Katerina Zachariadou

University of West Attica | TEIATH · Electrical & Electronics Engineering

The ATLAS experiment at CERN undergoes a series of upgrades, in line with the upgrades (Phase-I and Phase-II) of the Large Hadron Collider (LHC), to cope with the steadily increasing instantaneous luminosity that ultimately is expected to reach 7.5×10 ³⁴ cm ⁻² s ⁻¹ at the High Luminosity LHC (HL-LHC) era. The most challenging upgrade project of the...

In this paper we study the use of Machine Learning techniques to set constraints on indirect signatures of physics beyond the Standard Model in Vector Boson Scattering (VBS), in the electroweak (EWK) production of self-interacting W ± Z bosons in association with two jets. The WZ fully leptonic channel has been extensively studied by the ATLAS Coll...

The main objectives of the KM3NeT Collaboration are (i) the discovery and subsequent observation of high-energy neutrino sources in the Universe and (ii) the determination of the mass hierarchy of neutrinos. These objectives are strongly motivated by two recent important discoveries, namely: (1) the high-energy astrophysical neutrino signal reporte...

Recommendation related to RFK - Eudoxos

The KM3NeT research infrastructure, currently under construction in the Mediterranean Sea, will host neutrino telescopes for the identification of neutrino sources in the Universe and for studies of the neutrino mass hierarchy. These telescopes will house hundreds of thousands of photomultiplier tubes that will have to be operated in a stable and r...

Studying atmospheric neutrino oscillations in the few-GeV range with a multi-megaton detector promises to determine the neutrino mass hierarchy. This is the main science goal pursued by the future KM3NeT/ORCA water Cherenkov detector in the Mediterranean Sea. In this paper, the processes that limit the obtainable resolution in both energy and direc...

The textile fabrics are materials of complex structure because their construction is based on interlaced yarns, which are made of twisted fibres. That complexity of the structure is reflected on their mechanical properties. Very often they are characterized by non-linear mechanical response and non-isotropic behaviour. Thus during the testing of th...

The main objectives of the KM3NeT Collaboration are i) the discovery and subsequent observation of high-energy neutrino sources in the Universe and ii) the determination of the mass hierarchy of neutrinos. These objectives are strongly motivated by two recent important discoveries, namely: 1) The high-energy astrophysical neutrino signal reported b...

Quark and gluon jets with the same energy, 24 GeV, are compared in symmetric three-jet configurations from hadronic Z decays observed by the ALEPH detector. Jets are defined using the Durham algorithm. Gluon jets are identified using an anti-tag on b jets, based on a track impact parameter method. The comparison of gluon and mixed flavour quark jet...

Using about 950000 hadronic events collected during 1991 and 1992 with the ALEPH detector, the ratios r(b) = alpha(s)(b)/alpha(s)(udsc) and r(uds) = alpha(s)(uds)/alpha(s)(cb) have been measured in order to test the flavour independence of the strong coupling constant alpha(s). The analysis is based on event-shape variables using the full hadronic...

A lower limit on the oscillation frequency of the Bs0s0 system is obtained from approximately four million hadronic Z decays accumulated using the ALEPH detector at LEP from 1991 to 1995. Leptons are combined with opposite sign Ds− candidates reconstructed in seven different decay modes as evidence of semileptonic Bs0 decays. Criteria designed to e...

Four candidates for charmless hadronic B decay are observed in a data sample of four million hadronic Z decays recorded by the aleph detector at lep. The probability that these events come from background sources is estimated to be less than 10−6. The average branching ratio of weakly decaying B hadrons (a mixture of Bd0, Bs0 and Λb weighted by the...

Using about 1.5 million hadronic Z decays recorded with the aleph detector, the lifetime of the b baryons has been measured using two independent data samples. From a maximum likelihood fit to the impact parameter distribution of leptons in 519 Λℓ− combinations containing a b baryon sample of 290 decays, the measured b baryon lifetime is τb—baryon...

Single top production via flavour changing neutral currents in the reactions is searched for in approximately 411 pb−1 of data collected by ALEPH at centre-of-mass energies in the range between 189 and 202 GeV. In total, 58 events are selected in the data to be compared with 50.3 expected from Standard Model backgrounds. No deviation from the Stand...

