In this project, an algorithm has been implemented in Python to estimate the parameters describing the production and decay of a spin 1/2 baryon - antibaryon pair. This decay can give clues about a fundamental asymmetry between matter and antimatter. A model-independent formalism developed by the Uppsala hadron physics group and previously implemented in C++, has been shown to be a promising tool in the search for physics beyond the Standard Model (SM) of particle physics. The program developed in this work provides a more user-friendly alternative, and is intended to motivate further use of the formalism through a more maintainable, customizable and readable implementation. The hope is that this will expedite future research in the area of charge parity (CP)-violation and eventually lead to answers to questions such as why the universe consists of matter. A Monte-Carlo integrator is used for normalization and a Python library for function minimization. The program returns an estimation of the physics parameters including error estimation. Tests of statistical properties of the estimator, such as consistency and bias, have been performed. To speed up the implementation, the Just-In-Time compiler Numba has been employed which resulted in a speed increase of a factor 400 compared to plain Python code.

No description available.

Freiburg i. Br., Univ., Diss., 2007.

Das Kuehlersynchrotron COSY im Forschungszentrum Juelich kann u.a. einen guten Protonenstrahl fuer Experimente zur Verfuegung stellen. An einem der Experimentierplaetze steht das Flugzeitspektrometer COSY-TOF. Es eignet sich hervorragend zur Untersuchung von Reaktionen, bei denen wenige Teilchen enstehen. Solange die entstehenden Teilchen einen Winkel von hoechstens 70 Grad mit Strahlachse einschliessen, werden diese nachgewiesen. Damit sind im schwellennahen Energiebereich die Flugzeit und Flugrichtung aller langlebigen Teilchen bestimmbar. Zum Nachweis kurzlebiger Teilchen gibt es einige Module im Flugzeitspektrometer zur Rekonstruktion der Flugrichtung. Die Arbeit untersucht zwei Reaktionen, bei denen Hyperonen entstehen: pp-->nK+Sigma+ und pp--> pK0Sigma+ bei einem Strahlimpuls von 2,95 GeV/c. Im schwellennahen Energiebereich liegen bisher keine (in Zeitschriften) veroeffentlichten Daten vor. Die Kenntnis der Reaktionsmechanismen sind jedoch wuenschenswert, um die physikalsiche Beschreibung in vielen Bereichen zu verbessern. Dazu gehoeren die Eigenschaften der Teilchen (Strangenessgehalt des Nukleons) und die Wechselwirkungen zwischen den Teilchen (auch in extrem dichter Materie). In dieser Arbeit werden die zur Kalibrierung des Detektors notwendigen Schritte, die vom Autor durchgefuehrt wurden, erlaeutert. Im Anschluss wird die Analyse der Daten fuer ein Experiment ausfuehrlich vorgestellt. Durch einige Bedingungen wird erreicht, dass eine (nahezu) untergrundfreie Menge der gesuchten Ereignissen vorliegt. Die Anzahl der gefundenen Ereignisse laesst fuer die Reaktion pp--> nK+Sigma+ nur die Angabe eines totalen Wirkungsquerschnittes zu. Fuer die Reaktion pp--> pK0Sigma+ wird ebenfalls der totale Wirkungsquerschnitt bestimmt. Weiterhin werden Untersuchungen zum Reaktionsmechanismus durchgefuehrt. Dadurch wird ersichtlich, dass diese Reaktion einen starken resonanten Anteil im K0Sigma-System hat. Die Analyse wird auch auf zwei andere Experimente mit COSY-TOF angewendet. Das Auftreten hoeherer Drehimpulse ist erst bei groesseren Strahlimpulsen 3,2 GeV/c zu erkennen.

The goal of this project was to develop a lightweight Monte-Carlo (MC) event generator for hyperon pair production in antiproton-proton collisions, and demonstrate it in one of the hyperon decay reaction channels, which is collisions of proton and antiproton to lambda hyperon and anti-lambda hyperon, and they decay to antiproton-positive pion pair, and proton-negative pion pair. The prototype of this external MC event generator we presented here is based on the software framework of ROOT. Compared to the corresponding framework of embedded MC event generators that is currently used in the PANDA experiment at FAIR, PandaRoot, it allows for easier and quicker testing of new models or formalisms on synthetic data, for example for studying spin observables like polarisation. The event generator was benchmarked by studying angular distributions in final states, which are constructed by kinematic relations of 4-momentum vectors in different reference frames for all mother and daughter particles.

The PANDA experiment at FAIR is an antiproton experiment and it will offer unique possibilities for the study of hadron physics including hyperon physics. With the PANDA detector, it will be possible to exclusively reconstruct hyperon-antihyperon events. Hyperons are relatively long-lived particles (10−10s), which can travel for a distance of up to a few meters before decaying into their reconstructible decay products. In this project, I focus on the reaction p̅ p → Ξ̄+ Ξ− → Λ̅ π+ Λ π− → p̅ π+π+ p π− π−. The Ξ− (cascade) hyperons take a special role as they are the lightest hyperons to introduce a sequential decay topology, i.e., Ξ− → Λ π− → p π− π− (and c.c.). This constitutes a substantial challenge for the reconstruction algorithms. In this thesis, a Monte-Carlo simulation study of realistic track and event reconstruction of this Ξ̄+ Ξ− reaction in the region near the production threshold is done, and the event generation of the Ξ̄+ Ξ− reaction channel was performed by the EvtGen event generator in PandaRoot. For various realistic tracking algorithms, track and event reconstruction performance levels were investigated in PandaRoot.

