Transcript Document 7656023

9
16 N High resolution spectroscopy by
Li
and
L
L
electron scattering at Jefferson Lab in Hall-A.
S. Marrone* on behalf of E94-107 Collaboration.
*Dipartimento di Fisica and INFN, Bari, Italy.
OUTLINE
Electroproduction of hypernuclei.
E94-107 experiment:
Experimental equipment and setup;
Preliminary results of Be and O.
Conclusions.
S. Marrone – HYP 2006, Mainz 10-14 October 2006
JLAB Hall A E94-107
COLLABORATION
(spokespersons: F. Garibaldi, S. Frullani,
J. Le Rose, P. Markowitz, T. Saito)
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
S. Marrone – HYP 2006, Mainz 10-14 October 2006
Electroproduction of Hypernuclei
Hypernucleus
L
Kaon detected
by HRSk
Scattered electron
Detected by HRSe
K+
g*
beam
e’
N…N
A
Z 1L
e  p  e K +  L
Better energy resolution than
hadronic induced reactions,
BUT smaller cross section
L
p
p
e
e  AZ  e  K  
N…N
nucleus
High luminosity, high duty cycle,
excellent beam energy spread
obtained at CEBAF in Hall-A.
S. Marrone – HYP 2006, Mainz 10-14 October 2006
E94-107 Experiment:
“High Resolution 1p Shell Hypernuclear Spectroscopy”
Nuclear targets and resulting hypernuclei:
 9Be  9LiL (spin doublets, information on spin-spin and spin-orbit term of L-N interaction
potential)

12C

12B
L (comparison with previous data: better understanding of results with hadron
probes and E89-009 in Hall C at Jefferson Lab explained in LeRose’s talk)

16O

16N
L (details of the hypernuclear spectrum also depends on
L single particle and
spin-orbit splitting)

1H(e,e’K)L for free because of the water target (Markovitz’s talk, parallel session C1)
Experimental requirements:
1. Excellent Energy Resolution: Best performances ever obtained for Beam and
High Resolution Spectrometer in Hall-A. (LeRose’s talk on monday).
2. Detection at very forward angles (6° to obtain reasonably high counting rates)
 Septum Magnets (F. Cusanno’s talk parallel session A3).
3. Excellent Particle Identification system (PID) for unambiguous kaon
selection  RICH (F. Cusanno’s talk).
S. Marrone – HYP 2006, Mainz 10-14 October 2006
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
S. Marrone – HYP 2006, Mainz 10-14 October 2006
Hall A - Two High Resolution Spectrometers
QDQ - Momentum Range: 0.3–4 GeV/c Dp/p : 1 x 10-4 – Dp = =-5% - DW = 5 –6 mr
12°
Septa
Detectors:
3 Scintillators for trigger,
2 VDC for tracking,
Gas Cherenkov and Showers
for PID in Electron Arm.
2 Cherenkov Aerogels +
RICH for PID in Hadrom
Arm
Results from 9Be target
Analysis of the reaction 9Be(e,e’K)9LiL
(still preliminary)
S. Marrone – HYP 2006, Mainz 10-14 October 2006
Weak Coupling Model
“weak coupling model”
Monte Carlo Simulations on 9Be target.
J A1  L ( s  shell )  J Hyp = J A1  12
(parent nucleus)
(L hyperon)
(doublet state)
2735
7/2+
2265
5/2+
1436
1424
1/2+
3/2+
581
5/2+
0
3/2+
2+
2255
sL
1+
981
sL
2+
0
8Li
sL
9
LLi
Counts / 400 keV
JLAB Hall A E-94107: Preliminary Results on 9Be target
9Be(e,e’K)9Li
L
Aerogel Kaon
selection
RICH Kaon
selection
Missing energy (MeV)
S. Marrone – HYP 2006, Mainz 10-14 October 2006
ANALYSIS of the reaction 9Be(e,e’K)9LiL
Red curve:
elementary process
by Benhold-Mart (K
MAID) - Hyp w.f. by
M.Sotona
Counts / 200 keV
Blue line:
elementary process
by Saghai SaclayLyon (SLA)- Hyp.
W.f. by M.Sotona
Black line:
elementary process
by Saghai SaclayLyon (SLA)- Hyp.
W.f. by J.Millener
Missing energy (MeV)
S. Marrone – HYP 2006, Mainz 10-14 October 2006
Curves are normalized
on g.s. peak.
First Results from the experiment on WATERFALL target
Analysis of the reaction
S. Marrone – HYP 2006, Mainz 10-14 October 2006
16O(e,e’K)16N
L
2005 E-94107: Running on waterfall target
Be windows
H2O “foil”
H2O “foil”
S. Marrone – HYP 2006, Mainz 10-14 October 2006
Theoretical model for
The structure of underlying nucleus
16N
L excitation-energy
15N
on
16O
target
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
2005 E-94107: Preliminary spectra of missing energy
16O(e,e’K)16N
L
1H
Low counting levels
above Ethr.
(e,e’K)L
16O(e,e’K)16N
L
16O(e,e’K)16N
L
S. Marrone – HYP 2006, Mainz 10-14 October 2006
Analysis on
16N spectrum : FIT to the data
L
S. Marrone – HYP 2006, Mainz 10-14 October 2006
Analysis on
16N spectrum : COMPARISON with models
L
15N
energy spectrum16NL energy spectrum
High energy excited MULTIPLETS
seems NOT WELL reproduced by
the model.
L-interaction here is in p-state and
is poorly known….
S. Marrone – HYP 2006, Mainz 10-14 October 2006
E94-107 Hall A Experiment Vs. KEK-E336
16O(e,e’K)16N
L
S. Marrone – HYP 2006, Mainz 10-14 October 2006
p
16O( ,K+)16O
L
E94-107 Hall A Experiment Vs. g-ray spectroscopy at BNL
16O(e,e’K)16N
L
S. Marrone – HYP 2006, 10-14 October 2006
16O(K-,
p g)
16O
L
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 in term of resolution and SNR on 9Be and
16O
targets have
been taken.
New experimental equipments demonstrated excellent performance.
The RICH detector performs, as expected, crucial role in the kaon selection.
Preliminary analysis of data on 9Be target is showing new information and
interesting comparison with theory for 9LiL.
VERY Promising physics is coming out from the present data analysis on
16N
L
hypernuclear spectroscopy (also with p(e,e’K)L Cross-Section.
In the Oxygen case, we have started the normalization procedures to extract
the cross sections.
S. Marrone – HYP 2006, 10-14 October 2006
HYPERNUCLEI and ASTROPHYSICS
contd
There is growing evidence that hyperons appears the first of the strange
hadrons in neutron stars at around twice normal density….The onset of the
hyperon formation is controlled by the attactive hyperon-nucleon interaction wich
can be extracted from hypernucleon scattering data and hypernuclear data
(J. Shaffner-Bielich et al: Hyperstars: Phase Transition to (meta)-Stable Hyperonic matter in
neutron Stars, arXiv: astroph/0005490
“ Additional experimental data from hypernuclei will be useful in establishing
the foundations of high density matter models. This is especially relevant for the
hyperon-nucleon interactions, for which relevant systems are more likely to be
produced in current accelerators than for hyperon-hyperon interactions”
in S. Balberg et al: Roles of hyperons in Neutron Stars, arXiv: astro-ph/9810361
S. Marrone – Indian-Summer School, Rez, Prague 3-7 October 2006