Hypernuclear spectroscopy in Hall A 12 C, 16 O, 9 Be, H E-07-012 Experimental issues Results
Hypernuclear spectroscopy in Hall A 12 C, 16 O, 9 Be, H E-07-012 Experimental issues
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Transcript of Hypernuclear spectroscopy in Hall A 12 C, 16 O, 9 Be, H E-07-012 Experimental issues
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Hypernuclear spectroscopy in Hall A12C, 16O, 9Be, H E-07-012
Experimental issues
Perspectives (Hall A & Hall C collaboration)
High-Resolution Hypernuclear Spectroscopy ElectronScattering at Jlab
F. Garibaldi – Bormio 22-01-2013
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Hypernuclear investigation• Few-body aspects and YN, YY interaction
– Short range characteritics ofBB interaction– Short range nature of the LN interaction, no pion exchange:
meson picture or quark picture ?– Spin dependent interactions– Spin-orbit interaction, …….– LS mixing or the three-body interaction
• Mean field aspects of nuclear matter– A baryon deep inside a nucleus distinguishable as a baryon ? – Single particle potential – Medium effect ?– Tensor interaction in normal nuclei and hypernuclei– Probe quark de-confinement with strangeness probe
• Astrophysical aspect– Role of strangeness in compact stars– Hyperon-matter, SU(3) quark-matter, …– YN, YY interaction information
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HYPERNUCLEAR PHYSICS Hypernuclei are bound states of nucleons with a strange baryon (L)
Extension of physics on N-N interaction to system with S#0
Internal nuclear shell are not Pauli-blocked for hyperons
Spectroscopy
L-N interaction, mirror hypernuclei,CSB, L binding energy…
Ideal laboratory to study
This “impurity” can be used as a probe to study both the structure and properties of baryons in the nuclear medium and the structure of nuclei as baryoni many-body systems
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H.-J. Schulze, T. Rijken PHYSICAL REVIEW C 84, 035801 (2011)
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High resolution,
high yield, and systematic
study is essential
using electromagnetic probe
and
BNL 3 MeV
Improving energy
resolution
KEK336 2 MeV
~ 1.5 MeV
new aspects of hyernuclear structureproduction of mirror hypernuclei
energy resolution ~ 500 KeV
635 KeV635 KeV
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LN interaction(r)
Each of the 5 radial integral (V, D, SL , SN, T) can be phenomenologically determined from the low lying level structure of p-shell hypernuclei
V
SL
SN
D
T
✔ most of information is carried out by the spin dependent part ✔ doublet splitting determined by D, sL, T
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YN, YY Interactions and Hypernuclear Structure
Free YN, YY interactionConstructed from limited hyperon scattering data
(Meson exchange model: Nijmegen, Julich)
YN, YY effective interaction in finite nuclei(YN G potential)
Hypernuclear properties, spectroscopic informationfrom structure calculation (shell model, cluster model…)
Energy levels, Energy splitting, cross sectionsPolarizations, weak decay widths
high quality (high resolution & high statistics) spectroscopy plays a significant role
G-matrix calculation
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AK
Z
iH iJ
*
1
ELECTROproduction of hypernucleie + A -> e’ + K+ + H
in DWIA (incoming/outgoing particle momenta are ≥ 1 GeV)
- Jm(i) elementary hadron current in lab frame (frozen-nucleon approx)- virtual-photon wave function (one-photon approx, no Coulomb distortion)- K– distorted kaon w. f. (eikonal approx. with 1st order optical potential)-YAYH - target nucleus (hypernucleus) nonrelativistic wave functions (shell model - weak coupling model)
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good energy resolution
reasonable counting rates
forward angle
septum magnets
do not degrade HRS
minimize beam energy instability “background free” spectrum unambiguous K identification
RICH detectorHigh Pk/high Ein (Kaon survival)
1. DEbeam/E : 2.5 x 10-5 2. DP/P : ~ 10-4
3. Straggling, energy loss…
~ 600 keV
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JLAB Hall A Experiment E94-107
16O(e,e’K+)16LN
12C(e,e’K+)12L
Be(e,e’K+)9LLi
H(e,e’K+)LS0
Ebeam = 4.016, 3.777, 3.656 GeVPe= 1.80, 1.57, 1.44 GeV/c Pk= 1.96 GeV/c
