First information on the time-like electromagnetic structure of baryons in the second resonance region has been obtained from measurements of dielectron (e+ e-) invariant-mass and angular distributions in the quasi-free reaction $\pi-$ p $\rightarrow$ n e+ e- at $\sqrt{s_{\pi p}}$ = 1.49 GeV with the High Acceptance Di-Electron Spectrometer (HADES) at GSI using the pion beam impinging on a CH$_2$ target. We find a total cross section $\sigma$ = 2.97 $\pm$ 0.07data $\pm$ 0.21acc $\pm$ 0.31Zeff $\mu$b. In complement to the analysis of the inclusive e+ e- channel, this data set provides a crucial test of the description of baryon time-like transitions. Approaches based on a Vector Meson Dominance amplitude containing direct photon and vector meson ($\rho$) couplings to the baryon provide a satisfactory agreement with the data. A good description is also obtained by electromagnetic time-like baryon transition form factors in a covariant spectator-quark model, pointing to the dominance of meson-cloud effects. The dielectron angular distributions exhibit the contributions of virtual photons ($\gamma^*$) with longitudinal polarization, in contrast to real photons. The virtual photon angular dependence supports the dominance of J=3/2, I=1/2 contributions observed in both the $\gamma^*$n and the $\pi \pi$n channels.

Resistive Plate Chambers (RPCs) are gaseous detectors widely used in High Energy Physics due to their excellent timing performance, high efficiency, scalability, and affordability. However, their operation relies on gas mixtures based on hydrofluorocarbons (HFCs), whose high Global Warming Potential and progressive phase-out under current environmental regulations pose significant challenges for the long-term sustainability of RPC technology. In this work, we investigate a conceptually different approach, as an alternative to eco gas-mixture substitution strategies, based on sealed RPCs, in which the detector is filled with standard gas during assembly and subsequently hermetically sealed, allowing operation without any external gas supply. This approach drastically reduces gas consumption, eliminates the need for complex gas systems, and offers a potential solution compatible with both environmental constraints and high-performance operation. Two sealed RPC configurations, with active areas of approximately 0.1 m2 and 1 m2, have been developed and characterized using atmospheric cosmic muons. The 0.1 m2 module demonstrates stable operation over an extended period of nearly two continuous years, with an average efficiency of about 98% and low streamer probability. The 1 m2 prototype exhibits a comparable initial response, although limitations related to mechanical stability are observed. These results demonstrate the feasibility of sealed RPC technology for trigger applications and highlight its potential as a robust, cost-effective, and environmentally sustainable alternative for future gaseous detector systems.

Inclusive e$^+$e$^-$ production has been studied with HADES in $\pi^-$ + p, $\pi^-$ + C and $\pi^- + \mathrm{CH}_2$ reactions, using the GSI pion beam at $\sqrt{s_{\pi p}}$ = 1.49 GeV. Invariant mass and transverse momentum distributions have been measured and reveal contributions from Dalitz decays of $\pi^0$, $\eta$ mesons and baryon resonances. The transverse momentum distributions are very sensitive to the underlying kinematics of the various processes. The baryon contribution exhibits a deviation up to a factor seven from the QED reference expected for the dielectron decay of a hypothetical point-like baryon with the production cross section constrained from the inverse $\gamma$ n$\rightarrow \pi^-$ p reaction. The enhancement is attributed to a strong four-momentum squared dependence of the time-like electromagnetic transition form factors as suggested by Vector Meson Dominance (VMD). Two versions of the VMD, that differ in the photon-baryon coupling, have been applied in simulations and compared to data. VMD1 (or two-component VMD) assumes a coupling via the $\rho$ meson and a direct coupling of the photon, while in VMD2 (or strict VMD) the coupling is only mediated via the $\rho$ meson. The VMD2 model, frequently used in transport calculations for dilepton decays, is found to overestimate the measured dielectron yields, while a good description of the data can be obtained with the VMD1 model assuming no phase difference between the two amplitudes. Similar descriptions have also been obtained using a time-like baryon transition form factor model where the pion cloud plays the major role.

A new readout technique decoupling the number of FEE channels from the detector area was tested with large-area Resistive Plate Chambers (RPCs) featuring a sensitive area of 130 x 90 cm2. Despite using only 48 electronic channels to read out 888 pick-up strips, a 2D submillimetric spatial precision was achieved during a long run with cosmic rays, along with a time precision of 89 ps (sigma). FLUKA Monte Carlo simulations were also performed to evaluate the use of RPCs with high spatial and temporal precision for scanning large volumes employing the Muon Scattering Tomography technique.

