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Large Acceptance Detector (LAD) for 12 GeV Hall C

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  1. Large Acceptance Detector (LAD) for 12 GeV Hall C Exclusive measurements of Short Range Correlations and more Physics opportunities in Hall C at 12 GeV Hall C Meeting, Monday, August 4, 2008 Jefferson Lab, Newport News, VA USA Eli Piasetzky Tel Aviv University, ISRAEL

  2. Large Acceptance Detector (LAD) Large solid angle multi particle (charged and neutral) detector HMS e’ SHMS p,π,… e Coverage of a large fraction of the hemisphere (“backward” =4π-forward) consistent with the forward spectrometers. Ability to detect multi-charge particles with good PID and moderate momentum resolution. Ability to detect neutrons with high efficiency. Ability to operate at a luminosity of 1036-1038 cm-2 sec-1 (10-1000 times the planned luminosity for CLAS).

  3. The physics driving the LAD detector Short Range Correlations (SRC) EMC Hadronization Study of GPDs Nuclear Matter in non - equilibrium condition

  4. 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 fo the next generation of SRC measurements 0.1 – 1 % of (e, e’ p). [(0.5-5)% of (e,e’p) with Pmiss>300 MeV/c]

  5. 2N 1N >> 2N - SRC >> 3N – SRC. 0.6±0.2% 19±4% 3N cure XB>2 PR 08-14 / PAC 33 or

  6. ~800 MeV/c ~400 MeV/c Needs large acceptance multi particle detector ~800 MeV/c ~400 MeV/c Exclusive measurement: From (e,e’p) + N to (e,e’p)+2N From triple coincidence (2N SRC) to 4 fold coincidence (3N SRC) star geometry Need to detect two recoil nucleons Colinear geometry : 0.3-1 GeV/c p and n

  7.  4o 2N-SRC 1.f ~1 fm Nucleons For a 1 fm separation, the central density is about 4 times the nuclear central density • Are the nucleons in the SRC pair different from free nucleons (e.g size,shape, mass, etc.) ? Are they nucleons ?

  8. Looking for non-nucleonic degrees of freedom  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. Looking for non-nucleonic degrees of freedom Expected Δ’s rates 5-10% of recoil N Detected by spectrometer 4 fold coincidence 2 particles in the backward detector 3-5 fold coincidence 2-4 particles in the backward detector

  10. Expected Δ’s rates 5-10% of recoil N

  11. Needs large acceptance multi particle detector Kinematics pΔ=640 MeV/c With SHMS(e) and HMS(p) acceptances and Γ=110 MeV Δ

  12. 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 R.B. Wiringa, R. Schiavilla, Steven C. Pieper, J. Carlson . Jun 2008. arXiv:0806.1718 [nucl-th]

  13. 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

  14. 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 hadronization in free space and the nuclear medium

  15. GPDs Hall B Hall C With a large acceptance detector: With a deuteron one can measure simultaneously both protons and neutrons by detecting the recoil neutron or proton, respectively ? low mass πN system- a test of chiral symmetry

  16. 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?

  17. p e’ e p Δ Large Acceptance Detector Multi particle detection Particle ID Large solid angle- 4π – non-symmetric opening in the forward hemisphere Cover up to ~1800 Large (full) luminosity Can operate in coincidence with small solid angle, high resolution spectrometer / spectrometers

  18. P Phase space coverage CLAS Large –angle TOF scintillators TOF HMS @ 120 TOF Counters SHMS @5.50 Target Chamber TOF Counters

  19. Phase space coverage Beam View Beam in Add two sectors at beam high

  20. Beam Left View Sector #1 Sector #3 Sector 1: 82-1420 Sector 2: 97-1290 Sector 3: 117-1720 Polar angle acceptance Sector #2

  21. Beam Right View Sector #4 Sector #6 Polar angle acceptance Sector 4: 75-1420 Sector 5: 97-1060 Sector 6: 77-1030 Sector #5

  22. 1420 1720 Sector #4 Sector #6 Sector #1 n-detectors Sector #3 n-detectors Sectors 2 and 5 are not shown

  23. 5 neutron detection PID 10 cm 5cm 22 X (370-450) X 5.08 cm3 ~140 counters With ~ 80 counters / layer we can cover the beam height ±80 cm behind sectors 3 and 6. 10x(10-25)x(100-160) cm3

  24. PID p d beam π ~140 counters TOF 22 X 370-450 X 5.08 cm3 PID can be better done by a partial acceptance (sectors 3 and 6) where more than one counter is on the line of sight. at about 4 m from the target

  25. Luminosity: singles rates (The large counters are ~ 1m2 ) 3 1033 cm-2 sec-1 ----> 1 kHz/m2 6 1036 cm-2 sec-1 ----> 2 MHz (the planned luminosity for 12GeV CLAS is 1035) (The Hall A E01-015 luminosity was 5·1037 )

  26. Luminosity: rates Rate of (e,e’p) with Pmiss=300-600 MeV/c, Hall A experiment E01-015: 0.2 Hz 6 1036 cm-2 sec-1 / 5 1037 cm-2 sec-1 = 1 / 10 LAD: (e, e’ppp) ~ 0.2 ·1% ·0.1 → ~1 events / hr (e,e’p) rate ~100 events / week (e,e’ppp)/(e,e’p) Luminosities ratio (higher rates taking into account the spectrometers solid angles)

  27. Luminosity: Signal/BG Pmis=“300” MeV/c (Signal : BG= 1.5:1) Pmis=“400” MeV/c (Signal : BG= 2.3:1) TOF corrected by the momentum determination based on Eloss Pmis=“500” MeV/c (Signal : BG= 4:1) Δt~15 nsec Hall A experiment E01-015

  28. Luminosity: number of pairs Average number of hits per event: 2MHz ·15 nsec = 3% 3%·140 = 4 hits/event (6 pairs/event) For each pair of identified protons with momentum within physically possible range calculate: Only pairs with are relevant BigBite is ~100msr, assuming 1Sr / 2π i.e <1 pair on average

  29. Luminosity: Signal/BG (e, e’pp)/(e,e’p) Hall A experiment E01-015: (e, e’ppp)/(e,e’p) in LAD Hall C: (assuming the worst case: that an individual recoil proton does not have any directional correlation with Pmiss.) (calculation for a single counter:) To be sensitive to 1% of the (e, e’p) we need to be sensitive to about 5% of the (e,e’p) with Pmiss between 300 -600 MeV/c (the spectrometer based trigger) .

