A. Guglielmi

We have constructed and operated the ICARUS T600 liquid argon (LAr) time projection chamber (TPC). The ICARUS T600 detector is the largest LAr TPC ever built, with a size of about 500tons of fully imaging mass. The design and assembly of the detector relied on industrial support and represents the applications of concepts matured in laboratory tests to the kton scale. The ICARUS T600 was commissioned for a technical run that lasted about 3 months. During this period all the detector features were extensively tested with an exposure to cosmic-rays at surface with a resulting data collection of about 30 000 events. The detector was developed as the first element of a modular design. Thanks to the concept of modularity, it will be possible to realize a detector with several ktons active mass, to act as an observatory for astroparticle and neutrino physics at the Gran Sasso Underground Laboratory and a second-generation nucleon decay experiment. In this paper a description of the ICARUS T600 is given, detailing its design specifications, assembly procedures and acceptance tests. Commissioning procedures and results of the technical run are also reported, as well as results from the off-line event reconstruction.

We have studied the muon neutrino and antineutrino quasi-elastic (QEL) scattering reactions (ν μ n→μ − p and $\bar{\nu }_{\mu}p\to\mu^{+}n$ ) using a set of experimental data collected by the NOMAD Collaboration. We have performed measurements of the cross-section of these processes on a nuclear target (mainly carbon) normalizing it to the total ν μ ( $\bar{\nu}_{\mu}$ ) charged-current cross section. The results for the flux-averaged QEL cross sections in the (anti)neutrino energy interval 3–100 GeV are $\langle \sigma_{\mathrm{qel}}\rangle_{\nu_{\mu}}=(0.92\pm0.02(\mathrm{stat})\pm0.06(\mathrm{syst}))\times10^{-38}~\mathrm{cm}^{2}$ and $\langle\sigma_{\mathrm{qel}}\rangle_{\bar{\nu}_{\mu}}=(0.81\pm0.05(\mathrm{stat})\pm0.09(\mathrm{syst}))\times10^{-38}~\mathrm{cm}^{2}$ for neutrino and antineutrino, respectively. The axial mass parameter M A was extracted from the measured quasi-elastic neutrino cross section. The corresponding result is M A =1.05±0.02(stat)±0.06(syst) GeV. It is consistent with the axial mass values recalculated from the antineutrino cross section and extracted from the pure Q 2 shape analysis of the high purity sample of ν μ quasi-elastic 2-track events, but has smaller systematic error and should be quoted as the main result of this work. Our measured M A is found to be in good agreement with the world average value obtained in previous deuterium filled bubble chamber experiments. The NOMAD measurement of M A is lower than those recently published by K2K and MiniBooNE Collaborations. However, within the large errors quoted by these experiments on M A , these results are compatible with the more precise NOMAD value.

We present the results of a search for νμ→νe oscillations in the NOMAD experiment at CERN. The experiment looked for the appearance of νe in a predominantly νμ wide-band neutrino beam at the CERN SPS. No evidence for oscillations was found. The 90% confidence limits obtained are Δm2<0.4 eV2 for maximal mixing and sin2(2θ)<1.4×10−3 for large Δm2. This result excludes the LSND allowed region of oscillation parameters with Δm2≳10 eV2.

This white paper addresses the hypothesis of light sterile neutrinos based on recent anomalies observed in neutrino experiments and the latest astrophysical data.

Important 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 Standard Model of particle interactions. Addressing these questions requires a new generation of massive particle detectors to explore the subatomic and astrophysical worlds. ICARUS T600 is the first large mass (760 tons) example of a new generation of detectors able to combine the imaging capabilities of the old famous ``bubble chamber'' with the excellent energy measurement of huge electronic detectors. ICARUS T600 now operates at the Gran Sasso underground laboratory and is used to study cosmic rays, neutrino oscillations and the proton decay. The potential for doing physics of this novel telescope is presented through a few examples of neutrino interactions reconstructed with unprecedented detail. Detector design and early operation are also reported.

The NOMAD experiment is a short base-line search for νμ − ντ oscillations in the CERN neutrino beam. The ντ's are searched for through their charged current interactions followed by the observation of the resulting τ− through its electronic, muonic or hadronic decays. These decays are recognized using kinematical criteria necessitating the use of a light target which enables the reconstruction of individual particles produced in the neutrino interactions. This paper describes the various components of the NOMAD detector: the target and muon drift chambers, the electromagnetic and hadronic calorimeters, the preshower and transition radiation detectors and the veto and trigger scintillation counters. The beam and data acquisition system are also described. The quality of the reconstruction and individual particles is demonstrated through the ability of NOMAD to observe Ks0's, Λ0's and π0's. Finally, the observation of τ− through its electronic decay being one of the most promising channels in the search, the identification of electrons in NOMAD is discussed.

We report an early result from the ICARUS experiment on the search for a ν μ →ν 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 ∼730 km. The LSND anomaly would manifest as an excess of ν e events, characterized by a fast energy oscillation averaging approximately to $\sin^{2}(1.27\Delta m^{2}_{\mathrm{new}}L/E_{\nu})\approx 1/2$ with probability $P_{\nu_{\mu}\rightarrow \nu_{e}} = 1/2 \sin^{2}(2\theta_{\mathrm{new}})$ . The present analysis is based on 1091 neutrino events, which are about 50 % of the ICARUS data collected in 2010–2011. Two clear ν 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 $\langle P_{\nu_{\mu}\rightarrow \nu_{e}}\rangle \le 5.4 \times 10^{-3}$ and $\langle P_{\nu_{\mu}\rightarrow \nu_{e}}\rangle \le 1.1 \times 10^{-2} $ are set respectively. The result strongly limits the window of open options for the LSND anomaly to a narrow region around (Δm 2,sin2(2θ))new=(0.5 eV2,0.005), 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.

We report an updated result from the ICARUS experiment on the search for ν μ →ν e anomalies with the CNGS beam, produced at CERN with an average energy of 20 GeV and traveling 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 ν 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 3.4×10−3 and 7.6×10−3, respectively. The present result confirms, with an improved sensitivity, the early result already published by the ICARUS Collaboration.

We report on a search for heavy neutrinos ($\nus$) produced in the decay $D_s\to τ\nus$ at the SPS proton target followed by the decay $\nudecay$ in the NOMAD detector. Both decays are expected to occur if $\nus$ is a component of $ν_τ$.\ From the analysis of the data collected during the 1996-1998 runs with $4.1\times10^{19}$ protons on target, a single candidate event consistent with background expectations was found. This allows to derive an upper limit on the mixing strength between the heavy neutrino and the tau neutrino in the $\nus$ mass range from 10 to 190 $\rm MeV$. Windows between the SN1987a and Big Bang Nucleosynthesis lower limits and our result are still open for future experimental searches. The results obtained are used to constrain an interpretation of the time anomaly observed in the KARMEN1 detector.\

Results from the ντ appearance search in a neutrino beam using the full NOMAD data sample are reported. A new analysis unifies all the hadronic τ decays, significantly improving the overall sensitivity of the experiment to oscillations. The “blind analysis” of all topologies yields no evidence for an oscillation signal. In the two-family oscillation scenario, this sets a 90% CL allowed region in the sin22θμτ–Δm2 plane which includes sin22θμτ<3.3×10−4 at large Δm2 and Δm2< 0.7 eV2/c4 at sin22θμτ=1. The corresponding contour in the νe→ντ oscillation hypothesis results in sin22θeτ<1.5×10−2 at large Δm2 and Δm2<5.9 eV2/c4 at sin22θeτ=1. We also derive limits on effective couplings of the τ lepton to νμ or νe.

Electron recombination in liquid argon (LAr) is studied by means of charged particle tracks collected in various ICARUS liquid argon TPC prototypes. The dependence of the recombination on the particle stopping power has been fitted with a Birks functional dependence. The simulation of the process of electron recombination in Monte Carlo calculations is discussed. A quantitative comparison with previously published data is carried out.

We present a measurement of the muon neutrino–nucleon inclusive charged current cross section, off an isoscalar target, in the neutrino energy range 2.5⩽Eν⩽40GeV. The significance of this measurement is its precision, ±4% in 2.5⩽Eν⩽10GeV, and ±2.6% in 10⩽Eν⩽40GeV regions, where significant uncertainties in previous experiments still exist, and its importance to the current and proposed long baseline neutrino oscillation experiments.

