Event-by-event fluctuations of the particle yield ratios in heavy-ion collisions at 20 - 158 AGeV

Non-statistical event-by-event fluctuations are considered as an important signal for the critical endpoint of the QCD phase diagram. Event-by-event fluctuations of different observables are thus investigated in detail in current experiments but are also an important observable to be studied at the future CBM experiment at FAIR. In this work we present the energy and centrality dependence of event-by-event fluctuations of particle yield ratios measured by the NA49 experiment in Pb+Pb collisions at 20 - 158 AGeV. Systematic studies of the influence of the dE/dx resolution on the particle identification and the centrality bin size were performed. Results can be compared to event-by-event fluctuations measured by NA49 for different observables such as or the mean charged particle multiplicity. Main results of these studies are an increase of absolute value of the dynamical particle ratio fluctuations with decreasing centrality for all considered ratios, saturation of the K/Pi and K/p ratio fluctuations for peripheral Pb + Pb collisions at 158A GeV and scaling of the energy and centrality dependences of the p/Pi ratio fluctuations with NpNPi. The measured energy and centrality dependences of the K/Pi and K/p ratio fluctuations scale with NK in a different way. The saturation of the mentioned ratios fluctuations was attributed to the development of pronounced spike at zero in the eventwise ratio distributions, which, as was shown by Monte Carlo simulations, influence the measured fluctuations in the very peripheral Pb + Pb collisions at 158A GeV. In future, the CBM experiment at FAIR will investigate the intermediate region of the QCD phase diagram in great detail searching for the first order phase transition line and the expected critical endpoint. It is therefore important to closely investigate its sensitivity towards particle ratio fluctuations in Au+Au collisions at 10-45 AGeV beam energy. Detailed simulation studies will be presented. As an outcome of these feasibility studies we conclude that the CBM experiment will be able to provide high quality data on the subject of the event-by-event flucutations of particle yield ratios with sensitivity in the order of 1%.Nicht statistische “event-by-event” Fluktuationen werden als wichtiges Signal für die Suche nach dem kritischen Endpunkt des QCD Phasendiagramms angesehen. In aktuellen Experimenten werden aus diesem Grund bereits detailliert “Event-by-event” Fluktuationen verschiedener Observablen untersucht. Diese Fluktuationen werden aber auch eine wichtige Observable für das zukünftige CBM Experiment bei FAIR sein. In dieser Arbeit werden Ergebnisse zur Energie- und Zentralitätsabhängigkeit der “event-byevent” Fluktuationen von Teilchenzahl-Verhältnissen präsentiert. Die Daten stammen von Messungen des NA49 Experimentes bei Pb + Pb Stössen mit Strahlenergien von 20 - 158AGeV. Es wurden systematische Studien bezüglich des Einflusses der dE/dx Auflösung auf die Teilchenidentifikation und die Grösse der Zentralitäts-Bins durchgeführt. Die Ergebnisse dieser Arbeit können mit weiteren Ergebnissen der NA49 Kollaborartion über “event-by-event” Fluktuationen von Observablen wie der mittleren Multiplizität geladener Teilchen oder verglichen werden. Die Hauptergebnisse dieser Arbeit sind ein Ansteigen der dynamischen Teilchenzahl-Verhältnis Fluktuationen mit abnehmender Multiplizität bei allen untersuchen Verhältnissen, eine Sättigung der Fluktuationen der K/Pi- und K/p-Verhältnisse für periphere Pb + Pb Stösse bei 158AGeV Strahlenergie und eine Skalierung der Energie- und Zentralitätsabhängigkeit der p/Pi-Verhältnis Fluktuationen mit NpNPi. Die gemessenen Energie- und Zentralitätsabhängigkeiten der K/Pi- und K/p-Verhältnis Fluktuationen skalieren mit NK in unterschiedlicherWeise. Die Sättigung der genannten Verhältnis Fluktuationen bei Ereignissweiser Auswertung der Daten werden mit der Ausbildung einer Singularität bei Null erklärt. Mittels Monte Carlo Simulationen kann gezeigt werden, dass die Singularität die gemessenen Fluktuationen in sehr peripheren Pb + Pb Stössen bei 158 AGeV beeinflusst. Das zukünftige CBM Experiment bei FAIR wird ganz speziell den Übergangsbereich des QCD Phasendiagramms untersuchen um nach dem Phasen-Übergang erster Ordnung und dem vorhergesagten kritischen Endpunkt zu suchen. Aus diesem Grund ist es wichtig die Sensitivität des Experiments für die Teilchenzahlverhältnis Fluktuationen im Bereich von 10-45 AGeV zu untersuchen. Hierzu werden in dieser Arbeit detaillierte Simulationen präsentiert, die als Ergebnis zeigen dass das CBM Experiment Daten erzeugen kann mit Hilfe derer man für die “event-by-event” Fluktuationen eine Sensitivität im Bereich von 1% erreichen kann

