Markus Merschmeyer

Using the large acceptance apparatus FOPI, we study pion emission in the reactions (energies in AGeV are given in parentheses): 40Ca + 40Ca (0.4, 0.6, 0.8, 1.0, 1.5, 1.93), 96Ru + 96Ru (0.4, 1.0, 1.5), 96Zr + 96Zr (0.4, 1.0, 1.5), 197Au + 197Au (0.4, 0.6, 0.8, 1.0, 1.2, 1.5). The observables include longitudinal and transverse rapidity distributions and stopping, polar anisotropies, pion multiplicities, transverse momentum spectra, ratios (π+/π−) of average transverse momenta and of yields, directed flow, elliptic flow. The data are compared to earlier data where possible and to transport model simulations.

Using the large acceptance apparatus FOPI, we study central collisions in the reactions (energies in A GeV are given in parentheses): 40Ca + 40Ca (0.4, 0.6, 0.8, 1.0, 1.5, 1.93), 58Ni + 58Ni (0.15, 0.25, 0.4), 96Ru + 96Ru (0.4, 1.0, 1.5), 96Zr + 96Zr (0.4, 1.0, 1.5), 129Xe + CsI (0.15, 0.25, 0.4), 197Au + 197Au (0.09, 0.12, 0.15, 0.25, 0.4, 0.6, 0.8, 1.0, 1.2, 1.5). The observables include cluster multiplicities, longitudinal and transverse rapidity distributions and stopping, and radial flow. The data are compared to earlier data where possible and to transport model simulations.

Using the large acceptance apparatus FOPI, we study central and semi-central collisions in the reactions (energies in AGeV are given in parentheses): 40Ca + 40Ca (0.4, 0.6, 0.8, 1.0, 1.5, 1.93), 58Ni + 58Ni (0.15, 0.25, 0.4), 96Ru + 96Ru (0.4, 1.0, 1.5), 96Zr + 96Zr (0.4, 1.0, 1.5), 129Xe + CsI (0.15, 0.25, 0.4), 197Au + 197Au (0.09, 0.12, 0.15, 0.25, 0.4, 0.6, 0.8, 1.0, 1.2, 1.5). The observables include directed and elliptic flow. The data are compared to earlier data where possible and to transport model simulations. A stiff nuclear equation of state is found to be incompatible with the data. Evidence for extra-repulsion of neutrons in compressed asymmetric matter is found.

We present measurements of the excitation function of elliptic flow at midrapidity in Au + Au collisions at beam energies from 0.09 to 1.49 GeV per nucleon. For the integral flow, we discuss the interplay between collective expansion and spectator shadowing for three centrality classes. A complete excitation function of transverse momentum dependence of elliptic flow is presented for the first time in this energy range, revealing a rapid change with incident energy below 0.4AGeV, followed by an almost perfect scaling at the higher energies. The equation of state of compressed nuclear matter is addressed through comparisons to microscopic transport model calculations.

We present a complete systematics (excitation functions and system-size dependences) of global stopping and side flow for heavy ion reactions in the energy range between $0.09A$ and $1.93A\text{ }\text{ }\mathrm{GeV}$. For the heaviest system, $\mathrm{Au}+\mathrm{Au}$, we observe a plateau of maximal stopping extending from about $0.2A$ to $0.8A\text{ }\text{ }\mathrm{GeV}$ with a fast drop on both sides. The degree of stopping, which is shown to remain significantly below the expectations of a full stopping scenario, is found to be highly correlated to the amount of side flow.

