1. SksMinus status SKS meeting 2007/5/10 白鳥昂太郎

2. SksMinus setup SksMinus  STOF : Time-of-flight  SAC & BAC: K - beam veto and  - ID (n=1.03)  (SFV : K - beam veto)  SDC1~4 : Beam position measurement Background Veto  SMF :  - from K - →  - +  SP0 :  - from K - →  - +  0 _ Trigger = K in ×PI out  K in = BH1×BH2×BAC  PI out = STOF×SAC×SFV×SMF×SP0 Target ~20 g/cm 2

3. SksMinus elements  Drift chamber : SDC1,2 & SDC3,4  Timing counter: STOF, BH2  Aerogel Cherenkov counters : BAC, SAC (K - beam veto counter (timing counter) SFV)  Beam decay veto counters : SMF, SP0  4 He target

4. SDC3&4  6 layer (x, x’, u, u’, v,v’ ( ±30°) ) (107×6 ch)  Size: 2140 mm×1140 mm (20 mm wire pitch) 400  m (rms) position resolution is assumed.  Highest counting rate @1.5 GeV/c (500 k/spill) 70 k/spill ⇒ 100 kHz (0.7 sec spill) 200 k/spill ⇒ 300 kHz (0.7 sec spill) @ 1.8 GeV/c

5. SDC1&2 SDC1  6 layer (x, x’, u, u’, v,v’ ( ±15°) ) (128×6 ch)  Size: 384 mm×200 mm (3 mm wire pitch)  Target distance : 350 mm SDC2  4 layer (x, x’, u, u’ ( ±15°) ) (112×4 ch ?)  Size: 560 mm×150 mm (5 mm wire pitch)  Target distance : 575 mm 400  m (rms) position resolution is assumed.  Who makes SDC1 (SksPlus SDC2) ? Size → Hyperball-J frame  Where is old SDC2 ? The area size of DC in clean room is 400 mm. Old SDC is 560 mm in Hasegawa D thesis.

6. STOF design  STOF is made from BT used in E930 experiment. All counters of the present TOF is planned to be replaced.  BT 1 segment: 85×2000×50 (x,y,z) → Half size 85×1000×50 (x,y,z) ∴ 28 segment = 2380×1000×50 (x,y,z) BT: 40 segments → 26 segments can be used for other counters.  150 ps(rms) time resolution is necessary.

7. BH2  Beam profile  x =20 mm,  y = 3 mm ⇒ 160 mm×25 mm (±4  )  It is possible for 1 segmented counter in E13 experiment (700 k/spill). Front image With PMT ⇒ ~400mm Target BH2 BAC1 BAC2 SAC 100~300mm200mm 250~350mm The position of BH2 is outside of the Hyperball-J frame, because of the conflict. For E13 experiment we needs an other additional counter just before the target to reduce the trigger rate. HBJ frame ~ 300mm Beam

8. BAC & SAC  BAC: 160×30×75 (x,y,z) ×2 layers  SAC: 300×90×75 (x,y,z) 1 or 2 layers (360×110×75 (x,y,z) ) Many fine mesh PMTs are needed. ⇔ PMTs conflicts Hyperball-J. Signal readout by fiber inside of AC

9. SMF & SP0  SMF: Iron blocks and scintillation counters Any counter can be used. (BT ?)  SP0 : Range counter (E559) Range counter with lead absorber shows good performance by rough simulation.

10. 4 He target  The similar target used in K5 is planned.  Target size is as large as possible. (Target length is less than 300 mm)  Determination of size of detectors around the target and Hyperball-J is needed.

11. Time table  SDC repair 、 test  STOF test  SP0,SAC,BAC design