Electroproduction of po in the D1232 region

1
Hall B 12 GeV Physics Program and Upgrade Plan
Volker D. Burkert Jefferson Lab

• Introduction
• The Equipment Plan
• Initial Physics Program
• Summary
• Equipment Options

PAC27 Meeting on the 12 GeV Upgrade, January
10-11, 2005
2
Initial Physics Program in Hall B at 12 GeV

• GPDs and 3D-Imaging of the Nucleon
• Deeply Virtual Compton Scattering -
  DVCS/DDVCS/DVCS
• Deeply Virtual Meson Production - DVMP
• High-t p0/h Production

• Valence Quark Distributions
• Proton and Neutron Spin Structure
• Neutron Structure Function F2n(x,Q2)
• Quark Distribution Functions in Semi-Inclusive
  SSA
• Flavor-tagged Quark Distribution Functions

• Form Factors and Resonance Excitations
• The Magnetic Structure of the Neutron GMn
• ND Transition at high Q2 - GM, REM, RSM
• High-mass N Resonance Excitation

• Hadrons in the Nuclear Medium
• Space-Time Characteristics of Quark
  Hadronization
• Color transparency
• Structure of bound Neutrons

• Hadron Spectroscopy with quasi-real Photons

3
Requirements for Hall B Upgrade

• High statistics capabilities for
  exclusive/semi-inclusive
• processes at electron energies up to 12 GeV
• Complement missing mass techniques by more
  complete
• detection of hadronic final state
• Increase operating luminosity to L gt 1035
  cm-2sec-1
• Extend particle ID to higher momenta (e-/p-,
  p/K/p, g/po)

• Upgrade the existing Forward Detection system
• - replace DCs by smaller chambers with reduced
  cell sizes
• - implement high-threshold Cerenkov detector pp
  gt 5 GeV/c
• - improve TOF resolution to 60psec
• - increase calorimeter granularity for po/g
  separation

4
CLAS12
Preshower EC (not visible)
Forward EC
Low Threshold Cerenkov Counter (LTCC)
Forward TOF
Forward Drift Chambers
Torus Coils
High Threshold Cerenkov(HTCC)
Central Detector
Inner EC (not visible)
Beamline
Coil EC
5
CLAS12
Beamline
6
Utilization of Existing Hall B Equipment

• Re-use many existing components from CLAS
• Forward electromagnetic calorimeters
• Low threshold gas Cerenkov counters
• Time-of-flight scintillators
• Drift chamber electronics and gas system
• Lead-tungstate DVCS small angle calorimeter
• DAQ and readout electronics

7
CLAS12 - Forward Detector Upgrades

• Replace Region 1, Region 2, Region 3 drift
  chambers
• gt simplified geometry compared to
  current DCs,
• factor two smaller cell sizes
• Time-of-flight detector with improved timing
  resolution
• Forward calorimeter gt extend g/p0 separation
  to higher momenta
• instrument coil regions with calorimetry
  (PbWO4)
• New Cerenkov Detector with high pion threshold
  5GeV
• Microstrip detector (part of CD)

