SKS Minus Detectors in detail Tohoku Univ. K.Shirotori

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

Proposed “DAY-1” experiment E13  Several light hypernulcear experiments are submitted ( 4 Λ He, 7 Λ Li, 10 Λ B, 11 Λ B, 19 Λ F).  (K -, π - γ) at p K = 1.5 GeV/c (500k/spill) (Out going π - ～ 1.4 GeV/c)  Experimental setup is determined by these requirements.

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 )

The K1.8 Beam line and SKS Beam spectrometers ・ BH1,2 : Time-of-flight ・ BAC : π - veto (n=1.03) SKS ・ SAC : K - veto (n=1.03) ・ SFV : K - beam veto ・ STOF : Time-of-flight Target : ～ 20 g/cm 2 DC : Beam position measurement Background Veto ・ SMF : μ - from K - →μ - +ν ・ SP0 : π - from K - →π - +π 0 SMF SP0 Hyperball-J : γray Beam spectrometer SKS 2.7T

K1.8 Beam Line -side view- BDC1,2BDC3,4SDC1,2BDC3,4 BH1BH2SFVSMFTOF BACSAC SP0 Ge+PW O Beam line part SKS part Hyperball-J

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 - +π 0 : SP0 2m

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 - +π 0 : SP0

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 ～ m

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

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

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

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

Background events  K - →μ - ν (63.4%) ⇒ Muon Filter  K - →π - π 0 (21.1%) ⇒ PiZero Veto Beam K - decay products make serious background K - →π - π - π + (5.58%) K - →e - π 0 ν (4.87%) K - →μ - π 0 ν (3.27%) K - →π - π 0 π 0 (1.73%) Contribution is relatively small ～ 150 trigger Fake trigger ～ 1700/spill True event trigger ～ 700/spill Beam K BACSAC Target 20cm μ νDecay

3-body Decay K - →π - π - π + (5.58%) K - →e - π 0 ν (4.87%) K - →μ - π 0 ν (3.27%) K - →π - π 0 π 0 (1.73%)

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

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

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

PiZero Veto  70% of π 0 can be detected by 2 set of 2[cm] lead plate and scintillation counter layer. (75% of γ from π 0 hit the SP0) Simulation in progress After Before

PiZero Veto  70% of π 0 can be detected by 2 set of 2[cm] lead plate and scintillation counter layer. (75% of γ from π 0 hit the SP0) Simulation in progress After Before Beam K

Trigger rate  (K -,π - ) Reaction rate ～ 700/spill  K - →μ - ν ～ 1320/spill  K - →π - π 0 ～ 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.  (K -,π - ) Reaction rate ～ 700/spill  K - →μ - ν ～ 140/spill  K - →π - π 0 ～ 120/spill  K - Beam ～ 10/spill  3-body decay ～ 150/spill ～ 1120/spill w/ Veto counters ～ 500/spill w/ Ge trigger (K -, π - γ) at p K = 1.5 GeV/c (500k/spill) Comparable to the present trigger rate

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.

Back up

Beam Momentum    n  

Level scheme of 7 Λ Li

Calculated cross section for 7 Λ Li

Iron thickness

Muon Filter

Percentage of decay in target 20cm