Systematic Study of Double Strangeness System by an Emulsion-Counter Hybrid Method

1
Systematic Study of Double Strangeness System
by an Emulsion-Counter Hybrid Method
Sep.09,2004 AGS-PAC 1 / 20
Phys. Dept., Gifu Univ. K.Nakazawa
Dept. of Phys., Tohoku Univ. H.Tamura
Current status of AGS-E964

• Experimental motivation.
• 0 . Previous experiment E373 (KEK-PS) 97
  scanned.
• ?. Making a S-2 nuclear chart.
• ?. Study of H-resonance or dibaryon state.
• ?. First measurement of X-ray from X-atom
• Outline of E964R and Development since 2001
• ?. Double-sided Si Strip Detector (DSSD).
• ?. Nuclear Emulsion.
• ?. Hyperball2
• Summary
• Conditions

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Double-L hypernuclei from E373(KEK-PS)
Sep.09,2004 AGS-PAC 2 / 20
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),p5.
2001
2001
3
Comparison with past results
Sep.09,2004 AGS-PAC 3 / 20
or
or
or
or
E373
4
DBLL nuclear medium effect
Sep.09,2004 AGS-PAC 4 / 20
Theoretical prediction
S-2 nuclear system
DBLL may NOT depend on A
BLL LL binding energy in nucleus
DBLL depends on A
To know LL int. independent on the nuclear medium
effect, we need to
measure A-dependence of DBLL.
5
Candidate events of double-hypernucleus from E373
Sep.09,2004 AGS-PAC 5 / 20
Analysis in progress
2002
3rd double-L hypernucleus
preliminary
2003
2003
2004
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Nuclear Chart with Strangeness
Sep.09,2004 AGS-PAC 6 / 20
Experimental motivation ?
Our goal is making a S-2 nuclear chart, by
observing so many nuclei with S-2 as possible.

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H-dibaryon resonance (?)
near the LL threshold
Sep.09,2004 AGS-PAC 7 / 20
Experimental motivation ?
Recent result
1. Confirm this enhancement by several
times higher statistics.
KEK-PS E522
What is the ground state of S-2 nucleus?
LL or H-dibarion state in nucleus? Hgt va LLgt
vb XNgt - vc SSgt mixing?
2. A-dependence of DBLL 3. Decay branching ratio
S-2 gt S-p, Ln
E373 data Br(LLgtS-p) lt 12, by 1/4
data and assumption P (X-stopgtLLZ)20