We present new experimental data on directed flow in collisions of $\mathrm{Au}+\mathrm{Au},$ $\mathrm{Xe}+\mathrm{CsI},$ and $\mathrm{Ni}+\mathrm{Ni}$ at incident energies from $90A$ to $400A\mathrm{MeV}.$ We study the centrality and system dependence of integral and differential directed flow for particles selected according to charge. All the features of the experimental data are compared with isospin quantum molecular dynamics (IQMD) model calculations in an attempt to extract information about the nuclear matter equation of state (EoS). We show that the combination of rapidity and transverse momentum analysis of directed flow allows to disentangle various parametrizations in the model. At $400A\mathrm{MeV},$ a soft EoS with momentum dependent interactions is best suited to explain the experimental data in $\mathrm{Au}+\mathrm{Au}$ and $\mathrm{Xe}+\mathrm{CsI},$ but in the case of $\mathrm{Ni}+\mathrm{Ni}$ the model underpredicts flow for any EoS. At $90A\mathrm{MeV}$ incident beam energy, none of the IQMD parametrizations studied here are able to consistently explain the experimental data.

The K 0 meson production by À mesons of 1:15 GeV=c momentum on C, Al, Cu, Sn, and Pb nuclear targets was measured with the FOPI spectrometer at the Schwer-Ionen-Synchrotron accelerator of GSI.Inclusive production cross sections and the momentum distributions of K 0 mesons are compared to scaled elementary production cross sections and to predictions of theoretical models describing the in-medium production of kaons.The data represent a new reference for those models, which are widely used for interpretation of the strangeness production in heavy-ion collisions.The presented results demonstrate the sensitivity of the kaon production to the reaction amplitudes inside nuclei and point to the existence of a repulsive KN potential of 20 AE 5 MeV at normal nuclear matter density.

First measurement of subthreshold \ensuremath{\Sigma}(1385) production is presented. Experimental data are presented for Al+Al reactions at $1.9A$ GeV measured with the FOPI detector at SIS/GSI. The $\ensuremath{\Sigma}(1385)/\ensuremath{\Lambda}$ ratio is found to be in good agreement with the transport and statistical model predictions. The results allow for a better understanding of subthreshold strangeness production and strangeness exchange reaction which is the dominant process for ${K}^{\ensuremath{-}}$ production below and close-to threshold.

New results concerning the production of neutral strange particles, ${K}^{0}$ and \ensuremath{\Lambda} in Ni+Ni collisions at $1.93A$ GeV, measured with the FOPI detector at GSI Darmstadt, are presented. Rapidity density distributions and Boltzmann slope parameter distributions are measured in nearly the full phase space of the reaction. The observables are compared to existing ${K}^{+}$ and proton data. While the ${K}^{0}$ data agree with previously reported ${K}^{+}$ measurements, the \ensuremath{\Lambda} distributions show a different behavior relative to that of protons. The strangeness balance and the production yield per participating nucleon as a function of the centrality of the reaction are discussed, for the first time at GSI Schwerionen Synchrotron (SIS) energies.

Results on ${K}^{+}$ and ${K}^{0}$ meson production in ${}_{44}^{96}\mathrm{Ru}$ + ${}_{44}^{96}\mathrm{Ru}$ and ${}_{40}^{96}\mathrm{Zr}$ + ${}_{40}^{96}\mathrm{Zr}$ collisions at a beam kinetic energy of 1.528$A$ GeV, measured with the FOPI detector at GSI-Darmstadt, are investigated as a possible probe of isospin effects in high-density nuclear matter. The measured double ratio (${K}^{+}/{K}^{0}$)${}_{\mathrm{Ru}}$/(${K}^{+}/{K}^{0}$)${}_{\mathrm{Zr}}$ is compared to the predictions of a thermal model and a relativistic mean field transport model using two different collision scenarios and under different assumptions on the stiffness of the symmetry energy. We find good agreement with the thermal model prediction and the assumption of a soft symmetry energy for infinite nuclear matter, while more realistic transport simulations of the collisions show a similar agreement with the data but also exhibit a reduced sensitivity to the symmetry term.