The double-differential production cross-section of positive pions, $d^2\sigma^{\pi^{+}}/dpd\Omega$, measured in the HARP experiment is presented. The incident particles are 8.9 GeV/c protons directed onto a beryllium target with a nominal thickness of 5% of a nuclear interaction length. The measured cross-section has a direct impact on the prediction of neutrino fluxes for the MiniBooNE and SciBooNE experiments at Fermilab. After cuts, 13 million protons on target produced about 96,000 reconstructed secondary tracks which were used in this analysis. Cross-section results are presented in the kinematic range 0.75 GeV/c < $p_{\pi}$ < 6.5 GeV/c and 30 mrad < $\theta_{\pi}$ < 210 mrad in the laboratory frame.

We present our new measurement of the cross-section for charm dimuon production in neutrino–iron interactions based upon the full statistics collected by the NOMAD experiment. After background subtraction we observe 15 344 charm dimuon events, providing the largest sample currently available. The analysis exploits the large inclusive charged current sample – about 9×106 events after all analysis cuts – and the high resolution NOMAD detector to constrain the total systematic uncertainty on the ratio of charm dimuon to inclusive Charged Current (CC) cross-sections to ∼2%. We also perform a fit to the NOMAD data to extract the charm production parameters and the strange quark sea content of the nucleon within the NLO QCD approximation. We obtain a value of mc(mc)=1.159±0.075 GeV/c2 for the running mass of the charm quark in the MS¯ scheme and a strange quark sea suppression factor of κs=0.591±0.019 at Q2=20 GeV2/c2.

The CERN-SPS accelerator has been briefly operated in a new, lower intensity neutrino mode with ~10^12 p.o.t. /pulse and with a beam structure made of four LHC-like extractions, each with a narrow width of 3 ns, separated by 524 ns. This very tightly bunched beam structure represents a substantial progress with respect to the ordinary operation of the CNGS beam, since it allows a very accurate time-of-flight measurement of neutrinos from CERN to LNGS on an event-to-event basis. The ICARUS T600 detector has collected 7 beam-associated events, consistent with the CNGS delivered neutrino flux of 2.2 10^16 p.o.t. and in agreement with the well known characteristics of neutrino events in the LAr-TPC. The time of flight difference between the speed of light and the arriving neutrino LAr-TPC events has been analysed. The result is compatible with the simultaneous arrival of all events with equal speed, the one of light. This is in a striking difference with the reported result of OPERA that claimed that high energy neutrinos from CERN should arrive at LNGS about 60 ns earlier than expected from luminal speed.

The Λ polarization in νμ charged current interactions has been measured in the NOMAD experiment. The event sample (8087 reconstructed Λ 's) is more than an order of magnitude larger than that of previous bubble chamber experiments, while the quality of event reconstruction is comparable. We observe negative polarization along the W -boson direction which is enhanced in the target fragmentation region: Px(xF<0)=−0.21±0.04(stat)±0.02(sys) . In the current fragmentation region we find Px(xF>0)=−0.09±0.06(stat)±0.03(sys) . These results provide a test of different models describing the nucleon spin composition and the spin transfer mechanisms. A significant transverse polarization (in the direction orthogonal to the Λ production plane) has been observed for the first time in a neutrino experiment: Py=−0.22±0.03(stat)±0.01(sys) . The dependence of the absolute value of Py on the Λ transverse momentum with respect to the hadronic jet direction is in qualitative agreement with the results from unpolarized hadron–hadron experiments.

A precision measurement of the double-differential production cross-section, d2σπ+/dpdΩ, for pions of positive charge, performed in the HARP experiment is presented. The incident particles are protons of 12.9 GeV/c momentum impinging on an aluminium target of 5% nuclear interaction length. The measurement of this cross-section has a direct application to the calculation of the neutrino flux of the K2K experiment. After cuts, 210 000 secondary tracks reconstructed in the forward spectrometer were used in this analysis. The results are given for secondaries within a momentum range from 0.75 to 6.5 GeV/c, and within an angular range from 30 mrad to 210 mrad. The absolute normalization was performed using prescaled beam triggers counting protons on target. The overall scale of the cross-section is known to better than 6%, while the average point-to-point error is 8.2%.

HARP is a high-statistics, large solid angle experiment to measure hadron production using proton and pion beams with momenta between 1.5 and 15 GeV/c impinging on many different solid and liquid targets from low to high Z. The experiment, located in the T9 beam of the CERN PS, took data in 2001 and 2002. For the measurement of momenta of produced particles and for the identification of particle types, the experiment includes a large-angle spectrometer, based on a Time Projection Chamber and a system of Resistive Plate Chambers, and a forward spectrometer equipped with a set of large drift chambers, a threshold Cherenkov detector, a time-of-flight wall and an electromagnetic calorimeter. The large angle system uses a solenoidal magnet, while the forward spectrometer is based on a dipole magnet. Redundancy in particle identification has been sought, to enable the cross-calibration of efficiencies and to obtain a few percent overall accuracy in the cross-section measurements. Detector construction, operation and initial physics performances are reported. In addition, the full chain for data recording and analysis, from trigger to the software framework, is described.

The ICARUS T600 detector, the largest liquid Argon Time Projection Chamber (LAr-TPC) realized after many years of RD 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 the ionizing particles with a very small attenuation along the drift path. The solutions adopted for the Argon re-circulation 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 equivalent O2 contamination, a milestone for any future project involving LAr-TPC's and the development of higher detector mass scales.

The ICARUS-T600 liquid argon (LAr) time projection chamber (TPC) detector is currently deployed as a far detector of the Short Baseline Neutrino (SBN) program at Fermilab (USA) to search for a possible LSND-like sterile neutrino signal at Δm2≈1 eV2 with the Booster (BNB) and Main Injector (NuMI) Neutrino Beams [1]. A global physical event rate of ≈0.6Hz, including the genuine neutrino interactions in LAr, beam halos and cosmic interactions inside the proton pulse time windows, is expected, roughly corresponding to ≈4 PB of data for the total 6.6×1020 protons on target exposure if the full ICARUS-T600 detector is read-out (≈200 MB event size). The designed trigger system described here would collect the genuine neutrino interactions with a ≈95% expected efficiency.

The results reported in this paper are based on the analysis of the data recorded with the first half-module of the ICARUS T600 liquid argon Time Projection Chamber (LAr TPC), during a technical run that took place on surface in Pavia (Italy). We include results from the linearity, uniformity and calibration of the electronics, measurements on the electron drift velocity in LAr at different electric fields, as well as the LAr purity achievement of the detector. Two complementary techniques were used to measure the drift electron lifetime inside the active volume: the first, from the data of a purity monitor, gives a measurement localized in space; the second, based on the study of the signals produced by long minimum ionizing tracks crossing the detector, provides a LAr volume averaged value. Both methods yield consistent results over the whole data taking period and are compatible with an uniform LAr purity over the whole volume. The maximal drift electron lifetime value was recorded before the run stop and was about 1.8ms. From an interpretation of the observed drift electron lifetime as a function of time, we conclude that the adopted technology would allow for drift distances exceeding 3m.

Measurements of the double-differential π± production cross section in the momentum range 100⩽p⩽800 MeV/c and angle range 0.35⩽θ⩽2.15 rad in proton-beryllium, proton-carbon, proton-aluminium, proton-copper, proton-tin, proton-tantalum, and proton-lead collisions are presented. The data were taken with the large-acceptance HARP detector in the T9 beam line of the CERN PS. The pions were produced by proton beams in a momentum range from 3 to 12.9 GeV/c hitting a target with a thickness of 5% of a nuclear interaction length. Tracking and identification of the produced particles was performed by using a small-radius cylindrical Time Projection Chamber (TPC) placed inside a solenoidal magnet. Incident particles were identified by an elaborate system of beam detectors. Results are obtained for the double-differential cross sections d2σ/(dpdθ) at six incident proton beam momenta [3, 5, 8, and 8.9 GeV/c (Be only) and 12 and 12.9 GeV/c (Al only)]. They are based on a complete correction of static and dynamic distortions of tracks in the HARP TPC, which allows the complete statistics of the collected data set to be used. The results include and supersede our previously published results and are compatible with these. Results are compared with the GEANT4 and MARS Monte Carlo simulation.26 MoreReceived 27 December 2007DOI:https://doi.org/10.1103/PhysRevC.77.055207©2008 American Physical Society

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.

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.

NOMAD is a neutrino oscillation experiment designed to search for ντ appearance in the CERN-SPS wide band νμ beam. Signal detection relies on the identification of ντ charged current interactions using kinematic criteria. The analysis of the 1995 data sample yields no oscillation signal. Combining all studied τ decay modes, a limit of sin22θμτ<4.2×10−3 is obtained for large Δm2 at the 90% confidence level.