qe = qK = 6°W 2.2 GeV Q2 ~ 0.07 (GeV/c)2
Beam current : <100 A Target thickness : ~100 mg/cm2
Counting Rates ~ 0.1 – 10 counts/peak/hour
A.Acha, H.Breuer, C.C.Chang, E.Cisbani, F.Cusanno, C.J.DeJager, R. De Leo, R.Feuerbach, S.Frullani, F.Garibaldi*, D.Higinbotham, M.Iodice, L.Lagamba, J.LeRose, P.Markowitz, S.Marrone, R.Michaels, Y.Qiang, B.Reitz, G.M.Urciuoli, B.Wojtsekhowski, and the Hall A Collaborationand Theorists: Petr Bydzovsky, John Millener, Miloslav Sotona
E94107 COLLABORATION
E-98-108. Electroproduction of Kaons up to Q2=3(GeV/c)2 (P. Markowitz, M. Iodice, S. Frullani, G. Chang spokespersons)
E-07-012. The angular dependence of 16O(e,e’K+)16N and H(e,e’K+)L (F. Garibaldi, M.Iodice, J. LeRose, P. Markowitz spokespersons) (run : April-May 2012)
Kaon collaboration
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hadron arm
septum magnets
RICH Detector
electron arm
aerogel first generation
aerogel second generation
To be added to do the experiment
Hall A deector setup
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Kaon Identification through Aerogels
The PID Challenge Very forward angle ---> high background of p and p- TOF and 2 aerogel in not sufficient for unambiguous K identification !
AERO1 n=1.015
AERO2 n=1.055
pkp
ph = 1.7 : 2.5 GeV/c
Protons = A1•A2
Pions = A1•A2Kaons = A1•A2
pkAll events
p
k
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RICH – PID – Effect of ‘Kaon selection
p P
K
Coincidence Time selecting kaons on Aerogels and on RICH
AERO K AERO K && RICH K
Pion rejection factor ~
1000
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12C(e,e’K)12BL M.Iodice et al., Phys. Rev. Lett. E052501, 99 (2007)
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Be windows H2O “foil”
H2O “foil”
The WATERFALL target: reactions on 16O and 1H nuclei
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1H (e,e’K)L
16O(e,e’K)16NL
1H (e,e’K)LS
L
SEnergy Calibration Run
Results on the WATERFALL target - 16O and 1H
Water thickness from elastic cross section on H Precise determination of the particle momenta and beam energy using the Lambda and Sigma peak reconstruction (energy scale
calibration)
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Fit 4 regions with 4 Voigt functions2
/ndf = 1.19
0.0/13.760.16
Results on 16O target – Hypernuclear Spectrum of 16NL
Theoretical model based on :SLA p(e,e’K+)L (elementary
process)LN interaction fixed parameters
from KEK and BNL 16LO spectra
• Four peaks reproduced by theory
• The fourth peak (L in p state) position disagrees with theory. This might be an
indication of a large spin-orbit term SL
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Fit 4 regions with 4 Voigt functions2
/ndf = 1.19
0.0/13.760.16
Binding Energy BL=13.76±0.16 MeV
Measured for the first time with this level of accuracy (ambiguous interpretation
from emulsion data; interaction involving L
production on n more difficult to normalize
Within errors, the binding energy and the excited levels of the mirror hypernuclei 16OL and 16NL (this experiment) are in agreement, giving no strong evidence of charge-dependent effects
Results on 16O target – Hypernuclear Spectrum of 16NL
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Radiative corrected experimental excitation energy vs theoretical data (thin curve). Thick curve: three gaussian fits of the radiative corrected data
Experimental excitation energy vs Monte Carlo Data (red curve) and vs Monte Carlo data with radiative Effects “turned off” (blue curve)
Radiative corrections do not depend on the hypothesis on the peak structure producing the experimental data
9Be(e,e’K)9LiL
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10/13/09
p(e,e'K+)L on WaterfallProduction run
Expected data from E07-012, study the angular dependence of
p(e,e’K)L and 16O(e,e’K)16NL at low Q2
Results on H target – The p(e,e’K)L Cross Section
p(e,e'K+)L on LH2 Cryo Target
Calibration run
None of the models is able to describe the data over the entire range
New data is electroproduction – could
longitudinal amplitudes dominate?
W2.2 GeV
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How?
The interpretation of the hypernuclear spectra is difficult because of the lack of relevant information about the elementary process.
