2 JUN 2025
11:00 - 12:00

Abstract:

A search for resonances in top quark pair (ttˉ) production in final states with two charged leptons and multiple jets is presented. The analysis is based on proton-proton collision data collected by the CMS experiment at the CERN Large Hadron Collider (LHC) at a center-of-mass energy of TeVs=13 TeV, corresponding to an integrated luminosity of 138 fb−1. The study investigates the invariant mass distribution of the ttˉ system, along with two angular observables that provide direct sensitivity to the spin correlations between the top quark and antiquark. A significant excess of events is observed near the kinematic ttˉ threshold when compared to the expectations from nonresonant production as predicted by fixed-order perturbative quantum chromodynamics (pQCD). This observed enhancement is compatible with the production of a color-singlet pseudoscalar quasi-bound toponium state in the 1S0[1] configuration, as predicted by nonrelativistic quantum chromodynamics (NRQCD). Within the framework of a simplified model for 1S0[1] toponium, the cross section of the excess above the pQCD prediction is measured to be: pbσexcess=8.8−1.4+1.2 pb.

Based on:
https://arxiv.org/abs/2503.22382, https://arxiv.org/abs/2503.22382, https://arxiv.org/abs/2503.22382, https://arxiv.org/abs/2503.22382

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

Link to Join Virtually:
https://www.skyroom.online/ch/ipm-particles/journal-club

28 MAY 2025
11:00 - 12:00

Abstract:

Singularities in Newton's gravitation, in general relativity (GR), in Coulomb's law, and elsewhere in classical physics, stem from two ill-conceived assumptions: a) there are point-like entities with finite masses, charges, etc., packed in zero volumes, and b) the non-quantum assumption that these point-likes can be assigned precise coordinates and momenta. In the case of GR, we argue that the classical energy-momentum tensor in Einstein's field equation is that of a collection of point particles and is prone to singularity. In compliance with Heisenberg's uncertainty principle, we suggest replacing each constituent of the gravitating matter with a suitable quantum mechanical equivalent, here a Klien-Gordon (KG) or a Yukawa-ameliorated version of it, YKG field. KG and YKG fields are spatially distributed entities. They do not end up in singular spacetime points nor predict singular blackholes. On the other hand, YKG waves reach infinity as 〖1/r e〗^(-(κ±ik)r). They create the Newtonian r^(-2) term as well as a non-Newtonian r^(-1) force. The latter can explain the observed flat rotation curves of spiral galaxies, and is interpretable as an alternative gravity, a dark matter scenario, etc. There are ample observational data on flat rotation curves of spiral galaxies, coded in the Tully-Fisher relation, to support our propositions.


Indico Link:
https://indico.hep.ipm.ir/e/h.sheikhahmadi1

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

Link to Join Virtually:
https://www.skyroom.online/ch/ipm-particles/weekly-seminar

21 MAY 2025
12:30 - 13:30

Abstract:

In this lecture, I will discuss recent efforts on discovery of black holes. I will also explain and elaborate on cases in which I have contributed in these discoveries.

Poster:
https://particles.ipm.ac.ir/pdf/poster_drrahvar.pdf

Indico Link:
https://indico.hep.ipm.ir/e/s.rahvar

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

Link to Join Virtually:
https://www.skyroom.online/ch/ipm-particles/special-seminar

19 MAY 2025
11:00 - 12:00

Abstract:

In this paper, they consider top quark decay in the standard model effective field theory (SMEFT). They present a calculation of the total decay width and the W-boson helicity fractions at next-to-leading order (NLO) in SMEFT. Their result includes the complete set of contributing four-fermion operators in addition to QCD dipole operators and bottom-mass suppressed effects. They show that operators that first appear at NLO in the SMEFT can be bounded by the current data as well as future data from both a high-luminosity LHC and a potential e+e− collider, demonstrating the importance of going beyond leading order when studying the SMEFT. They discuss technical aspects of Their calculation that They believe will be useful in future higher-order studies of the SMEFT, in particular, the treatment of γ5 in loop diagrams.

Based on:
https://arxiv.org/abs/1907.00997

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

Link to Join Virtually:
https://www.skyroom.online/ch/ipm-particles/journal-club

14 MAY 2025
11:00 - 12:00

Abstract:

This talk addresses key challenges in modern cosmology and introduces the motivations for a "void-based cosmology". In this approach, voids (bubbles) are treated as independent, dynamic components of the cosmic web next to clusters (drops). Drawing inspiration from the behavior of heated milk overflowing, the presentation will examine the connection between void surface tension and the cosmological constant, the modified uncertainty principle, and the evolving dark energy density resulting from void mergers on cosmic scales.

