ICARUS Collaboration Meeting LNGS 180706 p 0 detection

ICARUS Collaboration Meeting LNGS, 18/07/06 p 0 detection and reconstruction with the ICARUS T 600 LAr TPC: final results G. Battistoni, R. Brunetti, K. Cieślik, A. Dąbrowska, R. Dolfini, A. Gigli Berzolari, J. Holeczek, J. Kisiel, J. Lagoda, M. Markiewicz, B. F. Mauri, A. Menegolli, P. Mijakowski, T. Palczewski, A. Piazzoli, C. A. Rappoldi, G. L. Raselli, E. Rondio, J. Stepaniak, M. Szarska, A. Zalewska 18/07/2006 ICARUS Collaboration Meeting 1

Contents q Motivations q Search for hadronic interactions with neutral meson production: scanning and reconstruction methods q Final results from ICARUS T 300 data q Simulations of neutrino interactions with p 0 production q E. m. shower energy resolution q Conclusions 18/07/2006 ICARUS Collaboration Meeting 2

Motivations Ø Study the capability of T 600 detector to identify neutral pions and reconstruct their mass through real event analysis (surface Pavia run) Ø Study the performance of T 600 detector in reconstructing electromagnetic shower of several hundreds Me. V (coming from the photons of p 0 decay) 18/07/2006 ICARUS Collaboration Meeting 3

Drift time coordinate Scanning rules for hadronic events with neutral meson production: a reminder ü An interaction with a clear main vertex in three views is searched; ü The main vertex is defined by two charged tracks (at least) converging to the same point; ü 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; Wire coordinate (3 mm pitch) The result of the a pre-selection All runs from ETH listscanning includingwas hadronic interactions of ~ 570 for neutral meson candidates have been scanned, a total of ~ 7500 images analyzed 18/07/2006 ICARUS Collaboration Meeting 4

Reconstruction tools Ø Identification of all hits belonging to a shower Ø Hit finding and reconstruction in Collection View Ø Deposited energy reconstruction Ø g direction reconstruction through association of Collection and Induction views Ø Evaluation of invariant mass of gg system 18/07/2006 ICARUS Collaboration Meeting 5

Measurement of (g, g) systems For the evaluation of the invariant mass Mgg of (g, g) systems are needed: 1. The two shower energies, E 1 and E 2 2. The angle 12 between the two showers The angleenergy 12 is computed of factor the main vertexfrom C = calibration converting Shower is given by: from the coordinate to Me. V (after simulations) of the interaction and from the starting. ADC points of the two. MC showers Hits inside the green polygonal line only are selected for energy reconstruction Ak = k-th hit area in ADC counts e(tk-t 0/te) = correction for drift electron finite life time te 1+k. Q(d. E/dx) = electron-ion recombination factor (Birks’ law) 18/07/2006 ICARUS Collaboration Meeting 6

ICARUS T 300 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 7

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 8

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 9

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: ± 18/07/2006 X 0 = (17. 5 ± 1. 2) cm ICARUS Collaboration Meeting 10

X-distribution of hadronic interaction verteces 141 events The distribution of hadronic vertexes along X (vertical) coordinate is related to the LAr interaction length Top of T 300 18/07/2006 ICARUS Collaboration Meeting 11

Agreement criterium # 3 : shower energy DE = 0. 2 Me. V s = 3. 4 Me. V 18/07/2006 If the relative difference is larger than 0. 5 (absolute value) the event is rejected ICARUS Collaboration Meeting 12

More event rejection criteria After the agreement criteria rejections, two more cuts were applied to get the final database: 1. Rejection of events belonging to the ‘Bad Sector’ of the Right Chamber of T 300: it is required that at least the first 90 cm (~ 6 X 0) 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 X 0) of a shower are fully visible in the event selected view 18/07/2006 ICARUS Collaboration Meeting 13

gg invariant mass and p 0 total energy: two shower events Ea ~ 400 Me. V - two shower events; - sm/m < 15%; - no charged tracks crossing. 18/07/2006 mgg = 128. 0 ± 4. 0 Me. V/c 2 RMS = 24. 4 Me. V/c 2 ICARUS Collaboration Meeting 14

gg invariant mass and p 0 total energy: add multi-shower events Ea ~ 370 Me. V - two + multi-shower events; - sm/m < 15%; - no charged tracks crossing; - proper g pair disentangled from c square analysis. 18/07/2006 mgg = 125. 7 ± 3. 7 Me. V/c 2 RMS = 25. 7 Me. V/c 2 ICARUS Collaboration Meeting 15

Reconstruction method has been validated through FLUKA simulation of events with p 0 production in ICARUS T 600 p 0 gg (at rest) p- + 40 Ar S 0 18/07/2006 n + p 0 + X (2 Ge. V) p 0 + p (at rest) ICARUS Collaboration Meeting 16

60 gg systems from 2 Ge. V p- interactions in LAr gg systems from p 0 at rest gg systems from S+ → p 0 + p decay 18/07/2006 ICARUS Collaboration Meeting 17

Other MC-FLUKA simulations: photons and electrons 1. 2. Photons Electrons Angle ( ) <Energy> (Me. V) RMS EMC/<E> 60 120 49 2 1, 02 ± 0, 06 45 60 120 99 5 1, 01 ± 0, 06 10 30 90 96 4 1, 04 ± 0, 04 10 64 116 100 5 1, 00 ± 0, 03 10 0 60 98 5 1, 02 ± 0, 03 10 120 180 96 4 1, 04 ± 0, 04 60 120 292 9 1, 03 ± 0, 02 60 120 994 22 1, 01 ± 0, 02 Number of events 1. Photon – 50 Me. V 10 2. Photon – 100 Me. V 3. Photon – 300 Me. V 10 4. Photon– 1000 Me. V 10 18/07/2006 ICARUS Collaboration Meeting 18

Simulation of p 0 production in neutrino interactions p 0 production from NC muon neutrino interaction in the T 600 was simulated using NUX-FLUKA chain of programs. Inc. energy 0 1 2 1 Ge. V 86 11 3 2 Ge. V 80 17 2 1 5 Ge. V 56 30 11 2 1 17 Ge. V 36 38 18 4 1 18/07/2006 3 4 5 6 Multiplicity from primary vertex 100 events per incident energy 0 2 Incident energy # of p 0 from primary interaction # of p 0 from secondary interaction 1 Ge. V 17 17 2 Ge. V 24 32 5 Ge. V 62 106 17 Ge. V 102 324 ICARUS Collaboration Meeting 19

gg invariant mass plots Two photon 1. 0, 1. 5, 2. 0 and 2. 5 Ge. V muon neutrino NC interaction Two photon 5 Ge. V muon neutrino NC interaction h 0 correctly reconstructed 18/07/2006 ICARUS Collaboration Meeting 20

Shower energy resolution (below 1 Ge. V) 142 showers: - survived the agreement criteria; - below 1 Ge. V; - not crossed by charged tracks. 18/07/2006 ICARUS Collaboration Meeting 21

Conclusions The analysis of p 0 events in T 600 is almost finished: scanning and measurements are concluded. Reconstruction tools were validated through MC-FLUKA simulations of several typologies of events with p 0 production. The analysis demonstrates that with the LAr TPC technology it is possible to well reconstruct e. m. shower energies and p 0 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 22