gep experimentwm-jlab.physics.wm.edu/mediawiki/images/0/0a/bogdan_gep-compressed.pdf · the front...
TRANSCRIPT
GEP experiment
B. Wojtsekhowski for the collaboration
1. Development of GEP-5
2. GEp related physics
slide 1
GEP-15
Large Acceptance Proton Form Factor Ratio Measurement at 13 and 15 GeV
2
Using Recoil Polarization Method
C.Perdrisat, L.Pentchev, E.Cisbani, V.Punjabi, B.Wojtsekhowski with more than 100 collaborators from almost 30 institutions
from the 2007 PAC presentation, slide 2
Outline of the talk
• Physics goals
• Experiment
• Method
• Analysis
• Tracking technology
• Budget /Road map
• Other applications
• Beam time request
from the 2007 PAC presentation, slide 3
from the 2007 PAC presentation, slide 4
Physics Goals: ratio F2 / F1
• Significantly increase the
Q2 range up to 15 GeV2
• Study the spin flip part of the hadron current
• Constrain GPDs at high t
• Provide critical test of the FF models and reaction dynamics
JLab measurements
Plan for GEP-15 GEP-I, II, III
BJY(03)
from the 2007 PAC presentation, slide 5
What is new in this experiment?
1. Large solid angle in the proton arm at a small scattering angle achieved with a single dipole magnet. The beam line will go through a hole in the magnet pole.
2. Gas Electron Multiplier chambers to handle high rate of the background. Similar counting rates handled in COMPASS; rate will be much higher in LHCb.
3. High threshold trigger with hadron calorimeter.
from the 2007 PAC presentation, slide 6
Challenges in this experiment
Need large statistics ! max luminosity and solid angle
Max luminosity ! large background Large solid angle ! small bend ! huge background
Solution is a modern tracking detector based on Gas Electron Multiplier (F. Sauli, 1997)
from the 2007 PAC presentation, slide 7
Proton Arm
- Magnet: 48D48 - 46 cm gap, 3 Tm field integral, 100 ton - solid angle is 35 msr for GEP, could be ~70 msr at larger angle GEM chambers for tracking with 70 µm resolution - momentum resolution is 0.5% for 8.5 GeV/c proton - angular resolution is 0.3 mrad - trigger threshold is 4 GeV from hadron calorimeter
Calorimeter response for 10 GeV protons from test for Compass experiment"
Top view A-A"
SBS components (in GEp /GM
p )
128 inch
63 inch
CC1
CC2
48D48
+/! 25 mr
Beam
Target
Proton
Electron
228 inch
CH2
Hadron
Calorimeter
GEM
10!20 Gauss
SiFiber
Calorimeter
Lead!glass
INFN BNL NSF D0 / SMU
Dubna (COMPAS) BigCal ITEP (HERA-B)
48D48
+/- 25 mrad
1 - 2 Gauss
2009 plan
from the 2009 meeting with B.Tippens & B.Keister, slide 8
E12-07-109: Large Acceptance Proton Form Factor Ratio Measurement at
13 and 15 GeV2 Using Recoil Polarization Method
C.Perdrisat, L.Pentchev, E.Cisbani, V.Punjabi, B.Wojtsekhowski
Scientific case
H(�e, e��p)
x < 0.1 x ~ 0.3 x ~ 0.8
FFs
GPDs
DIS
DVCS DVMP
RCS
dσ = dσNS
�
ε(G̃E
+s − u
4M2F̃3)
2 + τ (G̃M
+ εs − u
4M2F̃3)
2
�
Gp
E
Gp
M
|1−γ
= −Px
Pz
Ee+Ee�
2Mptan(θe/2)
ρ(�b) ρ(�b, x)
two-photon effect +
< 2%
IMF densities
from the 2010 PAC presentation, slide 9
2 in GeV2Q
0 5 10 15
p M/G
p EG
pµ
-0.5
0.0
0.5
1.0
GEp(1)
GEp(2)
GEp(3) (prelim, stat only)
GEp(5) E12-07-109, SBS
VMD - E. Lomon (2002)
VMD - Bijker and Iachello (2004)
RCQM - G. Miller (2002)
DSE - C. Roberts (2009)
= 300 MeV!, 2)/Q2!/2(Q2 ln"
1/F
2F
E12-07-109: Large Acceptance Proton Form Factor Ratio Measurement at
10 and 14.5 GeV2 Using Recoil Polarization Method
E.Brash, E.Cisbani, M.Jones, M.Khandaker, L.Pentchev, C.Perdrisat, V.Punjabi, B.Wojtsekhowski
Expected results
Q2 Ebeam beam time pp θSBS Ee θBigCal ∆ [ µGpE/Gp
M]
GeV 2 GeV days GeV deg GeV degoptics 6.6 4 28.0
5.0 6.6 1 3.48 28.0 3.94 26.3 0.02310.0 8.8 10 6.20 16.7 3.47 35.3 0.06514.5 11. 45 8.61 12.0 3.27 39.0 0.135
2 in GeV
2Q
0 5 10 15
)2
!/2
(Q2
ln
2Q
p 1
F
p 2F
0.15
0.2 = 300 MeV!
