705 research outputs found

    u-RANIA: a neutron detector based on \mu -RWELL technology

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    In the framework of the ATTRACT-uRANIA project, funded by the European Community, we are developing an innovative neutron imaging detector based on micro-Resistive WELL (μ\mu -RWELL) technology. The μ\mu -RWELL, based on the resistive detector concept, ensuring an efficient spark quenching mechanism, is a highly reliable device. It is composed by two main elements: a readout-PCB and a cathode. The amplification stage for this device is embedded in the readout board through a resistive layer realized by means of an industrial process with DLC (Diamond-Like Carbon). A thin layer of B4_4C on the copper surface of the cathode allows the thermal neutrons detection through the release of 7^7Li and α\alpha particles in the active volume. This technology has been developed to be an efficient and convenient alternative to the 3^3He shortage. The goal of the project is to prove the feasibility of such a novel neutron detector by developing and testing small planar prototypes with readout boards suitably segmented with strip or pad read out, equipped with existing electronics or readout in current mode. Preliminary results from the test with different prototypes, showing a good agreement with the simulation, will be presented together with construction details of the prototypes and the future steps of the project.Comment: Prepared for the INSTR20 Conference Proceeding for JINS

    A model to explain angular distributions of J/ψJ/\psi and ψ(2S)\psi(2S) decays into ΛΛ\Lambda\overline{\Lambda} and Σ0Σ0\Sigma^0\overline{\Sigma}^0

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    BESIII data show a particular angular distribution for the decay of the J/ψJ/\psi and ψ(2S)\psi(2S) mesons into the hyperons ΛΛ\Lambda\overline{\Lambda} and Σ0Σ0\Sigma^0\overline{\Sigma}^0. More in details the angular distribution of the decay ψ(2S)Σ0Σ0\psi(2S) \to \Sigma^0\overline{\Sigma}^0 exhibits an opposite trend with respect to that of the other three channels: J/ψΛΛJ/\psi \to \Lambda\overline{\Lambda}, J/ψΣ0Σ0J/\psi \to \Sigma^0\overline{\Sigma}^0 and ψ(2S)ΛΛ\psi(2S) \to \Lambda\overline{\Lambda}. We define a model to explain the origin of this phenomenon.Comment: 6 pages, 7 figures, to be published in Chinese Physics

    The HPS electromagnetic calorimeter

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    The Heavy Photon Search experiment (HPS) is searching for a new gauge boson, the so-called “heavy photon.” Through its kinetic mixing with the Standard Model photon, this particle could decay into an electron-positron pair. It would then be detectable as a narrow peak in the invariant mass spectrum of such pairs, or, depending on its lifetime, by a decay downstream of the production target. The HPS experiment is installed in Hall-B of Jefferson Lab. This article presents the design and performance of one of the two detectors of the experiment, the electromagnetic calorimeter, during the runs performed in 2015–2016. The calorimeter's main purpose is to provide a fast trigger and reduce the copious background from electromagnetic processes through matching with a tracking detector. The detector is a homogeneous calorimeter, made of 442 lead-tungstate (PbWO4) scintillating crystals, each read out by an avalanche photodiode coupled to a custom trans-impedance amplifier

    Determination of the proton spin structure functions for 0.05 \u3c Q(2) \u3c 5GeV(2) using CLAS

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    We present the results of our final analysis of the full data set of g(1)(p) (Q(2)), the spin structure function of the proton, collected using CLAS at Jefferson Laboratory in 2000-2001. Polarized electrons with energies of 1.6, 2.5, 4.2, and 5.7 GeV were scattered from proton targets ((NH3)-N-15 dynamically polarized along the beam direction) and detected with CLAS. From the measured double spin asymmetries, we extracted virtual photon asymmetries A(1)(p) and A(2)(p) and spin structure functions g(1)(p) and g(2)(p) over a wide kinematic range (0.05 GeV2 \u3c Q(2) \u3c 5 GeV2 and 1.08 GeV\u3c W \u3c 3 GeV) and calculated moments of g(1)(p). We compare our final results with various theoretical models and expectations, as well as with parametrizations of the world data. Our data, with their precision and dense kinematic coverage, are able to constrain fits of polarized parton distributions, test pQCD predictions for quark polarizations at large x, offer a better understanding of quark-hadron duality, and provide more precise values of higher twist matrix elements in the framework of the operator product expansion