Objective: To explore readout architectures for the simultaneous high-resolution timing and bidimensional tracking of charged particles with Resistive Plate Chambers (TOF-tracker) and for the accurate detection of gamma rays for Positron Emission Tomography (PET).Materials and methods: Resistive plate chambers and their corresponding readout systems under evaluation were exposed to cosmic rays and β+ sources.Results: Over an active area of 625 cm2, we obtained a time resolution of 61 ps ơ and bidimensional position resolution below 150 μm ơ for the tracking and timing of charged particles from cosmic rays. The intrinsic precision for localising a small β+ source via the detection of its annihilation radiation was determined to be 0.49 mm FWHM.Conclusions: The proposed device exhibits excellent timing and position resolution for the tracking and timing of charged particles, with potential applications in nuclear and high-energy particle physics, as well as gamma imaging with applications in PET.

SND@LHC, Scattering and Neutrino Detector at the LHC, is a compact experiment designed to perform measurements with neutrinos produced at the LHC in the unexplored pseudo-rapidity region of 7.2 < \eta η < 8.4, complementary to all the other experiments at the LHC. The experiment was approved in March 2021. It was constructed in about one year and it is now taking data during the Run 3 of the LHC. In this paper we review the detector concept, the physics case and the status of the data taking.

The phase-out of hydro-fluorocarbons, owing to their high Global Warming Power, affecting the main gas used in Resistive Plate Chambers (RPCs), tetrafluoroethane C_2H_2F_4, has increased operational difficulties on existing systems and imposes strong restrictions on its use in new systems. This has motivated a new line of R&D on sealed RPCs: RPCs that do not require a continuous gas flow for their operation and dispense the use of very complex and expensive re-circulation and/or recycling gas systems. At the moment it is not clear whether this solution can cover all fields of application normally allocated to RPCs, but it seems that it could be considered as a valid option for low particle flux triggering/tracking of particles, e.g. in cosmic ray or rare event experiments. In this work, we demonstrate the feasibility of a small telescope for atmospheric muon tracking consisting of four 300 x 300 mm^2 sealed RPCs with gas gap widths of 1 mm, 1.5 mm and 2 mm. The results suggest that it is possible to operate this type of detectors for extended periods of time (more than five months) with its main characteristics, efficiency, average charge and streamer probability, without apparent degradation and similar to a RPC operated in continuous gas flow.

Hadron production ( π ^± , proton, Λ , K_S^0 , K^± ) in π ^- + C and π ^- + W collisions is investigated at an incident pion beam momentum of 1.7 GeV/c . This comprehensive set of data measured with HADES at SIS18/GSI significantly extends the existing world data on hadron production in pion induced reactions and provides a new reference for models that are commonly used for the interpretation of heavy-ion collisions. The measured inclusive differential production cross-sections are compared with state-of-the-art transport model (GiBUU, SMASH) calculations. The (semi-) exclusive channel π ^- + A →Λ + K_S^0 +X , in which the kinematics of the strange hadrons are correlated, is also investigated and compared to a model calculation. Agreement and remaining tensions between data and the current version of the considered transport models are discussed.

The SHiP-charm project was proposed to measure the associated charm production induced by 400 GeV/c protons in a thick target, including the contribution from cascade production. An optimisation run was performed in July 2018 at CERN SPS using a hybrid setup. The high resolution of nuclear emulsions acting as vertex detector was complemented by electronic detectors for kinematic measurements and muon identification. Here we present first results on the analysis of nuclear emulsions exposed in the 2018 run, which prove the capability of reconstructing proton interaction vertices in a harsh environment, where the signal is largely dominated by secondary particles produced in hadronic and electromagnetic showers within the lead target.

Recently we have proposed a new concept of a thermal neutron detector based on resistive plate chambers and 10B4C solid neutron converters, enabling to readout with high resolution in both the 3D position of neutron capture and the neutron time of flight (ToF). In this paper, we report the results of the first beam tests conducted with a new neutron RPC detection module, coupled to the position readout units of a new design. The main focus is on the measurements of the neutron ToF and identification of the converter layer where the neutron is captured, giving the position along the beam direction.

The production of Σ ^0 hyperons in proton proton collisions at a beam kinetic energy of 3.5 GeV impinging on a liquid hydrogen target was investigated using data collected with the HADES setup. The total production cross section is found to be σ (pK^+Σ ^0) = 17.7 ± 1.7 (stat) ± 1.6 (syst) µb. Differential cross section distributions of the exclusive channel pp → pK^+Σ ^0 were analyzed in the center-of-mass, Gottfried–Jackson and helicity reference frames for the first time at the excess energy of 556 MeV. The data support the interplay between pion and kaon exchange mechanisms and clearly demonstrate the contribution of interfering nucleon resonances decaying to K^+Σ ^0 . The Bonn–Gatchina partial wave analysis was employed to analyse the data. Due to the limited statistics, it was not possible to obtain an unambiguous determination of the relative contribution of intermediate nucleon resonances to the final state. However nucleon resonances with masses around 1.710 GeV/c^2 ( N^*(1710) ) and 1.900 GeV/c^2 ( N^*(1900) or Δ ^*(1900) ) are preferred by the fit.