8
CLAS12 HTCC
High Threshold Cerenkov Counter
Radiator Gas CO2
Winston cones PMTs
mirror
photo electrons
q(o)
f (o)
9
CLAS12 - Electron/pion separation
e- and p- inclusive cross sections and expected
trigger rate
L 1035cm-2sec-1
EC
x 0.01
ECLTCC
pp-
x 0.1
ECLTCCHTCC
x 0.1
10
CLAS12 Forward Drift Chambers
3 Regions Planar trapezoids 36 Layers (12
axial, 24 stereo) Hexagonal cell geometry
Cell radius 0.35 1.0 cm Time window 100
250 nsec
u - layer
v - layer
w - layer
11
CLAS12 FD Time-of-Flight Detectors
PMTs
Scintillators
Re-use scintillator from CLAS
12
CLAS12 - Preshower Calorimeter
Scintillator/lead sandwich, with wavelength
shifting fiber readout, 4 rad. length.
3.5cm
Lead sheets 1mm thick
Wavelength Shifting Fibers embedded in
scintillator
13
CLAS12 Torus Coils Coil EC
DVCS calorimeter 424 PbWO4 crystals
New Torus coil geometry
EC possible candidate PbWO4 w/ APD readout
DVCS EC
14
CLAS12 Inner Calorimeter
DVCS calorimeter 424 PbWO4 crystals
15
CLAS12 Central Detector
16
Magnetic Field Distribution in Flux Return Iron
Flux Return Iron
Solenoid Coil
Central B-Field 5 Tesla
(Gauss)
17
Moller Electrons in Target Region
L1035cm-2s-1, DT 250nsec
L1033cm-2s-1, DT 250nsec
without solenoid field
L1035cm-2s-1, DT 250nsec
HTCC
18
CLAS12 CD Calorimeter
Tungsten-SciFi
Polar angle
Axial fibers
PMTs
fibers
Prototype with 5,500 fibers under testing.
Fiber readout
19
CLAS12 - CD Time-of-Flight
TOF Lightguide
Flux return
TOF Lightguide
Central TOF
Scintillator
additional particle id from DEscint
Currently being prototyped at KNU (South Korea)
20
CLAS12 Central Tracking Detector
pitch 100-300mm
readout
Cathode Pad Chambers - 20 pads in
azimuth/sl - 40 pads parallel to beam/sl
- 160 anode wires - 1600 cathode
pads read out
Silicon micro strip

• forward track reconstruction
• large angle tracking
• - high rate operation near target

21
CLAS12 - Central Detector
High Q2, low t ep eKS0(gL(pp-)) event
22
CLAS 12 - Expected Performance
Forward Detector Central Detector Angular
coverage Tracks (inbending) 8o - 37o 40o
- 135o Tracks (outbending) 5o - 37o 40o -
135o Photons 3o - 37o 40o - 135o Track
resolution dp (GeV/c) 0.003p 0.001p2
dpT0.03pT dq (mr) lt 1 (gt2.5 GeV/c) 8
(1 GeV/c) df (mr) lt 3 (gt 2.5 GeV/c) 2
(1 GeV/c) Photon detection Energy range gt 150
MeV gt 60 MeV dE/E 0.09 (1 GeV) 0.06 (1
GeV) dq (mr) 4 (1 GeV) 15 (1
GeV) Neutron detection heff 0.5 (EC), 0.1
(TOF) 0.025 (TOF) Particle id e/p
gtgt1000 ( lt 5 GeV/c) gt100 ( gt 5
GeV/c) p/K (4s) lt 3 GeV/c (TOF) 0.65
GeV/c 3 - 10 GeV/c (CC) p/p (4s) lt 5
GeV/c (TOF) 1.2 GeV/c 3 - 10 GeV/c
(CC) K/p(4s) lt 3.5 GeV/c (TOF) 0.9 GeV/c

