DVCS Exclusive Vector meson Large-x PDFs The CLAS12 detector } 3 particular Examples among many others

DVCS Exclusive Vector meson Large-x PDFs The CLAS12 detector

DVCS Bethe-Heitler GPDs

DVCS Bethe-Heitler GPDs

Proton-DVCS BSAs with CLAS12  LU ~sin  {F 1 H +.  }d  e p ep  Kinematically suppressed A =           = Sensitivity to H( ,t)

DVCS/BH Longitudinal Target Asymmetry e p ep  Longitudinally polarized target  UL ~sin  Im{F 1 H +  (F 1 +F 2 ) H... }d  ~ Sensitivity to H(ξ,t) ~ CLAS12

JLab Hall A Collaboration, PRL 99:242501,2007 en en  0 because F 1 (t) is small 0 because of cancelation of u and d quarks n-DVCS gives access to the least known and constrained GPD, E

 = 60° x B = 0.17 Q 2 = 2 GeV 2 t = -0.4 GeV 2 n-DVCS BSA is: very sensitive to J u, J d can be as strong as for the proton According to the kinematics and Ju, Jd DVCS on the neutron J u =.3, J d =.1 J u =.8, J d =.1 J u =.5, J d =.1 J u =.3, J d =.8 J u =.3, J d =-.5 E e = 11 GeV DVCS BSA: sensitivity to Ju,Jd Hall A 6 GeV

 = 60° x B = 0.2 Q 2 = 2 GeV 2 t = -0.2 GeV 2 DVCS BSA: sensitivity to J u,d DVCS on the proton J u =.3, J d =.1 J u =.8, J d =.1 J u =.5, J d =.1 J u =.3, J d =.8 J u =.3, J d =-.5 E e = 11 GeV

nDVCS with CLAS12 ~ 80% of neutrons from n-DVCS have  >40° → neutrons detector for central part of CLAS12 (CD) ~ 0.4 GeV/c ed→e’n  (p) Detected in CLAS12 (FD) Detected in FEC, IC Not detected PID (n or  ?) + angles to identify final state CD CND CTOF Central Tracker Technical challenges : available room very small (thickness cm) → no room for light guides → need a compact read-out system strong magnetic field (5 T) → photodetectors insensitive to the magnetic field (SiPMs or Microchannel PMTs) resolution on time-of-flight ~ 150 ps to distinguish neutrons from photons

DVCS Exclusive Vector meson Large-x PDFs The CLAS12 detector

Longitudinal cross section  L  (  * L p  p  L 0 ) S. Morrow et al., Eur.Phys.J.A39:5, 2009 (  C. Hadjidakis et al., Phys.Lett.B605:256, 2005 (  GeV)

ep  ep  0 EPJA09 VGG GPD model GK GPD model

VGG + “meson exchange” VGG w/o “meson exchange” (VGG) “meson exchange”

k perp corr. ( + “meson exchange”) Leading twist handbag

CLAS HERMES

d  /dt (  * p  p  0 ) b constant as Q 2 increases ?

  

DVCS Exclusive Vector meson Large-x PDFs The CLAS12 detector

The Problem: nuclear binding uncertainties prevent us from knowing F 2n and d/u(x  1) F 2n extracted from deuteron data The Solution: spectator proton tagging  select low-momentum part of d wave function and tag motion of struck neutron W spectrum on d kinematically corrected W spectrum on n in d How? Slow proton recoil detector (radial TPC) F 2n /F 2p Analysis underway… results in late 2009 BoNuS (Experiment e8 w/ CLAS) W > 1.9 GeV Q 2 > 1 GeV 2 W > 1.6 GeV Q 2 > 2 GeV 2

Valence Quark Distribution d/u CLAS12 en(p s ) → ep s X Measure spectator proton to tag scattering of “free” neutron with small FSI. There is large uncertainty in the ratio d/u of down and up quark distributions at large x, due to large effects of nuclear wave function. This can be significantly improved by performing the measurement at kinematics where nuclear effects are under control.

Existing Data from CLAS Isgur, PRD 59, (2003) } Close and Melnitchouk, PRC 68, (2003) Proton Deuteron W > 2; Q 2 > 1 Valence spin structure function CLAS12

Proton Deuteron W > 2; Q 2 > 1 CLAS12 ΔG(x) Accurate measurement of Q 2 dependence is key for extraction of ΔG(x)

 GPD’s and 3D-Imaging of the Nucleon  Deeply Virtual Compton Scattering - DVCS  Deeply Virtual meson Production at low/high t  Valence Quark Distributions  u- and d-Quark Spin Distributions in Proton and Neutron  Neutron Structure Function F 2n (x,Q 2 ), d/u  TMD Quark Distribution Functions in SIDIS  Form Factors and Resonance Excitations  The Magnetic Structure of the Neutron – G Mn  N* Transition Form Factors at high Q 2 Proposed Initial Physics Program in Hall B  Hadrons in the Nuclear Medium  Space-Time Characteristics of Quark Hadronization  Color Transparency  Short Distance Dynamics of Light Nuclei 13 CLAS12 already approved experiments (and 7 LOIs) corresponding to about 5 years of scheduled beam operation.

