CLAS12 European Workshop February 25-28, Genova, Italy Analyzing CLAS / Hall B Data to Extract New Results on QCD Nuclear Physics An Initiative to Maximize the Return on Already Collected Data M. Strikman, L. Weinstein, S. Kuhn, S. Stepanyan, E. Piasetzky, K. Griffioen, M. Sargsian Eli Piasetzky Tel Aviv University, ISRAEL

MEGIDDO: THE FLAGSHIP OF TEL AVIV UNIVERSITY DIGS A mound with 32 cities one on top of the other Schumacher University of Chicago 1960s,1970s The Hebrew University Tel Aviv University

Schumacher University of Chicago 1960s,1970s The Hebrew University Tel Aviv University

The physics driving the proposed analysis Short Range Correlations (SRC) Hadronization Nuclear Matter in non - equilibrium condition Nuclear transparency Detailed study on few body systems (Deuteron, 3He)

Nucleon Short Range Correlations (SRC)  1.f Nucleons 2N-SRC 1.7f  o = 0.16 GeV/fm 3   5  o ~1 fm 1.7 fm What SRC in nuclei can tell us about: High – Momentum Component of the Nuclear Wave Function. The Strong Short-Range Force Between Nucleons. Cold-Dense Nuclear Matter (from deuteron to neutron-stars). A~10 57 tensor force, repulsive core, 3N forces

What did we learn recently about SRC ? The probability for a nucleon to have momentum ≥ 300 MeV / c in medium nuclei is ~25% More than ~90% of all nucleons with momentum ≥ 300 MeV / c belong to 2N-SRC. The probability for a nucleon with momentum MeV / c to belong to np-SRC is ~18 times larger than to belong to pp-SRC. 2N-SRC mostly built of 2N not 6 quarks or NΔ ΔΔ. All the non-nucleonic components can not exceed 20% of the 2N-SRC. Three nucleon SRC are present in nuclei.. PRL. 96, (2006) PRL (2006); Science 320, 1476 (2008). CLAS / HALL B EVA / BNL and Jlab / HALL A The dominant NN force in the 2N-SRC is the tensor force PRL 98, (2007).

np-SRC dominance ~18 % 12 C 2N-SRC Results (summary) The uncertainties allow a few percent of: more than 2N correlations Non - nucleonic degrees of freedom 2N –SRC dominance 18±5% 1±0.3% 12 C Sensitivity required: 1% of (e,e’p) 5% of (e, e’ p) with P miss >300 MeV/c

Looking for non-nucleonic degrees of freedom The signature of a non-nucleonic SRC intermediate state is a large branching ratio to a non-nucleonic final state. Breaking the pair will yield more backward Δ, π, k  1.f Nucleons 2N-SRC   5  o ~1 fm For the non –nucleonic component:

Search for cumulative Delta 0(1232) and Delta + + (1232) isobars in neutrino interactions with neon nuclei Ammosov, eAmmosov, et al. Journal of Experimental and Theoretical Physics Letters, Vol. 40, p.1041 (1984). Δ’s rates 5-10% of recoil N rates Nucl-th

a measurement of (e,e’ p back ) by the Yerevan group src

How to search for pre-existing Δs in CLAS data? (e, e’ Δ back ) and(e, e’ N Δ back )Search for backward emitted Δ, both to separate initial state from background multistep processes a)Look at x 1 b)Vary Q 2 and ω Search for forward emitted Δ ++ at x>1 By studying the dependence on x and A we can separate the charge exchange Δ ++ production (main effect for α =1 increasing with A ) and scattering off primordial Δ ++ ( larger x). Look for Δ ++ at large x, corresponding to the larger expected Δ - momentum in the nucleus.

~800 MeV/c ~400 MeV/c Colinear geometry : 3N-SRC Needs to detect two recoil nucleons GeV/c p and n 3N –SRC arise from two mechanisms: pair interactions 3N force Isospin ratios and selected kinematics may allow to separate them

19±4% 0.6±0.2% 2N 3N 1N >> 2N - SRC >> 3N – SRC. 0.6 / 19 ~ 3% (large uncertainty on this ratio)

How to search for these in the CLAS data? Inclusive measurement of two backward recoil nucleons (e, 2N back ) In coincidence with the scattered electron (e, e’ 2N back )

208 Pb(e,e’) / 3 He(e,e’) Is there a reduction of the a 2 for neutron rich nuclei ? a step toward neutron stars SystemAZN 3He He,12C,40Ca1 56Fe Ca Au Pb n-star A 2 (A / d) Available data: (±2%) 4.27 (±6%) 5.10 (±6%) a2(A/d)

Extrapolation factor ~10 Measured ratio Extrapolated ratio The limited acceptance allows determination of only two components of the pair c.m. momentum with very limited acceptance. Even the triple coincidence SRC experiment could be done better with a larger acceptance detector. R.B. WiringaR.B. Wiringa, R. Schiavilla, Steven C. Pieper, J. Carlson. Jun arXiv: [nucl-th]R. SchiavillaSteven C. PieperJ. Carlson Can we look for a signature of the l=2 pair in the relative angular distribution of the pair ? Can we learn more on the CM motion of the pair ?

