Pandemics, like COVID-19, are becoming a recurring threat to our global society. Surprisingly, high energy physics can help us understand how the dynamics of the virus spreading works. The epidemic Renormalisation Group approach provides simple models, which can be used to predict incurring waves of infections, as demonstrated for the second wave in Europe. Finally, models
with strolling dynamics can shed light on how infection waves arise, and help us prevent them. 

Informal journal club meeting about the following paper:

Search for phenomena beyond the Standard Model in events with largeb-jet multiplicity using the ATLAS detector at the LHC

A search is presented for new phenomena in events characterised by high jet multiplicity, no leptons (electrons or muons), and four or more jets originating from the fragmentation of b-quarks (b-jets). The search uses 139 fb−1 of s√ = 13 TeV proton-proton collision data collected by the ATLAS experiment at the Large Hadron Collider during Run 2. The dominant Standard Model background originates from multijet production and is estimated using a data-driven technique based on an extrapolation from events with low b-jet multiplicity to the high b-jet multiplicities used in the search. No significant excess over the Standard Model expectation is observed and 95% confidence-level limits that constrain simplified models of R-parity-violating supersymmetry are determined. The exclusion limits reach 950 GeV in top-squark mass in the models considered.

Due to the special role of the top quark in many beyond-standard models, the study of the different top-quark production modes is an important area of research to find evidence for new physics at the LHC. Recently, the ATLAS collaboration claimed a strong evidence for the production of four top quarks with a measured cross section that is twice the standard-model prediction. In this seminar, I will present the sophisticated techniques that were used to overcome the analysis challenge for such a rare and complicated process. The robustness of the result and its compatibility with the standard-model prediction will also be discussed.

Lien zoom: https://univ-amu-fr.zoom.us/j/96100395873?pwd=SnFGUmRObGFEYTJhblNja0pLV0lMZz09
ID de réunion : 961 0039 5873
Code: CPPM

With the lowest background level ever reached by a liquid xenon time
projection chamber, XENON1T proved to be the most sensitive WIMP dark
matter direct detection experiment on earth. Despite being primarily
designed to search for nuclear recoils between WIMPs and xenon atoms,
the unprecedented low electron recoil background of 76 ± 2 stat
events/(tonne × year × keV) between 1–30 keV, made the XENON1T
experiment suitable also to explore new parameter space for
electronic-recoil channels.
In this talk, I will review the XENON1T detection principles before
focusing on the recently observed electronic recoil excess in the (1 -
7) keV region. I will discuss the different interpretations of this
excess, provide details on the analysis, and cross-checks of our results.

Lien zoom: https://univ-amu-fr.zoom.us/j/96100395873?pwd=SnFGUmRObGFEYTJhblNja0pLV0lMZz09
ID de réunion : 961 0039 5873
Code: CPPM

Axions are a low mass dark matter candidate which arise from
the Peccei Quinn solution to the Strong CP problem. Axions are
predicted to have a coupling to the Standard Model photon which is
exploited in the haloscope search technique. ADMX was the first
experiment to use a haloscope to exclude the full range of axion-photon
coupling values predicted in benchmark models of the axion that
solve the Strong CP, covering the mass range of 2.66 - 3.31 μ eV. In this
presentation we will discuss the axion, the experimental
innovations which enabled this result and the future of the ADMX.

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Topic: CPPM Seminar
Time: Jun 22, 2020 04:00 PM Paris

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