= 500 MeV!
BJY: quark OAM
RCQM, DSE calculations; lQCD progress
Total 60 days: beam time + kin. changes ( as in 2007)
ln2(Q
2/(
30
0 M
eV
)2)
E12-07-109: Large Acceptance Proton Form Factor Ratio Measurement at
10 and 14.5 GeV2 Using Recoil Polarization Method
Technical progress
The Super Bigbite in GEp: - SBS magnet - SBS trackers - Hadron calorimeter - Trigger and DAQ The BigCal (electron arm)
Funding, construction, progress
1. GEM trackers design – INFN $1.1M Front tracker construction
2. Funding proposal to DOE 11/2009 JLab+UVa+W&M+NSU+CMU+RU+ total of $3.8M 3. Technical Review 1/22/2010 http://hallaweb.jlab.org/12GeV/
SuperBigBite/SBS_CDR/ 4. AY measurement at Dubna
Hadron Calorimeter
Beam Line
Pol. GEM Trackers
Front GEM Tracker
BNL Magnet
Field Clamp
Scattering Chamber
from the 2010 PAC presentation, slide 11
E12-07-109: Large Acceptance Proton Form Factor Ratio Measurement at
10 and 14.5 GeV2 Using Recoil Polarization Method
PAC report slide 12
E12-07-109: Large Acceptance Proton Form Factor Ratio Measurement at
08 and 12.0 GeV2 Using Recoil Polarization Method
Updated plan slide 13
Projected Errors based on projected detector performance and general setup
1st order Resolution
1st Order P = 8
! (%) 0.03p+0.29 0.53
"tar (mrad) 0.09 + 0.59/p 0.16
ytar (mm) 0.53 + 4.49/p 1.09
#tar (mrad) 0.14+1.34/p 0.31
from the 2010 LeRose’s analysis, slide 14
Momentum Dependence of $%
0
0.2
0.4
0.6
0.8
1
1.2
0 2 4 6 8 10 12
P (GeV/c)
Super BigBite Relative
Acceptance !"#$%&
'"
("#$%&
'"
15
Parameters
Solid angle =>
Resolution:
Momentum =>
Angular =>
Momentum acceptance =>
Target length (y)
σp
P= 0.0029 + 0.0003 × p[GeV]
σθ
= 0.14 + 1.3/p [GeV], mrad
unlimited above 1-2 GeV/c
50 cm
16
Angle with
Beam, deg
Solid angle,
msr
Distance,
meters
Horizontal
range, deg
Vertical
range, deg
7.5 30 3.2 +/- 3.0 +/- 8.0
15 72 1.6 +/- 4.8 +/- 12.2
30 76 1.5 +/- 4.9 +/- 12.5
SBS design parameters:
17
GEANT3 Simulations of Background Rates
• GEANT3 code with 100 keV threshold for tracking • Model includes the target, scattering chamber, magnet, SBS detectors (with COMPASS type GEM), BigCal, beamline, beam dump
Several configurations were studied: ! Target only ! Target + scattering chamber ! + magnet, field clamps, lead
shielding ! + beam line and beam dump
18
Bz = 8, Bx = 0.07
Pb
Clamp (iron)
Magnet
cell
Snout
Window
0.05
B=14 kG
4
Beam line field region
Pb
Local shielding must be thick
Minimize transverse magnetic field on the beam line
Minimize material on the beam line in direct view of the detector
from the 2010 Pentchev’s analysis, slide 19
MC Background Results: First GEM chamber
Configuration
Ebeam = 11 GeV, 75 µA
# rates
(MHz/cm2)
# induced hits
(MHz/cm2)
Charged rates (MHz/cm2 )
Target 115 0.351 0.101
Target + Scatt. chamber 118 0.361 0.101
Target + Scatt. Ch. + Magnet 143 0.437 0.119
• Initial soft electrons swept by the magnet
• Photons originate from the target or from electrons hitting material in front of the magnet
First GEM chamber:
Technical Review 2: Summary Paul Brindza, Eugene Chudakov, Dave Doughty, Bernhard Ketzer, Bernhard Mecking (chair), and Maxim Titov
from the report Feb. 2010 TR2, slide 20
Updated CDR – July 2011
from the 2011 CDR, slide 21
" MC simulations for GEp, GEn, GMn " GEM tracker data
Background contribution [%]0 20 40 60 80 100
Str
ips o
ccu
pan
cy
[%]
0
10
20
30
40
50
60
70
80
Raw
D
+ D!