Bose-Einstein correlations are studied in semileptonic () and fully hadronic () W-pair decays with the ALEPH detector at LEP at centre-of-mass energies of 172, 183 and 189 GeV. They are compared with those made at the Z peak after correction for the different flavour compositions. A Monte Carlo model of Bose-Einstein correlations based on the JETSE...

The data collected at a centre-of-mass energy of 188.6 GeV by ALEPH at LEP, corresponding to an integrated luminosity of 173.6 pb(-1), are analysed in a search for the scalar partners of quarks and leptons predicted in supersymmetric models. No evidence for any such particles was found in the decay channels (l) over tilde --> l chi, (t) over tilde...

Radiative returns to the Z resonance (Z gamma events) are used to determine the LEP2 centre-of-mass energy from the data collected with the ALEPH detector in 1997. The average centre-of-mass energy is measured to he: E(CM) = 182.50 +/- 0.19(stat.) +/- 0.08 (syst.) GeV in good agreement with the precise determination by the LEP energy working group...

The reaction e+e− → HZ∗ is used to search for the standard model Higgs boson in the and the Hℓ+ℓ− channels. The data sample corresponds to about 4.5 million hadronic Z decays collected by the ALEPH experiment at LEP from 1989 to 1995 at centre-of-mass energies at and around the Z peak. Three candidate events are found in the Hμ+μ− channel, in agree...

During 1997 the ALEPH experiment at LEP gathered 57 pb(-1) of data at centre-of-mass energies near 183 GeV. These data are used to look for possible signals from the production of the Standard Model Higgs boson in the reaction e(+)e(-) --> HZ. No evidence of a signal is found in the data; seven events are selected, in agreement with the expectation...

Data taken with the ALEPH detector at LEP1 have been used to search for gamma gamma production of the glueball candidates f(0)(1500) and f(j)(1710) via their decay to pi(+)pi(-). No signal is observed and upper limits to the product of gamma gamma width and pi(+)pi(-) branching ratio of the f(0)(1500) and the f(j)(1710) have been measured to be Gam...

Measurements of the subjet structure of quark and gluon jets in hadronic Z decays are presented. The analysis is based on one million hadronic events recorded by the Aleph detector. Roughly symmetric three-jet events are selected with a coarse jet-resolution cut-off, y1. Gluon jets are identified with a purity of 94.6% in those events where evidenc...

The data recorded by the ALEPH experiment at LEP at centre-of-mass energies of 161 GeV and 172 GeV were analysed to search for sleptons, the supersymmetric partners of leptons. No evidence for the production of these particles was found. The number of candidates observed is consistent with the background expected from four-fermion processes and γγ-...

Searches for supersymmetric particles produced in e+e− interactions at the Z peak have been performed under the assumptions that R-parity is not conserved, that the dominant R-parity violating coupling involves only leptonic fields, and that the lifetime of the lightest supersymmetric particle can be neglected. In a data sample collected by the ALE...

Searches for neutral Higgs bosons are performed with the 237 pb−1 of data collected in 1999 by the ALEPH detector at LEP, for centre-of-mass energies between 191.6 and 201.6 GeV. These searches apply to Higgs bosons within the context of the Standard Model and its minimal supersymmetric extension (MSSM) as well as to invisibly decaying Higgs bosons...

In a data sample of four million hadronic Z decays collected with the ALEPH detector at LEP, four Λb baryon candidates are exclusively reconstructed in the Λb → Λc+π− channel, with the Λc+ decaying into pK−π+, , or Λπ+π+π−. The probability of the observed signal to be due to a background fluctuation is estimated to be 4.2 × 10−4. The mass of the Λb...

An improved measurement of the average b hadron lifetime is performed using a sample of 1.5 million hadronic Z decays, collected during the 1991–1993 runs of ALEPH, with the silicon vertex detector fully operational. This uses the three-dimensional impact parameter distribution of lepton tracks coming from semileptonic b decays and yields an averag...

The fragmentation of b quarks into B mesons is studied with four million hadronic Z decays collected by the ALEPH experiment during the years 1991–1995. A semi-exclusive reconstruction of B→ℓνD(★) decays is performed, by combining lepton candidates with fully reconstructed D(★) mesons while the neutrino energy is estimated from the missing energy o...

The decay is reconstructed with J/ψ→e+e− or μ+μ− and K0S→π+π−. From the full ALEPH dataset at LEP1 of about 4 million hadronic Z decays, 23 candidates are selected with an estimated purity of 71%. They are used to measure the CP asymmetry of this decay, given by sin2β in the Standard Model, with the result . This is combined with existing measureme...

