Absolute neutrino cross section measurements are presently limited by uncertainties on
ν
fluxes. In this paper, we propose a technique that is based on the reconstruction of large angle positrons in ...the decay tunnel to identify three-body semileptonic
K
+
→
e
+
π
0
ν
e
decays. This tagging facility operated in positron counting mode (“event count mode”) can be employed to determine the absolute
ν
e
flux at the neutrino detector with
O
(
1
%
)
precision. Facilities operated in “event by event tag mode” i.e. tagged neutrino beams that exploit the time coincidence of the positron at source and the
ν
e
interaction at the detector, are also discussed.
We present an optimization of the hadron focusing system for a low-energy high intensity conventional neutrino beam (super-beam) proposed on the basis of the HP-SPL at CERN with a beam power of 4 MW ...and an energy of 4.5 GeV. The far detector would be a 440 kton Water Cherenkov detector (MEMPHYS) located at a baseline of 130 km in the Fréjus site. The neutrino fluxes simulation relies on a new GEANT4 based simulation coupled with an optimization algorithm based on the maximization of the sensitivity limit on the
θ
13
mixing angle. A new configuration adopting a multiple horn system with solid targets is proposed which improves the sensitivity to
θ
13
and the CP violating phase
δ
CP
.
The OPERA experiment at the Gran Sasso underground laboratory is searching for νμ → ντ oscillations in appearance mode in the CNGS neutrino beam. Four ντ candidate events have been found so far, ...using a sub-sample of data from the 2008-2012 runs. Given the number of analysed events and the low background, νμ → ντ oscillations are established with a significance of 4.2 σ. In this paper the data analysis is discussed, with emphasis on the background constraints obtained using dedicated data-driven control samples. We present also the analysis of the τ neutrino and electron neutrino data in the framework of the 3+1 sterile neutrino model. The measurement of the muon charge ratio in the collected cosmic ray sample is also reported.
New results from T2K Longhin, A.
EPJ Web of Conferences,
01/2017, Letnik:
164
Journal Article, Conference Proceeding
Recenzirano
Odprti dostop
The T2K experiment is a 295-km long-baseline neutrino experiment in Japan employing an off-axis muon neutrino beam with a ~ 0.6 GeV peak energy. The beam, produced from 30-GeV protons at the J-PARC ...complex on the Pacific coast, is directed to the Super-Kamiokande detector. T2K released the first long-baseline measurement of a nonzero value for the θ13 mixing parameter through the observation of electron neutrino appearance (vµ → ve) and produced the most precise measurement of θ23 through the observation of muon neutrino disappearance (vµ → vµ). T2K data, in combination with reactor experiments, also excludes at 90% C.L. a significant region of the Dirac CP phase: δCP < -3.02(-1.87) and δCP > -0.49(-0.98) for the normal (inverted) hierarchy. A full joint appearance and disappearance fit including both neutrino (7×1020 protons on target, PoT) and anti-neutrino (4 × 1020 PoT) data and, for the first time, a constraint from water target data in the near detector, is presented yielding improved sensitivity on δCP and improved precision on sin2 2θ23 and the atmospheric mass splitting.
The probability of large-angle scattering for multi-GeV muons in lead targets with a thickness of O(10 - 1 ) radiation lengths is studied. The new estimates presented here are based both on ...simulation programs (GEANT4 libraries) and theoretical calculations. In order to validate the results provided by simulation, a comparison is drawn with experimental data from the literature. This study is particularly relevant when applied to muons originating from νμ CC interactions of CNGS beam neutrinos. In that circumstance the process under study represents the dominant background for the νμ → ντ search in the τ→ μ channel for the OPERA experiment at LNGS. Finally we also investigate, in the CNGS context, possible contributions from the muon photo-nuclear process which might in principle also produce a large-angle muon scattering signature in the detector.
The longitudinal segmentation of shashlik calorimeters is challenged by dead zones and non-uniformities introduced by the light collection and readout system. This limitation can be overcome by ...direct fiber–photosensor coupling, avoiding routing and bundling of the wavelength shifter fibers and embedding ultra-compact photosensors (SiPMs) in the bulk of the calorimeter. We present the first experimental test of this readout scheme performed at the CERN PS-T9 beamline in 2015 with negative particles in the 1–5GeV energy range. In this paper, we demonstrate that the scheme does not compromise the energy resolution and linearity compared with standard light collection and readout systems. In addition, we study the performance of the calorimeter for partially contained charged hadrons to assess the e/π separation capability and the response of the photosensors to direct ionization.
An upgrade of the Near Detector of the T2K long baseline neutrino oscillation experiment, ND280, has been proposed. This upgrade will include two new Time Projection Chambers, each equipped with 16 ...resistive Micromegas modules for gas amplification. A first prototype of resistive Micromegas has been designed, built, installed in the HARP field cage, and exposed to a beam of charged particles at CERN. The data have been used to characterize the performances of the resistive Micromegas module. A spatial resolution of 300 μm and a deposited energy resolution of 9% were observed for horizontal electrons crossing the TPCs at 30 cm from the anode. Such performances fully satisfy the requirements for the upgrade of the ND280 TPC.
Effective longitudinal segmentation of shashlik calorimeters can be achieved taking advantage of the compactness and reliability of silicon photomultipliers. These photosensors can be embedded in the ...bulk of the calorimeter and are employed to design very compact shashlik modules that sample electromagnetic and hadronic showers every few radiation lengths. In this paper, we discuss the performance of a calorimeter made up of 12 such modules and able to sample showers every ~4X 0 . In summer 2016, this prototype has been exposed to electrons, muons, and hadrons at CERN PS (East Area T9 beamline). The performances in terms of energy resolution, linearity, response to minimum ionizing particles, and reconstruction of the shower profile are discussed.
An upgrade of the near detector of the T2K long baseline neutrino oscillation experiment is currently being conducted. This upgrade will include two new Time Projection Chambers, each equipped with ...16 charge readout resistive Micromegas modules.
A procedure to validate the performance of the detectors at different stages of production has been developed and implemented to ensure a proper and reliable operation of the detectors once installed. A dedicated X-ray test bench is used to characterize the detectors by scanning each pad individually and to precisely measure the uniformity of the gain and the deposited energy resolution over the pad plane. An energy resolution of about 10% is obtained.
A detailed physical model has been developed to describe the charge dispersion phenomena in the resistive Micromegas anode. The detailed physical description includes initial ionization, electron drift, diffusion effects and the readout electronics effects. The model provides an excellent characterization of the charge spreading of the experimental measurements and allowed the simultaneous extraction of gain and charge spreading information of the modules.
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