A new readout technique was developed with the primary aim of keeping the number of channels in the front-end electronics as low as possible when scaling up the sensitive area of a Resistive Plate Chamber (RPC). The readout method here presented significantly reduces the dependence between the detector area and the number of electronic channels, without substantial reduction of its performance: a 30 x 30 cm(2) double stack multi-gap timing RPC was operated during weeks with cosmic rays, achieving a 2D spatial resolution well below 1 mm and time resolution lower than 100 ps, while its efficiency was kept above 98%.

A muon telescope equipped with four multi-gap Resistive Plate Chambers of 2 m2 per plane was tested with the muon scattering tomography technique. The telescope was operated during several hours with high atomic number materials located at its center with two detector planes on each side. With an intrinsic efficiency above 98%, spatial resolution around 1 cm and detector planes spaced by 45 cm, it was possible to identify the presence of a 5 cm thick tungsten block in 10 min of acquisition. The results obtained after five hours of acquisition are also presented in this communication.

High-precision measurements of flow coefficients v_n ( n = 1 - 4 ) for protons, deuterons and tritons relative to the first-order spectator plane have been performed in Au+Au collisions at √(s__NN)= 2.4 GeV with the High-Acceptance Di-Electron Spectrometer (HADES) at the SIS18/GSI. Flow coefficients are studied as a function of transverse momentum p_t and rapidity y_cm over a large region of phase-space and for several classes of collision centrality. A clear mass hierarchy, as expected by relativistic hydrodynamics, is found for the slope of v_1 , d v_1/d y^'|_y^' = 0 where y^' is the scaled rapidity, and for v_2 at mid-rapidity. Scaling with the number of nucleons is observed for the p_t dependence of v_2 and v_4 at mid-rapidity, which is indicative for nuclear coalescence as the main process responsible for light nuclei formation. v_2 is found to scale with the initial eccentricity ⟨ϵ _2⟩ , while v_4 scales with ⟨ϵ _2⟩ ^2 and ⟨ϵ _4⟩ . The multi-differential high-precision data on v_1 , v_2 , v_3 , and v_4 provides important constraints on the equation-of-state of compressed baryonic matter.

Large Resistive Plate Chamber systems have their roots in High Energy Physics experiments at the European Organization for Nuclear Research: ATLAS, CMS and ALICE, where hundreds of square meters of both trigger and timing RPCs have been deployed. These devices operate with complex gas systems, equipped with re-circulation and purification units, which require a fresh gas supply of the order of 6 cm$^{3}$/min/m$^{2}$, creating logistical, technical and financial problems. In this communication, we present a new concept in the construction of RPCs which allowed us to operate a detector at ultra-low gas flow regime. With this new approach, the glass stack is encapsulated in a tight plastic box made of polypropylene, which presents excellent water vapor blocking properties as well as a good protection against atmospheric gases.

An optimized design of a neutron detector based on timing RPCs (Resistive Plate Chambers) with boron-10 neutron converters is presented. The detector is composed of a stack of ten double gap RPCs with aluminium cathode plates coated on both sides with 10B4C. This design enables simultaneous determination with high accuracy of both the neutron time-of-flight (down to ns resolution) and the interaction position in 3D (down to 0.25 mm resolution across and-1 mm along the beam). It is shown that the detection efficiency can approach 60% for neutrons with lambda = 4.7 angstrom. A new geometry with less material budget is introduced for the signal pick-up strip arrays. The results of simulation-based optimization of the design are reported considering the trade-off between the detection efficiency, the count rate capability and the amount of elastic scattering on the detector components.

Over the last two decades, the possibility of using RPCs in outdoors systems has increased considerably. Our group has participated in this effort by installing several systems and continues to work on their optimization, while simultaneously studying and developing new approaches that can use RPCs in outdoor applications.In particular, four detectors were deployed in the field at the Pierre Auger Observatory in 2019 remained inactive, awaiting the commissioning of support systems. During the pandemic the detectors were left without gas flow for more than two years, but were recently reactivated with no major problems.The LouMu project combines particle physics and geophysics in order to map meter-scale geologic structures, using Muon Tomography. Transmission muography is sensitive to the total amount of matter crossed by the muons, allowing to separate targets of different densities. In this exploratory project, it serves to identify unconsolidated rock zones, like geological faults and ore masses around an old Pyrite mine, now converted into a science center. The general goal is to compare how effective is the muographic survey when compared with the more standard geophysical techniques. The development of the RPC system used and the data from the last two years will be presented.Finally, recent advances in a large area (1 m2) double gap-sealed RPC will be presented.

Muon tomography is one of several fields of applied physics that have witnessed the successful use of particle detection based on Resistive Plate Chambers (RPC). In this work, we report on an innovative project concerning transmission muography for geological characterization. For this purpose, a muon telescope built of four RPC planes was mounted on an adjustable structure and the telescope’s response to atmospheric muons was studied. Data acquisition campaigns took place at different locations for producing muographic images of the building of the Physics Department of the University of Coimbra, in Portugal. More recently, the detector was moved to an underground gallery of an old mine, where it is taking data that is being assessed in combination with the results from conventional geophysics techniques.