1. ICARUS T600: preliminary analysis of cosmic ray induced interactions with neutral meson production
A. Menegolli, University of Pavia and INFN Pavia
ICARUS LNGS, 23/07/2004
23/07/2004
A. Menegolli - University of Pavia and INFN Pavia

2. A. Menegolli - University of Pavia and INFN Pavia
Involved people
23/07/2004
A. Menegolli - University of Pavia and INFN Pavia

3. A. Menegolli - University of Pavia and INFN Pavia
Contents
Search for hadronic interaction with neutral meson production
Calorimetric reconstruction of e.m. showers with ANATRA program
Montecarlo FLUKA calibration
Preliminary results from ICARUS T600 data
Conclusions
23/07/2004
A. Menegolli - University of Pavia and INFN Pavia

4. Scanning of hadronic events with meson production
These kind of events are identified using Qscan, with the following
scanning rules:
An interaction with a clear vertex in three views is searched;
The vertex is defined by two tracks (at least) converging
in the same point;
Two gammas (at least) must be present, generating clear showers
pointing to the interaction vertex in three views (note that one of the
two showers can be just an e+e- pair);
If just one charged track is present, the additional presence of a short,
highly ionising proton, attached to the track end point, must be carefully
checked. If not, the event must be rejected.
23/07/2004
A. Menegolli - University of Pavia and INFN Pavia

5. A. Menegolli - University of Pavia and INFN Pavia
Run 975 event 100
Right Chamber
t (cm) p
g1, g2
Induction 2 view
u (cm)
23/07/2004
A. Menegolli - University of Pavia and INFN Pavia

6. A. Menegolli - University of Pavia and INFN Pavia
Run 975 event 44
Left Chamber
t (cm)
g1,g2 ,g3
Main vertex
u (cm)
23/07/2004
A. Menegolli - University of Pavia and INFN Pavia

7. Associated production of h0 and p0
Run 975 event 65
Right Chamber
Associated production of h0 and p0
Measured masses are:
m (g1g2) = ± 66.1 MeV/c2
m (g3g4) = ± 15.4 MeV/c2
consistent with the hypothesis of h0
and p0 associated production
23/07/2004
A. Menegolli - University of Pavia and INFN Pavia

8. A. Menegolli - University of Pavia and INFN Pavia
Reconstruction tools
Hit finding and reconstruction
Identification of all hits belonging to a shower
Deposited energy reconstruction
g direction reconstruction
Evaluation of invariant mass of gg system
23/07/2004
A. Menegolli - University of Pavia and INFN Pavia

9. A. Menegolli - University of Pavia and INFN Pavia
ANATRA program
ANATRA (ANAlysis of TRAcks) allows to display views of events selected with Qscan, and to make energy-range analysis of tracks and calorimetric reconstruction of e.m. showers.
23/07/2004
A. Menegolli - University of Pavia and INFN Pavia

10. Hit finding and reconstruction
Hit search is performed by ANATRA program on raw signals,
not filtered to avoid signal distortion;
The hit finding and reconstruction algorithms follow
the strategy developed by Qscan (see ICARUS-TM-2002/03);
The baseline of signal is computed as the mean value
between the local means at the two sides of the hit;
For calorimetric measurements two parameters are needed:
a) peak position: assigned to the maximum output sample;
b) hit area : evaluated as the sum of the ADC counts of the
samples belonging to the hit (baseline subtracted).
23/07/2004
A. Menegolli - University of Pavia and INFN Pavia

11. Shower identification
t (cm)
Hits inside the green polygonal
line only are selected for energy
reconstruction. It is really mandatory to select manually the region of shower hits when measuring real events
indicates a reconstructed hit
in Collection view.
u (cm)
23/07/2004
A. Menegolli - University of Pavia and INFN Pavia

12. Energy reconstruction
The energy of hits belonging to recognized e.m. showers is computed by:
This formula accounts for ADC to MeV conversion, actual electron
lifetime in LAr and recombination factors.
23/07/2004
A. Menegolli - University of Pavia and INFN Pavia

