Spectroscopic Investigation of L hypernuclei in the wide mass region using the e,eK reaction Extensi

1
Spectroscopic Investigation of L hypernuclei in
the wide mass region using the (e,eK)
reaction(Extension request of the currently
running E01-011 experiment)
P05-115

• Osamu Hashimoto
• Department of Physics, Tohoku University
• representing the HKS collaboration

JLab PAC28 August 24, 2005
2
Hyper Collaboration

• O. Hashimoto (Spokesperson), S.N. Nakamura
  (Spokesperson), Y. Fujii, M. Kaneta, M. Sumihama,
  H. Tamura,K. Maeda, H. Kanda, Y. Okayasu, K.
  Tsukada, A. Matsumura, K.Nonaka, D. Kawama, N.
  Maruyama, Y. Miyagi (Tohoku U)
• S. Kato (Yamagata U)
• T. Takahashi, Y. Sato, H. Noumi (KEK)
• T. Motoba (Osaka EC)
• L. Tang (Spokesperson), O.K. Baker, M. Christy,
  L. Cole, P. Gueye, C. Keppel, L. Yuan (Hampton U)
• J. Reinhold (Spokesperson), P. Markowitz, B.
  Beckford, S. Gullon, C. Vega (FlU)
• Ed.V. Hungerford, K. Lan, N. Elhayari, N.
  Klantrains, Y. Li,S. Radeniya (Houston)
• R. Carlini, R. Ent, H. Fenker, D. Mack, G. Smith,
  W. Vulcan, S.A. Wood, C. Yan (JLab)
• N. Simicevic, S. Wells (Louisiana Tech)
• L. Gan (North Carolina, Wilmington)
• A. Ahmidouch, S. Danagoulian, A. Gasparian (North
  Carolina AT)
• D. Dehnhard (Minnesota)
• M. Elaasar(New Orleans)
• R. Asaturyan, H. Mkrtchyan, A. Margaryan, S.
  Stepanyan, V. Tadevosyan (Yerevan)
• D. Androic, T. Petkovic, M. Planinic, M. Furic
  (Zagreb)
• T. Angelescu (Bucharest)
• V.P. Likhachev (Sao Paulo)
• M. Ahmed (Duke)

3
Outline of the talk

• Significance of hypernuclear spectroscopy and
  goals of the proposed experiment
• (e,eK) spectroscopy and the current status
• of E01-011 experiment
• 3. Setup conditions of the proposed
  experiment
• 4. Summary with prospect

4
Significance of hypernuclear spectroscopyandthe
goals of the proposed experiment
5
3D Nuclear Chart with the strangeness degree of
freedom
6
Single-particle nature of L hypernuclei
Singly charged atom
Core Nucleus L
A L hyperon in the mean field

• New degree of freedom ? free from Pauli blocking
• Deeply bound nuclear states
• Baryon structure in nuclear medium
• Unique structure of hadronic many-body system
• Nucleus with a new quantum number
• Core excited states
• Glue role of a L hyperon
• LN interaction
• Unified view of baryon-baryon interaction in
  SU(3)
• Central and spin-dependent LN interaction

Core excitation,
7
Nucleon single particle orbits
8
Single-particle nature of L hypernuclei
Singly charged atom
Core Nucleus L
A L hyperon in the mean field

• New degree of freedom ? free from Pauli blocking
• Deeply bound nuclear states
• Baryon structure in nuclear medium
• Unique structure of hadronic many-body system
• Nucleus with a new quantum number
• Core excited states
• Glue role of a L hyperon
• LN interaction
• Unified view of baryon-baryon interaction in
  SU(3)
• Central and spin-dependent LN interaction

