Contalbrigo Marco INFN Ferrara Workshop on Partonic Transverse Momentum in Hadrons: Quark Spin-Orbit Correlations and Quark-Gluon Interactions March 12-13, 2010 Duke University

PDFs f p u (x),… Form Factors F 1p u (t),F 2p u (t ).. TMD PDFs: f p u (x,k T ),… d2kTd2kT  =0,t=0 dx W p u (x,k T,r) “Mother” Wigner distributions d3rd3r d2kTd2kT Quantum Phase-Space Distributions of Quarks Measure momentum transfer to target Direct info about spatial distributions Measure momentum transfer to quark Direct info about momentum distributions GPD Probability to find a quark u in a nucleon P with a certain polarization in a position r and momentum k (FT) GPDs: H p u (x, ,t), … 2 Duke Workshop 2010 M. Contalbrigo

3 Duke Workshop 2010 ┴┴ ┴ ┴ ┴ g 1L h1h1 Fragmentation Functions (FF) Distribution Functions (DF) M. Contalbrigo Interference between wave functions with different angular momenta: contains infos about parton orbital angular momenta Testing QCD at the amplitude level i.e. Sivers: spin-orbit correlations with same matrix element of anomaluos magnetic moment, and GPD E Off-diagonal elements are important objects: 3D description in momentum space PRD 78 (2008)

┴┴ ┴ ┴ ┴ Distribution Functions (DF) anti-green remnant green quark GPD EGPD E T SIVERS Quark orbital angular momentum BOER-MULDERS Spin orbit effect M. Contalbrigo4 Duke Workshop 2010 Off-diagonal elements: interference of wave- function components with different orbital momenta

e+e- annihilation: FFs Not zero Collins & IFF Drell-Yan: PDFs Not zero Boer-Mulders SIDIS: PDFs x FFs Not zero Sivers Not zero h 1, Collins & IFF Non zero Boer-Mulders ……. pp reactions: PDFs (x FFs) Strong SSA at large x F ISI FSI ISI x FSI FSI RICH CLEAN Hadron probe Lepton probe M. Contalbrigo5 Duke Workshop 2010

Distribution Functions (DF) Correlation Functions and SIDIS N/qULT U Fragmentation Functions (FF) D q h (z) q(x) Rich phenomenology but rather involved observables Target type and hadron ID provide flavor tagging !! constrain valence and sea disentangle distribution and fragmentation functions Muldidimensional analysis resolves kinematic correlations !! M. Contalbrigo6 Duke Workshop 2010

CollinsSivers Boer- Mulders M. Contalbrigo7 Several observables already measured… with matches and mismatches Duke Workshop 2010

8 Executive summary Crucial: completeness flavor tagging and five-fold differential extraction in all variables (x,z,Q 2,P T ) to have all dependencies resolved TMDs are a new class of phenomena providing novel insights into the rich nuclear structure Limited knowledge on transverse momentum dependences Flavor decomposition often missing Evolution properties to be defined Role of the higher twist to be quantified Universality Fundamental test of QCD Still incomplete phenomenology is asking for new inputs Non-zero results from DIS experiments provide promises but also open questions Contalbrigo Marco CLAS12 European Workshop 26 February 2009 M. Contalbrigo8 Duke Workshop 2010

M. Contalbrigo9 Duke Workshop 2010 Reccomendation 1 We recommend the completion of the 12 GeV Upgrade at Jefferson Lab.  It will enable three-dimensional imaging of the nucleon, revealing hidden aspects of its internal dynamics.  It will complete our understanding of the transition between the hadronic and the quark/gluon descriptions of nuclei. 

