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SKS Minus Detectors at Tohoku University: Experiment Details and Setup Requirements

Explore the detailed setup and operation of SKS Minus Detectors at Tohoku University, essential for hypernuclear experiments like those proposed in the E13 "DAY-1" experiment. Learn about the detectors, veto counters, gamma-ray spectroscopy requirements, beamline setup, and more. The setup includes components like Time-of-Flight, Beam Veto, Drift Chamber, Hyperball-J, and Background Veto systems to achieve accurate measurements and high resolution. Crucial information on how these detectors function, their configuration, and the analysis of hypernuclear states is provided. Discover the complexities involved in ensuring low background experimental conditions and high momentum resolutions required for the experiments.

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SKS Minus Detectors at Tohoku University: Experiment Details and Setup Requirements

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  1. SKS Minus Detectors in detail Tohoku Univ. K.Shirotori

  2. Outline • Requirement on setup • Setup, SKS & Hyperball-J • Detectors in detail, SKS & Veto counters • Summary

  3. Proposed “DAY-1” experimentE13 • Several light hypernulcear experiments are submitted (4ΛHe, 7ΛLi, 10ΛB, 11ΛB, 19ΛF). • (K-, π- γ) at pK = 1.5 GeV/c (500k/spill) (Out going π-～1.4 GeV/c) • Experimental setup is determined by these requirements.

  4. Requirement on hypernuclear gamma-ray spectroscopy • To analyze 1.4GeV/c scattered π- by existent spectrometer system. • Large acceptance ～100[msr]. →Enough hypernuclear production yield. • Good momentum resolution 2～4[MeV/c]. →To distinguish excited states of hypernuclear. • (Low background experimental condition) SKS (Superconducting Kaon Spectrometer )

  5. The K1.8 Beam line and SKS Beam spectrometers ・BH1,2 : Time-of-flight ・BAC : π- veto (n=1.03) SMF SKS SKS 2.7T ・SAC : K- veto (n=1.03) ・SFV : K- beam veto ・STOF : Time-of-flight SP0 DC : Beam position measurement Background Veto Target : ～20 g/cm2 ・SMF : μ- from K-→μ-+ν ・SP0 : π- from K-→π-+π0 Beam spectrometer Hyperball-J : γray

  6. K1.8 Beam Line -side view- BDC1,2 BDC3,4 SDC1,2 BDC3,4 BH1 BH2 SFV TOF SMF BAC SAC SP0 SKS part Beam line part Ge+PWO Hyperball-J

  7. SKS Minus • Time-of-flight : STOF • Position measurement : SDC1～4 • Beam veto : SAC • Beam veto : SFV • Veto counter, μ- from K-→μ-+ν : SMF • Veto counter, π- from K-→π-+π0 : SP0 2m

  8. SKS Minus • Time-of-flight : STOF • Position measurement : SDC1～4 • Beam veto : SAC • Beam veto : SFV • Veto counter, μ- from K-→μ-+ν : SMF • Veto counter, π- from K-→π-+π0 : SP0

  9. SKS Minus –Drift chamber- DC active area (num of layer) • SDC1 (4): 350x150[mm] • SDC2 (6): 600x200[mm] →Covering full range, 0～25° →Newly construction (present SDC1 240x150, SDC2 400x150) • SDC3 (6): 2140x1140[mm] • SDC4 (6): 2140x1140[mm] →Shipped form BNL D6 line and added two layers • Resolution ～ 400[μm] • Counting rate /wire < 100kHz • Channel ～3000 2m

  10. SKS Acceptance & Momentum resolution • Acceptance ～120[msr] 100[msr] for present SKS • Momentum resolution 2.1[MeV/c](bending angle ～60° w/ multiple scattering) 0.8[MeV/c] for present SKS (ΔP/P=6.3x10-4) Simulation is checked by present SKS data

