and Meson Production at JLab/CLAS Hyon-Suk Jo for the CLAS - - PowerPoint PPT Presentation
Deeply Virtual Compton Scattering and Meson Production at JLab/CLAS Hyon-Suk Jo for the CLAS collaboration IPN Orsay PANIC 2011 M.I.T. Cambridge - July 25, 2011 19th Particles & Nuclei International Conference Outline
Hyon-Suk Jo
for the CLAS collaboration
IPN Orsay PANIC 2011 – M.I.T. – Cambridge - July 25, 2011
19th Particles & Nuclei International Conference
Hyon-Suk Jo PANIC 2011 - M.I.T. – Cambridge - July 24-29, 2011 July 25, 2011
H(x,,t), E(x,,t) H(x,,t), E(x,,t)
~ ~
H(x,,t), E(x,,t) H(x,,t), E(x,,t)
~ ~
“handbag” diagram (high Q2, small t, fixed xB)
BH DVCS BH DVCS BH DVCS BH DVCS B
T T T T I I T T T T dtd dx dQ d
* * 2 2 2 2 4
with
interference term
GPDs
BH fully calculable in QED
(epep) =
2
DVCS and Bethe-Heitler (BH) experimentally undistinguishable interference between the 2 processes
DVCS is the most straightforward, theoretically cleanest reaction allowing to access the GPDs
Hyon-Suk Jo PANIC 2011 - M.I.T. – Cambridge - July 24-29, 2011 July 25, 2011
ep ep
LU LU
UT ~ cos Im{k(F2H – F1E) + ….. }d
= xB/(2-xB) k = t/4M2
LU ~ sin Im{F1H + (F1+F2)H -kF2E}d ~ UL ~ sin Im{F1H+(F1+F2)(H + xB/2E) –kF2 E+…}d ~
e’
p’ e
*
hadronic plane leptonic plane
q q
1 q
2 q
q
q q
2 q
Proton Neutron
LL ~ (A+Bcos Re{F1H+(F1+F2)(H + xB/2E)…}d
Hyon-Suk Jo PANIC 2011 - M.I.T. – Cambridge - July 24-29, 2011 July 25, 2011
~ ~
CEBAF : Continuous Electron Beam Accelerator Facility
Duty cycle 100% Emax5.8 GeV Pmax80%
Hall B
CLAS detector in Hall B
Hyon-Suk Jo PANIC 2011 - M.I.T. – Cambridge - July 24-29, 2011 July 25, 2011
(CC) (EC) (DC) (SC)
e’ p’
CC EC DC SC
DVCS/BH photon not detected with CLAS alone
epe’p’
The DVCS/BH photon is mostly emitted at forward angles
Hyon-Suk Jo PANIC 2011 - M.I.T. – Cambridge - July 24-29, 2011 July 25, 2011
Need an electromagnetic calorimeter at forward angles for DVCS experiments !
