K. Zaremba

Measurement of the proton and deuteron structure functions, F2p and F2d, and of the ratio sigmaL/sigmaT.

The muon-proton and muon-deuteron inclusive deep inelastic scattering cross sections were measured in the kinematic range 0.002 < x < 0.60 and 0.5 < Q(2) < 75 GeV2 at incident muon energies of 90, 120, 200 and 280 GeV. These results are based on the full data set collected by the New Muon Collaboration, including the data taken with a small angle trigger. The extracted values of the structure functions F-2(p) and F-2(d) are in good agreement with those from other experiments. The data cover a sufficient range of y to allow the determination of the ratio of the longitudinally to transversely polarised virtual photon absorption cross sections, R = sigma(L)/sigma(T), for 0.002 < x < 0.12. The values of R are compatible with a perturbative QCD prediction; they agree with earlier measurements and extend to smaller x.The muon-proton and muon-deuteron inclusive deep inelastic scattering cross sections were measured in the kinematic range 0.002<x<0.60 and 0.5<Q2<75 GeV2 at incident muon energies of 90, 120, 200 and 280 GeV. These results are based on the full data set collected by the New Muon Collaboration, including the data taken with a small angle trigger. The extracted values of the structure functions F2p and F2d are in good agreement with those from other experiments. The data cover a sufficient range of y to allow the determination of the ratio of the longitudinally to transversely polarised virtual photon absorption cross sections, R= sigma(L)/sigma(T), for 0.002<x<0.12 . The values of R are compatible with a perturbative QCD prediction; they agree with earlier measurements and extend to smaller x.

Characterization and Simulation of the Response of Multi Pixel Photon Counters to Low Light Levels

The calorimeter, range detector and active target elements of the T2K near detectors rely on the Hamamatsu Photonics Multi-Pixel Photon Counters (MPPCs) to detect scintillation light produced by charged particles. Detailed measurements of the MPPC gain, afterpulsing, crosstalk, dark noise, and photon detection efficiency for low light levels are reported. In order to account for the impact of the MPPC behavior on T2K physics observables, a simulation program has been developed based on these measurements. The simulation is used to predict the energy resolution of the detector.

The Q2 dependence of the structure function ratio F2Sn/F2C and the difference RSn - RC in deep inelastic muon scattering

The Q(2) dependence of the structure function ratio F-2(Sn)/F-2(C) for 0.01 < x < 0.75 and 1 < Q(2) < 140 GeV2 is reported. For x < 0.1 the size of shadowing decreases linearly with In Q(2) and the maximum rate is about 0.04 at x = 0.01. The rate decreases with x and is compatible with zero for x greater than or equal to 0.1. The difference R(Sn) - R(C), where R is the ratio of longitudinally to transversely polarised virtual photon absorption cross sections, is also given. No dependence on x is seen and the average value is 0.040 +/- 0.021 (stat.) +/- 0.026 (syst.) at a mean Q(2) of 10 GeV2.

A search for the analogue to Cherenkov radiation by high energy neutrinos at superluminal speeds in ICARUS

Abstract The OPERA Collaboration (2011) [1] has reported evidence of superluminal ν μ propagation between CERN and the LNGS. Cohen and Glashow (2011) [2] argued that such neutrinos should lose energy by producing photons and e + e − pairs, through Z 0 mediated processes analogous to Cherenkov radiation. In terms of the parameter δ ≡ ( v ν 2 − v c 2 ) / v c 2 , the OPERA result corresponds to δ ≈ 5 ⋅ 10 − 5 . For this value (note that ( v ν − v c ) / v c ≈ δ 2 ≈ 2.5 ⋅ 10 − 5 ) of δ , a very significant deformation of the neutrino energy spectrum and an abundant production of photons and e + e − pairs should be observed at LNGS. We present an analysis based on the 2010 and part of the 2011 data sets from the ICARUS experiment, located at Gran Sasso National Laboratory and using the same neutrino beam from CERN. We find that the rates and deposited energy distributions of neutrino events in ICARUS agree with the expectations for an unperturbed spectrum of the CERN neutrino beam, as also reported by OPERA. Our results therefore refute a superluminal interpretation of the OPERA result according to the Cohen and Glashow (2011) prediction [2] for a weak current analog to Cherenkov radiation. In a dedicated search, no superluminal Cherenkov-like e + e − pair or γ emission event has been directly observed inside the fiducial volume of the “bubble chamber-like” ICARUS TPC-LAr detector, setting the much stricter limit of δ 2.5 ⋅ 10 − 8 at the 90% confidence level, comparable with the one due to the observations from the SN1987a (M.J. Longo, 1987 [4] ). The observations of high energy neutrino events by Super-Kamiokande and IceCube are also pointing to a much stricter limit on δ .

