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 18/07/2006 ICARUS Collaboration Meeting

ICARUS Collaboration Meeting 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 18/07/2006 ICARUS Collaboration Meeting

ICARUS Collaboration Meeting 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) 18/07/2006 ICARUS Collaboration Meeting

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 18/07/2006 ICARUS Collaboration Meeting

ICARUS Collaboration Meeting 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 18/07/2006 ICARUS Collaboration Meeting

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 18/07/2006 ICARUS Collaboration Meeting

ICARUS Collaboration Meeting 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. 18/07/2006 ICARUS Collaboration Meeting

ICARUS Collaboration Meeting Agreement criterium # 1 : main vertex position Dx = - 0.003 cm s = 0.367 cm Dy = - 0.038 cm s = 0.395 cm Dz = - 0.015 cm s = 0.252 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. 18/07/2006 ICARUS Collaboration Meeting

ICARUS Collaboration Meeting Agreement criterium # 2 : shower starting points Dx = - 0.085 cm s = 0.567 cm Dy = - 0.035 cm s = 0.389 cm Dz = - 0.018 cm s = 0.380 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. 18/07/2006 ICARUS Collaboration Meeting

ICARUS Collaboration Meeting 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 18/07/2006 ICARUS Collaboration Meeting

ICARUS Collaboration Meeting 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 18/07/2006 ICARUS Collaboration Meeting

ICARUS Collaboration Meeting 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 18/07/2006 ICARUS Collaboration Meeting

ICARUS Collaboration Meeting 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 18/07/2006 ICARUS Collaboration Meeting

ICARUS Collaboration Meeting gg invariant mass and p0 total energy: two shower events Ea ~ 400 MeV two shower events; sm/m < 15%; no charged tracks crossing. mgg = 128.0 ± 4.0 MeV/c2 RMS = 24.4 MeV/c2 18/07/2006 ICARUS Collaboration Meeting

ICARUS Collaboration Meeting 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 = 125.7 ± 3.7 MeV/c2 RMS = 25.7 MeV/c2 18/07/2006 ICARUS Collaboration Meeting

Reconstruction method has been validated through FLUKA simulation of events with p0 production in ICARUS T600 p0 gg (at rest) p- + 40Ar n + p0 + X (2 GeV) S0 p0 + p (at rest) 18/07/2006 ICARUS Collaboration Meeting

ICARUS Collaboration Meeting 60 gg systems from 2 GeV p- interactions in LAr gg systems from p0 at rest gg systems from S+ → p0 + p decay 18/07/2006 ICARUS Collaboration Meeting

ICARUS Collaboration Meeting 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 18/07/2006 ICARUS Collaboration Meeting

ICARUS Collaboration Meeting 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 18/07/2006 ICARUS Collaboration Meeting

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 18/07/2006 ICARUS Collaboration Meeting

Shower energy resolution (below 1 GeV) 142 showers: survived the agreement criteria; below 1 GeV; not crossed by charged tracks. 18/07/2006 ICARUS Collaboration Meeting

ICARUS Collaboration Meeting 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 18/07/2006 ICARUS Collaboration Meeting