Search

The High-Intensity Kaon Experiment (HIKE) is a proposed future kaon experiment designed for the CERN SPS accelerator. To cope with a planned increase of beam intensity by a factor of 4 with respect to the current NA62 experiment, the new Main Electromagnetic Calorimeter (MEC) has to provide a similar improvement in time resolution over the current Liquid Krypton calorimeter, down to ≈ 100 ps for a 40 GeV photon, while maintaining a comparable energy and spatial resolution. To achieve these goals, the planned detector consists of a shashlik calorimeter paired with high-resolution analog to digital converter for both energy deposit and arrival time estimates, operating at fast sample rates (∼ 1 GHz). This contribution describes a prototype of the readout system using commercial "off-the-shelf" boards. In particular, we focused on feature extraction and tested it using a pulse generator. We included a data readout logic based on the TCP/IP protocol allows for easy deployment in beam tests. [ABSTRACT FROM AUTHOR]

In the framework of the upgrade of the MEG experiment a new trigger system with demanding performances in terms of latency was designed. To achieve the goal of 512 ns latency the serial connections between trigger boards have been optimized so that they only rely on serial to parallel shift registers for the data flow, minimizing the amount of logic to be crossed by data. A dedicated Finite State Machine (FSM) was designed to select the sampling point of the serial stream with respect to an external precision clock used by both transmitter and receiver. As a proof of concept a 16 000 channel weighted waveform sum including pedestal suppression, was computed, resulting in 700 ns of latency. [ABSTRACT FROM AUTHOR]

We present two novel beam monitors designed for use in current PSI muon beams and upgradable for the High Intensity Muon Beam (HIMB) project beamlines: the scintillating fibre (SciFi) detector, a grid of scintillating fibres coupled to SiPMs, and the MatriX detector, a matrix of plastic scintillators coupled to silicon photomultipliers (SiPMs), both detectors having particle ID capability. The advantage of these highly segmented detectors is the capability to withstand the high beam rate and to perform total beam rate measurements. Furthermore, the use of the SiPM as a photosensor enables operation of these detectors in high magnetic field environments (up to 1. 25 T). Both detectors have been tested in the beam at PSI and with continuous beam rates up to 1 0 8 μ + /s. The performance of these detectors as measured on the beamlines are presented. [ABSTRACT FROM AUTHOR]

We present the ongoing development of an algorithm for the software alignment of the MEG II drift chamber based on the MillePede global approach. This method uses cosmic rays data collected during the 2022 data taking period to perform wire-by-wire alignment. We discuss first results obtained on data. [ABSTRACT FROM AUTHOR]

The MEG II experiment aims to improve the sensitivity to μ + → e + γ down to 6 × 1 0 − 14 , surpassing the 4. 2 × 1 0 − 13 UL by MEG. To achieve this sensitivity the detector performances need to be assessed and monitored via dedicated calibrations. To calibrate the Liquid Xenon Calorimeter near the signal energy (52.8 MeV), photons are produced through the Charge EXchange (CEX) process π − p → n π 0 (→ γ γ). Here we present the liquid Hydrogen target used for the CEX run 2021, during the first MEG II physics run. [ABSTRACT FROM AUTHOR]

Two very promising materials as the BrilLanCe (Cerium doped Lanthanum Bromide, LaBr 3 (Ce) and the LYSO (Lutetium Yttrium OxyorthoSilicate, Lu2(1−x) Y2x SiO5 (Ce)) coupled to Silicon photomultipliers (MPPC/SiPM) could represent an appealing option for the future calorimetry. The response of both LaBr 3 (Ce) and LYSO detectors having MPPC as photosensors have been studied via detailed Monte Carlo (MC) simulations. The impinging gammas are in the range of 50–100 MeV. The MC simulations are based on GEANT4, including the full electronic chain up to the waveform digitizer and finally the reconstruction algorithms. The results have been obtained are very promising. For a detector based on a (radius R = 4.45 cm, length L = 20.3 cm) LaBr 3 (Ce) crystal an energy resolution of σ E / E [ % ] = 2. 3 (1) and a timing resolution of σ t [ps] = 35(1) have been predicted. The energy resolution can be further improved by using larger crystals (either R = 6.35 cm or R = 7.6 cm, L = 20.3 cm) approaching respectively a σ E / E [ % ] = 1. 20 (3) or a σ E / E [ % ] = 0. 91 (1). Detector based on LYSO crystal of similar size performs even better, thanks to the shorter LYSO Moliere radius compared to the LaBr 3 (Ce) one. For a detector based on a (R = 3.5 cm, L = 16 cm) LYSO crystal an energy resolution of σ E / E [ % ] = 1. 7 (1) % can be obtained, and that can be further improved using bigger crystals (R = 6.5 cm, L = 25 cm, σ E / E [ % ] = 0. 74 (1) %. Energy resolution approaching σ E / E [ % ] = 0. 3 (1) % can be addressed for both crystals with ultimate sizes (R = 20–23 cm, L = 17–32 cm), complemented by timing and position resolutions in the range of O (30) ps and O (a few mm) respectively. Such results put these future high energy calorimeters at the detector forefront at intensity frontiers. [ABSTRACT FROM AUTHOR]

