Programm für das Wintersemester 2019/2020
Wednesdays, 13:00 Uhr s.t.
Kaffee und Tee ab 14:00 UhrOrt: Institut für Physik, Lorentz-Raum 05-127, Staudingerweg 7
|30.10.19||Verena Spatz, TU Darmstadt|
Physics Education It is a widely held view that in the field of physics education the implementation of scientific findings into instruction practice should be a critical issue, however the record of research results on genuine classroom activities is generally poor. In the seminar, a project will be presented, that aims at closing this research-practice gap. In the project, novel teaching units on the introduction to Newtonian mechanics were developed and evaluated, based on empirical studies concerning common pre-instruction ideas, which students bring along into school. Some of these ideas are appropriate, whereas many are inappropriate to build upon in physics lessons. A very popular erroneous idea about motion is that a force is needed to keep an object moving at constant velocity. This novices concept has to be changed into an experts concept, that a force is needed only to change the velocity of an object. As illustrated in this example, teaching and learning physics often requires conceptual change. Considering this, the content area itself had to be restructured and teaching materials had to be prepared to meet students learning needs. An accompanying quasi-experimental field study with grade seven classes showed a significant improvement of students conceptual understanding.
|06.11.19||Karin Schönning, Upsala University|
Many challenges in modern physics manifest themselves in the proton. Despite being known for a century, it is to this day difficult to describe properties like its mass, spin, structure, size and abundance from first principles. One strategy when you have a system you don’t fully understand, is to make a small change to the system and see how it reacts. In the case of the proton, we can replace one of the light quarks with a heavier one and thereby obtain a hyperon. Hyperons have the advantage over protons and neutrons that their spin is traceable through their weak, parity violating and thereby self-analysing decay. In this talk, I will outline how various aspects of hyperons can shed light on two of the puzzles related to the proton: the structure and the abundance. In particular, I will discuss how two recent measurement by the BESIII collaboration exploit the unique properties of hyperons and pave the way for a new generation of hyperon physics experiments.
|13.11.19||Alejandro Kievsky, INFN Pisa|
The short-range interaction between particles many times shows a strong repulsion that strongly correlated the many-body system. In the particular case of a two-body shallow state, very extended compared to the range of the interaction, the three-body system has universal behavior. There is an infinite number of states geometrically accumulated at E=0. This is the Efimov effect predicted by V. Efimov in 1970 and experimentally verified more than 25 years later. I will discuss how universal behavior emerges in strongly correlated systems as liquid drops or light nuclear systems and how this behavior propagates as the number of particle increases.
|20.11.19||Christian Weinheimer, Universität Münster|
Since the discovery of neutrino oscillation we know that neutrinos have non-zero masses, but we do not know the absolute neutrino mass scale, which is as important for cosmology as for particle physics. The direct search for a non-zero neutrino mass from endpoint spectra of weak decays is complementary to the search for neutrinoless double beta-decay and analyses of cosmological data. Today the most stringent direct limits on the neutrino mass originate from investigations of the electron energy spectra of tritium beta-decay. The next generation experiment KATRIN, the Karlsruhe Tritium Neutrino experiment, is improving the sensitivity from the tritium beta decay experiments at Mainz and Troitsk of 2 eV/c^2 by one order of magnitude probing the region relevant for structure formation in the universe. KATRIN uses a strong windowless gaseous molecular tritium source combined with a huge MAC-E-Filter as electron spectrometer. To achieve the sensitivity, KATRIN has been putting many technologies at their limits. The full 70m long setup has been successfully commissioned. From early 2019 on KATRIN is taking high statistics tritium data hunting for the neutrino mass. In this talk an introduction into the necessity to determine the neutrino mass and the status in the field will be given, followed by a detailed presentation of KATRIN and its results from the first KATRIN science run. The new results are already bringing KATRIN into the lead position of the field. In the outlook the perspectives of KATRIN for the coming years and new technologies in the field to potentially improve further the sensitivity on the neutrino mass will be presented.
