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

23 APR 2025
17:00 - 18:00

Abstract:

The dark dimension scenario, which is motivated from Swampland principles and predicts a single micron scale extra dimension, suggests a consistent framework for the dark sector of the universe. We consider the implications of this scenario for the QCD axion. We find that in the scenario in which the axion is localized on the standard model brane (which we argue is natural), a combination of theoretical (being bounded by the 5D Planck mass) and observational constraints forces it to have decay constant in a narrow range f~10^9 −10^10 GeV.

Indico Link:
https://indico.hep.ipm.ir/e/n.gendler

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

21 APR 2025
11:00 - 12:00

Abstract:

The study of the Standard Model (SM) from the perspective of quantum information theory has led to a variety of interesting results. Recently, quantum entanglement has been employed to explore new physics in top quark pairs, and this concept has found increasing application in high-energy physics. In this talk, I begin by providing an introduction to quantum information theory, with a focus on entanglement and quantum correlations. I then present the results of a paper that considers the entropic uncertainty relations (EURs) and quantum Fisher information (QFI) to investigate the formation of top-antitop quark pairs at the Large Hadron Collider (LHC). This analysis considers both the combination of light quark-antiquark pairs and gluon-initiated processes. A detailed study of the interplay between quark and gluon channels in top quark pair production is significant, with emphasis on the tightness of EURs and the behavior of the system’s maximal QFI.

Based on:
https://doi.org/10.1103/PhysRevD.110.055025

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

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

16 APR 2025
12:30 - 13:30

Abstract:

The Nobel Prize in Physics 2024 was awarded jointly to John J. Hopfield and Geoffrey Hinton "for foundational discoveries and inventions that enable machine learning with artificial neural networks".

Poster:
https://particles.ipm.ir/docs/poster-DrRouhani.pdf

Indico Link:
https://indico.hep.ipm.ir/e/sh.rouhani

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

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

14 APR 2025
11:00 - 12:00

Abstract:
This article presents the design and optimization of a nonlinear kicker injection magnet (NLK) specifically tailored for the ultralow emittance ring at the Iranian Light Source Facility (ILSF). Traditional beam injection methods utilizing septum magnet and multiple dipole kickers are often hindered by challenges such as timing fluctuations and field errors, which can disrupt the operation of stored beams. The proposed NLK configuration eliminates the need for a bump injection trajectory, thus providing a more transparent solution for maintaining beam integrity during injection. Our design incorporates a unique magnetic field profile, characterized by a wide central region with minimal field perturbation, allowing the stored beam to transit with reduced disturbances. Simulations using Opera software in both two and three dimensions were conducted to optimize the magnet's configuration, focusing on maximizing efficiency while addressing key parameters such as eddy currents and wake impedances within a coated ceramic vacuum chamber. An optimized coating thickness was determined to effectively manage thermal loads and magnetic field distribution. The beam dynamics were meticulously analyzed to enhance the overall injection efficiency, achieving a remarkable 98%. This nonlinear kicker system paves the way for advancements in modern synchrotron light source facilities, providing significant improvements in design simplicity, compactness, and operational reliability.

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

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

19 FEB 2025
11:00 - 12:00

Abstract:

We revisit the canonical quantization of free bosonic closed string theory and observe that the physicality of states requires vanishing of the worldsheet Virasoro algebra generators sandwiched between any two physical states. This requirement yields four classes of physical states, depending on discrete worldsheet symmetries: parity and time reversal. The usual string states which are highest weight states of the Virasoro algebra, preserve both, while the other new three classes break one or both. We initiate the quantization of a null p-brane in light-cone gauge using the idea of sandwich quantum constraints and show that solutions to the sandwich conditions are classified into p+1 distinct classes, which we completely specify.

Indico Link:
https://indico.hep.ipm.ir/e/i.rasulian

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

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

17 FEB 2025
11:00 - 12:00

Abstract:

Atomic nuclei are self-organized, many-body quantum systems bound by strong nuclear forces within femtometer-scale space. These complex systems manifest a variety of shapes, traditionally explored using non-invasive spectroscopic techniques at low energies. However, at these energies, their instantaneous shapes are obscured by long-timescale quantum fluctuations, making direct observation challenging. Here we introduce the collective flow assisted nuclear shape imaging method, which images the nuclear global shape by colliding them at ultrarelativistic speeds and analyzing the collective response of outgoing debris. This technique captures a collision-specific snapshot of the spatial matter distribution within the nuclei, which, through the hydrodynamic expansion, imprints patterns on the particle momentum distribution observed in detectors. We benchmark this method in collisions of ground state Uranium-238 nuclei, known for their elongated, axial-symmetric shape. Our findings show a large deformation with a slight deviation from axial symmetry in the nuclear ground state, aligning broadly with previous low-energy experiments. This approach offers a new method for imaging nuclear shapes, enhances our understanding of the initial conditions in high-energy collisions and addresses the important issue of nuclear structure evolution across energy scales.

Based on:
Nature 635, 67-72 (2024)

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

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

5 FEB 2025
11:00 - 12:00

Abstract:

In this paper, we explore the interactions between light axion-like particles (ALPs) and top quarks, gluons, and W-bosons. Utilizing high-energy probes at the LHC, we probe these couplings in the context of single top quark production associated with a W-boson and an ALP. We analyze the latest LHC Run II data on tt spin correlation measurements to establish constraints on these couplings. Additionally, we compare these constraints with those derived from loop-induced couplings and indirect searches involving B-meson decays. Furthermore, we derive two-dimensional limits on the ALP couplings with top quarks and gluons.

Based on:
arXiv:2408.11588

Indico Link:
https://indico.hep.ipm.ir/e/y.hosseini2

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

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

3 FEB 2025
11:00 - 12:00

Abstract:

The proton, one of the components of atomic nuclei, is composed of fundamental particles called quarks and gluons. Gluons are the carriers of the force that binds quarks together, and free quarks are never found in isolation—that is, they are confined within the composite particles in which they reside. The origin of quark confinement is one of the most important questions in modern particle and nuclear physics because confinement is at the core of what makes the proton a stable particle and thus provides stability to the Universe. The internal quark structure of the proton is revealed by deeply virtual Compton scattering, a process in which electrons are scattered off quarks inside the protons, which subsequently emit high-energy photons, which are detected in coincidence with the scattered electrons and recoil protons. Here we report a measurement of the pressure distribution experienced by the quarks in the proton. We find a strong repulsive pressure near the centre of the proton (up to 0.6 femtometers) and a binding pressure at greater distances. The average peak pressure near the centre is about 1035 pascals, which exceeds the pressure estimated for the most densely packed known objects in the Universe, neutron stars. This work opens up a new area of research on the fundamental gravitational properties of protons, neutrons and nuclei, which can provide access to their physical radii, the internal shear forces acting on the quarks and their pressure distributions.

Based on:
https://doi.org/10.1038/s41586-018-0060-z

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

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