We have developed a compact detector for measuring beam particles using plastic scintillators readout through Multi-Pixel Photon Counters, which is employed for hypernuclear measurements in the WASA-FRS experiment at GSI. The Time-of-Flight resolution of the newly-developed detector has been investigated in relation to the overvoltage with respect to the breakdown voltage, a maximum counting rate of approximately 3 x 10(6)/s per segment, and a maximum beam charge of Z = 6. The evaluated Time-of-Flight resolutions between the neighboring segments of the detector range from 44.6 +/- 1.3 ps to 100.3 +/- 3.6 ps (sigma) depending on the segment, overvoltage values, and beam intensity. It is also observed that the Time-of-Flight resolution is inversely correlated to the beam atomic charge (Z).

We conducted an experimental search for 77 ' -mesic nuclei, bound systems of an 77 ' meson and a nucleus, in 12 C( p, dp ) reactions. We measured the missing mass in the ( p, d ) reaction to obtain the mass spectrum of the reaction product near the 77 ' emission threshold. Forward-emitted deuterons were momentum-analyzed in the FRS of GSI. We installed a nearly 4 7r detector WASA near the 12 C target to effectively select formation and decay of the 77 ' -mesic nuclei. We are presently finalizing the analysis.

The FRagment Separator FRS at GSI is a versatile spectrometer and separator for experiments with relativistic in-flight separated short-lived exotic beams. One branch of the FRS is connected to the target hall where the bio-medical cave (Cave M) is located. Recently a joint activity between the experimental groups of the FRS and the biophysics at the GSI and Department of physics at LMU was started to perform biomedical experiments relevant for hadron therapy with positron emitting carbon and oxygen beams. This paper presents the new ion-optical mode and commissioning results of the FRS-Cave M branch where positron emitting 15O-ions were provided to the medical cave for the first time. An overall conversion efficiency of 2.9±0.2×10-4 15O fragments per primary 16O ion accelerated in the synchrotron SIS18 was reached.

A novel technique to study bound states of exotic hadrons in subatomic nuclei, such as hypernuclei and mesic nuclei, has been developed by employing the Fragment Separator FRS and the WASA central detector at GSI. Two experiments, S447 for studying light hypernuclei, especially hypertriton and a Λnn bound state, and S490 for searching for η' mesic-nuclei, were recently performed. Data analyses are currently in progress, and light charged particles such as protons and π± are clearly observed and identified in the both experiments. For S447, light nuclear fragments that can also be residual nuclei from decays of hypernuclei of interests have been analysed by the FRS, and a momentum resolution, Δp/p, of 5×10−4 has been achieved. Further data analyses are to be completed. The WASA-FRS project will be continued and extended with the FRS at FAIR Phase 0, and upgrading of the WASA magnet and detectors is currently in progress. Furthermore, construction of a larger detector system with the Super-FRS at FAIR Phase 1 is also under consideration.

Interests on few-body hypernuclei have been increased by recent results of experiments employing relativistic heavy ion beams. Some of the experiments have revealed that the lifetime of the lightest hypernucleus, hypertriton, is significantly shorter than 263 ps which is expected by considering the hypertriton to be a weakly-bound system. The STAR collaboration has also measured the hypertriton binding energy, and the deduced value is contradicting to its formerly known small binding energy. These measurements have indicated that the fundamental physics quantities of the hypertriton such as its lifetime and binding energy have not been understood, therefore, they have to be measured very precisely. Furthermore, an unprecedented Λnn bound state observed by the HypHI collaboration has to be studied in order to draw a conclusion whether or not such a bound state exists. These three-body hypernuclear states are studied by the heavy-ion beam data in the WASA-FRS experiment and by analysing J-PARC E07 nuclear emulsion data with machine learning.

An experiment was performed at GSI with the objective of measuring theβ-intensity distribution in the decay of Hg, Au and Pt isotopes around N=126 using the total absorption gamma-ray spectroscopy technique. The aim is to benchmark theoretical models used to make predictions of half-life and neutron emission probabilities of exotic nuclei involved in the rapid neutron capture process, leading to the synthesis of very heavy elements. This paper presents some experimental details and the current status of the analysis.

Low-energy investigations on rare ion beams are often limited by the available intensity and purity of the ion species in focus. Here, we present the first application of a technique that combines in-flight production at relativistic energies with subsequent secondary beam storage, accumulation and finally deceleration to the energy of interest. Using the FRS and ESR facilities at GSI, this scheme was pioneered to provide a secondary beam of ^118Te^52+ for the measurement of nuclear proton-capture at energies of 6 and 7 MeV/u. The technique provided stored beam intensities of about 10^6 ions at high purity and brilliance, representing a major step towards low-energy nuclear physics studies using rare ion beams.

