Transcript Document

Electroproduction of hypernuclei
E94-107 experiment in Hall A
Experimental equipment and setup
Analysis results of 2004 run on 12C
Preliminary results of 2005 run on 16O
Future (experiment E07-012)
Conclusions
G.M. Urciuoli
INFN Roma III (Italy)
BNL 3 MeV(FWHM)
KEK336 2 MeV(FWHM)
Improving energy
resolution
1.45 MeV(FWHM)
635 KeV
and
using
electromagnetic
probe
≤ 500 KeV
G. M. Urciuoli INPC2007
Hall A
High resolution,
high yield, and
systematic study is
essential
JLAB Hall A 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
G. M. Urciuoli INPC2007
Present status of L Hypernuclear Spectroscopy
This exp. E94-107
16
L
N

(e,e’K+)
O. Hashimoto and H. Tamura, Prog. Part. Nucl. Phys, in press.
G. M. Urciuoli INPC2007
Hall A at Jefferson Lab
e- Source
Hall A
JLAB Hall A Experimental setup
The two High Resolution Spectrometer (HRS) in Hall A @ JLab
Beam energy: 4.0, 3.7 GeV
sE/E :
2.5 10-5
Beam current: 10 - 100 mA
Targets : 12C, 9Be, 16O
Run Time : approx 6 weeks
HRS – QQDQ main characteristics:
Momentum range: 0.3, 4.0 GeV/c
Dp/p (FWHM):
10-4
Momentum accept.: ± 5 %
Solid angle:
5 – 6 msr
Minimum Angle : 12.5°
G. M. Urciuoli INPC2007
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 HRS+Septa
with accurate optics calibrations
1. DEbeam/E : 2.5 x 10-5
2. DP/P (HRS + septum) ~ 10-4
3. Straggling, energy loss…
G. M. Urciuoli INPC2007
Excitation energy resolution ≤ 600 keV
Kinematics, Counting rates
Ebeam = 4.016 — 3.777 — 3.656 GeV
Pe= 1.80 — 1.56 — 1.44 GeV/c
Pk= 1.96
GeV/c
qe = qK = 6°
= Eg  2.2 GeV – Q2 = 0.079 (GeV/c)2
Beam current : 100 mA Target thickness : ~100 mg/cm2
Counting Rates ~ 0.1 – 10 counts/peak/hour
G. M. Urciuoli INPC2007
Septum Magnets
•Superconducting magnets
•Commissioned 2003-4
Electrons scattered
at 6 deg sent to the
HRS at 12.5 deg.
RICH detector
Ch
– C6F14/CsI proximity focusing RICH
“MIP”
Performances:
Np.e. # of detected photons (p.e.)
and sq (angular resolution)
G. M. Urciuoli INPC2007
Separation Power
2 1  ns s 
c
Cherenkov
angle resolution
s 
c
s p.e.
N p .e .
Rich – PID – Effect of ‘Kaon selection’:
Coincidence Time selecting kaons on Aerogels and on RICH:
AERO K
AERO K && RICH K
p
P
K
Pion rejection
factor ~ 1000
G. M. Urciuoli INPC2007
What do we learn from hypernuclear spectroscopy
Hypernuclei and the L-N interaction
JA1  L(s  shell)
“weak coupling model”
(parent nucleus)
(L hyperon)
VLN = V0 (r) + Vs (r)sL  sN + VL (r)
V 
D
 J Hyp  JA1  12
(doublet state)
LN
 sL + VN (r)
SL
LN
 sN + VT (r)S12
SN
T
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
J
(A-1)

G. M. Urciuoli INPC2007
J
SN
1
2
Hypernuclear
Fine Structure
Split by LN spin
dependent interaction
AL 
J
1
2
D , SL , T
Results on
12C
target – Hypernuclear Spectrum of
12B
L
12C(e,e’K)12B
L
Red line: Fit to the dataBlue line: Theoretical curve: Sagay Saclay-Lyon
(SLA) used for the elementary K-L electroproduction on
proton.Hypernuclear wave function obtained by M.Sotona and J.Millener
Results on
12C
target – Conclusion
- energy resolution ~ 635 KeV, the best achieved in hypernuclear
production experiments
- first clear evidence of excited core states at ~2.5 and 6.5
MeV with high statistical significance
- the width of the strong pL peak and the distribution of strength
within several MeV on either side of this peak can put constraints
on the hypernuclear structure calculations
- hint for a peak at 9.65 MeV excitation energy (admixture)
2005 E-94107: Running on waterfall target
Be windows
H2O “foil”
H2O “foil”
G. M. Urciuoli INPC2007
Theoretical model for
16N
Lexcitation-energy
on
16O
target
The structure of underlying nucleus 15N is dominated by:
(i) J=1/2-proton-hole state in 0p1/2 shell - ground state
(ii) J=3/2- proton-hole state in 0p3/2 shell - Excited states at Ex = 6.32 MeV
Details of the hypernuclear spectrum at Ex ~ 17-20 MeV depends not only on L-N residual
interaction but also on the Lsingle particle spin-orbit splitting (difference in energy of 0p3/2 and
0p1/2 L states)
15N
energy spectrum
16N
L
energy spectrum
16O(e,e’K)16N
L
Coupling of
Lp1/2 and Lp3/2
Analysis on
16N spectrum : FIT to the data
L
G. M. Urciuoli INPC2007
+

The Angular Dependence of16O(e,eK )16
N
and
H(e,
e
K
)L
L
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
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
Conclusions:
Experiment E94-107 at Jefferson Lab: GOAL is to carry out a systematic study
of light hypernuclei (shell-p).
The experiment required important modifications on the Hall A apparatus.
Good quality data on
12C, 9Be
and
16O
targets (12BL ,9LiL and
16N
L
hypernuclei)
have been taken
New experimental equipments showed excellent performance.
The RICH detector performed as expected and it is crucial in the kaon
selection.
Analysis of data on
the
12B
12C
target showed new information on the spectroscopy of
Lhypernucleus
VERY Promising physics is coming out from new data on the waterfall target
for
16N hypernuclear
L
G. M. Urciuoli INPC2007
spectroscopy - also for p(e,e’K)LX-Sect. measurement
E94-107 Hall A Experiment Vs. KEK-E336
16O(e,e’K)16N
L
p
16O( ,K+)16O
L
Mauro Iodice – XLIV Meeting on Nucl. Phys. - Bormio06, Italy - January 29 - February 5, 2006
E94-107 Hall A Experiment Vs. g-ray spectroscopy at BNL
16O(e,e’K)16N
L
G. M. Urciuoli INPC2007
16O(K-,
p g)
16O
L