result of KEK-E176 E964
can achieve Br(LLgtS-p) lt 0.3 Br(LLgtLn)
lt 3
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Experimental motivation ?
Sep.09,2004 AGS-PAC 8 / 20
The first measurement of X-ray of
X-atom X-nucleus potential can be seen.
H.Tamura will introduce this with the
development of Hyperball 2, later.
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Nuclear Physics with double strangeness (S-2)
KEK-E373 gt AGS-E964
Sep.09,2004 AGS-PAC 9 / 20
6 countries 16 institutes 34 staffs Graduate
stu.
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Outline of E964R
Sep.09,2004 AGS-PAC 10 / 20
Beam K- (1.7GeV/c), 2 x 105 gt 4 x 105
K-/spill with K-/p-gt9 at D6-line Detectors
Nuclear Emulsion, Double-sided Si
strip Detector (DSSD),
Ge-Detector (Hyperball),
KURAMA magnet carried from Japan Time requested
300 gt150 hours for detector tune 1100
gt600 hours for beam exposure Trigger
(K-, K) gt 104 X- stopping events (10 times
higher stat. than E373)
We request Beam time in FY2006
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Experimental setup of E964
Sep.09,2004 AGS-PAC 11 / 20
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Development 1 Double-sided Si Strip Detector
(DSSD)
Sep.09,2004 AGS-PAC 12 / 20
Precise tracking of X- hyperons for the top
emulsion plate. gt Reduction of background
tracks, which are picked up in the plate.
gt Speeding up of emulsion scanning.
2nd Surface
1st Surface
Effective area 30x60mm2 / Thickness 0.3mm /
pitch 50mm
Two sets in the 4mm gap between the Target
Emulsion.
DSSDs have already been ordered to HAMAMATSU
Photo Co.Ltd.
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Development 2 Automatic Scanning
Sep.09,2004 AGS-PAC 13 / 20
Current systemSurface Grid 22
sec.Track_scan 15 sec.
Developing systemSurface Grid 9
sec.Track_Scan 6 sec.
x3 faster
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Development 3 Production
method of emulsion
Sep.09,2004 AGS-PAC 14 / 20
Production method of Emulsion gel will be changed.
For E964, amount of emulsion gel gt 2.4 tons
Fuji-film needs one year or more by conventional
way.
Conventional way by
hand
Using the production lines for
commercial films
Emulsion cost will be saved 50
Stopping power and physical characteristic has
been tested, and the result showed no problem.
Budget approved
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SEM Micrographs of AgBr crystals
Sep.09,2004 AGS-PAC 15 / 20
Development 4 Fine crystal emulsion
Size of AgBr crystals
NIT(Nano Image Tracker) developed by Nagoya U.
E373 emulsion (ET-7C,D)
Size 40nm RMS 9nm
Tracks due to 5MeV a - particles
Merit 1) get better position
resolution. 2) insensitive for beam track gt
higher dense exposure. Under development We
will use this as possible.
Dark Field Image of Light Microscope
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Experimental motivation III
Sep.09,2004 AGS-PAC 16 / 20
H.Tamura

• The first measurement of X--atomic X rays
• employing Hyperball (Ge detector array)

• Energy shift -gt X- nucleus potential -gt X-N
  interaction

High accuracy Ge resolution lt 1.5 keV
(FWHM) at 0.3 MeV -gt Accuracy of X-ray energy
0.2 keV (FWHM)
lt Expected energy shift
0.3 - 3 keV
(Friedman, Gal)
gt 100 counts for each
Quite low background Take clear X-
stopping events only identified in
emulsion.
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AGS E930 Precision g spectroscopy of L
Hypernuclei for LN interaction (98,01)
Observed Hypernuclear Fine Structure
16O (K-, p- g) 16LO
435 keV
26.12.0 keV
Hyperball (Ge array) DE 3 keV (FWHM) D6
line
Eg (keV)
Eg (keV)
Ukai et al., submitted to PRL.
Akikawa et al., PRL 88 (2002) 082501.
LN tensor force T 0.03 MeV
LN spin-orbit force SL - 0.01 MeV
M. Ukai won a RHIC-AGS thesis award this year.
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Sep.09,2004 AGS-PAC 18 / 20
Development 5
E964 setup
Hyperball2
K
to BNL
K-
Construction completed by November, 2003
Add six new Clover Ge detectors -gt
efficiency doubled
(6 Clover 8 single detectors) eff.
6 at 0.3 MeV much higher than the proposal
( 4)

• All new detectors working fine.
• In-beam test of Clover Ge OK.

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Summary
Sep.09,2004 AGS-PAC 19 / 20

• Physics
• 1) making a S-2 nuclear chart by 102 LLZ via
  104 X--stopping events.
• gt at least several nuclides will
  provide us DBLL definitive information.
• 2) confirm LL production enhancement.
• obtain the information about the
  component of H-dibaryon state in S-2
• system by A-dependence of DBLL decay
  of LLZ.
• 3) the First measurement of X-ray of X-atom
• 
  gt may give us X- -nucleus
  potential.
• Preparation of the E964 experiment
• 1) cutdown in requested beam time 1400 gt 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.

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Conditions
Sep.09,2004 AGS-PAC 20 / 20

• Experimental budget 3M by JPN Gov. (0307)
• 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
• gt hope to
  run in the beginning of 2006
• it will be spoiled in one year, we
  cant 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.