The method developed for the calculation of the flux and composition of the West Area Neutrino Beam used by NOMAD in its search for neutrino oscillations is described. The calculation is based on particle production rates computed using a recent version of FLUKA and modified to take into account the cross-sections measured by the SPY and NA20 experiments. These particles are propagated through the beam line taking into account the material and magnetic fields they traverse. The neutrinos produced through their decays are tracked to the NOMAD detector. The fluxes of the four neutrino flavours at NOMAD are predicted with an uncertainty of about 8% for νμ and νe, 10% for ν̄μ, and 12% for ν̄e. The energy-dependent uncertainty achieved on the νe/νμ prediction needed for a νμ→νe oscillation search ranges from 4% to 7%, whereas the overall normalization uncertainty on this ratio is 4.2%.

We present the results of the first exposure of a Liquid Argon TPC to a multi-GeV neutrino beam.The data have been collected with a 50 liters ICARUS-like chamber located between the CHORUS and NOMAD experiments at the CERN West Area Neutrino Facility (WANF).We discuss both the instrumental performance of the detector and its capability to identify and reconstruct low-multiplicity neutrino interactions.

We carried out a careful evaluation of the performance of the large cathode area ETL 9357FLA photomultiplier tube operating at cryogenic temperature. The measurements were focused on evaluating the parameters which mainly characterize the operating performances of the device down to 77 K and the spread of the distinctive features over 54 samples assembled in the ICARUS apparatus. The results that we obtained demonstrate that the photomultiplier is suited for light detection in such unconventional operating conditions, certifying this device for the direct measurement of scintillation light coming from noble-gas liquids in detectors dedicated to neutrino physics and dark matter research.

The paper is considering an opportunity for the CERN/GranSasso (CNGS) neutrino complex, concurrent time-wise with T2K and NOvA projects, with the aim of improving the sensitivity on νμ ↔ νe θ13 mixing angle by nearly an order of magnitude with respect to T2K expectations. The experiment is based on a ≈20 kt fiducial volume LAr-TPC, following very closely the technology developed for the ICARUS-T600. The present preliminary proposal, called MODULAr, is focused on the following three main activities, for which we seek an extended international collaboration: The neutrino beam from the CERN 400 GeV proton beam and an optimized horn focussing, eventually with an increased intensity in the framework of the LHC accelerator improvement programme. A new experimental area LNGS-B, of at least 50,000 m3 at 10 km off-axis from the main laboratory, eventually upgradable to larger sizes. A location is under consideration at about 1.2 km equivalent water depth. The bubble chamber like imaging and the very fine calorimetry of the LAr-TPC detector will ensure the best background recognition not only from the off-axis neutrinos from the CNGS but also for proton decay and cosmic neutrinos. A new LAr Imaging detector, at least initially with about 20 kt fiducial mass, realised with a modular set of four identical, but independent units, each of about 5 kt, “cloning” the basic technology of the T600. Further phases may foresee extensions of MODULAr to a mass required by the future physics goals. Compared with large water Cherenkov (T2K) and fine grained scintillators (NOvA), the LAr-TPC offers a higher detection efficiency for a given mass and lower backgrounds, since virtually all channels may be unambiguously recognized. In addition to the search for θ13 oscillations and CP violation, it would be possible to collect a large number of accurately identified cosmic ray neutrino events and perform search for proton decay in the exotic channels.

ICARUS T600 is the far detector of the Short Baseline Neutrino program at Fermilab (U.S.A.), which foresees three Liquid Argon Time Projection Chambers along the Booster Neutrino Beam line to search for LSND-like sterile neutrino signal. The T600 detector underwent a significant overhauling process at CERN, introducing new technological developments while maintaining the already achieved performances. The realization of a new liquid argon scintillation light detection system is a primary task of the detector overhaul. As the detector will be subject to a huge flux of cosmic rays, the light detection system should allow the 3D reconstruction of events contributing to the identification of neutrino interactions in the beam spill gate. The design and implementation of the new scintillation light detection system of ICARUS T600 is described.

The NOMAD Collaboration presents a study of opposite sign dimuon events in the framework of Leading Order QCD. A total of 2714 neutrino- and 115 antineutrino-induced opposite sign dimuon events with Eμ1,Eμ2>4.5 GeV, 15<Eν<300 GeV and Q2>1(GeV/c)2 are observed in the Front-Calorimeter of NOMAD during the 1995 and 1996 runs. The analysis yields a value for the charm quark mass of mc=1.3+0.3+0.3−0.3−0.3GeV/c2 and for the average semileptonic branching ratio of Bc=0.095+0.007+0.014−0.007−0.013. The ratio of the strange to non-strange sea in the nucleon is measured to be κ=0.48+0.09+0.17−0.07−0.12. The measured rate of charm-induced dimuon relative to single muon, as a function of neutrino energy, is consistent with the slow rescaling hypothesis of heavy quark production.

An experiment has been set up at the Institut Laue-Langevin in Grenoble to search for free neutron-antineutron oscillations. No candidate events were observed in the first run of the experiment, providing a lower limit in the oscillation time τnn>107s at 90% CL, which improves the previous experimental limit by an order of magnitude.

We present a study of exclusive neutral pion production in neutrino-nucleus Neutral Current interactions using data from the NOMAD experiment at the CERN SPS. The data correspond to $1.44 \times 10^6$ muon-neutrino Charged Current interactions in the energy range $2.5 \leq E_{\nu} \leq 300$ GeV. Neutrino events with only one visible $\pi^0$ in the final state are expected to result from two Neutral Current processes: coherent $\pi^0$ production, {\boldmath $\nu + {\cal A} \to \nu + {\cal A} + \pi^0$} and single $\pi^0$ production in neutrino-nucleon scattering. The signature of coherent $\pi^0$ production is an emergent $\pi^0$ almost collinear with the incident neutrino while $\pi^0$'s produced in neutrino-nucleon deep inelastic scattering have larger transverse momenta. In this analysis all relevant backgrounds to the coherent $\pi^0$ production signal are measured using data themselves. Having determined the backgrounds, and using the Rein-Sehgal model for the coherent $\pi^0$ production to compute the detection efficiency, we obtain {\boldmath $4630 \pm 522 (stat) \pm 426 (syst)$} corrected coherent-$\pi^0$ events with $E_{\pi^0} \geq 0.5$ GeV. We measure {\boldmath $\sigma (\nu {\cal A} \to \nu {\cal A} \pi^0) = [ 72.6 \pm 8.1(stat) \pm 6.9(syst) ] \times 10^{-40} cm^2/nucleus$}. This is the most precise measurement of the coherent $\pi^0$ production to date.

We present a search for neutrino induced events containing a single, exclusive photon using data from the NOMAD experiment at the CERN SPS where the average energy of the neutrino flux is ≃25GeV. The search is motivated by an excess of electron-like events in the 200–475 MeV energy region as reported by the MiniBooNE experiment. In NOMAD, photons are identified via their conversion to e+e− in an active target embedded in a magnetic field. The background to the single photon signal is dominated by the asymmetric decay of neutral pions produced either in a coherent neutrino–nucleus interaction, or in a neutrino–nucleon neutral current deep inelastic scattering, or in an interaction occurring outside the fiducial volume. All three backgrounds are determined in situ using control data samples prior to opening the 'signal-box'. In the signal region, we observe 155 events with a predicted background of 129.2±8.5±3.3. We interpret this as null evidence for excess of single photon events, and set a limit. Assuming that the hypothetical single photon has a momentum distribution similar to that of a photon from the coherent π0 decay, the measurement yields an upper limit on single photon events, <4.0×10−4 per νμ charged current event. Narrowing the search to events where the photon is approximately collinear with the incident neutrino, we observe 78 events with a predicted background of 76.6±4.9±1.9 yielding a more stringent upper limit, <1.6×10−4 per νμ charged current event.

ICARUS T600 will be operated as far detector of the Short Baseline Neutrino program at Fermilab (USA), which foresees three liquid argon time projection chambers along the Booster Neutrino Beam line to search for a LSND-like sterile neutrino signal. The detector employs 360 photomultiplier tubes, Hamamatsu model R5912-MOD, suitable for cryogenic applications. A total of 400 PMTs were procured from Hamamatsu and tested at room temperature to evaluate the performance of the devices and their compliance to detect the liquid argon scintillation light in the T600 detector. Furthermore 60 units were also characterized at cryogenic temperature, in liquid argon bath, to evaluate any parameter variation which could affect the scintillation light detection. All the tested PMTs were found to comply with the requirements of ICARUS T600 and a subset of 360 specimens was selected for the final installation in the detector.

