Study of Light Hypernuclei Study of Light Hypernuclei by Pionic Decay at JLABby Pionic Decay at JLAB
Liguang TangLiguang Tang
Other spokespersons:Other spokespersons:A. Margaryan, L. Yuan, S.N. Nakamura, J. ReinholdA. Margaryan, L. Yuan, S.N. Nakamura, J. Reinhold
Collaboration:Collaboration:From both Hall C and A hypernuclear programsFrom both Hall C and A hypernuclear programs
JLAB PAC 33, January 14-18, 2008JLAB PAC 33, January 14-18, 2008
IntroductionIntroductionNuclei Baryon-Baryon Interaction Neutron Stars
D.H.
D.H.D.H.
S.H.S.H.N.R.p
S.H.S.H.N.R.N.R.n
(uds)
(uds)
P(uud)
n(udd) The single and double The single and double
hypernuclei are the hypernuclei are the main sources of the main sources of the strange sector of strange sector of baryon-baryon baryon-baryon interactioninteraction
S=-1
S=-2
S=-0
Discovery of the first hypernucleus by pionic decay in Discovery of the first hypernucleus by pionic decay in emulsion produced by Cosmic Rays. Marian Danysz and emulsion produced by Cosmic Rays. Marian Danysz and
Jerzy Pniewski, 1952Jerzy Pniewski, 1952
• p + - (64%); n + 0 (36%)
• Remain effective even at medium A
Access rich information about Access rich information about hypernuclear and nuclear physicshypernuclear and nuclear physics
Used exclusively to determine the Used exclusively to determine the binding energy of light (A≤15) binding energy of light (A≤15) hypernuclei in emulsionhypernuclei in emulsion
Precision: ~50keVPrecision: ~50keV Resolution: ~0.5 – 1.0 MeVResolution: ~0.5 – 1.0 MeV Problems: Problems:
- Poor statistics- Poor statistics
- Calibrations- Calibrations
- Cannot resolve pure 2-body decay- Cannot resolve pure 2-body decay Was not interested in the past ~20 Was not interested in the past ~20
years – years – low energy and low yieldlow energy and low yield
New Opportunity at JLABNew Opportunity at JLAB
Combination the CEBAF beam and Combination the CEBAF beam and the HKS systemthe HKS system
High precision and high yieldHigh precision and high yield
Program features:Program features:
• Energy resolution: Energy resolution: ~130 keV FWHM~130 keV FWHM
• BB precision: precision: ~10 keV~10 keV
• Simultaneous lifetime measurement Simultaneous lifetime measurement (timing resolution ≤80ps)(timing resolution ≤80ps)
Wide range of physicsWide range of physics
Directly Produced Hypernuclei - Directly Produced Hypernuclei - ExampleExample
p
e’
e
12C
K+
12B
12Cg.s. -
Mesonic two body decay
1- 0.02- ~150 keV
Ground state doublet of 12
B
B and
Indirectly Produced Hypernuclei – Indirectly Produced Hypernuclei – ExampleExampleFragmentation ProcessFragmentation Process
p
e’
e
12C
12B
*
K+
4He
-
Mesonic two body decay (~10-10s)
Access to variety of light and exotic
hypernuclei, some of which cannot be
produced or measured precisely
by other means
4H
Fragmentation (<10-16s)
Physics Objectives – YN InteractionsPhysics Objectives – YN Interactions Emulsion data of light hypernuclei (primarily the ground Emulsion data of light hypernuclei (primarily the ground
states) were used to check theoretical models on YN states) were used to check theoretical models on YN interaction in the past 40 some years.interaction in the past 40 some years.