23
CLAS12 GPDs
Target LH2 Beam E 11/8.8/6.6 GeV, Pe gt 0.70 L
gt 1035cm-2s-1
Processes measured concurrently
Description
Reaction
ep epg ep epee- (mm-) ep
e(D,N)g ep ep(r,w,f) ep
eN(p0,h,p) ep eN(p0,h,p) ep
e(p,p0,h,K)X ep eN(p0,p) ep
eN(h,pp-,w)
DVCS, DVMP, internal qq (twist-2), qGq
(twist-3), spin dynamics, proton tomography
GPDs, H, xx
Q2 1.5 8 GeV2
GPDs, -xltxltx
xB 0.05 0.9
N transition GPDs
GPDs spin/flavor separation
t 0.051.5 GeV2
hard meson production short distance dynamics
GPDs _at_ high t
t lt 10 GeV2
quark transverse momentum-dependent
distributions (TMD)
twist-3 distr. functions,
z 0.3 - 0.9
quark core excitation 3-quark confinement
Q2 3.0 12
ND - REM, RSM high mass N
W 1.13.0 GeV
24
CLAS12 - GPDs Spin Structure
Target Polarized H/D Beam E 11/8.8 GeV, Pe gt
0.70 Pp0.75,PD0.35 L gt 2x1035cm-2s-1
Processes with same target measured concurrently
A1p, g1p, G1p
proton spin structure neutron spin structure
e p eX e D eX
A1n, g1n, G1n
ep epg
DVCS/BH target SSA
H
GPDs
e p epg
H, E
H, E,
DVCS/BH double asym.
Q2 1.5 8GeV2
DVMP target SSA
e p eN(p0,h,p)
GPDs
H, E
xB 0.05 0.7
e p eN(p0,h,p)
DVMP/BH double asym.
z0.05-0.95
Q2 1.5 8GeV2
sinf
ep e(p,p0,h)X
Ddv/dv
AUL
quark flavor tagging
xB 0.05 0.7
eD e(p/-,p0,h)X
z0.05-0.95
25
CLAS12 GPDs p/n spin structure
Target Polarized H/D Beam E 11 GeV, Pe gt
0.70 Pp0.75,PD0.35 L gt 2x1035cm-2s-1
Processes measured concurrently on NH3 or ND3
Kinematics
Physics quantity
Physics description
Reaction
g2p, G2p
proton spin structure neutron spin structure
epT eX eDT eX
g2n , G2n
Q2 1.5 6GeV2
sinf
xB 0.05 0.7
AUT
epT e(p,p0,h,K)X
quark transversity
du/u
z0.2-0.95
sinf
Quark flavor contribution to proton spin
epT epr0, epT enr(pp0)
Q2 1.5 8GeV2
AUT
xB 0.05 0.7
z0.3-0.95
enT epr-
Quark flavor contribution to neutron spin
Q2 1.5 6GeV2
sinf
AUT

26
CLAS12 - Neutron Structure
Processes measured concurrently
Kinematics
Physics quantity
Reaction
Q2 1.5 8GeV2
S.F. of free neutron neutron resonances
F2n(x,Q2) A1/2,A3/2 (Q2)
eD epsX eD eps(p-p),Dp-
o
o
xB 0.1 0.90
GPD H(x,x,t)
eD eDg eD eps(D0,N)g
DVCS, DDVCS
Q2 1.5 8GeV2
GN(t)
twist-3 distribution functions
eD e(m,g)X
Q2 1.5 8GeV2
e(x)
xB 0.1 0.6
eD e(n,p) ep epn
neutron magnetic form factor
Q2 4 14GeV2
GMn(Q2)
color transparency in coherent VM production
eD eD(r,w,f)
ds(t1)/ds(t2) vs Q2
Q2 1.0 6GeV2
color transparency at fixed coherence length
sA/AsN
eD e(r,w,f)X
27
CLAS12 Hadronization
Target Nuclear Beam E 11/8.8/6.6 GeV, Pe gt
0.70 L gt 1035cm-2s-1
Processes measured concurrently
Kinematics
Physics quantity
Physics description
Reaction
Q2 2 - 9 GeV2 n 2 9 GeV z 0.3 0.9
e2H e hadrons X
space-time characteristics of
hadronization (DIS kinematics)
Hadronization length vs. Q2, v, pT, z, hadron
mass and size, and quark flavor quark energy
loss, gluon emission properties, quark-gluon
correlations
e14N e hadrons X
e56Fe e hadrons X
e84Kr e hadrons X
e197Au e hadrons X
Detect all hadrons
color transparency in r production from complex
nuclei
e14N erX
color transparency at fixed coherence length
Q2 2 8 GeV2
e56Fe erX
28
CLAS12 Hadron Spectroscopy
With small angle electron tagger (may exist
before the Upgrade)
Kinematics
Physics quantity
Physics description
Reaction
g4He 4He m0
Mmeson lt 2.5GeV
Exotic mesons w/o baryon contamination
Partial waves
gH2 N m
Meson spectroscopy
s0, sLT
g3He 3H m
Exotic Mesons
Partial waves
Partial waves
g3H 3He m-
Exotic Mesons
B/M Spectroscopy Frozen spin target
MB, MM lt 2.2GeV
s0, Asymmetries
gH/D Nmesons
29
Deeply Virtual Exclusive Processes Kinematics
Coverage
CLAS12
30
Modeling of the GPDs
31
Deeply Virtual Exclusive Processes
DVMP
DVCS
long. only
hard gluon
hard vertices
All four GPDs may contribute, Separate GPDs using
beam/target polarization.
32
CLAS - DVCS/BH Beam Asymmetry
Longitudinal beam polarization.
Beam spin asymmetry
e p epg

