np

E373 / E522
Λ Study of Double Strangeness Systems
 Experimental motivation

PS-Review2004
Jun.07
K.Nakazawa

Quit limited experimental information=> Information Λ-Λ force,for understanding B-B int. in SU(3)f
investigating Multi-strangeness system, “strange matter”

Existence of the H-dibaryon
Coupling effectDouble Strangeness Systems

np

PS-Review2004
Jun.07
K.Nakazawa

ΛExperimental status before E373



3 candidate events (Double-Λ) in the 20th century.
M.Danysz et al., PRL.11(1963)29;

D.J.Prowse, PRL.17(1966)782

S.Aoki et al, PTP.85(1991)1287R.H.Dalitz et al., Proc. R.S.Lond.A436(1989)1?
? ?
?
in ~4 Ξstops

ΔBΛΛ = 4.3


0.4 MeV6?? ?

HeKEK-E176
in ~80 ΞstopsΛΛΔBΛΛ = 4.6
ΔBΛΛ = 4.9



0.5 MeV

if a doughter Λ9 Be is in excited
ΔBΛΛ ~1.3MeV

Why VΛΛ so strong?
“interesting theoretical problem”
C.B.Dover, Proc. HYP91, NP.A547(1992)27C

0.7
  MeV0.8


if a doughter 13
ΛC is in excited
ΔBΛΛ ~0MeVor10BeΛΛ

ΔBΛΛ = -4.8
0.7 MeV0.8

How to produce S=-2 SystemsnΛp

Direct process

via Ξ atom

K+K+K

PS-Review2004
Jun.07
K.Nakazawa

K−−pp

ΛΛ

KEK- E176 K+K

KEK- E176
E224 K−
BNL- E813
E836
HE885

Ξ−
ΛΛ

3 Cands.

−KoΞ

Λ
Λ

K−
ΛΛ
Λ

Λ

ΛΛ
orH

KEK-E176
E373AΞ atomΛ−Ξ−KEK- E224

Prowse(?),Danyszetal.
KEK-E176,E373
BNL-E906

Ξ −p=> ΛΛ+28MeV

KEK- E176
E224
BNL- E885KΞ −or H (?)

Ξ−+K−

π

K+

ΛA *(S= −2)ΛΛ Λ KEK-E176
orH

E224
BNL-E885

ΛKEK-E373

np

PS-Review2004
Jun.07
K.Nakazawa

ΛStudy of S=-2 Nuclear Systembyan Emulsion-Counter Hybrid Method
K E K -E 373 collaborators

Japan(16 Univ.・Inst.)

Aichi-edu, Gifu, Higashi-Nippon-Kokusai, KEK, Kobe, Kyoto,Kyoto-Sangyo, Nagoya, Nat. Inst. Rad. Sci., Osaka-city, Osaka-ele.-comm.,
Science-center Osaka pref., Toho, Tohoku, Tokyo, Tsuru

Korea(4 Univ.)

Gyeonsang National Univ., Chonnam National Univ.,
Wonkwang Univ., Konkuk Univ., Korea Univ.

USA(3Univ.・Inst.)
BNL, Univ. New Mexico,Carnegie Mellon Univ.

UK(1Univ.)
Univ. College London

Analysis for 103 stopped Ξ− events (statistics 10 times more than KEK-E176)

・Λ-Λ interaction energy
・existence of Ｈ dibaryon・ ΛΛ weak interaction (ΛΛ => Λn, ΣN)・level energy of Ξ in nucleus

npExperimental Method (KEK-E373)
Λ Scintillating-fiber

Area : 24.5 25.0 cm2
K
Packed in vacuum chamber
Emulsion Mover

Emulsion Stack

Bundle Tracker+SCIFI Blo ck

 Controlled with PC

1.66GeV/cK-

SCIFI Block−ΞDiamond(12C) Targetπ−ZAΛΛπZ'A'ΛΛSide View
Thin type (#1)

Thick type (#2)

Ξ−Emulsion
Thickness(t = 100μm)

