Hypernuclei: A quick introduction
Electroproduction of hypernuclei
E94-107 experiment UPDATE
Experimental equipment and setup
Analysis results of 2004 run on 12C and 9Be
Preliminary results of 2005 run on 16O
Conclusions
Mauro Iodice – e94107 update – Hall A Collaboration Meeting, JLAB, Dec 6 2005
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
Mauro Iodice – e94107 update - Hall A Collaboration Meeting, JLAB, Dec 6 2005
HYPERNUCLEI …what they are
Hypernuclei are bound states of nucleons with a strange baryon (Lambda
hyperon). A hypernucleus is a “laboratory” to study nucleon-hyperon
interaction (L-N interaction).
Extension of physics on N-N interaction to system with S0
Internal nuclear shell are not
Pauli-blocked for hyperons.
Mauro Iodice – e94107 update - Hall A Collaboration Meeting, JLAB, Dec 6 2005
HYPERNUCLEI and ASTROPHYSICS
Strange baryons may appear in neutral b-stable matter through process
like:
n  e     e
The presence of strange baryons in
neutron stars strongly affect their
properties. Example: mass-central
density relation for a non-rotating (left)
and a rotating (right) star
The effect strongly depends upon the
poorly known interactions of strange
baryons
More
data
needed
to
constrain theoretical models.
Mauro Iodice – e94107 update - Hall A Collaboration Meeting, JLAB, Dec 6 2005
Hypernuclei - historical background - experimental techniques
1953 : discovery of first hypernucleus
by Danysz and Pniewski
while studying cosmic radiation
with emulsion techniques
To commemorate their discovery the above
postcard was issued by the Polish Post in May 1993
1962 : The first double LL Hypernucleus was
The first observation of a
hypernucleus
discovered in a nuclear emulsion
irradiated by a beam of K- mesons
at CERN
Mauro Iodice – e94107 update - Hall A Collaboration Meeting, JLAB, Dec 6 2005
Hypernuclei - historical background - experimental techniques
1953  1970 : hypernuclear identification with visualizing techniques
emulsions, bubble chambers
1970  Now :
Spectrometers at accelerators:
Elementary reaction
on neutron :
CERN (up to 1980)
K  n  p   L
BNL : (K-, p-) and (K+, p+) production methods
p   n  K  L
KEK : (K-, p-) and (K+, p+) production methods
e.g.

> 2000 :
Stopped kaons at DAFNE (FINUDA) : (K-stop, p-)
> 2000 :
The new electromagnetic way :
HYPERNUCLEAR production with


ELECTRON BEAM at JLAB
C 
12
12
CL
Elementary reaction
on proton :
e  p  e K   L
e.g.

Production of MIRROR hypernuclei
L: I=0, q=0
C 
12
12
BL
 Ln = Lp
Spectroscopy of mirror hypernuclei reveal Ln ≠ Lp  L0 mixing and LN-N coupling

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.
Mauro Iodice – e94107 update - Hall A Collaboration Meeting, JLAB, Dec 6 2005
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) + V (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)

J
SN
1
2
Hypernuclear
Fine Structure
Split by LN spin
dependent interaction
AL 
J
1
2
D , SL , T
Mauro Iodice – e94107 update - Hall A Collaboration Meeting, JLAB, Dec 6 2005
E94-107 Experiment:
“High Resolution 1p Shell Hypernuclear Spectroscopy”
(spokespersons: F. Garibaldi, S. Frullani, J. Le Rose, P. Markowitz, T. Saito – Hall
Electroproduction of hypernuclei
by the reaction:
e  Z  e K 
A

A
Z 1L
Spin flip states
pL Production of mirror nuclei / n rich hypernuclei
High energy resolution

AZ(e,e’K)A(Z-1)
e’
e
e beam
~4 GeV
A Coll.)
L
HRSe at 6˚
K+
p
L
HRSk at 6˚
Hypernucleus
Nuclear targets and resulting hypernuclei:
9Be
12C
 9LiL(spin doublets, information on s-s term of L-N interaction potential)

12B
L(comparison with previous data: better understanding of results with hadron probes
and E89-009 in Hall C at Jefferson Lab; clear identification of core excited states)
16O

