7 DEC 2022
11:00 - 12:00

Abstract:

In this work, we study the heavy-ion collisions in high energy scales. we employ the EMC effect to extract the parton distribution functions (PDF s) inside the Lead (Pb) and Gold (Au) nuclei. Calculated PDFs are used to achieve the transverse momentum dependent (TMD) ones, using the Pythia 8 and MCFM-10 codes. Through this procedure TMDPDFs for charm and bottom quarks in Au at $\sqrt{S_{NN}} = 200$ GeV, Pb at $\sqrt{S_{NN}} = 2.76$ TeV and $\sqrt{S_{NN}} = 5.02$ TeV are calculated. To evaluate the validity of results and investigate the influence of nuclear EMC effects, achieved TMDs are used as input to calculate the heavy quark modification factor $R_{AA}$ at transverse plane $P_T$. This observable is calculated through numerical solution of the Fokker-Planck equation by extracting the drag and diffusion coefficients, using the hard thermal loop correction in the frame work of the relativistic hydrodynamics up to the third order approximation of gradient expansion. The results are compared with same solution when the input PDFs are considered inside the unbounded protons. Some predictions for future experiments are also presented.

Indico Link
https://indico.hep.ipm.ir/e/j.sheibani

Meeting Link
https://meet.google.com/gwq-hepa-cpy

5 DEC 2022
11:00 - 12:00

Abstract:

The first measurements of production cross sections of polarized same-sign W^± W^± boson pairs in proton-proton collisions are reported. The measurements are based on a data sample collected with the CMS detector at the LHC at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 137 fb^(-1) . Events are selected by requiring exactly two same-sign leptons, electrons or muons, moderate missing transverse momentum, and two jets with a large rapidity separation and a large dijet mass to enhance the contribution of same-sign W^± W^± scattering events. An observed (expected) 95% confidence level upper limit of 1.17 (0.88) fb is set on the production cross section for longitudinally polarized same-sign W^± W^± boson pairs. The electroweak production of same-sign W^± W^± boson pairs with at least one of the W bosons longitudinally polarized is measured with an observed (expected) significance of 2.3 (3.1) standard deviations.

Based on
doi:10.1016/j.physletb.2020.136018

Meeting Link
https://meet.google.com/jyc-uqyh-bmq

30 NOV 2022
11:00 - 12:00

Abstract:

At the back of succeeding measurements of anomalies in semileptonic decays at several collider experiments hinting at the possible violation of lepton flavor universality, we undertake a concise review of theoretical foundations of the tree- and loop-level b-hadron decays along with experimental environments. We revisit the world averages for $R_{D(D^*)}$, $R_{K(K^*)}$, $R_{J/\psi}$ and $R_{\eta_c}$, and provide results within the framework of the relativistic independent quark model in addition to the results from model-independent studies. A confirmation of these measurements would soon turn out to be the first observation of physics beyond the Standard Model giving a wider outlook on the better understanding of new physics.

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

Meeting Link
https://meet.google.com/gwq-hepa-cpy

28 NOV 2022
11:00 - 12:00

Abstract:

The production of intense high-quality positrons for R&D in high-energy physics colliders and other applications is achieved using GeV-energy electrons impinging on a hybrid tungsten target. The positrons emerge from the target with a large momentum spread and at non-relativistic energies, and they have to be accelerated rapidly in order to be transported to the next stages of the accelerator. The CLIC positron source consists of a hybrid target, an adiabatic matching device and a capture Linac. The parameters of these devices influence strongly the final useable positron yield.
In the tracking simulations, a fixed gradient is assumed. In reality, the capture structure suffers strong beam loading from both the positrons and the remaining electrons from pair production. It is therefore difficult to evaluate the real gradient of the structure and its stability along the pulse. The objective of this study is studding the effect of transient beam loading on the positrons as they travel through the accelerating components of the Linac.

