Neutron Form Factorsrelnp.jinr.ru/ishepp-xx/presentations/Wojtsekhowski.pdf · Neutron Form Factors Bogdan Wojtsekhowski, Jefferson Lab Neutron structure and EM form factors Recent

Neutron Form Factors Bogdan Wojtsekhowski, Jefferson Lab

Neutron structure and EM form factors Recent experiment 3He(e,e’n) at Jlab Flavor decomposition of nucleon FFs The transverse neutron densities Future GEN&GMN and GMN/GMP at high Q2

October 4, 2010 Bogdan Wojtsekhowski Baldin 2010 slide 2

Highlights of the neutron Prediction: Rutherford 1920 Discovery: Chadwick 1932 Magnetic moment:Esterman&Stern 1934, Alvarez&Bloch 1940 Determination of spin 1/2: Schwinger 1937 Direct observation of the structure: Hofstadter 1950th SLAC measurement of Gn

M up to 10 GeV2 Time like FFs: DM2, FENICE Polarizabilities: SAL, Mainz, Lund Polarized electron beam era: Sinclair’s electron source in 1977 CEBAF with polarimeter and polarized targets in 1990th Unification of DIS/FFs/DVCS in GPDs by Muller, Ji, Radyushkin Gn

M/GpM precision measurement by Brooks etal in 2001

Polarized He-3: laser pumping Gn

E/GnM measurements at NIKHEF, Mainz, JLab, BATES


Electro-Magnetic Form Factors

Rosenbluth (1950) !

Akhiezer (1958)!Arnold, Carlson !and Gross (1981)!

Guichon &!Vanderhaeghen!

Afanasev et al.!Blunden et al.!

One-photon approximation, αem = 1/137, hadron current !

Full expression for M has three complex functions, F1, F2, F3 !

old GE,M are real !functions of t=-Q2!

Extra terms contribute less than few % to σR !

At large Q2 study of GE require use of !polarization observables - FFs at CEBAF!


Photon - Neutron Interaction

At Q2 of several GeV2 massive photon vibrates in q-qbar, which can’t propagate far - already inside of the nucleon => still such q-qbar propagates as a VM !

Q2=0


GPDs of nucleon Muller (94), Ji (97), Radyushkin (97) :!


GPDs information a lot to measure P.Kroll, Excl.-07

Ji’s sum rule for quark orbital momentum

!Lqv" = 1

2

! 10 dx [xEq

v(x, ! = 0, t = 0) + xqv(x) # !qv(x)]

DVCS will access low t, large Q2 kinematics


3-d picture of the nucleon

Proton form factors, transverse charge & current densities

Structure functions, quark longitudinal momentum & helicity distributions

Correlated quark momentum and helicity distributions in transverse space - GPDs

Sachs Form Factors of the nucleon

]2 [GeV2Q

0 5 10 15

DG

pµ/

p MG

0.7

0.8

0.9

1.0

1.1

1.2

Borkowski

Sill

Bosted

Walker

Andivahis

Diehl

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

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


Recent experiment at Jlab

:!


Jlab high Q2 GEN experiment Since 1984, when Blankleider&Woloshin suggested ,!several experiments of this type have been performed at NIKHEF-K !and Mainz (A1, A3) for Q2 up to 0.7 GeV2 , a big success in part due to!a new accurate 3-body calculation possible at low Q2 (Glockle et al.)!

At Q2 above 1-2 GeV2 Glauber method becomes sufficiently " " " " " " " accurate (Sarksian)!

Electron-polarized neutron luminosity and high polarization of 3He!target made measurement about 10 times more effective than with ND3. In combination with a large acceptance electron spectrometer the total enhancement is more than 100, which allows to reach 3.5 GeV2 !

• Polarized target !• Electron spectrometer!• Neutron detector!

Require super!

:!


Double polarization method

Selection of QE !by cut P < 150 MeV !

Hall A GEn experiment

Beam

Target Neutron arm

Electron arm

October 4, 2010 slide 12 Bogdan Wojtsekhowski Baldin 2010

Target Neutron arm

Electron arm Neutron arm

Pumping chamber

Laser light

Polarized beam

Target chamber

Scattered electron

Recoiled neutron

Rb + K

Polarization pumping

Jpolarized nuclei.x P2nuclei

GEn

Beam Hall A GE

n experiment


• Solid angle of 76 msr (12 times higher than HRS) • 40 cm long target • Momentum resolution of 1%

Beam

Target Electron arm Neutron arm

Hall A GEn experiment



Electron Spectrometer Useful ΔQ2/Q2 ~ 0.1 with max Ω leads to a large aspect ratio, limited just of 30o for the polar. target. BigBite was designed at NIKHEF for aspect ratio Δθ/Δφ = 1/5. Spectrometer has solid angle up to 95 msr.!

