CLAS12 European Workshop Physics requiring RICH Contalbrigo Marco INFN Ferrara CLAS12 European Workshop February 26, 2009 Contalbrigo Marco CLAS12 European Workshop 26 February 2009

Kaon in SIDIS Approved by PAC34: PR12-09-07: Studies of partonic distributions using semi-inclusive production of Kaons PR12-09-08: Studies of Boer-Mulders Asymmetry in Kaon Electroproduction with Hydrogen and Deuterium Targets PR12-09-09: Studies of Spin-Orbit Correlations in Kaon Electroproduction in DIS with polarized hydrogen and deuterium targets Contalbrigo Marco CLAS12 European Workshop 26 February 2009

The Spin Structure of the Nucleon Describe the complex nucleon structure in terms of partonic degrees of freedom of QCD Important testing ground for QCD Phys Lett B647 (2007) 8-17 Latest news from Deep Inelastic Scattering (DIS) DS=0.33±0.03 Phys. Rev. D 75 (2007) 012007 DG small at 0.02<x<0.3 From DIS and pp scattering e-print 0804.0422 Proton’s spin Jq Jg Understanding of the orbital motion of quarks crucial!!! Contalbrigo Marco CLAS12 European Workshop 26 February 2009

Distribution Functions (DF) Fragmentation Functions (FF) Correlation Functions Distribution Functions (DF) Fragmentation Functions (FF) N/q U L T q(x) Dqh(z) Hadron ID provides flavor tagging !! constrain the unpolarized strange sea disentangle distribution and fragmentation functions Contalbrigo Marco CLAS12 European Workshop 26 February 2009

Strange parton distribution Isoscalar target Charge conjugation in FF K Constrain strange sea Reduce uncertainty on NS (and S) fragmentation functions PR12-09-07: H2 & D2 (54 days) X Contalbrigo Marco CLAS12 European Workshop 26 February 2009

Distribution Functions (DF) Fragmentation Functions (FF) Correlation Functions Distribution Functions (DF) Fragmentation Functions (FF) N/q U L T Dqh D Hadron ID provides flavor tagging !! flavor decomposition of quark helicity Contalbrigo Marco CLAS12 European Workshop 26 February 2009

Helicity distribution Flavour decomposition of quark helicity Is the light sea symmetrically polarized ? Contalbrigo Marco CLAS12 European Workshop 26 February 2009

Helicity distribution Flavor decomposition • Constrain very well the valence • Explore the valence-sea transient • Check sea polarization symmetry • Improve phenomenological fits indirect information on DG Hep-ex 0804.0422 Isoscalar method Flavor decomposition of quark helicity PR12-09-07: NH3 (30 days) & ND3 (50 days) Contalbrigo Marco CLAS12 European Workshop 26 February 2009

ALL PT-dependence in SIDIS M.Anselmino et al hep-ph/0608048 m02=0.25GeV2 mD2=0.2GeV2 LL ALL Constituent quark model (Pasquini et al). 0.4<z<0.7 p+ ALL suggests broader kT distributions for f1 compared to g1 p- ALL may require non-Gaussian kT-dependence for different helicities and/or flavors Contalbrigo Marco CLAS12 European Workshop 26 February 2009

ALL PT-dependence in SIDIS M.Anselmino et al hep-ph/0608048 m02=0.25GeV2 mD2=0.2GeV2 proton deuteron GRSV-2000+Kretzer PR12-09-09: NH3 (30 days) & ND3 (50 days) Azimuthal asymmetry sensitive to the difference of kT -widths in PDFs Complete set required for the flavor decomposition (H,D target + K,p ID) Contalbrigo Marco CLAS12 European Workshop 26 February 2009

Distribution Functions (DF) TMDs Correlation Functions pp pX Distribution Functions (DF) Off-diagonal elements: interference of partial-wave function for different orbital momentum states ┴ ┴ SIVERS Quark orbital angular momentum ┴ ┴ ┴ GPD E GPD ET pT<2 GeV/c √s = 20 GeV xF AN pp pX anti-green remnant green quark Contalbrigo Marco CLAS12 European Workshop 26 February 2009

Distribution Functions (DF) Fragmentation Functions (FF) Sivers Function Distribution Functions (DF) Fragmentation Functions (FF) N/q U L T Contalbrigo Marco CLAS12 European Workshop 26 February 2009

Sivers function p+ (u,d) K+(u,s) M.Anselmino et al hep-ph/0805.2677 D. de Florian et al., Phys. Rev. D75 (2007) 114010 p+ (u,d) K+(u,s) Clear example of flavor sensitivity thanks to hadron ID From kaon vs pion comparison Unpolarized SIDIS provides detailed description of FFs Polarized SIDIS provides information on sea contribution to Sivers: • saturation of sbar • clear negative tendency for dbar Contalbrigo Marco CLAS12 European Workshop 26 February 2009

