p n systematic study of double strangeness system by an emulsion-counter hybrid method experimental...
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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 E964R and Development since 2001Ⅰ. Double-sided Si Strip Detector (DSSD).Ⅱ. Nuclear Emulsion.Ⅲ. Hyperball2
Summary Conditions
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Phys. Dept., Gifu Univ.K.Nakazawa
Current status of AGS-E964
Dept. of Phys., Tohoku Univ.H.Tamura
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*two body case at point AΞ - +
12C → 10Be + t or 10Be* + tΛΛ ΛΛ
Δ BΛΛ : -1.14± 0.19 or +1.86± 0.19MeVBΛΛ :12.29± 0.17(excited) MeV 15.29± 0.17(ground) MeV
*three body case at point A1) Ξ - + 14N → 13B + p + n
Δ BΛΛ : +1.47 MeV+2.4- 0.7
Λ Λ
::
protonA
CΞ
B
Demachi-yanagi event
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),p5.
5
6ΛΛHe
4He
t
Ξ -
p
π -
ΛHe
10μm500
10
5
2001
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Comparison with past results
inte
ract
ion
en
ergy
12
or or
or
or
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interaction is weakly attractive.Our knowledge for int. until now.
E373
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B & nuclear medium effect
To know int. independent on the nuclear medium effect, we need to measure A-dependence of B.
B:
b
ind
ing
en
erg
y in
nu
cleu
s
S=-2 nuclear system
‘H’
B depends on A
B may NOT depend on A
Theoretical prediction
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Candidate events of double-hypernucleus
from E373
preliminary
20023rd double- hypernucleus
Nuclear species of the double- can be , or .
He He
Be
2003
2004
2003
Analysis in progress
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Nuclear Chart with Strangeness
Experimental motivation Ⅰ
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Strange matter 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 threshold
KEK-PS E522
Experimental motivation Ⅱ
What is the ground state of S=-2 nucleus?
Recent result
2. A-dependence of B3. Decay branching ratio [S=-2] => p, n
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M()thres.
1. Confirm this enhancement by several times higher statistics.
or H-dibarion state in nucleus?|H> √a √b N> - √c |mixing?
‘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 %
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The first measurement of X-ray of -atom-nucleus potential can be seen.
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H.Tamura will introducethis with the developmentof Hyperball 2, later.
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Nuclear Physics with double strangeness (S=-2)
KEK-E373 => AGS-E964
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6 countries16 institutes34 staffs+ Graduate stu.
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Outline of E964R
# Beam : K- (1.7GeV/c), 2 x 105 => 4 x 105 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 tune1100 =>600 hours for beam exposure
# Trigger : (K-, K+) => 104 - stopping events (10 times higher stat. than E373)
We request Beam time in FY2006
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Experimental setup of E964Sep.09,2004
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Development #1Double-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 : 30x60mm2 / Thickness : 0.3mm / pitch : 50m
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Development #2 Automatic Scanning
Current systemSurface & Grid : 22 sec.Track_scan : 15 sec.
Images are shown: 1. Surface detection => Grid measurement for position calib.2. Track scanning
Developing systemSurface & Grid : 9 sec.Track_Scan : 6 sec.
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x3 faster
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Development #3 Production method of emulsion
Production method of Emulsion gel will be changed.For E964, amount of emulsion gel => 2.4 tonsFuji-film needs one year or more by conventional way.
Emulsion costwill be saved
50%
by the product ion lines for commercial f ilms
Conventional way by hand
Using the production lines for commercial films
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Stopping power and physicalcharacteristic has been tested,and the result showed no problem.
Budget approved
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E373 emulsion (ET-7C,D)
200nm
Size of AgBr crystals
Size 40nmRMS 9nm
Development #4 Fine crystal emulsion
NIT(Nano Image Tracker) developed by Nagoya U.
SEM Micrographs of AgBr crystalsSEM Micrographs of AgBr crystals
Dark Field Image of Light MicroscopeDark Field Image of Light Microscope
Tracks due to 5MeV α - Tracks due to 5MeV α - particlesparticles
Merit1) get better position resolution.
2) insensitive for beam track => higher dense exposure.
Under development
We will use this as possible.
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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)
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> 100 counts for each
Quite low background
Take clear - stopping events only
identified in emulsion.
Energy shift -> - nucleus potential -> -N interaction
H.Tamura
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Revised
9Be (K-, -) 9Be
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= - 0.01 MeV
43±5 keV 26.1±2.0 keV
16O (K-, -) 16O
E(keV)E(keV)
Ukai et al.,submitted to PRL.
Akikawa et al.,PRL 88 (2002) 082501.
Hyperball (Ge array) E ~ 3 keV (FWHM)
+ D6 line
M. Ukai won a RHIC-AGS thesis award this year.
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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-single Ge detector
= 60%]
x 14
“Clover” Ge detector= 125%]
x 6
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
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Summary
Physics :1) making a S=-2 nuclear chart by ~102 Z via 104 -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.
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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.
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