[en] The existence of a light-dark-force mediator has been tested with the KLOE detector at DAΦNE. This particle, called U, is searched for using the decay chain φ → ηU, with the final state η → π⁺π⁻ π⁰, U → e⁺e⁻ . No evidence is found in 1.5 fb⁻¹ of data. An upper limit on the existence of the U has been set, in the mass range 50 < M_U < 420 MeV. We are studying other η dominant decay channels as the 2γ and the 3π⁰. The combined fit will extend the upper limit on the overall mass range.

[en] In this paper, we report the measurement of the neutron radiation hardness of custom Silicon Photomultipliers arrays (SiPMs) manufactured by three companies: Hamamatsu (Japan), AdvanSiD (Italy) and SensL (Ireland). These custom SiPMs consist of a 2×3 array of 6×6 mm² monolithic cells with pixel sizes of respectively 50 μm (Hamamatsu and SensL) and 30 μm (AdvanSiD). A sample from each vendor has been exposed to neutrons generated by the Elbe Positron Source facility (Dresden), up to a total fluence of ∼ 8.5 × 10¹¹ n_1 MeV/cm². Test results show that the dark current increases almost linearly with the neutron fluence. The room temperature annealing was quantified by measuring the dark current two months after the irradiation test. The dependence of the dark current on the device temperature and on the applied bias have been also evaluated.

[en] The angular coverage extension of the KLOE-2 electromagnetic calorimeter, from a polar angle of 20⁰ down to 10⁰, will increase the multiphoton detection capability of the experiment enhancing the search reach for rare kaon, η and η' prompt decay channels. The basic layout of the calorimeter extension consists of two small barrels of LYSO crystals readout with APD photosensors aiming to achieve a timing resolution between 300 and 500 ps for 20 MeV photons. The first test of a (5.5x6x13) cm³ prototype for such a detector wa s carried out at the Beam Test Facility of Laboratori Nazionali di Frascati of INFN. We present here the results ofthis test.

[en] The upgrade of the DAΦNE machine layout requires a modification of the size and position of the inner focusing quadrupoles of KLOE² thus asking for the realization of two new calorimeters covering the quadrupoles area. To improve the reconstruction of K_L→2π⁰ events with photons hitting the quadrupoles, a tile calorimeter, QCALT, with high efficiency to low energy photons (20-300 MeV), time resolution of less than 1 ns and space resolution of few cm, is needed. We propose a tile calorimeter with a high granularity readout corresponding to about 2500 silicon photomultipliers (SiPM) of 1x1mm² area. Moreover, the low polar angle regions need the realization of a dense crystal calorimeter with very high time resolution performances to extend the acceptance for multiphotons events. Best candidates for this calorimeter are LYSO crystals with APD readout or PbWO₄ crystals with large area SIPM readout.

[en] The KLOE-2 detector has been successfully rolled in inside the new interaction region of the DAΦNE machine, which is still in its commissioning phase. Construction of detector upgrades is in progress to provide larger acceptance both for charged particles and photons. The CCALT calorimeters will be placed in front of the inner quadrupoles, inside the apparatus, thus increasing the acceptance for prompt decay channels. They consist of two barrels of LYSO crystals, read-out with large area SiPM. This choice provides high efficiency for low energy photons and good timing performances, needed to reject machine background events. Tests of a calorimeter prototype were carried out both with electron and photon beams, showing high light yield and good timing capabilities. The construction of the CCALT detector is in progress and will be completed in few months, in time for installing it over the new interaction region

[en] Understanding the energy resolution terms for LYSO based calorimeters with APD readout at low energy (< 500 MeV) is relevant both for the completion of the KLOE-2 experiment, at DAΦNE, and for the design of the Mu2e calorimeter. In this work, we present a dedicated comparison between experimental data, taken in 2011 at the MAMI tagged photon beam facility with a crystal matrix prototype, and a full Geant-4 simulation of this detector. The crystal prototype matrix consisted of 9 2×2 × 15 cm³ LYSO crystals read-out by 10×10 mm² Hamamatsu avalanche photodiodes (APD) surrounded by 8 PbWO₄ crystals read-out by Bialkali photomultipliers for outer leakage recovery granting a total transverse coverage of 3 Rm. An energy resolution of ∼5.4% at 100 MeV has been achieved. A fit to the energy dependence of the resolution provides the following parametrization: σ_E/E = 2.1%/E^1/4 ⊕ 3.6%, where the sum is in quadrature. The noise term is completely negligible as expected by the reduced level of the electronic noise achieved. The constant term is still leakage dominated.

