p n  Systematic Study of Double Strangeness System by an Emulsion-Counter Hybrid Method Experimental motivation. 0. Previous experiment E373 (KEK-PS) [ 97% scanned ]. Ⅰ. Making a S=-2 nuclear chart. Ⅱ. Study of H-resonance or dibaryon state. Ⅲ. First measurement of X-ray from  -atom Outline of E964 R and Development since 2001 Ⅰ. Double-sided Si Strip Detector (DSSD). Ⅱ. Nuclear Emulsion. Ⅲ. Hyperball 2 Summary Conditions Sep.09,2004 AGS-PAC 1 / 20 Phys. Dept., Gifu Univ. K.Nakazawa Current status of AGS-E964 Dept. of Phys., Tohoku Univ. H.Tamura

p n  2001 Double-  hypernuclei from E373(KEK-PS) “ the most significant result of the past 5 years in hypernuclear physics. ” Final Report of the 2004 KEK PS External Review Committee (August 30, 2004),p Sep.09,2004 AGS-PAC 2 / 20

p n  Comparison with past results  interaction energy 11 22 or Sep.09,2004 AGS-PAC 3 / 20  interaction is weakly attractive. Our knowledge for  int. until now. E373

p n   B  & nuclear medium effect To know  int. independent on the nuclear medium effect, we need to measure A-dependence of  B . B  :  binding energy in nucleus S=-2 nuclear system     ‘H’  B  depends on A  B  may NOT depend on A Theoretical prediction Sep.09,2004 AGS-PAC 4 / 20

p n  Candidate events of double-hypernucleus from E373 preliminary rd double-  hypernucleus Nuclear species of the double-  can be, or.   He   He   Be Analysis in progress Sep.09,2004 AGS-PAC 5 / 20

p n  Nuclear Chart with Strangeness Experimental motivation Ⅰ Sep.09,2004 AGS-PAC 6 / 20 Strange matter Our goal is making a S=-2 nuclear chart, by observing so many nuclei with S=-2 as possible.

p n  H-dibaryon resonance (?) near the  threshold KEK-PS E522 Experimental motivation Ⅱ What is the ground state of S=-2 nucleus? Recent result 2. A-dependence of  B  3. Decay branching ratio [S=-2] =>   p,  n Sep.09,2004 AGS-PAC 7 / 20 M(  ) thres. 1. Confirm this enhancement by several times higher statistics.  or H-dibarion state in nucleus? |H>  √ a  √ b  N> - √ c |  mixing?   ‘H’‘H’ E373 data : Br(  =>   p) < 12%, by 1/4 data and assumption P (   stop =>  Z)~20% result of KEK-E176 E964 can achieve Br(  =>   p) < 0.3% Br(  =>  n) < 3 %

p n  The first measurement of X-ray of  -atom  -nucleus potential can be seen. Sep.09,2004 AGS-PAC 8 / 20 Experimental motivation Ⅲ H.Tamura will introduce this with the development of Hyperball 2, later.

p n  Nuclear Physics with double strangeness (S= - 2) KEK-E373 => AGS-E964 Sep.09,2004 AGS-PAC 9 / 20 6 countries 16 institutes 34 staffs + Graduate stu.

p n  Outline of E964R # Beam : K - (1.7GeV/c), 2 x 10 5 => 4 x 10 5 K - /spill with K - /  - >9 at D6-line # Detectors : Nuclear Emulsion, Double-sided Si strip Detector ( DSSD), Ge-Detector ( Hyperball ), KURAMA magnet carried from Japan # Time requested : 300 =>150 hours for detector tune 1100 =>600 hours for beam exposure # Trigger : (K-, K+) => 10 4  - stopping events (10 times higher stat. than E373) We request Beam time in FY2006 Sep.09,2004 AGS-PAC 10 / 20

p n  Experimental setup of E964 Sep.09,2004 AGS-PAC 11 / 20

p n  Development #1 Double-sided Si Strip Detector (DSSD) 1st Surface 2nd Surface ・ Two sets in the 4mm gap between the Target & Emulsion. ・ DSSDs have already been ordered to HAMAMATSU Photo Co.Ltd. Precise tracking of   hyperons for the top emulsion plate. => Reduction of background tracks, which are picked up in the plate. => Speeding up of emulsion scanning. ・ Effective area : 30x60mm 2 / Thickness : 0.3mm / pitch : 50  m Sep.09,2004 AGS-PAC 12 / 20

