Short Range NN Correlations (from Inclusive Cross Sections)

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 P_min (GeV/c) x • 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

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

3He 3He E02-019 2N Ratios (A/D) α2N -Light-cone momentum fraction of the struck nucleon vs x Raw Cross Section Ratios vsα2N 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

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/σDyields 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

<Q2>(GeV2) CLAS: 1.6 E02-019: 2.7 E02-019 Ratios 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

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) δp = ±4.5% δp = ±3% E02-019 kin# 6.5 CLAS

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

Soon….. • 2H • 3He • 4He • 6,7Li • 9Be • 10,11B • 12C • 40Ca • 48Ca • Cu • Au 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)

Short Range NN Correlations (from Inclusive Cross Sections)