DVCSDVCS

Exclusive Vector mesonExclusive Vector meson

Large-x PDFsLarge-x PDFs

The CLAS12 detectorThe CLAS12 detector

} 3 particularExamplesamong many others

DVCSDVCS

Exclusive Vector mesonExclusive Vector meson

Large-x PDFsLarge-x PDFs

The CLAS12 detectorThe CLAS12 detector

DVCS Bethe-Heitler

GPDs

DVCS Bethe-Heitler

GPDs

Proton-DVCS BSAs with CLAS12

LU~sin{F1H+.}d

e p ep

Kinematically suppressed

A =

=

Sensitivityto H(,t)

DVCS/BH Longitudinal Target AsymmetryDVCS/BH Longitudinal Target Asymmetry

e p ep

Longitudinally polarized target

UL~sinIm{F1H+(F1+F2)H...}d~

Sensitivityto H(ξ,t)~

CLAS12CLAS12

JLab Hall A Collaboration, PRL 99:242501,2007

en en

EHHF )(4

~)()()()( 22211 tF

M

ttFtFtFC I

n

0 because F1(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°xB = 0.17Q2 = 2 GeV2

t = -0.4 GeV2

n-DVCS BSA is:• very sensitive to Ju, Jd • can be as strong as for the protonAccording to the kinematics and Ju, Jd

DVCS on the neutron Ju=.3, Jd=.1

Ju=.8, Jd=.1

Ju=.5, Jd=.1

Ju=.3, Jd=.8

Ju=.3, Jd=-.5

Ee = 11 GeV

DVCS BSA: sensitivity to Ju,Jd Hall A 6 GeV

= 60°xB = 0.2Q2 = 2 GeV2

t = -0.2 GeV2

DVCS BSA: sensitivity to Ju,d

DVCS on the proton Ju=.3, Jd=.1

Ju=.8, Jd=.1

Ju=.5, Jd=.1

Ju=.3, Jd=.8

Ju=.3, Jd=-.5

Ee = 11 GeV

nDVCS with CLAS12

~ 80% of neutrons from n-DVCS have >40°

→ neutrons detectorfor central part of CLAS12 (CD)

<pn>~ 0.4 GeV/c

ed→e’n(p)

Detected in CLAS12 (FD)

Detected inFEC, IC

Not detected

PID (n or ?) + angles to identify final state

CD

CND

CTOF CentralTracker

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

DVCSDVCS

Exclusive Vector mesonExclusive Vector meson

Large-x PDFsLarge-x PDFs

The CLAS12 detectorThe CLAS12 detector

Longitudinal cross section L(*Lp pL

0)

S. Morrow et al., Eur.Phys.J.A39:5,2009 (0@5.75GeV)

C. Hadjidakis et al., Phys.Lett.B605:256,2005 (0@4.2 GeV)

ep ep ep ep00

EPJA09

VGG GPD model

GK GPD model

VGG + “meson exchange”

VGG w/o “meson exchange” (VGG)

“meson exchange”

kperp corr. (+ “meson exchange”)

Leading twist handbag

CLAS

HERMES

d/dt (*p p0)

b constant as Q2

increases ?

DVCSDVCS

Exclusive Vector mesonExclusive Vector meson

Large-x PDFsLarge-x PDFs

The CLAS12 detectorThe CLAS12 detector

The Problem: nuclear binding uncertainties prevent us from knowing F2n and d/u(x1)

d

u

4F2n F2p 1

4 F2n F2p

F2n 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)

F2

n/F

2p

Analysis underway… results in late 2009

BoNuS(Experimente8 w/ CLAS)

W > 1.9 GeVQ2 > 1 GeV2

W > 1.6 GeVQ2 > 2 GeV2

Valence Quark Distribution d/uValence Quark Distribution d/uCLAS12CLAS12

en(ps) → epsX

Measure spectator proton to tag Measure spectator proton to tag scattering of “free” neutron with scattering of “free” neutron with small FSI. 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

xbj

A1d ( D-state corrected ) HF perturbed QM

World Data Parm + d WF Q2 = 4.2 GeV2

World Data parm Q2 = 10 GeV2

Spin 3/2 suppression

Helicity 3/2 suppression

Symmetric Q Wave function suppression

SLAC - E143

SMC

HERMES

SLAC - E155

CLAS-EG1b Q2 = 1.0 - 4.52 GeV2

SU(6)

pQCD

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Isgur, PRD 59, 034013 (2003)

}

Close and Melnitchouk, PRC 68, 035210 (2003)

xbj

A1p

HF perturbed QM

World Data parm Q2 = 10 GeV2

Spin 3/2 suppression Helicity 3/2 suppression

Symmetric Q Wave function

SLAC - E143

SMC

HERMES

SLAC - E155

CLAS-EG1b Q2 = 1.0 - 4.52 GeV2

SU(6)

pQCD

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Proton

Deuteron

W > 2; Q2 > 1

Valence spin structure functionValence spin structure functionCLAS12CLAS12

Valence spin structure functionValence spin structure function

Proton Deuteron W > 2; Q2 > 1

CLAS12CLAS12

Accurate measurement of Q2 dependence is key for extraction of ΔΔG(x)G(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 F2n(x,Q2) , d/u TMD Quark Distribution Functions in SIDIS

Form Factors and Resonance Excitations The Magnetic Structure of the Neutron – GMn

N* Transition Form Factors at high Q2

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 .

