Analyzing CLAS / Hall B Data to Extract New Results on QCD Nuclear Physics

1. 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

2. 1903-1905 Schumacher 1920-1939 University of Chicago 1960s,1970s The Hebrew University 1994 - Tel Aviv University MEGIDDO: THE FLAGSHIP OF TEL AVIV UNIVERSITY DIGS A mound with 32 cities one on top of the other

3. 1903-1905 Schumacher 1920-1939 University of Chicago 1960s,1970s The Hebrew University 1994 - Tel Aviv University

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

5. 2N-SRC  5o 1.f 1.7f o = 0.16 GeV/fm3 Nucleons Nucleon Short Range Correlations (SRC) ~1 fm 1.7 fm A~1057 What SRC in nuclei can tell us about: High – Momentum Component of the Nuclear Wave Function. The Strong Short-Range Force Between Nucleons. tensor force, repulsive core, 3N forces Cold-Dense Nuclear Matter (from deuteron to neutron-stars).

6. 1 2 4 3 1 6 4 2 3 6 5 5 What did we learn recently about SRC ? CLAS / HALL B The probability for a nucleon to have momentum ≥ 300 MeV / c in medium nuclei is ~25% . PRL. 96, 082501 (2006) More than ~90% of all nucleons with momentum ≥ 300 MeV / c belong to 2N-SRC. The probability for a nucleon with momentum 300-600 MeV / c to belong to np-SRC is ~18 times larger than to belong to pp-SRC. The dominant NN force in the 2N-SRC is the tensor force. PRL 98,132501 (2007). 2N-SRC mostly built of 2N not 6 quarks or NΔΔΔ. All the non-nucleonic components can not exceed 20% of the 2N-SRC. EVA / BNL and Jlab / HALL A Three nucleon SRC are present in nuclei. PRL 162504(2006); Science 320, 1476 (2008).

7. 2N-SRC Results (summary) The uncertainties allow a few percent of: more than 2N correlations 1±0.3% Non - nucleonic degrees of freedom 12C 12C 18±5% 2N –SRC dominance np-SRC dominance ~18 % Sensitivity required: 1% of (e,e’p) 5% of (e, e’ p) with Pmiss>300 MeV/c

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

9. Δ’s rates 5-10% of recoil N rates Nucl-th 0901.2340 Search forcumulative Delta 0(1232) and Delta + + (1232) isobars in neutrino interactions with neon nuclei Ammosov, et al. Journal of Experimental and Theoretical Physics Letters, Vol. 40, p.1041 (1984).

10. src a measurement of (e,e’ pback) by the Yerevan group

11. How to search for pre-existing Δs in CLAS data? Search for backward emitted Δ, both (e, e’ Δback) and (e, e’ N Δback) to separate initial state from background multistep processes • Look at x<1 and x>1 • Vary Q2 and ω Search for forward emitted Δ++ at x>1 Look for Δ++ at large x, corresponding to the larger expected Δ - momentum in the nucleus. 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).

12. ~800 MeV/c ~800 MeV/c ~800 MeV/c ~400 MeV/c 3N-SRC 3N –SRC arise from two mechanisms: pair interactions 3N force Isospin ratios and selected kinematics may allow to separate them Colinear geometry : Needs to detect two recoil nucleons 0.3-1 GeV/c p and n

13. 1N >> 2N - SRC >> 3N – SRC. 0.6±0.2% 2N 0.6 / 19 ~ 3% 3N 19±4% (large uncertainty on this ratio)

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

15. a2(A/d) 1.7 3.33 (±2%) 4.27 (±6%) 5.10 (±6%) 208Pb(e,e’) / 3He(e,e’) Is there a reduction of the a2 for neutron rich nuclei ? a step toward neutron stars A2(A / d) Available data:

16. Even the triple coincidence SRC experiment could be done better with a larger acceptance detector. Measured ratio Extrapolation factor ~10 The limited acceptance allows determination of only two components of the pair c.m. momentum with very limited acceptance. Extrapolated ratio 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 ? R.B. Wiringa, R. Schiavilla, Steven C. Pieper, J. Carlson . Jun 2008. arXiv:0806.1718 [nucl-th]

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

18. Available now: 12C only Available now : Q2=2 only very limited CM momentum range (in 2 direction) only Available now: 12C only

19. 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

20. Some examples: 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 Detailed study of FSI as a function of the final state particles, momenta, and Q2 Important also for the study of CT, hadronization and medium modification to the nucleon form factors.

21. ColorTransparency PLC ? 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 ?

22. 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 (e, e’ π) DATA: Jlab / Hall C B. Clasie et al. PRL 242502 (2007). Coherence length: 0.2-0.5 fm with CT with CT with CT no CT no CT no CT with CT With CT Dashed area: from Pion nucleus scattering Carroll et al., PLB 80, 319 (’79) no CT no CT dot-dash : Glauber (Relativistic) dotted : Glauber +CT (quantum diff.) +SRC Cosyn et al. PRC 74, 062201R (2006) Also: PRC 77, 034602 (2008) solid : Glauber (semi-classical) dashed : Glauber +CT (quantum diff.) Larson et al , PRC 74, 018201 (2006)

23. 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 Study A(e, e’ Δ0) as a function of Q2 and A d

24. e’ e s11 A

25. 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

26. 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?

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

28. 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 2010-2011 3full time experienced researchers at JLab. and up to 6 students Create new data summary files Full analysis effort at Jlab. and home institutes 2011-2015 3full time experimental and 1 theoretical researcher at JLab. and up to 6+1 students Use the new data summary files

29. 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

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

32. 208Pb ? Is there a reduction of the a2 for neutron reach nuclei ? a step toward neutron stars

33. EMC A large acceptance detector allows tagging of the DIS event 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

34. How to search for these in the CLAS data? (e, e’ Δback) or even XB>1 and XB<1 (e, e’ n Δback) (e, e’ p Δback)

35. 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).