Occupancy for various filter options
After signal shape analysis, strip occupancy is ~ 10%. Hit rate is ~ 500 kHz/cm2
Plane z [m]
0 0.2 0.4 0.6 0.8
Hit
x [
m]
-0.004
-0.003
-0.002
-0.001
0
0.001
0.002
0.003
489490491492493494495496497498499500501502503504505506507508509
Event 4 , Ntracks = 1
Plane z [m]
0 0.2 0.4 0.6 0.8
Hit
y [
m]
-0.003
-0.002
-0.001
0
0.001
0.002
0.003
616
617618
619620
621
622623
624625
626627
628629
630
631632
633
Real track
Reconstr track
= 4.6 / NDF = 72!
Event display for the front tracker: six GEM planes
A generated proton track (red line)
A reconstructed track (blue line)
Accidental hits
from the 2011 CDR, slide 22
x [mm]
-0.4 -0.2 0 0.2 0.40
5
10
15
20
25100 % background
MC-XtrackX
y [mm]
-0.4 -0.2 0 0.2 0.4
MC-YtrackY
[mrad]
0
5
10
15
20
25
30
35MC
-track
[mrad]
0
5
10
15
20
25
30
35
40
MC-
track
210-1-2 210-1-2
Track reconstruction efficiency, GEp(5) Track reconstruction accuracies
“The initial experimental program consists of three nucleon form factor experiments that have been approved by the JLab PAC. It is obvious to the Committee that the SBS will become the instrument of choice for a large variety of other important physics
problems requiring small-angle coverage, high luminosity, and modest resolution.” Second Technical Review, final report (October, 2011)
-0.4 -0.2 0 0.2 0.4
∆x [mm]
-2 -1 0 1 2
∆θ [mrad]-2 -1 0 1 2
∆φ [mrad]
-0.4 -0.2 0 0.2 0.4
∆y [mm]
Background contribution [%]0 20 40 60 80 100
Tra
ck
ing
eff
icie
nc
y
[%]
0
20
40
60
80
100
D
R
+ D!
+ R!
+ R + D!
Efficiency for various filter options
% of GEp(5) luminosity
90%
Updated CDR – July 2011
DOE Review
23
10/10/11 10:07 AM
Page 1 of 3http://hallaweb.jlab.org/12GeV/SuperBigBite/Dry_Run/
DOE combined science/technical review including cost andschedule
for the Super Bigbite Spectrometer
The project plans (PMP and RMP) are available here PMP and here RMP
The additional review documents are available in this window
Preliminary agenda of the STC Review of the SBS project
October 13-14, 2011 - from 8:00 AM, JLAB CC, room F113
October 13, 2011 - from 8:00 AM, JLAB CC, room F113
08:00 - 08:50 Executive Session
08:50 - 09:00 Welcome McKeown
09:00 - 09:15(10+5)
Introduction and Overview Ent slides
09:15 - 10:15(40+20)
Physics Motivation Overview Cates slides outline
10:15 - 10:45(20+10)
Neutron Form Factor Measurements Riordan slides outline
10:45 - 11.00 Break
11:00 - 11:30(20+10)
Proton Charge Form FactorMeasurement
Cisbani slides outline
11:30 - 12:00(20+10)
SIDIS and Other Physics de Jager slides outline
12:00 Lunch (one hour)
1:00 - 1:45 (30+15) SBS Project Overview Wojtsekhowski slides outline
10/10/11 10:07 AM
Page 2 of 3http://hallaweb.jlab.org/12GeV/SuperBigBite/Dry_Run/
1:45 - 2:15 (20+10) Magnet and Infrastructure Wines slides outline
2:15 - 2:45 (20+10) GEM Detectors Liyanage slides outline
2:45 - 3:15 (20+10) Calorimetry Franklin slides outline
3:15 - 3.30 Break