We describe and show results of a novel technique to measure with high precision the positions of photodetectors installed in the upgraded liquid xenon calorimeter of the MEG II experiment. The measurement was done by detecting the signal in individual photo-detectors as the front surface of the calorimeter was scanned in axial (Z) and azimuthal (ϕ) directions with a precisely controlled, thin, collimated beam of X-rays obtained from a 57 Co X-ray source. The measurements were made when the calorimeter was cold and operational, under which conditions they could not otherwise be made. This technique is used to check for changes in the photodetector positions due to the effects of cooling and thermal cycling of the support structure and to provide a reference between the positions of the operational photodetectors and alignment markers on the cryostat exterior. The use of an essentially monochromatic X-ray source allowed ancillary measurements of photodetector properties, including pulse shape, relative gain, and variation in response over the photodetector surface. Measurement uncertainties below 0.6 mm in Z and 0.7 mrad in ϕ have been achieved, well within the requirements for the MEG II performance. [ABSTRACT FROM AUTHOR]

The Light-only Liquid Xenon (LoLX) experiment is designed to study the properties of light emission and transport in liquid xenon (LXe) using silicon photomultipliers (SiPMs). In addition, we also plan to perform long-term stability studies of the SiPMs in LXe. Another important goal of the LoLX experiment is to characterize and utilize the differences in spectrum and timing of Cherenkov and scintillation light production to develop a background discriminator for low-background LXe experiments such as, neutrino-less double beta decay searches. In this paper we present the project status and perspectives. [ABSTRACT FROM AUTHOR]

The physics programme of the MEG II experiment can be extended with the search for new invisible particles produced in rare muon decays. The hunt for such elusive signals requires accurate simulations to characterise the detector response and estimate the experimental sensitivity. This work presents an improved simulation of muon decay in MEG II, based on McMule and Geant4. [ABSTRACT FROM AUTHOR]

The MEG experiment at the Paul Scherrer Institut (PSI) represents the state of the art in the search for the charged Lepton Flavor Violating μ + → e + γ decay, setting the most stringent upper limit on the BR (μ + → e + γ) ≤ 4. 2 × 1 0 − 13 (90% C.L.). An upgrade of MEG, MEG II, was designed, commissioned and recently started the physics data taking. Its goal is to reach a sensitivity level of 6 × 1 0 − 14 . In order to reconstruct the positron momentum vector a Cylindrical Drift CHamber (CDCH) with unprecedented peculiarities was built, featuring angular and momentum resolutions at the 6.5 mrad and 100 keV/c level. The CDCH is a 2-meter long, 60 cm in diameter, low-mass, single volume detector with high granularity: 9 layers of 192 drift cells, few mm wide, defined by ∼ 12000 wires in a stereo configuration for longitudinal hit localization. The filling gas mixture is Helium:Isobutane 90:10. The total radiation length is 1. 5 × 1 0 − 3 X 0 , thus minimizing the Multiple Coulomb Scattering and allowing for a single-hit resolution < 120 μ m. After the assembly at INFN Pisa, the CDCH was transported to PSI and integrated into the MEG II experimental apparatus since 2018. The commissioning phase lasted for the past three years until the operational stability was reached in 2020. The analysis software is continuously developing and the tuning of the reconstruction algorithms is one of the main activities. The latest updates on the positron momentum vector resolutions and tracking efficiency are presented. [ABSTRACT FROM AUTHOR]