With luminosity of JLab polarized target, 1037 cm-2/s, the open geometry - a dipole spectrometer - works well when!all MWDCs located behind the magnet.!


Neutron Detector • Match BigBite solid angle " for QE kinematics !• Flight distance ~ 10 m !• Operation at 3.1037 cm2/s!

• 1.6 x 5 m2 active area !• 6-7 layers (~ 250 bars)!• 2 veto layers (~ 200)!• 0.38 ns time resolution!


Target monitoring

Single arm rate (neutral pions)

smaller is better for reduction of the systematic errors


Data analysis: step 1 - Time-of-Flight

Raw events (BLACK lines) have significant accidental level and large tail for slower protons

RED lines present events after cut on e’-n angular correlation: accidentals and tails almost gone


Analysis: step 2 - qperp vs W; 1.7 GeV2 perpendicular “q” = q x tan(θqh); W2 = M2 + 2M(E-E’) - Q2

Quasi elastic events dominates after Full Cuts applied max value of used perp. q


Analysis: step 3 - W distribution

for 3.5 GeV2 quasi-elastic signal very small in e,e’ after angular correlation cut peak is just as suppose to be

The results GEn experiment

Target Neutron arm

Electron arm


]2 [GeV2Q

n M/G

n EG

nµ

0.0

0.2

0.4

0.6

0.8

RCQM

GPD

VMD

DSE

= 150 MeV!pQCD,

= 300 MeV!pQCD,

0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

The JLab GEn experiments

Target Neutron arm

Electron arm


]2 [GeV2Q

0 1 2 3 4

D/G

n EG

0.0

0.2

0.4

0.6

0.8

1.0

]2 [GeV2Q

0 1 2 3 4

D/G

n EG

0.0

0.2

0.4

0.6

0.8

1.0

Electric Form Factor of the Neutron

without JLab GEn experiments

significantly better accuracy for high Q2


Recent experiment at Bates

D(e,e’n) DRIFT CHAMBERS

CERENKOV COUNTERS

SCINTILLATORS NEUTRON COUNTERS

TARGET BEAM

BEAM

COILS


Running experiment at Mainz

]2 [GeV2Qn M

/Gn E

Gn!

0.0

0.2

0.4

0.6

0.8

RCQM - Miller (2006)

GPD - DiehlVMD - Lomon (2005)

DSE - RobertsOur Kelly fit

= 150 MeV!, 1

/F2F

= 300 MeV!, 1

/F2F

Passchier, NIKHEF

Herberg, MAMI

Ostrick, MAMI

Meyerhoff, MAMI

Golak, MAMI

Bermuth, MAMI

Plaster, JLab

Zhu, JLab

Warren, JLab

Glazier, MAMI

Geis, BATES

E02-013

A1 Result - Prelim.

0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

Flavor view with EMFFs


]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 = Fd,p

1 = 2 F1n + F1p

Fp = +23 Fdual + !1

3 Flone

Fn = !13 Fdual + +2

3 Flone

F1d

(2)/F1u

(2) with proton and neutron FFs

Fu

1 = 2 F1p + F1n

Fd

1 = 2 F1n + F1p

F1 = GE +!GM

1 + !

F2 = !GE !GM

1 + !

Lattice calculation => very good agreement with the trend, need accuracy DSE (ANL) => good, possibly a signature of dominant degrees of freedom Our data will require a new fit of Ed and Eu GPDs

u 1/F

d 1F

0.2

0.4

0.6

RCQM

GPD

Lattice

]2 [GeV2Q0.5 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

VMD

DSE


Form Factors ratios

]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

x

0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

d/u

0.0

0.2

0.4

0.6

JLab Projected Data

He DIS3

H/ 3

]2 [GeV2Q

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

u 1/F

u 2F

u-1!

0.0

0.1

0.2

0.3

0.4

0.5

F1,

lone/

F1,

dual

!!

1

du

alF

2,d

ual/

F1,d

ual

]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


GPD - Diehl

Galster + Kelly

VMD - Lomon (2006)

Kelly Param.

