1. Development of Forward Aerogel Cherenkov Detector for the H-dibaryon search experiment (E42) at J-PARC Japan-Korea PHENIX Collaboration Meeting Minho Kim Korea Univ.

2. Signal : p(K -, K + )Ξ - Background: p(K -, π + )Σ - H-Dibaryon Search Experiment, E42 KUNPL 2 KURAMA magnet ToF wall TPC Helmholtz magnet “AC detector” 1.7 GeV/c K - beam Drift chamber “H-dibaryon” Six quarks J π = 0 +

3. Forward Aerogel Cherenkov Detector 3 KUNPL π, K Fine-mesh PMT Strong to B field Parabolic reflector Light box Thin Al plate Aerogel n=1.04, 110×110×20 mm 3 Will be installed at the exit of Helmholtz magnet. Contents 1. Aerogel 2. Fine-mesh PMT 3. SPring-8 beam test

4. FAC Aerogel 4 Refractive index should be smaller than 1.04132. KUNPL Pion emits Cherenkov light. Kaon emits Cherenkov light. p min FAC can reject is about 0.48 GeV/c.

5. FAC PMT, fine-mesh PMT 5 KUNPL mean Npe = 1 Let’s assume one photoelectron  mean ADC, +Q. Bad resolution for photon counting. Mesh type dynode  Not Gaussian shaped amplification.

6. FAC Test Experiment at SPring-8 6 KUNPL 1. Parabola FAC 2. Teflon FAC 3. Winston cone FAC Installed at the very end of LEPS spectrometer.

7. FAC Setup KUNPL 7 PMT2 PMT16 Drawn by S.H. Kim W.S. Jung PMT1 PMT17 PMT1 PMT2 6/9~7/4 run 7/15~ 7/24 run PMT17 PMT16 Same |x|, |y| position. Similar pion momentum range with similar statistics.

8. FAC Installation KUNPL 8 480<x<700 mm 115<y<225 mm 480<x<700 mm -225<y<-115 mm 1 2 1 2 Turned off

9. Particles which passed through FAC 9 KUNPL Momentum (GeV/c) Mass*charge(GeV/c 2 ) Below 3.0 GeV/c for protons. Above 0.5 GeV/c for pions. Mass*charnge (GeV/c 2 ) Counts π+π+ π-π- P K+K+ P K+K+ π+π+ Particle identification with ± 2σ tolerance. Kaon study  Pion study Wide range of momenta pions.

10. Pion Efficiency KUNPL Parabola FAC ADC threshold: Proton misidentification is less than 5 %. Pion efficiency = (Events which pion leaves ADC bigger than threshold) / (All pion events in specific momentum range) 10 Considered as pions. Considered as kaons.

11. Pion Efficiency 11 KUNPL Parabola FAC shows better performance. Maximum 0.980 efficiency on average with neutron bar cut condition(>0.7 GeV/c). Teflon FAC Parabola FAC Pion momentum (GeV/c) Pion efficiency Pion momentum (GeV/c) Pion efficiency Winston FAC Parabola FAC Without nbar cut condition With nbar cut condition

12. Position Dependence of Efficiency 12 KUNPL Exterior Cherenkov light goes towards surrounding plane surface first. Perfect fit (to aerogel area) light box is not good. Parabola FAC Central Inclusive Boundary Maximum 0.992 on average. Pion efficiency (GeV/c)

13. Npe Study 13 KUNPL Total (>0.7 GeV/c)0.7~0.8 GeV/c0.8~0.9 GeV/c 0.9~1.0 GeV/c1.0~1.1 GeV/c1.1~1.2 GeV/c 1.2~1.3 GeV/c 1.3~1.4 GeV/c1.4~1.5 GeV/c Npe Counts

14. Npe Study 14 KUNPL sin 2 θ1/β 2 mean Npe Since Cherenkov angle is smaller than 15 °, cosθ ≈ 1.

15. Summary & Plan 15 KUNPL We tested three types of FAC and studied corresponding pion efficiency. We’re checking pion efficiency and Npe again. From middle of November, we will start the test of full size FAC mockup.