The MEG II experiment is designed to improve by an order of magnitude the sensitivity of 4. 2 × 1 0 − 13 reached by MEG on the search for μ + → e + γ decay. A pixelated Timing Counter (pTC) has been developed to improve the time resolution by measuring the positron time information independently with several counters. We constructed and installed the pTC and performed commissioning runs at the π E5 beam line at PSI. A resolution of 38.5 ps is obtained with commissioning run data. [ABSTRACT FROM AUTHOR]

FOOT is a fixed target nuclear physics experiment in which O, C and He beams are shot on H enriched targets to study the projectile fragmentations; the measured cross sections will be used in medical physics and radioprotection in space applications. Beam fragmentation happens only on ≈ 10% of the cases so it is convenient to develop a sophisticated trigger procedure to veto most of non-fragmented primaries passing through the detector. In this paper we present the developed trigger algorithm operated on a WaveDAQ TDAQ system which is used also as DAQ for three of the FOOT detectors. [ABSTRACT FROM AUTHOR]

The MEG II experiment was designed to improve by an order of magnitude the sensitivity of 4. 2 × 1 0 − 13 reached by MEG on the branching ratio of the μ + → e + γ decay. The resolution of the positron timing is improved by using a segmented pixelated Timing Counter (pTC) where each counter is read independently. The pTC was commissioned in several engineering runs as well as in the first year of physics run (2021) at the π E5 beam line at PSI. Degradation of time resolution performance is observed and a program of partial upgrading the pTC is ongoing. [ABSTRACT FROM AUTHOR]

In the MEG II detector, the measurement of the momentum of the charged particle is performed by a high transparency single volume, full stereo cylindrical Drift Chamber (CDCH). It is composed by 9 concentric layers, each consisting of 192 drift cells. The single drift cell is approximately squared, with a 20 μ m gold plate tungsten sense wire surrounded by 40 μ m/50 μ m silver plated aluminum field wires in a ratio of 5:1. During the construction of the first CDCH, we observed the breaking of about hundred cathode wires: 97 of these were 40 μ m aluminum wires, while 10 were 50 μ m wires. Since the number of broken cathodes is less than 1% of the total, one can expect the influence on the track reconstruction efficiency to be not so dramatic. We verified by means of simulations that the loss of one cathode does not change the cell electric field appreciably. Here we present the results of the analysis of the effects of mechanical stress and chemical corrosion observed on these broken wires. Finally, we show the studies carried out on new wires to overcome the weaknesses found and the process that will be used for the construction of the new drift chamber (CDCH2). It will be built with the same modular technique, as for the previous one, the use of the wiring robot will be optimized to improve some weaker step in the procedure, new wires will be adopted with a 25% thicker diameter, which has very little effects on the resolution and efficiency of the detector. Furthermore these wires are made with a manufacturing process different from that used previously. • Brief description of the MEG CDCH. • Analysis and study of the problems on the wires used in the MEG CDCH. • Analysis and study of the problems on the wires used in the MEG CDCH. • The construction of the new MEG CDCH. • Chemical and SEM analysis of the wires used in the CDCH. [ABSTRACT FROM AUTHOR]

The MEG II experiment is searching for new physics beyond the SM (e.g. SUSY-GUT, SUSY-seesaw) through the lepton flavor violating μ + → e + γ decay with ten times better sensitivity than the MEG experiment. The MEG collaboration published the result of B (μ + → e + γ) < 4. 2 × 1 0 − 13 at 90% C.L. in 2016, which was thirty times better result than the previous limit. As the sensitivity of the MEG experiment was already limited by the accidental background, the MEG detector had to be upgraded to reach one order of magnitude better sensitivity. The MEG experiment utilized 846 2 inch PMTs to detect scintillation light in a 900 l liquid xenon γ calorimeter. In the MEG II experiment, 216 2 inch PMTs on the γ incident face were replaced with 4092 MPPCs (SiPMs produced by Hamamatsu) to improve the energy and position resolutions. We started the detector commissioning with the full electronics readout channels for the first time in 2021, and soon after, we started the physics data taking. Here the LXe detector status including initial photon sensor calibration and performance will be summarized together with the expected detector performance. The PDE decrease of the SiPM observed in the high rate muon beam environment and our possible remedy will also be discussed. [ABSTRACT FROM AUTHOR]

