j lab hall a experiment e94-107 16 o(e,ek + ) 16 n 12 c(e,ek + ) 12 12 c(e,ek + ) 12 be(e,ek + ) 9...
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JLAB Hall A Experiment E94-107
1616O(e,e’KO(e,e’K++))1616NN
1212C(e,e’KC(e,e’K++))1212
Be(e,e’KBe(e,e’K++))99LiLi
H(e,e’KH(e,e’K++))00
Ebeam = 4.016, 3.777, 3.656 GeV
Pe= 1.80, 1.57, 1.44 GeV/c Pk= 1.96 GeV/c
e = K = 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 Collaboration
E94107 COLLABORATION
• 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, 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 HRS+Septa
with accurate optics calibrations
Experimental requirements :
1. Ebeam/E : 2.5 x 10-5
2. P/P (HRS + septum) ~ 10-4
3. Straggling, energy loss…
Excitation energy resolution ≤ 600 keV
G. M. Urciuoli INPC2007
Septum Magnets
Electrons scatteredat 6 deg sent to theHRS at 12.5 deg.
•Superconducting magnets
•Commissioned 2003-4
RICH detector – C6F14/CsI proximity focusing RICH
Ch“MIP”
Performances: Np.e. # of detected photons (p.e.)and (angular resolution)
..
..
ep
ep
Nc
Cherenkov angle resolution
Separation Power
c n12
G. M. Urciuoli INPC2007
Rich – PID – Effect of ‘Kaon selection’:
P
K
Coincidence Time selecting kaons on Aerogels and on RICH:
AERO K AERO K && RICH K
Pion rejection factor ~ 1000
G. M. Urciuoli INPC2007
METHOD TO IMPROVE THE OPTIC DATA BASE:
An optical data base means a matrix T that transforms the focal plane coordinates inscattering coordinates:
y
x
X
Y
DP
Y
XTY
To change a data base means to find a new matrix T’ that gives a new set of values:
: XTY
''
YTX
1Because: this is perfectly equivalent to find a matrix 1' TTF
YFY
'you work only with scattering coordinates.
.
From F you simply find T’ by:
TFT '
METHOD TO IMPROVE THE OPTIC DATA BASE (II)
You have:
Y)Φ,Θ,P(DP,DPδ(DP)DPYδFDPDP'
FF 1Expressig:
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 DPDP’ also the missing energy will change:
),,,()()()(
)())(()'( YDPADPEmissDPDP
EmissDPEmissDPDPEmissDPEmiss
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:
)(
')(
DP
EmissEmissEmiss
DP
and finally to calculate
Emiss ),,,( YDPP
),,,( YDPA
)(' YYYFYY
What do we learn from hypernuclear spectroscopy Hypernuclei and the -N interaction
“weak coupling model”
(parent nucleus) ( hyperon) (doublet state)
JA 1 (s shell) JHyp JA 112
VN = V0(r) + V (r)s s N + V (r)
N
s + VN (r)
N
s N + VT (r)S12
S SNT
J 12
J
J 12
(A-1)A
SN
, S , T
Split by N spindependent interaction
HypernuclearFine Structure
Low-lying levels of Hypernuclei
Each of the 5 radial integral (V, , S, SN, T) can be phenomenologically determined from the low lying level structure of p-shell hypernuclei
V
G. M. Urciuoli INPC2007
Results on 12C target
Analysis of the reaction 12C(e,e’K)12B
Results published: M.Iodice et al., Phys. Rev. Lett. E052501, 99 (2007).Results published: M.Iodice et al., Phys. Rev. Lett. E052501, 99 (2007).
Results on 12C target – Hypernuclear Spectrum of 12B
G.S. width is 1150 keV; an unresolved doublet?What would separation be between two 670 keV peaks? ~650 keV (theory predicts only 140)
Narrowest peak is doublet at 10.93 MeV experiment resolution < 700 keV
670 keVFWHM
Preliminary Results on the WATERFALL target
Analysis of the reaction 16O(e,e’K)16N
and 1H(e,e’K)(elementary reaction)
Waterfall target allows energy-scale calibration of 16O(e,e’K)16N
by 1H(e,e’K)(peak at binding energy = zero)
Be windows H2O “foil”
H2O “foil”
the WATERFALLWATERFALL target: provides 16O and H targets
1H (e,e’K)1H (e,e’K)
16O(e,e’K)16N16O(e,e’K)16N
1H (e,e’K)1H (e,e’K)
Energy Calibration Run
Preliminary Results on the WATERFALL target - 16O and H spectra
Excitation Energy (MeV)N
b/sr
2 G
eV
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)
Results on 16O target – Hypernuclear Spectrum of 16N
- Peak Search :Identified 4 regions with excess counts above background
Binding Energy B=13.68 ± 0.16 (stat) ± 0.05 (sys) MeVMeasured for the first time with this level of accuracy (ambiguous interpretation from emulsion data; interaction involving production on n more difficult to normalize)
Fit to the data (red line): Fit 4 regions with 4 Voigt functions 2
/ndf = 1.19 Theoretical model (blu line)
superimposed curve based on :i) SLA p(e,e’K+) (elementary
process)ii) N interaction fixed
parameters from KEK and BNL 16O spectra
Results on 16O target – Hypernuclear Spectrum of 16N
11
11.5
12
12.5
13
13.5
14
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5
Serie1
E94-107
(+,K+)
(K-,-) (Kstop,-)
[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)
[2] [3] [4]
Comparison with the mirror nucleus 16O
Difference expected with respect to mirror nucleus:
400 – 500 keV (M. Sotona)
p(e,e'K+) on WaterfallProduction run
p(e,e'K+) on LH2 Cryo TargetCalibration run
Expected data from theExperiment E07-012 to study the angular dependence of p(e,e’K) and 16O(e,e’K)16N at Low Q2
(approved January, 2007)
Results on H target – The p(e,e’K)Cross Section
Be(e,e’KBe(e,e’K++))99LiLi
1.4
1.2
1.0
0.6
0.8
0.4
Li9
Chi2/NDF: 266.342 / 232 = 1.14803
0: 7.23 +/- 3.68 , 6.44+/- 0.21 , 0.71 +/- 0.15
Peak Strength Position FWHM
1: 23.20+/- /4.75 , 7.10 +/- 0.08, 0.71 +/- 0.15
2: 12.57 +/- 5.66, 8.06 +/- 0.08, 0.71 +/- 0.15
3: 11.01 +/- 5.68 , 8.54 +/- 0.08, 0.71 +/- 0.15
4: 11.87 +/- 3.51 , 9.18+/- 0.11, 0.71 +/- 0.15
The Angular Dependence of 16O(e, e K) 16N and H(e,e K+)
- 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
proposal for PAC 31 (F. Garibaldi January 0507 - Hall A Collaboration meeting - Jlab)
the proposed experiment will answer the following the proposed experiment will answer the following questionsquestions
• 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 arethese questions are very important for our very important for our understanding of dynamicsunderstanding of dynamics of the of the process and process and vitalvital for the hypernuclear calculations and for the hypernuclear calculations and interpretation of the data, interpretation of the data, they urgethey urge to be answered also for “building” the to be answered also for “building” the hypernuclear program at Jlab in hypernuclear program at Jlab in the futurethe future
Conclusion• E94-107 experiment successfully performed:
• Three hypernuclei studied:
+ the reaction:
1616N N ((submitted ) and 99
LiLi1212(published),
H(e,e’KH(e,e’K++))00
Experiment E07-012 will study the angular dependence of p(e,e’K)L and 16O(e,e’K)16NL at Low Q2(approved January, 2007)