A lower limit is set on the Bs0 meson oscillation parameter Δms using data collected from 1991 to 1994 by the ALEPH detector. Events with a high transverse momentum lepton and a reconstructed secondary vertex are used. The high transverse momentum leptons are produced mainly by b hadron decays, and the sign of the lepton indicates the particle/anti...

Using a sample of about 1.46 million hadronic Z decays collected between 1991 and 1993 with the ALEPH detector at LEP, the energy distribution of the B0 and B± mesons produced at the Z resonance is measured by reconstructing semileptonic decays B → ℓνℓD(X) or . The charmed mesons are reconstructed through the decay modes D0 → K−π+, D0 → K−π+π−π+, D...

The branching fraction for D0 → K−π+ is measured with the statistics collected by ALEPH from 1991 to 1994. The method is based on the comparison between the rate for the reconstructed , D0 → K−π+ decay chain and the rate for inclusive soft pion production at low transverse momentum with respect to the nearest jet. The result is B(D0 → K−π+0 = (3.90...

A study of scaling violations in fragmentation functions performed by the ALEPH collaboration at LEP is presented. Data samples enriched in uds, c, b and gluon jets, respectively, together with measurements of the longitudinal and transverse inclusive cross sections are used to extract the fragmentation function for the gluon and for each flavour....

The lifetimes of theB 0 andB + mesons have been measured with theAleph detector at LEP, using approximately 3 million hadronic Z decays collected in the period 1991–1994. In the first of three methods, semileptonic decays ofB 0 andB + mesons were partially reconstructed by identifying events containing a lepton with an associatedD*− or\(\bar D^0 \)...

The purely leptonic decays Ds → τν and Ds → μν are studied in a sample of four million hadronic Z decays collected with the ALEPH detector at the LEP e+e− collider from 1991 to 1995. The branching fractions are extracted from a combination of two analyses, one optimized to select Ds → τν decays with τ → eνν ̄ or μνν ̄, and the other optimized for D...

A search for the pseudoscalar meson η b is performed in two-photon interactions at LEP 2 with an integrated luminosity of 699 pb −1 collected at e + e − centre-of-mass energies from 181 GeV to 209 GeV. One candidate event is found in the six-charged-particle final state and none in the four-charged-particle final state, in agreement with the total...

The mass of the W boson is determined from the direct reconstruction of W decays in WW → q¯ qq¯ q and WW → ℓνq¯ q events in e + e − collisions at LEP. The data sample corresponds to an integrated luminosity of 683 pb −1 collected with the ALEPH detector at centre-of-mass energies up to 209 GeV. To minimise any effect from colour reconnection a new...

The first prototype of a photo-detection unit of the future KM3NeT neutrino telescope has been deployed in the deep waters of the Mediterranean Sea. This digital optical module has a novel design with a very large photocathode area segmented by the use of 31 three inch photomultiplier tubes. It has been integrated in the ANTARES detector for in-sit...

We present a laboratory over the internet aiming to assist undergraduate students of natural sciences and engineering disciplines to enhance their understanding on the statistical analysis of measurements. The laboratory is implemented through an inexpensive, student-friendly and flexible system consisting of a radiation sensor, a data acquisition...

From a sample of 152,000 τ decays collected by the ALEPH detector at LEP an upper limit of 24 MeV at 95% CL on the τ neutrino mass has been determined. The limit is obtained using a two dimensional likelihood fit of the visible energy and the invariant mass distribution of 25 τ → 5π(π0)ντ events.

An improved measurement of the forward-backward asymmetry in decays is presented, based on a sample of 4.1 million hadronic Z decays collected by ALEPH between 1991 and 1995. Data are analysed as a function of polar angle of the event axis and b purity. The event tagging efficiency and mean b-jet hemisphere charge are measured directly from data. F...

Starting from a sample of four million hadronic Z decays collected with the ALEPH detector at LEP, 404 charged and neutral B mesons are fully reconstructed and used to look for resonant structure in the Bπ system. An excess of events is observed above the expected background in the Bπ mass spectrum at a mass ≈5.7 GeV/c2, consistent with the product...

The data collected at centre-of-mass energies of 188.6 GeV by ALEPH at LEP, corresponding to an integrated luminosity of 176.2 pb−1, are analysed in a search for pair-produced charged Higgs bosons H±. Three analyses are employed to select the , and final states. No evidence for a signal is found. Upper limits are set on the production cross section...

