23 MAY 2022
11:00 - 12:00

A search for flavor-changing neutral current interactions of the top quark (t) and the Higgs boson (H) is presented. The search is based on a data sample corresponding to an integrated luminosity of 137 fb−1 recorded by the CMS experiment at the LHC in proton-proton collisions at 13 TeV. Events containing exactly one lepton (muon or electron) and at least three jets, among which at least two are identified as originating from the hadronization of a bottom quark, are analyzed. A set of deep neural networks is used for kinematic event reconstruction, while boosted decision trees distinguish the signal from the background events. No significant excess over the background predictions is observed, and upper limits on the signal production cross sections are extracted. These limits are interpreted in terms of top quark decay branching fractions (B) to the Higgs boson and an up (u) or a charm quark (c). Assuming one non-vanishing extra coupling at a time, the observed (expected) upper limits at 95% confidence level are B(t - Hu) < 0.079 (0.11)% and B(t - Hc) < 0.094 (0.086)%.



Based on
https://arxiv.org/abs/2112.09734

Meeting Link
https://meet.google.com/koj-tjzj-dxg


Link: https://meet.google.com/koj-tjzj-dxg

24 MAY 2022
16:30 - 18:00

I will make an overview on the theory of secant varieties to projective varieties, starting with fundamental motivations and basic tools, and focusing on some recent developments of the theory. The general pattern shows that properties of secant varieties to X are intimately related with the geometry of its configurations of points, thus with the intrinsic geometry of the variety X. The recent awareness of strong connections between the theory of secant varieties and multilinear algebra suggests several lines of investigations which involve highly sophisticated geometric tools, and poses questions on projective loci that represent a challenge for the development of Algebraic Geometry.

https://zoom.us/join
Meeting ID: 9086116889
Passcode: 362880

Email: agnt@ipm.ir

25 MAY 2022
18:00 - 19:00

There are many ways to study life, and one that is particularly appealing to physicists is regarding it as self-organized active soft matter that is away from equilibrium ``just the right way’’. In this Colloquium, I will discuss this notion, and provide a number of examples of how we can begin to put together simple systems - from basic ingredients that we fully understand - that would exhibit the kind of active behaviour we find in living systems. In particular, I will discuss the general class of chemical activity both as the source of non-equilibrium drive and the underlying mechanism for self-organization. Cells and microorganisms produce and consume all sorts of chemicals, from nutrients to signalling molecules. The same happens at the nanoscale inside cells themselves, where enzymes catalyze the production and consumption of the chemicals needed for life. In this colloquium, I will discuss a generic mechanism by which such chemically-active particles, be it cells or enzymes or engineered synthetic colloids, can "sense" each other and ultimately self-organize in a multitude of ways. A peculiarity of these chemical-mediated interactions is that they break action-reaction symmetry: for example, one particle may be repelled from a second particle, which is in turn attracted to the first one, so that it ends up "chasing" it. Such chasing interactions allow for the formation of large clusters of particles that "swim" autonomously. Regarding enzymes, we find that they can spontaneously aggregate into clusters with precisely the right composition, so that the product of one enzyme is passed on, without lack or excess, to the next enzyme in the metabolic cascade. Finally, I will discuss how breaking the action-reaction symmetry can allow a system described by two scalar fields to exhibit spontaneous breaking of time translation, time-reversal, space translation, and polar symmetries.

Link: https://www.skyroom.online/ch/schoolofphysics/colloquium

25 MAY 2022
11:00 - 12:00


In this talk, I present a detailed study to probe the bottom quark Yukawa couplings in the Standard Model (SM) effective field theory (SMEFT) approach. This study is done for the two proposed future high energy electron-proton colliders, the Large Hadron Electron Collider (LHeC) and for the Future Circular Collider (FCC-he) considering two different center-of-mass energy of 1.3 and 3.46 TeV. The signal scenario is considered to be the charged-current (CC) Higgs boson production process ep → Hjν where the Higgs boson decays to a b-quark pair. Using the Machine Learning (ML) technique, we estimate the 95% confidence level (CL) limits on the SMEFT parameters contributing to the Higgs boson production for the LHeC running at the integrated luminosity of 1 /ab, and for the FCC-he running at the integrated luminosity of 2 and 10 /ab.

Meeting Link

https://meet.google.com/zmx-jjzc-gye
https://indico.hep.ipm.ir/e/rjafari

Link: https://meet.google.com/zmx-jjzc-gye