6 FEB 2023
11:00 - 12:00

Abstract:

Measurements of the inclusive and normalized differential cross sections are presented for the production of single top quarks in association with a W boson in proton-proton collisions at a centre-of-mass energy of 13TeV. The data used were recorded with the CMS detector at the LHC during 2016–2018, and correspond to an integrated luminosity of 138 fb−1. Events containing one electron and one muon in the final state are analyzed. For the inclusive measurement, a multivariate discriminant, exploiting the kinematic properties of the events is used to separate the signal from the dominant tt background. A cross section of
79.2 ± (syst) ±1.2 (lumi) pb is obtained, consistent with the predictions of the standard model. For the differential measurements, a fiducial region is defined according to the detector acceptance, and the requirement of exactly one jet coming from the fragmentation of a bottom quark. The resulting distributions are unfolded to particle level and agree with the predictions at next-to-leading order in perturbative quantum chromodynamics.

Based on
https://arxiv.org/abs/2208.00924v1

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

Virtual room:
https://meet.google.com/fnv-dfkk-ghb

1 FEB 2023
11:00 - 12:00

Abstract:

The phase-2 upgrade of the CMS RPC System for the low-eta region will enhance the electronics performance, and muon hit time resolution to cope with the High Luminosity Large Hadron Collider (HL-LHC) conditions. In the Compact Muon Solenoid (CMS) experiment, Resistive Plate Chambers (RPC) have between 36 and 96 strips read out by frontend electronics boards (FEB). The FEB outputs are connected to the IPM electronics known as the Link System, where 96-channel time-to-digital converters (TDC) implemented in a Kintex-7 Field Programmable Gate Array (FPGA) measure the arrival time of the muon hit at a fine-time resolution of 1.56 ns that is near to the RPC intrinsic time resolution. Additionally, the Link System will be installed in a radiation environment and must tolerate radiation effects. This talk will review the new Link System and explain how this system fulfilled the CMS Phase-2 upgrade requirements.

Indico Link
https://indico.hep.ipm.ir/e/b.boghrati.part2


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

Link to join virtually:
https://meet.google.com/fnv-dfkk-ghb

1 FEB 2023
14:00 - 15:00

Inside living cells many essential processes involve deformation of charged helical molecules and interaction between them. Actin filaments and DNA molecules with linear charge distribution -1e/0.27nm and -2e/0.34nm respectively, are important examples of charged helical molecules. On the other hand, the existence of salt concentration inside the cell environment emphasizes on the crucial role of the electrostatic interactions in biological systems. Here we consider an impermeable dielectric molecule in the solvent with a different dielectric constant. The electrostatic free energy in the problem is studied in the Debye-Huckel regime using the analytical Green function method. Using this electrostatic free energy, we study the electrostatic contribution to the twist rigidity of a double stranded helical molecule such as DNA and actin filaments. The dependence of the electrostatic twist rigidity of the molecule to the dielectric inhomogeneity, structural parameters and the salt concentration is studied. It is shown that, depending on the parameters, the electrostatic twist rigidity could be positive or negative.

31 JAN 2023
14:00 - 15:00

Date and time

Tuesday, 31th of January 2023 (11th of Bahman, 1401), 2:00 pm (Tehran zone)

Link

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



Abstract

We construct microstates of 3d black holes in the Hilbert space of tensionless null strings with non-zero winding along the bifurcation horizon. Counting these string states we recover the Bekenstein-Hawking entropy and its semiclassical logarithmic corrections.

30 JAN 2023
11:00 - 12:00

Abstract:

The discovery of the unique resistance switching mechanism in memristive devices is attracting efforts to replace current transistors in dynamic random access memories (DRAM) and is introducing a novel architecture for in-memory computing devices that provides optimal functionality for neural network computation. Briefly speaking, these developments are of particular importance and are leading to a revolution in the future of electronic devices. It is expected that memristive devices can be used to construct long-term memories, but faster than current DRAM. Although memristive devices can be a very efficient choice in the development of high-speed and low-cost computer technologies, such devices are not commercially exploited mainly because of the construction issues. Among these technical issues, the lack of a reliable model to explain the physics of the switching mechanism is the main problem, this resistance switching mechanism is mainly based on the drift of metal ion atoms into the active insulator layer ( ionic channel) as a function of the applied voltage. In this talk, I will present a novel and unique method for discovering the nature of the ionic channel in the memristor. This method is based on the implantation of a radioactive probe into the memristive devices.

