19 AUG 2025
14:00 - 15:00

Date and time

Tuesday, August 19, 2025 (28 Mordad), 2:00 pm (Tehran time)




Link

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


Abstract
Parton Distribution Functions (PDFs) are key to understanding the momentum and spin distributions of fundamental particles inside the nucleon, and their precise determination is crucial for rigorous tests of the Standard Model and for predicting outcomes in high-energy collider experiments. In this study, we employ Gegenbauer polynomials—a set of orthogonal polynomials with strong convergence properties and superior ability to model the detailed shape of distributions—to parameterize the polarized parton distribution functions (PPDFs). These polynomials are defined by two key parameters, and by fitting experimental data, unknown parameters are extracted that provide deeper insights into the proton’s structure.
By analyzing comprehensive datasets, especially the final JLAB CLAS/EG1b data for proton and deuteron, the essential role of higher twist effects in accurately determining the PPDFs is demonstrated. The polarized structure functions of the proton, neutron, and deuteron are studied at NLO accuracy, both with and without considering higher twist effects. Additionally, the polarized Bjorken sum rule and proton helicity sum rule are examined to validate the fitting results. The findings show strong agreement with existing data and various parameterization models, indicating that this approach effectively decodes the complex structure of the nucleon and opens new horizons in understanding the behavior of fundamental particles at high energies.

13 AUG 2025
11:00 - 12:00

Abstract:

Higher harmonic cavities are widely used in low-emittance and high-current synchrotron storage rings to increase the stored beam's lifetime and vanish the coupled bunch instabilities. These parameters have an essential effect on the quality of synchrotron radiation and the machine's stability. Higher harmonic cavities of the Iranian light source facility are passive, capacitive-loaded structures designed to operate at 300 MHz. These cavities can operate in the beam current range of 50 to 400 mA. This presentation comprehensively discusses analytical calculations and simulations of beam dynamics, electromagnetic, thermomechanical, and vacuum aspects of the Iranian Light Source Facility's higher harmonic cavities. The engineering drawings are finalized after many technical discussions according to the presented results, and the fabrication process of the higher harmonic cavity has been started accordingly. The low-power RF measurement results of the first developed prototype will be reported in the final section.

Indico Link:
https://indico.hep.ipm.ir/e/Sadeghipanah1

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

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

13 AUG 2025
14:00 - 15:00

Entanglement and quantum coherence have pivotal roles in the recent era of quantum technology. However, these unique quantum features are very fragile to inevitable system-environment interaction and decay very fast. Hence, there has been a long-standing debate on finding the procedures to diminish or ideally wash out such deleterious effects. Over the years, the many different approaches have been developed for this purpose, from quantum feedback control to optimal control theory. At the first part of the talk, we establish our general scheme, referred to as process-based optimal control, to control optimally the destructive effects of environment on the dynamics of an open system. This state-independent framework enables us to reexamine the important problems in quantum technology from a different perspective including gate simulation, system-environment decoupling and indirect environment engineering. At the second part, we introduce some quantum features such as purity and coherence of a quantum dynamics/process. By using these properties, we construct a feature-based approach to increase the purity and coherence of an open system dynamics at a given final time.




Venue: Room D, 3rd Floor, Farmanieh Building, IPM
Link: https://vmeeting2.ipm.ir/b/nan-gkn-wmh-exh

12 AUG 2025
14:00 - 15:00

Date and time

Tuesday, August 12, 2025 (21 Mordad), 2:00 pm (Tehran time)




Link

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


Abstract
We entertain the possibility that transient astrophysical sources can produce a flux of dark particles that induce ultra-high-energy signatures at neutrino telescopes such as IceCube and KM3NeT. We construct scenarios where such “dark flux” can produce meta-stable dark particles inside the Earth that subsequently decay to muons, inducing through-going tracks in large-volume neutrino detectors. We consider such a scenario in light of the O(70) PeV ultra-high-energy muon observed by KM3NeT and argue that because of its location in the sky and the strong geometrical dependence of the signal, such events would not necessarily have been observed by IceCube. Our model relies on the upscattering of a new particle X onto new metastable particles that decay to dimuons with decay lengths of O(100) km. This scenario can explain the observation by KM3NeT without being in conflict with the IceCube data.

