Post on 12-Jan-2016
description
Prospects on Hypernuclear PhysicsProspects on Hypernuclear Physics
• Hypernuclear physics: state of the artHypernuclear physics: state of the art
• DADAΦΦNE: an efficient hypernuclear factoryNE: an efficient hypernuclear factory
• FINUDA physics programFINUDA physics program
• Future prospectsFuture prospects
• ConclusionsConclusions
• Hypernuclear physics: state of the artHypernuclear physics: state of the art
• DADAΦΦNE: an efficient hypernuclear factoryNE: an efficient hypernuclear factory
• FINUDA physics programFINUDA physics program
• Future prospectsFuture prospects
• ConclusionsConclusions
Paola Gianotti
LNF
Hypernuclear Physics: state of the artHypernuclear Physics: state of the art
Hypernuclear physics is a good tool to match nuclear and particle
physics. The study of this field may help in understanding some
crucial questions:
four baryon weak
interaction vertex;
YN and YY strong interactions;
change of hyperon and meson properties in the nuclear medium;
existence of di-baryon particles;
the role played by the quark degrees of freedom,
flavor symmetry and chiral models in nuclear and hypernuclear field.
N N
N
N
N
K
d
6Li
+ d
Li7Λ
120 )(sl)(sl)(ss)()()( SrVrVrVrVrVrV TNN NNΛΛNΛΛN
120 )(sl)(sl)(ss)()()( SrVrVrVrVrVrV TNN NNΛΛNΛΛN
d
s
u
W u
d
dn
u
u
d
u
u
d
pp
The 2nd roundFirst Counter Experiments CERN & BNL1973 Stopped (K,π) at CERN1974 in-flight (K,π) at CERN PS and BNL AGS
very small spin-orbit splitting
The 2nd roundFirst Counter Experiments CERN & BNL1973 Stopped (K,π) at CERN1974 in-flight (K,π) at CERN PS and BNL AGS
very small spin-orbit splitting
The 1st round 1953 Discovery of Λ hypernucleiEmulsion detectors --- CERN PS, BNL AGS K beam
Λ potential depth about 1/2
The 1st round 1953 Discovery of Λ hypernucleiEmulsion detectors --- CERN PS, BNL AGS K beam
Λ potential depth about 1/2
The 3rd roundNew reactions with New Detectors1985 (π+,K+) started at AGS1990 S=-2 searches at AGS and KEK (Emulsion-counter hybrid technique)1993 S=-1 Λ Spectroscopy, Weak decay, SKS spectrometer1998 ray spectroscopy (Hyperball)
ΛN potential definition Γn/ Γp puzzle in the non-mesonic decays
The 3rd roundNew reactions with New Detectors1985 (π+,K+) started at AGS1990 S=-2 searches at AGS and KEK (Emulsion-counter hybrid technique)1993 S=-1 Λ Spectroscopy, Weak decay, SKS spectrometer1998 ray spectroscopy (Hyperball)
ΛN potential definition Γn/ Γp puzzle in the non-mesonic decays
50 years of Hypernuclear Physics50 years of Hypernuclear Physics
Production of Production of ΛΛ-Hypernuclei-Hypernuclei
nK nK
Kn Kn
Kepe )()( Kepe )()(
Different production mechanisms can be used to form an hypernuclei:
strangeness exchange reaction (in flight, stopped)
σ ≈ 100 mb ; Ibeam = 104 s-1
associated production
σ ≈ 1 mb ; Ibeam = 107 s-1
real and virtual photo- production σ ≈ μb ; Ibeam = 1010 s-1
Hyp
eron
rec
oil m
omen
tum
[MeV
/c] θL= 0o
Kn
Kepe )()(
NK
Projectile momentum pLab [GeV/c]
Production of Production of ΛΛ-Hypernuclei-Hypernuclei(K+,π+), and (K-
stop,π-) are similar, both give
to the hyperon a large momentum transferred, but not identical. Many excited hypernuclear states
Electroproduction mainly populates streched
and unnatural parity nuclear states.
DWIA calculationsDWIA calculations
12C(K-,π-)
pK=800 MeV/c
12C(π+,K+) pπ=1040 MeV/c
θ=0o
12C(π+,K+) pπ=1040 MeV/c
θ=0o
12C(K-stop,π
-)
a
b
c
K.Itonaga et al., Prog. Theor. Phys 84 (1990) 291.