    Search for the decay J/ψγ+invisibleJ/\psi\to\gamma + \rm {invisible}

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    We search for J/ψJ/\psi radiative decays into a weakly interacting neutral particle, namely an invisible particle, using the J/ψJ/\psi produced through the process ψ(3686)π+πJ/ψ\psi(3686)\to\pi^+\pi^-J/\psi in a data sample of (448.1±2.9)×106(448.1\pm2.9)\times 10^6 ψ(3686)\psi(3686) decays collected by the BESIII detector at BEPCII. No significant signal is observed. Using a modified frequentist method, upper limits on the branching fractions are set under different assumptions of invisible particle masses up to 1.2  GeV/c2\mathrm{\ Ge\kern -0.1em V}/c^2. The upper limit corresponding to an invisible particle with zero mass is 7.0×107\times 10^{-7} at the 90\% confidence level

    Precise Measurements of Branching Fractions for Ds+D_s^+ Meson Decays to Two Pseudoscalar Mesons

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    We measure the branching fractions for seven Ds+D_{s}^{+} two-body decays to pseudo-scalar mesons, by analyzing data collected at s=4.1784.226\sqrt{s}=4.178\sim4.226 GeV with the BESIII detector at the BEPCII collider. The branching fractions are determined to be B(Ds+K+η)=(2.68±0.17±0.17±0.08)×103\mathcal{B}(D_s^+\to K^+\eta^{\prime})=(2.68\pm0.17\pm0.17\pm0.08)\times10^{-3}, B(Ds+ηπ+)=(37.8±0.4±2.1±1.2)×103\mathcal{B}(D_s^+\to\eta^{\prime}\pi^+)=(37.8\pm0.4\pm2.1\pm1.2)\times10^{-3}, B(Ds+K+η)=(1.62±0.10±0.03±0.05)×103\mathcal{B}(D_s^+\to K^+\eta)=(1.62\pm0.10\pm0.03\pm0.05)\times10^{-3}, B(Ds+ηπ+)=(17.41±0.18±0.27±0.54)×103\mathcal{B}(D_s^+\to\eta\pi^+)=(17.41\pm0.18\pm0.27\pm0.54)\times10^{-3}, B(Ds+K+KS0)=(15.02±0.10±0.27±0.47)×103\mathcal{B}(D_s^+\to K^+K_S^0)=(15.02\pm0.10\pm0.27\pm0.47)\times10^{-3}, B(Ds+KS0π+)=(1.109±0.034±0.023±0.035)×103\mathcal{B}(D_s^+\to K_S^0\pi^+)=(1.109\pm0.034\pm0.023\pm0.035)\times10^{-3}, B(Ds+K+π0)=(0.748±0.049±0.018±0.023)×103\mathcal{B}(D_s^+\to K^+\pi^0)=(0.748\pm0.049\pm0.018\pm0.023)\times10^{-3}, where the first uncertainties are statistical, the second are systematic, and the third are from external input branching fraction of the normalization mode Ds+K+Kπ+D_s^+\to K^+K^-\pi^+. Precision of our measurements is significantly improved compared with that of the current world average values

    Measurement of proton electromagnetic form factors in e+eppˉe^+e^- \to p\bar{p} in the energy region 2.00-3.08 GeV

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    The process of e+eppˉe^+e^- \rightarrow p\bar{p} is studied at 22 center-of-mass energy points (s\sqrt{s}) from 2.00 to 3.08 GeV, exploiting 688.5~pb1^{-1} of data collected with the BESIII detector operating at the BEPCII collider. The Born cross section~(σppˉ\sigma_{p\bar{p}}) of e+eppˉe^+e^- \rightarrow p\bar{p} is measured with the energy-scan technique and it is found to be consistent with previously published data, but with much improved accuracy. In addition, the electromagnetic form-factor ratio (GE/GM|G_{E}/G_{M}|) and the value of the effective (Geff|G_{\rm{eff}}|), electric (GE|G_E|) and magnetic (GM|G_M|) form factors are measured by studying the helicity angle of the proton at 16 center-of-mass energy points. GE/GM|G_{E}/G_{M}| and GM|G_M| are determined with high accuracy, providing uncertainties comparable to data in the space-like region, and GE|G_E| is measured for the first time. We reach unprecedented accuracy, and precision results in the time-like region provide information to improve our understanding of the proton inner structure and to test theoretical models which depend on non-perturbative Quantum Chromodynamics
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