GK Seminars SS 15

Tue 14.04.2015, 16.30 h

A. Pich (IFIC Valencia)

Flavour & Electroweak Symmetry Breaking

Although the scalar boson discovered at the LHC has the properties expected for a Higgs-like particle, more precise data are needed to clarify whether it is the unique Higgs boson of the Standard Model or the first member of a new variety of dynamical fields. Alternative scenarios of electroweak symmetry breaking with extended scalar sectors are strongly constrained by experimental data on flavour-changing phenomena: generic flavour structures are not allowed at the TeV scale. The highly non-generic flavour structure of viable multi-Higgs models will be illustrated in the simpler case of two scalar doublets. The present phenomenological constraints on this type of models and the prospects for the next LHC run will be discussed.


Tue 21.04.2015, 16.30 h

T. Flacke (KAIST Daejeon)

Search Strategies for Composite Higgs Models at LHC run II

Composite Higgs Models provide an attractive extension of the Standard Model which solves the hierarchy problem and predicts new resonances at the TeV scale which can be observed at the LHC run II. In most composite models, the new resonances include colored top partner states. In this seminar, we present results on several new search strategies for such heavy vector-like quark partners at the early stages of the LHC run-II. In particular, we show that identifying tops, Z and W bosons, and higgses with very high momenta are the key to heavy quark partner searches and how jet-substructure techniques can maximize the sensitivity to such signatures.


Tue 28.04.2015, 16.30 h

T. Flacke (KAIST Daejeon)

Searching for Universal Extra Dimensions at Colliders and in the Sky

In models with Universal Extra Dimensions (UED), all Standard Model fields are promoted to five dimensional fields which also propagate in a flat, compact extra dimension. The effective field theory arising from UED models contains the Standard Model fields, and associated to each of them also a tower of Kaluza-Klein excitations with identical quantum numbers but higher masses. The Kaluza-Klein excitations represent particles which can be detected at the LHC. Also, the lightest Kaluza-Klein particle is stable, such that UED models  provide a viable dark matter candidate. In this talk, I will give an overview on the minimal UED model and its extensions and summarize the current status of searches for UED at colliders as well as for UED dark matter.


Tue 19.05.2015, 16.30 h

P. Salati (LAPTh Annecy)

The relation between dark matter and cosmic rays

An essential component of the Universe, the so-called dark matter, could be made of massive and weakly interacting particles, dubbed WIMPs. These species are predicted in most of the extensions of the Standard Model. They are actively searched at the LHC, where their production is eagerly awaited during the second run of the machine.
WIMPs are also expected to pervade the halo of the Milky Way where they should annihilate, producing positrons and antiprotons. As these antimatter cosmic rays are rare, they potentially provide an indirect signature for dark matter under the form of spectral distortions in the fluxes detected at Earth. However, before interpreting any positron or antiproton excess as evidence for the presence of WIMPs in the heavens, the astrophysical backgrounds to these signals must be carefully investigated.
In particular, the transport of charged particles within the Galactic magnetic fields must be modeled, hence the connection between cosmic rays and dark matter searches. I will review how cosmic rays propagate and what probes such as the boron-to-carbon ratio can tell us. I will then discuss the positron excess and why it cannot be attributed to dark matter. Finally, I will comment about a recent press release from the AMS collaboration where a high-energy antiproton excess is reported.


Tue 02.06.2015, 16.30 h

G. Dissertori (ETH Zürich)

The LHC experiments

In this presentation I will highlight the main criteria, which formed the basis for the original designs of the ATLAS and CMS detectors, and then show how the achieved detector performance allowed to produce such a rich and high-quality output in terms of physics results during Run1 of the LHC. Finally, a short outlook to the upcoming Run 2 will be given.


Tue 09.06.2015, 16.30 h

D. Lhuillier (CEA Saclay)

The reactor neutrino spectrum and the reactor anomaly


Tue 23.06.2015, 16.30 h

J. Goodman (U. of Maryland)

High Energy Gamma Astronomy with the High Altitude Water Cherenkov Observatory (HAWC)

HAWC is a second generation wide-field TeV gamma-ray observatory. HAWC has just been completed in the high mountains of Mexico at 4100m a.s.l. The modularity of the detector enabled us to begin taking science data with a detector that was significantly more sensitive than previous instruments even while the detector was under construction. This talk will describe the science goals of the project, the current status of the detector and present science results from operations with the partially completed detector.


Tue 14.07.2015, 16.30 h

L. Baudis (Zuerich)

Searching for dark matter with XENON and DARWIN


Cosmological observations and the dynamics of the Milky Way provide strong evidence for an invisible and dominant mass component, that so far reveals its presence only by its gravitational interaction. If the dark matter is made of Weakly Interacting Massive Particles (WIMPs), it can be directly detected via elastic scattering from nuclei in ultra-low background, deep-underground detectors. Among these, detectors based on liquefied noble gases feature an excellent sensitivity over a wide range of WIMP masses, and thus a large discovery potential. After a brief introduction to the direct dark matter detection method, I will discuss the XENON100 detector, its most recent results, and present the prospects for XENON1T, which is under construction at the Gran Sasso Underground Laboratory in Italy. I will end by introducing DARWIN, an R&D and design study for a next-generation, multi-ton dark matter detector.