sensitive to E:(Jq input parameter in ansatz for E) DVCS AUT : HERMES nDVCS ALU : Hall AFirst model dependent attempt to constrain Jq

Hermes DVCS-TTSA [arXiv: 0802.2499]:VGG

Hall A nDVCS-BSA (PRL99 (2007)):x=0.36 and Q2=1.9GeV2 Neutron obtained combining deuterium and proton

F1 small u & d cancel in

Model dependent20AHLT: Ahmad, Honkanen, Liuti, Taneja PRD75(2007)DVCS: Deuterium TargetE.C. Aschenauer RHIC-AGS Users Metting, June 201021

Latest Measurements from JLabE.C. Aschenauer RHIC-AGS Users Metting, June 201022DVCS-BSA:

arXiv: 0711.4805x=0.249Q2=1.95x=0.249Q2=1.95

VGG VGG+twist3 Lagetmore data on:ALU, ALL, cross section @ 6GeV

12 GeV:a lot to come with Q2max ~ 13 GeV, t>0.1 GeV x>0.2 DVCS from &

E.C. Aschenauer RHIC-AGS Users Metting, June 201023

Zeus: ArXiv: 0812.2517

H1: PLB 681 (2009) 391time for crude models is over use data to determine GPDs from global QCD fits

first attempt to extract H(x,x) from DVCS data: Mueller, Kumericki, Passek-Kumericki so far, very good fits but only the beginning; will be an ongoing effort for years need to incorporate useful information from meson production (gluon GPD!) but theory considerably more difficult and less maturetowards a global analysis of GPDs

E.C. Aschenauer RHIC-AGS Users Metting, June 201024

Hermes BCACLAS BSAHall AHall Adifferent GPD parametrisationsMore Results from MKKE.C. Aschenauer RHIC-AGS Users Metting, June 201025arXiv: 0904.0458

t=0t=-0.3

Other Fits: M. Guidal PLB 689 (2010) 156M. Guidal & H. Moutarde EPJ A42 (2009) 71H. Moutarde PRD 79 (2009) 094021but all to limited data sets Charge and Beam Spin Asymmetry Heavy TargetsE.C. Aschenauer RHIC-AGS Users Metting, June 201026Beam Charge Asymmetry

Beam Spin Asymmetry Why nuclear DVCS: How does the nuclear medium modify parton-parton correlations? How do nucleon properties change in the nuclear medium? Enhanced generalized EMC effect, rise of tDVCS with A? arXiv: 0911.0091

eRHIC ScopeE.C. Aschenauer RHIC-AGS Users Metting, June 2010e-e+pUnpolarized andpolarized leptons4-20 (30) GeVPolarized light ions (He3) 215 GeV/uLight ions (d,Si,Cu)Heavy ions (Au,U)50-100 (130) GeV/uPolarized protons50-250 (325) GeVElectron acceleratorRHIC70% e- beam polarization goalpolarized positrons?Center mass energy range: s=28-200 GeV; L~100-1000xHeralongitudinal and transverse polarisation for p/He-3 possiblee-

Mission: Studying the Physics of Strong Color Fields2727

eSTARePHENIXThe latest design of eRHICE.C. Aschenauer RHIC-AGS Users Metting, June 2010100m |--------|6 pass 2.5 GeV ERLCoherent e-cooler22.5 GeV 17.5GeV 12.5 GeV 7.5 GeV Common vacuum chamber27.5 GeV 2.5 GeV Beam-dumpPolarized e-guneRHIC detector25 GeV 20 GeV 15 GeV 10 GeV Common vacuum chamber30 GeV 5 GeV 0.1 GeV The mostcost effective designRHIC: 325 GeV p or 130 GeV/u AueRHIC staging all-in tunnel28A detector integrated into IRE.C. Aschenauer RHIC-AGS Users Metting, June 2010

ZDCFPD Dipoles needed to have good forward momentum resolution Solenoid no magnetic field @ r ~ 0 DIRC, RICH hadron identification p, K, p high-threshold Cerenkov fast trigger for scattered lepton radiation length very critical low lepton energiesFED

a lot of space for polarimetryand luminositymeasurements

29

eRHIC Detector in Geant-3E.C. Aschenauer RHIC-AGS Users Metting, June 2010 DIRC: not shown because of cut; modeled following Babar no hadronic calorimeter in barrel yet investigate ILC technology to combine mID with HCAL

central trackingala BaBarSilicon Stripdetectorala ZeusEM-CalorimeterLeadGlasHigh ThresholdCerenkovfast trigger on ee/h separationDual-Radiator RICHala HERMESDrift Chambers ala HERMES FDCHadronicCalorimeter30Can we detect DVCS-protons and Au break up pE.C. Aschenauer RHIC-AGS Users Metting, June 2010 track the protons through solenoid, quads and dipole with hector

proton track Dp=10%

proton track Dp=20%

proton track Dp=40%

Equivalent to fragmenting protonsfrom Au in Au optics (197/79:1 ~2.5:1)

will need roman pots as used in pp2ppDVCS protons are fine, need more optimization for break-up protons31DVCS @ eRHIC32 at low x dominated by gluon contributions Need wide x and Q2 range to extract GPDs Need sufficient luminosity to bin in multi-dimensions