3:30 - 4:00 (20+10) DAQ and Trigger Electronics Camsonne slides outline
4:00 - 4:30 (20+10) Project Management, Cost andSchedule
LeRose slides outline
4:30 - 4:45 (10+5) Collaboration Management de Jager slides outline
4:45 - 5.00 Break
5:00 - 6.00 Executive Session
6:30 Reception
October 14, 2011 - from 8:00 AM, JLAB CC
Breakoutsessions
09:00 - 11:30 Magnet/Intrastructure/Integration roomF113
Michaels, Gavalya, Wines, deJager
09:00 - 11:30 GEM Detectors and Electronics roomB207
Cisbani, Camsonne, Franklin,Liyanage
09:00 - 11:30 Project Management roomF227
LeRose, Khandaker, Wells,Cates
09:00 - 11:30 Physics roomF326-327
Wojtsekhowski, Jones, Riordan(Cates, de Jager)
Wrapup
DOE approval
24
DOE report: Summary Executive Summary
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DOE report: Summary
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26
DOE report: Summary Calorimeters and Other Off-Project Components
Findings:
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Recommendations:
‚ R(+&
#
27
GEP development
28
- Collaboration efforts, meetings: http://hallaweb.jlab.org/12GeV/SuperBigBite/
- Detector design / construction - “should” items from the DOE report - a few technology updates
- Research Management Plan: MOUs, …
GEP development
29
‒
!
!"#$%&'%$()*+,-./+,0$
ID # Level Milestone Scheduled
Date Expected
Date Actual Date
1.1-01M 1 Project start 10/1/2012 10/1/2012 10/1/2012
1.2-01M 2 Magnet delivered to JLab 4/30/2013 4/30/2013
1.2-10M 2 Platform parts received 6/27/2014 6/27/2014
1.2-20M 2 Magnet assembled on platform 3/19/2015 3/19/2015
1.2-30M 2 Beam-line parts received 9/24/2015 9/24/2015
1.1-10M 1 Project completion 1/29/2016 1/29/2016
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The design of 48D48 components is a HIGH priority!
First Contents Back Conclusion
Frontiers of Nuclear Science:
Theoretical Advances
S(p) =Z(p2)
iγ · p + M(p2)
0 1 2 3
p [GeV]
0
0.1
0.2
0.3
0.4
M(p
) [G
eV
]
m=0 (Chiral limit)
30 MeV70 MeV
for DSE-predicted
Hint of support in Lattice-QCD results
confinement signal
Mass from nothing.
In QCD a quark’s effective mass
depends on its momentum. The
function describing this can be
calculated and is depicted here.
Numerical simulations of lattice
QCD (data, at two different bare
masses) have confirmed model
predictions (solid curves) that the
vast bulk of the constituent mass
of a light quark comes from a
cloud of gluons that are dragged
along by the quark as it
propagates. In this way, a quark
that appears to be absolutely
massless at high energies
(m = 0, red curve) acquires a
large constituent mass at low
energies.
Craig Roberts – Exposing the Dressed Quark’s mass
4th Workshop on Exclusive Reactions at High Momentum Transfer, 18-21 May 2010 . . . 27 – p. 13/28
C.Roberts: the dressed-quark mass function M(p2)
The goal is understanding of QCD
31
First Contents Back Conclusion
Nucleon-Photon Vertex
M.Oettel, M. Pichowsky
and L. von Smekal, nu-th/9909082
6 terms . . .
