The T2K experiment observes indications of ν(μ) → ν(e) appearance in data accumulated with 1.43×10(20) protons on target. Six events pass all selection criteria at the far detector. In a three-flavor ...neutrino oscillation scenario with |Δm(23)(2)| = 2.4×10(-3) eV(2), sin(2)2θ(23) = 1 and sin(2)2θ(13) = 0, the expected number of such events is 1.5±0.3(syst). Under this hypothesis, the probability to observe six or more candidate events is 7×10(-3), equivalent to 2.5σ significance. At 90% C.L., the data are consistent with 0.03(0.04) < sin(2)2θ(13) < 0.28(0.34) for δ(CP) = 0 and a normal (inverted) hierarchy.
Studies of silicon photomultipliers at cryogenic temperatures Collazuol, G.; Bisogni, M.G.; Marcatili, S. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
02/2011, Letnik:
628, Številka:
1
Journal Article
Recenzirano
We investigate the behavior of silicon photomultipliers (SiPMs) at low temperatures:
I–
V characteristics, breakdown voltage, dark noise, afterpulsing, crosstalk, pulse shape, gain and photon ...detection efficiency are studied as a function of temperature in the range
50
K
<
T
<
320
K
. We discuss our measurements on the basis of the temperature dependent properties of silicon and of the models related to carrier generation, transport and multiplication in high electric field. We conclude that SiPMs provide an excellent alternative to vacuum tube photomultipliers (PMTs) in low temperature environments, even better than in room temperature ones: in particular they excel in the interval
100
K
<
T
<
200
K
.
Supernova detection is a major objective of the Super-Kamiokande (SK) experiment. In the next stage of SK (SK-Gd), gadolinium (Gd) sulfate will be added to the detector, which will improve the ...ability of the detector to identify neutrons. A core-collapse supernova (CCSN) will be preceded by an increasing flux of neutrinos and antineutrinos, from thermal and weak nuclear processes in the star, over a timescale of hours; some of which may be detected at SK-Gd. This could provide an early warning of an imminent CCSN, hours earlier than the detection of the neutrinos from core collapse. Electron antineutrino detection will rely on inverse beta decay events below the usual analysis energy threshold of SK, so Gd loading is vital to reduce backgrounds while maximizing detection efficiency. Assuming normal neutrino mass ordering, more than 200 events could be detected in the final 12 hr before core collapse for a 15-25 solar mass star at around 200 pc, which is representative of the nearest red supergiant to Earth, -Ori (Betelgeuse). At a statistical false alarm rate of 1 per century, detection could be up to 10 hr before core collapse, and a pre-supernova star could be detected by SK-Gd up to 600 pc away. A pre-supernova alert could be provided to the astrophysics community following gadolinium loading.
Arrays of single photon avalanche diodes (SPADs) fabricated in a 150 nm CMOS technology have been exposed to neutrons up to fluences of about <inline-formula> <tex-math notation="LaTeX">4.3 \times ...10^{10}~1 </tex-math></inline-formula> MeV neutron equivalent cm<inline-formula> <tex-math notation="LaTeX">^{-2} </tex-math></inline-formula>, with fluxes around <inline-formula> <tex-math notation="LaTeX">3 \times 10^{6}~1 </tex-math></inline-formula> MeV neutron equivalent cm<inline-formula> <tex-math notation="LaTeX">^{-2}\text{s}^{-1} </tex-math></inline-formula>. Dark count rate (DCR) was monitored during irradiation and for some time, from 5 to 23 min, depending on the irradiation step, at the end of the irradiation interval to investigate the dynamics of defect formation and short-term annealing. Measurements were performed both on single- and on dual-layer devices, where SPAD arrays are face to face bonded and read out in coincidence. A range of different DCR behaviors were detected after single neutron interaction with the device substrate, including in particular partial performance recovery following a logarithmic relaxation process, but also damped oscillation phenomena, sudden step-shaped changes, and the emergence of RTS-like fluctuations, pointing to different defect reordering dynamics.
The possibility to detect fast neutrons as a distinct signal from that one of γ-rays background is surely of great importance for several topics, spanning from homeland security to radiation ...monitoring in nuclear physics research plants. Nowadays, Helium-3 based detectors are extremely expensive, while the use of large volume liquid scintillators presents serious concerns related to spillage risks and waste disposal. A very attractive alternative is the use of commercially available solid scintillators, which exploits an aromatic polymer matrix entrapping very high loadings of primary dye, thereby enabling the use of pulse shape analysis (PSA) to discriminate between fast neutrons and γ-rays. In this work, we analyse in detail the optical features of a solid scintillator composed by polymethylphenylsiloxane (PMPS) as base polymer loaded with moderate amounts of 2,5-diphenyloxazole (PPO). Furthermore, fluorescence decay kinetics have been correlated to the observed pulse shape discrimination capabilities of this radiation and thermally resistant scintillator, whose performances have been discussed in terms of conformational features and excimers formation revealed by the optical analyses.
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.
The ENUBET project is aimed at designing and experimentally demonstrating the concept of monitored neutrino beams. These novel beams are enhanced by an instrumented decay tunnel, whose detectors ...reconstruct large-angle charged leptons produced in the tunnel and give a direct estimate of the neutrino flux at the source. These facilities are thus the ideal tool for high-precision neutrino cross-section measurements at the GeV scale because they offer superior control of beam systematics with respect to existing facilities. In this paper, we present the first end-to-end design of a monitored neutrino beam capable of monitoring lepton production at the single particle level. This goal is achieved by a new focusing system without magnetic horns, a 20 m normal-conducting transfer line for charge and momentum selection, and a 40 m tunnel instrumented with cost-effective particle detectors. Employing such a design, we show that percent precision in cross-section measurements can be achieved at the CERN SPS complex with existing neutrino detectors.
Neutral current (NC) interactions of atmospheric neutrinos on oxygen form one of the major backgrounds in the search for supernova relic neutrinos with water-based Cherenkov detectors. The NC channel ...is dominated by neutrino quasielastic (NCQE) scattering off nucleons inside O16 nuclei. In this paper we report the first measurement of NCQE cross section using atmospheric neutrinos at Super-Kamiokande (SK). The measurement used 2,778 live days of SK-IV data with a fiducial volume of 22.5 kiloton water. Within the visible energy window of 7.5–29.5 MeV, we observed 117 events compared to the expected 71.9 NCQE signal and 53.1 background events. Weighted by the atmospheric neutrino spectrum from 160 MeV to 10 GeV, the flux averaged NCQE cross section is measured to be (1.01±0.17(stat.)−0.30+0.78(sys.))×10−38 cm2.
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.
Abstract
A new event reconstruction algorithm based on a maximum likelihood method has been developed for Super-Kamiokande. Its improved kinematic and particle identification capabilities enable the ...analysis of atmospheric neutrino data in a detector volume 32% larger than previous analyses and increase the sensitivity to the neutrino mass hierarchy. Analysis of a 253.9 kton$\cdot$year exposure of the Super-Kamiokande IV atmospheric neutrino data has yielded a weak preference for the normal hierarchy, disfavoring the inverted hierarchy at 74% assuming oscillations at the best fit of the analysis.
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