Seminars SS 19

Tue 02.04.2019, 16.30 h (28B110)

Stefano Gariazzo (IFIC Valencia)

Relic neutrinos and the PTOLEMY project

The Cosmic Neutrino Background (CNB) is a prediction of the standard cosmological model, but it has been never observed directly. Several methods of direct detection for the CNB have been proposed in the past and the most promising one is currently adopted to develop the PTOLEMY proposal. I will review some theoretical aspects of the CNB, including the calculation of the local density of relic neutrinos in the Milky Way, some proposed detection techniques and finally discuss the specific case of PTOLEMY, mostly from the point of view of perspectives in neutrino physics.


Tue 21.05.2019, 16.30 h (28B110)

Yoann Genolini (ULB, Brussels)

DM and compact objects

Due to their extreme density and low temperature, neutron stars (NS) are efficient probes to unveil interactions between standard model and dark matter (DM) particles. From elastic scatterings on NS material, DM can get gravitationally trapped by the star. The cooling of DM through further collisions may lead to the formation of a dense core which could collapse into a black hole, thus destroying the whole NS. I will show that from the observation of old NS, such a scenario leads to very stringent constraints on the parameter space of asymmetric DM, and I will detail the novelties we have introduced.


Tue 28.05.2019, 16.30 h (28B110)

Andreas Meyer (DESY)

Physics at the HL-LHC

The High-Luminosity LHC (HL-LHC) is going to start operation in 2026. Upgrades of the experiments comprise substantially improved detectors with larger acceptance, better triggers, and enhanced background suppression. Until the end of the 2030s, an integrated luminosity of 3000 fb-1 of pp data will be recorded. Based on the recent new and precise results of LHC Run-2, the expectations for the physics yield at the HL-LHC have been updated. The report of the "Workshop on the Physics at the HL-LHC and Perspectives for the HE-LHC”,  input to the European Particle Physics Strategy Update 2018-2020, covers all aspects of HL-LHC physics. In my talk, I am presenting a selection of highlights.


Tue 18.06.2019, 16.30 h (28B110)

Belina von Krosigk (TRIUMF, Vancouver)

Searches for Dark Sector Particles with SuperCDMS SNOLAB

The Super Cryogenic Dark Matter Search (SuperCDMS) is a direct Dark Matter search experiment designed to observe nuclear recoils induced by WIMPs. However, it is also sensitive to Dark Matter particle candidates beyond the standard WIMP paradigm, which could create electron recoil signals in the cryogenic silicon and germanium detectors. The pool of candidates is rich and includes Dark Photons, ALPs (axion-like particles) and LDM (light Dark Matter) particles. Lacking knowledge of the particles that constitute the dark sector of the Universe it is essential to make the search for them as broad as possible. This talk will give an overview of the versatile dark sector particle search strategies at the upcoming SuperCDMS SNOLAB experiment and will highlight first results with R&D devices as well as the expected science reach of selected searches.


Tue 25.06.2019, 16.30 h (28B110)

Dietrich Bödeker (Uni Bielefeld)


I present a brief introduction to finite temperature quantum field theory, in particular for Quantum Chromodynamics (QCD). Applications in cosmology, like the effect on gravitational waves, the production of dark matter and of the matter-antimatter asymmetry are discussed.


Tue 09.07.2019, 16.30 h (28B110)

Felice Pantaleo (CERN)

Towards a heterogenous computing farm for the CMS High Level Trigger

To fully exploit the physics reach of the High-Luminosity Large Hadron Collider, the LHC experiments are planning substantial upgrades of their detector technologies and increases of their data acquisition rates. Studies are ongoing to develop the Future Circular Collider (FCC) trigger and data acquisition infrastructure, which will have even higher requirements. The higher proton-proton interaction rate, pileup and event processing rate present an unprecedented challenge to the real-time and offline event reconstruction, requiring a processing power which is orders of magnitude larger than today. This exceeds by far the expected increase in processing power for conventional CPUs (at a fixed cost), demanding an alternative approach.
In recent years, Industry and High-Performance Computing centres have been successfully using heterogeneous computing platforms to achieve higher throughput and better energy efficiency, combining traditional processors with dedicated accelerators and matching each task to the most appropriate architecture.
The speaker will present the implications of the higher luminosity, pileup and event complexity for the trigger and data acquisition system of the Compact Muon Solenoid (CMS) experiment, and discuss the possibility of addressing them by employing a heterogeneous computing architecture. The speaker will also describe the main differences in the hardware and programming models between traditional CPUs and a widespread type of accelerator, general purpose GPUs, and discuss how they can be used together to explot their potential.
Finally, the speaker will present the Patatrack project, an incubator for R&D activities within the CMS collaboration aiming to use a heterogenous computing farm during the upcoming Run 3 (2021-2023), with the goal to improve the physics reach of the experiment and gain the necessary expertise in view of a wider deployment during the High-Luminosity runs at the LHC.


Di. 19.11.2019 16:30 (28B110)


Michal Bluj (Warsaw)

Testing CP structure of Higgs couplings at LHC

Violation of the CP symmetry is one of the Sakharov conditions required to explain the baryon asymmetry observed in Universe. Although the CP violation is already built in the Standard Model via quark mixing, its strength is not sufficient to explain the magnitude of the observed baryon asymmetry. This motivates searches for new sources of CP violation in the Higgs sector.