The Compact Muon Solenoid (CMS) experiment prepares its Phase-2 upgrade for the high-luminosity era of the LHC operation (HL-LHC). Due to the increase of occupancy, trigger latency and rates, the full electronics of the CMS Drift Tube (DT) chambers will need to be replaced. In the new design, the time bin for the digitization of the chamber signals will be of around 1 ns, and the totality of the signals will be forwarded asynchronously to the service cavern at full resolution. The new backend system will be in charge of building the trigger primitives of each chamber. These trigger primitives contain the information at chamber level about the muon candidates position, direction, and collision time, and are used as input in the L1 CMS trigger. The added functionalities will improve the robustness of the system against ageing. An algorithm based on analytical solutions for reconstructing the DT trigger primitives, called Analytical Method, has been implemented both as a software C++ emulator and in firmware. Its performance has been estimated using the software emulator with simulated and real data samples, and through hardware implementation tests. Measured efficiencies are 96 to 98% for all qualities and time and spatial resolutions are close to the ultimate performance of the DT chambers. A prototype chain of the HL-LHC electronics using the Analytical Method for trigger primitive generation has been installed during Long Shutdown 2 of the LHC and operated in CMS cosmic data taking campaigns in 2020 and 2021. Results from this validation step, the so-called Slice Test, are presented.

Abstract High-speed multichannel ADCs are costly and require complex FPGA or MCU firmware to communicate with them. The Multi-Voltage Thresholding (MVT) approach can replace to some extent an external ADC by harnessing the internal FPGA resources, thus reducing costs and complexity. The MVT approach needs only a few low-cost external components. The focus of the contribution is presenting an open-source IP-Core that implements the MVT approach and simplifies its implementation on a standard FPGA. The contribution also provides an overview of characterization measurements and specific calibration method. Our example application demonstrates the viability of the developed IP-Core for signal acquisition from multiple SiPMs.

Small-angle correlations of pairs of protons emitted in central collisions of Ca + Ca, Ru + Ru and Au + Au at beam energies from 400 to 1500MeV per nucleon are investigated with the FOPI detector system at SIS/GSI Darmstadt. Dependences on system size and beam energy are presented which extend the experimental data basis of pp correlations in the SIS energy range substantially. The size of the proton-emitting source is estimated by comparing the experimental data with the output of a final-state interaction model which utilizes either static Gaussian sources or the one-body phase-space distribution of protons provided by the BUU transport approach. The trends in the experimental data, i.e. system size and beam energy dependences, are well reproduced by this hybrid model. However, the pp correlation function is found rather insensitive to the stiffness of the equation of state entering the transport model calculations.

We present transverse momentum and rapidity spectra of charged pions in central Ru + Ru collisions at 400$A$ and 1528$A$ MeV. The data exhibit enhanced production at low transverse momenta compared to the expectations from the thermal model that includes the decay of $\Delta(1232)$-resonances and thermal pions. Modification of the $\Delta$-spectral function and the Coulomb interaction are necessary to describe the detailed shape of the transverse momentum spectra. Within the framework of the thermal model, the freeze-out radii of pions are similar at both beam energies. The IQMD model reproduces the shapes of the transverse momentum and rapidity spectra of pions, but the predicted absolute yields are larger than in the measurements, especially at lower beam energy.

The $\phi$-meson production cross section is measured for the first time at a sub-threshold energy of 1.93 AGeV in \nuc{58}{Ni}+\nuc{58}{Ni} central collisions. The $\phi$ data were obtained within the acceptance of the CDC/Barrel subsystem of FOPI. For a sample of $4.7\cdot 10^6$ central events, after background subtraction, 23 candidates were observed. Extensive GEANT simulations of the detector performance are shown in a thorough comparison to the real response, aiming at a good understanding of the apparatus and at a trustable determination of the efficiencies, production probability and possible systematic errors. A filter procedure is elaborated, which is meant to facilitate the comparison of any theoretical calculation or new data with the current ones. How to extrapolate the present value to a $\phi$-meson cross section in $4\pi$ is also discussed. This result on pseudo-vector mesons can now be compared to existing experimental knowledge for the same reaction at the same incident energy for various outgoing channels, $K^+$ and $K^-$ included. A significant fraction (at least 20%) of the $K^-$-mesons is originating in the decay of the $\phi$, supporting the statement that the two channels are strongly correlated.