In this contribution we discuss the calibration and performance of the TOF-Wall detector of the Fragmentation-Of-Target (FOOT) experiment. A thin carbon target was irradiated with carbon ions of several energies ranging from 150 to 400 MeV/u. The charge spectra of the produced fragments were used to calibrate the energy response. The energy resolution for a single bar was about 6%. The time resolution between the two layers ranged from 42 (150 MeV/u) to 62 ps (400 MeV/u). [ABSTRACT FROM AUTHOR]

The ultra-low mass cylindrical drift chamber designed for the MEG II experiment is a challenging apparatus made of 1728 ϕ = 20 μ m gold plated tungsten sense wires, 7680 ϕ = 40 μ m and 2496 ϕ = 50 μ m silver plated aluminium field wires. Because of electrostatic stability requirements all the wires have to be stretched at mechanical tensions of ∼ 25 , ∼ 19 and ∼ 29 g respectively which must be controlled at a level better than 0. 5 g. This chamber is presently in acquisition, but during its construction ∼ 100 field wires broke, because of chemical corrosion induced by the atmospheric humidity. On the basis of the experience gained with this chamber we decided to build a new one, equipped with a different type of wires less sensitive to corrosion. The choice of the new wire required a deep inspection of its characteristics and one of the main tools for doing this is a system for measuring the wire tension by means of the resonant frequency technique, which is described in this paper. The system forces the wires to oscillate by applying a sinusoidal signal at a known frequency, and then measures the variation of the capacitance between a wire and a common ground plane as a function of the external signal frequency. We present the details of the measuring system and the results obtained by scanning the mechanical tensions of two samples of MEG II cylindrical drift chamber wires and discuss the possible improvements of the experimental apparatus and of the measuring technique. [ABSTRACT FROM AUTHOR]

In the quest for Lepton Flavor Violation (LFV) the MEG experiment at the Paul Scherrer Institut (PSI) represents the state of the art in the search for the charged LFV decay μ + → e + γ , setting the most stringent upper limit on the BR (μ + → e + γ) ≤ 4. 2 × 1 0 − 13 (90% C.L.). An upgrade of MEG, MEG II, was designed and it recently started the physics data taking, with the aim to reach a sensitivity level of 6 × 1 0 − 14 . The Cylindrical Drift CHamber (CDCH) is a key detector in order to improve the e + angular and momentum resolutions at the 6.5 mrad and 100 keV/c level. The CDCH is a low-mass single volume detector with high granularity: 9 layers of 192 drift cells each, few mm wide, defined by 12000 wires in a stereo configuration for longitudinal hit localization. After the assembly, the CDCH was transported to PSI for the commissioning phase and it has been integrated into the MEG II experimental apparatus since 2018. The operational stability was reached in 2020 and the complete readout electronics was tested for the first time in 2021. A preliminary analysis of 2020–2021 data is presented. [ABSTRACT FROM AUTHOR]

This article presents the MEG II Cylindrical Drift CHamber (CDCH), a key detector for the phase 2 of MEG, which aims at reaching a sensitivity level of the order of 6 × 1 0 − 14 for the charged Lepton Flavour Violating μ + → e + γ decay (Calibbi and Signorelli, 2018; Cei and Nicolò, 2014). CDCH is designed to overcome the limitations of the MEG e + tracker (Baldini et al., 2013) and guarantee the proper operation at high rates with long-term detector stability. CDCH is a low-mass unique volume detector with high granularity: 9 layers of 192 drift cells, few mm wide, defined by ≈ 12000 wires in a stereo configuration for longitudinal hit localization. The total radiation length is 1. 5 × 1 0 − 3 X 0 , thus minimizing the Multiple Coulomb Scattering (MCS) contribution and allowing for a single-hit resolution of 110 μ m (Baldini et al., 2016) and a momentum resolution of 130 keV/c. CDCH integration into the MEG II experimental apparatus (Baldini et al., 2018) will start in this year. • The new Cylindrical Drift CHamber (CDCH) is a key detector for the phase 2 of MEG. • CDCH has a single cylindrical volume filled with a low-mass He:Isobutane gas mixture. • High granularity is ensured by 1728 drift cells (few mm wide) divided in 9 layers. • Material budget minimized to 1. 5 × 1 0 − 3 X 0 per track turn to reduce MCS. • CDCH is in the final mechanical and HV test phase before the shipping to PSI. [ABSTRACT FROM AUTHOR]