11 AUG 2025
11:00 - 12:00

Abstract:

The Swiss Light Source upgrade (SLS 2.0) represents a transition to a fourth-generation synchrotron light source, featuring a diffraction-limited storage ring with ultra-low emittance and enhanced beam quality. This upgrade imposes strict requirements on the vacuum system, especially in the arc sections where compact chambers must withstand high synchrotron radiation power and resistive-wall effects. In this talk, I will introduce the vacuum system design for the SLS 2.0 arcs, focusing on the use of ultra-thin copper chambers with NEG coatings, challenges in manufacturing and assembly, and the solutions adopted to maintain ultra-high vacuum in narrow-aperture environments. The presentation is based on the recent paper “Vacuum chambers for Swiss Light Source arcs” published in Phys. Rev. Accel. Beams.

Based on:
https://journals.aps.org/prab/abstract/10.1103/PhysRevAccelBeams.27.053201

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

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

30 JUL 2025
11:00 - 12:00

Abstract:

Collinear parton distribution functions (cPDFs) and transverse momentum dependent distributions (TMDs) are essential for calculating cross sections in high-energy physics, particularly within collinear and -factorization frameworks. Currently, there exists two libraries, such as LHAPDF and TMDLib, to obtain these physical objects. However, there are limitations in both libraries, especially for TMDs, such as restricted customization and extensibility. Users are limited to the implementations provided by these libraries and cannot easily support unconventional PDFs. Additionally, no standard TMD library currently supports calculations of QCD coupling and uncertainties, which are crucial for precise phenomenological studies. To address these shortcomings, we introduce PDFxTMDLib, a modern C++ library designed to offer a robust and flexible solution. This library supports both collinear PDFs and TMDs while allowing greater customization. It also opens the way to support higher-order distributions. In this article, we describe the structure of PDFxTMDLib. We also demonstrate its validity and performance by integrating it into the PYTHIA Monte Carlo event generator to compute Drell-Yan cross sections. Additionally, comparisons of PDFs obtained from PDFxTMDLib with those from LHAPDF.and TMDLib confirm the reliability of PDFxTMDLib's results.

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

Meeting Place:
Virtual Format

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

30 JUL 2025
14:00 - 15:00

We have considered the spin-1/2 XXZ chain model which is exactly solvable with the Bethe anzats method. It is shown adding a single defect away from edges is sufficient to see a chaos signature in the model. In this work, we have studied the time behavior of the Loschmidt-echo (LE) by considering domain-wall and Neel states as two product initial states and also a Bell state as an entangled initial state. We have used the numerical full diagonalization method to have full spectrum of the model. It is shown that very short times behavior of the LE is independent from defect and initial state, and the decay is quadratic. Moreover, results show that in the chaotic regime and for intermediate times, the exponential decay behavior of the LE shows some changes by removing defect from the chain in the domain-wall and Bell states, while no changes is seen in the Neel state. To get some intuition of these changes, we have addressed the relation between the dynamics of the LE and the local density of states features..

Based on : https://iopscience.iop.org/article/10.1088/1402-4896/ab0582


Venue: Room D, 3rd Floor, Farmanieh Building, IPM
Link: https://vmeeting2.ipm.ir/b/nan-gkn-wmh-exh

29 JUL 2025
14:00 - 15:00

Date and time

Tuesday, July 29th, 2025 (7 Mordad), 2:00 pm (Tehran zone)




Link

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


Abstract
The ATOMKI collaboration measured excesses in electron-positron production from nuclear transitions of beryllium, helium and carbon nuclei. All these excesses are compatible with the emission of a new boson with mass around 17 MeV, denoted X17. An independent search for this particle, harnessing a particle physics experiment, was performed at the Positron Annihilation into Dark Matter Experiment (PADME), where a positron beam collided against a diamond target expecting to produce resonantly the X17 particle. Given the presumably narrow width of this particle, a precise theoretical computation of the signal shape was required to account for electron motion within the target. After including the theoretical modelling of this effect in their analysis, the PADME collaboration has reported an excess in electron-positron events centered around 17 MeV. This excess was later independently shown to largely reduce the uncertainty on the expected X17 mass when combined with nuclear observables. As a byproduct of these studies, electron motion in large Z materials has been shown to enhance centre-of-mass energy in fixed-target experiments and allow for a new energy scan mechanism relevant for the measurement of the hadronic vacuum polarization contribution to the muon anomalous magnetic moment.