Coulomb dissociation of O-16 into He-4 and C-12

We measured the Coulomb dissociation of O-16 into He-4 and C-12 within the FAIR Phase-0 program at GSI Helmholtzzentrum fur Schwerionenforschung Darmstadt, Germany. From this we will extract the photon dissociation cross section O-16(alpha,gamma)C-12, which is the time reversed reaction to C-12(alpha,gamma)O-16. With this indirect method, we aim to improve on the accuracy of the experimental data at lower energies than measured so far. The expected low cross section for the Coulomb dissociation reaction and close magnetic rigidity of beam and fragments demand a high precision measurement. Hence, new detector systems were built and radical changes to the (RB)-B-3 setup were necessary to cope with the high-intensity O-16 beam. All tracking detectors were designed to let the unreacted O-16 ions pass, while detecting the C-12 and He-4

Coulomb dissociation of 16O into 4He and 12C

We measured the Coulomb dissociation of 16O into 4He and 12C at the R3B setup in a first campaign within FAIR Phase 0 at GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt. The goal was to improve the accuracy of the experimental data for the 12C(a,?)16O fusion reaction and to reach lower center-ofmass energies than measured so far. The experiment required beam intensities of 109 16O ions per second at an energy of 500 MeV/nucleon. The rare case of Coulomb breakup into 12C and 4He posed another challenge: The magnetic rigidities of the particles are so close because of the same mass-To-charge-number ratio A/Z = 2 for 16O, 12C and 4He. Hence, radical changes of the R3B setup were necessary. All detectors had slits to allow the passage of the unreacted 16O ions, while 4He and 12C would hit the detectors' active areas depending on the scattering angle and their relative energies. We developed and built detectors based on organic scintillators to track and identify the reaction products with sufficient precision

Titel Event-by-event fluctuations of the particle yield ratios in heavy-ion collisions at 20 - 158 AGeV

Non-statistical event-by-event fluctuations are considered as an important signal for the critical endpoint of the QCD phase diagram. Event-by-event fluctuations of different observables are thus investigated in detail in current experiments but are also an important observable to be studied at the future CBM experiment at FAIR. In this work we present the energy and centrality dependence of event-by-event fluctuations of particle yield ratios measured by the NA49 experiment in Pb+Pb collisions at 20 - 158 AGeV. Systematic studies of the influence of the dE/dx resolution on the particle identification and the centrality bin size were performed. Results can be compared to event-by-event fluctuations measured by NA49 for different observables such as or the mean charged particle multiplicity. Main results of these studies are an increase of absolute value of the dynamical particle ratio fluctuations with decreasing centrality for all considered ratios, saturation of the K/Pi and K/p ratio fluctuations for peripheral Pb + Pb collisions at 158A GeV and scaling of the energy and centrality dependences of the p/Pi ratio fluctuations with NpNPi. The measured energy and centrality dependences of the K/Pi and K/p ratio fluctuations scale with NK in a different way. The saturation of the mentioned ratios fluctuations was attributed to the development of pronounced spike at zero in the eventwise ratio distributions, which, as was shown by Monte Carlo simulations, influence the measured fluctuations in the very peripheral Pb + Pb collisions at 158A GeV. In future, the CBM experiment at FAIR will investigate the intermediate region of the QCD phase diagram in great detail searching for the first order phase transition line and the expected critical endpoint. It is therefore important to closely investigate its sensitivity towards particle ratio fluctuations in Au+Au collisions at 10-45 AGeV beam energy. Detailed simulation studies will be presented. As an outcome of these feasibility studies we conclude that the CBM experiment will be able to provide high quality data on the subject of the event-by-event flucutations of particle yield ratios with sensitivity in the order of 1%

