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

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

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

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

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

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

Associated production of h0 and p0 Run 975 event 65 Right Chamber Associated production of h0 and p0 Measured masses are: m (g1g2) = 551.2 ± 66.1 MeV/c2 m (g3g4) = 131.6 ± 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

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

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

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

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

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

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

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

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

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

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

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

A. Menegolli - University of Pavia and INFN Pavia Real events <mp0> = 135.0 ± 8.2 MeV/c2 p0 mass (MeV/c2) 23/07/2004 A. Menegolli - University of Pavia and INFN Pavia

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

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

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