-
sUL-sUL
ALU
-

sULsUL

DsLU KF1(-t) H ..
Fit AUL asinf bsin2f
a - twist-2

H(x,x,t)
Access to GPD
33
CLAS - DVCS/BH Beam Asymmetry
Longitudinal beam polarization.
E5.75 GeV
Beam spin asymmetry
e p epg

-
sUL-sUL
ALU
-

sULsUL

DsLU KF1(-t) H ..
Fit AUL asinf bsin2f
a - twist-2

H(x,x,t)
Access to GPD
34
CLAS12 - Acceptance for DVCS
E 11 GeV
ep epg
Q2 gt 2.5 GeV2
Central Detector
Forward Detector
35
CLAS12 Acceptance for DVCS
Ee 11 GeV, xB 0.325-0.375
ep epg
EC
IEC
DVCS photons need detection for Qg gt 2o
EC
EC
IEC
IEC
36
DVCS/BH- Beam Asymmetry
Ee 11 GeV
37
DVCS/BH- Beam Asymmetry
Ee 11 GeV
38
CLAS12 - DVCS/BH Beam Asymmetry
E 11 GeV
Selected Kinematics
39
CLAS12 - DVCS/BH Beam Asymmetry
E 11 GeV
Selected Kinematics
40
CLAS - DVCS/BH Target Asymmetry
Longitudinal target spin polarization.
41
CLAS12 - DVCS/BH Target Asymmetry
E 11 GeV
Selected Kinematics
Longitudinal polarized target

• L 2x1035
• T 2000 hrs
• DQ2 1GeV2
• Dx 0.05

42
CLAS12 - DVCS/BH Target Asymmetry
E 11 GeV

• L 2x1035
• T 2000 hrs
• DQ2 1GeV2
• Dx 0.05

Selected Kinematics
43
CLAS12 - DVCS/BH Target Asymmetry
E 11 GeV
Selected Kinematics
Transverse polarized target
GPD H and E enter in Jis spin sum rule.
44
Double DVCS (DDVCS)
45
CLAS12 Acceptance for DDVCS
e
e-
e-
p
46
CLAS DDVCS/DVCS
CLAS _at_ 5.75 GeV
DDVCS
ep e-pee-
Open issue Increase operating luminosity to
1036 cm-2sec-1?
m
47
GPDs - Deeply Virtual Meson Production
gLp pr0(pp-)/w(pp-p0)
Access Eu,d, Hu,d
HERMES (27GeV)
W5.4 GeV
48
CLAS12 L/T Separation ep epro (pp-)
xB 0.3-0.4 -t 0.2-0.3GeV2
sL
sT
Other bins measured concurrently
49
CLAS12 - r0/w with transverse target
2 D (Im(AB))/p
Asymmetry depends linearly on the GPD E, which
enters Jis sum rule. At high xB
strong sensitivity to u-quark contributions.
T
AUT -
A2(1-x2) - B2(x2t/4m2) - Re(AB)2x2
w has similar sensitivity to proton quark spin
50
CLAS12 - Pseudoscalar Meson Production
ep enp
s
s
Rosenbluth separation for
/
L
T
x
0.4-0.5
other bins at
B
-t 0.2-0.4GeV
2
the same time
s
L

