1. Short Range NN Correlations (from Inclusive Cross Sections)
Nadia Fomin
Los Alamos National Laboratory
August 19th, 2011
Newport News, VA

2. Data mining E02-019
Inclusive Quasielastic and Inelastic Data allows the study of a wide variety of physics topics
Scaling (x, y, ξ, ψ)
Superfast quarks [N. Fomin et al, PRL 105, (2010)]
Short Range Correlations – NN force [N. Fomin et al, arXiv: , submitted to PRL]
Q2 –dependence of the F2 structure functions for a variety of nuclei
Momentum Distributions
Duality

3. Deuterium
Usually, we look at x>1 results in terms of scattering from the nucleon in a nucleus and they are described very well in terms of y-scaling (scattering from a nucleon of some momentum)
Quasielastic scattering is believed to be the dominant process
F(y,q)
x=1
Deuterium

4. F(y)  n(k) for 2H

5. Not so fast, heavy nuclei
Scaling is not perfect
Final State Interactions (known to exist from (e,e’,p), where the proton is absorbed in the nucleus)
Contribution from inelastic processes
Excitation of the nucleus – barrier to extracting momentum distributions Au

6. Other scaling variables?
ycw – analogous to y, but accounts for the excitation of the residual nucleus (Ciofi degli Atti – PRC, 2009)
Other scaling variables also exist, but this approach is model-dependent

7. High momentum nucleons
- Short Range Correlations
3N SRC
2N SRC
C. Ciofi degli Atti and S. Simula, Phys. Rev. C 53 (1996).

8. Short Range Correlations -- Not a new idea
Independent Particle Shell Model :
For nuclei, Sα should be equal to 2j => number of protons in a given orbital
However, it as found to be only ~2/3 of the expected value
The bulk of the missing strength it is thought to come from short range correlations
NN interaction generates high momenta (k>kfermi)
momentum of fast nucleons is balanced by the correlated nucleon(s), not the rest of the nucleus

9. Short Range Correlations
To experimentally probe SRCs, must be in the high-momentum region (x>1)
To measure the 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
1.4<x<2 => 2 nucleon correlation
2.4<x<3 => 3 nucleon correlation
P_min (GeV/c) x

10. Short Range Correlations – 2 Nucleons (CLAS and SLAC)
4He
56Fe
Egiyan et al, Phys.Rev.C68, 2003
Plots by D. B. Day
No observation of scaling for Q2<1.4 GeV2

11. E N Ratios (A/D)
3He
α2N - Light-cone momentum fraction of the struck nucleon
vs x
Raw Cross Section Ratios
3He
vs α2N
Onset of scaling occurs for fixed α2N, but not x

12. Onset of 2N SRC region is not A-independent2H
197Au

13. E02-019: 2N correlations in A/D ratios
18° data
<Q2>=2.7 GeV2
R(A, D) for
α2N >1.275
3He
2.14±0.04
4He
3.66±0.07 Be
4.00±0.08 C
4.88±0.10 Cu
5.37±0.11 Au
5.34±0.6

14. CM Motion of the 2N pair
If we’re in the regime of quasielastic scattering from a nucleon in an n-p SRC at rest  σA/σD yields the number of nucleons in high momentum pairs relative to deuterium
Need to remove the smearing effect of the CM motion of the 2N SRC pairs
Enhances the high momentum tails in heavy nuclei
Correction was calculated via convolution of iron CM motion with deuterium n(k)
Isoscalar corrections removed from SLAC and CLAS results (where applicable)

15. Short Range Correlations – 3N
1.4<x<2 => 2 nucleon correlation
2.4<x<3 => 3 nucleon correlation
Egiyan et al, PRL 96, 2006

16. E02-019 Ratios <Q2> (GeV2) CLAS: 1.6 E02-019: 2.7
Preliminary
Excellent agreement for x≤2
Very different approaches to 3N plateau, later onset of scaling for E02-019
Very similar behavior for heavier targets
Need higher statistics data for a more definitive comparison

17. E02-019: 2N correlations in A/D ratios
18° data
<Q2>=2.7 GeV2
R(A, D) for
α2N >1.275
3He
2.14±0.04
4He
3.66±0.07 Be
4.00±0.08 C
4.88±0.10 Cu
5.37±0.11 Au
5.34±0.6

18. Examine the A dependence of SRCs – 2N
A-dependence, especially the 9Be looks very familiar
Possible connection to physics in a completely different kinematic regime

19. A
EMC effect vs A
Beryllium strikes again

20. What does this mean ? EMC effect appears to follow “local” density
Sounds like the short range structure that we would normally study at x>1 (result of nucleon interaction at short range)
J.Seely, et al., PRL103, (2009)

21. SRC vs EMC
Suggests both effects could be sensitive to a similar quantity
Probing what happens when nucleons come close together
Linear relationship between EMC effect and SRC
L. Weinstein, E. Piasetzky, D.W. Higinbotham, J. Gomer, O. Hen, R. Schneor
PRL 106:052301,2011

22. Overlapping nucleons enhancement of F2 structure function
two-nucleon only
two-nucleon only
5% 6 quark bag
5% 6 quark bag
qD(x)
Small effect, possible contribution to EMC effect?
Noticeable effect at x>1

23. “Superfast” quarks
Current data at highest Q2 (JLab E02-019) already sensitive to partonic behavior at x>1
N. Fomin et al, PRL 105, (2010)

24. The Future is now -- E08-014 (recently completed)
kin# 6.5
CLAS

25. E Statistics
Patricia Solvignon
Only half of the data are included (higher systematic errors for those not shown)

26. Soon….. 2H 3He 12C 40Ca 4He 48Ca 6,7Li Cu 9Be Au 10,11B
x>1 at 12 GeV
Follow up experiments for EMC effect and x>1 approved with high scientific ratings
EMC effect 12 GeV

27. Summary E02-019 offer a very rich data set
1 PRL, another one submitted
Results suggest a local density dependence of the EMC effect as well as SRCs
These hints and suggestions need to be further investigated with new experiments

28. Analysis repeated for other targets
All data sets scaled to a common Q2 (at ξ=1.1)
N. Fomin et al, PRL 105, (2010)