16N
L (details of the hyper. spectrum also depends on
L single particle spin-orbit splitting )
Mauro Iodice – e94107 update - Hall A Collaboration Meeting, JLAB, Dec 6 2005
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 spread (SLI, OTR) and absolute energy, spectrometers NMR, BPMs, …
Excellent energy resolution  Best performance for beam and HRS+Septa
with accurate optics calibrations
1. DE/E : 2.5 x 10-5
2. DP/P (HRS + septum) ~ 10-4
3. Straggling, energy loss…
≤ 600 keV
Mauro Iodice – e94107 update - Hall A Collaboration Meeting, JLAB, Dec 6 2005
Data taking, Kinematics, Counting rates :
Last year e94107 experiment took data in two separate periods. Data have been
collected on solid targets. The second part of the experiment took data in June 2005 in
Hall A using the waterfall target
January 2004
12C
April 2004
target and May 2004
12C
target
9Be
June 2005 Waterfall target for hypernuclear state production on
(as a byproduct) on the elementary process on Hydrogen
16O
and
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
Mauro Iodice – e94107 update - Hall A Collaboration Meeting, JLAB, Dec 6 2005
SEPTUM magnets in Hall A:
new optics DB for the D+QQDQ system
QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
OLD DB “2004”
NEW DB “2005”
FWHM = 1.1x10-4
FWHM = 2.2x10-4
Mauro Iodice – e94107 update - Hall A Collaboration Meeting, JLAB, Dec 6 2005
KAON Id Requirements physics case
Signal Vs. Background
Process
Rates
signal
Bound
states
(e,e’K)
10-4 – 10-2
accidentals
(e,e’)(e,p)
(e,e’)(e,p)
(e,e’)(e,k)
100
100
0.1
Forward angles  higher
background of p and p
 TOF and 2 Threshold
Cherenkov NOT sufficient for
unambiguous kaon
identification
 RICH DETECTOR
Mauro Iodice – e94107 update - Hall A Collaboration Meeting, JLAB, Dec 6 2005
RICH detector
Ch
–C6F14/CsI proximity focusing RICH
“MIP”
Performances:
Np.e. # of detected photons (p.e.)
and q (angular resolution)
Separation Power
Cherenkov
angle resolution
2  1  n   
c
Mauro Iodice – e94107 update - Hall A Collaboration Meeting, JLAB, Dec 6 2005
 
c
 p.e.
N p .e .
Rich Performance
‘key parameters’:
Npe for pand p
Cherenkov angle for p
Nclusters
Npe p/p ratio:
P
N clus
1  b P2 n 2

 0.66
p
2 2
N clus 1  bp n
Cherenkov average angle (rad)
Angular resolution:
   5 mrad
c
Mauro Iodice – e94107 update - Hall A Collaboration Meeting, JLAB, Dec 6 2005
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
Mauro Iodice – e94107 update - Hall A Collaboration Meeting, JLAB, Dec 6 2005
Rich – PID – Effect of ‘Kaon selection’:
Coincidence Time selecting kaons on Aerogels and on RICH:
AERO K
AERO K && RICH K
K
p
P
GREATLY
improved
AEROGEL
performance!
Mauro Iodice – e94107 update - Hall A Collaboration Meeting, JLAB, Dec 6 2005
Shell model excitation levels for 12BL
dependence on the LN potential - different set of potential params.
11C
12B
energy spectrum
L
energy spectrum
J=2+, 3+
J=2+, 3+
J=2+, 3+
x 0pL
J=2J=3/2-
x 0sL
J=2-
J=2-
E=~5 MeV
J=5/2E=~4.5 MeV
J=1/2-
E=~2 MeV
J=3/2E=0.0 MeV
J=1x 0sL
x 0sL
J=1J=1J=1-, 2- doublet
YNG potential
“Canonical”
“Standard”
Mauro Iodice – e94107 update - Hall A Collaboration Meeting, JLAB, Dec 6 2005
Monte Carlo simulation of 12BLexcitation-energy levels
produced on 12C target
12C(e,e’K)12B
L
VNL  V0 (r )
 V (r )  N   L
 VSO (r )  LN   L
V (central)
D (spin  spin)
S L spin  orbit 
 VSO (r )  LN   N
S N spin  orbit 
 VT (r ) S12
T (Tensor)