The flavour changing neutral current decay b --> s gamma has been detected in hadronic Z decays collected by ALEPH at LEP. The signal is isolated in lifetime-tagged b (b) over bar events by the presence of a hard photon associated with a system of high momentum and high rapidity hadrons. The background processes are normalised from the data themsel...

The mass of the W boson is obtained from reconstructed invariant mass distributions in W-pair events. The sample of W pairs is selected from 10.65 pb−1 collected with the ALEPH detector at a mean centre-of-mass energy of 172.09 GeV. The invariant mass distribution of simulated events are fitted to the experimental distributions and the following W...

The inclusive production of the η and ω(782) mesons is measured in the π+π−π0 decay mode in hadronic Z decays and compared to model predictions. The analysis is based on 4 million hadronic Z decays recorded by the ALEPH detector between 1991 and 1995. The η production rate for xp=pmeson/pbeam>0.10 is found to be 0.355±0.011stat±0.024sys per event,...

Searches for supersymmetric particles produced in e+e− collisions at centre-of-mass energies of 130 and 136 GeV have been performed in a data sample of 5.7 pb−1 collected in the autumn of 1995 by the ALEPH detector at LEP. No candidate events were found, allowing limits to be set on the masses and production cross-sections of scalar leptons, scalar...

A study of events with photons and missing energy has been performed with the data sample obtained with the ALEPH detector at centre-of-mass energies from 161 to 184 GeV, corresponding to a total integrated luminosity of about 80 pb−1. The measured distributions are in agreement with Standard Model predictions, leading to constraints on WWγ gauge c...

A search for pair production of new heavy leptons has been performed assuming different scenarios for the mixing of the new particles with Standard Model leptons. No candidate events were found in a data sample corresponding to an integrated luminosity of 5.6 pb−1 collected by the ALEPH detector at centre-of-mass energies of 130 and 136 GeV. New li...

Data collected at centre-of-mass energies from 189 GeV to 202 GeV by the ALEPH detector at LEP corresponding to an integrated luminosity of 411 pb(-1), are analysed in a search for the scalar top in the decay channels (t) over tilde --> c/u chi for small mass differences between the stop and the lightest neutralino. No evidence for deviations from...

A search for charginos nearly mass degenerate with the lightest neutralino is performed with the data collected by the ALEPH detector at LEP, at centre-of-mass energies between 189 and 209 GeV, corresponding to an integrated luminosity of 628 pb−1. The analysis is based on the detection of isolated and energetic initial state radiation photons, pro...

The data collected at centre-of-mass energies ranging from 130 to 172 GeV by ALEPH at LEP, corresponding to an integrated luminosity of 27.5 pb−1, are analysed in a search for pair-produced charged Higgs bosons H±. Three analyses are employed to select the , and final states. No evidence for a signal is found. Mass limits are set as a function of t...

A search for γγ decays of a Higgs boson is performed in the data sample collected at LEP with the ALEPH detector between 1991 and 1999. This corresponds to an integrated luminosity of 672 pb−1 at centre-of-mass energies ranging from 88 to 202 GeV. The search is based on topologies arising from a Higgs boson produced in association with a fermion pa...

The e+e−→W+W− cross section is measured in a data sample collected by ALEPH at a mean centre-of-mass energy of 172.09 GeV, corresponding to an integrated luminosity of 10.65 pb−1. Cross sections are given for the three topologies, fully leptonic, semi-leptonic and hadronic of a W-pair decay. Under the assumption that no other decay modes are presen...

Searches for charginos and neutralinos produced in e+e− collisions at centre-of-mass energies of 130 and 136 GeV have been performed under the assumptions that R-parity is not conserved, that the dominant R-parity violating coupling involves only leptonic fields, and that the lifetime of the lightest supersymmetric particle can be neglected. In the...

The mass of the W boson is obtained from reconstructed invariant mass distributions in W-pair events. The sample of W pairs is selected from 57 pb−1 collected with the ALEPH detector in 1997 at a centre-of-mass energy of 183 GeV. The invariant mass distributions of reweighted Monte Carlo events are fitted separately to the experimental distribution...

The triple gauge-boson couplings, alpha(W phi), alpha(W) and alpha(B psi), have been measured using 34 semileptonically and 54 hadronically decaying W(+)W(-) candidate events. The events were selected in the data recorded during 1996 with the ALEPH detector at 172 GeV, corresponding to an integrated luminosity of 10.65 pb(-1). The triple gauge-boso...

