I will start reviewing one of the main open questions in physics: why the expansion of the Universe is accelerating? Making precise maps of the structures of the Universe, as a function of time, can help us answer this question. I will present how we can learn about dark energy from these maps, in particular focusing on the state-of-the-art results from the extended Baryon Oscillation Spectroscopic Survey (eBOSS), published in 2020. I will finish by exposing the goals of next-generation surveys of our cosmic structures.

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

The LHCb and Belle II experiments explore phenomena in quark-flavour physics
at unprecedented precision and extend studies to ever rarer decays to test
the Standard Model (SM) of particle physics and search for nonstandard signals.
Since some years now, tensions with the SM have been observed, also known as
"B-physics anomalies". We will give an introduction to the field and discuss
the status, what has been learned so far and what we would like to know in
the future.
 

Zoom link:

https://cern.zoom.us/j/91966246292?pwd=UHRZVmN0UmNJbzNqVmhpcUhYY1VXUT09

In recent years, tensions between measurements and Standard Model predictions in the decays of b-hadrons have hinted at the possible violation of lepton universality, specifically in observables in b→sll and b→clυ transitions. Among them is the ratio of branching fractions R(D*)τμ = B→ D*τυ/ B→ D*μυ. I will discuss the first measurement of the ratio R(D*)eμ = B→ D*eυ / B→ D*μυ at the LHCb experiment at CERN, which will lead towards a combined measurement of all three lepton species in the future.

The LHCb experiment is currently being upgraded for Run 3 of the LHC to record more statistics and therefore reduce the uncertainties of observables testing for example lepton flavor universality. After this upgrade, LHCb will run without a hardware level trigger, resulting in the complete detector being read out at the full bunch-crossing rate of 30 MHz and a maximum data rate of 40 Tbit/s. Events of interest are selected with a software-only trigger in two stages. This allows unprecedented flexibility for trigger selections but at the same time poses a significant computing challenge.

In this seminar, I will also present the first complete high throughput trigger implemented entirely on graphics processing units (GPUs) for an HEP experiment. In LHCb’s High Level Trigger 1 (HLT1) charged particle trajectories and decay vertices are reconstructed to select pp-collisions of interest and reduce the event rate by a factor 30-60. The full HLT1 will be processed on about 200 state of the art GPUs from 2022 onwards. I will discuss the software framework, reconstruction algorithms and performance of the GPU HLT1, as well as ongoing developments towards commissioning.

T2K is an accelerator based long baseline neutrino oscillation experiment taking data since 2010 in Japan. The neutrino beam is produced at the J-PARC accelerator complex and neutrinos are detected in a Near Detector complex (ND280) before the oscillations and at the Far Detector (Super-Kamiokande) after the oscillations. 
T2K was the first experiment to measure oscillations in the appearance channel and, as it will be shown in this seminar, is now observing first hints of CP violation in the leptonic sector by comparing appearance probabilities of electron neutrinos and antineutrinos. 

Such hints are currently limited by statistical uncertainties and T2K is now entering its second phase (T2K-II) consisting in an upgrade of the accelerator complex and of ND280. Such upgrades are expected to be operational in 2022 and will allow to establish CP violation at more than 3 sigma with T2K-II if CP is maximally violated in neutrino oscillations. 
T2K-II will be followed by Hyper-K, a Water Cherenkov detector 8 times larger than Super-K. Hyper-K will use the same accelerator complex and near detectors of T2K and it is expected to start data taking in 2027.  
Thanks to its large size, Hyper-K will have unprecedented sensitivity to CP violation and to the proton decay and it will be a powerful observatory for atmospheric and solar neutrinos and for neutrinos emitted in supernovae explosions.

Millisecond pulsars are rapidly rotating neutron stars with phenomenal rotational stability. The NANOGrav collaboration monitors an array of about 80 of these cosmic clocks in order to detect perturbations due to gravitational waves at nanohertz frequencies. These gravitational waves will most likely result from an ensemble of supermassive black hole binaries. Their detection and subsequent study will offer unique insights into galaxy growth and evolution over cosmic time. I will present our most recent dataset and the results of our gravitational wave analysis, which suggests the presence of a common signature in the data that could be the first hints of a gravitational wave background. I will then describe the gains in sensitivity that are expected from additional data, discoveries of millisecond pulsars, more sensitive instrumentation, and international collaboration and discuss prospects for detection in the next several years.

Observations of the cosmic microwave background (CMB) have played a critical role in establishing the current cosmological concordance model. Next generation CMB experiments promise to go even further, and image the very birth of the universe by observing primordial gravitational waves created during the Big Bang. However, observing this signal will be a tremendous challenge, as the expected signal can easy be contaminated by systematic uncertainties both from confusing radiation from the Milky Way and from instrumental imperfections. In this talk, I will describe the BeyondPlanck project, which developed the world's first end-to-end Bayesian CMB analysis code, accounting for both instrumental and astrophysical uncertainties, and applied this to the Planck LFI data set. I will argue that this approach not only sets a new standard for CMB analysis, but also that the main ideas are applicable to any experiment for which systematic error propagation is the main limiting factor.

Lien zoom: https://univ-amu-fr.zoom.us/j/96100395873?pwd=SnFGUmRObGFEYTJhblNja0pLV0lMZz09

This CPPM seminar is part of our series of talks from the CPPM 3rd year PhD students.
It will be happening remotely on zoom:

https://cern.zoom.us/j/98884149890?pwd=ZGVSNlE5RlJNUVk5MUgvVXhBdU9Gdz09

Meeting ID: 988 8414 9890

Passcode: 758510

By phone: Find your local number: https://cern.zoom.us/u/ad6uXVcoCT

This CPPM seminar is part of our series of talks from the CPPM 3rd year PhD students.
It will be happening remotely on zoom:

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

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. 

Note that the talk has been recorded and is available in the link below