Particle Physics in Paris

5 oct. 2017, 11:00 → 30 juin 2019, 00:00 Europe/Paris

Paris

                                                                                  

This is the website of the 2017-2018 edition. Click here for the 2019-2020 edition.

Particle Physics in Paris started in 2017 as a series of meetings aiming at gathering the particle and astro-particle physics community of the Paris area around a distinguished invited speaker. The goal of these meetings is to discuss the latest and exciting developments in the field of particle physics, exchange ideas, and start new collaborations. It is also an opportunity to get to know the new postdocs of the Paris community.

The meeting took place once a month at one of the participating institutions in turn. It starts at 2pm with a 1h seminar, a break, and then a 1h joint journal club to discuss altogether about recent interesting papers.

 

 

Organisers:

• Mathieu Boudaud
• Brando Bellazini
• Adam Falkowski
• Andreas Goudelis

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jeu. 5 octobre

11:00 → 12:00 Assessing the Higgs (self-)couplings

The Higgs self-coupling is at the heart of the hierarchy problem and it controls the fate of the electroweak vacuum. Yet, it is notoriously intangible at the LHC. First, I’ll discuss how to possibly obtain a parametrically enhanced deviation of the Higgs self-couplings compared to the Higgs couplings to the other particles, thus motivating an independent measurement. Then, I’ll show how to probe this coupling in a global fit of the Higgs data, relying in particular on the use of differential measurements in the associated single-Higgs production channels in addition to the traditional double-Higgs production channel.

Orateur: Christophe GROJEAN (DESY - Hamburg)

12:00 → 12:30 Coffee break

12:30 → 13:30 Journal club

Discussing recent papers.

mar. 14 novembre

11:00 → 12:00 Gravitational waves and the two-body problem in general relativity

The gravitational wave detectors LIGO/VIRGO have discovered the signals generated by the coalescence of compact binary systems (made of black holes or neutron stars) at astronomical distances. The theoretical and numerical works on the two-body problem in general relativity play a crucial role when deciphering and interpreting the gravitational wave signals. In this talk, after a general review on gravitational waves and the problem of motion, we shall present the state-of-the-art on approximation methods in general relativity, such as the famous post-Newtonian expansion, which is an expansion when the orbital velocity of the compact objects is small with respect to the speed of light. We shall show how important is this approximation for the GW detections, notably the recent binary neutron star event, and discuss the latest developments in the field.

Orateur: Luc BLANCHET (C.N.R.S.)

12:00 → 12:30 Coffee break

12:30 → 13:30 Journal club

"Fact Checking Dark Energy" led by Filippo Vernizzi

ven. 1 décembre

11:00 → 12:00 Sexaquark Dark Matter

There may be a so-far-undiscovered neutral, stable particle composed of 6 quarks, denoted S, with mass m_S ~ 2 m_p. If so, the S is an excellent Dark Matter candidate. I will explain why such a particle would not have been detected, propose experiments to discover it, discuss why direct detection experiments to date do not exclude it, mention some of the numerous astrophysical benefits of a DM-baryon interaction, and how it works cosmologically giving the observed DM-baryon abundance ratio and the baryon asymmetry of the Universe.

Orateur: Glennys FARRAR (CCPP - New York University)

12:00 → 12:30 Coffee break

12:30 → 13:30 Journal club

Discussing recent papers.

SDM_LPTHE_120117.pdf

mar. 16 janvier

11:00 → 12:00 In Search of Light Dark Matter

I will describe some latest theoretical and experimental results, aimed to constrain the parameter space of light dark matter particles. A new phenomenon, light dark matter reflected from the solar interior, can be used to significantly advance the sensitivity of the existing dark matter detectors to very light dark matter states.

Orateur: Maxim POSPELOV (U. of Victoria)

12:00 → 12:30 Coffee break

mar. 13 février

11:15 → 12:15 An Emergent Standard Model at the Large Hadron Collider

I will discuss how the Standard Model of particle physics can emerge consistently (in the form of an effective field theory) as the long-distance approximation of radically different theories, based possibly on strongly coupled dynamics. These broad scenarios of vector/fermion/scalar compositeness, constitute the primary target for precision tests of the Standard Model, performed at the LHC. I discuss the implications of interesting BSM-SM non-interference rules, that can be simply derived using scattering amplitudes techniques, and provide an additional challenge for a precision program.

Orateur: Francesco RIVA (CERN)

12:15 → 12:45 Coffee break

12:45 → 13:45 Journal club

Discussing recent papers

mar. 13 mars

11:00 → 12:00 Nambu-Goldstone bosons: from the composite Higgs to scattering amplitudes

I will discuss recent developments in understanding the infrared structure of nonlinear sigma models. They result in universal predictions in Higgs couplings for all composite Higgs models where the Higgs arises as a pseudo-Nambu-Goldstone boson. For scattering amplitudes of Goldstone bosons, we derive the subleading single soft theorem and shed light on the mysterious extended theory of biadjoint cubic scalars recently uncovered using the Cachazo-He-Yuan representation of scattering equations.

Orateur: Ian LOW (Argonne & Northwestern U.)

Slides

12:00 → 12:30 Coffee break

12:30 → 13:00 Journal club

Discussion of possible dark matter explanations of the unexpectedly large absorption signal of 21cm photons at the cosmic dawn measured by the EDGES experiment.

http://arxiv.org/abs/1802.10094
http://arxiv.org/abs/1803.02365
http://arxiv.org/abs/1803.02804
http://arxiv.org/abs/1803.03091

ven. 4 mai

11:00 → 12:00 Signatures of Primordial Black Holes as Dark Matter

More than twenty one years ago, we predicted that massive primordial black holes (PBH) would form via the gravitational collapse of radiation and matter associated with high peaks in the spectrum of curvature fluctuations, and that they could constitute all of the dark matter today. In 2015, we predicted the clustering and mass distribution of PBH, which peaks at several Msun, and whose high-mass tails could be responsible for the seeds of all galaxies. Since then, LIGO has detected gravitational waves from at least five merger events of very massive black hole binaries. We propose that they are PBH, and predict that within a few years a less than one solar mass PBH will be detected by AdvLIGO-VIRGO, and that in 10 years, an array of GW detectors (i.e. LIGO, VIRGO, KAGRA, INDIGO, etc.) could be used to determine the mass and spin distribution of PBH dark matter with 10% accuracy. Thus, gravitational wave astronomy could be responsible for a new paradigm shift in the understanding of the nature of dark matter.

Orateur: Juan GARCÍA-BELLIDO (IFT-UAM/CSIC Madrid and TH-Division CERN)

12:00 → 12:30 Coffee break

12:30 → 13:30 Journal club

Discussing recent papers

mar. 5 juin

11:00 → 12:00 Neutron stars chirp about vacuum energy

While the current vacuum energy of the Universe is very small, in our standard cosmological picture it has been much larger at earlier epochs. We try to address the question of what are possible ways to try to experimentally verify the properties of vacuum energy in phases other than the SM vacuum. One promising direction is to look for systems where vacuum energy constitutes a non-negligible fraction of the total energy, and study the properties of those. Neutron stars could be such systems, and we discuss how to use the recent observation of neutron star mergers to try to learn about the inner core of the neutron star which may be dominated by vacuum energy.

Orateur: Csaba CSÁKI (LEPP - Cornell University)

12:00 → 12:30 Coffee break

12:30 → 13:30 Journal club

Discussing recent papers