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

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, 212502 (2010)] Short Range Correlations – NN force [N. Fomin et al, arXiv:1107.3583, submitted to PRL] Q2 –dependence of the F2 structure functions for a variety of nuclei Momentum Distributions Duality

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

F(y)  n(k) for 2H

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

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

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

Short Range Correlations -- Not a new idea Independent Particle Shell Model : For nuclei, Sα should be equal to 2j+1 => 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

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

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

E02-019 2N 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

Onset of 2N SRC region is not A-independent 2H 197Au

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

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)

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

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

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

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

A EMC effect vs A Beryllium strikes again

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, 202301 (2009)

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

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

“Superfast” quarks Current data at highest Q2 (JLab E02-019) already sensitive to partonic behavior at x>1 N. Fomin et al, PRL 105, 212502 (2010)

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

E08-014 -- Statistics Patricia Solvignon Only half of the data are included (higher systematic errors for those not shown)

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

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

Analysis repeated for other targets All data sets scaled to a common Q2 (at ξ=1.1) N. Fomin et al, PRL 105, 212502 (2010)