T.S.H. Lee et al., Phys. Rev. C 58 (1998) 1551.
12C(,K+)12ΛB
E=1.1GeV
θ=10o
Saclay-Lyon amplitudeSaclay-Lyon amplitude
12C(K-,π-)
Production of Production of ΛΛ-Hypernuclei-Hypernucleiexp. resultsexp. results
12C(,K+)12ΛB
HNSS(E89-009) high resolution (900MeV FWHM) spectrometer
FINUDA experiment high resolution (1.4 MeV FWHM) spectometer
pΛ
sΛ
pΛsΛ
• GOALGOAL: understanding Baryon-Baryon interactions
• NN interaction: experimentally well known from elastic scattering data phenomenologically well reproduced by meson-exchange and quark-cluster models• YN, YY interaction: poor scattering data low yield, short lifetime (c < 10 cm)
Hypernuclear SpectroscopyHypernuclear Spectroscopy
information from hypernuclei are important mostly Λ-hypernuclei ΛN interaction In Λ-hypernuclei: No Pauli effect, weak coupling simple structure extraction of ΛN interaction is rather straightforward
information from hypernuclei are important mostly Λ-hypernuclei ΛN interaction In Λ-hypernuclei: No Pauli effect, weak coupling simple structure extraction of ΛN interaction is rather straightforward
Hypernuclear SpectroscopyHypernuclear Spectroscopy
Phenomenological NN, YN potential, mainly based on OBE mechanism, improves (Nijmegen ESC02, 03) thanks to hypernuclear physics
Textbook example of
Single-particle orbits in nucleus
Hotchi et al., PRC 64 (2001) 044302
The peak positions is well describedby a Wood-Saxon potential
The peak positions is well describedby a Wood-Saxon potential
spectroscopy 7
Li, 9Be, 10
B, 11B, 15
N, 16O KEK E419, E509, E518; BNL E930
13C BNL E929 NaI array
Recent improvements Recent improvements (1998~2003)(1998~2003)
Hyperball
120 )(sl)(sl)(ss)()()( SrVrVrVrVrVrV TNN NNΛΛNΛΛN
S S p shell: 4 radial integrals for pN,sΛ w.f.
KEK E419 (π+,K+) 7ΛLi
Towards hyper-fine splitting understanding
N- LS interaction SN~ -0.4 MeV
N- LS interaction SN~ -0.4 MeV
spin-spin interaction = 0.50 MeV
spin-spin interaction = 0.50 MeV
BNL E930 (K- π-) 9ΛBe S= 0.01 MeVS= 0.01 MeV
BNL E929 (K-,π-) 13ΛC
HYPERBALL
S = 152 ± 54(stat) ± 36(syst) keVS = 152 ± 54(stat) ± 36(syst) keV
The experimental measurements on SΛ are in agreement but smaller than the values given by the meson exchange models
The experimental measurements on SΛ are in agreement but smaller than the values given by the meson exchange models
NaI
BNL E930 (K π) 13ΛC
OBEP predictions agree with the experimental value ND NF NSC89 NSC97f T (keV) 18 33 36 54
OBEP predictions agree with the experimental value ND NF NSC89 NSC97f T (keV) 18 33 36 54
T ~ 30 keV (prelim.) First info. on TT ~ 30 keV (prelim.) First info. on T
ΛΛΛΛ interactioninteraction• Unique channel in SU(3) BB interaction classification• Repulsive core may vanish in this channel possibile existense of H-dibaryon (uuddss, J=I=0)• Original prediction by Jaffe (PRL38 (1977) 195) - H is predicted 80 MeV below ΛΛ mass • No experimental evidence so far - at least, deeply bound H is rejected• ΛΛ - Ξ N (- ΣΣ) coupling important (ΔE = 28 MeV)• ΛΛ interaction study performed by - ΛΛ hypernuclei - ΛΛ final state interaction in (K-,K+) reaction (J. K. Ahn et al., PLB444 (1998) 267 )• Present data suggests ΛΛ interaction is weakly attractive
Hybrid emulsion experiment Hybrid emulsion experiment (KEK-PS E373)(KEK-PS E373)
• Hybrid emulsion -- (K-,K+) reaction to produce Ξ -
then stop it in emulsion• The best event found (H. Takahashi et al., PRL87(2001)212502)
6• Track #1 is the• Binding energy of is obtained to be B = 7.3±0.3 MeV (from )• In order to extract interaction, we take B = B = 1.0±0.3 MeV weakly attractive
• Track #1 is the• Binding energy of is obtained to be B = 7.3±0.3 MeV (from )• In order to extract interaction, we take B = B = 1.0±0.3 MeV weakly attractive
He6
He
He5
K- K+
-
Chain of π- decays (BNL E906)
D6 line CDS detector: (K-,K+) Ξ - , Ξ - + 9Be -> ΛΛ Z + X
First production of ΛΛ hypernuclei by a counter experiment
PRL 87(2001) 132504
3H
4H
4 ΛΛ H → 4
ΛHe* + π- (104)
→ 3 Λ H + p
→ 3He + π- (114.3)
3H
4H
Neutron rich Neutron rich ΛΛ-Hypernuclei-Hypernuclei
Better candidates to study matter with extreme N/Z ratio are neutron rich Λ-hypernuclei 7
ΛH, 6ΛH, 12
ΛBe,...
