Transverse Spin Physics With CLAS12 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

Partonic Transverse MoMentum

Quantum Phase-Space Distributions of Quarks Wpu(x,kT,r) “Mother” Wigner distributions Probability to find a quark u in a nucleon P with a certain polarization in a position r & momentum k d3r d2kT (FT) GPD TMD PDFs: fpu(x,kT),… GPDs: Hpu(x,x,t), … d2kT dx x=0,t=0 Form Factors F1pu(t),F2pu(t ).. Measure momentum transfer to target Direct info about spatial distributions Measure momentum transfer to quark Direct info about momentum distributions pT< 2 GeV/c √s = 20 GeV xF AN PDFs fpu(x),… SSA Proton spin puzzle M. Contalbrigo Duke Workshop 2010 3

TMD correlators Distribution Functions (DF) Off-diagonal elements are important objects: Distribution Functions (DF) Interference between wave functions with different angular momenta: contains infos about parton orbital angular momenta ┴ ┴ Testing QCD at the amplitude level g1L ┴ ┴ ┴ h1 3D description in momentum space Fragmentation Functions (FF) Bacchetta, PRD78 mostra un gafico diverso, con shift positivo per gli u. Da dove viene davvero il grafico ? PRD 78 (2008) 074010 M. Contalbrigo Duke Workshop 2010 4

The 3D description of the nucleon Distribution Functions (DF) SIVERS Quark orbital angular momentum BOER-MULDERS Spin orbit effect Impact parameter space ┴ ┴ anti-green remnant green quark GPD E GPD ET+2HT ~ Deformations by ┴ ┴ ┴ 3-momentum space i.e. Sivers: spin-orbit correlations with same matrix element of anomalus magnetic moment, and GPD E M. Contalbrigo Duke Workshop 2010 5

Correlation Functions and SIDIS Distribution Functions (DF) ~ Fragmentation Functions (FF) q(x) Dqh(z) Rich phenomenology but rather involved observables Target type and hadron ID provide flavor tagging !! constrain valence and sea disentangle distribution and fragmentation functions (test factorization, HT) Multidimensional analysis resolves kinematic correlations !! M. Contalbrigo Duke Workshop 2010 6

Several observables already measured… with matches and mismatches Collins Sivers Boer- Mulders M. Contalbrigo Duke Workshop 2010 7

Executive summary TMDs are a new class of phenomena providing novel insights into the rich nuclear structure Non-zero results from DIS experiments provide promises but also open questions 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 Crucial: completeness flavor tagging and five-fold differential extraction in all variables (x,z,Q2,PT) to have all dependencies resolved Still incomplete phenomenology is asking for new inputs Contalbrigo Marco CLAS12 European Workshop 26 February 2009 M. Contalbrigo Duke Workshop 2010 8

JLAB 12

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. Contalbrigo Duke Workshop 2010 10

Upgrade magnets and power supplies add Hall D (and beam line) 6 GeV CEBAF CHL-2 Upgrade magnets and power supplies 12 GeV CEBAF Beam current 90 mA Beam polarization 85 % 2008-2014: Construction (funded at 99%) May 2012 6 GeV Accelerator Shutdown starts May 2013 Accelerator Commissioning starts October 2013 Hall Commissioning starts 2013-2015 Pre-Ops (beam commissioning) Enhance equipment in existing halls M. Contalbrigo Duke Workshop 2010 11

Your Text Here The SIDIS landscape EIC Complementary experiments Limit defined by luminosity Different Q2 for same x range Your Text Here EIC 1034 Resonance region 1032 1031 1035 Complementary experiments Matches valence M. Contalbrigo Duke Workshop 2010 12

broad kinematical range CLAS12 L~ 1035 cm-2s-1 PCAL FTOF LTCC HTCC EC SVT CTOF 5T solenoid toroid large luminosity H and D targets 10 nA electron beam 85% beam polariz broad kinematical range NH3 ND3 target 85 % polarization Pion and kaon, …. SSA Large kinematic ranges accessible with CLAS12 are important for separation of Valence region Higher Twist contributions (Q2) Perturbative regime (PT ≥ 1) multi-purpose detector for fixed target electron scattering experiments Q2>1GeV2 W2>4 GeV2 y<0.85 MX>2GeV Wide detector acceptance allows current & target fragmentation measur. Contalbrigo Marco CLAS12 European Workshop 26 February 2009 M. Contalbrigo Duke Workshop 2010 13

broad kinematical range CLAS12 L~ 1035 cm-2s-1 PCAL FTOF LTCC HTCC EC SVT CTOF 5T solenoid toroid large luminosity H and D targets 10 nA electron beam 85 % polarization broad kinematical range NH3 ND3 target 85 % polarization Pion and kaon, …. SSA Replace 2 sectors of LTCC with a proximity RICH detector to identify Kaons approved by JLab PAC34 charged particle radiator drift electrode Proximity gap Photocathode Contalbrigo Marco CLAS12 European Workshop 26 February 2009 M. Contalbrigo Duke Workshop 2010 14