Sivers function Still preliminary data Role of evolution ? CLAS12 with transverse target Contalbrigo Marco CLAS12 European Workshop 26 February 2009

Distribution Functions (DF) Fragmentation Functions (FF) TMDs Correlation Functions NA10 E866 E615 hp mmX BOER-MULDERS Spin Orbit effect Distribution Functions (DF) ┴ g1L ┴ h1 ┴ ┴ ┴ ee ppX COLLINS Quark spin probe Fragmentation Functions (FF) N/q U L T Contalbrigo Marco CLAS12 European Workshop 26 February 2009

Non-collinear SIDIS off unpolarized targets ep e’hX longitudinal to transverse photon flux Intrinsic kT “Cahn effect” (1978) g1L h1 Contalbrigo Marco CLAS12 European Workshop 26 February 2009

Cosnf moments (Up to 2008) cosf cos2f No hadron identification EMC (1987) EMC (1987) E665 (1993) ZEUS (2000) No hadron identification No charge separation Poor statistics for cos2f Qualitative agreement with expectations based on Cahn model, but investigation far to be conclusive Contalbrigo Marco CLAS12 European Workshop 26 February 2009

SIDIS off unpolarized targets ep e’hX longitudinal to transverse photon flux Leading twist g1L h1 Contalbrigo Marco CLAS12 European Workshop 26 February 2009

FUU structure func. Expansion up to twist 3 pQCD CORRECTIONs Convolution integral over transverse momenta with implicit sum over quark flavours BOER-MULDERS x COLLINS Access to partonic transverse spin and momentum correlations in distribution and fragmentation CAHN EFFECT Sensitive to partonic intrinsic transverse momentum extracted only from Drell-Yan same sign for u and d in agreement with most of the models sign change between DY and SIDIS • universality of TMDs Boer-Mulders function: x Fit to Drell-Yan DATA PhysRevD77 (2008) 034035 Fundamental prediction of QCD ! Contalbrigo Marco CLAS12 European Workshop 26 February 2009

FUU structure func. Expansion up to twist 3 BOER-MULDERS x COLLINS Convolution integral over transverse momenta with implicit sum over quark flavours Access to partonic transverse spin and momentum correlations in distribution and fragmentation CAHN EFFECT Sensitive to partonic intrinsic transverse momentum Dfav -Dunf FIT TO BELLE DATA Transversity 2008, Ferrara 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 still unknown for kaons • strange vacuum • strangeness in the nucleon Contalbrigo Marco CLAS12 European Workshop 26 February 2009

Sign change with hadron charge ! p- p+ Cos2f moments Boer-Mulders All contributions Cahn (twist 4) V. Barone et al. Phys.Rev.D78:045022,2008 Non-zero ! Sign change with hadron charge ! ? Experiments still working hard to control systematics How large is the contribution at higher twist ? How to compare different Q2 ? Contalbrigo Marco CLAS12 European Workshop 26 February 2009

SIDIS off unpolarized targets ep e’hX longitudinal to transverse photon flux Twist-3 Leading twist g1L h1 Contalbrigo Marco CLAS12 European Workshop 26 February 2009

FUU structure func. Expansion up to twist 3 BOER-MULDERS + COLLINS Access to Partonic transverse spin and momentum correlations In distribution and fragmentation CAHN EFFECT Access to Partonic intrinsic transverse momentum Contalbrigo Marco CLAS12 European Workshop 26 February 2009

Cosf moments Large negative effect confirmed ! preliminary How large is the uncertainty in predictions from intrinsic transverse momentum distribution ? Is Cahn effect diluted by other terms ? preliminary Is the difference between p+ and p- the sign of a non-zero boer-mulders ? Contalbrigo Marco CLAS12 European Workshop 26 February 2009

Boer-Mulders kaon asymmetry @ CLAS12 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 Excellent precision vs model uncertainties PR12-09-08: 54 days at L=1x1035 cm-2s-1 Contalbrigo Marco CLAS12 European Workshop 26 February 2009

Distribution Functions (DF) Fragmentation Functions (FF) Collins function & transversity Distribution Functions (DF) Fragmentation Functions (FF) N/q U L T Contalbrigo Marco CLAS12 European Workshop 26 February 2009

Collins function & transversity No kaon analysis Valence poorly constrained M.Anselmino et al hep-ph/0812.4366 CLAS12 with transverse target Contalbrigo Marco CLAS12 European Workshop 26 February 2009