Here more extended mass distribution are expected thanks to the “gluing role” of the Λ
Interesting also for astrophysics studies on high density nuclear matter in neutron stars
A new branch of nuclear physics is studyng light nuclei with extended spatial distribution giving rise to a neutron halo.
number of neutrons
number of protons
solarburning
Proton-rich nuclei
Neutron-rich nuclei
Superheavy elements
Neutron rich Neutron rich ΛΛ-Hypernuclei-HypernucleiTretyakova et al., Nucl. Phys, A691 (2001) 351c, Akaishi et al., Frascati Phys. S. XVI, (1999) 59
Two different production mechanisms have been invoked:1. Double charge exchange
K- p → Λ π0 ; π0 p → n π+
π-p → π0 n ; π0 p → K+ Λ• Strangeness exchange with
Λ-Σ couplingK- p → Σ- π+ ; (Σ- n Λ p)
π-p → Σ- K+ ; (Σ- n Λ p)
KEK E521
FINUDA
10B
Weak decay of hypernucleiWeak decay of hypernuclei• In free space...
Λ p + π- (63.9%, Q = 38 MeV) n + π0 (35.8%, Q = 41 MeV)• ΔI=1/2 rule holds - initial state: I=0, final state: I=1/2 or 3/2 if If = 1/2, branch is 2:1 3/2, 1:2 - this is a general rule in strangeness decay, but no one knows why• This decay (called mesonic decay) is suppressed in hypernuclei due to Pauli blocking for the final state nucleon.• Therefore, non-mesonic decay occurs in hypernuclei p + Λ p + n, n + Λ n + n, .... - Is the ΔI=1/2 still valid? We need to measure Γn and Γp
observables:observables:
tot 0 np nn 3N
tot 0 np nn 3N
non- mesonicdecay
mesonicdecay
Do we need quarks to describe non-mesonic decay or the OBE description is good?
Do we need quarks to describe non-mesonic decay or the OBE description is good?
Weak decay of hypernucleiWeak decay of hypernuclei
OPE0.05 0.2
OME (with heavy meson )Quark models …
10 0.5 1.5Γn / Γ p
Exp. Value0.5 2
asymmetry of the weak decay of polarized Hypernucleiasymmetry of the weak decay of polarized Hypernuclei
Experimental measurements Experimental measurements (past)(past)
Λ lifetime is almost constant for A > 10 non-mesonic decay dominate short range nature of non-mesonic decay
Past experiments only measured Γtot
5He (E462) : Γn/ Γp 0.45±0.11±0.03
systematic error : neutron efficiency(6%) + acceptance (3%)
Experimental measurements Experimental measurements (present)(present)
Modern experiments can measure
Γp and Γn at the same time:
KEK SKS FINUDA
En+Ep
En+En
First results are coming from KEK
To be compared with the old data: 0.93±0.55 (Szymanski et al. PRC 43 (1991)849)
Is the puzzle of Γn/ Γp solved? Stay tuned....