PS-Review2004
Jun.07
K.Nakazawa

t=500μm(#12)− Move emulsion during spills
 Keep track density to 1

106/cm2

Scintillating-fiber blocks (KEK-E373)

np

PS-Review2004
Jun.07
K.Nakazawa

ΛReadout with Image Intensifier Tube and CCD
Cross section of a fiber : 0.3 x 0.3 mm2
Cross section of a block : 10 x 10 x 10 cm3
There is almost NOT dead area.
Diamond Target (2 x 2 x 3 cm3)

n

KEK-E373: Automatic track findingpΛ

Algorism

PS-Review2004
Jun.07
K.Nakazawa

Raw Image1) Take picturesat different z(focusing)position.
zemulsion lamp

2) Make overllapped image
shift each imageby (-Δx,-Δy)}Overlap Image~100µmn

Typical Twin single-Λ hypernucleusp

Λ

PS-Review2004
Jun.07
K.Nakazawa

Preliminary・Ξ-+12C→ 6ΛHe(#2)+ 7ΛLi(#1)#2#1BΞ- =1.6MeV(7ΛLi* :0.9±0.3MeV) 2P→ 5ΛHe+ 7ΛLi+nBΞ- =1.1MeV(7ΛLi* :0.4 ±0.4MeV) 3D・Ξ-+14N→ 5ΛHe+ 9ΛBe+nBΞ- =10MeV(9ΛBe* :6.9 ±1.0MeV) 0s

Ξ-n

Double hypernucleus #2p

ΛVertices A and Bcoplanar#5#5 stopped in base film
#6have to beπ#7 left emulsion

#6#7

BA10C
500

510μm

Ξ-PS-Review2004
Jun.07
K.Nakazawa

nReconstruction and ΔBΛΛ

p

Λ

Decay

PS-Review2004
Jun.07
K.Nakazawa

by Y.S. Iwata & H. Takahashi

Production(ΔBΛΛ<20MeV)(ΔBΛΛ>−20MeV)

np

PS-Review2004
Jun.07
K.Nakazawa

Nuclear Physics with double strangeness (S=-2)
KEK-E373 => AGS-E964 ……> J-PARC

Λ Observation of a Λ 6ΛHe (KEK-E373)

Success of Emulsion detector with micro-meter accuracy

NAGARA event6ΛΛ He double-hypernucleus

High Energy News
Vol.20 No.5 (2002)
KEKUnique interpretation!!
46
Ξ- + 12C
ΛΛ He + He + t
56
ΛΛHeΛHe + p +π

H.Takahashi et al.,P. R. L. 87, 212502(2001)

Lambpha6m(ΛΛHe)=5951.82 0.54MeV+0.18BΛΛ=7.25 0.19MeV-0.11+0.18
ΔBΛΛ=1.01 0.20MeV-0.11(assumedBΞ-=0.13MeV)

π-m(Ｈ)≧2223.7MeV/c 2p(90%C.L.)6
ΛΛHe4He105
ΛHe1210ΛΛ10ΛΛ

1413ΛΛ

:t

Ξ-50＊two body case at point A
Ξ- + C → Be + t or Be* + t
ΔBΛΛ ：-1.14 0.19 or +1.86 0.19MeVBΛΛ ：12.29 0.17(excited) MeV ＊three body case at point A
15.29 0.17(ground) MeV1) Ξ- + N → B + p + n
ΔBΛΛ ：+1.47 +2.4
- 0.7 MeV

Aproton−Ξ
0510μmhttp://www.phys.ed.gifu-u.ac.jp/Topics/NAGARA-e.htm

CBKEK-E373 → AGS-E964npΛPS-Review2004
Jun.07
K.Nakazawa

Theoretical calculation for light double hypernuclei

KEK-E373 (Preliminary results)*) ~103 Ξ− stopping events in nuclear emulsion.

ΔBΛΛ : Λ−Λ interaction energy [MeV]*) Observation of several double-Λ hypernuclei=> NAGARA event (without any ambiguities).

2σ
1σ

AGS-E964 (statistics X 10)*) ~10ΛΛ interaction is attractive but weak・7th publication award (JPS)  E176
・Gifu Univ. Award Iwata (MS)・Young scientist Award  Ichikawa(DC) Takahashi (DC)・Three DC students

4 Ξ− stopping events in nuclear emulsion.