constructed systematically . . . current conserved automatically
for on-shell nucleons described by Faddeev Amplitude
i
i! !Pf
f
P
Q i
i! !Pf
f
P
Q
i
i! !PPf
f
Q
"#
"
scalaraxial vector
i
i! !Pf
f
P
Q
µ
i
i
X
! !Pf
f
Q
P "#
µi
i
X#
! !Pf
f
P
Q
"
Craig Roberts – Exposing the Dressed Quark’s mass
4th Workshop on Exclusive Reactions at High Momentum Transfer, 18-21 May 2010 . . . 27 – p. 22/28
The goal is understanding of the nucleon
F1 =G
E+τG
M
1 + τ
F2 = −G
E−G
M
1 + τ
From the Sachs FFs to the Dirac&Pauli
The goal is understanding of the nucleon
)2
(GeV2Q
0 2 4 6 8
p 1/F
p 2)
F2
q/2
(Q2
/ln
2Q 0.10
0.15
0.20 = 236 MeVq
p 1/F
p 2Q
F
0.5
1.0
1.5
p 1/F
p 2 F
2Q
0
1
2
3
Guidal05
Diehl05
Puckett et al (2012)
slide 32
]2 [GeV2Q
0 5 10 15 20
p M/G
p EG
pJ
-0.5
0.0
0.5
1.0
GEP-I
GEP-II
GEp-III
VMD - Lomon (2002)
DSE, q(qq) - (2012)
CQM - Miller (2002)2)/Q2q/2(Q2 ln…
1/F2F
= 0.24 GeVq
F2/F1 =
1−GE
/GM
τ+GE
/GM
High Q2 data for EMFFs of the nucleon
slide 33
]2 [GeV2Q
0 10 20 30
DG
pµ/
p MG
0.6
0.8
1.0
1.2
Borkowski
Sill
Bosted
Walker
Andivahis
GPD
Kelly
BBBA05
]2 [GeV2Q
0 5 10 15
DG
nµ/
n MG
0.4
0.6
0.8
1.0
1.2 Rock
Lung
Markowitz
Anklin(1994)
Bruins
Anklin(1998)
Kubon
Lachniet
GPD
Kelly
BBBA05
]2 [GeV2Q
0 5 10 15 20
p M/G
p EG
pJ
-0.5
0.0
0.5
1.0
GEP-I
GEP-II
GEp-III
VMD - Lomon (2002)
DSE, q(qq) - (2012)
CQM - Miller (2002)2)/Q2q/2(Q2 ln…
1/F2F
= 0.24 GeVq
]2 [GeV2Q
n M/G
n EG
nJ
0.0
0.5
1.0
VMD - Lomon (2006)
DSE - Cloet (2010)
Galster fit
BLAST fit
E02-013 fit
MAMI (prel)
Plaster
RiordanE02-013, kin#1 (prel)
2 4 60
]2 [GeV2Q
0 5 10 15
p M/G
p EG
pµ
0.0
0.5
1.0
GEp(1)
GEp(2)
GEp(3)
Diehl
Kelly
BBBA05
]2 [GeV2Q
n M/G
n EG
nµ
0.0
0.2
0.4
0.6
0.8
1.0
RCQM
GPD
VMD
Kelly
BBBA05
DSE
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
The goal is understanding of the nucleon
F1,dual = Fu,p
1= 2 F1p + F1n F1,lone = F
d,p
1= 2 F1n + F1p
Fp =+2
3Fdual +
−1
3Flone
Fn =−1
3Fdual +
+2
3Flone
34
F2/F1 and other ratios
]2 [GeV2Q
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
d 1/F
d 2F
d-1!
0.5
1.0
1.5
]2 [GeV2Q
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
u 1/F
d 1F
0.2
0.4
0.6
RCQM - Miller
Lattice
Diehl et al.
Galster fitq(qq) Faddeev&DSE
]2 [GeV2Q
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
u 2F
u-1!/
d 2F
d-1!
0.5
1.0
1.5
]2 [GeV2Q
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
u 1/Fu 2Fu-1
!
0.0
0.1
0.2
0.3
0.4
0.5
slide 35
pQCD, 1/Q2
The goal is understanding of the nucleon 1
/F2
F2S
= Q
pS
2nS
BJY - pQCD (2003)
2
4
6
]2
[GeV2
Q
2d
S-
uS
1 2 3 4 5 6 7 80
2
4
Flavor separated contribution: The log scaling for the proton Form Factor ratio at few GeV2
is “accidental”.
The lines for each individual flavor are straight!
Sx = Q2F x
2/F x
1
pQCD prediction for large Q2:
S → Q2F2/F1
pQCD updated prediction:
S →�
Q2/ ln2(Q2/Λ2)�
F2/F1
slide 36
CJRW (2011)
F1d < 0 presents an interesting feature!
slide 37
F1 =G
E+τG
M
1 + τ
F2 = −G
E−G
M
1 + τ
Fu
1= 2 F1p + F1n
Fd
1= 2 F1n + F1p
At Q2 = 8 GeV2 ($ = 2)
GEp/GMp ~ 0.1 and
GEn/GMn ~ 0.1?