  30. What can be done with LAD that cannot be done with the planned 12 GeV CLAS ? Up to ~100x the planned luminosity for the 12 GeV CLAS (1035). Backward coverage up to 1720 (the planned 12 GeV CLAS covers up to 1350 ) Possible trigger by two high resolution spectometers

  31. Quo vadis ? 2008 Conceptual detector design Simulations A physics proposals on SRC to the next PAC Other proposals ?

  32. Acknowledgment Discussions and ideas exchange with: Stepan Stepanyan Sebastian Kuhn Larry Weinstein Steve Wood Rolf Ent Preliminary design Mike Fowler Dave Kashy Paul Brindza

  33. SRC in nuclei Roadmap What is the role played by short range correlation of more than two nucleons ? How to relate what we learned about SRC in nuclei to the dynamics of neutron star formation and structure ?  5o 2N-SRC SRC in nuclei 1.f ~1 fm 1.7 fm 1.7f Nucleons o = 0.16 GeV/fm3 • Are the nucleons in the SRC pair different from free nucleons (e.g size,shape, mass, etc.) ? Are they nucleons ? NN interaction: what is the role played by the repulsive core ?

  34. ΔE PID d p n-detection efficiency ~20% +15%(?) π TOF Also E vs. ΔE 5 cm beam 20 cm beam LAC LAC ~200 counters

  35. Quo vadis ? Short Range Correlations (SRC) EMC Hadronization Study of GPDs Nuclear Matter in non - equilibrium condition 2008 2-3 physics proposals to the 12 GeV PAC Conceptual detector design

  36. Large Angle Calorimeter (LAC) 2 mm lead foil 1.5 cm plastic Scintillator 33 layers neutron momentum [GeV/c]

  37. The CLAS as a 4π-forward detector For the new 12 GeV clas: The current magnet, Drift chambers, and scintillator counters are not to be used. Need new power supplies, and electronics Require a careful, non trivial dismount of the current detector at Hall B and non trivial setup at hall c. Improve n-detection

  38. TOF CAL CER DC3 DC2 DC1 The CLAS as a 4π-forward detector

  39. CLAS 3-D View

  40. SRC in nuclei Roadmap What is the role played by short range correlation of more than two nucleons ? How to relate what we learned about SRC in nuclei to the dynamics of neutron star formation and structure ?  5o 2N-SRC SRC in nuclei 1.f ~1 fm 1.7 fm 1.7f Nucleons o = 0.16 GeV/fm3 • Are the nucleons in the SRC pair different from free nucleons (e.g size,shape, mass, etc.) ? Are they nucleons ? NN interaction: what is the role played by the repulsive core ?

  41. The uncertainties allow a few percent of: more than 2N correlations Non nucleonic degrees of freedom 12C: 2N-SRC np-SRC 20±4.5 % 18±4.5 % pp-SRC 0.95 ± 0.2 % nn-SRC A single “particle” in an average potential 0.95 ± 0.2 % 80±4.5%

  42. Identifying Future Experiments Looking for SRC with more than 2 nucleons:

  43. Identifying Future Experiments Looking for SRC with more than 2 nucleons: The problems: The cross sections are small. 1N >> 2N - SRC >> 3N – SRC. Questions What is the signature for 3N correlation ? star geometry : What is the difference from two 2N correlations ? What is the expected isospin structure of the 3N ?

  44. Identifying Future Experiments Looking for SRC with more than 2 nucleons: The problems: The cross sections are small. 1N >> 2N - SRC >> 3N – SRC. The cure for 1N background is : large pmiss and/or large XB The cure for 2N-SRC: XB>2 or suppression of the 2N-SRC at prel=300-600 MeV/c for nn or pp pairs.

  45. ~800 MeV/c ~400 MeV/c ~800 MeV/c ~400 MeV/c Identifying Future Experiments Looking for SRC with more than 2 nucleons: Colinear geometry : Initial configurations A very strong isospin dependence is expected for the 2N part. For the 3N? The 2N-SRC interaction is suppressed, opening a window of opportunity to identify 3N correlation. The signal of today is tomorrow’s background

  46. ~800 MeV/c ~800 MeV/c Identifying Future Experiments Looking for SRC with more than 2 nucleons: Colinear geometry FSI are strong function of θ SRC are not

  47.  5o 2N-SRC 1.f ~1 fm Nucleons Identifying Future Experiments Looking for non-nucleonic degrees of freedom Breaking the pair will yield more backward Δ, π , k The signature of a non-nucleonic SRC intermediate state is a large branching ratio to a non nucleonic final state.

  48. Looking for non-nucleonic degrees of freedom In coincidence with (e, e’p), as a function of the missing momentum we want to detect; p, n, π-, π+ k - triple coincidence

  49. Identifying Future Experiments Looking for non-nucleonic degrees of freedom “np”  pn • pΔ0 p π- p “pp”  pp • pΔ+ p π+ n 4 fold coincidence Expected rates 5-10% of recoil N

  50. Kinematics Δ