TMDs with UNPOLArized targets

Distribution Functions (DF) TMD correlators ┴ g1L h1 Distribution Functions (DF) M. Contalbrigo Duke Workshop 2010 16

Unpolarized target @ CLAS12 Boer-Mulders spin-orbit effect 56 d @ 1035 s-1cm-2 LH2 LD2 targets kaon Line: Phys Rev D78 045022 Boer-Mulders from Sivers Collins from e+e- data Band: Phys Rev D78 034035 Boer-Mulders from DY data Collins from chiral limit Measurements of kinematic (x,Q2,z,PT) will probe HT distribution functions PR12-06-112 ATT: corrente tipica 10 nA, e per HD-ice 1-2 nA, polarizzazione fascio 85 % L’andamento con 1/Pt descritto da Bacchetta in PT matches Pbeam = 85 % In the perturbative limit 1/PT behavior expected ALU~ 1/Q (Twist-3) M. Contalbrigo Duke Workshop 2010 17

Unpolarized target @ CLAS12 PT-dependence of azimuthal moments allows studies of transition from non-perturbative to perturbative description (Unified theory by Ji et al, PT matches and mismatches by Bacchetta et al). In the perturbative limit 1/PT2 behavior expected Perturbative region 4<Q2<5 GeV2 Talk di Harut al PAC 30 Da dove prende Boer-Mulders ??? Non-perturbative TMD 2000h @ 1035 s-1cm-2 LH2 target M. Contalbrigo Duke Workshop 2010 18

Longitudinal Polarized TMDs with Longitudinal Polarized targets

Distribution Functions (DF) TMD correlators ┴ g1L h1 Distribution Functions (DF) M. Contalbrigo Duke Workshop 2010 20

Longitudinal Target Spin @ CLAS12 2000h @ 1035 s-1cm-2 NH3 and ND3 target Constituent quark model (Pasquini et al). proton M.Anselmino et al hep-ph/0608048 Phys.Rev.D74:074015,2006 m02=0.25GeV2 mD2=0.2GeV2 Helicity dependence of kT-distribution of quarks M. Contalbrigo Duke Workshop 2010 21

Longitudinal Target Spin @ CLAS12 Transversely polarized quarks in long polarized nucleon Leading twist, sensitive to spin-orbit correlations Curves, χQSM, Efremov et al, Czech J Phys 55 (2005) A189 proton deuteron 2000h @ 1035 s-1cm-2 NH3 and ND3 target OK con referenze Plot in alto dal PR12-07-107, curve da Efremov et al., Czech J Phys 55 (2005) A189 hep-ph/0412420 Plot in basso dal PR12-09-009, curve colorate da CQM con diverse wave functions Pasquini et al, PRD78 (2008) 034025, 0806.2298 in questo papero anche relazione h1T=g1L-h1 curve in nero sono limiti da relazione con h1 Avakian et al., PRD77 (2007) 014023, 0709.3253 Curves colored: CQM, Pasquini et al, PRD78 (2008) 034025 black: Avakian et al, PRD77 (2008) 014012 M. Contalbrigo Duke Workshop 2010 23

Collins effect Simple string fragmentation (Artru model) L=1 Sub-leading pion opposite to leading (into page) Simple string fragmentation (Artru model) L=1 r production may produce an opposite sign AUT Leading r opposite to leading p(into page) r hep-ph/9606390 Collins function: extracted from e+e- collider data (BELLE) at much higher scale than SIDIS to be investigate at SIDIS scale too • evolution of TMDs only for pions unknown for kaons • strange vacuum • strangeness in the nucleon unknown for vector mesons Fraction of direct kaons may be higher than the fraction of direct pions. LUND-MC M. Contalbrigo Duke Workshop 2010 24

Transversely Polarized TMDs with Transversely Polarized targets

CLAS transversely polarized HD-Ice target HD-Ice target vs std nuclear targets Heat extraction is accomplished with thin aluminum wires running through the target (can operate at T~500-750mK) Pros Small field (∫Bdl~0.005-0.05Tm) Small dilution (fraction of events from polarized material) Less radiation length Less nuclear background (no nuclear attenuation) Wider acceptance much better FOM, especially for deuteron H and D may be independently polarized Cons HD target is highly complex and there is a need for redundancy due to the very long polarizing times (months). Need to demonstrate that the target can remain polarized for long periods with an electron beam with currents of order of 1-2 nA Additional shielding of Moller electrons necessary (use minitorus) P= 95 % H , 70 % D HD-Ice target at ~ 1-2nA NH3 at ~ 5-10 nA Recuperare valori di polarizzazione, aggiungere che H e D possono essere polarizzati indipendentemente Details of the HD were already presented by Volker. In addition SIDIS will benefit significantly From absence of nuclear material, which complicates the final analysis due to nuclear attentation effects. And here also crucial for this experiment will be the demonstration that target can remain polarized for long periods With electron beam currents ~1-2 nA. Untested for electrons (suggestive but unverified evidence of slow depolarization from beam-generated free radicals) M. Contalbrigo Duke Workshop 2010 26

