Seminare SS 17


Di. 16.05.2017 16:30 (28B110)

R. Thorne (UCL)

Parton Distribution Functions at the LHC

I will discuss the importance of the precise knowledge of parton distribution functions (PDFs) for high-energy physics, particularly that at the LHC. I will briefly introduce the background and the different approaches taken to obtaining the PDFs and their uncertainties, and summarise the recent developments, degree of agreement between different groups, and methods of combination of different PDF sets. I will then illustrate the manner in which PDFs and Standard Model predictions are being tested at the LHC, and the manner in which this is leading to further improvements. I will highlight particular challenges with the extreme precision now being achieved for some LHC measurements.


Di. 30.05.2017 16:30 (28B110)

S. Söldner-Rembold (University of Manchester)

Neutrino (and other) Physics with Liquid-argon Detectors

The outstanding capability of liquid-argon Time Projection Chambers to detect particle interactions make them one of the most promising technology choices for next-generation neutrino experiments. Several mid-size detectors at Fermilab and CERN will soon demonstrate the potential of the liquid-argon technology, searching for sterile neutrinos and measuring liquid-argon interactions of neutrinos and charged particles. Within a decade, the DUNE experiment in South Dakota will start to address a broad science programme, with the aim to discover CP violation in the neutrino sector, record supernova neutrinos, and search for proton decay. DUNE is the largest particle physics project undertaken world-wide since the LHC construction. I will give an overview of the current status and future discovery potential of the liquid-argon programme.


Di. 06.06.2017 16:30 (28B110)

D. Straub (TU München)

Searches for Physics beyond the Standard Model with Flavour

Processes involving flavour-changing neutral currents, like rare decays of B mesons, are strongly suppressed in the Standard Model and thus sensitive to virtual new physics effects. In recent years, several deviations from Standard Model expectations have been observed in such processes, but their interpretation in terms of new physics is complicated by the presence of hadronic uncertainties. This seminar will give an introduction to this field, its current status, main challenges, and prospects at current and future experiments.


Di. 13.06.2017 16:30 (28B110)

M. Doser (CERN)

Experiments on antimatter at CERN

Two decades after the first production of (relativistic) antihydrogen atoms, and a good decade after the first production of “cold” antihydrogen, first measurements of the properties of antihydrogen have recently begun. Together with the start-up of an additional dedicated low energy antiproton decelerator (ELENA), and the development of a wide range of techniques that permit precise atomic measurements, the study of antihydrogen atoms is set to start in earnest. This presentation will provide an overview of the present status and outlook for fundamental physics with antihydrogen atoms. A special focus will be put on the AEGIS experiment, which aims to reach a 1% precision on the gravitational interaction of antihydrogen by measuring its free fall over its parabolic trajectory, as well as on the technological developments from a variety of fields on which it relies.


Di. 20.06.2017 16:30 (28B110)

D. Lopez-Val (KIT)

Higgs portrays beyond the Standard Model

The coupling patterns and CP properties of the 126 GeV Higgs are key to address a major question brought to the fore by the ATLAS and CMS discovery - does this state indeed correspond to the agent of the electroweak symmetry breaking in exactly the form postulated by Higgs, Englert and Brout - or is rather a first footstep into the Beyond? With this goal in mind, we will show how Higgs coupling deviations would constitute telltale signatures of New Physics, and describe how these could help to portray the nature of a possible completion of the SM. We will also present strategies to probe the CP nature of novel scalar resonances that may be found in the upcoming LHC searches for extended Higgs sectors.


Di. 04.07.2017 16:30 (28B110)

W. Handley (Cambridge)

Modern Bayesian Inference: Theory and Practice

Inference is the procedure by which we define and extract information from data using scientific models. In this seminar we will cover the essential elements of the theory and practice of modern Bayesian statistics. In the context of scientific examples I shall discuss the importance of Parameter Estimation and Model Comparison. I will survey the current numerical tools and their state-of-the-art implementations: Metropolis-Hastings, Hamiltonian Monte Carlo, The MCMC Hammer and Nested Sampling.


Di. 18.07.2017 16:30 (28B110)

M. Krämer (RWTH Aachen)

Probing dark matter with cosmic ray antiprotons

We evaluate dark matter limits from cosmic-ray antiproton observations using recent AMS-02 measurements, taking into account cosmic-ray propagation uncertainties. We find a possible indication of a dark matter signal with an annihilation cross-section close to the thermal value and with masses in range between 50 and 130 GeV, depending on the annihilation channel. Furthermore, we investigate in how far the possible signal is compatible with the Galactic center gamma-ray excess and recent observation of dwarf satellite galaxies by performing a joint global fit including uncertainties in the dark matter density profile. As an example, we interpret our results in the framework of a Higgs portal model. Interpreting the AMS-02 data in terms of upper limits on hadronic DM annihilation, we obtain strong constraints excluding a thermal annihilation cross-section for DM masses below about 50 GeV and in the range between approximately 150 and 500 GeV.


Di. 25.07.2017 16:30 (28B110)

F. Krauss (Durham University)

Precision Simulations for the LHC

I review recent progress in precision simulations for the LHC, with special emphasis on parton showering.