The measurement of muon momentum by Multiple Coulomb Scattering is a crucial ingredient to the reconstruction of νμ CC events in the ICARUS-T600 liquid argon TPC in absence of magnetic field, as in the search for sterile neutrinos at Fermilab where ICARUS will be exposed to ∼ 1 GeV Booster neutrino beam. A sample of ∼ 1000 stopping muons produced by charged current interactions of CNGS νμ in the surrounding rock at the INFN Gran Sasso underground Laboratory provides an ideal benchmark in the few-GeV range since their momentum can be directly and independently obtained by the calorimetric measurement. Stopping muon momentum in the 0.5–4.5 GeV/c range has been reconstructed via Multiple Coulomb Scattering with resolution ranging from 10 to 25% depending on muon energy, track length and uniformity of the electric field in the drift volume.

The construction and performance of a large area scintillator-based time-of-flight detector for the HARP experiment at CERN are reported. An intrinsic counter time resolution of ∼160 ps was achieved. The precision on the time calibration and monitoring of the detector was maintained at better than 100 ps by using dedicated cosmic rays runs, a fast laser-based system and calibrations with beam particles. The detector was operated on the T9 PS beamline during 2001 and 2002. A time-of-flight resolution of ∼200 ps was obtained, providing π/p discrimination at more than 3σ up to 4.0 GeV/c momentum.

A measurement of the double-differential cross-section for the production of charged pions in proton--tantalum collisions emitted at large angles from the incoming beam direction is presented. The data were taken in 2002 with the HARP detector in the T9 beam line of the CERN PS. The pions were produced by proton beams in a momentum range from 3 \GeVc to 12 \GeVc hitting a tantalum target with a thickness of 5% of a nuclear interaction length. The angular and momentum range covered by the experiment ($100 \MeVc \le p < 800 \MeVc$ and $0.35 \rad \le \theta <2.15 \rad$) is of particular importance for the design of a neutrino factory. The produced particles were detected using a small-radius cylindrical time projection chamber (TPC) placed in a solenoidal magnet. Track recognition, momentum determination and particle identification were all performed based on the measurements made with the TPC. An elaborate system of detectors in the beam line ensured the identification of the incident particles. Results are shown for the double-differential cross-sections ${{\mathrm{d}^2 \sigma}} / {{\mathrm{d}p\mathrm{d}\theta}}$ at four incident proton beam momenta (3 \GeVc, 5 \GeVc, 8 \GeVc and 12 \GeVc). In addition, the pion yields within the acceptance of typical neutrino factory designs are shown as a function of beam momentum. The measurement of these yields within a single experiment eliminates most systematic errors in the comparison between rates at different beam momenta and between positive and negative pion production.

ICARUS T600 liquid argon time projection chamber is the first large mass electronic detector of a new generation able to combine the imaging capabilities of the old bubble chambers with the excellent calorimetric energy measurement. After the three months demonstration run on surface in Pavia during 2001, the T600 cryogenic plant was significantly revised, in terms of reliability and safety, in view of its long-term operation in an underground environment. The T600 detector was activated in Hall B of the INFN Gran Sasso Laboratory during Spring 2010, where it was operated without interruption for about three years, taking data exposed to the CERN to Gran Sasso long baseline neutrino beam and cosmic rays. In this paper the T600 cryogenic plant is described in detail together with the commissioning procedures that lead to the successful operation of the detector shortly after the end of the filling with liquid Argon. Overall plant performance and stability during the long-term underground operation are discussed. Finally, the decommissioning procedures, carried out about six months after the end of the CNGS neutrino beam operation, are reported.

A search was made for a new light gauge boson X which might be produced in π0→γ+X decay from neutral pions generated by 450 GeV protons in the CERN SPS neutrino target. The X's would penetrate the downstream shielding and be observed in the NOMAD detector via the Primakoff effect, in the process of X→π0 conversion in the external Coulomb field of a nucleus. With 1.45×1018 protons on target, 20 candidate events with energy between 8 and 140 GeV were found from the analysis of neutrino data. This number is in agreement with the expectation of 18.1±2.8 background events from standard neutrino processes. A new 90 %C.L. upper limit on the branching ratio Br(π0→γ+X)< (3.3 to 1.9)×10−5 for X masses ranging from 0 to 120 MeV/c2 is obtained.

With additional data and improved algorithms, we have enhanced the sensitivity of our appearance search for νμ→ντ oscillations in the NOMAD detector in the CERN-SPS wide-band neutrino beam. The search uses kinematic criteria to identify ντ charged current interactions followed by decay of the τ− to one of several decay modes. Our “blind” analyses of deep-inelastic scattering data taken in 1996 and 1997, combined with consistent reanalyses of previously reported 1995 data, yield no oscillation signal. For the two-family oscillation scenario, we present the contour outlining a 90% C.L. confidence region in the sin22θμτ–Δm2 plane. At large Δm2, the confidence region includes sin22θμτ<1.2×10−3 (a limit 3.5 times more stringent than in our previous publication), while at sin22θμτ=1, the confidence region includes Δm2<1.2 eV2/c4.

We present a measurement of the polarization of Λ̄ hyperons produced in νμ charged current interactions. The full data sample from the NOMAD experiment has been analyzed using the same V0 identification procedure and analysis method reported in a previous paper [NOMAD Collaboration, Nucl. Phys. B 588 (2000) 3] for the case of Λ hyperons. The Λ̄ polarization has been measured for the first time in a neutrino experiment. The polarization vector is found to be compatible with zero.

The predictions of meson production by 450GeV/c protons on Be using the Monte Carlo FLUKA standalone and GEANT-FLUKA and GEANT-GHEISHA in GEANT are compared with available experimental measurements. The comparison enlightens the improvements of the hadronic generator models of the present standalone code FLUKA with respect to the 1992 version which is embedded into GEANT-FLUKA. Worse results were obtained with the GHEISHA package. A complete simulation of the SPS neutrino beam line at CERN showed significant variations in the intensity and composition of the neutrino beam when FLUKA standalone instead of the GEANT-FLUKA package is used to simulate particle production in the Be target.

A study of strange particle production in νμ charged current interactions has been performed using the data from the NOMAD experiment. Yields of neutral strange particles (K0s,Λ,Λ̄) have been measured. Mean multiplicities are reported as a function of the event kinematic variables Eν, W2 and Q2 as well as of the variables describing particle behaviour within a hadronic jet: xF, z and pT2. Decays of resonances and heavy hyperons with identified K0s and Λ in the final state have been analyzed. Clear signals corresponding to K★±, Σ★±, Ξ− and Σ0 have been observed.

The results of the measurements of the double-differential production cross-sections of pions in p-C and $\pi^\pm$-C interactions using the forward spectrometer of the HARP experiment are presented. The incident particles are 12 GeV/c protons and charged pions directed onto a carbon target with a thickness of 5% of a nuclear interaction length. For p-C interactions the analysis is performed using 100035 reconstructed secondary tracks, while the corresponding numbers of tracks for $\pi^-$-C and $\pi^+$-C analyses are 106534 and 10122 respectively. Cross-section results are presented in the kinematic range 0.5 GeV/c $\leq p_{\pi} <$ 8 GeV/c and 30 mrad $\leq \theta_{\pi} <$ 240 mrad in the laboratory frame. The measured cross-sections have a direct impact on the precise calculation of atmospheric neutrino fluxes and on the improved reliability of extensive air shower simulations by reducing the uncertainties of hadronic interaction models in the low energy range.

A measurement of the double-differential π± production cross-section in proton–carbon, proton–copper and proton–tin collisions in the range of pion momentum 100 MeV/c≤p<800 MeV/c and angle 0.35 rad≤θ<2.15 rad is presented. The data were taken with the HARP detector in the T9 beam line of the CERN PS. The pions were produced by proton beams in a momentum range from 3 GeV/c to 12 GeV/c hitting a target with a thickness of 5% of a nuclear interaction length. The tracking and identification of the produced particles was done using a small-radius cylindrical time projection chamber (TPC) placed in a solenoidal magnet. An elaborate system of detectors in the beam line ensured the identification of the incident particles. Results are shown for the double-differential cross-sections d2σ/dpdθ at four incident proton beam momenta (3 GeV/c, 5 GeV/c, 8 GeV/c and 12 GeV/c).

