SksMinus status Hyperball collaboration meeting 2009/3/11 K. Shirotori

 Reaction analysis : K1.8 + SksMinus   -ray detection : Hyperball-J ⇒ Reaction-  coincidence J-PARC E13 experiment Hypernuclear  -ray spectroscopy experiments on several light nuclei ( 4  He, 7  Li, 10  B, 11  B, 19  F) (K -,  - ) p K = 1.5 GeV/c

SksMinus setup SksMinus elements  Particle tracking : SDC1~4  Time-of-flight : STOF  Reaction ID : BAC, SAC (n=1.03)  Veto counters SMF :  - from K - →  - + SP0 :  - from K - →  - +  0  Target : Li 2 O, Teflon ((CF2) n ), Boron( 10,11 B) (~10 cm, ~15 g/cm 2 ) Liquid 4 He (25 cm, 3.13 g/cm 2 ) _ Requirements for  - of ~1.4 GeV/c Acceptance >100 msr, ~20 o scattering angles Momentum resolution < 3 MeV/c (FWHM) 1 m SksMinus

Contents Detector status –Drift chambers –Timing counters –Veto counters –Others SksMinus system status –SKS magnet problem –Detector placement Summary

Drift chambers

Drift chambers for SksMinus SDC3&4 : BD chamber ×2 –Large DC camber : 2 m×1 m (x,x,u,u,v,v) SDC2 : Old SKS chamber –Repair in Tohoku SDC1 : New construction –Not completely finish the design work

Drift chambers status BD chambers are almost ready. –~300  m (rms) position resolution –99% efficiency at counting rate of 100 kHz (w/ 90 Sr source) ⇒ To design and product frame Broken wires of SDC2 are finished to be repaired. –Signal check and TDC data taking –Frame design SDC1 is under construction. –How about design ? ⇒ Almost finished –Frame confliction to Hyperball-J frame

Timing counters

Timing counters for SksMinus STOF : Using SKS TOF scintillation counter –2 m×1 m TOF wall –Present 15 segments + new 17 segments –Bought by KEK fund BH2 : Time zero counter –~1 MHz counting rate ⇒ 1 segment counter ?

Timing counters status STOF –New segments : Need 34 PMTs (H1949) –PMT check Finished : 71 PMTs –Light guide is ordered. ⇒ Counter assembly and frame design BH2 –Scintillator : Available one –PMTs : Booster PMT (old SKS BH2 PMT)

Veto counters

Veto counters for SksMinus SP0 : K - →  -  0 event veto –T. Otani working SAC & BAC : (K -,  - ) trigger –Aerogel cherenkov counter –M. Sato working SMF : K - →  - event veto –Counter assembly –Iron shield

SAC and BAC Aerogel cherenkov counters for the (K -,  - ) reaction ID –Radiator (Aerogel) are bought by Kyoto Univ. fund. –Fine mesh PMTs are bought by Osaka RCNP fund. BAC1&2 : Beam PID counter –160×57×4 mm 3 radiator –2 fine mesh PMTs SAC1 :  - detection counter –334×80×4 mm 3 radiator –5 fine mesh PMTs SAC2 : Combinational beam veto Aerogel counter –K - beam veto by SFV –Forward scattered  - saved by Aerogel cherenkov counter We can assemble all detectors after PMTs are arrived. ⇒ All detectors will be tested in LNS experiment

SP0 status Counter production –Plastic scintillation counter : E559 Range counter –4 mm thickness lead plate : Arrived –Frame design final check Proto-type ⇒ production Result of test experiment –LNS experiment : Response to electromagnetic shower compared with simulation ⇒ Detection efficiency : 78.6 ± 1.5%(sys.) –CYRIC experiment : Neutron detection efficiency ⇒ ~0.3 % of  non-mesonic weak decay events detected Enough performance for E13 experiment

SMF status Counter production –Plastic scintillation counter : BT(2m ⇒ 1.2m cutting) –Light guide for 2 segments readout –Frame design Iron shield –Barrow from KEK (Request for support) ⇒ Need to design iron shield frame (after finished BD and STOF frame) 100 cm×50 cm×50 cm 100 cm×50 cm×20 cm Block-A Block-B

Others

Other components status Targets – 4 He target was ordered. : ~\4,000,000 –Li 2 O : Company was found. – 10 B and 11 B : modified old target used in BNL-E930 for the beam profile at K1.8 – 19 F : Teflon ((CF 2 ) n ) or BeF 2 –CH 2 : SksMinus calibration run ( 12  C and p(K -,  - )  + ) + Design of target stage with BAC and SAC He target assembly and test He target cell production

Summary ○ SDC3&4 : Repair finished ⇒ Frame ○ SDC2 : Repair almost finished ⇒ Frame × SDC1 : Design ○ STOF : Design and construction (by KEK ?) ○ BH2 : Construction (scintillator + booster PMT) ○ SAC&BAC : Construction ○ SP0 : Design finalize ⇒ construction × SMF : Iron shield borrow, frame, scintillation counter cutting △ Targets : Helium target assembly and test

To do SDC3&4 : Frame design SDC2 : Test ⇒ Frame design SDC1 : Design and test STOF : Frame design and counter assembling BH2 : To find scintillator + booster PMT SAC&BAC : Preparation for the LNS test experiment SP0 : Design finalize ⇒ Proto-type ⇒ construction SMF : Scintillation counter cutting, Iron shield frame design ⇒ After finishing BD and STOF frame design Targets : Helium target assembly and test Target stage : W/ SAC and BAC design Rotation arm for SksMinus position

SksMinus system status

SKS magnet problem SKS magnet coil broken ! One of the coil segment was broken and removed. ⇒ Coil turn became 5/6. Effects Maximum magnetic field strength : 2.7 T ⇒ 2.5 T Change of the shape of magnetic field (Cannot be measured) What did we do ? Change the SksMinus geometry –Incident beam angel –Target position and around target Magnetic field map : Calculated map is enough for E13 experiment. Acceptance : 118 msr ⇒ 115 msr Momentum resolution : 2.1 MeV/c ⇒ 2.4 MeV/c SksMinus system is almost OK. The change of magnetic field shape is still a significant problem.

Change of the rotation angle Old : -27° ⇒ +17° New : -27° ⇒ +12° Just only changing the rotation angle from SksZero configuration to SksMinus configuration SKS moving ー Old SksMinus ー New SksMinus

Acceptance : latest one 118 ms ⇔ 115 msr ○ : 395A before × : 395A after □ : New geom

Momentum resolution ○ : 395A before × : New geom 2.1 MeV/c (2.7 T) ⇒ 2.4 MeV/c (2.5 T)

SKS magnet and detector position SKS magnet position : FF mm ⇒ Enough space for Hyperball-J (Not determined the Q-magnet design) Upstream detectors Need minor change of positions with the realistic detector size To design suitable frame Downstream detectors Frame design in progress Iron shield for SMF