Deeply Virtual Compton Scattering at 11 Ge V

Deeply Virtual Compton Scattering at 11 Ge. V with transversely polarized target using the CLAS 12 detector (proposal PR 12 -12 -010) Latifa Elouadrhiri Jefferson Lab Latifa Elouadrhiri JLab PAC 39, June 19, 2012

CLAS 12 - Proposal PR 12 -12 -010 Collaboration • Thomas Jefferson National Accelerator Facility • French Collaboration: – CPh. T Ecole Polytechnique, – IPN (Orsay), – LPSC (Grenoble) – LPT (Orsay) – SPh. N (Saclay) CEA/DAPNIA • Italian Collaboration – University of Ferrara and INFN Ferrara – Universita di Roma – INFN-Sezione di Roma 2, Rome – Dipartimento di Fisica, Universita’ di Roma Tor Vergata – Dipartamento di Fisica and INFN, Sezione di Genova – LNF INFN, Frascati, Rome – University of Bari and INFN Bari Spokespersons: – H. Avakian (JLab) – – – V. D. Burkert (JLab) L. Elouadrhiri* (JLab) M. Guidal (Orsay) M. Lowry (JLab)** F. Procureur (Saclay) *Contact ** Target Expert • University of Glasgow, UK • University of Connecticut, Storrs, CT • Fairfield University, Fairfield CT, USA • Kyungpook National University, Republic of Korea • Old Dominion University, Norfolk, USA • Moscow State University, Moscow, Russia Latifa Elouadrhiri JLab PAC 39, June 19, 2012 and the CLAS collaboration

Outline • GPDs and the quark-structure of the proton • Accessing GPDs in DVCS – Results from existing from CLAS data – Anticipated data from approved CLAS 12 experiments • Experimental Setup • Projections for 11 Ge. V – Extraction of GPDs – Parton density in transversely polarized nucleon – u-quark and d-quark contributions • Summary and beam request Latifa Elouadrhiri JLab PAC 39, June 19, 2012

Quantum phase-space distributions of quarks Wpq(x, k. T, r) “Mother” Wigner distributions 2 d d 3 r Probability to find a quark q in a nucleon P with a certain polarization in a position r & momentum k k. T T) (F [Wigner (1932)] QM [Belitsky, Ji, Yuan (04)] QFT (Breit frame) [Lorce’, BP (11)] QFT (light cone) TMD PDFs: fpu(x, k. T), … Semi-inclusive measurements Momentum transfer to quark Direct info about momentum distribution GPDs: Hpu(x, x, t), … d 2 k T 0 t, = 0 x= Exclusive Measurements Momentum transfer to target Direct info about spatial distribution PDFs fpu(x), … This Proposal Exclusive Physics: DVCS with Transverse Target PR 12 -105 &C 12 -11 -111 SIDIS Physics with Transverse Target Contalbrigo M. Latifa Elouadrhiri JLab PAC 39, June 19, 2012 JLPAC 39, 18 th June 2012, Newport News 4

Deep Virtual Compton Scattering (DVCS) and Generalized Parton Distributions x: average fraction of quark longitudinal momentum : fraction of longitudinal momentum transfer ~ ~ H, E, H, E : Generalized Parton Distributions (GPDs) 3 -D Imaging conjointly in transverse impact parameter and longitudinal momentum Latifa Elouadrhiri JLab PAC 39, June 19, 2012

GPDs and transverse imaging Latifa Elouadrhiri JLab PAC 39, June 19, 2012

Deeply Virtual Compton Scattering (DVCS) The Cleanest Probe at low medium energies Latifa Elouadrhiri JLab PAC 39, June 19, 2012