Measurements of the double-differential charged pion production cross-section in the range of momentum 0.5 GeV/c < p < 8.0 GeV/c and angle 0.025 rad < theta <0.25 rad in collisions of protons on beryllium, carbon, nitrogen, oxygen, aluminium, copper, tin, tantalum and lead are presented. The data were taken with the large acceptance HARP detector in the T9 beam line of the CERN PS. Incident particles were identified by an elaborate system of beam detectors. The data were taken with thin targets of 5% of a nuclear interaction length. The tracking and identification of the produced particles was performed using the forward system of the HARP experiment. Results are obtained for the double-differential cross section mainly at four incident proton beam momenta (3 GeV/c, 5 GeV/c, 8 GeV/c and 12 GeV/c). Measurements are compared with the GEANT4 and MARS Monte Carlo generators. A global parametrization is provided as an approximation of all the collected datasets which can serve as a tool for quick yields estimates.

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.

A description is given of the NOMAD electromagnetic calorimeter, consisting of 875 lead-glass counters read out by two-stage photomultipliers and a low noise electronic chain. The detector operates in a 0.4 T magnetic field transverse to the counter axis. The paper discusses the design criteria, the lead-glass characteristics, the properties of the read out chain and provides a summary of the calorimeter performance.

A generation of neutrino experiments have established that neutrinos mix and probably have mass. The mixing phenomenon points to processes beyond those of the Standard Model, possibly at the Grand Unification energy scale. A extensive sequence of of experiments will be required to measure precisely all the parameters of the neutrino mixing matrix, culminating with the discovery and study of leptonic CP violation. As a first step, extensions of conventional pion/kaon decay beams, such as off-axis beams or low-energy super-beams, have been considered. These could yield first observations of $ν_μ\to ν_e$ transitions at the atmospheric frequency, which have not yet been observed, and a first measurement of $θ_{13}$. Experiments with much better flux control can be envisaged if the neutrinos are obtained from the decays of stored particles. One such possibility is the concept of beta beams provided by the decays of radioactive nuclei, that has been developed within the context of these studies. These would provide a pure (anti-)electron-neutrino beam of a few hundred MeV, and beautiful complementarity with a high-intensity, low-energy conventional beam, enabling experimental probes of T violation as well as CP violation. Ultimately, a definitive and complete set of measurements would offered by a Neutrino Factory based on a muon storage ring. This powerful machine offers the largest reach for CP violation, even for very small values of $θ_{13}$.

Detection of Cherenkov light emission in liquid argon has been obtained with an ICARUS prototype, during a dedicated test run at the Gran Sasso Laboratory external facility. Ionizing tracks from cosmic ray muons crossing the detector active volume have been collected in coincidence with visible light signals from a photo-multiplier (PMT) immersed in liquid argon. A 3D reconstruction of the tracks has been performed exploiting the ICARUS imaging capability. The angular distributions of the tracks triggered by the PMT signals show an evident directionality. By means of a detailed Monte Carlo simulation we show that the geometrical characteristics of the events are compatible with the hypothesis of Cherenkov light emission as the main source of the PMT signals.

The discovery of the neutrino oscillation pattern with solar and atmospheric neutrinos has stimulated systematic studies with long-baseline accelerator experiments. Precise neutrino beamline calculations have demonstrated the importance and paucity of existing hadroproduction data needed to shape the primary meson production in targets and tune available Monte Carlo codes for hadronic shower simulation. After a brief introduction to the physics of neutrino beams, available hadron production data will be reviewed with regards to their parametrization. Fast simulations based on such parameterizations and full Monte Carlo simulations of neutrino beamlines will then be illustrated. The prospective impact of new hadroproduction experiments, such as HARP at CERN and MIPP at Fermilab, will be shown together with some neutrino beamline simulations.

Measurements of the double-differential π± production cross-section in the range of momentum 100 MeV/c≤p< 800 MeV/c and angle 0.35 rad ≤θ< 2.15 rad in proton–beryllium, proton–aluminium and proton–lead collisions are presented. The data were taken with the HARP detector in the T9 beam line of the CERN PS. The pions were produced by proton beams in a momentum range from 3 GeV/c to 12.9 GeV/c hitting a target with a thickness of 5% of a nuclear interaction length. The tracking and identification of the produced particles was performed using a small-radius cylindrical time projection chamber (TPC) placed inside a solenoidal magnet. Incident particles were identified by an elaborate system of beam detectors. Results are obtained for the double-differential cross-sections d2σ/dpdθ at six incident proton beam momenta (3 GeV/c, 5 GeV/c, 8 GeV/c, 8.9 GeV/c (Be only), 12 GeV/c and 12.9 GeV/c (Al only)) and compared to previously available data.

This proposal describes an experimental search for sterile neutrinos beyond the Standard Model with a new CERN-SPS neutrino beam. The experiment is based on two identical LAr-TPC's followed by magnetized spectrometers, observing the electron and muon neutrino events at 1600 and 300 m from the proton target. This project will exploit the ICARUS T600, moved from LNGS to the CERN "Far" position. An additional 1/4 of the T600 detector will be constructed and located in the "Near" position. Two spectrometers will be placed downstream of the two LAr-TPC detectors to greatly complement the physics capabilities. Spectrometers will exploit a classical dipole magnetic field with iron slabs, and a new concept air-magnet, to perform charge identification and muon momentum measurements in a wide energy range over a large transverse area. In the two positions, the radial and energy spectra of the nu_e beam are practically identical. Comparing the two detectors, in absence of oscillations, all cross sections and experimental biases cancel out, and the two experimentally observed event distributions must be identical. Any difference of the event distributions at the locations of the two detectors might be attributed to the possible existence of {\nu}-oscillations, presumably due to additional neutrinos with a mixing angle sin^2(2theta_new) and a larger mass difference Delta_m^2_new. The superior quality of the LAr imaging TPC, in particular its unique electron-pi_zero discrimination allows full rejection of backgrounds and offers a lossless nu_e detection capability. The determination of the muon charge with the spectrometers allows the full separation of nu_mu from anti-nu_mu and therefore controlling systematics from muon mis-identification largely at high momenta.

The ICARUS T600 liquid argon (LAr) time projection chamber (TPC) underwent a major overhaul at CERN in 2016-2017 to prepare for the operation at FNAL in the Short Baseline Neutrino (SBN) program. This included a major upgrade of the photo-multiplier system and of the TPC wire read-out electronics. The full TPC wire read-out electronics together with the new wire biasing and interconnection scheme are described. The design of a new signal feed-through flange is also a fundamental piece of this overhaul whose major feature is the integration of all electronics components onto the signal flange. Initial functionality tests of the full TPC electronics chain installed in the T600 detector at FNAL are also described.

The transverse shower shape of the energy deposition of hadrons in the NOMAD lead glass calorimeter has been studied by exposing a prototype of this calorimeter to pion test beams of various momenta and incident angles. Large event-to-event fluctuations in the shower shape and significant energy depositions far from the incident hadron were observed making it difficult to associate all the deposited energy to the incident hadron that caused it. Since in the NOMAD detector the momenta of charged hadrons are measured by a magnetic spectrometer, such an association is necessary to be able to subtract from the calorimeter all the energy caused by the observed charged hadrons in order to avoid double counting. Probability functions based on the measurements have been developed to describe fluctuations of the lateral shower shape. Starting from these functions, an algorithm is developed for identifying the energy deposition associated to a charged hadron. The identification and separation of overlapping showers based on these functions is also discussed. The Monte Carlo simulation of the calorimeter reproduces the test beam data well therefore allowing the application of the algorithm at angles and momenta not studied in the test beam.

A precise calibration and monitoring system has been developed for the HARP experiment scintillator-based time of flight system. An Nd-YAG laser with passive Q-switch and active/passive mode-locking and a custom-made laser light injection system based on a bundle of IR monomode optical fibers were used. The laser pulse timing was provided by a novel ultrafast InGaAs MSM photodiode, with 30 ps risetime. Experience over a several month data taking period in 2001 and 2002 shows that drifts in timing down to about 70 ps can be traced.