M. Contalbrigo10 Duke Workshop 2010

Limit defined by luminosity Different Q2 for same x range EIC Resonance region M. Contalbrigo11 Complementary experiments Duke Workshop 2010

6 GeV CEBAF CHL-2 Upgrade magnets and power supplies 12 GeV CEBAF Enhance equipment in existing halls add Hall D (and beam line) : Construction (funded at 99%) May GeV Accelerator Shutdown starts May 2013 Accelerator Commissioning starts October 2013 Hall Commissioning starts Pre-Ops (beam commissioning) M. Contalbrigo12 Duke Workshop 2010

13 CLAS12: experimental set-up Polarized beam multi-purpose detector for fixed target electron scattering experiments Pion and kaon, …. SSA broad kinematical range large luminosity H and D targets Contalbrigo Marco CLAS12 European Workshop 26 February 2009 Q 2 >1GeV 2 W 2 >4 GeV 2 y<0.85 M X >2GeV Large kinematic ranges accessible with CLAS12 are important for separation of Valence region Higher Twist contributions (Q 2 ) Perturbative regime (P T ≥ 1)

LTCC FTOF PCAL EC HTCC Lumi = cm -2 s -1 High beam polarization 80% High target polarization 85% NH 3 (30 days) ND 3 (50 days) HD-ice target !!! Replace 2 sectors of LTCC with a proximity RICH detector to identify Kaons approved by JLab PAC34 charged particle radiator drift electrode Proximity gap CLAS12 Wide detector acceptance allows current & target fragmentation measur. Photocathode M. Contalbrigo14 Duke Workshop 2010

Pros 1.Small field (∫Bdl~ Tm) 2.Small dilution (fraction of events from polarized material) 3.Less radiation length 4.Less nuclear background (no nuclear attenuation) 5.Wider acceptance much better FOM, especially for deuteron Cons 1.HD target is highly complex and there is a need for redundancy due to the very long polarizing times (months). 2.Need to demonstrate that the target can remain polarized for long periods with an electron beam with currents of order of 1-2 nA 3.Additional shielding of Moller electrons necessary (use minitorus) Heat extraction is accomplished with thin aluminum wires running through the target (can operate at T~ mK) HD-Ice target at ~2nA NH3 at ~5 nA HD-Ice target vs std nuclear targets CLAS transversely polarized HD-Ice target M. Contalbrigo15 Duke Workshop 2010 P= 95 % H, 70 % D ???

16 Duke Workshop 2010 M. Contalbrigo ┴┴ ┴ ┴ ┴ g 1L h1h1 Distribution Functions (DF)

Boer-Mulders CLAS12 Band: Phys Rev D Boer-Mulders from DY data Collins from chiral limit Line: Phys Rev D Boer-Mulders from Sivers Collins from e+e- data 56 days at L=1x10 35 cm -2 s -1 kaon Boer-Mulders: excellent precision vs model uncertainties M. Contalbrigo17 Duke Workshop 2010

High statistics CLAS12 M. Contalbrigo18 PT-dependence of azimuthal moments allows studies of transition from non-perturbative to perturbative description (Unified theory by Ji et al, P T matches and mismatches by Bacchetta et al). In the perturbative limit 1/P T 2 behavior expected Perturbative region Non-perturbative TMD Duke Workshop 2010

Beam CLAS12 M. Contalbrigo19 In the perturbative limit 1/P T behavior expected A LU ~ 1/Q (Twist-3) Measurements of kinematic (x,Q 2,z,P T ) will probe HT distribution functions Duke Workshop 2010

20 Duke Workshop 2010 M. Contalbrigo ┴┴ ┴ ┴ ┴ g 1L h1h1 Distribution Functions (DF)

Longitudinal Target CLAS12 proton 11 GeV with sec -1 cm -2 ) M. Contalbrigo21 Helicity dependence of k T - distribution of quarks Duke Workshop 2010 M.Anselmino et al hep-ph/ Phys.Rev.D74:074015,2006  0 2 =0.25GeV 2  D 2 =0.2GeV 2 Constituent quark model (Pasquini et al).

