1. p0 detection and reconstruction with the
ICARUS Collaboration Meeting
LNGS, 18/07/06
p0 detection and reconstruction with the
ICARUS T600 LAr TPC: final results
G. Battistoni, R. Brunetti, K. Cieślik, A. Dąbrowska, R. Dolfini,
Gigli Berzolari, J. Holeczek, J. Kisiel, J. Lagoda, M. Markiewicz,
F. Mauri, A. Menegolli, P. Mijakowski, T. Palczewski, A. Piazzoli,
A. Rappoldi, G.L. Raselli, E. Rondio, J. Stepaniak, M. Szarska, A. Zalewska
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Contents
Motivations
Search for hadronic interactions with neutral meson production: scanning and reconstruction methods
Final results from ICARUS T300 data
Simulations of neutrino interactions with p0 production
E.m. shower energy resolution
Conclusions
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Motivations
Study the capability of T600 detector to identify neutral pions
and reconstruct their mass through real event analysis (surface
Pavia run)
Study the performance of T600 detector in reconstructing
electromagnetic shower of several hundreds MeV (coming from
the photons of p0 decay)
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4. Scanning rules for hadronic events with neutral meson production: a reminder
An interaction with a clear main vertex in three views is searched;
The main vertex is defined by two charged tracks (at least) converging
to the same point;
Two photons (at least) must be present, generating clear e.m. showers
pointing to the main vertex in Collection view and in one of the two
Induction views;
Drift time coordinate
Wire coordinate (3mm pitch)
All runs from ETH list including hadronic interactions have been scanned, for a total of ~ 7500 images analyzed
The result of the scanning was a pre-selection
of ~ 570 neutral meson candidates
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Reconstruction tools
Identification of all hits belonging to a shower
Hit finding and reconstruction in Collection View
Deposited energy reconstruction
g direction reconstruction through association of
Collection and Induction views
Evaluation of invariant mass of gg system
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6. Measurement of (g,g) systems
For the evaluation of the invariant mass Mgg of (g,g) systems are needed:
The two shower energies, E1 and E2
The angle q12 between the two showers
The angle q12 is computed from the coordinate of the main vertex
of the interaction and from the starting points of the two showers
Shower energy is given by:
C = calibration factor converting from
ADC to MeV (after MC simulations)
Ak = k-th hit area in ADC counts
e(tk-t0/te) = correction for drift electron
finite life time te
1+kQ(dE/dx) = electron-ion recombination
factor (Birks’ law)
Hits inside the green polygonal line only
are selected for energy reconstruction
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ICARUS T300 data analysis
The four labs involved in the analysis (Katowice, Krakow, Pavia, Warsaw) have collected ~ 570 events of hadronic interactions with production of at least two e.m. showers.
The number of such events that it was possible to measure twice independently with the newest version of the software is ~ 250.
Criteria of agreement between two different measurements of the same event were studied and applied to the data.
The final sample of ‘good’ events is built after the averaging of main vertex
and shower coordinates and shower energies of events who survived the
agreement criteria.
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Agreement criterium # 1 : main vertex position
Dx = cm
s = cm
Dy = cm
s = cm
Dz = cm
s = cm
If differences between main vertex coordinates independently measured are
within the average difference ± 5 s, then main vertexes are considered to be
in agreement, otherwise the event is rejected.
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Agreement criterium # 2 : shower starting points
Dx = cm
s = cm
Dy = cm
s = cm
Dz = cm
s = cm
If differences between shower vertex coordinates independently measured are within the average difference ± 5 s, then shower vertexes are considered to be in agreement, otherwise the event is rejected.
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LAr radiation length evaluation
After the agreement on coordinates, the distribution of the distances
of the shower starting point from the main vertex of the hadronic
interaction has been built:
X0 = (17.5 ± 1.2) cm
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X-distribution of hadronic interaction verteces
The distribution of hadronic
vertexes along X (vertical) coordinate is related to the LAr interaction length
141 events
Top of T300
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Agreement criterium # 3 : shower energy
If the relative difference is larger
than 0.5 (absolute value) the event
is rejected
DE = 0.2 MeV
s = 3.4 MeV
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More event rejection criteria
After the agreement criteria rejections, two more
cuts were applied to get the final database:
Rejection of events belonging to the ‘Bad Sector’
of the Right Chamber of T300: it is required that
at least the first 90 cm (~ 6 X0) of a shower are
outside the bad sector;
2. Rejection of events in which single charged tracks
crossed at least one of the e.m. showers.
Fiducial volume cuts are going to be included: it will be
required that at least the first 90 cm (~ 6 X0) of a shower
are fully visible in the event selected view
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gg invariant mass and p0 total energy: two shower events
Ea ~ 400 MeV
two shower events;
sm/m < 15%;
no charged tracks crossing.
mgg = ± 4.0 MeV/c2
RMS = 24.4 MeV/c2
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gg invariant mass and p0 total energy: add multi-shower events
Ea ~ 370 MeV
two + multi-shower events;
sm/m < 15%;
no charged tracks crossing;
proper g pair disentangled from
c square analysis.
mgg = ± 3.7 MeV/c2
RMS = 25.7 MeV/c2
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16. Reconstruction method has been validated through FLUKA simulation
of events with p0 production in ICARUS T600
p gg (at rest)
p- + 40Ar n + p0 + X (2 GeV)
S p0 + p (at rest)
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60 gg systems from 2 GeV
p- interactions in LAr
gg systems from p0 at rest
gg systems from S+ → p0 + p decay
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Other MC-FLUKA simulations: photons and electrons
1. Photons
2. Electrons
Number of events
Angle  ()
Angle  ()
<Energy> (MeV)
RMS
EMC/<E>
1. Photon – 50 MeV 10 60
120 49 2
1,02 ± 0,06
2. Photon – 100 MeV 45 99 5
1,01 ± 0,06 30 90 96 4
1,04 ± 0,04 64
116
100
1,00 ± 0,03 98
1,02 ± 0,03
180
3. Photon – 300 MeV
292 9
1,03 ± 0,02
4. Photon– 1000 MeV
994 22
1,01 ± 0,02
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Simulation of p0 production in neutrino interactions
p0 production from NC muon neutrino interaction in the T600 was simulated using NUX-FLUKA chain of programs.
Inc. energy 1 2 3 4 5 6
1 GeV 86 11
2 GeV 80 17
5 GeV 56 30
17 GeV 36 38 18
Multiplicity from primary vertex
100 events per incident energy
Incident energy
# of p0 from primary interaction
# of p0 from secondary interaction
1 GeV 17
2 GeV 24 32
5 GeV 62
106
17 GeV
102
324
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20. gg invariant mass plots
Two photon 1.0, 1.5, 2.0 and 2.5 GeV
muon neutrino NC interaction
Two photon 5 GeV
muon neutrino NC interaction
h0 correctly reconstructed
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21. Shower energy resolution (below 1 GeV)
142 showers:
survived the agreement criteria;
below 1 GeV;
not crossed by charged tracks.
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Conclusions
The analysis of p0 events in T600 is almost finished: scanning and measurements are concluded.
Reconstruction tools were validated through MC-FLUKA simulations
of several typologies of events with p0 production.
The analysis demonstrates that with the LAr TPC technology it is possible to well reconstruct e.m. shower energies and p0 mass, also in the difficult conditions of a surface run
The draft zero of this work is going to be submitted to the Collaboration in sight of a future publication
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