  11. SKS Minus –TOF & Beam veto- • TOF : 2240x1000[mm] →32 segments 70x1000x20[mm], 17 new scintillation counters (present 15) →ΔT=200[ps] • SFV : 150x25[mm] →Air light guide • SAC : 200x30[mm] →n=1.03 • SBS : 150x25x50[mm] →Pb, W (300kHz→60kHz/wire) 2m

  12. Time resolution • Flight time ～16[ns] • Path length ～4.63[m] • Momentum Pk=1.5 GeV/c (ΔP/P=1.4x10-4) Pπ form (K, π) reaction (ΔP/P=6.3x10-4) • Present TOF → 300[ps] w/o PHC • Present BH1,2 → 200[ps] w/ PHC

  13. Beam Veto • SAC efficiency ～99% →5k trigger /spill @ 500k/spill SFV →～10 trigger Reduction of acceptance 7.5% • Beam size σx=19.8[mm] σy=3.2[mm] (u=0.02, v=0.002) • SBS K- beam directly hit SDC3,4. ↓ Scattering beam particles by some material (Pb, W) 300kHz→60kHz@ 20mm cell SBS

  14. Target 20cm Background events BAC SAC μ Beam K Decay ν Beam K- decay products make serious background • K-→μ-ν (63.4%) ⇒Muon Filter • K-→π-π0 (21.1%) ⇒PiZero Veto Fake trigger ～1700/spill True event trigger ～700/spill K-→π-π-π+ (5.58%) K-→e-π0ν (4.87%) K-→μ-π0ν (3.27%) K-→π-π0π0 (1.73%) Contribution is relatively small ～150 trigger

  15. 3-body Decay K-→π-π-π+ (5.58%) K-→e-π0ν (4.87%) K-→μ-π0ν (3.27%) K-→π-π0π0 (1.73%)

  16. SKS Minus –Background veto- • SMF : 2200x1400[mm] →11 segments 200x1400x20[mm], Any scintillation counters are OK • Iron : 500x500x500[mm]x12 • +additional parts • SP0 : 1400x1400[mm] →many conuters ～60 • Lead plate : 1400x1400x20(15)[mm]x2～3 2m

  17. Muon Filter Thick Material (ex. Iron) μ- Pass through π- Stopped by hadronic interaction Scintillation counter Scintillation counter Only μ-can be detected.

  18. Muon Filter Before • 89% of μ can be detected in the trigger • In the offline analysis ～100% • Over kill for true π ～1.7% After

  19. PiZero Veto Before • 70% of π0 can be detected by 2 set of 2[cm] lead plate and scintillation counter layer. (75% of γ from π0 hit the SP0) After Simulation in progress

  20. PiZero Veto Beam K Before • 70% of π0 can be detected by 2 set of 2[cm] lead plate and scintillation counter layer. (75% of γ from π0 hit the SP0) After Simulation in progress

  21. Trigger rate (K-, π- γ) at pK = 1.5 GeV/c (500k/spill) • (K-,π-) Reaction rate ～700/spill • K-→μ-ν ～1320/spill • K-→π-π0～390/spill • K- Beam ～10/spill • 3-body decay ～150/spill ～2570/spill w/o Veto counters True trigger ～350/spill w/ Ge trigger and fake trigger greatly decreased. ～1120/spill w/ Veto counters • (K-,π-) Reaction rate ～700/spill • K-→μ-ν ～140/spill • K-→π-π0～120/spill • K- Beam ～10/spill • 3-body decay ～150/spill ～500/spill w/ Ge trigger Comparable to the present trigger rate

  22. Summary • Hypernuclear gamma-ray spectroscopy is feasible with SKS. • Simulations in progress show a good veto counter efficiency. • Estimation of background from heavy counter materials is necessary.

  23. Back up

  24. Beam Momentum K- + n-> L + p-

  25. Level scheme of 7ΛLi

  26. Calculated cross section for 7ΛLi

  27. Iron thickness

  28. Muon Filter

  29. Percentage of decay in target 20cm

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