The T2K Side Muon Range Detector (SMRD)

The T2K experiment is a long baseline neutrino oscillation experiment aiming to observe the appearance ofe in a �µ beam. The �µ beam is produced at the Japan Proton Accelerator Research Complex (J-PARC), observed with the 295 km distant Super- Kamiokande Detector and monitored by a suite of near detectors at 280m from the proton target. The near detectors include a magnetized off-axis detector (ND280) which measures the un-oscillated neutrino flux and neutrino cross sections. The present paper describes the outermost component of ND280 which is a side muon range detector (SMRD) composed of scintillation counters with embedded wavelength shifting fibers and Multi-Pixel Photon Counter read-out. The components, performance and response of the SMRD are presented.

Precise 3D Track Reconstruction Algorithm for the ICARUS T600 Liquid Argon Time Projection Chamber Detector

Liquid Argon Time Projection Chamber (LAr TPC) detectors offer charged particle imaging capability with remarkable spatial resolution. Precise event reconstruction procedures are critical in order to fully exploit the potential of this technology. In this paper we present a new, general approach to 3D reconstruction for the LAr TPC with a practical application to the track reconstruction. The efficiency of the method is evaluated on a sample of simulated tracks. We present also the application of the method to the analysis of stopping particle tracks collected during the ICARUS T600 detector operation with the CNGS neutrino beam.

ICARUS at FNAL

The INFN and the ICARUS collaboration originally developed the technology of the LAr-TPC. Located the underground LNGS Hall-B, the ICARUS T600 detector has been performed over three years with remarkable detection efficiency featuring a smooth operation, high live time, and high reliability. About 3000 CNGS neutrino events have been collected and are being actively analyzed. ICARUS will now be moved to CERN for an extensive RD the T150 will be located at ~150 m. The T600 will also receive >10^4 nu_e events/year from the off-axis NUMI beam peaked around 1 GeV and exploitable to prepare for the LBNE experiment. The ICARUS teams are also interested in extending the participation to other short baseline neutrino activities collaborating with existing FNAL groups.

Experimental observation of an extremely high electron lifetime with the ICARUS-T600 LAr-TPC

The ICARUS T600 detector, the largest liquid Argon Time Projection Chamber (LAr-TPC) realized after many years of R&D activities, was installed and successfully operated for 3 years at the INFN Gran Sasso underground Laboratory. One of the most important issues was the need of an extremely low residual electronegative impurity content in the liquid Argon, in order to transport the free electrons created by ionizing particles with very small attenuation along the drift path. The solutions adopted for the Argon recirculation and purification systems have permitted to reach impressive results in terms of Argon purity and a free electron lifetime exceeding 15 ms, corresponding to about 20 parts per trillion of O2-equivalent contamination, a milestone for any future project involving LAr-TPCs and the development of higher detector mass scales.

Self-Organising maps for classification with metropolis-hastings algorithm for supervision

Self-Organising Maps (SOM) provide a method of feature mapping from multi-dimensional space to a usually two-dimensional grid of neurons in an unsupervised way. This way of data analysis has been proved as an efficient tool in many applications. SOM presented by T.Kohonen originally were unsupervised learning algorithm, however it is often used in classification problems. This paper introduces novel method for supervised learning of the SOM. It is based on neurons class membership and Metropolis-Hastings algorithm, which control networks learning process. This approach is illustrated by performing recognition tasks on nine real data sets, such as: faces, written digits or spoken letters. Experimental results show improvements over the state-of-art methods for using SOM as classifier.

The trigger system of the ICARUS experiment for the CNGS beam

The ICARUS T600 detector, with its 470 tons of active mass, is the largest liquid Argon TPC ever built. Operated for three years in the LNGS underground laboratory, it has collected thousands of CNGS neutrino beam interactions and cosmic ray events with energy spanning from tens of MeV to tens of GeV, with a trigger system based on scintillation light, charge signal on TPC wires and time information (for beam related events only). The performance of trigger system in terms of efficiency, background and live-time as a function of the event energy for the CNGS data taking is presented.