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A bstract The NEXT experiment aims to observe the neutrinoless double beta decay of 136 Xe in a high-pressure xenon gas TPC using electroluminescence (EL) to amplify the signal from ionization. One of the main advantages of this technology is the possibility to reconstruct the topology of events with energies close to Q ββ . This paper presents the first demonstration that the topology provides extra handles to reject background events using data obtained with the NEXT-DEMO prototype. Single electrons resulting from the interactions of 22 Na 1275 keV gammas and electronpositron pairs produced by conversions of gammas from the 228 Th decay chain were used to represent the background and the signal in a double beta decay. These data were used to develop algorithms for the reconstruction of tracks and the identification of the energy deposited at the end-points, providing an extra background rejection factor of 24 . 3 ± 1 . 4 (stat.)%, while maintaining an efficiency of 66 . 7 ± 1 . % for signal events.

Abstract We performed a novel Σ+p scattering experiment at the J-PARC Hadron Experimental Facility. Approximately 2400 Σ+p elastic scattering events were identified from 4.9 × 107 tagged Σ+ particles in the Σ+ momentum range 0.44–0.80 GeV/c. The differential cross sections of the Σ+p elastic scattering were derived with much better precision than in previous experiments. The obtained differential cross sections were approximately 2 mb/sr or less, which were not as large as those predicted by the fss2 and FSS models based on the quark cluster model in the short-range region. By performing phase-shift analyses for the obtained differential cross sections, we experimentally derived the phase shifts of the 3S1 and 1P1 channels for the first time. The phase shift of the 3S1 channel, where a large repulsive core was predicted owing to the Pauli effect between quarks, was evaluated as $20^\\circ \\lt |\\delta _{^3S_1}|\\lt 35^\\circ$. If the sign of $\\delta _{^3S_1}$ is assumed to be negative, the interaction in this channel is moderately repulsive, as the Nijmegen extended-sort-core models predicted.

A new hyperon-proton scattering experiment, dubbed J-PARC E40, was performed to measure differential cross sections of the Σ + p , Σ − p elastic scatterings and the Σ − p → Λ n scattering by identifying a lot of Σ particles in the momentum ranging from 0.4 to 0.8 GeV/ c produced by the π ± p → K + Σ ± reactions. We successfully measured the differential cross sections of these three channels with a drastically improved accuracy with a fine angular step. These new data will become important experimental constraints to improve the theories of the two-body baryon-baryon interactions. Following this success, we proposed a new experiment to measure the differential cross sections and spin observables by using a highly polarized Λ beam for providing quantitative information on the Λ N interaction. The results of three Σ p channels and future prospects of the Λ p scattering experiment are described.

NEXT is an experiment dedicated to neutrinoless double beta decay searches in xenon. The detector is a TPC, holding 100 kg of high-pressure xenon enriched in the 136Xe isotope. It is under construction in the Laboratorio Subterráneo de Canfranc in Spain, and it will begin operations in 2015. The NEXT detector concept provides an energy resolutionbetter than 1% FWHM and a topological signal that can be used to reduce the background. Furthermore, the NEXT technology can be extrapolated to a 1 ton-scale experiment.

A high statistics ∑p scattering experiment has been performed at the K1.8 beamline in the J-PARC Hadron Experimental Facility. Data for momentum-tagged ∑− beam running in a liquid hydrogen target were accumulated by detecting the π−p→K+∑− reaction with a high intensity π− beam of 20 M/spill. The number of the Σ− beam was about 1.7 × 107 in total. The ∑−ρ elastic scattering and the ∑−p → Λn inelastic scattering events were successfully observed with about 100 times larger statistics than that in past experiments.

A bstract NEXT-100 is an electroluminescent high-pressure xenon gas time projection chamber that will search for the neutrinoless double beta (0 νββ ) decay of 136 Xe. The detector possesses two features of great value for 0 νββ searches: energy resolution better than 1% FWHM at the Q value of 136 Xe and track reconstruction for the discrimination of signal and background events. This combination results in excellent sensitivity, as discussed in this paper. Material-screening measurements and a detailed Monte Carlo detector simulation predict a background rate for NEXT-100 of at most 4 × 10 −4 counts keV −1 kg −1 yr −1 . Accordingly, the detector will reach a sensitivity to the 0 νββ -decay half-life of 2.8 × 10 25 years (90% CL) for an exposure of 100 kg·year, or 6.0 × 10 25 years after a run of 3 effective years.

