23 SEP 2024
11:00 - 12:00

Abstract:

We have studied the entanglement of purification Ep in a non-conformal holographic model which is a five-dimensional Einstein gravity coupled to a scalar field ϕ with a non-trivial potential V (ϕ). The dual 4-dimensional gauge theory is not conformal and exhibits a RG flow between two different fixed points. There are three parameters including energy scale Λ, model parameter ϕM and temperature T which control the behaviour of the theory. Interestingly, we have found that Ep can be used as a measure to probe the non-conformal behavior of the theory at both zero and finite temperature.

Based on:
https://arxiv.org/pdf/2408.05522

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

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

16 SEP 2024
11:00 - 12:00

Abstract:

Preserving the phase space quality has been of crucial importance to high-brightness electron beam transport. Any driving source of beam performance limitations in such a transport system must be carefully examined in order to preserve the beam phase space quality. It is found that in the low beam energy, high bunch charge regime, space charge effect on the charged particle beam evolution can be complicated. It may be insufficient to analyze the beam properties through the envelope or lower order moments for the mere bulk of the beam. In this work we will study the space-charge-dominated, low-energy, high-brightness electron beam dynamics based on the slice beam matrix method. The slice beam matrix method, extended from the existing bulk beam analysis, is applicable to an arbitrary longitudinal bunch distribution and can thus take the nonlinear RF curvature into account. The semi-analytical sliced beam space charge model is constructed and assumes an axisymmetric beam in the presence of perfect conducting cylindrical pipe with circular cross section. We present in this paper the theoretical formulation, starting from single-particle dynamics, space charge field calculation, followed by the moment description of a collection of particles, based on beam sigma matrix and longitudinal slice decomposition. We prove the equivalence between the beam matrix method and the envelope formalism in the presence of space charge effect, in both the transverse and longitudinal dimensions.

Based on:
https://doi.org/10.1016/j.nima.2019.05.035

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

Link to Join Virtually:
https://meet.google.com/bda-vsem-tuv

11 SEP 2024
11:00 - 12:00

Abstract:

In the Standard Model (SM) of particle physics, gluons are the fundamental particles mediating the strong interaction, as photons do in electromagnetic interactions. Gluons can attract each other to form new bound states called glueballs, which are the only particles in nature entirely composed of force mediators. Finding these gluon bound states is crucial and serves as a fundamental test of the SM. No candidate has yet been unambiguously identified until the new BESIII result to be reported in this presentation.
The Beijing Electron Positron Collider (BEPCII) is a double ring e+e- collider in the 2-5 GeV energy region and the Beijing Spectrometer (BESIII) is a general purpose detector operating at the BEPCII. Decays of J/ψ particle produce a gluon-rich environment and are an ideal place to search for glueball. Discovery of the glueball has been one of the most important scientific goals of the BEPC and BEPCII for decades.
The X(2370) particle was first discovered at the BESIII experiments in 2011. To confirm its pseudoscalar glueball state nature experimentally, the most crucial step is to determine whether the spin parity quantum number of the X(2370) are indeed zero spin and negative parity.
Recently, based on ~10 billion J/ψ decays collected with BESIII, the spin-parity quantum numbers of the X(2370) were firstly measured with a complex partial wave analysis. The experimental results, including quantum numbers, mass, production and decay properties, are consistent with the features of the lightest pseudoscalar glueball. This recent study provides direct and strong experimental evidence for X(2370) being a glueball.

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

Link to Join Virtually:
https://meet.google.com/bda-vsem-tuv

9 SEP 2024
11:00 - 12:00

Abstract:

Precise predictions of experimental data at the high energy proton–proton collision are significantly important. Due to the complex nature of proton, where the partons are bound by the strong gluonic force inside the proton, this calculation is not an easy task.
Hence, one cannot calculate the cross section, as simple as, that of the point like particles cross section. Fortunately, the factorization theorem allows us to calculate the cumbersome hadronic differential cross section (DCS) in terms of the elementary partonic cross section, convoluted by the familiar parton distribution functions (PDFs).
In the literature, there can be found different factorization frameworks for calculating the cross section, mostly based on the assumptions of parton behavior inside the proton
, such as the collinear and kt-factorizations (kt is the partonic transverse momentum).
For example, in the collinear factorization, it is assumed that the parton moves collinear to the proton and enters into the hard collision.
Therefore in the collinear factorization theorem, it is supposed that the constituent partons can only have a fraction of the proton momentum, i.e., x,
and these partons do not carry any transverse momentum dependency, i.e. kt.
To describe the distribution of these partons inside the proton, one should use the parton distribution functions (PDFs). However, in the small x limit, the transverse momentum of parton (kt), becomes comparable against the collinear component, i.e., xP (P is the proton momentum). Therefore, the evolution equation of collinear parton, should be generalized by the fact that, parton can also have transverse momentum. This means that the PDFs should have kt dependency. These kt dependent PDFs are called transverse momentum dependent PDFs (TMDs) or unintegrated parton distribution functions (UPDFs).

Link to Join Virtually:
https://meet.google.com/bda-vsem-tuv

28 AUG 2024
11:00 - 12:00

Abstract:

In this talk, I quantify the effects of light spin-zero particles with pseudoscalar couplings to leptons and scalar couplings to nucleons on the evolution of solar neutrinos. I show in this scenario the matter potential sourced by the nucleons in the Sun’s matter gives rise to spin precession of the relativistic neutrino ensemble. For Dirac neutrinos, the spin-flavour precession results in active-sterile oscillations, while for Majorana neutrinos it results in left-handed neutrino to right-handed antineutrino oscillations. In both cases, this leads to distortions in the solar neutrino spectrum which we use to derive constraints on the allowed values of the mediator mass and couplings via a global analysis of the solar neutrino data. In addition for Majorana neutrinos, spin-flavour precession results into a potentially observable flux of solar electron antineutrinos at the Earth which we quantify and constrain with the existing bounds from Borexino and KamLAND.

Indico Link:
https://indico.hep.ipm.ir/e/s.ansarifard1

Link to Join Virtually:
https://meet.google.com/bda-vsem-tuv