The MEG experiment, at the PSI, aims to search for the charged lepton flavor violating decay μ + → e + γ. MEG has established the world best upper limit for the branching ratio: BR (μ + → e + γ) < 4. 2 × 1 0 − 13 at 90% CL. An upgrade (MEG II) of the whole detector has been approved to obtain a substantial increase in sensitivity. The new positron tracker is a single volume, full stereo cylindrical Drift Chamber (CDCH), filled with a gas mixture of 85: 15 H e ∕ i − C 4 H 10. Due to their high wires density (12 wires/cm2) and the stringent requirements on spatial resolution, the use of the classical feed-through technique as wire anchoring system can hardly be implemented and therefore it is necessary to develop an automatic system (wiring robot) with a high-performing control. A wiring robot, designed and built at the INFN Lecce and University of Salento laboratories was used for the wiring phase of the MEG CDCH. The new CDCH is currently in the test phase at INFN Lecce and Pisa, and later it will be delivered to PSI for commissioning. [ABSTRACT FROM AUTHOR]

The FOOT experiment aims at identifying the fragments produced in the human body during hadrontherapy and at measuring their cross sections. The apparatus is composed of several detectors which allow a complete reconstruction of the tracks of the fragments. In particular, the Δ E-TOF detector measures the energy released in a thin plastic scintillator and the time of flight of the fragments. In this work, we report the energy and time resolution of a Δ E-TOF detector prototype with proton and carbon irradiations, and we compare the results with a Monte Carlo simulation of the optical transport in the detector. With carbon ions, we measured time resolutions of ∼ 50 ps and energy resolutions of ∼ 6%. The Monte Carlo simulation was able to model the dependence of the number of detected photons on the proton interaction position. [ABSTRACT FROM AUTHOR]

The WaveDAQ is a full custom, compact and highly integrated trigger and data acquisition system. Despite the decisive urge from the MEG II experiment at PSI aiming at a sensitivity of 6 × 1 0 − 14 on the μ → e γ decay, it is a general purpose device suited for small and medium-sized applications in the range from 16 to about 10 000 channels. It exploits the performance of the DRS4 waveform digitiser with a sampling speed programmable from 1 to 5 GSPS; each input channel can supply HV to arrays of SiPMs and provides a front-end amplification with gains chain in the range from 0.5 up to 100 and GHz bandwidth. Input signals are, in parallel to the DRS4, digitised at 80 MSPS and used in an FPGA-based trigger; fast discriminators associated to each input channel are also used for online reconstruction. This paper presents the WaveDAQ design principles and the results obtained by a demonstrator in the MEG II pre-engineering run in fall 2017 with a homogeneous LXe detector and a plastic scintillation detector both readout by SiPMs and in the tests associated to the Δ E-TOF prototype of the FOOT detector. [ABSTRACT FROM AUTHOR]

A positron timing counter (TC) with 30–40 ps time resolution for 50 MeV/c positrons required by the MEG II experiment has been developed. We employed a highly segmented design with 512 scintillator plates (120 × 40 × 5 mm3 and 120 × 50 × 5 mm3) read out by 6-SiPM-arrays at the both ends. Pile up is reduced by the segmented design and multi-counter measurement improves the overall timing resolution. All the single counters were assembled and their resolutions were measured to be below 100 ps in a pre-test with a 90 Sr source. The construction and installation were completed in 2017. An engineering run was performed at the end of 2017 at the π E5 muon beam line in PSI, which supplies the most intense muon beam (7 × 107 stops/s on a target) in the world. We successfully operated the full system of TC in the MEG II environment and achieved a time resolution below 40 ps with more than 6 counter hits. The overall resolution for the signal positrons is estimated to be 38.5 ps by weighting the obtained resolutions with the number of hits distribution of the signal positrons obtained by a Monte Carlo simulation. The time resolution of the TC is improved by a factor of 2 with respect to the MEG experiment. [ABSTRACT FROM AUTHOR]