We report on the first analysis of directed and elliptic flow with the new method of Lee--Yang zeros. Experimental data are presented for Ru+Ru reactions at 1.69A GeV measured with the FOPI detector at SIS/GSI. The results obtained with several methods, based on the event-plane reconstruction, on Lee--Yang zeros, and on multiparticle cumulants (up to fifth order) applied for the first time at SIS energies, are compared. They show conclusive evidence that azimuthal correlations between nucleons and composite particles at this energy are largely dominated by anisotropic flow.

The signal of silicon photomultipliers (SiPMs) depends not only on the number of incoming photons but also on thermal and correlated noise of which the latter is difficult to handle. Additionally, the properties of SiPMs vary with the supplied bias voltage and the ambient temperature. The purpose of the G4SiPM simulation package is the integration of a detailed SiPM simulation into Geant4 which is widely used in particle physics. The prediction of the G4SiPM simulation code is validated with a laboratory measurement of the dynamic range of a 3×3 mm2 SiPM with 3600 cells manufactured by Hamamatsu.

Cluster production is investigated in central collisions of Ca+Ca, Ni+Ni, 96Zr+96Zr, 96Ru+96Ru, Xe+CsI and Au+Au reactions at 0.4 AGeV incident energy. We find that the multiplicity of clusters with charge Z⩾3 grows quadratically with the system's total charge and is associated with a midrapidity source with increasing transverse velocity fluctuations. When reduced to the same number of available charges, an increase of cluster production by about a factor of 5.5 is observed in the midrapidity region between the lightest system (Ca+Ca) and the heaviest one (Au+Au). The results, as well as simulations using quantum molecular dynamics, suggest a collision process where droplets, i.e., nucleon clusters, are created in an expanding, gradually cooling, nucleon gas. Within this picture, expansion dynamics, collective radial flow and cluster formation are closely linked as a result of the combined action of nucleon–nucleon scatterings and the mean fields.

Scintillator- and fibre-based particle detectors with SiPM readout are an indispensable tool in high-energy particle physics, medical physics and other fields of application. For designing and understanding these detectors, very detailed simulations are necessary, which require an accurate modelling of the optical physics (optics, scintillation, wavelength-shifting effects, ... ), of the optical material properties, and of the geometry. To allow for a reliable usage also by less experienced users, the necessary complexity and flexibility of a suitable simulation framework must not lead to an increasing danger of user mistakes. Additionally, the required effort for creating or modifying a detailed simulation has to be minimised in order to allow for the fast creation of flexible simulation setups. These challenges have been addressed by developing GODDeSS (Geant4 Objects for Detailed Detectors with Scintillators and SiPMs). It is an extension of the particle-physics simulation tool Geant4 and allows for the easy simulation of optical detector components, especially combinations of scintillators, optical fibres, and photodetectors. GODDeSS enables the user to create extensive setups for Geant4 simulations with a few lines of source code. At the same time, GODDeSS helps to avoid typical user mistakes. This paper introduces the basic concepts of the GODDeSS framework, its object classes, and its functionality. Furthermore, test measurements with prototype modules will be presented, which were performed to validate simulation results of the GODDeSS framework.

We analyzed the $\ensuremath{\phi}$ meson production in central Ni + Ni collisions at a beam kinetic energy of 1.93A GeV with the FOPI spectrometer and found a production probability per event of $[8.6\ifmmode\pm\else\textpm\fi{}1.6(\text{stat})\ifmmode\pm\else\textpm\fi{}1.5(\text{syst})]\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$. This new data point allows us for the first time to inspect the centrality dependence of subthreshold $\ensuremath{\phi}$ meson production in heavy-ion collisions. The rise of $\ensuremath{\phi}$ meson multiplicity per event with mean number of participants can be parametrized by a power function with exponent $\ensuremath{\alpha}=1.8\ifmmode\pm\else\textpm\fi{}0.6$. The ratio of $\ensuremath{\phi}$ to ${K}^{\ensuremath{-}}$ production yields seems not to depend, within the experimental uncertainties, on the collision centrality, and the average of measured values was found to be $0.36\ifmmode\pm\else\textpm\fi{}0.05$.