F1d/F1
u from GMn/GMp at max Q2
]2 [GeV2Q0 2 4 6 8 10 12 14 16 18 20
1/F
1-F
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1BBBA FitKelly FitAlberico FitCLAS dataSLAC dataHall A projected
]2 [GeV2Q0 2 4 6 8 10 12 14 16 18 20
1/F
1F
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5
0.6BBBA FitKelly FitAlberico FitCLAS dataSLAC dataHall A projected
F1
d
/F1
u
−F
n 1/F
p 1
F1d/F1
u from GMn/GMp at max Q2
slide 38
F1d < 0 presents an interesting feature!
]2 [GeV2Q0 2 4 6 8 10 12 14 16 18 20
1/F
1-F
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1BBBA FitKelly FitAlberico FitCLAS dataSLAC dataHall A projected
]2 [GeV2Q0 2 4 6 8 10 12 14 16 18 20
1/F
1F
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5
0.6BBBA FitKelly FitAlberico FitCLAS dataSLAC dataHall A projected
F1
d
/F1
u
−F
n 1/F
p 1
GPD model (Guidal et al) and crossing zero
Transverse densities
C.Carlson & M.Vanderhaeghen !
slide 39
slide 40
Rotation of u/d quarks in neutron
neutron GEn Bogdan Wojtsekhowski, JLab
Let us see how quark rotation leads to u/d separation:
virtual photon quark
motion inside nucleon
M.Burkardt (2003)
amplitude is small
amplitude is large
slide 41
Rotation of u/d quarks in neutron
Interaction selects one side because of rotation
Let us see how quark rotation leads to u/d separation:
M.Burkardt (2003)
virtual photon quark
amplitude is small
amplitude is large
slide 42
Rotation of u/d quarks in neutron
u-quark d-quark
u-quark d-quark
interaction selects
Rotation of u/d quarks in neutron
slide 43
Flavor decomposition of the transverse “charge” densities
[fm]y
b-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1
]-2
[fm
T!
-0.5
0
0.5
1
1.5
2
2.5
3
3.5
4
u quark
d quark
Polarized Transverse Charge Density
b [fm]0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
]-2
[fm
D!
0
0.5
1
1.5
2
2.5
3
3.5
4
u quark
d quark
Dirac Transverse Charge Density
[fm]y
b0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
]-2
[fm
P!
-0.6
-0.4
-0.2
0
0.2
0.4
0.6 u quark
d quark
Pauli Transverse Charge Density
r ����
0.0 0.5 1.0 1.5 2.0 2.5 3.0
]
-�
(����
! 2�
"4
-0.10
-0.05
0.00
0.05
0.10
0.15
0.20Charge Distribution in the Neutron
Ordinary charge density
slide 44
proton
proton
proton
Physical Meaning of Sachs Form Factors Ernst, Sachs, Wali in PR 119 (1105) 1960
45
Physical Meaning of Sachs Form Factors
Galynskii & Kuraev in arXiv:1210.0634
GE
GM
46
Physical Meaning of Sachs Form Factors
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
q 2F
4Q
q-1!
0.1
0.2
0.3
u quark
0.75"d quark
]2 [GeV2Q0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
q 1F
4Q
0.0
0.5
1.0
u quark
2.5"d quark
47
The d-quark contributions to both F1 and F2 are strongly suppressed at high Q2
At Q2 above 1.5 GeV2
both F1 and F2 d-quark contributions are close to 1/Q4
It should be due to the difference between a singly represented d-quark and doubly rep. u-quark
To what is it pointing?
Fu1(0) = 2 F d
1(0) = 1
Fu2(0) = 1.67 F d
2(0) = −2.03
Physical Meaning of Sachs Form Factors
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
q 2F
4Q
q-1!
0.1
0.2
0.3
u quark
0.75"d quark
]2 [GeV2Q0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
q 1F
4Q
0.0
0.5
1.0
u quark
2.5"d quark
48
The d-quark contributions to both F1 and F2 are strongly suppressed at high Q2
At Q2 above 1.5 GeV2
both F1 and F2 d-quark contributions are close to 1/Q4
Fu1(0) = 2 F d
1(0) = 1
Fu2(0) = 1.67 F d
2(0) = −2.03
Physical Meaning of Sachs Form Factors
0 0.5 1 1.5 2 2.5 3 3.50
0.1
0.2
0.3
0.4
0.5
0.6
d
EG4
Q
0 0.5 1 1.5 2 2.5 3 3.5
0.1
0.2
0.3
0.4
0.5
0.6
u
EG4
Q
49
The relative contribution of d-quark to the non-spin flip proton form factor, GEp, is much larger than the projected from the numbers of d- and u-quarks
Summary
slide 50
Our goal is GEP-5 in 2017