*) ~10 double-Λ hypernuclei (without any ambiguities).

=> making a nuclear chart with S=-2.
A-dependence of ΔBΛΛ in several nuclides.
−*) X-ray measurement from Ξ -atom, for the first time.
=> information of Ξ-N interaction.
*) funded by JPN. Gov., already. (2003~2007)

H-Dibaryon resonance searchnΛΛΛ Invariant mass spectrum
KEK-PS E224

Predicted masses

H mass (0.1GeV/c2/bin)pPS-Review2004
Jun.07
K.Nakazawa

19751985

1995

2000

Updated from the year 1995, referred onS.V.Bashinsky, R.L.Jaffe, Nucl. Phys. A625(1997)167,and W.J.Lope, talk given at ‘12th Winter Workshop on Nuclear Dynamics’

J.K.Ahn et al., (KEK-E224)
Phys. Lett. B444 (98) 267

H-dibaryon resonance : KEK-E522np

ΛPS-Review2004
Jun.07
K.Nakazawa

nH-Dibaryon resonance : KEK-E522p

ΛPS-Review2004
Jun.07
K.Nakazawa

nH-Dibaryon near the ΛΛ thresholdp

Λ
KEK-PS E224

J.K.Ahn et al., (KEK-E224)
Phys. Lett. B444 (98) 267

PS-Review2004
Jun.07
K.Nakazawa

KEK-PS E522

Future plann

PS-Review2004
Jun.07
K.Nakazawa

Λp

PS-E559(High Resolution Spectroscopy of Pentaquark Θ+)
PS-Shutdown

AGS-E964(2006?)[Spring8/RHIC]↓↓↓↓↓↓J-PARC

3000/7000

E964 experimentnp

Nuclear Physics with double strangeness (S=-2)
Λ

PS-Review2004
Jun.07
K.Nakazawa

KEK-E373 => AGS-E964 ……> J-PARC

Title : Systematic Study of Double
AGS-E964 (statistics X10 of the past experiments)
Strangeness System with*) International collaboration(USA/China/India/JPN/Korea/Myanmar/UK)
an Emulsion-Counter*) ~104 Ξ- stopping events in nuclear emulsion.
Hybrid Method.
*) ~10 double-Λ hypernuclei
Beam : K- (1.7GeV/c),(without any ambiguities).
52 x 10 K /spill (4.1sec)=> making nuclear chart with S=-2.
with K /π >9 at D6-line
A-dependence of ΔBΛΛ in several nuclides.
*) X-ray measurement from Ξ--atom,
Detectors : Nuclear Emulsion,for the first time.
Double-sided Si strip Detector,=> information of Ξ-N interaction.
Ge-Detector (Hyperball),*) funded by JPN. Gov., already.
KURAMA magnet(2003~2007)
Time requested :100 hours for detector tuneE964 leads the community of hypernuclear
100 hours for beam tune
physics to significant activities at J-PARC.
1100 hours for beam exposureSetup around the target (E964)

npΛ

PS-Review2004
Jun.07
K.Nakazawa

Volume of nuclear emulsion
70 liters (E373) => 210 liters
Track scanning method
Automated + Interactive (E373)=> Fully Automated (speed x 4)
Emulsion Mover Controlled with PC

Move emulsion during spills
 Keep track density to 1
106/cm2
DSSD(Double-Sided Si Detector)
Precise prediction of Ξ- tracks
on the first emulsion plate.
=> Reduction in background tracks
which are picked up in the first plate.

Quite low background
X-ray data are only analyzed forclear Ξ- stopping events which areidentified by nuclear emulsion.

nDevelopment of Automatic ScanningpΛ

Images are shown:
1. Surface detection=> Grid measurement
for position calib.
2. Track scanning

Current system

Surface & Grid : 22 sec.
Track_scan: 15 sec.

Developing system

Surface & Grid : 9 sec.
Track_Scan: 6 sec.

PS-Review2004
Jun.07
K.Nakazawa