Short-range NN interactions: Experimental Past and … · Short-range NN interactions: ... Jlab E02-019. Test scaling in x and Q2 3 He 12 C 3 12 ... Study short range correlations

Short-range NN interactions:

Experimental Past and Future

Nadia Fomin

University of Tennessee

April 12th, 2017

The quick and the correlated:

Progress towards understanding short-range NN

interactions

The quick and the correlated:

Progress towards understanding short-range NN

interactions

Electron scattering is a great tool for studying subatomic structure:

unlike a proton, it cannot be absorbed by the nucleus

resolution varies with momentum transfer, allowing us to probe

the entire volume of the nucleus

Choosing an Appropriate Microscope

q

1

"for his pioneering studies of electron

scattering in atomic nuclei and for his

thereby achieved discoveries

concerning the structure of the

nucleons"

R. Hofstadter

Nobel Prize 1961

Collisions – Measured Cross sections

M

Qx

QMMW

qqQ

EE

2

2

'

2

222

2222

θ

dΩ

dN

flux F

electrons of energy E dFNdN )(

Number of scattering centersTarget

scattered

electrons of energy E’

Thomas

Jefferson

National

Accelerator

Facility

A B C

Electron

Source

Linacs

Experimental Halls

D

now with an 11 GeV beam

Hall C at

Jefferson Lab

SOS HMS

Scattering ChamberBeam Line

Shielded Detector Hut

Hall A at

Jefferson Lab

2N SRC3N SRC

Nucleon

momentum

distribution in 12C

High momentum nucleons

- Short Range Correlations

High momentum tails in A(e,e’p)

• E89-004: Measure of 3He(e,e’p)d

• Measured far into high momentum

tail: Cross section is ~5-10x

expectation

Difficulty

• High momentum pair can come from

SRC (initial state)

OR

• Final State Interactions (FSI) and

Meson Exchange Contributions (MEC)

“slow” nucleons “fast” nucleons

p p p p

A(e,e’p)

2H(e,e’p) Mainz

PRC 78 054001 (2008)

E =0.855 GeV

θ = 45o

E’=0.657 GeV

Q2=0.33 GeV2

x=0.88

Unfortunately: FSI, MECs

overwhelm the high momentum

nucleons

Past A(e,e’p) experiments in Hall A

2N SRC3N SRC

Nucleon

momentum

distribution in 12C



Try inclusive scattering!

Select kinematics such that

the initial nucleon

momentum > kf

QE

Jlab E02-019

JLab, Hall C, 1998

(x>1) x=1 (x<1)

Deuteriu

m

2N SRC3N SRC



22*

1

22

)(),('

kMpMMArg

ArgEkSdEkddEd

d

AA

iei

QE

||

22

2

)(2

)()(

1),(

y

np

kdkkn

qyMNZdd

dyF

qq

Ok for A=2

Deuterium

Fomin et al, PRL 108 (2012)

2N SRC3N SRC

C. Ciofi degli Atti and S.

Simula, Phys. Rev. C 53

(1996).

Nucleon

momentum

distribution in 12C



2N SRC3N SRC

C. Ciofi degli Atti and S.

Simula, Phys. Rev. C 53

(1996).

P>kfermi

Nucleon

momentum

distribution in 12C



Mean

field

High

momentum

from SRCs

Short Range Correlations• To experimentally probe SRCs, must be in the high-momentum region (x>1)

• To measure the relative probability of

finding a correlation, ratios of heavy to light

nuclei are taken

• In the high momentum region, FSIs are

thought to be confined to the SRCs and

therefore, cancel in the cross section ratios

)(2

2 AaA D

A

1.4<x<2 => 2 nucleon correlation


• L. L. Frankfurt and M. I. Strikman, Phys.

Rept. 76, 215(1981).

• J. Arrington, D. Higinbotham, G. Rosner, and

M. Sargsian (2011), arXiv:1104.1196

• L. L. Frankfurt, M. I. Strikman, D. B. Day, and

M. Sargsian, Phys. Rev. C 48, 2451 (1993).

• L. L. Frankfurt and M. I. Strikman, Phys.

Rept. 160, 235 (1988).

• C. C. degli Atti and S. Simula, Phys. Lett. B

325, 276 (1994).

• C. C. degli Atti and S. Simula, Phys. Rev. C

53, 1689 (1996).

A

j

jj QxAaj

AQx1

22 ),()(1

),(

),()(2

2

22 QxAaA

....),()(3

2

33 QxAaA

Before my time

A

j

jj QxAaj

AQx1

22 ),()(1

),(

),()(2

2

22 QxAaA

....),()(3

2

33 QxAaA



Previous measurements

Egiyan et al, Phys.Rev.C68, 2003

No observation of scaling for

Q2<1.4 GeV2



E02-019: 2N correlations in A/D ratios

<Q2>=2.7 GeV2Fomin et al, PRL 108 (2012)

Jlab E02-019

Test scaling in x and Q2

3He

12C

3He

12C

W

MW

M

Mq 22 41

2

22

αi represents the light cone nuclear momentum fraction carried by the

constituent nucleon𝜶𝒊 =

𝒑𝒊−𝒑𝑨−/𝑨

Look at nuclear dependence of NN SRCs

SRC

N. Fomin et al, PRL 108 (2012)

a2

-1

SRC

EMC

J.Seely, et al., PRL 103, 202301 (2009)

Enter 9Be


a2

-1

O. Hen, et al, PRC 85, 047301 (2012)

L. Weinstein, et al., PRL 106, 052301 (2011)

J. Seely, et al., PRL103, 202301 (2009)

N. Fomin, et al., PRL 108, 092052 (2012)

JA, A. Daniel, D. Day, N. Fomin, D.