S12  3( N  r )( L  r )  ( N   L )
a
b
c
d
Absolute and relative positions of “resolved” levels a,b,c,d, may provide information on
parameters of LN interaction potential and its terms (spin-spin, spin-orbit, tensor, …)
Mauro Iodice – e94107 update - Hall A Collaboration Meeting, JLAB, Dec 6 2005
Monte Carlo simulation of 9LiLexcitation-energy levels
Produced on 9Be target
Excitation-energy levels of 9LiLhypernucleus, especially from the first-doublet levels a and
b, would provide important information on D, SL and T terms of the LN interaction.
Separation of c and d doublets may provide information on the spin-orbit term SN
VNL  V0 (r )
 V (r ) N   L
 VSO (r )lLN   L
9Be(e,e’K)9Li
a b
c
V (central)
D (spin  spin)
S L spin  orbit 
 VSO (r )lLN   N
S N spin  orbit 
 VT (r ) S12
T (Tensor)


S12  3( N  r )( L  r )  ( N   L )
L
d
Mauro Iodice – e94107 update - Hall A Collaboration Meeting, JLAB, Dec 6 2005
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
Results from last year run on
12C
target
Analysis of the reaction
12C(e,e’K)12B
L
Mauro Iodice – e94107 update - Hall A Collaboration Meeting, JLAB, Dec 6 2005
Results on
12C
target – Hypernuclear Spectrum of
12B
Missing energy (MeV)
12C(e,e’K)12B
g.s.
L
< 1 MeV
FWHM
As obtained with the old optics DB. The new one does not improve the resolution …
still under analysis/investigation
Mauro Iodice – e94107 update - Hall A Collaboration Meeting, JLAB, Dec 6 2005
L
Analysis on
12B spectrum : Aerogel vs. RICH K-selection
L
12C(e,e’K)12B
Signal
 2.5
Bckgnd
L
Aerogel Kaon
selection