!!

1

loneF

2,lo

ne/

F1,

lone

Form Factors ratios

]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.


x

0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

d/u

0.0

0.2

0.4

0.6

JLab Projected Data

He DIS3

H/ 3

]2 [GeV2Q

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

u 1/F

u 2F

u-1!

0.0

0.1

0.2

0.3

0.4

0.5

F1,

lone/

F1,

dual

!!

1

du

alF

2,d

ual/

F1,d

ual

correspondence e.g. via GPDs

]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


GPD - Diehl

Galster + Kelly

VMD - Lomon (2006)

Kelly Param.

!!

1

loneF

2,lo

ne/

F1,

lone

Form Factors ratios

]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.


x

0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

d/u

0.0

0.2

0.4

0.6

JLab Projected Data

He DIS3

H/ 3

]2 [GeV2Q

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

u 1/F

u 2F

u-1!

0.0

0.1

0.2

0.3

0.4

0.5

F1,

lone/

F1,

dual

!!

1

du

alF

2,d

ual/

F1,d

ual

Dual and Lone quark distribution FFs

correspondence e.g. via GPDs

]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


GPD - Diehl

Galster + Kelly

VMD - Lomon (2006)

Kelly Param.

!!

1

loneF

2,lo

ne/

F1,

lone

- What is a unique signature of the diquark configuration?

]2 [GeV2Q

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

u 1/F

u 2F

u-1!

0.0

0.1

0.2

0.3

0.4

0.5


Results of E02-013 Hall A GEn

!!

1

du

alF

2,d

ual/

F1,d

ual

Fp = +23 Fdual + !1

3 Flone

Fn = !13 Fdual + +2

3 Flone

]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


GPD - Diehl

Galster + Kelly

VMD - Lomon (2006)

Kelly Param.

!!

1

loneF

2,lo

ne/

F1,

lone

- A diquark configuration? - An effect of orbital motion?

]2 [GeV2Q

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

u 1/F

u 2F

u-1!

0.0

0.1

0.2

0.3

0.4

0.5

Results of E02-013 Hall A GEn


0.3 !!

1

du

alF

2,d

ual/

F1,d

ual

F1,dual = Fu,p

1 = 2 F1p + F1n F1,lone = Fd,p

1 = 2 F1n + F1p

]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


GPD - Diehl

Galster + Kelly

VMD - Lomon (2006)

Kelly Param.

!!

1

loneF

2,lo

ne/

F1,

lone

1.2

Interesting observation: F2/F1 = R is constant in the Q2-range 1 - 3.5 GeV2


EMFFs and GPDs


GMn/GMp and GPDs

)2 (GeV2Q0 2 4 6 8 10 12 14 16 18 20

p 1/F

n 1-F

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1Kelly FitBBBA FitAlberico FitCLAS dataSLAC dataHall A projected

)2 (GeV2Q0 2 4 6 8 10 12 14 16 18 20

u 1/F

d 1F

-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

0.6Kelly FitBBBA FitAlberico FitCLAS dataSLAC dataHall A projected

GPD model (Guidal etal):

F1d < 0 presents an interesting

challenge to such a model F1,

lone/

F1,

dual

The transverse neutron densities



Impact parameter GPDs

Muller, Ji, Radyushkin!

M.Burkardt!

P.Kroll: u/d segregation!

G.Miller!


Transverse densities

C.Carlson & M.Vaderhaeghen !

transversely polarized neutron has huge EDM

Flavor decomposition of IMF 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 [fm]

0.0 0.5 1.0 1.5 2.0 2.5 3.0

]-1

(r)

[fm

! 2

r"

4

-0.10

-0.05

0.00

0.05

0.10

0.15

0.20Charge Distribution in the Neutron

Ordinary charge density


Density in polarized neutron

C.Carlson & M.Vaderhaeghen !