FOOT (FragmentatiOn On Target) is an applied nuclear physics experiment aimed at measuring the production cross sections of fragments for energies, beams and targets relevant in particle therapy and radioprotection in space. The Δ E-TOF detector will measure the energy deposited by the fragments in a wall of plastic scintillators and the time of flight with respect to a start detector. These two quantities allow to determine the charge Z of the fragment. In this work, we summarize the charge identification procedure of a detector prototype with two scintillator modules. [ABSTRACT FROM AUTHOR]

The MEG experiment at the Paul Scherrer Institute searches for the charged Lepton Flavor Violating μ + → e + γ decay. MEG has already determined in a first data taking phase the world best upper limit on the branching ratio: BR (μ + → e + γ) < 4. 2 × 1 0 − 13 An upgrade of the whole detector has been approved to obtain a substantial increase in sensitivity. Currently MEG is in upgrade phases, this phase involves all the detectors. The new positron tracker is a high transparency single volume, fully stereo cylindrical Drift Chamber (CDCH), immersed in a non uniform longitudinal B-field, with length of 1. 93 m, internal radius of 17 cm and external radius of 30 cm. It is composed of 9 concentric layers, divided into 12 identical sector of 16 drift cells. The single drift cell is approximately square, with a 20 μ m gold plated W sense wire surrounded by 40 μ m silver plated Al field wires in a ratio of 5:1. The total number of wires amounts to 11904 for an equivalent radiation length per track turn of about 1.5x10−3 X 0 when the chamber is filled with a gas mixture of helium and iso-butane. Due to the high wire density (12 w i r e s ∕ cm 2 ), the use of the classical feed-through technique as wire anchoring system could hardly be implemented and therefore it was necessary to develop new wiring strategies. The number of wires and the stringent requirements impose the use of an automatic system (wiring robot) to operate the wiring procedures. Several tests have been performed in different prototypes of the drift chamber, exposed to cosmic rays, test beams and radioactive sources, to fulfill the requirement on the spatial resolution to be less than 110 μ m. In this paper we describe the CDCH construction and the first tests during the 2018 Engineering Run. [ABSTRACT FROM AUTHOR]

Nuclear physics processes are an important source of uncertainty in dose calculations in particle therapy and radioprotection in space. Accurate cross section measurements are a crucial ingredient in improving the understanding of these processes. The FOOT (FragmentatiOn Of Target) experiment aims at measuring the production cross sections of fragments for energies, beams and targets that are relevant in particle therapy and radioprotection in space. An experimental apparatus composed of several sub-detectors will provide the mass, charge, velocity and energy of fragments produced in nuclear interactions in a thin target. A crucial component of the FOOT apparatus will be the Δ E-TOF detector, designed to identify the charge of the fragments using plastic scintillators to measure the energy deposited and the time of flight with respect to a start counter. In this work, we present a charge reconstruction procedure of produced fragments at particle therapy energies. We validate it by measuring the charges of various fragments at an angle of 3.2°and 8.3°with respect the beam-axis, using a small-scale detector and clinical beams of carbon ions at the CNAO oncology center. Experimental results agree well with FLUKA Monte Carlo simulations. [ABSTRACT FROM AUTHOR]

We have developed a new laser-based time calibration system for highly segmented scintillator counters like the MEG II pixelated Timing Counter (pTC), consisting of 512 centimetre-scale scintillator counters read out by silicon photomultipliers (SiPMs). It is difficult to apply previous laser-based calibration methods for conventional metre-scale Time-Of-Flight detectors to the MEG II pTC from the implementation and the accuracy points of view. This paper presents a new laser-based time calibration system which can overcome such difficulties. A laser pulse is split into each scintillator counter via several optical components so that we can directly measure the time offset of each counter relative to the laser-emitted time. We carefully tested all the components and procedures prior to the actual operation. The laser system was installed into the pTC and thoroughly tested under the real experimental condition. The system showed good stability and being sensitive to any change of timing larger than ∼ 10 ps. Moreover, it showed an uncertainty of 48 ps in the determination of the time offsets, which meets our requirements. The new method provides an example of the implementation of a precise timing alignment for the new type of detectors enabled by the advance of SiPM technology. [ABSTRACT FROM AUTHOR]