Scintillator counters with WLS fiber/MPPC readout for the side muon range detector (SMRD)of the T2K experiment

The T2K neutrino experiment at J-PARC uses a set of near detectors to measure the properties of an unoscillated neutrino beam and neutrino interaction cross-sections. One of the sub-detectors of the near-detector complex, the side muon range detector (SMRD), is described in the paper. The detector is designed to help measure the neutrino energy spectrum, to identify background and to calibrate the other detectors. The active elements of the SMRD consist of 0.7 cm thick extruded scintillator slabs inserted into air gaps of the UA1 magnet yokes. The readout of each scintillator slab is provided through a single WLS fiber embedded into a serpentine shaped groove. Two Hamamatsu multi-pixel avalanche photodiodes (MPPC's) are coupled to both ends of the WLS fiber. This design allows us to achieve a high MIP detection efficiency of greater than 99%. A light yield of 25-50 p.e./MIP, a time resolution of about 1 ns and a spatial resolution along the slab better than 10 cm were obtained for the SMRD counters.Comment: 7 pages, 4 figures; talk at TIPP09, March 12-17, Tsukuba, Japan; to be published in the conference proceeding

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 of three-dimensional reconstruction for the LAr TPC with a practical application to 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 real data tracks collected during the ICARUS T600 detector operation with the CNGS neutrino beam.Comment: Submitted to Advances in High Energy Physic

Search for anomalies in the {\nu}e appearance from a {\nu}{\mu} beam

We report an updated result from the ICARUS experiment on the search for {\nu}{\mu} ->{\nu}e anomalies with the CNGS beam, produced at CERN with an average energy of 20 GeV and travelling 730 km to the Gran Sasso Laboratory. The present analysis is based on a total sample of 1995 events of CNGS neutrino interactions, which corresponds to an almost doubled sample with respect to the previously published result. Four clear {\nu}e events have been visually identified over the full sample, compared with an expectation of 6.4 +- 0.9 events from conventional sources. The result is compatible with the absence of additional anomalous contributions. At 90% and 99% confidence levels the limits to possible oscillated events are 3.7 and 8.3 respectively. The corresponding limit to oscillation probability becomes consequently 3.4 x 10-3 and 7.6 x 10-3 respectively. The present result confirms, with an improved sensitivity, the early result already published by the ICARUS collaboration

The T2K Side Muon Range Detector

The T2K experiment is a long baseline neutrino oscillation experiment aiming to observe the appearance of {\nu} e in a {\nu}{\mu} beam. The {\nu}{\mu} 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.Comment: 13 pages, 19 figures v2: fixed several typos; fixed reference

\Delta G/G results from the COMPASS experiment for Q^2 > 1 GeV^2, using high p_T hadrons

One of the goals of COMPASS experiment is the determination of the gluon polarisation, \Delta G/G, for a deep understanding of the spin structure of the nucleon. The gluon polarisation can be measured via the Photon-Gluon-Fusion (PGF) process. One of the methods to identify this process is selecting high p_T hadron pairs in the final state. The data used for this analysis were collected by the COMPASS experiment during the years 2002 to 2006, using a 160 GeV naturally polarised positive muon beam impinging on a polarised nucleon target. A new result of \Delta G/G from high p_T hadron pairs in events with Q^2>1 GeV^2 is presented. This result has a better precision due to the addition of 2006 data and an improved analysis based on a neural network approach. The gluon polarisation is also presented in three bins of x_G.Comment: Proceedings for SPIN2010 - 19th International Spin Physics Symposium September 27 - October 2, 2010, Juelich, German

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

The OPERA collaboration has claimed evidence of superluminal {\nu}{_\mu} propagation between CERN and the LNGS. Cohen and Glashow argued that such neutrinos should lose energy by producing photons and e+e- pairs, through Z0 mediated processes analogous to Cherenkov radiation. In terms of the parameter delta=(v^2_nu-v^2_c)/v^2_c, the OPERA result implies delta = 5 x 10^-5. For this value of \delta 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. Our results therefore refute a superluminal interpretation of the OPERA result according to the Cohen and Glashow prediction for a weak current analog to Cherenkov radiation. In particular no superluminal Cherenkov like e+e- pair or gamma 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 delta < 2.5 10^-8 at the 90% confidence level, comparable with the one due to the observations from the SN1987A.Comment: 17 pages, 6 figure

