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Physics with low energy recoil detector and options for instrumentation for the CLAS12

Physics with low energy recoil detector and options for instrumentation for the CLAS12. S. Stepanyan (JLAB) CLAS12 European Workshop  February 25-28, 2009, Genova, Italy. Few physics topics with low energy recoil ( ) detector neutron structure

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Physics with low energy recoil detector and options for instrumentation for the CLAS12

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  1. Physics with low energy recoil detector and options for instrumentation for the CLAS12 S. Stepanyan (JLAB) CLAS12 European Workshop  February 25-28, 2009, Genova, Italy

  2. Few physics topics with low energy recoil ( ) detector • neutron structure • nuclear structure (see also K. Joo’s talk) • meson spectroscopy • Options for a recoil detector • RTPC • LPMWPC&SSD CLAS12 European Workshop  February 25-28, 2009, Genova, Italy

  3. Neutron target and accessible physics • Free neutrons decay in 15 min • Can we explore the structure of the neutron if all we have are neutrons bound in nuclei? – nuclear model uncertainties • Low energy spectator tagging can be a solution for a neutron target: • PDF at large x • d/u at large x • quark-hadron duality on neutron • neutron elastic scattering • neutron DVCS S. Bueltman et al., E12-06-113 CLAS12 European Workshop  February 25-28, 2009, Genova, Italy

  4. d/u ratio at x  1 F2n/F2p = F2d/F2p -1??? CLAS12 European Workshop  February 25-28, 2009, Genova, Italy

  5. Modifications to Simple Spectator Picture Binding Effects “BoNuS” Final State Interactions CLAS12 European Workshop  February 25-28, 2009, Genova, Italy

  6. e n p Spectator Tagging with BoNuS RTPC E = 4.223 GeV <Q2> = 1.19 (GeV/c)2 * CLAS12 European Workshop  February 25-28, 2009, Genova, Italy

  7. Coherent DVCS Incoherent DVCS DVCS on nuclei Coherent DVCS • Nuclear GPDs - partonic structure of nuclei, • momentum and spatial distribution of quarks in nuclei, generalized EMC effect • Incoherent DVCS • bound nucleon GPDs – nuclear medium effects, modification with respect to free nucleon ones Both will require low energy recoil detector CLAS12 European Workshop  February 25-28, 2009, Genova, Italy

  8. Nuclear DVCS Coherent and incoherent were not cleanly separated. CLAS12 European Workshop  February 25-28, 2009, Genova, Italy

  9. CLAS experiment E08-024 (K. Hafidi et al.) 4He nucleus For nucleon DVCS: CLAS12 European Workshop  February 25-28, 2009, Genova, Italy

  10. Meson spectroscopy Production on hydrogen - physics background from associated baryon resonance production CLAS/g6:gp’np+p+p- D(1232) N(1520) N(1680) D, N* a2(1320) Strong kinematical cuts and a complex PWA are required CLAS12 European Workshop  February 25-28, 2009, Genova, Italy

  11. Spectroscopy in coherent production on nuclei Method to eliminate the baryon background All three charged modes can be studied using gas targets 3H, 3He, and 4He CLAS12 European Workshop  February 25-28, 2009, Genova, Italy

  12. Example: coherent production on 4He Scattering off a spin and isospin zero target works as a spin and parity filter with JLAB experiment E07-009, Stepanyan et al. CLAS12 European Workshop  February 25-28, 2009, Genova, Italy

  13. Coherent production of p0h and p0h’ off 4He Only C=-1 w-exchanges is allowed, Natural Parity Exchange (NPE) The helicity of the produced state will be that of the incoming photon, l=lg, production of p0h (p0h’) in S-wave is forbidden Test for above assumptions CLAS12 European Workshop  February 25-28, 2009, Genova, Italy

  14. CLAS12 central detector 5T SC Solenoid Magnet Silicon Vertex Tracker Scintillator Counters, dt=50ps Low (200 MeV/c) energy protons in CLAS12 CD (M. Ungaro, GEMC) CLAS12 European Workshop  February 25-28, 2009, Genova, Italy

  15. g g p0 p0 qgg qgg g g CLAS12 Central detector Protons Deuterons Specialized detector is needed for a broad physics program requiring low energy recoil detection CLAS12 European Workshop  February 25-28, 2009, Genova, Italy

  16. BoNuS* RTPC** BoNuS Region VIPs 0.07 0.2 GeV/c Helium/DME at 80/20 ratio 7 atm D2 gas Drift Region Gas Electron Multiplier Readout pads and electronics *BoNuS = Barely off-shell Nucleon Scattering **RTPC = Radial Time Projection Chamber CLAS12 European Workshop  February 25-28, 2009, Genova, Italy

  17. =8mm z =4º =1.4º   Performance and limitations of BoNuS RTPC e- reconstructed in CLAS & RTPC dE/dx from charge along the track Reasonable 3-vector reconstruction Reasonable PID for a proton Low rate of DAQ - ~500Hz Poor PID for high mass fragments – gain uniformity of GEM pads CLAS12 European Workshop  February 25-28, 2009, Genova, Italy

  18. BoNuS-II (for EG6 run in October) Lightweight (carbon-foam composite structure) rungs for stress-free, self support of GEMs – to avoid “wrinkles” Ground and cathode foils, each 6mm thick Target region - new cell – ID 4mm, 30mm thick wall Open, 2p geometry – only 80% is accessible due to the GEM and readout pad sizes CLAS12 European Workshop  February 25-28, 2009, Genova, Italy