Hall A experimental setup (septum magnets, waterfall target, excellent energy resolution AND Particle Identification ) give unique opportunity to measure, simultaneously, hypernuclear process AND elementary process
In this kinematical region models for the K+- L electromagnetic production on protons differ drastically
The ratio of the hypernuclear and elementary cross section measured at the same kinematics is almost model independent at very forward kaon scattering angles
Why?
The ratio of the hypernuclear and elementary cross section doesn’t depend strongly on the electroproducion model and contains direct information on hypercnulear structure and production mechanism
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The results differ not only in the magnitude of the X-section (a factor 10) but also in the angular dependence (given by a different spin structure of the elementary amplitudes for smaller energy (1.3 GeV) where the differences are smaller than at 2 GeV
the information from the hypernucleus production, when the cross sections for productionof various states are measured, is reacher than the ordinary elementary cross section
Measuring the angular dependence of the hypernuclear cross section, we may discriminate among models for the elementary process.
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Future mass spectroscopy
Hypernuclear spectroscopy prospectives at Jlab
Collaboration meeting - F. Garibaldi – Jlab 13 December 2011
Decay Pion Spectroscopy to Study L-Hypernuclei
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- Put HKS behind a Hall A style septum magnet in
Hall A - Enhance setup in Hall A over HRS2 + Septum
-No compromise of low backgrounds - Independently characterize the optics of each arm using elastic scattering - The HKS+Septum arm would replace present Hall A Kaon arm (Septum+HRS)
- Keep the ability to use waterfall target or cryotargets
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SL, p-1 states are weakly populated - small overlap of the corresponding single particle wave functions of proton and lasmbda. For L in higher s.p. states overlap as well as cross sections increases being of the order of ~ 1 nb.
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208
208
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208
208
208
We have to evaluate pion and proton background and fine tune it with data from (e,e’p)Pb
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PR12-10-001 - Study of Light - Hypernuclei by Spectroscopy of Two Body Weak Decay Pions
Fragmentation of Hypernuclei And Mesonic Decay inside Nucleus
Free: L p + p -
2-B: ALZ A(Z + 1) + p - (and fragmentation of hypernuclei)
Thus high yield and unique decay feature allow high precision measurement of decay pion spectroscopy from which variety of physics may be extracted
- High yield of hypernuclei (bound or unbound in continuum) makes high yield of hyper fragments, i.e. light hypernuclei which stop primarily in thin target foil- Weak 2 body mesonic decay at rest uniquely connects the decay pion momentum to the well known structure of the decay nucleus, BL and spin-parity of the ground state of
hyperfragment
- High momentum transfer in the primary production sends most of the background particles forward, thus pion momentum spectrum is expected to be clean with minor 3-
boby decay pions.
(p - 0.1)
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ConclusionsE94-107: “systematic” study of p shell light
hypernuclei
The experiment required important modifications on the Hall A apparatus.New experimental equipment showed excellent performance.
Data on 12C show new information. For the first time significant strength and resolution on the core excited part of the spectrum
Prediction of the DWIA shell model calculations agree well with the spectra of 12BL and 16NL for L in s-state. In the pL
region more elaborate calculations are needed to fully understand the data.
Interesting results from 9Be, interpretation underway Elementary reaction needs further studies More to be done in 12 GeV era (few body, Ca-40,Ca-
48,Pb…)
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Back up slides
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PAVI 09
Lead Target
Liquid Helium Coolant
Pb
C
208
12
Diamond Backing:
• High Thermal Conductivity• Negligible Systematics
Beam, rastered 4 x 4 mm
beam
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Diaond LEAD
Lead / Diaond Taret
• Three bas• Lead 0.5 sandwihed b
diaond 0.15 • Liquid He oolin 30 Watts
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Perforane of Lead / Diaond Tarets durin PREX
Last 4 days at 70 uA
Targets with thin diamond backing (4.5 % background) degraded fastest.
Thick diamond (8%) ran well and did not melt at 70 uA.
eltedelted
NOT elted
PREX-II plan: Run with 10 targets.
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Coents on Pb/D Taret
If perfet theral ontat to diaond Iax > 100 uA. If no ontat Iax 10 uA
Soe have suested a spinnin taret.Miht work for soe expt’s but
• needs R&D• a ause noise relevant to parit expt’s
Ideas bein onsidered thouh no ation et: • sputter lead onto diaond ahieve better ontat• tests of new desins at Idaho State Universit
eletron bea failit