Distribution Functions (DF) TMD correlators ┴ g1L h1 Distribution Functions (DF) M. Contalbrigo Duke Workshop 2010 27

Collins asymmetry @ CLAS12 2000h @ 1034 s-1cm-2 HD-ice (P=85%) Curves fom A.V. Efremov et al PRD76:094025,2006 x Study AUT at large x (valence) where models are mostly unconstrined Tensor charge Curve da Efremov, probabilmente da PRD76 (2006) 094025 uscita postuma ATT: dilution factor dell’HD-ice !!! Solo proton quindi ? Aggiungere qui plots su tensor charge! Vedere prokudin at DIS 2008!! M. Anselmino et al hep-ph:0812.4366 M. Wakamatsu hep-ph:0811.4196 M. Contalbrigo Duke Workshop 2010 28

non spherical shape of the nucleon Pretzelosity @ CLAS12 unpolarized beam, transv. target non spherical shape of the nucleon u quark k=0 k=2.0 GeV S B. Pasquini et al. arXiv:0806.2298 n 2000h @ 1034 s-1cm-2 HD-ice (P=85%) Avakian et al., PRD78,114024 OK con referenze L’articolo di Avakian lavora col bag model e anche con spectator model Jackob hep-ph/9707340 trovano Asimmetria negativa entro I positivity bounds HD-ice for transverse because the transverse magnet can not clean the Mollers->if I have low-lumi allora meglio HD-ice con high f Relation in no-gluon models: (in bag & spectator model) M. Contalbrigo Duke Workshop 2010 30

Sivers effect @ CLAS12 unpolarized beam, transverse target 2000h @ 1034 s-1cm-2 HD-ice (P=85%) S. Arnold et al arXiv:0805.2137 Manca referenza plot pioni Plot dei K da LOI12 al pac34 Mettere 10^34 in lumi, con NH3 si escludono 2 settori e ho Pt broadening (f dipende da tutto e loro ne tengono conto, il dilution lo calcolano con target di Carbonio) M. Anselmino et al arXiv:0805.2677 Eur.Phys.J.A39:89-100,2009 M. Contalbrigo Duke Workshop 2010 31

GPDs @ CLAS12 ? Structure functions, D. Mueller, X. Ji, A. Radyushkin, A. Belitsky, … M. Burkardt, … Interpretation in impact parameter space Structure functions, quark longitudinal momentum & helicity distributions Correlated quark momentum and helicity distributions in transverse space - GPDs Proton form factors, transverse charge & current densities ? M. Contalbrigo Duke Workshop 2010 32

DVCS @ CLAS12 e p e p g Sample kinematics Q2=2.2 GeV2, xB = 0.25, -t = 0.5GeV2 Ds ~ sinfIm{k1(F2H – F1E) +…}df AUTx Target polarization in the scattering plane 2000h @ 1034 s-1cm-2 HD-ice (P=85%) AUTy Target polarization perpendicular to the scattering plane OK con referenze PUT lumi to 10^34 Asymmetries highly sensitive to the u-quark contributions to the proton spin. M. Contalbrigo Duke Workshop 2010 33

Exclusive r0 production @ CLAS12 Eu, Ed allow to map the orbital motion of quarks. 2D (Im(AB*)) T AUT ~ Q2=5 GeV2 A ~ 2Hu - Hd B ~ 2Eu - Ed r0 A ~ Hd - Hu B ~ Ed - Eu r+ 2000h @ 1034 s-1cm-2 HD-ice (P=85%) OK con referenze Confinment: distribution in PT and xT -> buono da usare. r0 A ~ 2Hu + Hd B ~ 2Eu + Ed w0 Possible flavor decomposition K. Goeke, M.V. Polyakov, M. Vanderhaeghen, 2001 B M. Contalbrigo Duke Workshop 2010 34

Summary CLAS12 is a wide-acceptance high-luminosity high-polarization experiment for a comprehensive study of the partonic transverse degree of freedoms in the nucleon Perform precise TMDs and GPDs measurements Constrain models with multi-D approach Test factorization Important test of QCD: universality SIDIS vs Drell-Yan Provide information on the Fragmentation (Collins, & polarized friends) Study higher twist effects Investigate non-perturbative to perturbative transition (along PT) Contalbrigo Marco PAC34 27 January 2009 M. Contalbrigo Duke Workshop 2010 35

p multiplicities in SIDIS ep→e’pX Hall-C M.Aghasyan DSS (Q2=2.5GeV2) DSS (Q2=25GeV2) p+/- multiplicities at large z diverge from SIDIS predictions p0 multiplicities less affected by higher twists 0.4<z<0.7 kinematical range, where higher twists are expected to be small