Indico Link:
https://indico.hep.ipm.ir/e/e.yusofi

Link to Join Virtually:
https://www.skyroom.online/ch/ipm-particles/weekly-seminar

12 MAY 2025
11:00 - 12:00

Abstract:

In this talk, a novel storage ring lattice design for synchrotron radiation sources which fulfills all the required features for the realization of a diffraction limited light source will be presented. In this lattice the insertion devices with half gaps of 2.5 mm are assumed and enabled by the design of dedicated straight sections. The use of long straight sections is possible for such a lattice and led to the definition of a set of transparency conditions used to minimize the effect of such insertions for on- and off- energy beam dynamics. The design proposed enables an extremely long Touschek lifetime and beam accumulation. A real case study will be shown for large circumference storage ring upgrade lattices.

Based on:
https://10.1103/PhysRevAccelBeams.26.021601

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

Link to Join Virtually:
https://www.skyroom.online/ch/ipm-particles/journal-club

7 MAY 2025
11:00 - 12:00

Abstract:

We classify conformal extensions of the Carroll algebra in arbitrary dimensions, and explore their infinite-dimensional extensions. We further constrain the corresponding two and three point invariant correlation functions with electric and/or magnetic features.

Indico Link:
https://indico.hep.ipm.ir/e/h.afshar1

Link to Join Virtually:
https://www.skyroom.online/ch/ipm-particles/weekly-seminar

5 MAY 2025
11:00 - 12:00

Abstract:

This presentation explores the application of classical and quantum machine learning techniques in particle physics, highlighting their role in tasks such as jet classification, Higgs boson and SUSY identification, and fully hadronic event generation. It begins with an overview of the historical development of artificial intelligence and foundational concepts in deep learning, followed by practical implementations of deep neural networks (DNNs) and convolutional neural networks (CNNs) in high-energy physics analyses, including supersymmetry searches and jet substructure studies. The presentation then introduces quantum machine learning (QML), covering models such as quantum support vector machines (QSVMs) and variational quantum classifiers (VQCs), along with their advantages and challenges in Higgs boson identification. Finally, the use of generative AI is presented as a solution for data generation in both Standard Model and beyond Standard Model scenarios, enabling the production of synthetic datasets significantly faster than traditional Monte Carlo simulations involving MadGraph, Pythia, and Geant4.

Based on:
https://link.springer.com/article/10.1140/epjc/s10052-023-11543-6 ,
https://cs231n.stanford.edu/reports/2016/pdfs/300_Report.pdf ,
https://arxiv.org/abs/2104.07692,
https://arxiv.org/abs/1701.05927

Indico Link:
https://indico.hep.ipm.ir/e/m.ghasemi

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

Link to Join Virtually:
https://www.skyroom.online/ch/ipm-particles/journal-club

30 APR 2025
11:00 - 12:00

Abstract:

Interest of the research in terahertz (THz) wave has been strongly motivated by its wide applications in the fields of physics, chemistry, biology, and engineering. Developing efficient and reliable THz source is of uttermost priority in these researches. Generally, due to the restrictions mainly caused by laser damage threshold, it is not possible to generate efficient and strong THz radiation. Plasma is a quasi-neutral medium composed of electrons and positive ions, exhibiting long-range collective behavior. It has garnered significant attention as a promising source for generating THz electromagnetic wave, primarily due to the ease with which it can tolerate very high power laser and provide strong THz beams in comparison with other media. This review focuses on the various key aspects of THz mechanisms in laser-plasma interactions and also examines the characteristics of the emitted THz waves under different laser and plasma parameters. Harnessing the advancements in ultrafast pulses, laser-induced plasma has proven to be a promising tool for generating THz waves.

Indico Link:
https://indico.hep.ipm.ir/e/s.safari

Link to Join Virtually:
https://www.skyroom.online/ch/ipm-particles/weekly-seminar

28 APR 2025
11:00 - 12:00

Abstract:

The CMS-TOTEM Precision Proton Spectrometer (PPS) is a CMS subdetector operating at the Large Hadron Collider (LHC) installed at a distance of ~200-220 meters from the CMS central detector. PPS measures the kinematics and time-of-flight of protons scattered in the very forward region with high precision. In this talk, I will explain how the PPS data is used to reconstruct protons at the interaction point and how it helps study Central Exclusive Production (CEP) processes.

Based on:
arXiv:2210.05854 and arXiv:2211.16320.

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

Link to Join Virtually:
https://www.skyroom.online/ch/ipm-particles/journal-club