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1. The Physics Case2. Present Status3. Hypersystems in pp Interactions4. The Experiment
Future Experiments on Hypernuclei and
Hyperatoms
_
1. The Physics Case
baryons tagged with a strange quark as a probe of the nuclear structurenuclei as a femto-laboratory for strange baryons
Two Sides of a Coin
mesonic decay of hypernuclei
mesonic decay of hypernuclei
w
N
suppressed by Pauli blocking
pF270MeV/c
w
N
pN100MeV/c
free decayfree decay
0n
+38MeV ( )
+41MeV ( )
2
6
6
4
36
%
%
3ps
p
non-mesonic decay
of hypernuclei
non-mesonic decay
of hypernuclei
w
N
s
N
N
+176MeV
+176MeVnn
p
n
p n
To use nuclei as a QCD-laboratory we have to understand the laboratory
s=1: -, -hypernucleinuclear structure, new symmetries
the presence of a hyperon may modify the size, shape... of nuclei new specific symmetries
Y-N interactionstrange baryons in nuclei weak decay
s=2: -atoms, -, -hypernucleinuclear structurebaryon-baryon interaction in SU(3)f
H-dibaryon
s=3: -atom, (-,-, -hypernuclei ?)quadrupole moment of the
Hypernuclei provide a link between nuclear physics and QCD
Strange Baryons in Nuclear Systems
W
su dusd dd
meson vs. gluon/quark exchange
meson vs. gluon/quark exchange
Weak baryon-baryon interaction non-mesonic weak decay of hypernuclei explore the baryon-baryon weak interaction
N-N scatteringN-N scattering
w
N
N
s
N
N
w
N
s
N
N
S=0 S=1
NN NNN N
only parity violating part of weak interactionparity-conserving part masked by strong interaction
only parity violating part of weak interactionparity-conserving part masked by strong interaction
parity violating and parity-conserving part of weak, strangeness changing, interactionq~400 MeV/c probes short distances
parity violating and parity-conserving part of weak, strangeness changing, interactionq~400 MeV/c probes short distances
T. Sakai, K. Shimizu, K. Yazaki Prog.Theor.Phys.Suppl. 137 (2000) 121-145
H-Particle R.L. Jaffe (1977)
free coalescencet ~ 10-23s
nuclear breeder
t ~ 10-10s
neutron stars
Nuclei as Femto-Laboratory
H-particle in a nucleus free H (see e.g. T. Yamada, NP A691 (2001) 250c; (3q)+(3q) quark cluster model )
free H-dibaryonH-dibaryon in 10
YYBe
B=12.2 MeV B=24.0 MeV
S=-2 Nuclei and H-dibaryon States
Formation of an H-particle in nuclei may modify levels in -nuclei
Contributions to intrinsic quadrupole moment of baryonsOne-gluon exchangeMeson exchange
J=1/2 baryons have no spectroscopic quadrupole moment
- Baryon:J=3/2long mean lifetime 0.82·10-10 sonly one-gluon contributions to quadrupole moment(A.J. Buchmann Z. Naturforsch. 52 (1997) 877-940)
3 2 2( )(3 )iQ d r r z r 3 2 2( )(3 )iQ d r r z r
s
ss
1/ 221/ 2
(3 ( 1)) 0z
Js z J
Q J J J 1/ 221/ 2
(3 ( 1)) 0z
Js z J
Q J J J
Fundamental Properties of Baryons
The quadrupole moment is an unique testcase for the quark-quark interaction
hyperfine splitting in -atom electric quadrupole moment of
prediction Q= (0 - 3.1) 10-2 fm2
E(n=11, l=10 n=10, l=9) ~ 515 keVEQ ~ few keV for Pb
spin-orbit Els ~ (Z)4 l·m
quadrupole EQ ~ (Z)4Qm3
spin-orbit Els ~ (Z)4 l·m
quadrupole EQ ~ (Z)4Qm3
Q= +0.02 fm2
Q= - 0.02 fm2
A very Strange Atom
R.M. Sternheimer, M. Goldhaber PRA 8, 2207 (1973)
2. Present Status
strangeness deposition (stopped K-,-) FINUDA@DANEtagged kaon „beam“low momentum (T=16MeV)low backgroundalso (stopped K-,+) neutron rich nuclei
strangeness production (+, K+) (-, K0) BNL, KEK, (GSI?)