A bstract A search for the exclusive decays of the Higgs and Z bosons to a ϕ or ρ meson and a photon is performed with a pp collision data sample corresponding to an integrated luminosity of up to 35 . 6 fb −1 collected at $$ \sqrt{s}=13 $$ s = 13 TeV with the ATLAS detector at the CERN Large Hadron Collider. These decays have been suggested as a probe of the Higgs boson couplings to light quarks. No significant excess of events is observed above the background, as expected from the Standard Model. Upper limits at 95% confidence level were obtained on the branching fractions of the Higgs boson decays to ϕ γ and ρ γ of 4 . 8 × 10 −4 and 8 . 8 × 10 −4 , respectively. The corresponding 95% confidence level upper limits for the Z boson decays are 0 . 9 × 10 −6 and 25 × 10 −6 for ϕ γ and ρ γ, respectively.

We have developed a new and unique experimental setup integrating the central part of the Wide Angle Shower Apparatus (WASA) into the Fragment Separator (FRS) at GSI. This combination opens up possibilities of new experiments with high-resolution spectroscopy at forward 0 and measurements of light decay particles with nearly full solid-angle acceptance in coincidence. The first series of the WASA-FRS experiments have been successfully carried out in 2022. The developed experimental setup and two physics experiments performed in 2022 including the status of the preliminary data analysis are introduced.

The current understanding of light hypernuclei, which are sub-atomic nuclei with strangeness, is being challenged and studied in detail by several European research groups and collaborations. In recent years, studies of hypernuclei using high-energy heavy ion beams have reported unexpected results on the three-body hypernuclear state 3ΛH, named the hypertriton. For some time, reports of a shorter lifetime and larger binding energy than what was previously accepted have created a puzzling situation for its theoretical description; this is known as the "hypertriton puzzle". With the inclusion of the most recent experimental measurements, the current status of the hypertriton puzzle is evolving. Additionally, the possible neutral bound state of a Λ hyperon with two neutrons, nnΛ, has raised questions about our understanding of the formation of light hypernuclei either in bound or resonance states. These results have initiated several ongoing experimental programs all over the world to study these three-body hypernuclear states precisely. We are studying these light hypernuclear states by employing heavy ion beams at 2AGeV on a fixed carbon target with the WASA detector system and the Fragment Separator (FRS) at GSI. The WASA-FRS experimental campaign was performed during the first quarter of 2022, and this paper presents a short overview of the campaign and how it seeks to tackle the hypertriton and nnΛ puzzles. Data analysis is ongoing, and several preliminary results will be reported.

New tracking detectors are necessary for beam diagnostics and event-by-event particle identification for the Super-FRS, a next generation reaction product separation being constructed at GSI/FAIR in Germany. Novel detectors and electronics are currently being developed to meet the stringent requirements of this forefront fragment separator due to high radiation levels, long term electronic stability and the required homogeneity of materials in the beam, while maintaining very high tracking efficiency. The present contribution focuses on the electronics for a new Gas Electron Multiplier (GEM)-based Time Projection Chamber (TPC) to provide the position information, which are needed to reconstruct the A/q of the fragment from protons to uranium ions. The most recent Front End Electronics (FEE) developed at GSI with a novel Amplifier With Adaptive Gain Settings (AWAGS) ASIC are being tested. This FEE has a low noise level (sub fC), a large dynamic range (up to similar to 71 pC) with excellent timing properties. The AWAGS uses a switched capacitance technique instead of fixed feedback capacitors to provide the large dynamic range. Results from the ASIC characterisation studies and the outlook for a new, updated chip for the full read out chain of the GEM TPC are presented.

The DEcay SPECtroscopy (DESPEC) setup for nuclear structure investigations was developed and commissioned at GSI, Germany in preparation for a full campaign of experiments at the FRS and Super-FRS. In this paper, we report on the first employment of the setup in the hybrid configuration with the AIDA implanter coupled to the FATIMA LaBr3(Ce) fast-timing array, and high-purity germanium detectors. Initial results are shown from the first experiments carried out with the setup. An overview of the setup and function is discussed, including technical advancements along the path.