Signal
7
Bckgnd
RICH Kaon
selection

Mauro Iodice – e94107 update - Hall A Collaboration Meeting, JLAB, Dec 6 2005
Analysis on
12B spectrum : FIT to the data
L
Gaussian fit systematically underestimate
The peaks  try with different shapes :
Mauro Iodice – e94107 update - Hall A Collaboration Meeting, JLAB, Dec 6 2005
JLAB Hall A E94-107:
Counts / 200 keV
preliminary comparison with theory for
12C(e,e’K)12B
L
12B hypernucleus
L
Two theoretical curves (blue and
red), two different model for
the elementary K-L
production on proton.
Same hypernuclear wavefunction (by Miloslav Sotona).
Red line: Bennhold-Mart (K
MAID)
Blue line: Sagay Saclay-Lyon
(SLA).
Curves are normalized on g.s.
peak.
Missing energy (MeV)
The relative intensity of first excited-core peak at 2.6 MeV and
strongly populated p-Lambda peak at 11 MeV would be better
described by K MAID model than SLA.
Mauro Iodice – e94107 update - Hall A Collaboration Meeting, JLAB, Dec 6 2005
JLAB Hall A E94-107:
Counts / 200 keV
preliminary comparison with theory for
12C(e,e’K)12B
L
12B hypernucleus
L
Two theoretical curves (blue and
red), two different model for
the elementary K-L
production on proton.
Same hypernuclear wavefunction (by Miloslav Sotona).
Red line: Bennhold-Mart (K
MAID)
Blue line: Sagay Saclay-Lyon
(SLA).
Curves are normalized on g.s.
peak.
Missing energy (MeV)
g.s. CrossSection =
5.00 nb/(GeV sr2 )
Stat ~ 4.3 %
Syst ~ 20 %
Theory =
5.4 nb/(GeV sr2 ) …!!!
Mauro Iodice – e94107 update - Hall A Collaboration Meeting, JLAB, Dec 6 2005
Analysis on
12B spectrum : COMPARISON with models
L
New comparison: inclusion of ”all” predicted levels bring to a stronger
disagreement for levels with L in p-shell
Mauro Iodice – e94107 update - Hall A Collaboration Meeting, JLAB, Dec 6 2005
E94-107 Hall A Experiment Vs. KEK-E369
12C(e,e’K)12B
L
p
12C( ,K+)12C
L
H. Hotchi et al., Phys. Rev. C 64 (2001) 044302
Statistical significance of core excited states:
Signal
7
Bckgnd
Mauro Iodice – e94107 update - Hall A Collaboration Meeting, JLAB, Dec 6 2005
E94-107 Hall A Experiment Vs. FINUDA (at DaFne)
12C(e,e’K)12B
L
12C(K- ,
p)12CL
Statistical significance of core excited states:
Signal
7
Bckgnd
Mauro Iodice – e94107 update - Hall A Collaboration Meeting, JLAB, Dec 6 2005
E94-107 Hall A Experiment Vs. HallC E89-009
12C(e,e’K)12B
L
12C(e,e’K)12B
L
Miyoshi et al., PRL 90 (2003) 232502.
New analysis
Statistical significance of core excited states:
Signal
7
Bckgnd
Mauro Iodice – e94107 update - Hall A Collaboration Meeting, JLAB, Dec 6 2005
E94-107 Hall A Experiment: status of
12C(e,e’K)12B
L
Statistical significance of core excited states:
Signal
7
Bckgnd
12B
L
data
Energy resolution is ~ 900 keV with
old optics database
More than one year spent to improve
the resolution
Although the new database does a
very good job for single arm elastics
data: 1.1 10-4 the expected resolution
of less than 600 keV is not yet
achieved
some more check and tuning has to
be done, …but :
despite
the
fact
that
optimal
resolution has not yet been obtained,
the data are of extremely good quality
… to be published soon
Mauro Iodice – e94107 update - Hall A Collaboration Meeting, JLAB, Dec 6 2005
Results from last year run on 9Be target
Analysis of the reaction 9Be(e,e’K)9LiL
(still preliminary)
Mauro Iodice – e94107 update - Hall A Collaboration Meeting, JLAB, Dec 6 2005
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)
Mauro Iodice – e94107 update - Hall A Collaboration Meeting, JLAB, Dec 6 2005
JLAB Hall A E-94107: Preliminary Results on 9Be target
Red line: Bennhold-Mart (K MAID)
Counts / 200 keV
Blue line: Sagay Saclay-Lyon (SLA)
Curves are normalized on g.s. peak.
Missing energy (MeV)
Mauro Iodice – e94107 update - Hall A Collaboration Meeting, JLAB, Dec 6 2005
First Results from current experiment on WATERFALL target
Analysis of the reaction
16O(e,e’K)16N
L
and 1H(e,e’K)L(elementary reaction)
Mauro Iodice – e94107 update - Hall A Collaboration Meeting, JLAB, Dec 6 2005
2005 E-94107: Running on waterfall target
Be windows
H2O “foil”
H2O “foil”
Mauro Iodice – e94107 update - Hall A Collaboration Meeting, JLAB, Dec 6 2005
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
Mauro Iodice – e94107 update - Hall A Collaboration Meeting, JLAB, Dec 6 2005
Analysis on
16N spectrum : FIT to the data
L
Mauro Iodice – e94107 update - Hall A Collaboration Meeting, JLAB, Dec 6 2005
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,
poorly known….
Mauro Iodice – e94107 update - Hall A Collaboration Meeting, JLAB, Dec 6 2005
Analysis on
16N spectrum : COMPARISON with models
L
…SHIFTING “by hand” the positions
of these MULTIPLETS in the model,
while mantaining the predicted
strength, a VERY GOOD agreement
with the data can be reached.
Work is in progress for a deeper
physics interpretation.
Mauro Iodice – e94107 update - Hall A Collaboration Meeting, JLAB, Dec 6 2005
E94-107 Hall A Experiment Vs. KEK-E336
16O(e,e’K)16N
L
p
16O( ,K+)16O
L
Mauro Iodice – e94107 update - Hall A Collaboration Meeting, JLAB, Dec 6 2005
E94-107 Hall A Experiment Vs. g-ray spectroscopy at BNL
16O(e,e’K)16N
L
16O(K-,
p g)
16O
L
Mauro Iodice – e94107 update - Hall A Collaboration Meeting, JLAB, Dec 6 2005
Importance of the elementary reaction 1H(e,e’K)Lat low Q2
K+L photoproduction
1H
(e,e’K)L
In K+L photoproduction on proton there is a
clear inconsistency of the experimental data
(CLAS vs SAPHIR) at QKcm < 40 deg.
Electroproduction at very low Q2 can clarify this
inconsistency, which is also important for
calculation for hypernuclear cross sections.
Mauro Iodice – e94107 update - Hall A Collaboration Meeting, JLAB, Dec 6 2005
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
and 9Be targets (12BLand 9LiL hypernuclei) have
been taken last year
New experimental equipments showed excellent performance.
The RICH detector performed as expected and it is crucial in the kaon
selection.
On-going Analysis of data on
12C
target is showing new information on
and interesting comparison with theory for
12B
L
12B
L
and 9LiL.
VERY Promising physics is coming out from new data on the waterfall target
for
16N hypernuclear
L
spectroscopy - also for p(e,e’K)LX-Sect. measurement
Mauro Iodice – e94107 update - Hall A Collaboration Meeting, JLAB, Dec 6 2005