1. High Performance PbWO 4 - Lead Glass Hybrid Calorimeter at Jefferson Lab M. Kubantsev ITEP, Moscow, Russia/Northwestern University, Evanston, USA A. Gasparian NC A&T State University Greensboro, NC USA I.Larin ITEP, Moscow,Russia for the PrimEx Collaboration Outline 1.Requirements for the Calorimeter 2.The HYCAL calorimeter design 3. Physics run performance 4.Summary.

2. Calor-2006, June 05M.Kubantsev ITEP/NWU2 Requirements for the Calorimeter Forward electro-photoproduction of neutral mesons (  o   ) @ 1- 10 GeV requires:  High energy resolution;  High position resolution;  Good photon detection efficiency @ few GeV;  Large geometrical acceptance.  o life-time measurement at JLab (the PrimEx experiment E-02-103): ( Pr ) peak  0.3 mrad

3. Calor-2006, June 05M.Kubantsev ITEP/NWU3 Design Concept and Resolutions  Invariant Mass Resolution Angular Resolution

4. Calor-2006, June 05M.Kubantsev ITEP/NWU4 Design Concept Resolution + Budget PbWO4 crystal Pb – glass Cherenkov Detectors detectors

5. Calor-2006, June 05M.Kubantsev ITEP/NWU5 Design Concept HYCAL with veto Modules: PWO: 34x34–4 = 1152 LG: 4x6x24 = 576

6. Calor-2006, June 05M.Kubantsev ITEP/NWU6 PbWO 4 Crystal Dimensions Dimensions: 20.5 x 20.5 x 180.0 mm 3 Tolerances (mm): 20.5 + 0.0 - 0.1 180.0 + 0.3 -0.0 Specified Measured

7. Calor-2006, June 05M.Kubantsev ITEP/NWU7 PbWO 4 Crystal Optical Properties Optical Transparency @ 360 nm @ 420 nm

8. Calor-2006, June 05M.Kubantsev ITEP/NWU8 HYCAL – The Hybrid Calorimeter Detector assembly and preparation tests

9. Calor-2006, June 05M.Kubantsev ITEP/NWU9 HYCAL Calibration Scheme of calorimeter irradiation with tagged photon beam during calibration

10. Calor-2006, June 05M.Kubantsev ITEP/NWU10 HYCAL Energy Resolution Energy resolution for the PWO crystal central part and lead glass periphery for tagged photons during calibration run PWO LG a = 0.023 b = 0.054 c =0.0a = 0.009 b = 0.025 c = 0.010

11. Calor-2006, June 05M.Kubantsev ITEP/NWU11 HYCAL Energy Resolution E γ =~5 GeV

12. Calor-2006, June 05M.Kubantsev ITEP/NWU12 HYCAL Position Resolution PWO: Dx =2.2 mm @ 1-3 GeV LG: Dx = 4 mm @ 1-3 GeV

13. Calor-2006, June 05M.Kubantsev ITEP/NWU13 HYCAL Light Monitoring Light monitoring system with blue LED: stability over period of 500 hours

14. Calor-2006, June 05M.Kubantsev ITEP/NWU14 HYCAL Performance for Physics Processes: π 0 production and decay to two photons at all angles (PWO and LG): constraint on mass of π 0 comparison of regions of the HYCAL: PWO, LG, PWO-LG border PWO Incident Tagged Photon Scattered Electron Scattered Photon Compton scattering at small angles mostly (only PWO): Pt = 0 constraint angular correlations as additional check of resolution Target: γe eγ PWO Target: π 0 γγ Incident Tagged Photon LG

15. Calor-2006, June 05M.Kubantsev ITEP/NWU15 HYCAL Resolution for Compton Events: after calibration after Pt = 0 correction only coordinate information Events/0.001 σ σ = 1.5 % σ = 1.1 % σ = 1.7 % Ratio of sum of electron and photon energies measured in the calorimeter and tagged γ energy at ~5.2 GeV

16. Calor-2006, June 05M.Kubantsev ITEP/NWU16 HYCAL π 0 Resolution: PWO after calibration Events/0.5 Mev/C2 σ = 2.3 MeV/ c 2 M γγ, GeV/ c 2 after correction on tagged photon energy: smearing due to coordinate resolution σ = 1.3 MeV/ c 2

17. Calor-2006, June 05M.Kubantsev ITEP/NWU17 HYCAL π 0 Resolution: PWO-LG Border π 0 mass resolution after calibration: one photon in PWO another at the border after correction on tagged photon energy: smearing due to coordinate resolution M γγ, GeV/ c 2 Events/0.5 Mev/C2 σ = 2.6 MeV/ c 2 σ = 1.4 MeV/ c 2

18. Calor-2006, June 05M.Kubantsev ITEP/NWU18 HYCAL π 0 Resolution: PWO + LG π 0 mass resolution after calibration: one photon in PWO another in LG σ = 4.5 MeV/ c 2 Events/0.5 Mev/C2 σ = 2.4 MeV/ c 2 after correction on tagged photon energy: smearing due to coordinate resolution M γγ, GeV/ c 2

19. Calor-2006, June 05M.Kubantsev ITEP/NWU19  o Angular Distribution (experiment, preliminary) Primakoff  0 12 C 208 Pb

20. Calor-2006, June 05M.Kubantsev ITEP/NWU20 Summary A high performance hybrid PbWO 4 calorimeter(~2000 channels) has been developed, constructed and run in PrimEx experiment at JLab. HYCAL took physics data in November 2004:  Energy and position calibration with tagged photons of 1 – 5.5 GeV  π 0 mass resolution  π 0 = 2.3 MeV (PWO), (with energy constraint on the tagger 1.3 MeV)  Rich high quality data sets have been collected to extract π 0 life time We expect first physics results this summer: http://www.jlab.org/primex/  This project is supported by the US NSF MRI grant (PHY-0079840)  This project is supported by the RFBR Grant 04-02-17466

21. Calor-2006, June 05M.Kubantsev ITEP/NWU21 Spare slides

22. Calor-2006, June 05M.Kubantsev ITEP/NWU22 PbWO 4 Detector Response vs. Dose Rate

23. Calor-2006, June 05M.Kubantsev ITEP/NWU23 Reconstruction of photon positions in the transition region between PWO crystal central part and lead glass periphery Center-of-Gravity Logarithmic Profile1 Profile2 Y beam coordinate (y = 300.88 mm) HYCAL Position Resolution

24. Calor-2006, June 05M.Kubantsev ITEP/NWU24 Coordinate of the cluster: X c = Σ(x i w i )/Σw i Center-of-Gravity: W i = E i Logarithmic: W i = 4.2 + ln(E i /E 9 ) HYCAL Position Resolution