A High-Precision Tracking Algorithm for Mass Reconstruction of Heavy-Ion Fragments in the R3B Experiment at FAIR

The multi-purpose R3B (Reactions with Relativistic Radioactive Beams) setup at the future FAIR facility in Darmstadt will be used for various experiments with exotic beams in inverse kinematics. In front and after the reaction target a combination of detectors serves for particle identification and momentum measurements. In order to perform a high-precision charge identification of heavy-ion fragments and achieve a momentum resolution of 10-3 following is required: a time of flight (ToF) measurement with up to 15 ps accuracy, position determination on the order of less than 0.5 mm and a dedicated algorithm for the heavy-ion tracking in highly non-homogeneous dipole field. With these constraints a tracking package is being developed and tested within the R3B software framework, this package has to go into production in fall of 2018. An iterative approach has been chosen for simultaneous track finding and fitting. The design and concept of the package are introduced in this paper, also the tests and the resolution measured with simulated data are presented

A High-Precision Tracking Algorithm for Mass Reconstruction of Heavy-Ion Fragments in the R

The multi-purpose R3B (Reactions with Relativistic Radioactive Beams) setup at the future FAIR facility in Darmstadt will be used for various experiments with exotic beams in inverse kinematics. In front and after the reaction target a combination of detectors serves for particle identification and momentum measurements. In order to perform a high-precision charge identification of heavy-ion fragments and achieve a momentum resolution of 10-3 following is required: a time of flight (ToF) measurement with up to 15 ps accuracy, position determination on the order of less than 0.5 mm and a dedicated algorithm for the heavy-ion tracking in highly non-homogeneous dipole field. With these constraints a tracking package is being developed and tested within the R3B software framework, this package has to go into production in fall of 2018. An iterative approach has been chosen for simultaneous track finding and fitting. The design and concept of the package are introduced in this paper, also the tests and the resolution measured with simulated data are presented

ALFA: A framework for building distributed applications

The ALFA framework is a joint development between ALICE Online-Offline and FairRoot teams. ALFA has a distributed architecture, i.e. a collection of highly maintainable, testable, loosely coupled, independently deployable processes. ALFA allows the developer to focus on building singlefunction modules with well-defined interfaces and operations. The communication between the independent processes is handled by FairMQ transport layer. FairMQ offers multiple implementations of its abstract data transport interface, it integrates some popular data transport technologies like ZeroMQ and nanomsg. Furthermore it also provides shared memory and RDMA transport (based on libfabric) for high throughput, low latency applications. Moreover, FairMQ allows the single process to use multiple and different transports at the same time. FairMQ based processes can be controlled and orchestrated via different systems by implementing the corresponding plugin. However, ALFA delivers also the Dynamic Deployment System (DDS) as an independent set of utilities and interfaces, providing a dynamic distribution of different user processes on any Resource Management System (RMS) or a laptop. ALFA is already being tested and used by different experiments in different stages of data processing as it offers an easy integration of heterogeneous hardware and software

ALFA: A framework for building distributed applications

The ALFA framework is a joint development between ALICE Online-Offline and FairRoot teams. ALFA has a distributed architecture, i.e. a collection of highly maintainable, testable, loosely coupled, independently deployable processes. ALFA allows the developer to focus on building singlefunction modules with well-defined interfaces and operations. The communication between the independent processes is handled by FairMQ transport layer. FairMQ offers multiple implementations of its abstract data transport interface, it integrates some popular data transport technologies like ZeroMQ and nanomsg. Furthermore it also provides shared memory and RDMA transport (based on libfabric) for high throughput, low latency applications. Moreover, FairMQ allows the single process to use multiple and different transports at the same time. FairMQ based processes can be controlled and orchestrated via different systems by implementing the corresponding plugin. However, ALFA delivers also the Dynamic Deployment System (DDS) as an independent set of utilities and interfaces, providing a dynamic distribution of different user processes on any Resource Management System (RMS) or a laptop. ALFA is already being tested and used by different experiments in different stages of data processing as it offers an easy integration of heterogeneous hardware and software