Based on
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Meeting Place
https://meet.google.com/fnv-dfkk-ghb

25 JAN 2023
11:00 - 12:00

Abstract:

The phase-2 upgrade of the CMS RPC System for the low-eta region will enhance the electronics performance, and muon hit time resolution to cope with the High Luminosity Large Hadron Collider (HL-LHC) conditions. In the Compact Muon Solenoid (CMS) experiment, Resistive Plate Chambers (RPC) have between 36 and 96 strips read out by frontend electronics boards (FEB). The FEB outputs are connected to the IPM electronics known as the Link System, where 96-channel time-to-digital converters (TDC) implemented in a Kintex-7 Field Programmable Gate Array (FPGA) measure the arrival time of the muon hit at a fine-time resolution of 1.56 ns that is near to the RPC intrinsic time resolution. Additionally, the Link System will be installed in a radiation environment and must tolerate radiation effects. This talk will review the new Link System and explain how this system fulfilled the CMS Phase-2 upgrade requirements.

Indico Link:
https://indico.hep.ipm.ir/e/b.boghrati

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

Link to join virtually:
https://meet.google.com/fnv-dfkk-ghb

25 JAN 2023
16:30 - 18:00

I will give a survey of some problems and recent results concerning the link between the monodromies of structure connections on certain Frobenius manifolds with the numerology of the derived categories of Fano varieties.





Zoom link:


https://zoom.us/j/92708332316?pwd=MGlBRWhTUy9wSzg5VGppTUNQVXN6dz09


Meeting ID: 927 0833 2316


Passcode: 692489








Subscribing the Mathematics Colloquium mailing list:


https://groups.google.com/g/ipm-math-colloquium

24 JAN 2023
14:00 - 15:00

Date and time
Tuesday- 24th of January 2023 - 4th of Bahman, 1401- 2:00 pm (Tehran zone)

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

Abstract
Cosmic voids are known as underdense substructures of the cosmic web that cover a large volume of the Universe. It is known that cosmic voids contain a small number of dark matter halos. Regarding this, the existence of primordial black holes (PBHs) in these secluded regions of the Universe is not unlikely. In this talk, I intend to speak about our recent analysis on the merger rate of PBHsin cosmic voids and their contribution to gravitational wave events resulting from black hole mergers recorded by the Advanced Laser Interferometer Gravitational-Wave Observatory (aLIGO)-Advanced Virgo (aVirgo) detectors.

23 JAN 2023
11:00 - 12:00

Abstract:

Nowadays, production of ultrashort and high-current electron bunches of few fs to hundred fs with several pc charge is a very attractive subject in the context of many recent applications, specially, in light sources, free electron lasers and plasma wake field accelerators. In the light sources and free electron lasers, the radiation gain is directly proportional to the beam pick current and so obtaining very short bunches on the order of fs plays an essential role for high gain machines.
Consequently, recent approaches for production of such electron bunches are based on usage of photo injectors in combination with a chain of bunch compressors. In the Iranian light source project attempts are directed toward the designing a novel compact soft X-ray synchrotron beyond the state of the art, using the latest advanced studies worldwide. The project will be started form a novel photoinjector which can provide very high quality, and in the meantime, ultra-short electron bunches in a compact structure. Moreover, finding the best structures for the rf components, specifically, the rf gun and its associated buncher cavity has a crucial effect on the function of the whole light source in near future. In this talk I will show some of the photocathode RF gun designing and compare the results.