13. A. Menegolli - University of Pavia and INFN Pavia
AREA is the hit area, evaluated in ADC counts over the hit baseline;
B = 2.242·10-3 MeV/ADC (±3%) is the conversion from ADC to MeV;
t is the hit time coordinate (from hit reconstruction);
t0 is the event zero-time (see later for its determination);
te is the actual electron lifetime in LAr, depending on run number;
is the Birks’ law factor for electron-ion recombination:
dE/dx for shower electrons is assumed to be on average
2.4 ± 0.3 MeV/cm (from measurements on Michel electrons);
kQ was measured to be kQ = 0.11±0.01 (g/cm2)/MeV;
A is a normalization factor evaluated through a Montecarlo
analysis.
23/07/2004
A. Menegolli - University of Pavia and INFN Pavia

14. Measurement of g direction
The direction of the g’s from neutral meson decay is assumed to be
the one pointing from the hadronic interaction vertex to the starting
point of the e.m. showers (usually the vertex of the e+e- pair closest
to the main vertex).
The space coordinates of the main vertex and of the starting points
of the e.m. showers are selected by the user directly from the display
of ANATRA program (Collection and Induction I/II).
Then the angle q12 between two selected e.m. showers is measured
from the versors of the two g’s.
The invariant mass of the gg system can now be calculated as:
23/07/2004
A. Menegolli - University of Pavia and INFN Pavia

15. A. Menegolli - University of Pavia and INFN Pavia
FLUKA samples for energy calibration
Three samples of Montecarlo data were used for calibration:
p0 decay at rest
p0 from S0 decay at rest
p0 produced in p- nuclear interaction in LAr (2 and 2.5 GeV)
The energy calibration factor was extracted and implemented
in ANATRA program.
23/07/2004
A. Menegolli - University of Pavia and INFN Pavia

16. A. Menegolli - University of Pavia and INFN Pavia
Sample coming from
p- interaction in LAr
23/07/2004
A. Menegolli - University of Pavia and INFN Pavia

17. A. Menegolli - University of Pavia and INFN Pavia
23/07/2004
A. Menegolli - University of Pavia and INFN Pavia

18. Preliminary analysis with real data
Scanning and measurements were done in three laboratories indipendently
The total number of real events collected and measured
untill now is 47.
For events measured indipendently in at least two
laboratories the average value of the mass was used
for invariant mass distribution
30 additional candidate events are currently under analysis
23/07/2004
A. Menegolli - University of Pavia and INFN Pavia

19. A. Menegolli - University of Pavia and INFN Pavia
Real events
<mp0> = ± 8.2 MeV/c2
p0 mass (MeV/c2)
23/07/2004
A. Menegolli - University of Pavia and INFN Pavia

20. t0 determination
The presence of the event zero-time is mandatory !!! But it can be
determined just in the following cases:
tracks intersecting wire plane (“whip effect” and/or “iso-strip”
signals);
many tracks intersecting cathode at the same drift time
(t0 = 962 ms – tendpoint);
one track intersecting cathode (but it must be visible in the
adjacent chamber);
energy-range calibration with ANATRA (from a clean electron
track produced in the e.m. shower).
23/07/2004
A. Menegolli - University of Pavia and INFN Pavia

21. A. Menegolli - University of Pavia and INFN Pavia
Measurement prescriptions
The method of measurement (“draw a polygonal line around
the shower”) implies some care by the user in:
excluding crossing tracks and other background hits;
2) drawing the line as close as possible to the shower boundary
in order to avoid the presence of fitted spurious hits.
23/07/2004
A. Menegolli - University of Pavia and INFN Pavia

22. A. Menegolli - University of Pavia and INFN Pavia
Conclusions
Preliminary analysis of some real candidate events with neutral
mesons production makes confident in the reliability of the used
methods of e.m. shower methods.
The collection of a higher statistics is now in progress in order to
reduce statistical errors and to better evaluate the performance
of ANATRA program routines with more real events.
Some routines for a more automatic reconstruction of the shower
parameters are currently under study.
Everyone interested in this kind of analysis is welcome!
23/07/2004
A. Menegolli - University of Pavia and INFN Pavia