%)13(
%),34(
%),49()1020(00
LSKK
KKee
%)13(
%),34(
%),49()1020(00
LSKK
KKee
FINUDAFINUDA
FIFIsicasica NU NUclearecleare aa DADAΦΦNENE
The Φ provide a unique “K- beam” :
1. monochromatic low momentum (127 MeV/c)
2. trigger tagging K-stop event through the associate K+
3. no hadronic background
that can be stopped in thin targets to produce hypernuclei
K-stop ++ AAZ Z AA
ΛΛZZ ++ ππ --K-stop ++ AAZ Z AA
ΛΛZZ ++ ππ --
FINUDA scientific programFINUDA scientific program
• comparison with the 6Li; available data of poor quality7Li
6Li • source of Λ4He and Λ
5He ( Λ6Li unstable) to study of the decay of
light hypernuclei
HeH
pHHe
ddHe
nnHeHe
nnHeHe
pnHHe
44
34
4
46
35
35
• reference target for spectroscopy and weak decay studies• expected over 105 events in the excitation spectrum• search for weakly excited states, ≤ 10-5/Kstop
(present limit 10-4/Kstop)• weak decays: Γp (Λp →→ n p)
Γn (Λn →→ n n) Γpn (Λ n p →→ n n p) New
Γnn (Λ n n →→ n n n) New
Γπ- (Λ →→ p π-)
12C
• never studied before• measurement of the capture rate in medium A hypernuclei
27Al
• no measurements available with K- at rest, useful for weakdecay studies
• important to assess the capture rate for medium and heavyA hypernuclei
51V
Accelerator
Complex
DADAΦΦNE Complex NE Complex energy 510 MeV
Design Luminosity
5 1032 cm-2 s-1
X(rms) 2.11 mm
y(rms) 0.021 mm
z(rms) 35 mm
Bunch length 30 mm
Crossing angle 13 mrad
Frequency (max) 368.25 MHz
Bunch/ring Up to 120
Part./bunch 8.9 1010
Current/ring 5.2 A (max)
FINUDA
KLOE
Mechanical support (Mechanical support (clessidraclessidra))Straw tubes, LMDC, Vertex/targetStraw tubes, LMDC, Vertex/target
Magnet end-capMagnet end-cap
Magnet yokeMagnet yokeB=1.0 TB=1.0 T
TOFONE detectorTOFONE detector
FINUDA DetectorFINUDA Detector
FINUDA Interaction RegionFINUDA Interaction Region
Be 500μm
2mm Sci.
Vanadium target profile
Aluminum target profile
Carbon target profile
Lithium target profiles
200.00
44.10210.0044.10
26.0
1.7
0
0.0
3
4.7
0
0.0
3
244.00
244.00
27.10
3.7
0
2.6
02
.60
4.1
027.10
27.10
27.10
4.7
0
1.0
0
4.7
0
0.6
0
3.3
25
0.0
3
2.6
0
210.00
200.00
44.1044.10
0.6
25
2.6
0
210.00
200.00
1.0
0
44.1044.10
3.7
0.0
3
Targets
3 12C1 51V1 27Al2 6Li 1 7Li
FINUDA first runFINUDA first run : October 2003 – March 2004 : October 2003 – March 2004
pb-1
nb-1
Integrated luminositydelivered to FINUDA Integrated luminositydelivered to FINUDA
FINUDA
FINUDA
Daily integrated luminosity [nbarn-1]
Integrated luminosity [nbarn-1]
From 14-Oct- 2003 to 22-Mar-2004 DAΦNE delivered 250 pb-1to IP233 pb-1 machine tuning10 pb-1 FINUDA debugging190 pb-1 useful data taking
From 14-Oct- 2003 to 22-Mar-2004 DAΦNE delivered 250 pb-1to IP233 pb-1 machine tuning10 pb-1 FINUDA debugging190 pb-1 useful data taking
DAΦNE peak luminosiy (cm-2s-1)
30∙106 events recorded30∙106 events recorded
FINUDA Detector performancesFINUDA Detector performances
• S.C. Solenoid: B = 1.0 T field homogeneity within 2% •Interaction/Target region: selection of K+- K- pairs , production and detection of hypernuclei.
• External tracking device: trajectories and momenta of charged particles with high precision Δp/p = 0.3%.
• External scintillator barrel: trigger purposes and neutron detection (10% eff. , 8 MeV en. Resol.)• Helium gas chamber: reduction of particle multiple scattering.
• S.C. Solenoid: B = 1.0 T field homogeneity within 2% •Interaction/Target region: selection of K+- K- pairs , production and detection of hypernuclei.