A path towards extracting GPDs + - A = + = 2 + ξ ~ x. B/(2 -x. B) k = t/4 M 2 Polarized beam, unpolarized target: ~ LU ~ sin {F 1 H + ξ(F 1+F 2)H +k. F 2 E}d H(ξ, t) Unpolarized beam, longitudinal target: ~ UL ~ sin {F 1 H+ξ(F 1+F 2)(H +ξ/(1+ξ)E)}d ~ H(ξ, t) Unpolarized beam, transverse target: UT ~ cos sin( s- ){k(F 2 H – F 1 E)}d Latifa Elouadrhiri JLab PAC 39, June 19, 2012 E(ξ, t)

GPDs in DVCS experiments with CLAS and CLAS 12 Nucleon polarization Unpolarized Sensitivity to GPDs ~ H, H, E ~ L. Polarized H, H, E T. Polarized E, H E 01 -113 : γ, π0 proton – 6 Ge. V, L. Elouadrhiri et al E 12 -06 -119 : γ, π0 proton – 11 Ge. V, F. Sabatie et al. E 12 -11 -003: γ, π0 neutron – 11 Ge. V, S. Nicolai et al. E 05 -114: γ, π0 (NH 3) proton- 6 Ge. V, L. Elouadrhiri et al. E 12 -06 -119 : γ, π0 (NH 3) proton-11 Ge. V, F. Sabatie et al. E 08 -021 : γ, π0 (HD) proton-11 Ge. V, V. D. Burkert et al. This Proposal : γ, π0 (HD) proton-11 Ge. V, L. Elouadrhiri et al. Latifa Elouadrhiri JLab PAC 39, June 19, 2012

CLAS Proton BSA and Cross section E 01 -113 F. -X. G. et al. , PRL 100(2008)162002 • More than 3 k φ-bins • Quantitative constraints on parameters Green band shows difference with BH Sensitivity to d 1 Latifa Elouadrhiri JLab PAC 39, June 19, 2012

CLAS DVCS target spin asymmetry results E 05114 ■ - preliminary results of eg 1 -dvcs ■ - pioneering measurements from CLAS-eg 1 b □ - results from HERMES AUL Preliminary Latifa Elouadrhiri JLab PAC 39, June 19, 2012

CLAS 12 DVCS approved experiments Large angle coverage: 5°- 135° Broad kinematic range coverage High luminosity: 1035 cm-2 s-1 Concurrent measurement of deeply virtual exclusive, semi-inclusive, inclusive processes, for same target Central Detector Dynamically polarized target NH 3, ND 3 • Polarization: 0. 8 • Dilution factor: 0. 15 (fraction of events from polarized material) • Magnetic field: 5 T Forward Detector E 12 -06 -119 : γ, π0 E 12 -11 -003: γ, π0 proton – 11 Ge. V, F. Sabatie et al. neutron – 11 Ge. V, S. Nicolai etal. E 12 -06 -119 : γ, π0 (NH 3) proton-11 Ge. V, F. Sabatie et al. Latifa Elouadrhiri JLab PAC 39, June 19, 2012

Q 2 (Ge. V 2) CLAS 12 approved DVCS program E=11 Ge. V x. B/Q 2 acceptance with CLAS 12 x. B 80 days of beam time 85% beam pol. 1035 cm-2 s-1 luminosity 1 < Q 2 < 10 Ge. V 2 0. 1 < x. B < 0. 65 -tmin < -t < 2. 5 Ge. V 120 days of beam time Pbeam = 85%, Ptarget = 80% 1035 cm-2 s-1 luminosity 1 < Q 2 < 10 Ge. V 2 0. 1 < x. B < 0. 65 -tmin < -t < 2. 5 Ge. V 2 Latifa Elouadrhiri JLab PAC 39, June 19, 2012

We propose to measure DVCS process at 11 Ge. V with transversely polarized target using the CLAS 12 detector CLAS 12 will provide the large acceptance and transverse target to cover wide phase space The 11 Ge. V CEBAF electron beam allows to cover a large Q 2, XB, t range Measurements of DVCS with Transversely Polarized Target are crucial for the completion of a comprehensive GPD program for JLab@12 Ge. V Latifa Elouadrhiri JLab PAC 39, June 19, 2012