  19. Expected performance of BoNuS-II • Better gain uniformity – better PID: • new GEM foils • stress free support • calibration system (a-source and elastic scattering) • Lower momentum threshold (250 MeV for a’s) • thinner target walls • Increased DAQ rate - 0.5 kHz to 5 kHz • new RCUs, crate, backplane … work is done at INFN Genova (R. De Vita, M. Battaglieri, S. Minutoli) Expected PID with fully calibrated RTPC CLAS12 European Workshop  February 25-28, 2009, Genova, Italy

  20. DAQ with new Readout Control Unit board Rx - PASA - ALTRO Max event rate 7 kHz FEC 128 ch 13 Front-end bus ( 200 MB / s ) FEC 128 ch 2 RCU FEC 128 ch 1 Data Proc. and Memory Tx DDL ( 200 MB/s ) Bus controller ( conf. & R/O ) DETECTOR DAQ int. (DDL-SIU) DCS ( 1 MB/s ) FEC 128 ch 13 BOARD Controller DCS int. (Ethernet) Local Monitor and Control TTC optical Link (Clock, L1 and L2 ) Trigger and Timing circuit Trigger int. (TTC-RX) FEC 128 ch 2 Control Network (I2C-serial link) FEC 128 ch 1 CLAS12 European Workshop  February 25-28, 2009, Genova, Italy

  21. LPAC&SSD* (NIKHEF NIM A409, 1998) Sci E SiY DE or E, y SiX DE or E, x Isobutane@ 7 mbar AC DE, t(dt=100ps), y Entrance foil – 1mm * Low-pressure avalanche chamber and silicon strip detectors CLAS12 European Workshop  February 25-28, 2009, Genova, Italy

  22. LPMWPC (JLAB FF detector NIM A426, 1999) Detector was developed by YerPhI group for detection of fission fragments for studies of the absolute photofission cross sections at MAX-lab (Lund, Sweden) and for hypernuclear experiments in Hall C at JLAB Two windowless gas proportional counters with three electrodes, operating as a parallel plate (wire planes) avalanche counter Silicon strip detectors to measure full energy Options for running the chamber with helium, helium/heptane (99%/1%), or helium/hydrogen (86%/15%) are under studies (YerPhI/Idaho) CLAS12 European Workshop  February 25-28, 2009, Genova, Italy

  23. Test of LPMWPC in Hall B Two symmetric arms placed on top and bottom of the beam centerline The inner chambers active area - 10.5 x 21cm2 Distance of the anode plane from the beam line - 3 cm. The outer chambers - 21 x 21 cm2 Target - 209Bi with a thickness of 2 mg/cm2. CLAS12 European Workshop  February 25-28, 2009, Genova, Italy

  24. RTPC and LPMWPC CLAS12 European Workshop  February 25-28, 2009, Genova, Italy

  25. Summary Broad physics program, ranging from nucleon and nuclear structure to meson spectroscopy, can be accessed with CLAS12 and a low energy recoil detector Exploration of some of these physics topics is started with CLAS and BoNuS RTPC 2nd generation RTPC will have much improved characteristics for PID and data rate (3rd generation detector for CLAS12 can have ~2p azimuthal coverage) Option with LPMWPC must be carefully studied, specially for the detection of a-s and the heavier fragments from solid targets CLAS12 European Workshop  February 25-28, 2009, Genova, Italy

  26. Backup slides CLAS12 European Workshop  February 25-28, 2009, Genova, Italy

  27. CLAS12 27 Pre-shower calorimeters Low Threshold Cherenkov Counters CLAS12 Solenoid Electromagnetic calorimeters Central Detector Drift Chambers High Threshold Cherenkov Counter (HTCC) TOF Counters CLAS12 Torus CLAS12 European Workshop  February 25-28, 2009, Genova, Italy

  28. EMC effect 4He/D Gomez et al., PRD49, 1994 Medium Modification S. Liuti & S. K. Taneja PRC72, 2005 • The asymmetry ratio for DVCS enhances the EMC effect. • The deviations from unity is mostly due to convolutions with k. CLAS12 European Workshop  February 25-28, 2009, Genova, Italy

  29. Electroproduction at “0” degrees [photoproduction] Reaction ep’pggggX at 5.76 GeV (e1-6 and e1-DVCS experiments) Missing transverse momentum distribution for |MX|2<0.1 GeV Invariant mass of 2 photon pairs in the reaction ep’pgggg(e’) • Data were taken with loosely defined electron trigger CLAS12 European Workshop  February 25-28, 2009, Genova, Italy

  30. Reaction ep’pp0p0(e’) andep’pp0h(e’) CLAS DVCS CLAS e1-6 • Note: • - data were taken with unfavorable trigger conditions • - transferred momentum squared, |t|>0.2 (GeV/c)2 (proton momentum >0.4 GeV/c) • - spectra contain the baryon background CLAS12 European Workshop  February 25-28, 2009, Genova, Italy

  31. Event display of RTPC: BoNuS data on D2 and 4He 2xQD < QHe Deuterium Target Helium Target CLAS12 European Workshop  February 25-28, 2009, Genova, Italy

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