Core excitation,
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YN, YY Interactions and Hypernuclear Structure
Free YN, YY interaction Constructed from limited
hyperon scattering data (Meson exchange model
Nijmegen, Julich)
G-matrix calculation
YN, YY effective interaction in finite nuclei (YN
G potential)
Hypernuclear properties, spectroscopic
information from structure calculation (shell
model, cluster model)
Energy levels, Energy splitting, cross
sections Polarizations, weak decay widths
high quality (high resolution high statistics)
spectroscopy plays a significant role
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Hypernuclear Hamiltonian
Weaker compared with NN
H HN(Core) tL SVLNeffective
HN(Core) Core nucleus ( Usually hole
states)
tL L kinetic energy
VLN effective LN interaction
( Nijmegen, Julich ... )
vLN weak compared to vNN
Direct comparison of spectroscopic data with
structure calculation
Biding energy, energy splitting, cross section, .
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Population of excited L hypernuclear statesand L
hypernuclear spectroscopy
L-particle nucleon-hole states
neutron or proton
L
BL
25 MeV
p
Narrow widths lt a few 100 keV
p
Reaction spectroscopy
Bp
n
Bn
207LTl
g
207LPb
208LPb
Gamma-ray spectroscopy
Weak decay nonmesonic mesonic
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L Hypernuclear production
(K-,p-)
Inflight(K-,p)
BNL, CERN
mb/sr
(p,K)
Stopped (K-,p)
KEK, BNL
Hypernuclear Cross section
mb/sr
(p,K)
JLab
(e,eK) (g,K)
(p,K)
nb/sr
(p,K)
0
500
1000
Momentum transfer (MeV/c)
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Hypernuclei in the wide mass range
-- toward strange matter --

• Short range nature of the LN interaction no
  pion exchange
• meson picture or quark picture ?

• Light hypernuclei (Alt20)
• Fine structure
• Baryon-baryon interaction in SU(3)
• LS coupling in large isospin hypernuclei
• Cluster structure
• Heavy hypernuclei (Agt50)
• Single-particle potential
• Distinguishability of a L hyperon
• U0(r), mL(r), VLNN, ...
• Neutron star (A 1057 )
• Hyperonization ? Softening of EOS ?
• Superfluidity

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12C(p,K) 12LC spectraby the SKS spectrometer
at KEK 12 GeV PS
BNL 3 MeV(FWHM)
SKS
SKS
KEK E369 1.45 MeV(FWHM)
Hypernuclear spectroscopy established
KEK336 2 MeV(FWHM)
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L hyperon in heavier nuclei

• L Single particle states
• -gt L-nuclear potential

Hotchi et al., PRC 64 (2001) 044302
Y
La
Pb
Si
Single-particle orbits in nucleus

• Skyrme HF (Yamamoto)
• DDRH (Lanske)
• Quark-meson coupling
• (Saito, Thomas)

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Goals of the proposed experiment

• 51V(e,eK)51LTi reaction
• Next heavier L hypernuclei from 28LAl
• L binding energies for s,p,d orbits determined
• L hypernuclear structure investigated
• ls splitting in l2,3 orbits to b derived If
  sizable
• 89Y(e,eK)89LSr reaction
• Exploratory run to examine feasibility of
  (e,eK)
• spectroscopy in heavier hypernuclei
• 6,7Li(e,eK)6,7LHe and 10,11B(e,eK)10,11LBe
• Precision hypernuclear structure in neutron-rich
  L hypernuclei
• LS coupling effect changing isospins with
  neutron number

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(e,eK) spectroscopy andE01-011 status
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The (e,eK) reaction for hypernuclear
spectroscopy

• Proton to L
• ? Neutron rich L hypernuclei
• Large angular momentum transfer
• Spin-flip amplitude

Higher energy resolution
A few 100 keV achievable
First (e,eK) spectroscopy ? E89-009 (SOS ENGE)
Only at JLab
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What limited the E89-009 experiment ?

• Energy resolution
• The kaon arm limited hypernuclear mass resolution
  
• Hypernuclear yield rates
• High accidental background rate due to Brems
  electrons
• Solid angle of the kaon arm (SOS) limited
  detection efficiency

(1) A high-resolution large-solid-angle kaon
spectrometer (HKS) (2) New experimental
configuration Tilt method
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Tilt method and optimization of the tilt angle
Singles rate of the e-arm 200 MHz ? lt a few
MHz even with 5? Target thickness and 50? Beam
intensity
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The HKS spectrometer system for E01-011
High resolution Kaon Spectrometer (HKS)
Maximum momentum 1.2 GeV/c Dispersion
4.7 cm/ Momentum resolution 2 x
10-4(FWHM) Solid angle 30
msr w/o splitter
16 msr w splitter Momentum acceptance
12.5
Tilt method for the electron arm
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E01-011 setup in Hall C
Tilted ENGE
HKS
ENGE
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Expected singles rates
Ie 30 mA, 100 mg/cm2
Measured values at E89-009 Ie 0.66 mA, 22
mg/cm2
Greater hadron rates
High rejection efficiencies against pions and
protons are required
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Yield comparison of E01-011 and E89-009
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Beam currents, singles rates trigger rates
E01-011
Tilt method proved to work !!
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Kaon PID E01-011
HKS singles events
HKS-ENGE coincidence events
btof btrack