Tue 15.10.2019, 16.30 h (28B110)

Kumiko Kotera (Paris)

The Giant Radio Array for Neutrino Detection

The Giant Radio Array for Neutrino DetectionAbstract: The Giant Radio Array for Neutrino Detection (GRAND) project aims to detect ultra-high-energy cosmic neutrinos, cosmic rays, and gamma rays with a radio antenna array deployed over a total area of 200000 km2 in mountainous regions, in several favorable locations around the world. The strategy of GRAND is to detect air showers above 10^17 eV that are induced by the interaction of high-energy particles in the atmosphere or in the Earth crust, through its associated coherent radio-emission in the 50-200 MHz range. In its final configuration, GRAND plans to reach a sensitivity of ~10-10 GeV cm-2 s-1 sr-1 above 5*1017 eV and a sub-degree angular resolution. The 300-antenna pathfinder array, GRANDProto300 is planned to be deployed in 2021. It aims at demonstrating autonomous radio detection of inclined air-showers, and make measurements of the composition and the muon content of cosmic rays around the ankle energy. In this talk, we will show preliminary designs and simulation results, plans for the ongoing, staged approach to construction, and the rich research program made possible by the proposed sensitivity and angular resolution.


Tue 23.06.2020, 16.30 h (Zoom)

Steffen Schumann (Universität Göttingen)

The art of combining matrix elements and QCD parton showers


I will discuss concepts and techniques used for the matching  and merging of next-to-leading order hard-scattering matrix  elements with QCD parton showers in modern Monte Carlo  event generators. Furthermore, recent developments to also  include next-to-leading order electroweak corrections will be  highlighted.

Host: Robert Harlander


Tue 26.05.2020, 16.30 h (Zoom)

Andreas Hinzmann (Hamburg University)

From raw data to published experimental results at the LHC



The collider experiments at the LHC are among the most complex particle detectors ever built and operated. Likewise, the process of analysing the raw data collected by these experiments to publish results on fundamental interactions of elementary particles is as complex as the detectors themselves. It required algorithm development for more than a decade. This talk gives a basic overview of the most important aspects of data reconstruction, calibration and analysis necessary for the study of fundamental interactions, taking as example the process of analysing raw data collected by the CMS experiment and covering state of the art techniques.

Host: Alexander Schmidt



Tue 12.05.2020, 16.30 h (Zoom)



Alexander Grohsjean (DESY)

Top quark spin: A window to new physics?


High precision measurements of the properties of elementary particles are essential to understand the Universe at smallest scales. However, they also might give us exciting insights to the largest scales of the Universe, such as the understanding of Dark Matter, and may provide an avenue to physics beyond the Standard Model (BSM). The analysis of observables with small systematic uncertainties in the phase space region of new physics are of particular interest.

In this talk, the first measurement of the full ttbar spin density matrix at the CMS experiment in proton-proton scattering at the Large Hadron Collider is presented. The general analysis concept and its application in the quest for BSM physics are highlighted. The measurement provides an important answer to an anomaly observed at ATLAS in 2018 and is used to constrain anomalous couplings in an Effective Field Theory framework with greatest sensitivity. It will also be shown how the tt spin density matrix can be utilized to enhance the sensitivity in searches for new scalar particles and how this could shed light on the nature of Dark Matter.


Tue 03.12.2019, 16.30 h (28B110)

Sascha Caron (Radboud University, Nikhef)

Expanding the search for new physics via data-derived signal regions, automatisation and machine learning


Tue 21.01.2020, 16.30 h (28B110)


Peter Fackeldey (RWTH)

Higgs pair production status at LHC (Run II)

The measurement of the di-Higgs boson production is a direct test of the electroweak symmetry breaking in the standard model of particle physics (SM). The coupling strength between three Higgs bosons (self-coupling) determines the shape of the Higgs potential and thus the vacuum stability of the universe. The current Run II status of ATLAS and CMS is presented with results interpreted in non-resonant (SM) and resonant (BSM) Higgs pair production.


Tue 14.01.2020, 16.30 h (28B110)


Dirk Krücker (DESY Hamburg)

The modern Times of HEP Analysis

Deep Learning and the common data science tools have fundamentally changed the style of data analysis in High Energy Physics. The latest b-quark taggers used by the CMS experiment at the LHC are large Neural Networks and many of the legacy Run II publication on searches for New Physics will use Machine Learning. The talks introduces the use of Neural Nets in CMS with examples from b-jet tagging and searches for Supersymmetry.


Tue 17.12.2019, 16.30 h (28B110)

Matthias Schröder (KIT)

The Higgs Boson at the Top: ttH Status and Future

In the Standard Model (SM) of particle physics, the Higgs boson is deeply related to the mechanism that creates the masses of the elementary particles. A precise measurement of the Higgs boson properties and couplings offers a unique probe of this mechanism, and thus, plays a crucial role in testing the predictions of the SM and discovering potential new physics.
The coupling of the Higgs boson to the heaviest known quark, the top quark, is particularly exciting, as it is large, and therefore, has a strong impact on the consistency of the SM as well as on many new physics models. The best direct measurement of the top-Higgs coupling is achieved at the LHC in proton-proton collision events where a top quark-antiquark pair is produced in association with a Higgs boson (ttH production).
In the presentation, the first observation of the ttH production by the CMS experiment in 2018, which was achieved by combining analyses in several decay channels of the Higgs boson, will be reviewed, and an overview of the current status will be presented. As an example, a recent result in the bb decay channel of the Higgs boson will be highlighted, which establishes evidence for ttH production in this channel alone. The analysis benefits from a larger dataset, improvements of the CMS detector, as well as refined analysis methods exploiting advanced machine-learning techniques. Finally, prospects for future ttH measurements at the LHC and beyond will be discussed.