The first measurement of longitudinal decorrelations of harmonic flow amplitudes v_{n} for n=2-4 in Xe+Xe collisions at sqrt[s_{NN}]=5.44  TeV is obtained using 3  μb^{-1} of data with the ATLAS detector at the LHC. The decorrelation signal for v_{3} and v_{4} is found to be nearly independent of collision centrality and transverse momentum (p_{T}) requirements on final-state particles, but for v_{2} a strong centrality and p_{T} dependence is seen. When compared with the results from Pb+Pb collisions at sqrt[s_{NN}]=5.02  TeV, the longitudinal decorrelation signal in midcentral Xe+Xe collisions is found to be larger for v_{2}, but smaller for v_{3}. Current hydrodynamic models reproduce the ratios of the v_{n} measured in Xe+Xe collisions to those in Pb+Pb collisions but fail to describe the magnitudes and trends of the ratios of longitudinal flow decorrelations between Xe+Xe and Pb+Pb. The results on the system-size dependence provide new insights and an important lever arm to separate effects of the longitudinal structure of the initial state from other early and late time effects in heavy-ion collisions.

After the Long Shutdown 2 (Dec. 2018 – Feb. 2021), the LHC will be a new machine in many respects and produce collisions with a center-of-mass energy at or near 14 TeV. The instantaneous luminosities can be expected to reach 2× 1034 cm−2s−1, which is two times the original design value. The mean number of interactions per bunch crossing is expected to go up to 80. To meet the challenges of the high-luminosity environment (much higher event rates and pileup level), several major upgrades will be installed during the Long Shutdown 2 in the ATLAS detector. As a part of the updates, the Level-1 calorimeter trigger will be upgraded to exploit higher granularity data compared to those available during Run 2 by using a new system of feature extraction modules, which each reconstructs different physics objects at Level-1. The Jet Feature Extractor (jFEX) is one of three feature extraction modules and has been conceived to identify small-/large-area jets, large-area τ leptons, missing transverse energy and the total sum of the transverse energy. The Xilinx Virtex UltraScale+ FPGA fulfills the physics requirements of significant processing power and large input bandwidth within a tight latency budget. The modular design optimizes a large number of high-speed signals within the limited space of an ATCA board. To guarantee the signal integrity, the board design has been accompanied by simulation of the power, current, and thermal distributions. The printed circuit board has a 24-layer stack-up and uses the MEGTRON6 material, which is commonly used for signal transmission above 10 Gb/s. This contribution focuses on the technological aspects of the jFEX module, reporting on the simulation studies and the design solutions of the board. Two jFEX prototypes and one pre-production module have been produced and tested at CERN with other systems, and these test results are presented. The firmware implemented on the trigger board will be illustrated in connection with the FPGA performance and board power consumption. The whole jFEX system, consisting of 6 boards, will be produced by the end of 2019 to allow the installation and commissioning of the full system in time for the LHC restart at the beginning of 2021.

This paper presents a search for direct top squark pair production in events with missing transverse momentum plus either a pair of jets consistent with Standard Model Higgs boson decay into b-quarks or a same-flavour opposite-sign dilepton pair with an invariant mass consistent with a Z boson. The analysis is performed using the proton–proton collision data at \n$$\\sqrt{s}=13$$\n\n TeV collected with the ATLAS detector during the LHC Run-2, corresponding to an integrated luminosity of 139 fb\n$$^{-1}$$\n\n. No excess is observed in the data above the Standard Model predictions. The results are interpreted in simplified models featuring direct production of pairs of either the lighter top squark (\n$$\\tilde{t}_1$$\n\n) or the heavier top squark (\n$$\\tilde{t}_2$$\n\n), excluding at 95% confidence level \n$$\\tilde{t}_1$$\n\n and \n$$\\tilde{t}_2$$\n\n masses up to about 1220 and 875 GeV, respectively.

The production cross-sections for W +/- and Z bosons are measured using ATLAS data corresponding to an integrated luminosity of 4.0 pb-1 collected at a centre-ofmass energy v s = 2.76 TeV. The deca ...

This Letter presents a search for new light resonances decaying to pairs of quarks and produced in association with a high-pT photon or jet. The dataset consists of proton–proton collisions with an integrated luminosity of 36.1 fb−1 at a centre-of-mass energy of s=13 TeV recorded by the ATLAS detector at the Large Hadron Collider. Resonance candidates are identified as massive large-radius jets with substructure consistent with a particle decaying into a quark pair. The mass spectrum of the candidates is examined for local excesses above background. No evidence of a new resonance is observed in the data, which are used to exclude the production of a lepto-phobic axial-vector Z′ boson.

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés. φ-Meson production at forward rapidity in p-Pb collisions at √ S_NN=5.02 TeV and in pp collisions at √ S=2.76 TeV J-L. Charvet, V.J.G. Feuillard, A. Rakotozafindrabe, J. Adam, Laurent Aphecetche, B. Audurier, A. Baldisseri, H. Borel, J. Castillo Castellanos, C. Cheshkov, et al.