Cascade Spectroscopy at CLAS

Transcription

1 Cascade Spectroscopy at CLAS D.P. Weygand Thomas Jefferson National Accelerator Facility 12/1/2005 D.P. Weygand Cascade Workshop 1

2 Outline: Ξ* Resonances at CLAS Ghosts of Ξ s Past Ξ(1620), High Mass Ξ* Resonances Ghosts of Ξ s Present CLAS g6,g11,eg3 Ghosts of Ξ s Future super-g, CLAS12 12/1/2005 Cascade Workshop 2

3 Ξ (1620) Phys. Rev. D 16, (1977) 12/1/2005 Cascade Workshop 3

4 Phys. Rev. Lett. 51, (1983) Ξ(1820) Ξ(2030) Ξ(2250) Ξ(2370) Ξ(2500) Ξ(1950) Ξ(2120) 12/1/2005 Cascade Workshop 4

5 12/1/2005 Cascade Workshop 5

6 Cebaf Large Acceptance Spectometer Beam line and the target Drift chambers 6 Superconducting Electromagnetic toroidal coils calorimeters Bremsstrahlung tagged photon facility, photon energy resolution ~0.2% (New Tagger Energy Calibration) TOF counters Cherenkov counters 12/1/2005 Cascade Workshop 6

7 Start Counter: /1/2005 Cascade Workshop 7

8 g 6a-b g6a: June, 1998 g6b: July, 1999 J. Price, J. Ducote, B.M.K. Nefkens (UCLA) g6a σ ~ 3.5 +/- 1 nb g6b Missing Mass/K + K + GeV/c Missing Mass/K + K + GeV/c 2 Missing Mass/K + K + GeV/c 2 12/1/2005 Cascade Workshop 8

9 g 6c Sept 2001 ~2.7 pb -1 E γ ~5 GeV 12/1/2005 Cascade Workshop 9

10 g 6c Eγ ~ 5.4 GeV γp K + K + K - X γp K + K + K-Λ/Ε 12/1/2005 Cascade Workshop 10

11 Start Counter: 2005 Y.G. Sharabian et al. (to be published NIM) 12/1/2005 Cascade Workshop 11

12 CLAS g 11 γp K + K + X May, 2005 ~75 pb -1 ε ~ 10% γ K + Κ - K + p Y* Ξ 12/1/2005 Cascade Workshop 12

13 Production Mechanism Ε γ > 3.4GeV γp K + K + Ξ Ε γ > 3.4GeV γp K + nk 0 Events/10MeV/c 2 M(Ξ K s+ ) Events/10MeV/c 2 M(Ξ K 12+ ) M(nK 0 ) 12/1/2005 Cascade Workshop 13

14 g11 γp K + K + Ξ -, Ξ - π - (Λ) 12/1/2005 Cascade Workshop 14

15 Simulation: γp K + Y* Y* X K + cos θ K s cos θ K f M(ΞK f ) M(ΞK s ) 12/1/2005 Cascade Workshop 15

16 Ξ - differential Cross section: dσ /d cos(θ Ξ ) /1/2005 Cascade Workshop 16

17 Ξ(1321) cross section: g 11 PRELIMINARY 12/1/2005 Cascade Workshop 17

18 γp K + K + Ξ - *, Ξ - * π - (Ξ 0 ) PRELIMINARY MM(K + K + π - ) M(Ξ 0 π - ) Shaded events: Background from out of target events M(Ξ 0 π - ) Background subtracted background subtracted 12/1/2005 Cascade Workshop 18

19 Kinematic Fit Ξ* Kinematic Fit M(Ξ 0 π - ) GeV/c 2 MM/K + K + π - GeV/c 2 12/1/2005 Cascade Workshop 19

20 cos HEL θ π VS M(Ξ 0 π - ) Preliminary Acc. corrected ~ Ξ(1530) ~ Ξ(1620) 12/1/2005 Cascade Workshop 20

21 M(K + 1,2) π - (GeV/c 2 ) 12/1/2005 Cascade Workshop 21

22 WA89 Eur.Phys.J.C5: , /1/2005 Cascade Workshop 22

23 eg 3 γd ΞπK K L ~100 pb -1 π + 12/1/2005 Cascade Workshop 23

24 7% of total exposure tight Λ mass cuts p π - DOCA cuts 50,000 Λ π events eg 3 : Intermediate State - Λ 12/1/2005 Cascade Workshop 24

25 Intermediate State Ξ - Missing mass above two kaon threshold a) additional track dislocated vertex 12/1/2005 Cascade Workshop 25

26 Hall B Schedule Date Experiment days Energy (GeV) Rating Polarization? /13-12/22/05 e8-bonus 25 4, 5.4 A- yes 2006 eg4-gdh A High g9a-frost A- circ/ linear g12 35 >5.75 A - e1-dvcs(b) A High g9b-frost A- circ/linear eg5-dvcs A High TPE 5 >5.75 A- - ===================================================================== SUM 268 (195 unscheduled) V. Burkert : CLAS Collaboration Meeting, October /1/2005 Cascade Workshop 26

27 Outlook for 6 GeV Cryomodule refurbishment In preparation for the 6 GeV program, we have started cryomodule refurbishment. Refurbishment entails the the removal of a low performance module from the accelerator opening opening the module, reprocessing the cavities and putting putting the cryomodule together and Installing the cryomodule in the accelerator H. Areti: CLAS Collaboration Meeting, October /1/2005 Cascade Workshop 27

28 Preshower Calorimeter CLAS 12 GeV Forward Cerenkov (LTCC) Forward Drift Chambers Superconducting Torus Magnet Forward Calorimeter Forward Time-of-Flight Detectors Inner Cerenkov (HTCC) Central Detector CLAS12 12/1/2005 Cascade Workshop 28

29 CLAS 12 Central Detector TOF light-guide Flux return Silicon Vertex Tracker Superconducting solenoid coil (B max = 5T) 12/1/2005 Cascade Workshop 29 1m Central TOF

30 CLAS12 - Design Parameters Central Detector Forward Detector Forward Central Detector Detector Angle range Tracks Photons NA Resolution δp/p p δp T /p T = 0.03 δθ (mr) <1.0 8 δφ (mr) <3.0 2 Photon detection Energy (MeV) >150 NA δθ (mr) 4 (1GeV) NA Neutron detection N eff Particle ID e/π Full range NA π/p Full range < 1.2 GeV/c π/k Full range < 0.65 GeV/c K/p < 4 GeV/c < 0.90 GeV/c π 0 γγ Full range NA η γγ Full range NA 12/1/2005 Cascade Workshop 30

31 CLAS12: Silicon Vertex Detector Silicon Vertex Tracker 3 double-sided layers of stereo strip readout On-board ADCs strip pitch: mm 45,000 readout channels Δz ~ 100 μm 12/1/2005 Cascade Workshop 31

32 CLAS12 Low Q 2 Spectrometer PbWO 4 or PbF 2 Calorimeter 12/1/2005 Cascade Workshop 32

33 CLAS12 Low Q 2 Spectrometer 12/1/2005 Cascade Workshop 33

34 Summary PAST: CLAS: First Observation of Ξ photoproduction (g6 a,b,c) PRESENT: g11: High integrated luminosity Sensitive to resonance (missing) masses up to ~1650 MeV/c2 eg3: High integrated luminosity, Direct observation of Ξ states FUTURE: super-g: High integrated luminosity Sensitive to resonance (missing) masses up to ~2000 MeV/c2 CLAS12 12/1/2005 Cascade Workshop 34