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New Detector Design for Combined Measurements of Omega Meson

October 17, 2009. KE0002. New Detector Design for Combined Measurements of Omega Meson. Kazuki Utsunomiya Kyoichiro Ozawa, Yosuke Watanabe, Shinichi Masumoto, Yusuke Komatsu, Tamotsu Sato, - The University of Tokyo Satoshi Yokkaichi, Kazuya Aoki, - RIKEN

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New Detector Design for Combined Measurements of Omega Meson

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  1. October 17, 2009 KE0002 New Detector Design for Combined Measurements of Omega Meson Kazuki Utsunomiya Kyoichiro Ozawa, Yosuke Watanabe, Shinichi Masumoto, Yusuke Komatsu, Tamotsu Sato, - The University of Tokyo Satoshi Yokkaichi, Kazuya Aoki, - RIKEN Tomoya Tsuji, - CNS, The University of Tokyo

  2. Contents

  3. Combined Measurements of w “Origin of Hadron mass” w mesons are almost stopped. • Meson mass modification in nucleus • Nuclear bound state Hadron Hall @ J-PARC 1.8 GeV/c momentum Neutron Counter - Missing mass of w. - w initial condition is restricted. Gamma-ray Detector - Invariant mass of w.

  4. Main Two Detectors 1.8GeV Neutrons • Gamma-ray Detector CsI(Tl) calorimerter • Neutron Counter TOF type Scintillator 7m Flight path Target Charged Particles 60cm 100cm 60cm 21cm 140cm

  5. Neutron Counter Double-end readout. 6 scintillators – 4 layers. ~5deg. neutron acceptance. • 48 PMTs • Hamamatsu H2431-50 • 24 scintillators • Saint-Gobain Crystals BC408 (600 x 100 x 30mm) • 4 iron plates Stopped ~1.8GeV/c 7m Time-Of-Flight (TOF) • Required performance • Time resolution : less or equal 80 psec • Neutron Efficiency : 30%

  6. Expected performance Missing mass spectrum of w 703.24 Δ1.9% Mass of w 782.65 • Time resolution : 55 psec • Beam test using electron beam at Fuji test beam line (KEK) and at Kakuriken (Tohoku Univ.). • Neutron efficiency : 25.6% (Scintillatorand 1cm thick iron plates, 4 layers) • Monte Carlo simulation using the FLUKA package. MeV/c2 Neutron detection efficiency Missing mass spectrum can be measured.

  7. Gamma-ray Detector • 768 CsI(Tl) crystals • PIN photodiode readout • 12 muon holes for T-violation experiment [NIM A 440 (2000) 151] The detector was used at KEK E246 experiment. Under upgrading for T-violation experiment(E06) at J-PARC. This detector will be reused and be customized for our combined measurements.

  8. Simulation for w mass reconstruction How does the invariant mass of w meson look like? • Make a simulation code to reproduce an existing experiment data. [NIM A 440 (2000) 151] [NIM A 494 (2002) 318] • Run a simulation for w meson mass reconstruction. Our experiment Existing experiment • Energy resolution • Angular resolution • Shower leak Evaluate by Simulation Mass of p0

  9. Simulation check by existing data Existing experiment data 123.4MeV/c2 8.0% 235.7MeV 5.2% Simulation for kaon 234.7MeV 4.9% 127.2MeV/c2 6.9% Opening angle Energy of p0 Invariant mass of p0 Reproducing of an existing experiment data is very well.

  10. w mass reconstruction Energy of g Fiducial cut All event Mass of p0 Tail cut MeV/c2 A large tail is caused by muon hole effects. With cut Away from hole MeV/c2

  11. Combined measurements of w Missing mass method Invariant mass method 9% Shifted mass event Mass of w 782.65 MeV/c2 MeV/c2 The mass modification and the nuclear bound state can be measured with these two detectors. MeV/c2

  12. Summary • The missing mass spectrum can be measured by neutron counter. • The invariant mass spectrum can be measured by gamma-ray detector without w mass tail. • Using these two detectors, the w mass modification in nucleus and the nuclear bound state can be measured. • Out look • Our proposal will be discussed at J-PARC 9th PAC meeting, January 15 – 17, 2010. • Construct the spectrometer!! Shall we collaborate?

  13. BACK UP

  14. Comparison betweensimulation and existing experiment Existing experiment Left: All event. Right: Energy cut for small opening angle. • Opening angle between two gamma-rays Simulation 67.7 deg. Reproducing opening angle is very well.

  15. Comparison betweensimulation and existing experiment Existing experiment • Energy of p0 235.7MeV 5.2% Left: All event. Right: Away from muon holes. 242.5MeV 4.1% Simulation 234.7MeV 4.9% 242.2MeV 4.1% Reproducing energy of p0 is very well.

  16. Comparison betweensimulation and existing experiment Existing experiment • Invariant mass of p0 123.4MeV/c2 8.0% 128.0MeV/c2 7.0% Left: All event. Right: Away from muon holes. Simulation 127.2MeV/c2 6.9% 133.0MeV/c2 5.6% Reproducing mass of p0 is very well.

  17. Fiducial cut and pion mass tail cut Pion mass tail cut Fiducial cut

  18. With or without muon hole Muon hole No muon hole Muon hole effect

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