No description available.

<p>Spin-orbit interactions cause a global polarization [P] of Lambda (anti-Lambda) hyperons with the vorticity (or total angular momentum) in the participant collision zone. The strong magnetic field mainly created by the spectator protons would split the Lambda and anti-Lambda global polarization [Delta P]. Quantum chromodynamics (QCD) predicts topological charge fluctuation in vacuum, resulting in a chirality imbalance, or parity violation in a local domain. This would give rise to an imbalanced left- and right-handed Lambda (anti-Lambda) [Delta n], as well as a charge separation along the magnetic field, referred to as the chiral magnetic effect (CME). The latter can be characterized by the parity-even [Delta gamma] and parity-odd [Delta a1] observables. While measurements of the individual [Delta P], [Delta gamma], and [Delta a1] have not led to affirmative conclusions on the CME or the magnetic field, correlations among these observables may reveal new insights. We report exploratory measurements of event-by-event correlations between [Delta P] and [Delta gamma], and between [Delta n] and [Delta a1] by the STAR experiment in Au+Au collisions at 27 GeV. No correlations have been observed beyond statistical fluctuations. Future endeavor would be to extract an upper limit from the data as well as to apply the correlation analysis to other data samples.</p>

To learn more about the structure of hadrons we study form factors. In the semi-leptonic decay Ω- → Ξ0W- two types of form factors arise namely the vector and axial-vector transition form factors. We focus on the vector transition form factors at next-to-next-to-leading order in the power counting of chiral perturbation theory and study their quark mass dependence. They are related to the scattering amplitude for the transition and therefore we have to calculate Feynman diagrams. Next-to-next-to-leading order Feynman diagrams translate to 1-loop diagrams and at this order there is a substantial amount of them. This study is a feasibility study and therefore we limit this study to diagrams containing the low-energy constants HA and hA from the leading order chiral Lagrangian. There are 5 such diagrams, three with two propagators in the loop (bubble diagrams) and two with three propagators in the loop (triangle diagrams). We derive explicit expressions for all 5 diagrams. To calculate these diagrams numerically we use Mathematica and FeynCalc. We provide numerical results for the three bubble diagrams but not the triangle diagrams due to the long computing time for these diagrams. Therefore, we show that performing form factor calculations at NNLO seems feasible but there needs to be more investment into figuring out the coding aspects regarding the triangle diagrams.

Les étoiles à neutrons sont parmi les objets les plus extrêmes dans l'univers. Elles sont des étoiles compactes, nées à la suite d'une explosion de supernova gravitationnelle, au point final de l'évolution stellaire. Le champ gravitationnel y est très fort, et la matière à l'intérieur atteint des densités extrêmement élevées. Elles sont donc des "laboratoires" prometteurs, non seulement pour tester le régime de champ fort en relativité générale, mais aussi pour en apprendre davantage sur la physique nucléaire à haute densité, qui actuellement ne peut pas être reproduit avec des expériences terrestres. Ainsi, les étoiles à neutrons nous permettent d'adresser des questions telles que l'existence éventuelle de particules autres que nucléons à haute-densité. À cause de la naissance violente de ces objets, les étoiles à neutrons très jeunes, que l'on appelle proto-étoiles à neutrons, sont également très chaudes, et souvent en rotation différentielle rapide. Dans cette thèse nous avons pour but de développer un modèle stationnaire d'une telle proto-étoile à neutrons.Ainsi, nous présentons une nouvelle méthode pour calculer numériquement les équations d'équilibre d'un fluide parfait relativiste, axisymétrique et stationnaire, en rotation différentielle et à température finie, valable pour une équation d'état réaliste. Nous présentons en détail le code (accessible au public) développé. Nous avons appliqué ce code avec des nouvelles équations d'état réalistes à température finie, basée sur une théorie relativiste du champ moyen, en incluant tous les degrés de liberté hyperoniques. Nous avons calculé des modèles relativistes stationnaires de proto-étoiles à neutrons en rotation différentielle rapide. Nous allons discuter les applications de nos modèles pour explorer plus en détail la physique de ces objets. / Neutron stars are among the most extreme objects in the universe. They are compact stars born as the aftermath of a core-collapse supernova explosion, at the endpoint of stellar evolution, with a strong gravitational field, and extremely high densities. They are therefore promising 'laboratories', not only to test the strong-field regime of general relativity, but also to learn about nuclear physics in the high density regime, which presently is not accessible in earth based experiments. This allows to address questions such as the possible existence of particles other than nucleons at high-densities. As a consequence of the violent birth of these objects, new-born (proto-)neutron stars are extremely hot and, in general, rapidly rotating, which raises interesting problems in the task of developing a stationary model of such objects.In this thesis, we present a new self-consistent method to numerically compute the equilibrium equations of stationary axisymmetric relativistic (differentially) rotating perfect fluids at finite temperature, with a realistic equation of state. We introduce in detail the (publicly available) code in which we implemented the described numerical scheme. We use newly developed realistic equations of state with finite temperature, which are based on density dependent relativistic mean field theory, and in which all hyperonic degrees of freedom are included, to compute realistic stationary relativistic models of rapidly differentially rotating proto-neutron stars. We discuss future applications of our code for further exploring the physics of proto-neutron stars.