Detailed study of the Fermi sea level ( the SRC onset). The transition from single particle to SRC phases

Available now: 12 C only Available now : Q 2 =2 only very limited CM momentum range (in 2 direction) only Available now: 12 C only

Detailed study on few body systems (Deuteron, 3He) These are interesting by themselves but also are important doorway to study complex nuclei. The clearly determined kinematics offered by these systems can be useful. 2N-SRC are dominant with T=0 np pairs. Fingerprints of the deuteron can be used to study 2N-SRC in nuclei. Effects related to EMC and CT can be tested on few body systems

Search for ΔΔ admixtures in the deutron Important also for the study of non-nucleonic componnets of SRC in nuclei. Measurements of tagged structure functions (electron scattering in coincidence with a fast backward proton or neutron) Important also for the study of EMC with the 12 GeV upgrade Measurements of the spin structure of SRC in the deuteron using polarized electron scattering off polarized or unpolarized deuteron Important also for the study of SRC in nuclei Some examples: Detailed study of FSI as a function of the final state particles, momenta, and Q 2 Important also for the study of CT, hadronization and medium modification to the nucleon form factors.

Q1: Is the strong interaction of small neutral (colorless) objects suppressed ? Q2: Can we produce small hadrons (PLC) ? Q3: Can we freeze the PLC long enough to observe the suppression of its interaction ? If the answers to all the questions above is positive we can expect a phenomenon known as Color Transparency. Q4: Where is the onset of CT ? (CT is a necessary condition for factorization of exclusive hard processes) Q5: What is the time / space structure of the transition from the PLC to a ‘normal’ hadron ? C olor T ransparency PLC

(e, e’ π) DATA: Jlab / Hall C B. Clasie et al. PRL (2007). solid : Glauber (semi-classical) dashed : Glauber +CT (quantum diff.) Larson et al, PRC 74, (2006) dot-dash : Glauber (Relativistic) dotted : Glauber +CT (quantum diff.) +SRC Cosyn et al. PRC 74, R (2006) Also: PRC 77, (2008) no CT with CT With CT with CT no CT with CT Dashed area: from Pion nucleus scattering Carroll et al., PLB 80, 319 (’79) Coherence length: fm Data from Hall C indicate that maybe the onset of CT is low enough to look for CT effects at the current JLab energy range

If CT is relevant at JLab energies one can look for suppression of the pion cloud and its interaction with the nuclear medium close to the point where a hadron is being produced in a hard process. e e’ d Study A(e, e’ Δ 0 ) as a function of Q 2 and A

A e e’ s 11

Hadronization Measure the multiplicity and the type of emitted particles in a large acceptance “backward direction ” in coincidence with the forward (large z) leading π +, π -, k +, k - particle. Difference in hadronization of different quarks Difference between hardonization in a free space and nuclear medium

Nuclear Matter in non - equilibrium condition Using hard processes to remove a single or a few nucleons from the nucleus creates a non-stable state. How does such a non-stable state decay to a stable system?

Data sets: E > 1 GeV, A>1, electron or photon beams

Plan of action White paper, seek for funding - Jan 2009 Exploration: 2009 Narrow down the effort to the most promising analysis projects 1full time experience postdoc at JLab. Use existing data summary files 1st stage analysis: developing analysis tools, Re-cooking 3full time experienced researchers at JLab. and up to 6 students Create new data summary files Full analysis effort at Jlab. and home institutes Use the new data summary files full time experimental and 1 theoretical researcher at JLab. and up to 6+1 students

Organization “steering committee” Core of postdocs and students at Jlab Groups of Postocs and students at the universities Weekly conferences calls Two annual meetings Open for everyone interested, Please join the initiative

How to search for these in the CLAS data? Inclusive measurement of two backward recoil nucleons (e, 2N back ) In coincidence with the scattered electron (e, e’ N) x>2 (e, e’ 2N back ) q E N MAX (A-1 recoil) Notice that FSI will not fill the gap

208 Pb ? Is there a reduction of the a 2 for neutron reach nuclei ? a step toward neutron stars

A large acceptance detector allows tagging of the DIS event EMC High nuclear density tagging : A recoil high momentum nucleon to the backward hemisphere is a signature of 2N-SRC i.e large local nuclear density. Due to the dominance of np-SRC pairs: a recoil neutron tags the proton structure function a recoil proton tags the neutron structure function Flavor tagging : Identifying a π + or π - with a large z can point to the flavor of the struck quark ( u or d). Recoil and forward tagging allows the study of u, d in p, n

How to search for these in the CLAS data? (e, e’ Δ back ) or even (e, e’ p Δ back ) (e, e’ n Δ back ) X B >1 and X B <1

How to search for these in the CLAS data? By studying the dependence on x and A we can separate the charge exchange Δ ++ production (main effect for α =1 increasing with A ) and scattering off primordial Δ ++ ( larger x).