The MODULAr project foresees the exploitation of a new liquid Argon imaging detector, of at least 20 kt fiducial mass, to be operated in a shallow depth location under the Gran Sasso Mountain. It will be devoted to study neutrino oscillations with an optimized off-axis CNGS neutrino beam. Cosmic neutrinos as well as proton decay will also be addressed. The MODULAr detector will vastly inherit from the technology developed for ICARUS-T600. However, such an increase in the volume over the current ICARUS-T600 needs to be carefully considered. It is concluded that a single, huge volume is an inoperable and uneconomical solution for many reasons. A very large mass is best realized with a modular set of many identical, independent units, each of about 5 kt, ``cloning'' the basic technology of the ICARUS-T600. Several of such modular units will be assembled to reach at least 20 kt as initial sensitive volume. The increase of the active volume of about one order of magnitude with respect to the ICARUS-T600 detector requires some specific R&D activity, which will be implemented in a ∼ 360 ton prototype unit (SLICE) of reduced length.

Measurements of the double-differential π± production cross-section in the range of momentum 0.5 GeV/c⩽p⩽8.0 GeV/c and angle 0.025rad⩽θ⩽0.25rad in interactions of charged pions on beryllium, carbon, aluminium, copper, tin, tantalum and lead are presented. These data represent the first experimental campaign to systematically measure forward pion hadroproduction. The data were taken with the large acceptance HARP detector in the T9 beam line of the CERN PS. Incident particles, impinging on a 5% nuclear interaction length target, were identified by an elaborate system of beam detectors. The tracking and identification of the produced particles was performed using the forward spectrometer of the HARP detector. Results are obtained for the double-differential cross-sections d2σ/dpdΩ mainly at four incident pion beam momenta (3 GeV/c, 5 GeV/c, 8 GeV/c and 12 GeV/c). The measurements are compared with the GEANT4 and MARS Monte Carlo simulation.

Measurements of the double-differential pi+/- production cross-section in the range of momentum 100 MeV/c <= p <= 800 MeV/c and angle 0.35 rad <= theta <= 2.15 rad using pi+/- beams incident on beryllium, aluminium, carbon, copper, tin, tantalum and lead targets are presented. The data were taken with the large acceptance HARP detector in the T9 beam line of the CERN Proton Synchrotron. The secondary pions were produced by beams in a momentum range from 3 GeV/c to 12.9 GeV/c hitting a solid target with a thickness of 5% of a nuclear interaction length. The tracking and identification of the produced particles was performed using a small-radius cylindrical time projection chamber (TPC) placed inside a solenoidal magnet. Incident particles were identified by an elaborate system of beam detectors. Results are obtained for the double-differential cross-sections d2sigma/dpdtheta at six incident beam momenta. Data at 3 GeV/c, 5 GeV/c, 8 GeV/c, and 12 GeV/c are available for all targets while additional data at 8.9 GeV/c and 12.9 GeV/c were taken in positive particle beams on Be and Al targets, respectively. The measurements are compared with several generators of GEANT4 and the MARS Monte Carlo simulation.

The ICARUS T600, a liquid argon time projection chamber (LAr-TPC) detector mainly devoted to neutrino physics, underwent a major overhauling at CERN in 2016-2017, which included also a new design of the read-out electronics, in view of its operation in Fermilab on the Short Baseline Neutrino (SBN) beam from 2019. The new more compact electronics showed capability of handling more efficiently the signals also in the intermediate Induction 2 wire plane with a significant increase of signal to noise (S/N), allowing for charge measurement also in this view. The new front-end and the analog to digital conversion (ADC) system are presented together with the results of the tests on 50 liters liquid argon TPC performed at CERN with cosmic rays.

This paper reports on the charged pion production yields measured by the SPY/NA56 experiment for 450 GeV/c proton interactions on beryllium targets. The present data cover a secondary momentum range from 7 GeV/c to 135 GeV/c in the forward direction. An experimental accuracy ranging from 5 to 10%, depending on the beam momentum, has been achieved, limited mainly by the knowledge of the beam acceptance. These results will be relevant in the calculation of neutrino fluxes in present and future neutrino beams.

Test beam results of the NOMAD electromagnetic calorimeter are presented showing linearity, signal uniformity, energy and position resolution measured in an electron beam. Tests were also performed placing the calorimeter in a magnetic field of 0.4 T. Results on the π rejection obtained using a combined measurement of preshower/electromagnetic calorimeter are found to be in good agreement with the project expectations. Finally the calorimeter response to the muons is discussed.

ŽWe carried out a model-independent search for light scalar or pseudoscalar particles a's an example of which is the .axion that couple to two photons by using a photon-regeneration method at high energies allowing a substantial increase in the sensitivity to eV masses.The experimental set-up is based on elements of the CERN West Area Neutrino Facility Ž .WANF beam line and the NOMAD neutrino detector.The new particles, if they exist, could be produced through the Primakoff effect in interactions of high energy photons, generated by the 450 GeV protons in the CERN SPS neutrino target, with virtual photons from the WANF horn magnetic field.The particles would penetrate the downstream shielding and would be observed in the NOMAD neutrino detector through their re-conversion into real high energy photons by interacting with the virtual photons from the magnetic field of the NOMAD dipole magnet.From the analysis of the data collected during the 1996 run with 1.08 = 10 19 protons on target, 312 candidate events with energy between 5 and 140 GeV were found.This number is in general agreement with the expectation of 272 " 18 background events from standard neutrino processes.A 90 % CL upper limit on the agg-coupling g -1.5 = 10 y4 GeV y1 agg for a masses up to 40 eV is obtained.

The particle identification (PID) methods used for the calculation of secondary pion yields with the HARP forward spectrometer are presented. Information from time of flight and Cherenkov detectors is combined using likelihood techniques. The efficiencies and purities associated with the different PID selection criteria are obtained from the data. For the proton–aluminium interactions at 12.9 GeV/c incident momentum, the PID efficiencies for positive pions are 86% in the momentum range below 2 GeV/c, 92% between 2 and 3 GeV/c and 98% in the momentum range above 3 GeV/c. The purity of the selection is better than 92% for all momenta. Special emphasis has been put on understanding the main error sources. The final PID uncertainty on the pion yield is 3.3%.

Measurements of double-differential charged pion production cross-sections in interactions of 12 GeV/c protons on O_2 and N_2 thin targets are presented in the kinematic range 0.5 GeV/c < p_{\pi} < 8 GeV/c and 50 mrad < \theta_{\pi} < 250 mrad (in the laboratory frame) and are compared with p--C results. For p--N_2 (p--O_2) interactions the analysis is performed using 38576 (7522) reconstructed secondary pions. The analysis uses the beam instrumentation and the forward spectrometer of the HARP experiment at CERN PS. The measured cross-sections have a direct impact on the precise calculation of atmospheric neutrino fluxes and on the improved reliability of extensive air shower simulations by reducing the uncertainties of hadronic interaction models in the low energy range. In particular, the present results allow the common hypothesis that p--C data can be used to predict the p--N_2 and p--O_2 pion production cross-sections to be tested.

This paper reports on the charged K/π production ratios and on the shape of the pT distributions of π fluxes measured by the SPY/NA56 experiment for 450 GeV/c proton interactions on beryllium targets. The present data cover a secondary momentum range from 7 GeV/c to 135 GeV/c in the forward direction and with pT values up to 600 MeV/c. An experimental accuracy of about 3% has been achieved. These results will reduce the uncertainty on the estimation of the νe component of neutrino beams.

Backward proton and π− production has been studied in νμCC interactions with carbon nuclei. Detailed analyses of the momentum distributions, of the production rates, and of the general features of events with a backward going particle, have been carried out in order to understand the mechanism producing these particles. The backward proton data have been compared with the predictions of the reinteraction and the short range correlation models.

Updated results from the appearance searches for νμ→ντ and νe→ντ oscillations in the full NOMAD data sample are reported. The increased data and the use of more refined kinematic schemes for the ντ CC selection allow a significant improvement of the overall sensitivity. The “blind analysis” of both the deep-inelastic and the low multiplicity samples yields no evidence for an oscillation signal. In the two-family oscillation scenario, this sets a 90% C.L. region in the sin22θμτ−Δm2 plane which includes sin22θμτ<4.4×10−4 at large Δm2 and Δm2<0.8 eV2/c4 at sin22θμτ=1. The corresponding contour in the νe→ντ oscillation hypothesis results in sin22θeτ<2.2×10−2 at large Δm2 and Δm2<6.5 eV2/c4 at sin22θeτ=1.