New measurement of sub-threshold $K^*(892)^0$ and $K^0$ production is presented. The experimental data complete the measurement of strange particles produced in Al+Al collisions at 1.9$A$ GeV measured with the FOPI detector at SIS/GSI. The $K^*(892)^0$ / $K^0$ yield ratio is found to be $0.0315\pm 0.006 (\mathrm{stat.})\pm 0.012 (\mathrm{syst.})$ and is in good agreement with the UrQMD model prediction. These measurements provide information on in-medium cross section of $K^+$ - $\pi^-$ fusion which is the dominant process on sub-threshold $K^*(892)^0$ production.

Silicon Photomultipliers (SiPMs) are versatile and sensitive photon detectors that experience a fast growing variety of use in particle physics and related fields of application. These photo detectors have a very promising photon detection efficiency and are therefore interesting for very low light flux applications such as scintillation and fluorescence light detection. As a semiconductor device the SiPM׳s gain and time response strongly depend on the operating temperature and voltage. Thus they have to be understood for a proper use of the SiPM. Therefore, accurate electrical simulations of the SiPM׳s behavior involving electrical readout and front-end electronics help to improve the design of experimental setups, since several different designs can be tested and simulated with a manageable amount of effort. To perform these simulations, a detailed equivalent circuit of the SiPM has to be used containing a set of well-defined parameters. For this purpose, SPICE simulations of SiPMs and readout electronics have been performed. These simulations utilize an improved SiPM model consisting of resistors, capacitances and inductances. The SiPM parameters for these simulations have been determined by measuring the impedance over a wide frequency range while applying a DC voltage in forward direction and various DC voltages from zero up to the SiPM breakdown voltage in order to determine the behavior under operating conditions. The impedance measurements, the electrical model and the resulting simulations are presented. The impact of different setups and the electrical properties of the SiPM is discussed.

The FOPI Collaboration at the GSI SIS-18 synchrotron measured charged kaons from central and semicentral collisions of Ni+Ni at a beam energy of $1.91A$ GeV. We present the distribution of the ${K}^{\ensuremath{-}}/{K}^{+}$ ratio on the energy vs polar angle plane in the nucleon-nucleon center-of-mass frame, with and without subtraction of the contribution of $\ensuremath{\phi}(1020)$ meson decays to the ${K}^{\ensuremath{-}}$ yield. The acceptance of the current experiment is substantially wider compared to the previous measurement of the same colliding system. The ratio of ${K}^{\ensuremath{-}}$ to ${K}^{+}$ energy spectra is expected to be sensitive to the in-medium modifications of basic kaon properties like mass. Recent results obtained by the HADES Collaboration at $1.23A$ and $1.76A$ GeV indicate that after inclusion of the $\ensuremath{\phi}$ meson decay contribution to the ${K}^{\ensuremath{-}}$ production no difference between the slopes of the ${K}^{\ensuremath{-}}$ and ${K}^{+}$ energy spectra is observed within uncertainties. For our data a linear fit to this ratio obtained after subtraction of the $\ensuremath{\phi}$ meson contribution still shows a decrease with kinetic energy, although a constant value cannot be rejected. The contribution of $\mathrm{\ensuremath{\Lambda}}(1520)\ensuremath{\rightarrow}p{K}^{\ensuremath{-}}$ decays estimated from fitting the thermal model to the experimental yields appears to be another factor of moderate relevance.

