Transcript Diapositiva 1 - Istituto Nazionale di Fisica Nucleare

E94-107: Hypernuclei Status Report
Francesco Cusanno
Hall A collaboration meeting, May 17-18, 2004
E94-107: high resolution hypernuclei spectroscopy program
on 1p-shell nuclei

Main goal: LN interaction
 Septum magnets commissioned on December
 RICH added to the hadron PID system
 Data taking: January 13 – 28 and April 17 – May 17
 Collected charge: 49.6 Coulomb on
9Be, one day on Hydrogen
12C
and 56.1 Coulomb on
Hypernuclear High Resolution Spectroscopy
E-94-107
F. Garibaldi, S. Frullani, J. LeRose, P. Markowitz, T. Saito
e + AZ -> e’ + K+ + A(Z -1)L
+ Vs( r ) SL.SN + VL(r ) SN.lNL + VT( r) S12
Sezioni d'urto sull'O
Cross
section
10
1
nb/sr2/GeV
VLN = V( r )
0,1
0,01
0,001
0,0001
0,00001
5
10
15
20
Electron scattering angle
The targets
12C:
comparison with present data, better understanding of the data
with hadronic probes and Hall C E89-009 (additional peak(s) found
respect to predictions)
9Be:
spin doublets, s-s potential parameter clarification.
The next goals:
7Li:
large neutron excess
16O:
ground state doublet investigation, ‘original’ target
The kinematics
Ei = 4.016 GeV, 3.777 (3.775) GeV
Pk= 1.98 GeV/c, 1.96 GeV/c
Pe= 1.80 GeV/c, 1.56 GeV/c
On-line ‘observations’
 Cross sections on nuclei are smaller than expected
 The background is smaller than expected and it is very
strongly reduced by the PID system.
The resulting contamination on the missing energy spectrum is
very small.
The absence of contamination and the good resolution allow a
good spectroscopy also with the real counting rate.
 The missing energy spectrum could be strongly improved by a
‘event-by-event’ evaluation of the beam central energy
Main Results 12C
Run Time:
January 9 – 27 and April 18 – 25
Number of Runs Analyzed 198 (January) + 214 (April, runs from 2524
up to 2777)
Total Charge:
Accumulated 49.6 Coulomb; different sets of data: RICH, kinematics,
beam energy
1 Coulomb @ 100 mA are 2.8 hours = 5.79 effective days (2.71 + 3.08)
Total Counts
700 Total ground-state counts, background subtracted;
Background counts =
1.1 counts / MeV x Coulomb (RICH);
700 Counts in the g. s. peak = 14.1 counts / Coulomb;
Not all of the data here!
background
•
•
•
•
Performance
The ground state and the p-shell state are identified with a good statistics
Indication of core-excited states and p-shell state (confirmation of Hall C E89009 data?).
The reduction factor with respect to the expected counting rate is 7.0 – 7.5.
The energy resolution is ‘under investigations’
800 keV
1.5 MeV
MeV
MeV
MeV
Much better?
Run #
MeV
Main Results
9Be
Run Time:
Started on 26 April Owl shift;
Runs Analyzed on 11 April 8.00 am, 16 Days.
Number of Runs Analyzed 435 from 2779 up to 3445.
Total Charge:
Accumulated 56.1 Coulomb;
1 Coulomb @ 100 mA are 2.8 hours = 6.54 effective days;
Beam Efficiency 41%;
Total Counts
1050 Total Counts no background subtracted;
400 Background counts =
7.1 counts / Coulomb;
650 Counts in the peak = 11.6 counts / Coulomb;
•
•
Performance
The reduction factor with respect to the expected counting rate is 6.5 (a bit better than C?) .
The resolution is improved 0.8 MeV (FWHM) with respect to the C data but is still poor for a
correct identification of the peaks.
Present and Future Work
 Beam energy correction with EPICS variables (thanks Ole)
 Optimized Coincidence Time calculation (thanks Rob)
 Data normalization (thanks Bob)
 Fine tuning of the RICH code
 optics database (thanks Doug and Yi)
 Beam incident angle, raster
Conclusions
We have just completed the data taking (yesterday)
 On-line results are promising. The 12C data seem confirm the data
from Hall C, The 9Be data show a interesting structure that
would confirm the expected spectrum
 Optics database optimized for missing mass reconstruction, the
obtained resolution on optics data is excellent
 We are presently working on the missing mass calculation, very
probably the present resolution is affected by a not optimized
correction on the beam energy value
 The analysis is continuously going forward, to obtain ‘publishable’
results ASAP (at least for my theses :-D).
THANKS
The experiment was proposed in 1994!
Now we have just ended the data taking and we
start to see nice results.
Many people have done a strong effort to realize it.
THANK YOU VERY MUCH !!!