pBEAM 1 GeV/c
high beam intensitylow cross section (1-10 mb/sr)q > 300 MeV/c large p, L
strangeness exchange (K_
, )(K_
, ) BNL, KEK, J-PARClow beam intensitylarger cross section (100 mb/sr)magic momentum low p, L
(e,e´K+) , (,K+) TJNAF, MAMI-Cspin-flip amplitude unnatural parity statesnew nuclei (p : 10
Be)
polarised beamsub-MeV resolution possible (0.3 MeV) for particle unstable states
substitutional state
non-substitutional state
Single Hypernuclei
( 1)A Ae Z e K Z ( 1)A Ae Z e K Z
stoppA
dA
e
KK
Z ZK
e e
stoppA
dA
e
KK
Z ZK
e e
Tamura et al.
Neutron number
16Λ O 18
Λ O14Λ N 15
Λ N12Λ C 13
Λ C 14Λ C
9ΛB 10
Λ B 11Λ B 12
Λ B7ΛBe 8
ΛBe 9ΛBe10
Λ Be6ΛLi 7
ΛLi 8ΛLi 9
ΛLi4ΛHe 5
ΛHe6ΛHe 7
ΛHe 8ΛHe
4ΛH3
ΛH
1 2 3 4 5 6 7 8 9
4
8
7
6
3
5
2
1
10
9
Pro
ton
nu
mb
er
Status of Single Hypernuclei
high resolution -spectroscopy
with germanium detectors
7 0.5 2 40.4
6 2 4
( 2; : 5 / 2 1/ 2 ) 3.6 0.5 1
( 2; : 3 1 ) 10.9 0.9 3
B E Li e fm
B E Li e fm
B(E2)~R4
shrinkage of 6Li core by ~20%
high resolution -spectroscopy is crucial to understand the structure of hypernculei
KEK, BNL
Multi-Hypernuclei are terra incognita, but they exist !
1963: Danysz et al. 10Be
1966: Prowse 6He
1991: KEK-E176 13B (or 10Be)
2001: AGS-E906 4H (~15);
no binding energies
2001: KEK-E373 6He
(Nagara)
“ 10Be
(Demachi-Yanagi)
NAGARA
6- 12 4
6 5
ΛΛ
-ΛΛ Λ
Ξ + C + He+t
He He+ π
He
p+
H. Takahashi et al., PRL 87, 212502-1 (2001)
Double Hypernuclei
Interpreting B as bond energy one has to consider e.g.
dynamical change of the core nucleusN spin-spin interaction for non-zero spin of coreexcited states possible
if- or intermediate -nuclei are produced in excited statesQ-value difficult to determine (particularly for heavy nuclei)nuclear fragments difficult to identify with usual emulsion technique
new concept required -spectroscopy!
1
1
( ) ( ) ( )
( ) ( ) ( )
A A A
A A A
B Z B Z B Z
B Z B Z B Z
What is known?