E.C. Aschenauer RHIC-AGS Users Metting, June 2010

SummaryE.C. Aschenauer RHIC-AGS Users Metting, June 201033

EIC many avenues for further important measurements and theoretical developmentswe have just explored the tip of the icebergyou are hereDutot, DdtotLq,gDsDgspin sum ruleKnowledge aboutGluons in p /ACome and join us

The BNL EIC Taskforce

E.C. Aschenauer RHIC-AGS Users Metting, June 201034BACKUPSummaryE.C. Aschenauer RHIC-AGS Users Metting, June 201035

Dq

DG

Lg

Lq

dq

DqDGLgLqdq

300 pb-1DIS&pp

x

More insights to the proton - TMDsE.C. Aschenauer RHIC-AGS Users Metting, June 2010Unpolarized distribution function q(x), G(x)Helicity distribution function Dq(x), DG(x)Transversity distribution function dq(x)

Correlation between and

Correlation between and

Correlation between and

Sivers distribution function

Boer-Mulders distribution function

Single Spin Asymmetries beyond collinear pictureExplore spin orbit correlationspeculiarities of f^1T

chiral even nave T-odd DFrelated to parton orbital angular momentumviolates nave universality of PDFsQCD-prediction: f^1T,DY = -f^1T,DIS 36: What can we learn about the nucleon spinE.C. Aschenauer RHIC-AGS Users Metting, June 201037

xinteresting questions at small x charm contribution to g1 any deviations from DGLAP behavior? precision study of Bjorken sum rule

(rare example of a well understood fundamental quantity in QCD)

positive Dgtranslates into

Anticipated precision for one beam energy combinationIntegrated Lumi: 5fb-1 ~ 1 week data taking Dg(x) very small at medium x best fit has a node at x ~ 0.1 huge uncertainties at small x small-x behavior still completey unconstrainedThe Gluon Polarization (HP12)E.C. Aschenauer RHIC-AGS Users Metting, June 2010

xRHICrange0.05< x < 0.2 small-x0.001 < x < 0.05large-xx > 0.2

Dg(x) small !?

38

de Florian, Sassot, Stratmann, and Vogelsang PRL101 072001

Deeply Virtual Compton Scattering and GPDset(Q2)egL*x+ x- H, H, E, E (x,,t)~~gppHandbag factorization validin the Bjorken regime:high Q2 , (fixed xB) Q2= - (e-e)2 xB = Q2/2Mn n=Ee-Ee

x+, x- longitudinal momentum fractions t = (p-p)2 x xB/(2-xB)x]0,x+x),(Exq21Hxdxq- JG = =21Jq[11-)0,,(Quark angular momentum (Jis sum rule)X. Ji, Phy.Rev.Lett.78,610(1997) GPDs:Correlation betweenquark distributions both in momentum and coordinate space39E.C. Aschenauer RHIC-AGS Users Metting, June 201039Hard exclusive meson production and GPDs4 Generalized Parton Distributions (GPDs) H H conserve nucleon helicityE E flip nucleon helicityVector mesons (r, w, f)Pseudoscalar mesons (p, h) ~ ~02u+d2u-d+u-dquark flavor decomposition accessible via meson productionx+ x- t, , (Q2)eegL*Factorization proven only forlongitudinally polarized virtual photonsand valid at high Q2 and small tp02Du+Ddh2Du-DdH, H, E, E (x,,t)~~(p0)~ | dx H(x,x,t) |2~40E.C. Aschenauer RHIC-AGS Users Metting, June 2010

t-slopes

b decreasing as a function of xb Valence (high x) quarks at the center (small b) Sea (small x) quarks at the perifery (high b)IF GPD formalism applies!!y

xz

Guidal, Polyakov, Radyushkin, Vanderhaeghen (2005) b(fm)x41E.C. Aschenauer RHIC-AGS Users Metting, June 2010Questions about QCDConfinement of color, or why are there no free quarks and gluons at a long distance? A very hard question to answerWhat is the internal landscape of the nucleons? What is the nature of the spin of the nucleon? What is the three-dimensional spatial landscape of nucleons?Need probes to see and locate the quarks and gluons, without disturbing them or interfering with their dynamics?What governs the transition of quarks and gluons into pions and nucleonsWhat is the role of gluons and gluon self-interactions in nucleons and nuclei?What is the physics behind the QCD mass scale?

E.C. Aschenauer RHIC-AGS Users Metting, June 2010 It represents the difference between QED and QCD Cant see it directly, but, it is behind the answers to all these questionsThe key to the solutionThe Gluon42Transversity and Sivers, what do we knowE.C. Aschenauer RHIC-AGS Users Metting, June 2010Anselmino et al. arXiv:0809.2677

xTransversity dq from fit to

43

Sivers fct from fit to

Q2=2.4 GeV2Fit to

SIDIS and e+e-Lattice: P. Haegler et al.lowest moment of distribution of unpol. q in transverse pol. proton

ANL ZGSs=4.9 GeV BNL AGSs=6.6 GeV FNAL s=19.4 GeV Big single spin asymmetries in pp !!

Naive pQCD (in a collinear picture) predicts AN ~ asmq/sqrt(s) ~ 0

What is the underlying process?Do they survive at high s?Relation to SIDIS? HP13Exclusive p+ production44E.C. Aschenauer RHIC-AGS Users Metting, June 2010

[PLB659(2008)]GPD model for sL: VGGLOLO+power corrections NLO corrections moderate