Spin

Momentum transfer

u

d

Transversity effects in

bx

by

October 4, 2010 slide 40

Rotation of u/d quarks in neutron

neutron GEn Bogdan Wojtsekhowski, JLab

Let see how quark rotation leads to u/d separation:

virtual photon quark

motion inside nucleon

M.Burkardt (2003)

amplitude is small

amplitude is large

Bogdan Wojtsekhowski Baldin 2010

October 4, 2010 slide 41


neutron GEn Bogdan Wojtsekhowski, JLab

Interaction selects one side because of rotation

M.Burkardt (2003)

Let see how quark rotation leads to u/d separation:

virtual photon quark

amplitude is small

amplitude is large


October 4, 2010 slide 42 neutron GEn Bogdan Wojtsekhowski, JLab

Rotation of u/d quarks in neutron u-quark d-quark


The u/d “separation”, observed in Form Factor data, is likely a result of the collective rotation of the u-quark and the d-quark, which is going in opposite directions

u-quark d-quark

interaction selects



Future neutron FFs experiments


Future neutron FFs experiments


D(e,e’n)p / D(e,e’p)n – under preparation

Double pol. He-3(e,e’n)pp – under preparation

D(e,e’n)p – requires a new AY data from JINR ( talk by J. Annand)

Optimization of the experimental setup Hadron Arm

Beam

Target

Electron Arm

.

.

17 m

Neutron Magnetic Form Factor

GEM

BigBenBNL

BigBiteGasCher

ECalo

HCalo

48D48

Electron Arm

Beam

.

.

Target

Proton form factors ratio, GEp(5): E12!07!109

Proton Arm

Lead!glassCalorimeter

BNLINFN

HCalo

Al filter

48D48

GEM

GEM

GEM

BigBenGEM

Beam

Target

Hadron Arm

Electron Arm

.

.

17 m

HCalo

48D48

BigBenBNL

BigBiteGasCher

ECalo

Neutron form factors, E12!09!016 and E12!09!019

GEM

Proton Magnetic Form Factor

Neutron form factors ratio, GEn(2):E12-09-016


Neutron/proton form factors ratio: E12-09-019 Proton magnetic form factor: E12-07-108


Neutron/proton form factors ratio: E12-09-019

D(e,e’n)p / D(e,e’p)n

Beam

Target

Hadron Arm

Electron Arm

.

.

17 m

HCalo

48D48

BigBenBNL

BigBiteGasCher

ECalo


GEM

Deuterium

Beam

Target

Hadron Arm

Electron Arm

.

.

17 m

HCalo

48D48

BigBenBNL

BigBiteGasCher

ECalo


GEM

Neutron form factors ratio, GEn(2):E12-09-016


Double polarized He-3(e,e’n)pp

Polarized He-3

Polarized

CLAS 12 BigBite + SBS


)2 (GeV2Q0 2 4 6 8 10 12 14 16 18 20

DG

nµ/

n MG

0.2

0.4

0.6

0.8

1

1.2

BBBA FitKelly FitAlberico FitCLAS dataSLAC data

Hall A E12-09-19

value on BBBA fit

Hall B E12-07-104

value shifted to 1.1

Gilman, Quinn, and BW

12 GeV GMn experiment

W.Brook etal


Cates, Riordan, and BW

]2 [GeV2Q

n M/G

n EG

n!

0.0

0.5

1.0RCQM - Miller

GPD - Diehl

VMD - Lomon (2005)

Faddeev&DSE - Roberts = 300 MeV!,

1/F2F

Passchier, NIKHEFHerberg, MAMI

Ostrick, MAMI

Meyerhoff, MAMI

Golak, MAMI

Bermuth, MAMI

Plaster, JLab

Zhu, JLab

Warren, JLab

Glazier, MAMI

Geis, BATES

E02-013

E12-09-016, Hall A

2 4 6 8 10 12 14 16 18 20

12 GeV GEn experiment


CEBAF electron beam in 2013(4)

Hall A will be the first hall which will get the beam

• Beam energy 11/12 GeV

• Beam power 1 MW

• Beam current (Hall A/D) 85/5 µA

• Beam polarization 85%

• Emittance @ 12 GeV 10 nm-rad

• Energy spread @ 12 GeV 0.02%

• Beam spot ~ 0.1mm

• Simultaneous beam delivery Up to 3 halls


THANKS


Polarized target 3He = p + p + n! S + S’ + P waves! Pn = 0.86 PHe !

Rb + K mixture has shortened spin-up time to 5-8 hours. The hybrid method of optical pumping was used here for the first time in the nuclear target.!

Pumping chamber!

Laser light!

Polarized beam!

Target chamber!

Scattered electron!

Recoiled neutron!

PHe of 50% with 8 µA beam !

Documents

Neutron Form Factorsrelnp.jinr.ru/ishepp-xx/presentations/Wojtsekhowski.pdf · Neutron Form Factors Bogdan Wojtsekhowski, Jefferson Lab Neutron structure and EM form factors Recent