BSc thesis

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The goal was to search for the charged Higgs boson in real data in LHC. We assumed that the charged Higgs boson decays as follows: H^+ -> H^0W^+ -> l + τ_h + x$. We chose H^+ -> H^0W, as the two-Higgs-doublet model predicts that this is the process with the larger branching ratio, for masses larger than 300 GeV/c^2 and tanβ=3 (or tanβ=30). We started by simulating the event by using a Monte Carlo simulation. We used the simulated data and reconstructed the event, pretending that the data came from real detectors. We did that in order to compare our results with the real data from CMS later on. Finally, we used real data from CMS (2016) with integrated luminosity = 35.8 fb^{-1} and 13 TeV center-of-mass energy. Unfortunately, the simulation showed that 86 % of our signal comes from top-antitop background processes. We fitted the transverse mass of the system on the data, by using the background processes and the signal, and we defined how much signal is allowed into the cross section that we chose.

A photo of myself in the LHCb control room, before Run 3 starts (and getting 100% credits for my 0% contribution)

CERN Summer MSc Studentship 2020 / Muon and electron reconstruction efficiency at LHCb

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The leptons that are produced in the LHCb (especially the electrons), are "suffering" from bremsstrahlung radiation by their interactions with the surrounding material. This leads to a decrease of their momentum and scattering, and therefore to fewer tracks into our detectors. As a result, the reconstruction of these particles becomes more difficult, and in some cases impossible. In my project we studied how the electron and muon reconstruction efficiency changes with respect to the kinematics of the particles, the various kinematic cuts and the track types. In real life experiments, the efficiency of the reconstruction algorithms is defined according to the tag-and-probe method. However, we can not define a priori which is the proper bin size that can be used for the efficiency plots. Therefore, by using simulated data we tried to understand how to optimize the bin size, in order to get as much useful information we can, without having low statistics in each bin.

MSc Thesis & published paper on NSs Mass and radius change universal relations

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Rotation causes an increase in a neutron star's mass and equatorial radius. The mass and radius depend sensitively on the unknown equation of state (EOS) of cold, dense matter. However, the increases in mass and radius due to rotation are almost independent of the EOS. The EOS independence leads to the idea of neutron star universality. In this paper, we compute sequences of rotating neutron stars with constant central density. We use a collection of randomly generated EOSs to construct simple correction factors to the mass and radius computed from the equations of hydrostatic equilibrium for nonrotating neutron stars. The correction factors depend only on the nonrotating star's mass and radius and are almost independent of the EOS. This makes it computationally inexpensive to include observations of rotating neutron stars in EOS inference codes. We also construct a mapping from the measured mass and radius of a rotating neutron star to a corresponding nonrotating star. The mapping makes it possible to construct a zero-spin mass–radius curve if the masses and radii of many neutron stars with different spins are measured. We show that the changes in polar and equatorial radii are symmetric, in that the polar radius shrinks at the same rate in which the equatorial radius grows. This symmetry is related to the observation that the equatorial compactness (the ratio of mass to radius) is almost constant on one of the constant-density sequences.

Effects Of Dark Matter Core On The Rotating Neutron Star’s Structural Universal Relations (Not published yet)

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Neutron stars represent unique laboratories, offering insights into the physics of supranuclear-density matter and serving as potential hosts for dark matter. This study explores the impact of dark matter cores on rapidly rotating neutron stars through the two-fluid approximation, assuming minimal interaction between baryonic matter and dark matter. The investigation employs phenomenological models for fermionic and bosonic dark matter, revealing that universal relations governing mass and radius changes due to rotation remain largely unaffected in the presence of a dark matter core. Specifically, for a 5 % dark matter mass fraction, the percent deviations in total mass ( M_tot), the equatorial radius (R_Be), and polar-to-equatorial radius ratio (R_Bp/R_Be) are within 3.9 %, 1.8 %, and 1.4 %, respectively. These findings suggest that the universal relations governing neutron star shape can be utilized to infer constraints on the properties of dark matter cores.

Νόσος Των Σκεπτόμενων Δυτών

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A small book about physics and life (in Greek) [ISBN:978-9925-581-46-7]

Lympia Texas Villagers Outlaw

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A small fun video game based on my village Lympia in Cyprus. The graphics are created by Evelyn Toumazou.

U.S. του ψουμά

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An Instagram page with stupid puns. The sketches are created by Evelyn Toumazou.