Executive summary Crucial: completeness 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 Still incomplete phenomenology is asking for new inputs Crucial: completeness flavor tagging and five-fold differential extraction in all variables (x,z,Q2,PT) to have all dependencies resolved Contalbrigo Marco CLAS12 European Workshop 26 February 2009

CLAS12: experimental set-up multi-purpose detector for fixed target electron scattering experiments broad kinematical range large luminosity Polarized beam H and D targets 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) Q2>1GeV2 W2>4 GeV2 y<0.85 MX>2GeV Contalbrigo Marco CLAS12 European Workshop 26 February 2009

Kinematic dependence of K/ ratios Critical for separation moment range 2<PK<5 and q<25 degree central detector forward detector K PEPSI LEPTO predictions Only reliable is p identification Contalbrigo Marco CLAS12 European Workshop 26 February 2009

CLAS12 Acceptance MC studies CLAS12 SIDIS MC (LUND-PEPSI) used to study azimuthal moments from acceptance and radiative corrections for different pions. generated reconstructed ep+X 0 0.5 1 1.5 PT 0.4 0.0 - 0.6 Contalbrigo Marco CLAS12 European Workshop 26 February 2009

CLAS12 Acceptance MC studies CLAS12 SIDIS MC (LUND-PEPSI) used to study azimuthal moments from acceptance and radiative corrections for different pions. generated reconstructed ep+X PT After acceptance correction the generated azimuthal moments are recovered with an error < 10% (dominant contribution to systematics) Even better results expected with a fully-differential analysis Contalbrigo Marco CLAS12 European Workshop 26 February 2009

A Rich detector for CLAS12 LTCC Only reliable is p identification Contalbrigo Marco CLAS12 European Workshop 26 February 2009

A Rich detector for CLAS12 2/3 cm 60/80 cm pad cathode coated with CsI film Proximity Gap A Rich detector would strongly enhance the CLAS12 capabilities in particle identification and would open possibilities for new physics Replacement of LTCC with proximity focusing CsI Rich detector  good separation of p/K/p in the 2-5 GeV/c momentum range  no impact on the baseline design of CLAS 12  minimum impact on spectrometer performace Contalbrigo Marco CLAS12 European Workshop 26 February 2009

A Rich detector for CLAS12 MC simulation:  3 cm thick C5F12 radiator  80 cm CH4 proximity gap  1 cm pixel pad size  5 o-30 o radiator polar angle 4s K-p separation at 5 GeV/c 80 % kaon eff. with 1:1000 p rejection 95 % kaon eff. with 1:100 p rejection Already with 2 sectors gain of factor ~3 in the relevant z region of interest without RICH with RICH Contalbrigo Marco CLAS12 European Workshop 26 February 2009

2-D Collins moments for p± x vs z z vs Ph ┴ Contalbrigo Marco CLAS12 European Workshop 26 February 2009

1-Hadron Production (ep epX) le ST I[h1H1┴] Transversity & Collins d le N/q U L T f1 h1 g1 h1L f1T g1T h1 h1T SL le Contalbrigo Marco CLAS12 European Workshop 26 February 2009

Other leading twist DF Contalbrigo Marco CLAS12 European Workshop 26 February 2009

Target SSA measurements at CLAS Complete azimuthal coverage crucial for separation of sinf, sin2f moments ep→e’pX p1sinf+p2sin2f CLAS PRELIMINARY W2>4 GeV2 Q2>1.1 GeV2 y<0.85 0.4<z<0.7 MX>1.4 GeV p1= 0.059±0.010 p2=-0.041±0.010 p1=-0.042±0.015 p2=-0.052±0.016 p1=0.082±0.018 p2=0.012±0.019 PT<1 GeV 0.12<x<0.48 No indication of Collins effect for p0 (x20 more data in 2009)

Collins frag.: Longitudinally polarized target Kotzinian-Mulders Asymmetry proton deuteron Pasquini et al. Study the Collins function of kaons Provides independent information on the RSMT TMD Contalbrigo Marco CLAS12 European Workshop 26 February 2009

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

Structure of the Nucleon GPDs/IPDs d2kT Wpu(k,rT) “Mother” Wigner distributions d2rT d2kT TMD PDFs f1u(x,kT), .. h1u(x,kT) quark polarization PDFs f1u(x), .. h1u(x) Gauge invariant definition (Belitsky,Ji,Yuan 2003) Universality of kT-dependent PDFs (Collins,Metz 2003) Factorization for small kT. (Ji,Ma,Yuan 2005) Analysis of SIDIS and DVMP are complementary! Contalbrigo Marco CLAS12 European Workshop 26 February 2009