Experimental search for the LSND anomaly with the ICARUS detector in the CNGS neutrino beam

We report an early result from the ICARUS experiment on the search for nu_mu to nu_e signal due to the LSND anomaly. The search was performed with the ICARUS T600 detector located at the Gran Sasso Laboratory, receiving CNGS neutrinos from CERN at an average energy of about 20 GeV, after a flight path of about 730 km. The LSND anomaly would manifest as an excess of nu_e events, characterized by a fast energy oscillation averaging approximately to sin^2(1.27 Dm^2_new L/ E_nu) = 1/2. The present analysis is based on 1091 neutrino events, which are about 50% of the ICARUS data collected in 2010-2011. Two clear nu_e events have been found, compared with the expectation of 3.7 +/- 0.6 events from conventional sources. Within the range of our observations, this result is compatible with the absence of a LSND anomaly. At 90% and 99% confidence levels the limits of 3.4 and 7.3 events corresponding to oscillation probabilities of 5.4 10^-3 and 1.1 10^-2 are set respectively. The result strongly limits the window of open options for the LSND anomaly to a narrow region around (Dm^2, sin^2(2 theta))_new = (0.5 eV^2, 0.005), where there is an overall agreement (90% CL) between the present ICARUS limit, the published limits of KARMEN and the published positive signals of LSND and MiniBooNE Collaborations.Comment: 10 pages, 7 figure

Precision measurement of the neutrino velocity with the ICARUS detector in the CNGS beam

During May 2012, the CERN-CNGS neutrino beam has been operated for two weeks for a total of 1.8 10^17 pot in bunched mode, with a 3 ns narrow width proton beam bunches, separated by 100 ns. This tightly bunched beam structure allows a very accurate time of flight measurement of neutrinos from CERN to LNGS on an event-by-event basis. Both the ICARUS-T600 PMT-DAQ and the CERN-LNGS timing synchronization have been substantially improved for this campaign, taking ad-vantage of additional independent GPS receivers, both at CERN and LNGS as well as of the deployment of the "White Rabbit" protocol both at CERN and LNGS. The ICARUS-T600 detector has collected 25 beam-associated events; the corresponding time of flight has been accurately evaluated, using all different time synchronization paths. The measured neutrino time of flight is compatible with the arrival of all events with speed equivalent to the one of light: the difference between the expected value based on the speed of light and the measured value is tof_c - tof_nu = (0.10 \pm 0.67stat. \pm 2.39syst.) ns. This result is in agreement with the value previously reported by the ICARUS collaboration, tof_c - tof_nu = (0.3 \pm 4.9stat. \pm 9.0syst.) ns, but with improved statistical and systematic errors.Comment: 21 pages, 13 figures, 1 tabl

Underground operation of the ICARUS T600 LAr-TPC: first results

Open questions are still present in fundamental Physics and Cosmology, like the nature of Dark Matter, the matter-antimatter asymmetry and the validity of the particle interaction Standard Model. Addressing these questions requires a new generation of massive particle detectors exploring the subatomic and astrophysical worlds. ICARUS T600 is the first large mass (760 ton) example of a novel detector generation able to combine the imaging capabilities of the old famous "bubble chamber" with an excellent energy measurement in huge electronic detectors. ICARUS T600 now operates at the Gran Sasso underground laboratory, studying cosmic rays, neutrino oscillation and proton decay. Physical potentialities of this novel telescope are presented through few examples of neutrino interactions reconstructed with unprecedented details. Detector design and early operation are also reported.Comment: 14 pages, 8 figures, 2 tables. Submitted to Jins

Leading order determination of the gluon polarisation from DIS events with high-p_T hadron pairs

We present a determination of the gluon polarisation Delta g/g in the nucleon, based on the longitudinal double-spin asymmetry of DIS events with a pair of large transverse-momentum hadrons in the final state. The data were obtained by the COMPASS experiment at CERN using a 160 GeV/c polarised muon beam scattering off a polarised ^6LiD target. The gluon polarisation is evaluated by a Neural Network approach for three intervals of the gluon momentum fraction x_g covering the range 0.04 < x_g < 0.27. The values obtained at leading order in QCD do not show any significant dependence on x_g. Their average is Delta g/g = 0.125 +/- 0.060 (stat.) +/- 0.063 (syst.) at x_g=0.09 and a scale of mu^2 = 3 (GeV/c)^2.Comment: 13 pages, 6 figures and 3 table