Gaskell, P. Solvignon, PRC 86, 065204

(2012)

• Goal was a measurement of the lepton-nucleon

cross section at high Q2

• To achieve statistical precision in a

reasonable amount of time, an iron target

was used, on the assumption that

meaning

Discovery of the EMC effect

12/

/

D

A A

)()()( 222 xNFxZFxF npA

e-

e-

MA

M*A-1

DIS

W2≥(Mn+Mπ)2

)(2

1)(

)]()([2

1)(

21

2

1

xFx

xF

xqxqexF iii

Shadowing

Anti-Shadowing

(pion excess)Fermi motion effects

EMC region

)()()( 222 xNFxZFxF npA

Nuclear dependence of the

structure functions discovered

30+ years ago by the European

Muon Collaboration (EMC effect)

The EMC effect

Nucleon structure functions are

modified by the nuclear medium

Depletion of high-x quarks for

A>2 nuclei is not expected or

understood

Measurements before 2004

• NMC – extraction of F2n/F2

p

• BCDMS -- 50 < Q2 < 200 (GeV2)

• HERMES – first measurement on 3He

• SLAC E139 – most precise large

x data

• Q2 independent

• Universal shape

• Magnitude approximately

scales with density

Nucleon structure is modified in the nuclear medium

or

Nuclear structure is modified due to hadronic effects

Models of the EMC effect

• Dynamical rescaling

• Nucleon ‘swelling’

• Multiquark clusters (6q, 9q ‘bags’)

• More detailed binding calculations

•Fermi motion + binding

• N-N correlations

• Nuclear pions

Nuclear Dependence of the EMC effect

Quark distributions are modified in

nuclei

Modification scales with A

ratio evaluated at x=0.6

ratio evaluated at x=0.6

4He

4He

Jlab E03-103

2H3He4He9Be12C27Al*63Cu197Au

Precision results on light

nuclei from JLab E03-103

•C/D and 4He/D ratios – no

isoscalar correction necessary

•Consistent with SLAC results, but

much higher precision at high x

PhD theses: J. Seely, A. Daniel

•Fit the slope of the ratios for

0.35<x<0.7:

• Compare across nuclei

dx

dREMC

J.Seely, A. Daniel, et al., PRL103, 202301 (2009)

SRC

EMC

J.Seely, et al., PRL 103, 202301 (2009)

Enter 9Be


a2

-1

O. Hen, et al, PRC 85, 047301 (2012)

L. Weinstein, et al., PRL 106, 052301 (2011)

J. Seely, et al., PRL103, 202301 (2009)

N. Fomin, et al., PRL 108, 092052 (2012)

JA, A. Daniel, D. Day, N. Fomin, D.

Gaskell, P. Solvignon, PRC 86, 065204

(2012)

2N knockout experiments establish NP dominance

R. Subedi et al., Science

320, 1476 (2008)

R. Shneor et al.,

PRL 99, 072501 (2007)

• Knockout high-initial-

momentum proton, look for

correlated nucleon partner.

• For 300 < Pmiss < 600 MeV/c all

nucleons are part of 2N-SRC

pairs: 90% np, 5% pp (nn)

2N knockout experiments establish NP dominance


320, 1476 (2008)

R. Shneor et al.,

PRL 99, 072501 (2007)

9.5 ± 2 %

96 ± 23 %

NP dominance


320, 1476 (2008)

R. Shneor et al.,

PRL 99, 072501 (2007)9.5 ± 2 %

96 ± 23

%

also Ciofi and Alvioli PRL 100, 162503 (2008)Sargsian, Abrahamyan, Strikman, Frankfurt PR C71 044615 (2005)

Slide courtesy O. Hen

Data mining using CLAS NP dominance continues for heavy nuclei

Assuming scattering off 2N-SRC pairs:

• (e,e’p) is sensitive to np and pp pairs

• (e,e’pp) is sensitive to pp pairs alone

=> (e,e’pp)/(e,e’p) ratio is sensitive to the np/pp

ratio

Coming very soon: [A=3 Measurements]

• Quasielastic electron scattering with 3H and 3He

• Study isospin dependence of 2N and 3N correlations

• Test calculations of FSI for well-understood nuclei

• EMC effect on A=3 nuclei

More nucleons in a correlation



A

j

jj QxAaj

AQx1

22 ),()(1

),(

),()(2

2

22 QxAaA

....),()(3

2

33 QxAaA

2N SRC3N SRC

3N correlations (x>2 inclusive scattering)

K. Egiyan et al, PRL96, 082501 (2006) <Q2> (GeV2): CLAS: 1.6 E02-019: 2.7

Have we actually seen 3N SRC in ratios?

3N correlations

Courtesy Zhihong Ye

3N correlations – are we there yet?

α3N_MIN=1.6

Where does 2N contribution become negligible?

Jlab E12-06-105

&& E12-10-008• short-range nuclear structure

- Isospin dependence

- A-dependence

• Super-fast quarks

Jlab E12-06-105

&& E12-10-008• short-range nuclear structure

- Isospin dependence

- A-dependence

• Super-fast quarks

Summary

• SRCs and EMC effect have been under the

microscope for many decades – 6GeV era at

Jlab has yielded interesting data

• 12 GeV experiments continue the search

• Upcoming experiments in Halls A/C

Study short range correlations in 3He/3H

Map out nuclear dependencies of clustering

Study how quark distributions are modified in nuclei over

free nucleons

• New results in the next few years!

Short-range NN interactions: Experimental Past and … · Short-range NN interactions: ... Jlab E02-019. Test scaling in x and Q2 3 He 12 C 3 12 ... Study short range correlations

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