Setup for hypernuclear gamma-ray spectroscopy at J-PARC K.Shirotori Tohoku Univ. Japan for the Hyperball-J collaboration J-PARC E13 hypernuclear  -ray spectroscopy experiment Missing mass analysis : Magnetic spectrometer (identification of hypernuclear bound states ) Beam K - Scattered  -  -ray measurement by Ge detector array  rays from hypernuclei : Particle-  coincidence (  +, K +  KEK, (K -,  -  BNL Magnetic spectrometers + Hyperball Upgrade  Hyperball-J Missing mass analysis  -ray measurement (K -,  -  ) J-PARC Optimized magnetic spectrometer + Hyperball-J SksMinusHyperball-J To analyze 1.4 GeV/c (1.1~1.8 GeV/c) scattered  -  Large acceptance ~100 msr,  20 degree → Efficient tagging of hypernuclei and angular selectivity Good momentum resolution 2  4 MeV/c (FWHM)  Good momentum resolution 2  4 MeV/c (FWHM) → Identification of bound states of hypernuclei (mass resolution ~5 MeV (FWHM) ) (mass resolution ~5 MeV (FWHM) ) Modified SKS (Superconducting Kaon Spectrometer) (K -,  - ) p K = 1.5 GeV/c SDC1~4 : Momentum analysis STOF : Time-of-flight SAC :  - identification SFV : K - beam veto Beam decay background Veto SMF :  - from K - →  - + SMF :  - from K - →  - + SP0 :  - from K - →  - +  0 _ Target ~20 g/cm 2 1 m 2.2T Previous condition SksMinus Beam K - decay products make serious background ⇒ Same kinematical region to (K -,  - ) reaction K - →  -  -  + (5.58%) K - →e -  0 (4.87%) K - →  -  0 (3.27%) K - →  -  0  0 (1.73%) Contribution of three-body decay is relatively small. Simulated performance Acceptance, Momentum resolution and Particle ID  Acceptance at 1.4 GeV/c, ~130 msr ~130 msr  Enough angular acceptance, ~20 degree ~20 degree  Momentum resolution at 1.4 GeV/c ~2.1 MeV/c (FWHM) ~2.1 MeV/c (FWHM) Rejection of K - beam through background SAC ~98% + SFV Reaction ID by BAC and SAC trigger  STOF : Time resolution ~150 ps (rms)  Large drift chambers  Optimized incident beam angle Beam decay background veto counters K - →  - (63.4%) Muon Filter _  - (passing through)  - (absorbed in the iron) Sufficient performance to reduce the trigger rate and background K - →  -  0 (21.1%) PiZero Veto _ _ Wall configuration and simulated efficiency  Mechanical cooling by Pulse tube  PWO background suppression  Waveform readout for pulse shape analysis ~6% photo peak 1 MeV (half picture) Mechanical cooler ⇒ Suppression of the neutron damage effect with Ge crystal below 85 K (LN2 cooling ~90 K) ~2 keV (FWHM) energy resolution and cooling power of less than 85 K are achieved. Ge Cooler Pulse Tube refrigerator PWO CsI PMT  Doped PWO crystal  Cooling of PWO below 0 ℃ W-type U-type L-type  -type The performance of background suppression of the PWO counter by cooling below 0 ℃ is the same as of BGO counter. But, small light yields (PWO/BGO = 1 /10) The PWO crystal has very first decay constant ~6 ns. (~300 ns for BGO) To improve energy resolution and recover rejected events at high counting rates  Baseline shift restoration  Pileup signals separation Pulse height ADC ⇒ FADC (wave form digitization) (after shaping) In the test experiment, the positron beam is irradiated to Ge detector to make frequent baseline shits by reset signal. ⇒ The restoration of the baseline shits 3.7 keV ⇒ 3.1 keV (FWHM)  2.6 keV w/o beam No baseline restoration Baseline restoration New Ge detector  Cooling power Ge crystal temperature less than 85K when biased  Low mechanical vibration Minimization of microphonics noise  Compact size Realization of the planar arrangement of Ge detectors Hyperball-J ∞-type element PWO counter and Waveform readout for high counting rates Summary  J-PARC E13 experiment by the (K -,  - ) p K =1.5 GeV/c Optimal magnetic spectrometerOptimal magnetic spectrometer New Hyperball system for the high counting rateNew Hyperball system for the high counting rate  Magnetic spectrometer, SksMinus and newly constructed array, Hyperball-J SksMinus performance : More than 100 msr acceptance, 20 degree coverage, ~2 MeV/c momentum resolution Hyperball-J : ~6 % efficiency, Mechanical cooling system, PWO counter, Waveform readout The experiment will be performed at PWO counter types 60 Co 1.3 MeV  -ray spectrum Several light hypernuclear  -ray spectroscopy experiments are planned. ( 4  He, 7  Li, 10  B, 11  B, 19  F ) SKS for 1.05 GeV/c (  +, K + ) reaction (p K = 0.72 GeV/c) 2.7T Beam K BACSAC Target 20cm  Decay Overlap 86% of   events detected 14 % non-rejected (stopped in the iron) by offline analysis Totally > 99.9 %  Over kill for true π ~2.5% 80% of  -  0 events detected 10 sets of 3 mm lead plate and 8 mm scintillation counter layer at 1.5 GeV/c beam. SAC Beam veto (SFV) BAC Muon Filter Neutron damage High counting rate 10 cm 13 cm Ge energy spectrum 1 MeV  ray J-PARC