gep experimentwm-jlab.physics.wm.edu/mediawiki/images/0/0a/bogdan_gep-compressed.pdf · the front...

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

$

!"#$%&'1$23.4+5-$67+3,)89-0$

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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