The inclusive production of the meson resonances ρ0(770), f0(980) and f2(1270) in neutrino–nucleus charged current interactions has been studied with the NOMAD detector exposed to the wide band neutrino beam generated by 450 GeV protons at the CERN SPS. For the first time the f0(980) meson is observed in neutrino interactions. The statistical significance of its observation is 6 standard deviations. The presence of f2(1270) in neutrino interactions is reliably established. The average multiplicity of these three resonances is measured as a function of several kinematic variables. The experimental results are compared to the multiplicities obtained from a simulation based on the Lund model. In addition, the average multiplicity of ρ0(770) in antineutrino–nucleus interactions is measured.

A search was made among νμ charged current events collected in the NOMAD experiment for the reaction: νμ+N→μ−+D★++hadrons↪D0+π+↪K−+π+. A high purity D★+ sample composed of 35 events was extracted. The D★+ yield in νμ charged current interactions was measured to be T=(0.79±0.17(stat.)±0.10(syst.))%. The mean fraction of the hadronic jet energy taken by the D★+ is 0.67±0.02(stat.)±0.02(syst.). The distributions of the fragmentation variables z, PT2 and xF for D★+ are also presented.

The LSND experiment has observed a 3.8 sigma excess of anti-nu_e events from an anti-nu_mu beam coming from pions at rest. If confirmed, the LSND anomaly would imply new physics beyond the standard model, presumably in the form of some additional sterile neutrinos. The MiniBooNE experiment at FNAL-Booster has further searched for the LSND anomaly. Above 475 MeV, the nu_e result is excluding the LSND anomaly to about 1.6 sigma but it introduces an unexplained, new 3.0 sigma anomaly at lower energies, down to 200 MeV. The nu_e data have so far an insufficient statistics to be conclusive with LSND's anti-nu_e. The present proposal at the CERN-PS is based on two strictly identical LAr-TPC detectors in the near and far positions, respectively at 127 and 850 m from the neutrino (or antineutrino) target and focussing horn, observing the electron-neutrino signal. This project will benefit from the already developed technology of ICARUS T600, well tested on surface in Pavia, without the need of any major R&amp;D activity and without the added problems of an underground experiment (CNGS-2). The superior quality of the Liquid Argon imaging TPC and its unique electron - pi-zero discrimination allow full rejection of the NC background, without efficiency loss for electron neutrino detection. In two years of exposure, the far detector mass of 600 tons and a reasonable utilization of the CERN-PS with the refurbished previous TT7 beam line will allow to collect about 10^6 charged current events, largely adequate to settle definitely the LSND anomaly.

Several different experiments have hinted to the existence of in the neutrino sector, implying the possible presence of additional sterile neutrinos or of other options. A definitive experimental search, capable to clarify either in favour or against all these anomalies at the appropriate > 5 sigma level has been proposed by the ICARUS-NESSIE Collaboration. The technique is based on two innovative concepts, namely (1) a large mass Liquid Argon Time Projection Chamber (LAr-TPC) now in full operation at LNGS and (2) the search for spectral differences in two identical detectors at different distances along the (anti-)neutrino line(s).

The CNGS facility (CERN Neutrinos to Gran Sasso) aims at directly detecting muon to tau neutrino oscillations. An intense muon-neutrino beam (1.0·1017 muon neutrinos/day) is generated at CERN and directed over 732km towards the Gran Sasso National Laboratory, LNGS, in Italy, where two large and complex detectors, OPERA and ICARUS, are located. CNGS is the first long-baseline neutrino facility in which the measurement of the oscillation parameters is performed by observation of the tau-neutrino appearance. The facility is approved for a physics program of five years with a total of 22.5·1019 protons on target. Having resolved successfully some initial issues that occurred since its commissioning in 2006, the facility had its first complete year of physics in 2008. By the end of 2009 the facility delivered in total 5.4·1019 protons on target corresponding to an expected ~2-3 tau neutrino events in the OPERA detector, according to the most probable physics parameter oscillation model of today. The experiences gained in operating this 500 kW neutrino beam facility along with highlights of the beam performance in 2009 are discussed.

An analog mean-timer has been designed and tested with 3 m long scintillation counters. It provides the mean time of two ECL signals with better than 100 ps precision and can operate at up to 16 MHz.

Abstract We have designed, built and tested a high stability system based on blue light emitting diodes (LED) and current pulse generators for calibration and monitoring of lead-glass calorimeters. This apparatus is presently being used for the electromagnetic calorimeter of the WA96 (NOMAD) experiment at CERN. The system was developed to minimize the sensitivity to temperature variations, different loadings, and ageing effects. Tests performed both in the laboratory and in the experiment showed that the response of the lead-glass calorimeter modules to LED light pulses could be kept within the precision of ±1% for periods of several months.

The HARP system of resistive plate chambers (RPCs) was designed to perform particle identification by the measurement of the difference in the time-of-flight of different particles. In previous papers an apparent discrepancy was shown between the response of the RPCs to minimum ionizing pions and heavily ionizing protons. Using the kinematics of elastic scattering off a hydrogen target a controlled beam of low momentum recoil protons was directed onto the RPC chambers. With this method the trajectory and momentum, and hence the time-of-flight of the protons can be precisely predicted without need for a measurement of momentum of the protons. It is demonstrated that the measurement of the time-of-arrival of particles by the thin gas-gap glass RPC system of the HARP experiment depends on the primary ionization deposited by the particle in the detector.

In the HARP experiment the large-angle spectrometer is using a cylindrical TPC as main tracking and particle identification detector. The momentum scale of reconstructed tracks in the TPC is the most important systematic error for the majority of kinematic bins used for the HARP measurements of the double-differential production cross-section of charged pions in proton interactions on nuclear targets at large angle. The HARP TPC operated with a number of hardware shortfalls and operational mistakes. Thus it was important to control and characterize its momentum calibration. While it was not possible to enter a direct particle beam into the sensitive volume of the TPC to calibrate the detector, a set of physical processes and detector properties were exploited to achieve a precise calibration of the apparatus. In the following we recall the main issues concerning the momentum measurement in the HARP TPC, and describe the cross-checks made to validate the momentum scale. As a conclusion, this analysis demonstrates that the measurement of momentum is correct within the published precision of 3%.

Measurements of the double-differential proton production cross-section ${d}^{2}\ensuremath{\sigma}/dpd\ensuremath{\Omega}$ in the range of momentum $0.5 \mathrm{GeV}/c\ensuremath{\leqslant}p&lt;8.0 \mathrm{GeV}/c$ and angle $0.05 \text{rad}\ensuremath{\leqslant}\ensuremath{\theta}&lt;0.25 \text{rad}$ in collisions of charged pions and protons on beryllium, carbon, aluminium, copper, tin, tantalum, and lead are presented. The data were taken with the large acceptance HARP detector in the T9 beam line of the CERN Proton Synchrotron. Incident particles were identified by an elaborate system of beam detectors and impinged on a target of $5%$ of a nuclear interaction length. The tracking and identification of the produced particles was performed using the forward spectrometer of the HARP experiment. Results are obtained for the double-differential cross-sections mainly at four incident beam momenta ($3,5,8$, and $12$ $\text{GeV}/c$). Measurements are compared with predictions of the geant4 and mars Monte Carlo generators.

A key feature for the success of the liquid Argon imaging TPC (LAr-TPC) technology is the industrial purification against electro-negative impurities, especially Oxygen and Nitrogen remnants, which have to be continuously kept at an exceptionally low level by filtering and recirculating liquid Argon. Improved purification techniques have been applied to a 120 liters LAr-TPC test facility in the INFN-LNL laboratory. Through-going muon tracks have been used to determine the free electron lifetime in liquid Argon against electro-negative impurities. The short path length here observed (30 cm) is compensated by the high accuracy in the observation of the specific ionization of cosmic ray muons at sea level as a function of the drift distance. A free electron lifetime of (21.4+7.3-4.3) ms, namely > 15.8 ms at 90 % C.L. has been observed over several weeks under stable conditions, corresponding to a residual Oxygen equivalent of about 15 ppt (part per trillion). At 500 V/cm, the free electron speed is 1.5 m/ms. In a LAr-TPC a free electron lifetime in excess of 15 ms corresponds for instance to an attenuation of less than 15 % after a drift path of 5 m, opening the way to the operation of the LAr-TPC with exceptionally long drift distances.

Marx-topology modulator, capable of providing the required waveform shaping to stabilize the accelerating gradient and compensate for beam loading, will be presented, along with development data from the prototype unit.