New results on nuclear collective flow are presented for central and semi-central Ru + Ru collisions at 400 A MeV measured with the FOPI detector at GSI-Darmstadt. The source shape parameters, flow angle and aspect ratios, are extracted from Gaussian fits to in-plane and out-of-plane momentum distributions. The orientation and the shape of the source exhibit different trends according to the investigated phase space region. The shape parameters of the participant source are studied as a function of the particle mass and collision centrality. The flow angle is found to be independent of the particle mass. Both the flow angle and the aspect ratios depend sensitively on the impact parameter. Detailed comparisons with the predictions of the isospin quantum molecular dynamics model are performed. It is shown in particular that the source shape parameters permit to extract information on the in-medium nucleon–nucleon cross section.

The CMS drift tubes (DT) muon detector, built for withstanding the LHC expected integrated and instantaneous luminosities, will be used also in the High Luminosity LHC (HL-LHC) at a 5 times larger instantaneous luminosity and, consequently, much higher levels of radiation, reaching about 10 times the LHC integrated luminosity. Initial irradiation tests of a spare DT chamber at the CERN gamma irradiation facility (GIF++), at large (∼ O(100)) acceleration factor, showed ageing effects resulting in a degradation of the DT cell performance. However, full CMS simulations have shown almost no impact in the muon reconstruction efficiency over the full barrel acceptance and for the full integrated luminosity. A second spare DT chamber was moved inside the GIF++ bunker in October 2017. The chamber was being irradiated at lower acceleration factors, and only 2 out of the 12 layers of the chamber were switched at working voltage when the radioactive source was active, being the other layers in standby. In this way the other non-aged layers are used as reference and as a precise and unbiased telescope of muon tracks for the efficiency computation of the aged layers of the chamber, when set at working voltage for measurements. An integrated dose equivalent to two times the expected integrated luminosity of the HL-LHC run has been absorbed by this second spare DT chamber and the final impact on the muon reconstruction efficiency is under study. Direct inspection of some extracted aged anode wires presented a melted resistive deposition of materials. Investigation on the outgassing of cell materials and of the gas components used at the GIF++ are underway. Strategies to mitigate the ageing effects are also being developed. From the long irradiation measurements of the second spare DT chamber, the effects of radiation in the performance of the DTs expected during the HL-LHC run will be presented.

Silicon Photomultipliers (SiPMs) are semiconductor-based photon detectors. Their most important properties, gain and photon detection efficiency, are dependent on or influenced by voltage and temperature and need to be characterised for optimal usage of the SiPMs. The test setup has been built for optical and electrical characterisation of SiPMs. The setup provides a temperature-stabilised SiPM mount, an LED-based multi-purpose light source offers continuous and pulsed operation mode for wavelengths from 300 nm to 650 nm. The result is a complete characterisation of the SiPM within a desired range of operation voltage and ambient temperature.

During the High Luminosity LHC, the Drift Tube chambers installed in the CMS detector need to operate with an integrated dose ten times higher than expected at the LHC due to the increase in integrated luminosity from 300 fb-1 to 3000 fb-1. Irradiations have been performed to assess the performance of the detector under such conditions and to characterize the radiation aging of the detector. The presented analysis focuses on the behaviour of the high voltage currents and the dose measurements needed to extrapolate the results to High Luminosity conditions, using data from the photon irradiation campaign at GIF++ in 2016 as well as the efficiency analysis from the irradiation campaign started in 2017. Although the single-wire loss of high voltage gain observed of 70% is very high, the muon reconstruction efficiency is expected to decrease less than 20% during the full duration of High Luminosity LHC in the areas under highest irradiation.

The production yields and the directed flow of the neutral strange particles K0S and Λ(Λ0 + Σ0) have been measured with the FOPI detector at SIS/GSI in Ni+Ni collisions of 1.93 A GeV energy. For the K0, the distributions of the inverse slope parameter and the particle yield show good agreement with the results of previous K+ measurements. Furthermore, the directed flow patterns of K0 and K+ are found to be compatible. The comparison of Λ and proton exhibits a significant difference in the yield distribution whereas both particle species show the same flow behaviour.