shielding the detectors from the Møller electrons
Part 1 of the e1-DVCS experiment:
Solenoid DVCS electromagnetic calorimeter
The e1-DVCS experiment (first experiment with CLAS dedicated to DVCS) with the CLAS detector + DVCS electromagnetic calorimeter + Solenoid
424 lead tungstate crystals + APD readout
Hyon-Suk Jo PANIC 2011 - M.I.T. – Cambridge - July 24-29, 2011 July 25, 2011
shielding the detectors from the Møller electrons
Solenoid DVCS electromagnetic calorimeter
424 lead tungstate crystals + APD readout
Hyon-Suk Jo PANIC 2011 - M.I.T. – Cambridge - July 24-29, 2011 July 25, 2011
The e1-DVCS data can be used to extract DVCS and DVMP Beam Spin Asymmetries and Cross Sections
The e1-DVCS experiment (first experiment with CLAS dedicated to DVCS) with the CLAS detector + DVCS electromagnetic calorimeter + Solenoid
Part 1 of the e1-DVCS experiment:
4-dimensional bins = (Q2, xB , -t, )
The kinematics of the DVCS reaction is defined by 4 independent variables :
Q2, xB, t and e’
p’ e
*
hadronic plane leptonic plane
Hyon-Suk Jo PANIC 2011 - M.I.T. – Cambridge - July 24-29, 2011 July 25, 2011
DVCS Beam Spin (ALU) and Longitudinal Target Spin (AUL) asymmetries
Hyon-Suk Jo PANIC 2011 - M.I.T. – Cambridge - July 24-29, 2011 July 25, 2011
integrated over t
F.X. Girod et al. (CLAS Collaboration),
F.X. Girod et al. (CLAS Collaboration),
<Q2>=1.82, <-t>=0.31, <>=0.16
Hyon-Suk Jo PANIC 2011 - M.I.T. – Cambridge - July 24-29, 2011 July 25, 2011 Previous CLAS results JLab Hall A results VGG twist-2 VGG twist-3 Regge (JML)
DVCS Beam Spin (ALU) and Longitudinal Target Spin (AUL) asymmetries
VGG model: Vanderhaeghen,Guichon,Guidal
Having both the beam-spin and longitudinal target-spin asymmetries, a nearly model-independent GPD analysis in leading twist was achieved fitting simultaneously ALU and AUL extracted with CLAS at 3 values of t and fixed xB
especially at lower t
ImH shows a steeper t-slope than ImH which would suggest that the axial charge is more concentrated than the electromagnetic charge
~ ~
Hyon-Suk Jo PANIC 2011 - M.I.T. – Cambridge - July 24-29, 2011 July 25, 2011
ImH ImH ~
Hyon-Suk Jo PANIC 2011 - M.I.T. – Cambridge - July 24-29, 2011 July 25, 2011
, [Kumericki and Mueller] (blue and green curves, black triangles)
red circles: fit with only H Indication that we can not neglect H
~
at High Momentum Transfer, Newport News, Virginia, 18-21 May 2010
2 W 0.8, p 45, 21 3 t
0.58, x 0.1 , Q
e B 2
e
1
Hyon-Suk Jo PANIC 2011 - M.I.T. – Cambridge - July 24-29, 2011 July 25, 2011
Q2 xB
The fast variation of the BH cross section: Around Φ=0 (where lies the BH singularity), there can be a factor ~2 between neighbouring kinematics The very fast variations of the BH cross section make the DVCS cross section analysis particularly difficult
4-dimensional bins = (Q2, xB , -t, )
2 independent analyses in progress JLab / IPN Orsay
Hyon-Suk Jo PANIC 2011 - M.I.T. – Cambridge - July 24-29, 2011 July 25, 2011
Q2 xB
2 W 0.8, p 45, 21 3 t
0.58, x 0.1 , Q
e B 2
e
1
4-dimensional bins = (Q2, xB , -t, )
H(x,,t), E(x,,t) H(x,,t), E(x,,t)
~ ~
H(x,,t), E(x,,t) H(x,,t), E(x,,t)
~ ~
“handbag” diagram (high Q2, small t, fixed xB)
