JLAB Hall A Experiment E94107

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JLAB Hall A Experiment E94-107
E94107 COLLABORATION
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
Collaboration

• Ebeam 4.016, 3.777, 3.656 GeV
• Pe 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 lt100 mA Target thickness 100
  mg/cm2
• Counting Rates 0.1 10 counts/peak/hour

16O(e,eK)16?N 12C(e,eK)12?? ?Be(e,eK)9?Li H(
e,eK)???0
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Experimental requirements

• Detection at very forward angle to obtain
  reasonable counting rate (increase photon flux) ?
  Septum magnets at 6
• Excellent ParticleIDentification system for
  unambiguous kaon selection over a large
  background of p, p ? RICH
• Accurate monitoring of many parameters over a
  long period of data taking Beam energy spread
  and absolute calibration, spectrometers settings
  and stability,
• Excellent energy resolution ? Best performance
  for beam and HRSSepta with accurate optics
  calibrations

1. DEbeam/E 2.5 x 10-5 2. DP/P (HRS septum)
10-4 3. Straggling, energy loss
Excitation energy resolution 600 keV
G. M. Urciuoli INPC2007
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Septum Magnets

• Superconducting magnets
• Commissioned 2003-4

Electrons scattered at 6 deg sent to the HRS at
12.5 deg.
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RICH detector C6F14/CsI proximity focusing RICH
MIP
Cherenkov angle resolution
Separation Power
Performances Np.e. of detected photons
(p.e.) and sq (angular resolution)
G. M. Urciuoli INPC2007
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Rich PID Effect of Kaon selection
Coincidence Time selecting kaons on Aerogels and
on RICH
AERO K
AERO K RICH K
2004
p
P
K
Pion rejection factor 1000
G. M. Urciuoli INPC2007
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METHOD TO IMPROVE THE OPTIC DATA BASEAn
optical data base means a matrix T that
transforms the focal plane coordinates
inscattering coordinates
To change a data base means to find a new matrix
T that gives a new set of values




Because
this is perfectly equivalent to find a matrix
?.
you work only with scattering coordinates.
From F you simply find T by
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METHOD TO IMPROVE THE OPTIC DATA BASE (II)
Expressig

• You have

just consider as an example the change in the
momentum DP because of the change in the data
base
with
a polynomial expression



Because of the change DP?DP also the missing
energy
will change
In this way to optimize a data base you have just
to find empirically a polynomial
in the scattering coordinates that added to the
missing energy improves its resolution
and finally to calculate
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What do we learn from hypernuclear spectroscopy
Hypernuclei and the L-N interaction
weak coupling model
(parent nucleus) (L hyperon)
(doublet state)
D
SL
SN
T
V
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
Low-lying levels of L Hypernuclei
Hypernuclear Fine Structure
SN
Split by LN spin dependent interaction
(A-1)
D
AL
, SL
, T
G. M. Urciuoli INPC2007
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Results on 12C target
Analysis of the reaction 12C(e,eK)12BL
Results published M.Iodice et al., Phys. Rev.
Lett. E052501, 99 (2007).
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Results on 12C target Hypernuclear Spectrum of
12BL
Narrowest peak is doublet at 10.93 MeV ?
experiment resolution lt 700 keV
G.S. width is 1150 keV an unresolved
doublet? What would separation be between two 670
keV peaks? ? 650 keV (theory predicts only
140)
670 keV FWHM
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Preliminary Results on the WATERFALL target
Analysis of the reaction 16O(e,eK)16NL
and 1H(e,eK)L (elementary reaction)
Waterfall target allows energy-scale calibration
of 16O(e,eK)16NL by 1H(e,eK)L (peak at binding
energy zero)
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the WATERFALL target provides 16O and H targets
H2O foil
Be windows
H2O foil
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Preliminary Results on the WATERFALL target - 16O
and H spectra
1H (e,eK)L
1H (e,eK)L,S
L
Energy Calibration Run
S
16O(e,eK)16NL
Nb/sr2 GeV MeV
Excitation Energy (MeV)