Based on
https://arxiv.org/abs/2202.04939
http://dx.doi.org/10.1063/1.33620

Meeting Link
https://meet.google.com/jyc-uqyh-bmq

23 NOV 2022
11:00 - 12:00

Abstract:

The collision of heavy ions in the hadron colliders produces a rich environment to study different aspects of QCD, from the geometry of the hadrons bound states in heavy ions to the collective evolution of a hot medium made of quarks and gluons, called quark-gluon plasma (QGP). Modeling various aspects of the experiment and extracting information from the measurements are the main challenges in the heavy-ion community. This talk overviews the latest physical picture of heavy-ion collisions and the systematic methods to improve this picture, exploiting the measurements. In particular, I will discuss the Bayesian approach to infer the model parameters from data. I will present speculations about the applicability of hydrodynamics when the produced matter is around the size of a proton. I will also discuss the deformation of heavy ions and extracting their geometry by using flow analysis of two isobar elements.

Indico Link
https://indico.hep.ipm.ir/e/f.taghavi

Meeting Link
https://meet.google.com/gwq-hepa-cpy

21 NOV 2022
11:20 - 14:30

Diamond magnetometry is a quantum sensing technique which allows nanoscale MRI. It is based on a defect in diamond, the so-called NV center, which changes its optical properties based on its magnetic surrounding. Since optical signals can be read out more sensitively, this technique offers unprecedented sensitivity. We will first give a general overview over different modes of diamond magnetometry and discuss advantages and drawbacks.
In the second lecture we will focus on relaxometry, a specific mode of diamond magnetometry and how we use this technique to answer biological questions. More specifically, relaxometry is sensitive to magnetic noise and in a biological context this technique allows us to detect free radical generation which is an important biomarker for stress responses in cells and organisms and is difficult to access with state-of-the-art technology.
Finally, we will discuss the commercial applications of diamond magnetometry and more specifically of relaxometry. Further, we will introduce Diamond Visions and their activities to give an insight over the commercial aspects of diamond magnetometry that are currently available.

21 NOV 2022
11:00 - 12:00


Abstract:

In this paper, we present the development of a numerical model to determine the energy spectrum from an attenuation curve via transmission measurements which combines two types of inverse models: a continue model and a discrete model. We validate this tool using a test spectrum and its transmission curve obtained via Monte-Carlo simulation. This qualification allowed us to determine its sensitivity (signal-to-noise ratio, SNR) in order to have a good convergence. We show that if the SNR is less than 4%, we have a good estimation of the photon energy spectrum. Then, it was experimentally tested with a transmission curve obtained at the laboratory.

Based on
https://doi.org/10.1051/epjconf/202125304002 https://doi.org/10.4236/ijmpcero.2020.94017

Meeting Link
https://meet.google.com/jyc-uqyh-bmq

16 NOV 2022
13:30 - 15:00

I will discuss our recent work Phys.Rev.Lett. 128 (2022) 4, 041301 in which we present a simple class of mechanical models where a canonical degree of freedom interacts with another one with a negative kinetic term,i.e., with a ghost. We prove analytically that the classical motion of the system is completely stable for all initial conditions, notwithstanding that the conserved Hamiltonian is unbounded from below and above.
Numerical computations fully supported this. Systems with negative kinetic terms often appear in modern cosmology, quantum gravity, and high energy physics and are usually deemed as unstable.
Our result demonstrates that, for mechanical systems, this common lore can be too naïve and that a stable living with ghosts is possible.
To join the seminar, please click on the following link


https://www.skyroom.online/ch/soa/weekly-seminar

9 NOV 2022
13:30 - 15:00

In this talk I review the recent works on the astrophysical implications of Mashhoon-Hehl nonlocal gravity (NLG) theory.
I discuss the physical characteristics of the effective dark matter in NLG specifically within the dwarf galaxies like the ultra-diffuse galaxies AGC 114905, 242019, and 219533. Furthermore, I present the results of some high-resolution galactic simulations conducted in NLG, and discuss the analytical computation of the dynamical friction force in NLG in the presence and absence of tidal effects. This force plays significant roles in connection with the dynamics of the stellar bars.