|27.11.19||Javier Menéndez, Universitad de Barcelona|
The rare decay of atomic nuclei known as neutrinoless double-beta Decay is a unique process. Here, a nucleus decays by turning two neutrons into two protons, emitting two electrons without the usual balance of antineutrinos. Therefore, two particles---two electrons---are effectively created. Neutrinoless double-beta decay is the most promising attempt to test lepton number conservation in the laboratory. The observation of neutrinoless double-beta decay would proof that neutrinos are its own antiparticle, can clarify the origin of the prevalence of matter over antimatter in the universe, and determine the absolute neutrino mass. In spite of formidable experimental efforts, neutrinoless double-beta decay remains elusive, with half-live limits set over 10^25 years in some nuclei. The decay rate depends critically on the nuclear structure of the initial and final nuclei. This is encoded in the nuclear matrix element, which is key to anticipate the reach of experiments and to fully extract all physics information from a future measurement. In this PRISMA+ colloquium I will summarize the status of double-beta decay searches, and highlight recent efforts to obtain reliable nuclear matrix elements from first principles.
|11.12.19||Torben Ferber, DESY Hamburg|
Belle II in Japan is a flagship experiment at the intensity frontier that started data taking this year after massive upgrades of the accelerator and the detector. In this talk I will report on the performance of the Belle II detector and first rediscoveries with the 2019 dataset. In the second part of the talk I will give an overview about the planned Belle II physics program for the next year with a focus on searches for Dark Sectors and Long-Lived Particles.
|18.12.19||Felix Kahlhoefer, RWTH Aachen|
Over many years the experimental programme to search for dark matter has been guided by the so-called freeze-out paradigm, which assumes that interactions between the dark matter and Standard Model particles are comparable in strength to weak interactions. The non-observation of any dark matter signal has challenged this idea and led to a shift of focus towards dark matter models with even weaker interactions. At first sight, the chance of discovering such particles appears very low, but there are a number of exciting cases where potentially observable signals are predicted in spite of tiny couplings. I will present cosmological and phenomenological aspects of these models and discuss how existing and planned experiments can be used to search for such hidden particles.
|08.01.20||Cristina Lazzeroni, University Birmingham, UK|
The decay K+→π+vv ̅, with a very precisely predicted branching ratio of less than 10-10, is one of the best candidates to reveal indirect effects of new physics at the highest mass scales. The NA62 experiment at the CERN SPS is designed to measure the branching ratio of the K+→π+vv ̅ with a decay-in-flight technique. NA62 took data so far in 2016-2018. Statistics collected in 2016 allowed NA62 to reach the Standard Model sensitivity for K+→π+vv ̅, entering the domain of 10-10 single event sensitivity and showing the proof of principle of the experiment. Thanks to the statistics collected in 2017, NA62 surpasses the present best sensitivity. The preliminary result from the 2017 data set is presented. The general status of the experiment, including other recent measurements, are presented. Plans for the next data taking and for a longer term future are also discussed.
|15.01.20||Christian Fischer, Universität Gießen|
In this talk I will give an overview on recent results on the spectrum and properties of conventional baryons and 'exotic' tetraquarks as obtained in the framework of Dyson-Schwinger and Bethe-Salpeter equations. I will discuss the spectrum of light baryons with focus on the comparison with quark model expectations, the impact of dynamical mass generation and the importance of relativistic components in the wave functions of baryons. I will also discuss extensions to SU(3). For four-quark systems I will summarize results for light quarks and discuss recent progress on discriminating between tetraquark, molecule or hadro-quarkonium configurations in heavy-light systems.
|22.01.20||Assumpta Parreno, Universitad de Barcelona|
A central goal of Nuclear Physics is to obtain a first-principles description of the properties and interactions of nuclei from the underlying theory of the strong interaction, Quantum Chromodynamics (QCD). Being the theory that governs the interactions between the basic building blocks of matter, quarks and gluons, it is also responsible for confining those primary pieces into hadronic states, binding neutrons and protons through the nuclear force to give the different elements in the periodic table. Nevertheless, due to the large complexity of the quark-gluon dynamics, one cannot obtain analytical solutions of QCD in the energy regime relevant to nuclear physics. In order to address this problem, numerical solutions of QCD can be obtained in a finite volume through its formulation in a Euclidean discretized space-time. I will present the results of our study in the two-baryon sector for different values of the light quark masses, as well as for the very light A=3,4 nuclei.
|29.01.20||Jonathan Butterworth, UCL London|
Particle-level, differential measurements made in fiducial regions of phase-space at colliders have a high degree of model-independence and can therefore be compared in a very generic way not only to precision Standard Model predictions, but to beyond the Standar Model physics implemented in Monte Carlo generators. This allows a wider array of final states to be considered than is typically the case, as well as a wider array of specific models, and optimises the long-term impact of precision LHC data. I present a method of exploiting this, with examples.
Prof. Dr. Stefan Tapprogge