Problem of inconsistency and model of choice existProblem of inconsistency and model of choice exist
Recent Recent -spectroscopy program has been successful for -spectroscopy program has been successful for spin dependent interactions but unable to measure spin dependent interactions but unable to measure BB
Recent successful mass spectroscopy programs cannot Recent successful mass spectroscopy programs cannot reach a precision on reach a precision on BB exceeding emulsion dataexceeding emulsion data
YN B (3H) B (4
H) B (4H* ) B (4
He) B (4He* ) B (5
He)
SC97d(S) 0.01 1.67 1.2 1.62 1.17 3.17
SC97e(S) 0.10 2.06 0.92 2.02 0.90 2.75SC97f(S) 0.18 2.16 0.63 2.11 0.62 2.10
SC89(S) 0.37 2.55 Unbound 2.47 Unbound 0.35
Experiment 0.13 ± 0.05 2.04 ± 0.04 1.00 ± 0.04 2.39 ± 0.03 1.24 ± 0.04 3.12± 0.02
The wealth of information coming from this poor The wealth of information coming from this poor statistics emulsion experiment is solely attributable statistics emulsion experiment is solely attributable to the technique's inherent good energy resolution, to the technique's inherent good energy resolution, ~50 keV~50 keV in this instance, and forcefully emphasizes in this instance, and forcefully emphasizes the need to strive for comparable energy resolution the need to strive for comparable energy resolution in counter experiments.in counter experiments.
- - D. Davis, 1992D. Davis, 1992
As it turns out, binding energies of light hypernuclei As it turns out, binding energies of light hypernuclei are highly correlated from calibrations to are highly correlated from calibrations to 1212
C for C for example, and most likely incorrect. example, and most likely incorrect. - D. - D. Davis, HYP2006Davis, HYP2006
Replace emulsion data with a new set of Replace emulsion data with a new set of data that has a factor of 2-5 times better data that has a factor of 2-5 times better precision on Bprecision on B to check current and future to check current and future theories with stringent limitstheories with stringent limits
Separate small ground state doubletsSeparate small ground state doublets
Study charge symmetry breaking in YN Study charge symmetry breaking in YN interaction, such as interaction, such as BB((44
HHg.s.g.s.) - B) - B((44HeHeg.s.g.s.))
YN Interactions – YN Interactions – cont.cont.
Search for and measure precisely the Search for and measure precisely the BB of the of the exotic hypernuclei is another effective way for exotic hypernuclei is another effective way for exotic nuclear physicsexotic nuclear physics
Many hypernuclei with unstable nuclear core Many hypernuclei with unstable nuclear core exist, e.g. exist, e.g. 66
HeHe, , 77BeBe, , 88
HeHe, , 99Be. Be. Other exotic Other exotic
hypernculei may exist, e.g. hypernculei may exist, e.g. 66H, H, 77
HH, , 88HH, , 1010
HeHe, , and and 1111
LiLi through fragmentation processthrough fragmentation process
Search for Highly Exotic HypernucleiSearch for Highly Exotic Hypernuclei
Bound hypernucleu
s
Search for light Search for light hypernuclei toward hypernuclei toward nucleon drip-lines: nucleon drip-lines: hypernuclei with hypernuclei with extreme isospinsextreme isospins
Other programs:Other programs:Heavy ion collisionHeavy ion collision
JINR, HypHI JINR, HypHI
This program – high This program – high precision on Bprecision on B
Hypernuclei at:
* -stability line* Neutron rich* Nucleon drip-lines
Pion decays offer insights into the hypernuclear Pion decays offer insights into the hypernuclear and nuclear structure, and the momentum and nuclear structure, and the momentum dependence of the single particle wave functionsdependence of the single particle wave functions
Impurity Nuclear Physics Impurity Nuclear Physics Hypernuclear and nuclear structureHypernuclear and nuclear structure
Nucleus at g.s.
-
Hypernucleus w/ hyperfine g.s. doublet
E < 100 keV
Decay pion can be used to determine the spin ordering of the doublet
Hypernucleus at g.s.