Based on
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Meeting Place
Seminar room of School of particles and accelerators,IPM

18 JAN 2023
11:00 - 12:00

Abstract:

Dark photons are predicted by various new physics models, and are being intensively studied in a variety of experiments. In the first part of this paper, we obtain partial wave unitarity constraints on the dark photon parameter space from the allowed VV→VV scattering processes in the limit of large center-of-mass energy, where V=W,Z. In the second part of the paper, searches are performed using the expected differential rates with a realistic detector simulation including a comprehensive set of background processes on dilepton and dilepton plus a photon events at the High Luminosity LHC. In these searches, sensitive differential distributions are used in an optimized way to determine the sensitivity to dark photon parameter space. It is shown that remarkable sensitivity to the dark photon model is achieved and kinetic mixing strength can be probed down to $(1.4−10)\times 10^{−4}$ for dark photon mass between 15 GeV to 2 TeV. We also investigate the sensitivity of a future muon collider suggested by the Muon Accelerator Program (MAP) to the dark photon model at different center-of-mass energies. It is shown that a future muon collider is able to reach a sensitivity to kinetic mixing at the order of $10^{−4}$.

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

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

18 JAN 2023
14:00 - 15:00

Separation of magnetic or magnetically labeled biological or synthetic particles in micro-fluidic setups has been recently achieved by subjecting them to an external magnetic field to produce controlled alterations in the flow-driven motion of target particles based on their size, shape and magnetic properties. We investigate Brownian noise effects on magnetic focusing of prolate and oblate spheroids carrying permanent magnetic dipoles in channel (Poiseuille) flow subject to a uniform magnetic field. The focusing is effected by the low-Reynolds-number wall-induced hydrodynamic lift which can be tuned via tilt angle of the field relative to the flow direction.

This mechanism is incorporated in a steady-state Smoluchowski equation that we solve numerically to analyze the noise effects through the joint position-orientation probability distribution function of spheroids within the channel. We complement this approach by analyzing stability of deterministic fixed points and a reduced onedimensional probabilistic theory which we introduce to semi-quantitatively explain noise-induced behavior of pinned spheroids under strong fields. The results reveal remarkable and even counterintuitive noise-induced phenomena that include fieldinduced defocusing upon strengthening the field. We map out focusing ‘phase’ diagrams based on the field strength and tilt angle to illustrate different regimes of behavior including centered focusing and defocusing in transverse/longitudinal fields and off-centered focusing in tilted fields. The latter encompasses two subregimes of optimal and shouldered focusing where spheroidal density profiles across the channel width display either an isolated off-centered peak or a skewed peak with a pronounced shoulder stretching toward the channel center. We also elucidate the implications of our results for efficient shape-based sorting of magnetic spheroids.

17 JAN 2023
14:00 - 15:00

Date and time
Tuesday, 17th of January 2023 (27th of Dey, 1401), 2:00 pm (Tehran zone)


Link
https://us02web.zoom.us/j/89461255809?pwd=d3RhVjNlaVl5aURRMFVHYnlVajdzUT09



Meeting ID: 894 6125 5809
Passcode: 873704



Abstract

We consider the standard Maxwell's theory in 1+3 dimensions in the presence of a timelike boundary. In this context, we show that (generalized) Ampere-Maxwell's law appears as a Noether charge associated with the Maxwell U(1) gauge symmetry which satisfies a spatial conservation equation. Furthermore, we also introduce the notion of spatial memory field and its corresponding memory effect. Finally, similar to the temporal case through the lens of Strominger's triangle proposal, we show how spatial memory and conservation are related.

16 JAN 2023
11:00 - 12:00

Abstract:

In the hydrodynamic model description of heavy ion collisions, the elliptic flow v2 and triangular flow v3 are sensitive to the quadrupole deformation β2 and octupole deformation β3 of the colliding nuclei. The relations between vn and βn have recently been clarified and were found to follow a simple parametric form. The STAR Collaboration have just published precision vn data from isobaric 96Ru+96Ru and 96Zr+96Zr collisions, where they observe large differences in central collisions v2,Ru >v2,Zr and v3,Ru
Based on
https://doi.org/10.1103/PhysRevLett.128.022301

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