28 JUL 2025
11:00 - 12:00

Abstract:

In this talk, I will present a recent paper from the STAR Collaboration, which reports the first observation of a positive spin correlation between Lambda and anti-Lambda hyperon pairs. This finding provides a direct link, via quantum entanglement, between the spin-entangled strange quark pairs of the QCD vacuum and their final-state hadron counterparts, offering crucial insights into the behavior of matter at its most fundamental level.

Based on:
https://arxiv.org/abs/2506.05499

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

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

22 JUL 2025
11:00 - 12:00

Date and time

Tuesday, July 22nd, 2025 (31 Tir), 11:00 AM (Tehran zone)




Link

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


Abstract


This talk addresses the intersection of physics at the smallest and largest scales, where quantum mechanics meets cosmology. We highlight the relevance of this interplay to foundational problems in both cosmology and high energy physics. Our discussion spans the potential quantum features manifesting at galactic or cosmological scales, as well as the role of quantum interferometry in enabling ultra-sensitive measurements in high-energy experiments. These experimental advances not only push the boundaries of precision measurement (such as the detection of gravitational waves), but also open promising avenues for probing quantum aspects of gravity, one of the most profound unresolved questions in theoretical physics.

21 JUL 2025
11:00 - 12:00

Abstract:

Inspired by the “What is…?” column in the Notices of the AMS, this talk provides an informal, nontechnical overview of the core ideas behind different characterizations of anomalies. In the first part, I will briefly survey several mathematical perspectives on the classification and characterization of anomalies in quantum field theories. The second part of the talk focuses on the specific example of the conformal anomaly in two dimensions, illustrating the general concepts with explicit computations and highlighting connections to 2D induced gravity and the AdS_3/CFT_2 correspondence where appropriate.



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

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

16 JUL 2025
14:00 - 15:00

We study the impact of noise on the dynamics of entanglement in the transverse-field Ising chain, with the field quenched linearly across one or both of the quantum critical points of the model. Taking concurrence as a measure of entanglement, we find that a quench generates entanglement between nearest- and next-nearest-neighbor spins, with noise reducing the amount of entanglement. Focusing on the next nearest-neighbor concurrence, known to exhibit Kibble-Zurek scaling with the square root of the quench rate in the noiseless case, we find a different result when noise is present: The concurrence now scales logarithmically with the quench rate, with a noise-dependent amplitude. This is also different from the anti-Kibble-Zurek scaling of defect density with quench rate when noise is present, suggesting that noisy entanglement generation is largely independent from the rate of defect formation. Intriguingly, the critical time scale beyond which no entanglement is produced by a noisy quench scales as a power law with the strength of noise, with the same exponent as that which governs the optimal quench time for which defect formation is at a minimum in a standard quantum annealing scheme.

Based on : https://doi.org/10.48550/arXiv.2503.03584


Venue: Room D, 3rd Floor, Farmanieh Building, IPM
Link: https://vmeeting2.ipm.ir/b/nan-gkn-wmh-exh

16 JUL 2025
11:00 - 12:00

Abstract:

Understanding the fundamental nature of dark matter remains one of the most profound challenges in modern physics. In this talk, I will present how cosmic birefringence—the rotation of the polarization plane of Cosmic Microwave Background (CMB) photons—can serve as a sensitive probe of dark matter phenomenology. I will focus on theoretical frameworks in which dark matter candidates, such as sterile neutrinos, dipolar dark matter, or axion-like fields, induce parity-violating effects that manifest as measurable birefringence. These signatures offer a unique observational window into the interactions between dark matter and Standard Model particles, providing constraints that are complementary to those from conventional direct and indirect detection methods.

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


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

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