• Water thickness from elastic cross section on H
• Fine determination of the particle momenta and
  beam energy
• using the Lambda peak reconstruction (resolution
  vs position)

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Results on 16O target Hypernuclear Spectrum of
16NL
- Peak Search Identified 4 regions with excess
counts above background

• Fit to the data (red line) Fit 4 regions with 4
  Voigt functions ? c2/ndf 1.19
• Theoretical model (blu line) superimposed curve
  based on
• SLA p(e,eK)? (elementary process)
• ?N interaction fixed parameters from KEK and BNL
  16?O spectra

Binding Energy BL13.68 0.16 (stat) 0.05
(sys) 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)
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Results on 16O target Hypernuclear Spectrum of
16NL
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3
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2 O. Hashimoto, H. Tamura, Part Nucl Phys 57,
564 (2006) 3 private communication from D.
H. Davis, D. N. Dovee, fit of data from Phys
Lett B 79, 157 (1978) 4 private
communication from H. Tamura, erratum on Prog
Theor Phys Suppl 117, 1 (1994)
E94-107
Difference expected with respect to mirror
nucleus 400 500 keV (M. Sotona)
(Kstop,p-)
(K-,p-)
(p,K)
Comparison with the mirror nucleus 16OL
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Results on H target The p(e,eK)L Cross Section
p(e,e'K)L on Waterfall Production run
p(e,e'K)L on LH2 Cryo Target Calibration run
Expected data from the Experiment E07-012 to
study the angular dependence of p(e,eK)L and
16O(e,eK)16NL at Low Q2 (approved January, 2007)
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?Be(e,eK)9?Li

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Chi2/NDF 266.342 / 232 1.14803
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Peak    Strength     Position   FWHM
 
4    11.87 /- 3.51 ,   9.18/- 0.11,
0.71 /- 0.15
3     11.01 /- 5.68 ,   8.54 /- 0.08,  
0.71 /- 0.15
2     12.57 /- 5.66,   8.06 /- 0.08,  
0.71 /- 0.15
1     23.20/- /4.75 ,   7.10 /- 0.08,
  0.71 /- 0.15
0       7.23 /- 3.68 ,   6.44/- 0.21 ,
0.71 /- 0.15
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proposal for PAC 31 (F. Garibaldi January 0507 -
Hall A Collaboration meeting - Jlab)

• hypernuclear physics
• the electromagnetic approach
• recent results
• motivation
• the elementary reaction
• angular distribution
• the apparatus
• kinematics and counting rates
• beam time request
• summary and conclusion

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the proposed experiment will answer the following
questions does the cross section for the
photo-production continue in rising as the kaon
angle goes to zero or is there a plateau or
even a dip like for the high-energy
data?(relationship with CLASS data) is the
concept of the hadronic form factors as it is
used in the isobaric models still correct? What
is the angular dependence of the hypernuclear
form factor at forward angle? . is the
hypernuclear angular dependence the same as the
hypernuclear process? which of the models
describes better the reality at forward angles
and can be therefore used in analysis of
hypernuclear data without introducing an
additional uncertainty? . the success of the
previous experiment (very clean (background
free) data) guarantees for the experimental
equipment (optics, PID), analysis, rates (beam
time) evaluation to be under control.
(extrapolations easy). unique possibility
for this experiment in Hall A with waterfall
target, septa and PID these questions are very
important for our understanding of dynamics of
the process and vital for the hypernuclear
calculations and interpretation of the data, they
urge to be answered also for building the
hypernuclear program at Jlab in the future
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Conclusion

• E94-107 experiment successfully performed
• Three hypernuclei studied
• the reaction

High Resolution 1p shell Hypernuclear
Spectroscopy at JLAB, Hall A
16?N (submitted ) and 9? Li
12?? (published),
H(e,eK)???0
Experiment E07-012 will study the angular
dependence of p(e,eK)L and 16O(e,eK)16NL at Low
Q2 (approved January, 2007)