DVCS Exclusive Vector meson Large-x PDFs The CLAS12 detector

A B C Jefferson Lab Today Large acceptance spectrometer electron/photon beams Hall B

CLAS12 Central Detector Forward Detector

Single sector (exploded view) Beamline equipment CLAS12

CLAS12 Central Detector Superconducting 5T Solenoid Magnet, 78cm ø warm bore.Superconducting 5T Solenoid Magnet, 78cm ø warm bore. Central Time-of-Flight array (CTOF)Central Time-of-Flight array (CTOF) ΔT < 60psec Silicon Vertex TrackerSilicon Vertex Tracker 31

CLAS12 – Solenoid, Torus Magnets & Tracking Chambers DC: 36 layers iπ 3 regions, 6 sectors, 24,000 sense wires. IC: Calorimeter, 424 PbWO crystals DC’s IC The B-field transverse to the particle trajectory is approximately matched to the average particle momentum.

CLAS12 – PID & Calorimetry FTOF FTOF: Timing resolution ΔT<80ps PCAL EC Forward Carriage LTCC PCAL/EC: Electron, photon, neutron detection, high energy γ/π 0 reconstruction. LTCC: Electron & pion separation. RICH: Needed for better Kaon id in some sectors.

Forward Central Detector Angular range Charged Particles 5 0 – – Photons 2 0 – 40 0 N/A Resolution  p/p (%) < 5 GeV/c < 0.5 GeV/c  (mr)< 0.5< 10  (mr)< 0.5< 6 Photon detection Energy (MeV)>150N/A  (mr)4 (1GeV)N/A Neutron detection N eff 0.1 – Particle ID e/  Full rangeN/A  pFull range≤ 1.2 GeV/c  /KFull range≤ 0.65 GeV/c K/p  GeV/c≤ 0.90 GeV/c    Full rangeN/A  Full rangeN/A Design Parameters (Base equipment) Design Parameters (Base equipment) CLAS12 Central Detector Forward Detector

CLAS12 in Hall B Moller polarimeter Photon Energy tagging system Polarized targets Goniometer/polarized photons Pair spectrometer Beam monitors

Future Upgrades to CLAS12 Base Equipment Micromegas (Saclay) –Detailed simulation and track reconstruction –Prototypes being tested, engineering design underway –Review will take place in May 2009 RICH Detector (INFN, Argonne, UK ) –Conceptual design with detailed simulations –PAC 34 approved 3 major experiments requiring RICH Neutron detector (IN2P3/INFN) –Detailed simulations, components being studied –PAC 34 gave high rating to the science presented in LOI HD-ice Polarized target (JLab/INFN) –Laboratory facility being designed Quasi real photon tagging facility (INFN, UK) –Feasibility study

Institution Focus Area Arizona State University (US)Beamline, Tagging System Argonne National Laboratory (US) Cerenkov Counter California State University (US)Cerenkov Counters Catholic University of America (US)Software College of William & Mary (US)Calorimetry, Magnet Mapping Edinburgh University (UK)Software Fairfield University (US)Polarized Target Florida International University, Miami (US)Beamline/Moller polarimeter Glasgow University (UK) Central Detector, DAQ, Forward Tagger, RICH Grenoble University/IN2P3 (France) Central Detector Idaho State University (US)Drift chambers INFN –University Bari (Italy)tbd, interest in RICH INFN –University Catania (Italy)tbd INFN – Frascati and Fermi Center (Italy)Central Neutron Detector+ interest show in RICH INFN –University Ferrara (Italy) (will join in 2010)tbd, interest in RICH INFN – University Genoa (Italy)Central Neutron Detector+ interest in Forward Tagger INFN – ISS/Rome 1(Italy) tbd, interest in RICH INFN – University of Rome Tor Vergata(Italy) Central Neutron Detector+ HD target Institute of Theoretical and Experimental Physics (Russia)SC. Magnets, Simulations James Madison University (US) Calorimetry Kyungpook National University (Republic of Korea)CD TOF Los Alamos National Laboratory (US)Silicon Tracker Moscow State University, Skobeltsin Institute for Nuclear Physics (Russia)Software, SVT Moscow State University (High Energy Physics) (Russia) Silicon Tracker Norfolk State University (US) Preshower Calorimeter Ohio University (US)Preshower Calorimeter Orsay University/IN2P3 (France)Central Neutron Detector Old Dominion University (US)Drift Chambers Renselear Polytechnic Institute (US) Cerenkov Counters CEA Saclay (France)Central Tracker, Reconstruction software Temple University, Philadelphia (US)Cerenkov Counters Thomas Jefferson National Accelerator Facility (US)Project coordination & oversight University of Connecticut (US) Cerenkov Counters University of New Hampshire (US)Central Tracker, Offline Software University of Richmond (US)Offline Software University of South Carolina (US)Forward TOF University of Virginia (US) Beamline/Polarized Targets Yerevan Physics Institute (Armenia)Calorimetry CLAS12 Institutions

Oct ‘13: Hall A commissioning start Apr ‘14: Hall D commissioning start Oct ‘14: Hall B & C commissioning start 12 GeV Schedule