17 SEP 2024
14:00 - 15:00

Abstract
Weakly- and Feebly-Interacting Massive Particles (WIMPs and FIMPs) are among the best-motivated dark matter (DM) candidates. In this paper, we investigate the production of DM through the WIMP and FIMP mechanisms during inflationary reheating. We show that the details of the reheating, such as the inflaton potential and the reheating temperature, have a strong impact on the genesis of DM. The strong entropy injection caused by the inflaton decay has to be compensated by a reduction of the portal coupling in the case of WIMPs, or by an increase in the case of FIMPs. We pinpoint the smooth transition between the WIMP and the FIMP regimes in the case of low reheating temperature. As an example, we perform a full numerical analysis of the singlet-scalar DM model; however, our results are generic and adaptable to other particle DM candidates. Interestingly, in the singlet-scalar DM model with low-reheating temperature, regions favored by the FIMP mechanism are already being tested by direct detection experiments such as LZ and XENONnT.

Date and time
Tuesday, September 17th, 2024 (Shahrivar 27th, 1403), 2:00 pm (Tehran zone)

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

16 SEP 2024
11:00 - 12:00

Abstract:

Preserving the phase space quality has been of crucial importance to high-brightness electron beam transport. Any driving source of beam performance limitations in such a transport system must be carefully examined in order to preserve the beam phase space quality. It is found that in the low beam energy, high bunch charge regime, space charge effect on the charged particle beam evolution can be complicated. It may be insufficient to analyze the beam properties through the envelope or lower order moments for the mere bulk of the beam. In this work we will study the space-charge-dominated, low-energy, high-brightness electron beam dynamics based on the slice beam matrix method. The slice beam matrix method, extended from the existing bulk beam analysis, is applicable to an arbitrary longitudinal bunch distribution and can thus take the nonlinear RF curvature into account. The semi-analytical sliced beam space charge model is constructed and assumes an axisymmetric beam in the presence of perfect conducting cylindrical pipe with circular cross section. We present in this paper the theoretical formulation, starting from single-particle dynamics, space charge field calculation, followed by the moment description of a collection of particles, based on beam sigma matrix and longitudinal slice decomposition. We prove the equivalence between the beam matrix method and the envelope formalism in the presence of space charge effect, in both the transverse and longitudinal dimensions.

Based on:
https://doi.org/10.1016/j.nima.2019.05.035

Meeting Place:
Seminar Room, School of Particles and Accelerators, IPM

Link to Join Virtually:
https://meet.google.com/bda-vsem-tuv

11 SEP 2024
14:00 - 16:00

This talk focuses on pointwise ergodic theorems and their connection to Bourgain's path to his Fields Medal. We aim to cover four key milestones:
Part One: We investigate the norm convergence of ergodic averages, concluding with an explanation of the Baby Spectral Theorem.
Part Two: We examine the pointwise ergodic theorem established by Birkhoff in 1931. Depending on the time available, we will cover at least one proof, exploring Calderon's transference in the process.
Part Three: This section delves into the circle method and its comparison to the continuous Fourier Transform. We will also discuss several properties of prime numbers and provide an approximation for averages along primes.
Part Four: We introduce the concept of oscillation and present a proof of the pointwise ergodic theorem along primes. Time permitting, we will explore further developments post-1990.

The references are uploaded in the following link:
https://drive.google.com/drive/folders/1_zIDuDybfkfYuHhrlLtwe-rd6SdpraPZ?usp=drive_link
Venue: Niavaran, Lecture Hall 1

11 SEP 2024
10:00 - 12:00

This talk focuses on pointwise ergodic theorems and their connection to Bourgain's path to his Fields Medal. We aim to cover four key milestones:
Part One: We investigate the norm convergence of ergodic averages, concluding with an explanation of the Baby Spectral Theorem.
Part Two: We examine the pointwise ergodic theorem established by Birkhoff in 1931. Depending on the time available, we will cover at least one proof, exploring Calderon's transference in the process.
Part Three: This section delves into the circle method and its comparison to the continuous Fourier Transform. We will also discuss several properties of prime numbers and provide an approximation for averages along primes.
Part Four: We introduce the concept of oscillation and present a proof of the pointwise ergodic theorem along primes. Time permitting, we will explore further developments post-1990.

The references are uploaded in the following link:
https://drive.google.com/drive/folders/1_zIDuDybfkfYuHhrlLtwe-rd6SdpraPZ?usp=drive_link
Venue: Niavaran, Lecture Hall 1

11 SEP 2024
11:00 - 12:00

Abstract:

In the Standard Model (SM) of particle physics, gluons are the fundamental particles mediating the strong interaction, as photons do in electromagnetic interactions. Gluons can attract each other to form new bound states called glueballs, which are the only particles in nature entirely composed of force mediators. Finding these gluon bound states is crucial and serves as a fundamental test of the SM. No candidate has yet been unambiguously identified until the new BESIII result to be reported in this presentation.
The Beijing Electron Positron Collider (BEPCII) is a double ring e+e- collider in the 2-5 GeV energy region and the Beijing Spectrometer (BESIII) is a general purpose detector operating at the BEPCII. Decays of J/ψ particle produce a gluon-rich environment and are an ideal place to search for glueball. Discovery of the glueball has been one of the most important scientific goals of the BEPC and BEPCII for decades.
The X(2370) particle was first discovered at the BESIII experiments in 2011. To confirm its pseudoscalar glueball state nature experimentally, the most crucial step is to determine whether the spin parity quantum number of the X(2370) are indeed zero spin and negative parity.
Recently, based on ~10 billion J/ψ decays collected with BESIII, the spin-parity quantum numbers of the X(2370) were firstly measured with a complex partial wave analysis. The experimental results, including quantum numbers, mass, production and decay properties, are consistent with the features of the lightest pseudoscalar glueball. This recent study provides direct and strong experimental evidence for X(2370) being a glueball.

Indico Link:
https://indico.hep.ipm.ir/e/y.huang

Link to Join Virtually:
https://meet.google.com/bda-vsem-tuv