The accumulation of positive ions, produced by ionizing particles crossing Liquid Argon Time Projection Chambers (LAr-TPCs), may generate distortions of the electric drift field affecting the track reconstruction of the ionizing events. These effects could become relevant for large LAr-TPCs operating at surface or at shallow depth, where the detectors are exposed to a copious flux of cosmic rays. A detailed study of such possible field distortions in the ICARUS T600 LAr-TPC has been performed analyzing a sample of cosmic muon tracks recorded with one T600 module operated at surface in 2001. The maximum track distortion turns out to be of few mm in good agreement with the prediction by a numerical calculation. As a cross-check, the same analysis has been performed on a cosmic muon sample recorded during the ICARUS T600 run at the LNGS underground laboratory, where the cosmic ray flux was suppressed by a factor ∼106 by 3400 m water equivalent shielding. No appreciable distortion has been observed, confirming that the effects measured on surface are actually due to ion space charge.

Energy spectra, intensity and composition of the CERN to Gran Sasso CNGS neutrino beam for nu_mu--&gt;nu_tau and nu_mu--&gt;nu_e oscillation searches are presented. The associated beam systematics, which is the major ingredient for the nu_mu--&gt;nu_e search sensitivity, are obtained from the study of the previous CERN WANF.

A number of innovative experiments dedicated to neutrino oscillations and rare event physics, such as direct searches for dark matter particles or neutrinoless double beta decays, are using liquefied noble-gases, particularly Liquid Argon (LAr), as detection media. Among many advantages of noble liquids, from the detection point of view, the most important ones are high scintillation and ionisation yields, possible long drift paths of ionisation electrons and feasible large detector masses. LAr is sufficiently dense and relatively cheap and therefore is the only adequate noble liquid for huge volumes. This paper describes a particle detection system that exploits the prompt signals from the scintillation light produced by ionising particles in LAr. The detector has been exposed to cosmic rays. The system performance in terms of trigger efficiency and timing resolution, with a view to its application in neutrino detectors, is presented.

In the context of a two-flavour approximation we reinterpret the published NOMAD limit on νμ→ντ oscillations in terms of νe→ντ oscillations. At 90% C.L. we obtain sin22θeτ<5.2×10−2 for large Δm2, while for sin22θeτ=1 the confidence region includes Δm2<11 eV2/c4.

In the neutron-antineutron oscillation experiment at ILL the divergence of the free flying cold neutron beam was strongly reduced without loss of intensity by the use of a 34 m long neutron-optical horn system. The divergence reduction was accurately studied in order to maintain the total width of the neutron beam below 1.1 m after a neutron free flight distance of about 80 m. The fabrication and performance of this system are described.

We report on a direct search in NOMAD for a new 33.9 MeV/c2 neutral particle (X) produced in pion decay in flight, π→μX followed by the decay X→νe+e−. Both decays are postulated to occur to explain the time anomaly observed by the KARMEN experiment. From the analysis of the data collected during the 1996–1998 runs with 4.1×1019 protons on target, a single candidate event consistent with background expectations was found. The search is sensitive to a pion branching ratio BR(π→μX)>3.7×10−15, significantly smaller than previous experimental limits.

Results of a detailed study of strange particle production in neutrino neutral current interactions are presented using the data from the NOMAD experiment. Integral yields of neutral strange particles (Ks0, Λ, Λ¯) have been measured. Decays of resonances and heavy hyperons with an identified Ks0 or Λ in the final state have been analyzed. Clear signals corresponding to K⋆± and Σ(1385)± have been observed. First results on the measurements of the Λ polarization in neutral current interactions have been obtained.

First measurements of K*(892) mesons production properties and their spin alignment in nu_mu charged current (CC) and neutral current (NC) interactions are presented. The analysis of the full data sample of the NOMAD experiment is performed in different kinematic regions. For K*+ and K*- mesons produced in nu_mu CC interactions and decaying into K0 pi+/- we have found the following yields per event: (2.6 +/- 0.2 (stat.) +/- 0.2 (syst.))% and (1.6 +/- 0.1 (stat.) +/- 0.1 (syst.))% respectively, while for the K*+ and K*- mesons produced in nu NC interactions the corresponding yields per event are: (2.5 +/- 0.3 (stat.) +/- 0.3 (syst.))% and (1.0 +/- 0.3 (stat.) +/- 0.2 (syst.))%. The results obtained for the rho00 parameter, 0.40 +/- 0.06 (stat) +/- 0.03 (syst) and 0.28 +/- 0.07 (stat) +/- 0.03 (syst) for K*+ and K*- produced in nu_mu CC interactions, are compared to theoretical predictions tuned on LEP measurements in e+e- annihilation at the Z0 pole. For K*+ mesons produced in nu NC interactions the measured rho00 parameter is 0.66 +/- 0.10 (stat) +/- 0.05 (syst).

The HARP Collaboration has presented measurements of the double-differential ${\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}$ production cross section in the range of momentum $100 \text{MeV}/c\ensuremath{\leqslant}p\ensuremath{\leqslant}800 \text{MeV}/c$ and angle $0.35 \text{rad}\ensuremath{\leqslant}\ensuremath{\theta}\ensuremath{\leqslant}2.15 \text{rad}$ with proton beams hitting thin nuclear targets. In many applications the extrapolation to long targets is necessary. In this article the analysis of data taken with long (one interaction length) solid cylindrical targets made of carbon, tantalum, and lead is presented. The data were taken with the large-acceptance HARP detector in the T9 beam line of the CERN proton synchrotron. The secondary pions were produced by beams of protons with momenta of 5, 8, and $12\text{GeV}/c$. The tracking and identification of the produced particles were performed using a small-radius cylindrical time projection chamber placed inside a solenoidal magnet. Incident protons were identified by an elaborate system of beam detectors. Results are obtained for the double-differential yields per target nucleon ${\mathrm{d}}^{2}\ensuremath{\sigma}/\mathrm{d}p\mathrm{d}\ensuremath{\theta}$. The measurements are compared with predictions of the MARS and GEANT4 Monte Carlo simulations.

A description of the response of the NOMAD electromagnetic calorimeter to electrons and photons is discussed. In particular, the dependence of the two-dimensional shower shape on the angle and energy of the incident particle is parametrized by analytical functions. Some applications to the neutrino event reconstruction are also reported.

The CERN to Gran Sasso neutrino facility (CNGS) is designed to study the νμ→ντ oscillation with a high intensity neutrino beam sent to the ICARUS and OPERA long base-line experiments searching for ντ appearance at LNGS. An ambitious and demanding project aimed to the protection of electronics against radiation has been devised and carried out in a very short time in 2008. Therefore the facility ran smoothly from June 18th to November 3rd 2008 delivering almost 2.0⋅1019 proton on target. As a successive phase the CNGS facility could be addressed to the search of νμ→νe subleading transitions driven by θ13 mixing angle with a more intense off-axis neutrino beam. An increase of nearly an order of magnitude with respect to T2K expected sensitivity should be reached by exposing ∼ 20 kt liquid Argon TPC detector shallow-depth at the Gran Sasso site.

We discuss the ICARUS T600 detector capabilities in electromagnetic shower reconstruction through the analysis of a sample of 212 events, coming from the 2001 Pavia surface test run, of hadronic interactions leading to the production of $π^{0}$ mesons. Methods of shower energy and shower direction measurements were developed and the invariant mass of the photon pairs was reconstructed. The ($γ$,$γ$) invariant mass was found to be consistent with the value of the $π^0$ mass. The resolution of the reconstructed $π^0$ mass was found to be equal to 27.3%. An improved analysis, carried out in order to clean the full event sample from the events measured in the crowded environment, mostly due to the trigger conditions, gave a $π^0$ mass resolution of 16.1%, significantly better than the one evaluated for the full event sample. The trigger requirement of the coincidence of at least four photomultiplier signals favored the selection of events with a strong pile up of cosmic ray tracks and interactions. Hence a number of candidate $π^0$ events were heavily contaminated by other tracks and had to be rejected. Monte Carlo simulations of events with $π^0$ production in hadronic and neutrino interactions confirmed the validity of the shower energy and shower direction reconstruction methods applied to the real data.

A search for exotic Θ+ baryon via Θ+→p+K0 S decay mode in the NOMAD νμN data is reported. The special background generation procedure was developed. The proton identification criteria are tuned to maximize the sensitivity to the Θ+ signal as a function of xF which allows to study the Θ+ production mechanism. We do not observe any evidence for the Θ+ state in the NOMAD data. We provide an upper limit on Θ+ production rate at 90% CL as 2.13×10-3 per neutrino interaction.

Energy spectra, intensity and composition of the CERN to Gran Sasso CNGS neutrino beam for ν μ → ν T search are presented with the first results of the beam commissioning and operations.