DVCSDVCS

Exclusive Vector mesonExclusive Vector meson

Large-x PDFsLarge-x PDFs

The CLAS12 detectorThe CLAS12 detector

A B C

Jefferson Lab Today

Large acceptance spectrometer electron/photon beams

Hall B

CLAS12 CLAS12

Central Detector

Forward Detector

Single sector (exploded view)Single sector (exploded view)

Beamline equipment

CLAS12

CLAS12CLAS12 Central DetectorCentral Detector

• Superconducting 5T Solenoid Superconducting 5T Solenoid Magnet, 78cm ø warm bore.Magnet, 78cm ø warm bore.

• Central Time-of-Flight array Central Time-of-Flight array (CTOF) (CTOF) ΔT < 60psec

• Silicon Vertex TrackerSilicon Vertex Tracker

3131

CLAS12 CLAS12 – – Solenoid, Solenoid, Torus Magnets Torus Magnets & Tracking Chambers& 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.

CLAS12CLAS12 – – PID & CalorimetryPID & Calorimetry

FTOF

FTOF: Timing resolution ΔT<80ps

PCAL

EC

Forward Carriage

LTCC

PCAL/EC: Electron, photon, neutron detection, high energy γ/π0 reconstruction. LTCC: Electron & pion separation. RICH: Needed for better Kaon id in some sectors.

Forward Central Detector Detector

Angular rangeCharged Particles 50 – 400 400 – 1350

Photons 20 – 400 N/AResolutionp/p (%) < 1 @ 5 GeV/c < 3 @ 0.5 GeV/c(mr) < 0.5 < 10(mr) < 0.5 < 6Photon detectionEnergy (MeV) >150 N/A (mr) 4 (1GeV) N/ANeutron detectionNeff 0.1 – 0.6 0.10Particle IDe/ Full range N/ApFull range ≤ 1.2 GeV/c/K Full range ≤ 0.65 GeV/cK/pGeV/c ≤ 0.90 GeV/cFull range N/A Full range N/A

Design Parameters (Base equipment) Design Parameters (Base equipment) CLAS12

Central Detector

Forward Detector

CLAS12CLAS12 in Hall B in Hall B

Moller polarimeterPhoton Energy tagging

systemPolarized targetsGoniometer/polarized photonsPair spectrometerBeam 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 AreaArizona State University (US) Beamline, Tagging SystemArgonne National Laboratory (US) Cerenkov CounterCalifornia State University (US) Cerenkov CountersCatholic University of America (US) SoftwareCollege of William & Mary (US) Calorimetry, Magnet MappingEdinburgh University (UK) Software Fairfield University (US) Polarized TargetFlorida International University, Miami (US) Beamline/Moller polarimeterGlasgow University (UK) Central Detector, DAQ, Forward Tagger, RICHGrenoble University/IN2P3 (France) Central DetectorIdaho State University (US) Drift chambers INFN –University Bari (Italy) tbd, interest in RICHINFN –University Catania (Italy) tbdINFN – Frascati and Fermi Center (Italy) Central Neutron Detector+ interest show in RICHINFN –University Ferrara (Italy) (will join in 2010) tbd, interest in RICHINFN – University Genoa (Italy) Central Neutron Detector+ interest in Forward TaggerINFN – ISS/Rome 1 (Italy) tbd, interest in RICHINFN – University of Rome Tor Vergata (Italy) Central Neutron Detector+ HD targetInstitute of Theoretical and Experimental Physics (Russia) SC. Magnets, SimulationsJames Madison University (US) CalorimetryKyungpook National University (Republic of Korea) CD TOFLos Alamos National Laboratory (US) Silicon TrackerMoscow State University, Skobeltsin Institute for Nuclear Physics (Russia) Software, SVT Moscow State University (High Energy Physics) (Russia) Silicon TrackerNorfolk State University (US) Preshower CalorimeterOhio University (US) Preshower CalorimeterOrsay University/IN2P3 (France) Central Neutron DetectorOld Dominion University (US) Drift ChambersRenselear Polytechnic Institute (US) Cerenkov CountersCEA Saclay (France) Central Tracker, Reconstruction softwareTemple University, Philadelphia (US) Cerenkov CountersThomas Jefferson National Accelerator Facility (US) Project coordination & oversightUniversity of Connecticut (US) Cerenkov CountersUniversity of New Hampshire (US) Central Tracker, Offline SoftwareUniversity of Richmond (US) Offline SoftwareUniversity of South Carolina (US) Forward TOFUniversity of Virginia (US) Beamline/Polarized TargetsYerevan 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