1,721,732 research outputs found
Precision measurement of the η → π +π −π 0Dalitz plot distribution with the KLOE detector
No full textAbstract: Using 1.6 fb−1of e+e−→ φ → ηγ data collected with the KLOE detector at DAΦNE, the Dalitz plot distribution for the η → π+π−π0decay is studied with the world’s largest sample of ∼ 4.7 · 106events. The Dalitz plot density is parametrized as a polynomial expansion up to cubic terms in the normalized dimensionless variables X and Y. The experiment is sensitive to all charge conjugation conserving terms of the expansion, including a gX2Y term. The statistical uncertainty of all parameters is improved by a factor two with respect to earlier measurements. © 2016, The Author(s)
Measurement of the charge asymmetry for the KS → πeν decay and test of CPT symmetry with the KLOE detector
No full textUsing 1.63 fb−1 of integrated luminosity collected by the KLOE experiment about 7 × 104KS → π±e∓ν decays have been reconstructed. The measured value of the charge asymmetry for this decay is AS = (−4.9 ± 5.7stat ± 2.6syst) × 10−3, which is almost twice more precise than the previous KLOE result. The combination of these two measurements gives AS = (−3.8 ± 5.0stat ± 2.6syst) × 10−3 and, together with the asymmetry of the KL semileptonic decay, provides significant tests of the CPT symmetry. The obtained results are in agreement with CPT invariance. © 2018, The Author(s)
Combination of KLOE σ (e + e − → π+π−) measurements and determination of aμπ+ π− in the energy range 0.10 < s < 0.95 GeV2
No full textThe three precision measurements of the cross section σ(e+e− → π+π−) using initial state radiation by the KLOE collaboration provide an important input for the prediction of the hadronic contribution to the anomalous magnetic moment of the muon. These measurements are correlated for both statistical and systematic uncertainties and, therefore, the simultaneous use of these measurements requires covariance matrices that fully describe the correlations. We present the construction of these covariance matrices and use them to determine a combined KLOE measurement for σ(e+e− → π+π−). We find, from this combination, a two-pion contribution to the muon magnetic anomaly in the energy range 0.10 < s < 0.95 GeV2 of aμπ+π−=(489.8±1.7stat±4.8sys)×10−10. Data vectors and covariance matrices are available at http://www.lnf.infn.it/kloe/ppg/ppg_2017/ppg_2017.html. © 2018, The Author(s)
Radiation performance of new semiconductor power devices for the LHC experiment upgrades
No full textGaN and SiC power devices were extensively tested under different types of radiation, in the framework of the APOLLO R&D collaboration, aiming to use these new technologies for designing power supplies for the future LHC experiments upgrades. SiC power MOSFETs were irradiated with -rays, neutrons, and heavy ions (Iodine, Bromine) at different energies (20MeV - 550MeV). They showed very good performances in terms of Total Ionizing Dose (TID) sensitivity, but exhibited a quite poor Safe Operating Area (SOA) with respect to Single Event Effects (SEEs). Enhancement-mode GaN transistors manufactured by EPC, with blocking voltage ranging from 40V to 200V, were irradiated with -rays, heavy ions (Iodine, Bromine), and low energy protons. They showed a very good SOA toward SEE. After the irradiation with 3-MeV protons at the highest fluence (4∙1014 p/cm2), the devices exhibited an increase of up to one order of magnitude in gate leakage, almost 1 V of threshold voltage reduction, degradation of the subthreshold slope, and drop in transconductance. The reduction in threshold is in contrast with the increase normally observed in GaN devices irradiated with protons, and is likely due to radiation effects in the layers introduced to engineer the positive threshold voltage. © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence
Photodetector R&D for the belle II upgraded forward electromagnetic calorimeter
No full textThe Belle II experiment will operate at the SuperKEKB e+e- collider, designed to reach a peak luminosity of 8×1035 cm-2s-1 at the Γ(4S) resonance. The high background environment of SuperKEKB poses serious challenges to the design of the Belle II detector. In particular, an upgrade of the forward Electromagnetic Calorimeter is foreseen: the new calorimeter will use pure CsI crystals, which have a faster scintillation light emission and lower light yield than the CsI(Tl) crystals presently used. An intense R&D program is ongoing to select the optimal photodetector to meet the stringent requirements set by the use of pure CsI in Belle II. A study of equivalent noise, resolution, radiation hardness and stability of low noise, high-gain avalanche photodiodes obtained by reading single pure CsI crystals is discussed. Our preliminary results indicate that a readout chain using these devices meets the requirements on electronic noise set by the Belle II simulation and could represent a cost-effective choice for the readout of pure CsI crystals in general. © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence
