Experimental Past and Future Nadia Fomin University of Tennessee - - PowerPoint PPT Presentation

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 Q x Q M M W q q Q E E 2 2 '

2 2 2 2 2 2 2 2

         

θ dΩ dN

flux x F electrons trons of f energy gy E

  d FN dN ) ( 

Number of scattering centers Target

scatt ttered ered electrons of energy E’

Thomas Jefferson National Accelerator Facility

A B C El Electr tron n Source ce Lin inacs cs Experi rimenta ental Hall lls D

now with an 11 GeV beam

Hall C at Jefferson Lab SOS HMS

Scattering Chamber

Beam Line

Shielded Detector Hut

Hall A at Jefferson Lab

2N SRC 3N 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 culty

• 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

• verwhelm the high momentum

nucleons

Past A(e,e’p) experiments in Hall A

2N SRC 3N SRC

Nucleon momentum distribution in 12C

High momentum nucleons

• Short Range Correlations

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 SRC 3N SRC

High momentum nucleons

• Short Range Correlations

2 2 * 1 2 2

) ( ) , ( ' k M p M M Arg Arg E k S dE k d dE d d

A A i ei QE

       



 

    





     

| | 2 2 2

) ( 2 ) ( ) ( 1 ) , (

y n p

kdk k n q y M N Z d d d y F      q q

Ok for for A=2 Deuterium

Fomin et al, PRL 108 108 (2012)

2N SRC 3N SRC

• C. Ciofi degli Atti and S.

Simula, Phys. Rev. C 53 (1996).

Nucleon momentum distribution in 12C

High momentum nucleons

• Short Range Correlations

2N SRC 3N SRC

• C. Ciofi degli Atti and S.

Simula, Phys. Rev. C 53 (1996).

P> P>kferm

rmi

Nucleon momentum distribution in 12C

High momentum nucleons

• Short Range Correlations

Mean n fie field ld Hig igh momentum entum fro rom SRCs Cs

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 A

a A

D A 

 

1.4<x<2 => 2 nucleon correlation 2.4<x<3 => 3 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 j j

Q x A a j A Q x

1 2 2

) , ( ) ( 1 ) , (  

  ) , ( ) ( 2

2 2 2

Q x A a A  .... ) , ( ) ( 3

2 3 3

 Q x A a A 

Before my time







A j j j

Q x A a j A Q x

1 2 2

) , ( ) ( 1 ) , (  

  ) , ( ) ( 2

2 2 2

Q x A a A  .... ) , ( ) ( 3

2 3 3

 Q x A a A 

1.4<x<2 => 2 nucleon correlation 2.4<x<3 => 3 nucleon correlation

Previous measurements

Egiyan et al, Phys.Rev.C68, 2003 No observation of scaling for Q2<1.4 GeV2 1.4<x<2 => 2 nucleon correlation 2.4<x<3 => 3 nucleon correlation

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

<Q2>=2.7 GeV2

Fomin et al, PRL 108 (2012) Jlab E02-019

Test scaling in x and Q2

3He 12C 3He 12C

            



W M W M M q

2 2

4 1 2 2 2 

αi represents the light cone nuclear momentum fraction carried by the constituent nucleon 𝜷𝒋 = 𝒒𝒋− 𝒒𝑩−/𝑩

Look at nuclear dependence of NN SRCs

SRC

• N. Fomin et al, PRL 108

108 (2012)

a2

2 -1

SRC EM EMC

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

Enter 9Be

• N. Fomin et al, PRL 108

108 (2012)

a2

2 -1

• O. Hen,

, et al, PRC RC 85, , 047301 (2012)

• L. Weinstein,

n, 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. Gaske kell, , P. Solvignon non, , PRC RC 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

1 2 / / 

D A A

  ) ( ) ( ) (

2 2 2

x NF x ZF x F

n p A

 

e- e- MA M*A-1 DIS W2≥(Mn+Mπ)2

) ( 2 1 ) ( )] ( ) ( [ 2 1 ) (

2 1 2 1

x F x x F x q x q e x F

i i i

   

 

Shado dowing wing Anti-Shado Shadowi wing ng (pion n exc xces ess) s) Fermi mi mot

• tion
• n effec

fects ts EMC region

) ( ) ( ) (

2 2 2

x NF x ZF x F

n p A

 

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 F2

n/F

/F2

p

• BCDM

DMS -- 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

Nucleo eon n structur ure e is modified ied in the nuclear medium

• r
• r

Nuclea ear r structur ure e is modified ified 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

2H 3He 4He 9Be 12C 27Al* 63Cu 197Au

Precision results on light nuclei from JLab E03-103

• C/D

C/D and 4He/D /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 EM EMC

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

Enter 9Be

• N. Fomin et al, PRL 108

108 (2012)

a2

2 -1

• O. Hen,

, et al, PRC RC 85, , 047301 (2012)

• L. Weinstein,

n, 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. Gaske kell, , P. Solvignon non, , PRC RC 86, , 065204 (2012)

2N knockout experiments establish NP dominance

R.

• R. Sube

bedi di et et al. l., Science e 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

R.

• R. Sube

bedi di et et al. l., Science e 320, , 1476 (2008)

• R. Shneor et al.,

PRL 99, 072501 (2007)

9.5 ± 2 % 96 ± 23 %

NP dominance

• R. Sube

bedi di et et al. l., Science e 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

1.4<x<2 => 2 nucleon correlation 2.4<x<3 => 3 nucleon correlation







A j j j

Q x A a j A Q x

1 2 2

) , ( ) ( 1 ) , (  

  ) , ( ) ( 2

2 2 2

Q x A a A  .... ) , ( ) ( 3

2 3 3

 Q x A a A 

2N SRC 3N SRC

3N correlations (x>2 inclusive scattering)

• K. Egiya

yan n et al, PRL96, , 082501 (2006)

<Q2> (GeV2): CLAS AS: : 1.6 E02 02-019 19: 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!