Vector mesons ( w ) sensitive to H and E Pseudoscalar mesons ( ) sensitive to H and E
~ ~
DVMP allows quark flavor decomposition
Factorization proven
longitudinally polarized virtual photons
L 2 T
Q 1 ~
Hyon-Suk Jo PANIC 2011 - M.I.T. – Cambridge - July 24-29, 2011 July 25, 2011
ρ0 2u+d ω 2u-d ρ+ u-d 0 2u+d + u-d 2u-d
~ ~ conserve nucleon helicity H (x,ξ,t) H (x,ξ,t) E (x,ξ,t) E (x,ξ,t) flip nucleon helicity
e1-b (1999) e1-6 (2001-2002)
e1-DVCS (2005)
Hyon-Suk Jo PANIC 2011 - M.I.T. – Cambridge - July 24-29, 2011 July 25, 2011
Vector mesons: exclusive 0, w and electroproduction on the proton at CLAS 6 GeV:
There are also results on exclusive pseudoscalar meson electroproduction on the proton at CLAS 6 GeV:
w 0
Hyon-Suk Jo PANIC 2011 - M.I.T. – Cambridge - July 24-29, 2011 July 25, 2011
Hyon-Suk Jo PANIC 2011 - M.I.T. – Cambridge - July 24-29, 2011 July 25, 2011
b increases with W: valence quarks in the center of the nucleon and sea quarks at the periphery of the nucleon b decreases with Q2: by increasing the resolution of the probe, smaller objects in the nucleon can be seen
As a function of W, at fixed Q2, L first drops (W<5 GeV) and then slightly rises (W>5 GeV)
L p p L 0)
Hyon-Suk Jo PANIC 2011 - M.I.T. – Cambridge - July 24-29, 2011 July 25, 2011
VGG GPD model GK GPD model
Valence q Sea q and gluons
L p p L 0)
Hyon-Suk Jo PANIC 2011 - M.I.T. – Cambridge - July 24-29, 2011 July 25, 2011 VGG: Vanderhaeghen,Guichon,Guidal GK: Goloskokov,Kroll
The GPD models fail to reproduce the behavior at low W (W < 5 GeV)
Hyon-Suk Jo PANIC 2011 - M.I.T. – Cambridge - July 24-29, 2011 July 25, 2011
L p p L
L p p
L
+
Gluon GPDs Quark GPDs + Gluon GPDs GPD models fail to reproduce the behavior at low W (W < 5 GeV) for 0 w but succeed for which is only sensitive to gluon GPDs
GK: Goloskokov,Kroll
CHL-2
Add new hall
12 GeV
E= 2.2, 4.4, 6.6, 8.8, 11 GeV Beam polarization Pe > 80%
CLAS12
Upgrade of the instrumentation of the existing Halls
Continuous Electron Beam Accelerator Facility
Hyon-Suk Jo PANIC 2011 - M.I.T. – Cambridge - July 24-29, 2011 July 25, 2011
PCAL
Design luminosity L ~ 1035 cm-2s-1
Hyon-Suk Jo PANIC 2011 - M.I.T. – Cambridge - July 24-29, 2011 July 25, 2011
High luminosity Large acceptance Large kinematic coverage
Central Detector Forward Detector
H1, ZEUS
Valence region Sea/gluon region JLab 12 GeV Upgrade is well matched for GPD studies in the valence quark regime
Hyon-Suk Jo PANIC 2011 - M.I.T. – Cambridge - July 24-29, 2011 July 25, 2011
DVCS beam-spin asymmetry ALU on the Proton DVCS longitudinal target-spin asymmetry AUL on the Proton DVCS transverse target-spin asymmetry AUT on the Proton DVCS on the Neutron DVCS unpolarized and polarized cross sections DVMP: pseudoscalar mesons DVMP: vector mesons
Hyon-Suk Jo PANIC 2011 - M.I.T. – Cambridge - July 24-29, 2011 July 25, 2011
ep ep
80 days – 1035 Luminosity – VGG model
Hyon-Suk Jo PANIC 2011 - M.I.T. – Cambridge - July 24-29, 2011 July 25, 2011
Large acceptance: measurements in large Q2, xB, t ranges simultaneously ALU(Q2,xB,t) Δσ(Q2,xB,t) σ(Q2,xB,t)
Large acceptance: measurements in large Q2, xB, t ranges simultaneously ALU(Q2,xB,t) Δσ(Q2,xB,t) σ(Q2,xB,t)