Experimental Setup Luminosity 5 x 1033 cm-2 s-1 FTOF H and D polarized targets Broad kinematic range coverage (current to target fragmentation) DC R 3 R 2 R 1 EC RICH HTCC HD-Ice PCAL HD-Ice: Transverse Target (common to PR 12 -105 and C 12 -11 -111) Solenoid Torus Latifa Elouadrhiri JLab PAC 39, June 19, 2012 Contalbrigo M. 15

Tracking - Protons and electrons resolutions Experimental configuration wit HDIce have been implemented in the standard CLAS 12 software, complete Geant 4 simulation, tracking and particle identification. The obtained resolutions for both electrons and protons fulfill technical CLAS 12 specifications Contalbrigo M. Latifa Elouadrhiri JLab PAC 39, June 19, 2012 JLab PAC 39, 18 th June 2012, Newport News 16

Event Selection ep ep ep g ep p 0, h ep All these channels are measured for efficiency studies and background subtraction ep g Angular cut to separate p 0 and nuclear background Angle between calculated photon, using reconstructed proton and electron and the real photon. Latifa Elouadrhiri JLab PAC 39, June 19, 2012

Kinematics coverage Errors (in color) with external squares corresponding to x vs Q 2 and with internal squares corresponding to φ vs t. Latifa Elouadrhiri JLab PAC 39, June 19, 2012

Transverse target spin asymmetry AUT 100 days of beam time 80% beam polarization 60% target polarization 5 x 1033 cm-2 s-1 luminosity Q 2 = 2. 5 x. B = 0. 2 High precision data over a large phase space will allow us to measure the CFF-E and constrain the quark angular momentum in the proton, Jq Latifa Elouadrhiri JLab PAC 39, June 19, 2012

Double spin asymmetry ALT 100 days of beam time 80% beam polarization 60% target polarization 5 x 1033 cm-2 s-1 luminosity Q 2 = 2. 5 x. B = 0. 2 At large t, ALT on proton target shows strong sensitivity to u-quarks. Latifa Elouadrhiri JLab PAC 39, June 19, 2012

Extraction of Compton Form Factors from expected DVCS data In general, 8 GPD quantities accessible Compton Form Factors, (CFF) DVCS : golden channel anticipated leading Twist dominance already at low Q 2 Latifa Elouadrhiri JLab PAC 39, June 19, 2012

GPD Extraction – Im E Model-independent fit, at fixed x. B, t and Q 2, of DVCS observables Latifa Elouadrhiri JLab PAC 39, June 19, 2012

GPD Extraction – Im H Model-independent fit, at fixed x. B, t and Q 2, of DVCS observables Latifa Elouadrhiri JLab PAC 39, June 19, 2012

Parton density in transversely polarized nucleon Parton density in a transversely polarized nucleon is not experimentally accessible What is directly accessible is the Fourier transform Contribution of E &H Contribution of E Latifa Elouadrhiri JLab PAC 39, June 19, 2012

Summary & Beam Request – Measurement of azimuthal moments in DVCS with transversely polarized hydrogen targets are highly sensitive to the GPD-E and the quark contributions to the angular momentum of the proton. – Precision measurements of single (and double) spin asymmetries with CLAS 12 with transversely polarized HD-Ice target provide: • Stringent constraints on GPD- E(x= , , t) both imaginary and real part • Quark distributions in transverse impact parameter space – Combined with approved CLAS 12 DVCS experiment on the neutron will allow the first flavor separation Request: approval of 100 days of running at 11 Ge. V with polarized electron beam (Pe=80%) and polarized HD target (60% polarized H), and an additional 10 days with non-polarized target, and empty targets. Runs parallel with C 12 -11 -111 and PR 12 -105 Latifa Elouadrhiri JLab PAC 39, June 19, 2012