• coincidence time (ns)

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p(e,eK)L/S0 reactions
E89-009 experiment
E01-011 experiment
Improved!
12C(e,eK) quasi-free
Accidental
210 Lambdas
1390 Lambdas
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12LB spectrum ( 12C target )
E01-011
E89-009
lt 1MeV (FWHM)
1 month
ds/dW nb/sr/0.3 MeV
Preliminary
Hypernuclear excitation (300 keV/bin)
-BL(MeV)
12LBg.s 600 counts (20 /hr) lt1 MeV (FWHM) ?
400 keV
vs. E89-009 Hall C 165 counts with 750
keV (0.9 /hr) E94-107 Hall A 600
counts with 800 keV (3 /hr)
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Proposed experimental setup conditions
Basically similar to those of E01-011 except for
the new High-resolution electron spectrometer and
some improvement based on the E01-011 experience
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HKS-HES hypernuclear spectrometer system
New Splitter
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High resolution electron spectrometer (HES)---
widen acceptable beam energy window
---compatible with 6, 12 GeV operation
( ENGE is used as an electron spectrometer when
the beam energy is 1.8 GeV )
Beam energy and spectrometer conditions
HKS
Eg dependence
6 GeV 12 GeV
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Acceptable energy windows of HKS systemwith ENGE
or HES
ENGE
HES
Acceptable Central Energy (GeV)
0.3
1
0.4
0.6
0.8
Ee (GeV)
2.5
1.8
1.9
2.0
2.2
2.4
2.1
Ee at Hall (GeV)
Etop2pass (GeV)
4.4
4.55
5.0
6.0
Etop1pass (GeV)
9.45
10.3
10.8
12.0
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Basic specification of HES

• Configuration DQQD
• horizontal 50 degree bend
• Central momentum 0.6 1.0 GeV/c
• Momentum acceptance gt 200 MeV/c
• Momentum resolution 2 x 10-4
• Electron detection angle horizontal 0 degrees
• vertical lt 10 degrees
• Solid angle gt 10 msr
• Maximum D magnetic field 1.6 T

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Splitter, HKS, HES geometry
1.0 GeV/c
HES
HKS
0.6 GeV/c
New Splitter
Splitter TOSCA calculation
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HES mechanical design
For 600 MeV/c
For 1000 MeV/c
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Expected Energy Resolution
lt400 keV(FWHM) expected
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Expected hypernuclear production ratesin the
(e,eK) reaction
Calculated hypernuclear cross sections
Hypernuclear production rates
(Target thickness 100 mg/cm2)
Motoba, Sotona
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51LTi and 51LV spectra
KEK SKS data
Simulation
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5022Ti and 5123V
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Evolution of (e,eK) spectroscopy
2000
2004-2005
2005
200?
( ) expected ENGE spectrometer to be used for
a 1.8 GeV beam
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Roadmap of (e,eK) hypernuclear spectroscopy
HKS as a strangeness tagger HES as a virtual
photon tagger

• Light L hypernuclear spectroscopy
• LN interaction, LS coupling
• p shell hypernuclei 6,7Li, 9Be,10,11B, 12C,
  13C,16O targets
• s shell hypernuclei 3,4He targets
• Medium to heavy hypernuclear spectroscopy
• A L binding in the mean field, quark picture vs.
  conventional picture
• 28Si, 51V, (Cr) ? 89Y ? 208Pb ? targets
• Coincidence experiment
• weak decay --- fission
• proton, neutron and pion emission

Complimentary to spectroscopy with hadronic beams
at J-PARC
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Requested beam time
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Summary

• Precision hypernuclear spectroscopy by the
  (e,eK) reaction plays an essential role in the
  investigation of hadronic may-body systems that
  contain strangeness.
• Physics goal of the proposed experiment is
  two-fold spectroscopy of heavier L hypernuclei
  (51V target) and light L hypernuclei(6,7Li
  or10,11B targets).
• A high resolution electron spectrometer (HES) is
  under construction at TOHOKU as a part of the
  HKS-HES hypernuclear spectrometer system. It will
  be shipped to JLab at the end of 2006.
• The HKS-HES spectrometer system allows us to
  conduct the proposed 3rd generation (e,eK)
  hypernuclear spectroscopy even with 6 GeV and 12
  GeV operation.