• dsL/dt expected to be dominant
• at large Q2 and small t.
• dependence of ds/dt shows
• size of power corrections.

s
TOT
s
T
51
CLAS - Neutron Magnetic Form Factor
M. Diehl, T. Feldmann, R. Jacob, P. Kroll,
hep-ph/0408173 Accurate data on GMn lacking in
GPD fit to high t form factor data.
52
CLAS12 - Neutron Magnetic Form Factor
CLAS12
M. Diehl, T. Feldmann, R. Jacob, P. Kroll,
hep-ph/0408173 Accurate data on GMn lacking in
GPD fit to high t form factor data.
53
CLAS12 - ND(1232)
Short distance behavior of 3-quark excitation
Dressed quark mass
LQCD/DSE/Instantons
gp ppo(gg)
54
CLAS N Photo-/Electroproduction
gp ppp-
Q20
W(GeV)
55
CLAS12 Kinematics for N Physics
E11 GeV qmax400
missingN states
E5.75 GeV qmax400
56
CLAS12 Semi-Inclusive DIS

• Beam asymmetry probes twist-3 DFs.

L2x1035cm-2s-1 T1000 hrs, xB 0.28-0.32 pT
0.4 0.6 GeV/c z 0.4 0.6
Selected Kinematics
ep epX
57
CLAS Longitudinal Target Asymmetry
ep ep/-,0 X
5.75 GeV
Curves Efremov et al (no Sivers contribution)

• First measurement of non-0 effect SIDIS p-
  production
• for longitudinally polarized proton target.

58
CLAS12 Semi-Inclusive DIS
59
CLAS12 - Structure of Neutrons
e-
e-
Requires detection of a slow recoil proton at
backward angles and with momenta 60-150MeV/c
Measure Q2 dependence simultaneously
60
CLAS12 - Structure of Neutrons
The technique opens up new possibilities for the
study of free neutron properties - inclusive
spectrum of neutron resonances (most
resonances are not seen in inclusive
scattering off even light nuclei) - PWA for
meson production on neutrons, e.g. epp-,
enpp-, epp-p0 - electrocoupling amplitudes of
resonance transitions, test single quark
transition hypothesis - deeply virtual
exclusive scattering on neutrons
e-
e-
Requires detection of a slow spectator proton at
backward angles and with momenta 60-150MeV/c
Measure Q2 dependence simultaneously
61
CLAS12 DIS Polarization Asymmetries
62
CLAS12 Light Nuclei
E 11 GeV
250 hrs _at_ 2x1035cm-2s-1
63
CLAS12 Quark Hadronisation
64
CLAS12 - Exotic Meson Production off Nuclei

• Coherent meson production off nuclei is a clean
  way of eliminating background from s-channel
  baryon resonances simplifies significantly PWA
  analysis.

Requires electron scattering at Qe 0o

• Combined measurements on light nuclei
• 4He, 3He, and 3H, will give access to all
• isospin combinations of given final state.

65
CLAS12 Summary

• World-wide the only full acceptance detector
  forfixed target electron scattering experiments,
  with high
• luminosity capability, the detection of high
  multiplicity
• final states with charged and neutral particles,
  use of
• polarized solid state targets. It can also
  provide the basis
• for discovery.
• Broad program of GPDs and nucleon tomography
  through the
• measurement of deeply virtual exclusive
  processes.
• Broad program in DIS and SIDIS spin physics.
• High Q2 baryon resonance program (N,D)
• Broad program of hadronization in nuclear
  medium.
• Low Q2 meson and baryon spectroscopy.