ep ep
80 days – 1035 Luminosity – VGG model
Hyon-Suk Jo PANIC 2011 - M.I.T. – Cambridge - July 24-29, 2011 July 25, 2011
DVCS on Neutron is sensitive to the GPD En and the d-quark content
Hyon-Suk Jo PANIC 2011 - M.I.T. – Cambridge - July 24-29, 2011 July 25, 2011
t = -0.35 GeV2, Δt = 0.3 GeV2 Q2 = 2.75 GeV2, ΔQ2 = 1.5 GeV2 xB = 0.225, ΔxB = 0.15 Total of 588 bins in t, Q2, xB, This program requires adding a Central Neutron Detector (CND) to the CLAS12 base equipment
CND
Combined analysis of DVCS on Proton and Neutron allows flavor separation of GPDs
production in the valence region
reproduce it at lower Q2
quarks and/or gluons) which seem to be interpretable in terms of (kperp-modified) leading order handbag diagram (quark/gluon GPDs) BUT fail by large for W<5 GeV (valence region) except for which is only sensitive to gluon GPDs
for DVCS on a wider Q2 range, and to approach GPD validity regime for DVMP
models on a large xB scale and thus will be the ideal facility to study GPDs in the valence region and CLAS12 will be perfectly suited for a rich experimental GPD program
Hyon-Suk Jo PANIC 2011 - M.I.T. – Cambridge - July 24-29, 2011 July 25, 2011
Hyon-Suk Jo PANIC 2011 - M.I.T. – Cambridge - July 24-29, 2011 July 25, 2011
GPDs provide a correlation between the transverse position AND the longitudinal momentum
3D image of the nucleon Form factors: transverse position of quarks in the nucleon Parton distributions: longitudinal momentum of quarks in the nucleon
H(x,,t), E(x,,t) H(x,,t), E(x,,t)
~ ~
H(x,,t), E(x,,t) H(x,,t), E(x,,t)
~ ~ “handbag” diagrams (high Q2, small t, fixed xB)
*~ ~ conserve nucleon helicity H (x,ξ,t) H (x,ξ,t) E (x,ξ,t) E (x,ξ,t) flip nucleon helicity
Hyon-Suk Jo PANIC 2011 - M.I.T. – Cambridge - July 24-29, 2011 July 25, 2011
q
q
1 1
Quark angular momentum (Ji’s sum rule)
Cross-section measurement and beam-charge asymmetry (ReT ) integrate GPDs over x Beam- or target-spin asymmetries are proportional to ImT, therefore to GPDs at x = and x = -
At leading order
Hyon-Suk Jo PANIC 2011 - M.I.T. – Cambridge - July 24-29, 2011 July 25, 2011
x
real part imaginary part
1 1 1 1
) , , ( ) , , ( ~ ) , , ( ~ t H i dx x t x H P dx i x t x H T DVCS
VGG model: Vanderhaeghen,Guichon,Guidal
(CC) (EC) (DC) (SC)
Angular coverage
8°< <140° (DC + SC)
8°< <45° (EC) Resolution dp/p1% d, dmrad
Hyon-Suk Jo PANIC 2011 - M.I.T. – Cambridge - July 24-29, 2011 July 25, 2011
Regge (Laget)
L(
L p p L 0)
Hyon-Suk Jo PANIC 2011 - M.I.T. – Cambridge - July 24-29, 2011 July 25, 2011
Pomeron ,F2
DDs + “meson exchange” DDs w/o “meson exchange” (VGG) “meson exchange”
L p p L 0)
Hyon-Suk Jo PANIC 2011 - M.I.T. – Cambridge - July 24-29, 2011 July 25, 2011
Hyon-Suk Jo PANIC 2011 - M.I.T. – Cambridge - July 24-29, 2011 July 25, 2011
Hyon-Suk Jo PANIC 2011 - M.I.T. – Cambridge - July 24-29, 2011 July 25, 2011
DVCS on Neutron is sensitive to the GPD En and the d-quark content
This program requires adding a Central Neutron Detector (CND) to the CLAS12 base equipment
CND
Combined analysis of DVCS on Proton and Neutron allows flavor separation of GPDs