Longitudinal Target CLAS12 11 GeV NH 3 and ND 3 target with sec -1 cm -2 M. Contalbrigo22 Flavor sensitivity thanks to  deuteron/proton target  pion/kaon detection Duke Workshop 2010 proton 11 GeV HD-ice target proton

deuteron Longitudinal Target CLAS12 M. Contalbrigo23 Curves, χQSM, Efremov et al, Czech J Phys 55 (2005) A189 Transversely polarized quarks in long polarized nucleon Leading twist, sensitive to spin-orbit correlations Duke Workshop 2010 Curves colored: CQM, Pasquini et al, PRD78 (2008) black: Avakian et al, PRD77 (2008) GeV NH 3 and ND 3 target with sec -1 cm -2

Simple string fragmentation (Artru model) Sub-leading pion opposite to leading (into page) L=1  production may produce an opposite sign A UT Leading  opposite to leading  (into page)  hep-ph/ Fraction of  in e  X% left from e  X asm 20% 40% ~75% ~50% Fraction of direct kaons may be significantly higher than the fraction of direct pions. LUND-MC M. Contalbrigo24 Duke Workshop 2010

25 Duke Workshop 2010 M. Contalbrigo ┴┴ ┴ ┴ ┴ g 1L h1h1 Distribution Functions (DF)

 UT ~ Collins Study A UT at large x (valence) where models are mostly unconstrined Collins CLAS12 26 Duke Workshop 2010 M. Contalbrigo 11 GeV NH 3 target (P=85%, f=0.14) L= sec -1 cm -2 Curves fom A.V. Efremov et al PRD76:094025,2006 Tensor charge

unpolarized beam, transv. target  Exciting relation: (in bag & spectator model) Avakian et al., PRD78, non spherical shape of the nucleon u quark k  =0 k  =2.0 GeV SS B. Pasquini et al. arXiv: kk CLAS12 27 Duke Workshop 2010 M. Contalbrigo 11 GeV NH 3 target (P=85%, f=0.14) L= sec -1 cm -2

unpolarized beam, transverse target S. ArnoldS. Arnold et al arXiv: M. AnselminoM. Anselmino et al arXiv: Eur.Phys.J.A39:89-100,2009 Sivers CLAS12 28 Duke Workshop 2010 M. Contalbrigo 11 GeV NH 3 target (P=85%, f=0.14) L= sec -1 cm -2

Proton form factors, transverse charge & current densities D. Mueller, X. Ji, A. Radyushkin, A. Belitsky, … M. Burkardt, … Interpretation in impact parameter space Structure functions, quark longitudinal momentum & helicity distributions How is the proton charge density related to its quark momentum distribution? ? Correlated quark momentum and helicity distributions in transverse space - GPDs 29 Duke Workshop 2010 M. Contalbrigo

CLAS12 - DVCS/BH Target Asymmetry  Asymmetries highly sensitive to the u-quark contributions to the proton spin. Transverse polarized target e p ep   ~ sin  Im{k 1 (F 2 H – F 1 E ) +…}d  Q 2 =2.2 GeV 2, x B = 0.25, -t = 0.5GeV 2 E = 11 GeV Sample kinematics A UTx Target polarization in the scattering plane A UTy Target polarization perpendicular to the scattering plane 30 Duke Workshop 2010 M. Contalbrigo 11 GeV NH 3 target (P=85%, f=0.14) L= sec -1 cm -2

Exclusive   production on transverse target 2  (Im(AB*)) T  UT  A ~ 2H u + H d B ~ 2E u + E d 00 K. Goeke, M.V. Polyakov, M. Vanderhaeghen, 2001 Q 2 =5 GeV 2 E u, E d allow to map the orbital motion of quarks. 00 B A ~ H u - H d B ~ E u - E d ++ 31 Duke Workshop 2010 M. Contalbrigo 11 GeV NH 3 target (P=85%, f=0.14) L= sec -1 cm -2