Nucleus w/ hyperfine g.s. doublet
E < 100 keV
Example: Example: 77Li w/ g.s. doublet 1/2Li w/ g.s. doublet 1/2++ & 3/2 & 3/2++
Impurity Nuclear Physics – Impurity Nuclear Physics – cont.cont. Probing nuclear structure with Probing nuclear structure with
Impurity Nuclear Physics – Impurity Nuclear Physics – cont.cont. Probing nuclear structure with Probing nuclear structure with
Example: Example: 1010B w/ g.s. doublet 1B w/ g.s. doublet 1-- & 2 & 2--
Spin order is not knownSpin order is not known
transition (transition (22-- 1 1--) was not found) was not found
Success competition by weak mesonic decaySuccess competition by weak mesonic decay
Assumed order could be wrongAssumed order could be wrong
Decay pion may provide clearificationDecay pion may provide clearification
1010Be Be may be the candidate at JLABmay be the candidate at JLAB
Impurity Nuclear Physics Impurity Nuclear Physics Role and effect of Role and effect of in Nucler Medium in Nucler Medium
E2
Precise Precise BB allows separation of those low lying states which allows separation of those low lying states which have sufficient long lifetime (i.e. have sufficient long lifetime (i.e. decay competes with weak decay competes with weak decay) decay)
Lifetime of these separable states allows to extract transition Lifetime of these separable states allows to extract transition probabilities probabilities B(E2)B(E2) and B(M1) which provide information about and B(M1) which provide information about the medium effect to baryon or the medium effect to baryon or to the core medium to the core medium
5/2+
3/2+
1/2+
E20 (MeV)
~1 .7
5/2+ and 3/2+ states are from unbound 2+ state of 6He core
7He
-
7Li
E2
1/2+
5/2+7/2+
0 (MeV)~0 .26
~1 .48
11B
-
11C
Tagged-Weak Pi-Method of B(E2) and Tagged-Weak Pi-Method of B(E2) and B(M1) Measurement B(M1) Measurement
By measuring both of PBweak(t) and PAweak(t) and fitting them together to the
equations above, , and m can be determined.λWA λW
B
If states can be separated and statistics is sufficient to measure lifetimes, then
Technique & Exp. LayoutTechnique & Exp. Layout
Pre-Chicaned Electron Beam
Hall C Z-axis
To Hall Dump To low power local dump
dump
Schematic Top View of New Hypernuclear
Decay Tagging System at Jlab
Standard Splitter and Standard Splitter and HKS for KHKS for K++
Enge & target moved Enge & target moved upstream for decay upstream for decay pionspions
Tilted TGT (25mg/cmTilted TGT (25mg/cm22) ) Eff. TGT (50mg/cmEff. TGT (50mg/cm22))
Standard pre-chicane Standard pre-chicane beam line (E05-115)beam line (E05-115)
Local dump for photonsLocal dump for photons Similar luminosity as Similar luminosity as
E05-115 (HKS/HES)E05-115 (HKS/HES)
Need calibration for Need calibration for the absolute Hthe absolute HS S
central momentum central momentum
Configuration Enge Split-Pole (or HES) spectrometer and detector package
Central momentum 115 MeV/c
Momentum acceptance ± 40%
Momentum resolution (r.m.s.) 10-4 without multiple scattering
Momentum resolution (r.m.s.) 4.9 10-4 with multiple scattering
Dispersion 1.28 cm/%
Time-zero precision < 100 ps (~80 ps)
Pion detection angle ~60 degree relative to the incident beam
Flight path length 309 cm
- survival rate ~ 60%
Solid angle ~20 msr
Total efficiency of the detector package
~80%
Parameters of the Parameters of the HHSS spectrometer spectrometer
Example of Possible G.S. of Light Hypernuclei Example of Possible G.S. of Light Hypernuclei from from 1212C TargetC Target
4H
8Li
12B
3H
7Li
11B
5He
8Be
9Be
Background:• ~97.5% QF decay• ~2.5% (K+ & -) accidentals
G.S. only (doublet structures are not shown)G.S. only (doublet structures are not shown) Estimated based on emulsion data thus may Estimated based on emulsion data thus may
