[en] Antihydrogen is at the forefront of antimatter research at the CERN Antiproton Decelerator. Experiments aiming to test the fundamental CPT symmetry and antigravity effects require the efficient detection of antihydrogen annihilation events, which is performed using highly granular tracking detectors installed around an antimatter trap. Improving the efficiency of the antihydrogen annihilation detection plays a central role in the final sensitivity of the experiments. We propose deep learning as a novel technique to analyze antihydrogen annihilation data, and compare its performance with a traditional track and vertex reconstruction method. We report that the deep learning approach yields significant improvement, tripling event coverage while simultaneously improving performance in terms of AUC by 5%. (paper)

[en] Voltages above a hundred kilo-volt will be required to generate the drift field of future very large liquid Argon Time Projection Chambers. One of the most delicate component is the feedthrough whose role is to safely deliver the very high voltage to the cathode through the thick insulating walls of the cryostat without compromising the purity of the argon inside. This requires a feedthrough that is typically meters long and carefully designed to be vacuum tight and have small heat input. Furthermore, all materials should be carefully chosen to allow operation in cryogenic conditions. In addition, electric fields in liquid argon should be kept below a threshold to reduce risks of discharges. The combination of all above requirements represents significant challenges from the design and manufacturing perspective. In this paper, we report on the successful operation of a feedthrough satisfying all the above requirements. The details of the feedthrough design and its manufacturing steps are provided. Very high voltages up to unprecedented voltages of −300 kV could be applied during long periods repeatedly. A source of instability was observed, which was specific to the setup configuration which was used for the test and not due to the feedthrough itself.

[en] X-ray images of the plasma were recorded at the ECR ion source using a pinhole and a high resolution CCD camera. Operating with short exposure times. any individual pixel could be used as a single photon detector with an energy resolution of about 180 eV. Images of selected plasma regions (extraction slit, magnet pole, magnet gap) gave a better understanding of the effect of important tuning parameters like bias disk voltage, gas mixing, microwave power, magnetic field strength etc. (K.A.)

[en] The problem of matching primary and secondary light signals, belonging to the same event, is presented in the context of dual-phase time projection chambers. In large scale detectors the secondary light emission could be delayed up to order of milliseconds, which, combined with high signal rates, could make the matching of the signals challenging. A possible approach is offered in the framework of the Stable Marriage and the College Admission problem, for both of which solutions are given by the Gale–Shapley algorithm.

[en] The 14.5 GHz ECR ion source of the ATOMKI is a stand-alone device producing highly charged ion beams for ion-surface experiments and a variety of low charged plasmas and beams for plasma physics studies and for practical applications. In the past two years we performed plasma diagnostics measurements using Langmuir-probes and X-ray camera. Langmuir-probe results allowed estimating the plasma potential close to the resonance zone. The studying of X-ray pictures of Xe-Ar plasmas helps understanding the gas-mixing phenomena. A mixture plasma of fullerene and ferrocene was generated and FeC60 hybrid molecules were detected in the extracted beam

[en] The ASACUSA antihydrogen setup at the CERN Antiproton Decelerator (AD) consists of an antihydrogen source (cusp magnet coupled to a positron source and an antiproton catching magnet) followed by a spectrometer beamline. After production in the cusp, the antihydrogen atoms decay while they escape the trap leading to changes in their effective magnetic moment which in turn affect their trajectories in the beamline. Those sequential decays in the presence of a varying magnetic field strength from their production point in the cusp to their detection at the end of the spectrometer line can in principle greatly affect the prospects for a precision measurement of the antihydrogen hyperfine splitting given the so-far relatively low number of available anti-atoms. The impact of the antihydrogen decay in this context has for the first time been simulated. The implementation of atomic radiative decay has been done in Geant4 to extend the particle tracking capabilities originally embedded in Geant4 to excited atoms, and to allow studies of the effect of dynamic atomic properties on trajectories. This new tool thus allows the study of particle–matter interaction via the Geant4 toolkit while properly taking into account the atomic nature of the object under study. The implementation as well as impacts on the experimental sensitivity for antihydrogen spectroscopy are discussed in this paper. (paper)

[en] The general distribution of the emitting highly charged ion cloud and its systematic dependence on various operating parameters were the focus of the experiments. The ion production and confinement provides insight into the operation of the ECR ion source and gives important information for our future spectroscopic plans. In addition to its source diagnostic value, the X-ray imaging and spectroscopy of highly charged ion plasmas can also be utilized for the laboratory investigation of plasmas of astrophysical and other interests. (R.P.)

[en] In this work, we report on the sensitivity potential of complementary muon-on-target experiments to new physics using a scalar boson benchmark model associated with charged lepton flavor violation. The NA64µ experiment at CERN uses a 160-GeV energy muon beam with an active target to search for excess events with missing energy and momentum as a probe of new physics. At the same time, the proton beam at Fermilab, which is used to produce the neutrino beam for the Deep Underground Neutrino Experiment (DUNE), will also produce a high-intensity muon beam dumped in an absorber. Combined with the liquid argon near detector, the system could be used to search for similar scalar boson particles with a lower-energy but higher-intensity beam. We find that both NA64µ and DUNE could cover new, unexplored parts of the parameter space of the same benchmark model, providing a complementary way to search for new physics.

[en] The ArDM experiment completed a single-phase commissioning run (ArDM Run I) with an active liquid argon target of nearly one tonne in mass. The analysis of the data and comparison to predictions from full detector simulations allowed extraction of the detector properties and an assessment of the low background conditions. The ³⁹Ar specific activity from the employed atmospheric argon is measured to be (0.95±0.05) Bq/kg. The cosmic muon flux at the Canfranc underground site was determined to be in the range (2–3.5)× 10⁻³m⁻²s⁻¹. The statistical rejection power for electronic recoil events using the pulse shape discrimination method was estimated using a ²⁵²Cf neutron calibration source. Electronic and nuclear recoil band profiles were found to be well described by Gaussian distributions. Employing such a model we derive values for the electronic recoil statistical rejection power of more than 10⁸ in the tonne-scale liquid argon target for events with more than 50 detected photons at a 50% acceptance for nuclear recoils. The ²²²Rn emanation rate of the ArDM cryostat at room temperature was found to be (65.6±0.4) μHz/l. These results represent an important physics milestone for the next run in the double-phase mode and in the context of foreseen developments towards the use of depleted argon targets.

[en] The ASACUSA collaboration aims at measuring the ground state hyperfine splitting of antihydrogen for probing fundamental symmetries. A cryogenic trap for mixing antiprotons and positrons serves as an antihydrogen source for in-flight spectroscopy. In order to be able to monitor the antihydrogen formation process, a dedicated Micromegas tracking detector has been designed and built to record the annihilation distribution in the trap. In this paper, we present the first results from antiproton annihilation data recorded with the Micromegas, together with a description of the event reconstruction algorithm.