Using the large acceptance apparatus FOPI, we study central and semi-central collisions in the reactions (energies in A GeV are given in parentheses): 40Ca+40Ca (0.4, 0.6, 0.8, 1.0, 1.5, 1.93), 58Ni+58Ni (0.15, 0.25, 0.4), 96Ru+96Ru (0.4, 1.0, 1.5), 96Zr+96Zr (0.4, 1.0, 1.5), 129Xe+CsI (0.15, 0.25, 0.4), 197Au+197Au (0.09, 0.12, 0.15, 0.25, 0.4, 0.6, 0.8, 1.0, 1.2, 1.5). The observables include directed and elliptic flow. The data are compared to earlier data where possible and to transport model simulations. A stiff nuclear equation of state is found to be incompatible with the data. Evidence for extra-repulsion of neutrons in compressed asymmetric matter is found.

To sustain and extend its discovery potential, the Large Hadron Collider (LHC) will undergo a major upgrade in the coming years, referred to as High Luminosity LHC (HLLHC), aimed to increase its instantaneous luminosity, 5 times larger than the designed limit, and, consequently leading to high levels of radiation, with the goal to collect 10 times larger the original designed integrated luminosity. The drift tube chambers (DT) of CMS muon detector system is built to proficiently measure and trigger on muons in the harsh radiation environment expected during the HL-LHC era. Ageing studies are performed at the CERNs gamma ray irradiation facility (GIF++) by measuring the muon hit efficiency of these detectors at various LHC operation conditions. One such irradiation campaign was started in October 2017, when a spare MB2 chamber moved inside the bunker and irradiated at lower acceleration factors. Two out of twelve layers of the DT chamber were operated while being irradiated with the radioactive source and then their muon hit efficiency was calculated in coincidence with other ten layers which were kept on the standby. The chamber absorbed an integrated dose equivalent to two times the expected integrated luminosity of the HL-LHC. Investigation on the outgassing of cell materials and of the gas components used at the GIF++ are underway and strategies to mitigate the aging effects are also being developed. The effect of radiation on the performance of DT chamber and its impact on the overall muon reconstruction efficiency expected during the HL-LHC are presented.

This thesis presents results on the production and the flow of $K^0$ and $\Lambda^0$ in Ni+Ni collisions at an energy of 1.93 AGeV. The analyzed data sample of 10$^8$ central events has been recorded during 12 days using an upgraded data acquisition with a fast online data reduction algorithm. Part of this work was the implementation of this algorithm on a digital signal processor. The slope parameter and yield distributions of the $K^0$ are found to agree with those of previously measured $K^+$. Comparisons to transport model calculations (UrQMD, IQMD) show that none of the models is able to consistently describe those distributions for both, $K^0$ and $\Lambda^0$. The integral and the differential directed flow of the $K^0$ are found to agree with that of the $K^+$, supporting the evidence for a repulsive $K^+$N potential. Comparing the directed flow of $\Lambda^0$ and protons, no significant difference is found between both for the integral as well as the differential flow. This brings up the issue of the strength of the in-medium $\Lambda$N potential and its relation to the magnitude of the observed flow. A method to reconstruct $\Xi^-$ and $\Sigma^-(1385)$ baryons has been developed and candidates of both particles have been identified. The very small reconstruction efficiency requires confirmation through an experiment with a significantly larger statistics, though.

Heavy-ion collisions at beam energies of 1 – 2 AGeV offer the possibility to investigate in-medium effects of strange hadrons. Experiments with Ni+Ni and Ru+Ru at beam kinetic energies of 1.93 AGeV and 1.69 AGeV, respectively, were performed and analysed. Possible evidence for in-medium effects was found in K+ flow and yield ratio of charged kaons. Recent results on ø meson production are also reported.