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

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

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.

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

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


Link: 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

Link: http://qpm.ipm.ac.ir/

6 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

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