The four LEP collaborations, ALEPH, DELPHI, L3 and OPAL, have searched for pair-produced charged Higgs bosons in the framework of Two Higgs Doublet Models (2HDMs). The data of the four experiments have been statistically combined. The results are interpreted within the 2HDM for Type I and Type II benchmark scenarios. No statistically significant ex...

The lifetime of the Bs0 meson is measured in approximately 3 million hadronic Z decays accumulated using the ALEPH detector at LEP from 1991 to 1994. Seven different Ds− decay modes were reconstructed and combined with an opposite sign lepton as evidence of semileptonic Bs0 decays. Two hundred and eight Ds−ℓ+ candidates satisfy selection criteria d...

The B0 - B̄0 average mixing parameter and b forward-backward asymmetry AFB0(b) are measured from a sample of about 4 200 000 Z → qq̄ events recorded with the ALEPH detector at LEP in the years 1990–1995. High transverse momentum electrons and muons produced in b semileptonic decays provide the tag of the quark flavour and of its charge.The average...

Using data obtained with the ALEPH detector at the Z resonance, a measure based on transverse momentum is shown to exhibit a correlation between the two halves of a hadronic event which cannot be explained by energy-momentum conservation, flavour conservation, the imposition of an event axis or imperfect event reconstruction. Two possible explanati...

We present a low-cost, fully computer-controlled, Arduino-based, educational laboratory (SolarInsight) to be used in undergraduate university courses concerned with electrical engineering and physics. The major goal of the system is to provide students with the necessary instrumentation, software tools and methodology in order to learn fundamental...

PoS(HEP2005)022 The CERN Axion Solar Telescope (CAST) is searching for axions produced in the Sun’s core by the Primakoff process. CAST is using a decommissioned Large Hadron Collider (LHC) test

We present results on the reconstructed image resolution of a position sensitive radiation instrument (COCAE) based on extensive simulation studies. The reconstructed image resolution has been investigated in a wide range of incident photon energies emitted by point-like sources located at different source-to-detector distances on and off the detec...

The COCAE project develops an instrument for localization and identification of radioactive sources. For the localization task it will exploit the Compton scattered photons within its detecting layers. It is based on pixilated Cd(Zn)Te matrices in a stacked configuration. Progress has been achieved in all the components necessary for this technolog...

Simulation studies are presented regarding the performance of algorithms that localize point-like radioactive sources detected by a position sensitive portable radiation instrument (COCAE). The source direction is estimated by using the List Mode Maximum Likelihood Expectation Maximization (LM-ML-EM) imaging algorithm. Furthermore, the source-to-de...

Extensive simulations of a portable radiation detecting system have been performed in order to explore important performance parameters. The instrument consists of a stack of ten detecting layers made of pixelated Cadmium Telluride (CdTe) crystals. Its aim is to localize and identify radiation sources, by exploiting the Compton imaging technique. I...

The four-jet final state is analyzed to search for hadronic decays of pair-produced heavy particles. The analysis uses the ALEPH data collected at LEP in November 1995 at centre-of-mass energies of 130 and 136~GeV, corresponding to a total integrated luminosity of 5.7~\inpb. An excess of four-jet events is observed with respect to the standard mode...

Spectroscopic measurements are presented using the PID350 pixelated gamma radiation detectors. A high-speed data acquisition system has been developed in order to reduce the data loss during the data reading in case of a high flux of photons. A data analysis framework has been developed in order to improve the resolution of the acquired energy spec...

The COCAE project develops an instrument for localization and identification of radioactive sources. For the localization task it will exploit the Compton scattered photons within its detecting layers. It is based on pixilated Cd(Zn)Te matrices in a stacked configuration. Progress has been achieved in all the components necessary for this technolog...

Spectroscopic measurements are presented using the PID350 pixelated gamma radiation detectors. A high-speed data acquisition system has been developed in order to reduce the data loss during the data reading in case of a high flux of photons. A data analysis framework has been developed in order to improve the resolution of the acquired energy spec...

Simulation studies and spectroscopic measurements are presented regarding the development of a pixel multilayer CdTe detector under development in the context of the COCAE project. The instrument will be used for the localization and identification of radioactive sources and radioactively contaminated spots. For the localization task the Compton ef...