[en] The upgrade of the DAΦNE machine layout requires a modification of the size and position of the inner focusing quadrupoles of KLOE-2 thus asking for the realization of two new calorimeters covering the quadrupoles area. To improve the reconstruction of K_L→2π⁰ events with photons hitting the quadrupoles a calorimeter with high efficiency to low energy photons (20-300 MeV), time resolution of less than 1 ns and space resolution of few cm, is needed. To match these requirements, we are designing a tile calorimeter, QCALT, where each single tile is readout by SiPM for a total granularity of 2400 channels. We show first tests of the different calorimeter components.

[en] The Mu2e calorimeter is composed of 1400 un-doped CsI crystals, coupled to large area UV extended Silicon Photomultipliers (SiPMs), arranged in two annular disks. This calorimeter has to provide precise information on energy, timing and position resolutions. It should also be fast enough to handle the high rate background and it must operate and survive in the high radiation environment. Simulation studies estimated that, in the highest irradiated regions, each photo-sensor will absorb a dose of 20 krad and will be exposed to a neutron fluency of 5.5×10¹¹n1 MeV/cm² in three years of running, with a safety factor of 3 included. At the end of 2015, we have concluded an irradiation campaign at the Frascati Neutron Generator (FNG, Frascati, Italy) measuring the response of two different 16 array models from Hamamatsu, which differ for the protection windows and a SiPM from FBK. In 2016, we have carried out two additional irradiation campaigns with neutrons and photons at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR, Dresden, Germany) and at the Calliope gamma irradiation facility at ENEA-Casaccia, respectively. A negligible increment of the leakage current and no gain change have been observed with the dose irradiation. On the other hand, at the end of the neutron irradiation, the gain does not show large changes whilst the leakage current increases by around a factor of 2000. In these conditions, the too high leakage current makes problematic to bias the SiPMs, thus requiring to cool them down to a running temperature of ∼0^oC.

[en] The angular coverage extension of the KLOE-2 electromagnetic calorimeter, from a polar angle of 20⁰ down to 8⁰, will increase the multiphoton detection capability of the experiment enhancing the search reach for rare kaon, η and η^' prompt decay channels. The basic layout of the calorimeter extension consists of two small barrels of LYSO crystals readout with APD photosensors aiming to achieve a timing resolution between 300 and 500 ps for 20 MeV photons. The first test of a (5.5x6x13)cm³ prototype for such a detector was carried out in April 2009 at the Beam Test Facility of Laboratori Nazionali di Frascati of INFN with an electron beam from 100 to 500 MeV. In the selected energy range, we measured a light yield of 500-800p.e./Mev, an energy resolution which can be parametrized as 0.05+0.01/(E/GeV)+0.015/√(E/GeV), a position resolution of 2.8 mm and a timing resolution of 200-300ps.

[en] To study an alternative to BaF_2, as the crystal choice for the Mu2e calorimeter, 13 pure CsI crystals from Opto Materials and ISMA producers have been characterized by determining their light yield (LY) and longitudinal response uniformity (LRU), when read with a UV extended PMT. The crystals show a LY of ~100 p.e./MeV (~150 p.e./MeV) when wrapped with Tyvek and coupled to the PMT without (with) optical grease. The LRU is well represented by a linear slope that is on average δ~ −0.6%/cm. The timing performances of the Opto Materials crystal, read with a UV extended MPPC, have been evaluated with minimum ionizing particles. A timing resolution of ~330 ps (~ 440 ps) is achieved when connecting the photosensor to the MPPC with (without) optical grease. The crystal radiation hardness to a ionization dose has also been studied for one pure CsI crystal from SICCAS. After exposing it to a dose of 900 Gy, a decrease of 33% in the LY is observed while the LRU remains unchanged.