under-estimated for some of the hypernucleiunder-estimated for some of the hypernuclei Additional hypernuclei may appear Additional hypernuclei may appear
Targets: Targets: 1212C and C and 77Li (Optimized combination)Li (Optimized combination)
• 1212C – Heaviest in p-shell; reliable yield rates on variety of light C – Heaviest in p-shell; reliable yield rates on variety of light hypernuclei but not too crowdedhypernuclei but not too crowded
• 77Li – Best chance for the lightest and highly exotic Li – Best chance for the lightest and highly exotic hypernuclei, such as hypernuclei, such as 66
HH
Beam energy: 1.8 – 2.2 GeVBeam energy: 1.8 – 2.2 GeV
Beam current and acq. timeBeam current and acq. time
• 1212C, 60C, 60A (100 Max.), 20 daysA (100 Max.), 20 days
• ~1000 counts for ~1000 counts for 44H (physics w/ moderate yield)H (physics w/ moderate yield)
• ~6000 counts for ~6000 counts for 55He (physics and calibration)He (physics and calibration)
• 77Li, 30Li, 30A (50 Max.), 20 days A (50 Max.), 20 days
Primary: Primary: 77He, He, 66
He, He, 55He; He; Questionable:Questionable: 44
He, He, 66H, H, 55
H, H, 44HH
Trigger rate: ~ few hundred HzTrigger rate: ~ few hundred Hz
Beam Parameters and Beam TimeBeam Parameters and Beam Time
SummarySummary CEBAF beam and HKS provide unique CEBAF beam and HKS provide unique
opportunity for a new counter type opportunity for a new counter type high precision decay pion program – high precision decay pion program – Producing data that replaces emulsion Producing data that replaces emulsion data in the role of checking theoriesdata in the role of checking theories
It can study a wide range of physics It can study a wide range of physics that either not accessible by other that either not accessible by other means or complementary to other means or complementary to other programsprograms
International Hypernuclear NetworkInternational Hypernuclear Network
PANDA at FAIR• 2012~• Anti-proton beam• Double -hypernuclei• -ray spectroscopy
MAMI C• 2007~• Electro-production• Single -hypernuclei• -wavefunction
JLab• 2000~• Electro-production• Single -hypernuclei• -wavefunction
FINUDA at DANE• e+e- collider• Stopped-K- reaction• Single -hypernuclei• -ray spectroscopy (2012~)
J-PARC• 2009~• Intense K- beam• Single and double -hypernuclei• -ray spectroscopy for single
HypHI at GSI/FAIR• Heavy ion beams• Single -hypernuclei at extreme isospins• Magnetic moments
SPHERE at JINR• Heavy ion beams• Single -hypernuclei
JLab, HπS• Electro-production• Single -hypernuclei at normal and extreme isospins• Binding energies•π - decay spectroscopy•Impurity nuclear physics
Basic map from Saito, HYP06
Introduction – Introduction – cont.cont.
ExampleExample
H. Outa et al., “Lifetime measurement of 4H hypernucleus”, INS-Rep.-914 (1992)
Decay Decay -- is used even in modern studiesis used even in modern studies
In the last 20 years or so, mesonic decay has not In the last 20 years or so, mesonic decay has not been really interested in study of the been really interested in study of the hypernuclear/nuclear structure, because of its low hypernuclear/nuclear structure, because of its low momentum and the difficulty to reach high momentum and the difficulty to reach high precision with unavoidable thick targets using precision with unavoidable thick targets using msonic beamsmsonic beams
Emulsion: cannot resolve two body decay Emulsion: cannot resolve two body decay and typical resolution is 0.5 – 1.0 MeVand typical resolution is 0.5 – 1.0 MeV
Counter type: resolution is 1.0 – 2.0 MeVCounter type: resolution is 1.0 – 2.0 MeV
Time delayed
The proposed project capable to provide precise binding values of known hypernuclei and have a
great potential to extend this landscape
Exotic HypernucleiExotic Hypernuclei
Different decay channels of excited 7He* hypernucleus (Majling,
2006).