In the J-PARC E27 experiment, we search for a K − pp bound state via the d ( π + , K + ) reaction at 1.7 GeV/ c at the K1.8 beam line. The binding energy and decay width of the K − pp bound state can be obtained in the missing mass measurement with a good energy resolution of 2 MeV/ c 2 . A range counter array (RCA) was constructed to detect the two high-momentum protons from the K − pp decay and to reduce the background such as quasi-free hyperon production. Recently, we have carried out a pilot run in June, 2012. The d ( π + , K + ) missing-mass spectrum has been obtained for the first time. In this report, an overview of the E27 experiment and a preliminary result on this pilot run are presented.

Abstract The CMS detector, including its muon system, has been operating at the CERN LHC in increasingly challenging conditions for about 15 years. The muon detector was designed to provide excellent triggering and track reconstruction for muons produced in proton–proton collisons at an instantaneous luminosity ( $$\\mathcal {L}$$ L ) of $$1 \\times 10^{34}$$ 1 × 10 34  cm $$^{-2}$$ - 2 s $$^{-1}$$ - 1 . During the Run 2 data-taking period (2015–2018), the LHC achieved an instantaneous luminosity of twice its design value, resulting in larger background rates and making the efficient detection of muons more difficult. While some backgrounds result from natural radioactivity, cosmic rays, and interactions of the circulating protons with residual gas in the beam pipe, the dominant source of background hits in the muon system arises from proton–proton interactions themselves. Charged hadrons leaving the calorimeters produce energy deposits in the muon chambers. In addition, high-energy particles interacting in the hadron calorimeter and forward shielding elements generate thermal neutrons, which leak out of the calorimeter and shielding structures, filling the CMS cavern. We describe the method used to measure the background rates in the various muon subsystems. These rates, in conjunction with simulations, can be used to estimate the expected backgrounds in the High-Luminosity LHC. This machine will run for at least 10 years starting in 2029 reaching an instantaneous luminosity of $$\\mathcal {L} = 5 \\times \\text {10}^\\text {34}\\,\\text {cm}^\\text {-2}\\,\\text {s}^\\text {-1}$$ L = 5 × 10 34 cm -2 s -1 and increasing ultimately to $$\\mathcal {L} = 7.5 \\times \\text {10}^\\text {34}\\,\\text {cm}^\\text {-2}\\,\\text {s}^\\text {-1}$$ L = 7.5 × 10 34 cm -2 s -1 . These background estimates have been a key ingredient for the planning and design of the muon detector upgrade.

We have measured an inclusive missing-mass spectrum of the $d(\\pi ^+ , K^+ )$ reaction at a pion incident momentum of 1.69 GeV/$c$ at laboratory scattering angles between $2^\\circ$ and $16^\\circ$ with a missing-mass resolution of $2.7 \\pm 0.1$MeV/$c^{2}$ (FWHM) at the missing mass of 2.27 GeV/$c^{2}$. In this letter, we first try to understand the spectrum as a simple quasi-free picture based on several known elementary cross sections, considering the neutron/proton Fermi motion in the deuteron. While gross spectrum structures are well understood in this picture, we have observed two distinct deviations; one peculiar enhancement at 2.13 GeV/$c^{2}$ is due to the $\\Sigma N$ cusp, and the other notable feature is a shift of a broad bump structure, mainly originating from hyperon resonance productions of $\\Lambda (1405)$ and $\\Sigma (1385)^{+ /0}$, by about 22.4 $\\pm$ 0.4 (stat.) $^{+2.7}_{-1.7}$ (syst.) MeV/$c^{2}$ toward the low-mass side, which is calculated in the kinematics of a proton at rest as the target.

We have observed a “$K^{-}pp$”-like structure in the $d(\\pi ^{+ },K^{+ })$ reaction at 1.69 GeV$/c$. In this reaction, a $\\Lambda (1405)$ hyperon resonance is expected to be produced as a doorway to form $K^{-}pp$ through the $\\Lambda ^{\\ast }p\\rightarrow K^{-}pp$ process. However, most of the $\\Lambda (1405)$ produced would escape from the deuteron without secondary reactions. Therefore, coincidence of high-momentum ($>$250 MeV$/c$) proton(s) at large emission angles ($39^\\circ \\lt \\theta _{\\rm lab.} \\lt 122^\\circ$) was requested to enhance the signal-to-background ratio. A broad enhancement in the proton coincidence spectra is observed around the missing mass of 2.27 GeV$/c^2$, which corresponds to the $K^{-}pp$ binding energy of 95 ^{+18}_{-17}$ (stat.) ^{+30}_{-21}$ (syst.) MeV and the width of 162 ^{+87}_{-45}$ (stat.) ^{+66}_{-78}$ (syst.) MeV.