Mojtaba Raouf
(Leiden Observatory, Netherlands)

2 NOV 2022
13:30 - 15:00

In this talk I will present hydrodynamic simulations of the interstellar medium gas within the circumnuclear disk (CND) of the Syfert 2 galaxy NGC 1068 influenced by the feedback from active galactic nuclei(AGN). The simulations coupled with the CHIMES non-equilibrium chemistry network to treat the radiative cooling and AGN heating. A focus is placed on the central 200 pc around the black hole where AGN outflows and radiation are coupled to the ISM compared to a model without AGN feedback. For a given geometrical distribution of gas, we post-process the simulation snapshots with a radiative transfer code to obtain synthetic observations of the molecular emission lines. The model including AGN feedback shows that there is a deficiency of molecular gas in the central region of the CND consistent with observations. Higher -J CO lines appear to have increased intensity in the 100 pc scale ring surrounding BH whereas CO integrated intensity at larger radii appears to diminish with increasing time scale. A kinematic analysis of the inclined disc indicates that the CND is oriented southwest-northeast. We attempt to discern between the competing explanations for the apparent counter-rotating gas in the AGN-dominated galaxy NGC 1068 through the analysis of kinematic maps of CO line emission in CND coupled with AGN feedback. The position velocity diagrams are also somewhat consistent with the predicted Keplerian rotation curve, which is in agreement with the observations of NGC 1068.

1 NOV 2022
16:30 - 18:00

Abstract: We give a formula which, for a principally polarized abelian variety $(A, \lambda)$ over a number field (or a function field), relates the stable Faltings height of $A$ with the N\'eron--Tate height of a symmetric theta divisor on $A$. Our formula involves invariants arising from tropical geometry. We also discuss the case of Jacobians in some detail, where graphs and electrical networks will play a key role. (Based on joint works with Robin de Jong.)

https://zoom.us/join
Meeting ID: 9086116889
Passcode: 362880

27 OCT 2022
11:00 - 13:00

Speaker: Reza Naghipour, University of Tabriz

Let a be an ideal of a commutative Noetherian ring R and let M be a finitely generated R-module. The purpose of this talk is to establish some new results on Lynch?s conjecture and the set of the attached primes of top local cohomology module H cd(a,M) a (M) for the case of R has prime characteristic and cd(a, M) = araM(a). To prove our results, we estab- lish and use a new relation between the set AttR(H cd(a,M) a (M)) and M-height of the anni- hilator of top local cohomology module H cd(a,M) a (M). Several corollaries of this result are proved. Among other things, we will provide a complete characterization of the attached primes of the top local cohomology module H cd(a,M) a (M) and Rad(AnnR(H cd(a,M) a (M))). Using this, we show that the ideal AnnR(H cd(a,M) a (M)) has M-height zero. This talk is based on joint work with Ali Atazadeh.

26 OCT 2022
16:00 - 18:00

Modified gravitation known as Scalar-Tensor-Vector-Gravity (STVG) and MOG and its consequences for dark matter, dark energy, astrophysics and cosmology are reviewed.

20 OCT 2022
11:00 - 13:00

Speaker: Rasoul Ahangari, IPM
Title: Free REsolutions over generic artinian gornestein graded algebras of socle degree 3

Abstract. An Artinian Gorenstein graded algebra R (over a field) with socle in degree 3 is in correspondence with a cubic form F via the so-called Macaulay inverse system. If F is a generic cubic, then we say that R is generic. In this talk, we study free resolutions over R by studying its Koszul dual which is a non- commutative algebra. We prove that if R is generic, then any finitely generated R-module annihilated by at least two generic linear forms, is a Koszul module. This talk is based on a joint work with Liana Sega.

18 OCT 2022
16:30 - 18:00

Speaker: Sandra Di Rocco, KTH, Sweden Title: Geometry of algebraic data Abstract: It is often convenient to visualize algebraic varieties (and hence systems of polynomial equations) by sampling. The key challenge is to have the right distribution and density in order to recover the shape, i.e the topology of the variety. Bottlenecks are pairs of points on the variety joined by a line which is normal to the variety at both points. These points play a special role in determining the appropriate density of a point-sample. Under suitable genericity assumptions the number of bottlenecks of an affine variety is finite and is called the bottleneck degree. Estimations of the bottleneck degree and certain generalizations lead to efficient sampling techniques. We will show how classical projective algebraic geometry has proven very useful in this analysis. The talk is based on joint work with D. Eklund, P. Edwards, O. Gäfvert, J Hauenstein, M. Weinstein. Date: Tuesday, October 18 (Mehr 26th)
Time: 16:30-18:00 (Tehran local time)
Venue: via Zoom:
Meeting ID: 908 611 6889 -- Passcode: 362880