6
6 0.18 0.180.11 0.11
10
10
13
Hyperkern ( ) ( )
10.9 0.5 4.7 0.6 Prowse (1966)
7.25 0.19 1.01 0.20 KEK-E373 (2001)
17.7 0.4 4.3 0.4 Danysz (1963)
8.5 0.7 4.9 0.7 KEK-E176 (1991)
27.6 0.7 4.8
B MeV B MeV
He
He
Be
Be
B
10 0.35
0.21
0.7 KEK-E176 (1991)
12.33 KEK-E373 (2001, unpublished)Be
same event
same event
3. Hypersystems in pp Interactions_
-atoms: x-raysconversion
-(dss) p(uud) (uds) (uds)Q = 28 MeV
Conversion probability approximatly 5-10%
Y. Hirata, J. Randrup et al.,
- capture
_
(Kaidalov & Volkovitsky)
quark-gluon string model
s
ud
s
dd
s
ds
s
ss
0
Use pp Interaction to produce a hyperon “beam” (t~10-10 s) which is tagged by the antihyperon or its decay products
_
General Idea
- capture:
- p + 28 MeV-
3 GeV/c
Kaons_
trigger
p_
2. Slowing down and capture
of insecondary
target nucleus
2. Slowing down and capture
of insecondary
target nucleus
1.Hyperon-
antihyperonproductionat threshold
1.Hyperon-
antihyperonproductionat threshold
+23MeV
3. -spectroskopy
with Ge-detectors
3. -spectroskopy
with Ge-detectors
Production of Double Hypernuclei
20000 stopped -K- beam, diamond target
neutron detector arrays
(--,12C) 12B + nBNL-AGS E885
few tens 2 decays of 4
HK- beam lineCylindrical Detector
System2 decaysBNL-AGS
E906
Captured - per day
beam/ targetdevicereactionfacility
several hundreds stopped -
(K-,K+)emulsion(K-,K+)KEK-PS E373
vertex detector + spectrometer
vertex detector
spectrometer, =30 msr
device
3000 „golden events“
~ 300000 KK trigger
(incl. trigger)
=2·1032, thin target,production vertex decay vertex
p p GSI-HESR
2000106 stopped p per sec
p p K*K*
K*N Kcold anti-protons
<70008·106/sec5 cm 12C
(K-,K+)JHF
statusbeam/ targetreactionexperiment
Competition
¯
¯
¯
¯
¯¯
Expected Count Rate
Ingredients (golden events)luminosity 2·1032 cm-2s-1 +- cross section 2mb for pp 700 Hz p(100-500 MeV/c) p500 0.0005 + reconstruction probability 0.5 stopping and capture probability pCAP 0.20 total captured - 3000 / day
- to nucleus conversion probability p 0.05 total hyper nucleus production 4500 / month
gamma emission/event, p 0.5
-ray peak efficiency pGE 0.1
~7/day „golden“ -ray events (+ trigger) ~ 700/day with KK trigger
high resolution -spectroscopy of double hypernuclei will be feasible
- capture:
- p + 28 MeV-
5.5 GeV/c
Kaons_
trigger
p_
2. Slow down
and capture of in
secondary target nucleus
2. Slow down
and capture of in
secondary target nucleus
1.Hyperon-
antihyperonproductionat threshold
1.Hyperon-
antihyperonproductionat threshold
+203MeV
3. -spectroskopy
with Ge-detectors
3. -spectroskopy
with Ge-detectors
Production of -Atoms
( ) 1( ) 20
atoms by produktion (~35/sec)hyperfine splitting in -atom
electric quadrupole moment of
prediction Q= (0 - 3.1) 10-2 fm2
E(n=11, l=10 n=10, l=9) ~ 515 keVEQ ~ few keV for Pb
taking production rate, stopping probability, capture probability and detection probability into account we expect
-
spin-orbit Els ~ (Z)4 l·m
quadrupole EQ ~ (Z)4Qm3
spin-orbit Els ~ (Z)4 l·m
quadrupole EQ ~ (Z)4Qm3
Q= +0.02 fm2
Q= - 0.02 fm2
~10 detected -transitions per daywith high resolution -spectroscopy feasible
A very strange Atom
R.M. Sternheimer, M. Goldhaber PRA 8, 2207 (1973)
Count rate estimate needs more detailed studies!
4. The Experiment
The PANDA Detector
hermetic (4)high ratePID (, e, , , K, p)trigger (e, , K, D, ) compact (€)modular
Elektronenkühler
InjektionKicker Septum
Solid state-micro-trackerthickness ~ 3 cm
High rate germanium detector
Summary
Hypersystems provide a link between nuclear physics and QCD
They allow to study basic properties of strongly interacting systems
These unique experiments will be feasible at the GSI-HESR