p n  Development #2 Automatic Scanning Current system Surface & Grid : 22 sec. Track_scan : 15 sec. Images are shown: 1. Surface detection => Grid measurement for position calib. 2. Track scanning Developing system Surface & Grid : 9 sec. Track_Scan : 6 sec. Sep.09,2004 AGS-PAC 13 / 20 x3 faster

p n  Development #3 Production method of emulsion Production method of Emulsion gel will be changed. For E964, amount of emulsion gel => 2.4 tons Fuji-film needs one year or more by conventional way. Emulsion cost will be saved 50% Conventional way by hand Using the production lines for commercial films Sep.09,2004 AGS-PAC 14 / 20 Stopping power and physical characteristic has been tested, and the result showed no problem. Budget approved

p n  E373 emulsion (ET-7C,D) 200nm Size of AgBr crystals Size 40nm RMS 9nm Development #4 Fine crystal emulsion NIT(Nano Image Tracker) developed by Nagoya U. SEM Micrographs of AgBr crystals Dark Field Image of Light Microscope Tracks due to 5MeV α - particles Merit 1) get better position resolution. 2) insensitive for beam track => higher dense exposure. Under development We will use this as possible. Sep.09,2004 AGS-PAC 15 / 20

p n  High accuracy Ge resolution < 1.5 keV (FWHM) at 0.3 MeV -> Accuracy of X-ray energy ~ 0.2 keV (FWHM) < Expected energy shift 0.3 － 3 keV (Friedman, Gal) The first measurement of  - -atomic X rays  employing “Hyperball” (Ge detector array) Sep.09,2004 AGS-PAC 16 / 20 Experimental motivation III > 100 counts for each Quite low background Take clear  - stopping events only identified in emulsion.  Energy shift ->  - nucleus potential ->  -N interaction H.Tamura

p n  Revised 9 Be (K -,  -  ) 9  Be Observed “Hypernuclear Fine Structure” AGS E930: Precision  spectroscopy of  Hypernuclei for  N interaction (‘98,‘01)  N tensor force: T  = 0.03 MeV  N spin-orbit force: S  = MeV 43±5 keV 26.1±2.0 keV 16 O (K -,  -  ) 16  O E  (keV)E  (keV) Ukai et al., submitted to PRL. Akikawa et al., PRL 88 (2002) Hyperball (Ge array)  E ~ 3 keV (FWHM) + D6 line M. Ukai won a RHIC-AGS thesis award this year.

p n  Add six new “Clover” Ge detectors -> efficiency doubled (6 Clover + 8 single detectors) eff. ~ 6% at 0.3 MeV much higher than the proposal ( ~ 4%) K-K- single Ge detector  = 60%] x 14 “Clover” Ge detector  = 125%] x 6 K+K+ All new detectors working fine. In-beam test of Clover Ge OK. Construction completed by November, 2003 Development #5 Hyperball2 E964 setup to BNL Sep.09,2004 AGS-PAC 18 / 20

p n  Summary Physics : 1) making a S=-2 nuclear chart by ~10 2  Z via 10 4   -stopping events. => at least several nuclides will provide us  B  definitive information. 2) confirm  production enhancement. obtain the information about the component of H-dibaryon state in S=-2 system by A-dependence of  B  & decay of  Z. 3) the First measurement of X-ray of  -atom => may give us   -nucleus potential. Preparation of the E964 experiment : 1) cutdown in requested beam time : 1400 => 750 hours 2) #1 DSSDs has been ordered. #2 Development of emulsion scanning system is in progress. #3 Mass-production of emulsion has been ready. #4 Test of fine crystal emulsion is in progress. #5 Hyperball2 will be ready soon. Sep.09,2004 AGS-PAC 19 / 20

p n  Conditions # Experimental budget : $3M by JPN Gov. (’03~’07) [necessary time before running after its decision] at least 10 months # 6 months : from order to delivery of emulsion 4 months : emulsion plate making [Budget profile]: # emulsion : ~$0.8M in JFY2004 & 2005 => hope to run in the beginning of 2006 it will be spoiled in ~one year, we can’t keep it for a long time (ex.2yrs). We will pay for everything except beam time. We are able to run in FY2006 and hope that. Sep.09,2004 AGS-PAC 20 / 20