Study of the Dalitz decay φ→ηe+e- with the KLOE detector
No full textWe have studied the vector to pseudoscalar conversion decay φ→ηe+e-, with η→π0π0π0, with the KLOE detector at DAΦNE. The data set of 1.7 fb-1 of e+e- collisions at s~Mφ contains a clear conversion decay signal of ~31, 000 events from which we measured a value of BR(φ→ηe+e-)=(1.075±0.007±0.038)×10-4. The same sample is used to determine the transition form factor by a fit to the e+e- invariant mass spectrum, obtaining bφη=(1.28±0.10-0.08+0.09) GeV-2, that improves by a factor of five the precision of the previous measurement and is in good agreement with VMD expectations. © 2015 The Authors
A novel radioguided surgery technique exploiting β- decays
No full textThe background induced by the high penetration power of the γ radiation is the main limiting factor of the current radio-guided surgery (RGS). To partially mitigate it, a RGS with β+ -emitting radio-tracers has been suggested in literature. Here we propose the use of β- -emitting radio-tracers and β- probes and discuss the advantage of this method with respect to the previously explored ones: the electron low penetration power allows for simple and versatile probes and could extend RGS to tumours for which background originating from nearby healthy tissue makes γ probes less effective. We developed a β- probe prototype and studied its performances on phantoms. By means of a detailed simulation we have also extrapolated the results to estimate the performances in a realistic case of meningioma, pathology which is going to be our first in-vivo test case. A good sensitivity to residuals down to 0.1 ml can be reached within 1 s with an administered activity smaller than those for PET-scans thus making the radiation exposure to medical personnel negligible
The PADME experiment at INFN LNF
No full textAt the end of 2015, INFN formally approved a new experiment, PADME, to search for invisible decays of the A' dark photon at the DAFNE Linac in Frascati. The experiment is designed to detect the A' produced in positron-on-fixed target annihilation, by measuring the final state missing mass. The collaboration aims to complete the design and construction of the experiment by the end of 2017 and to collect ∼1013 positrons on target by the end of 2018, thus reaching a sensitivity on the coupling constant of ∼103 and on the dark photon mass up to ∼ 23.7 MeV/c2 © Published under licence by IOP Publishing Ltd
Search for light vector boson production in e+e-→μ+μ-γ interactions with the KLOE experiment
No full textWe have searched for a light vector boson U, the possible carrier of a "dark force", with the KLOE detector at the DAΦNE e+e- collider, motivated by astrophysical evidence for the presence of dark matter in the Universe. Using e+e- collisions collected with an integrated luminosity of 239.3 pb-1, we look for a dimuon mass peak in the reaction e+e-→μ+μ-γ, corresponding to the decay U→μ+μ-. We find no evidence for a U vector boson signal. We set a 90% CL upper limit for the mixing parameter squared between the photon and the U boson of 1.6×10-5 to 8.6×10-7 for the mass region 520<mU<980 MeV. © 2014 The Authors
Limit on the production of a new vector boson in e+e-→Uγ, U→π+π- with the KLOE experiment
No full textThe recent interest in a light gauge boson in the framework of an extra U(1) symmetry motivates searches in the mass range below 1 GeV. We present a search for such a particle, the dark photon, in e+e-→Uγ, U→π+π- based on 28 million e+e-→π+π-γ events collected at DAΦNE by the KLOE experiment. The π+ π- production by initial-state radiation compensates for a loss of sensitivity of previous KLOE U→e+e-, μ+μ- searches due to the small branching ratios in the ρ-ω resonance region. We found no evidence for a signal and set a limit at 90% CL on the mixing strength between the photon and the dark photon, ε2, in the U mass range between 527 and 987MeV. Above 700 MeV this new limit is more stringent than previous ones. © 2016 The Authors
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