• External tracking device: trajectories and momenta of charged particles with high precision Δp/p = 0.3%.
• External scintillator barrel: trigger purposes and neutron detection (10% eff. , 8 MeV en. Resol.)• Helium gas chamber: reduction of particle multiple scattering.
LMDC: (r,) 150 m; z 1% wire length
ST: (r,) 150 m; sz = 500 m
LMDC: (r,) 150 m; z 1% wire length
ST: (r,) 150 m; sz = 500 m
z = 30 m ; en. res. 20% FWHM z = 30 m ; en. res. 20% FWHM
VDET z resolution
Outer TOF time resolutionFINUDA momentum resolution p/p is:
0.3% in He 1.5% in air
FINUDA momentum resolution p/p is:0.3% in He 1.5% in air
Pid in VDET
Distribution of stopped KDistribution of stopped K--
Reconstructed K- stopping points – external layer: 8 targets– inner layer: microstrip ISIM modules
Φ
7Li
6Li
27Al 51V
12C12C
12C
6Li
ISIM 7
ISIM 8
ISIM 1
ISIM 2
K stopping in ISIM are about 10% of the total due to a boost (≈ 13 MeV) of the Φ in the x direction
K stopping in ISIM are about 10% of the total due to a boost (≈ 13 MeV) of the Φ in the x direction
e+
e-
ΦΦ12.5 mrad
Λ - hypClean hypernuclear structures can be seen in any target material
π- spectra coming form
different target materials
π- spectra coming form
different target materials
Experimental resultsExperimental results
π-spectrum contributions
Looking for protons from the Non-Mesonic Looking for protons from the Non-Mesonic ΛΛ decay decay
Particles coming from background processes can be easily
rejected requiring: dE/dx in the proton region; pπ- >240 MeV/c
all positive from
K- vertex 12C target 12C target
-1.8<BΛ<11.MeV
FINUDA future prospectsFINUDA future prospects
The Segmented Clover DetectorThe Segmented Clover Detector
BGO Comptonsuppression shield
Ge crystals
active collimator(scintillator)
Geometrical acceptancereduced to 72%
Geometrical acceptancereduced to 72%
@ L = 1033 cm-2 s-1 FINUDA can observe ~ 1.6 · 103 ev/h from YN g.s.@ L = 1033 cm-2 s-1 FINUDA can observe ~ 1.6 · 103 ev/h from YN g.s.
~ 1.87 · 103 ev/d~ 1.87 · 103 ev/d machine duty cycle: 75% spectrometer acceptance: 72% Ge acceptance: ~ 30% εGe: ~ 30%
machine duty cycle: 75% spectrometer acceptance: 72% Ge acceptance: ~ 30% εGe: ~ 30%
ConclusionsConclusions
Hypernuclear Physics has reached the status of a mature science
It helps in understanding BB weak and strong force allowing a detailed study into a SU(3) flavor symmetry environment
Some open problems still remain:
precise measurements of the spin-observables;
double Lambda hyp. binding force B;
Existence of neutron rich hypernuclei;
Survey on different targets of Γn /Γp.
Future activitiesFuture activities
• Jlab Hall A (HRS), Hall C (HKS)
• DAΦNE FINUDA → DAΦNE2 with spect.
• KEK-PS, BNL-AGS (E930,E963,E964) SKS, Hyperball2,..
• J-PARC
・ Ξ hyp. Spectroscoy using K-K+ reaction
・ ΛΛ hyp. Study using π- seq. decay
• GSI PANDA
ΛΛ hyp. Ge spectroscopy
Bhabha events eBhabha events e++ e e-- e e++ e e--
e+
e
e+ e invariant mass (GeV/c)
Ks +
e+ e e+ e
0 +
KKss ++ -- eventsevents
-
+
Ks
-
+
Hypernuclear typical eventHypernuclear typical event
+
-
K-
K+
+
-
Momentum resolutionMomentum resolution
K+ +
K+ + o (205 MeV/c)
K+ μ+ νμ , π+πo
From the width of the μ+ the spectrometer momentum resolution is evaluated.
(236 MeV/c)
Δp/p 0.4%Δp/p 0.4%After mechanicalalignment
Δp/p 0.9%
K- n -
p -
K- p+ -
K- p- +
- n -
K- (NN)- N - n -
K- n0 -
TOT
Background contributionsBackground contributions