Search results for "Particle physics"
showing 10 items of 6826 documents
Deep-learning based reconstruction of the shower maximum X max using the water-Cherenkov detectors of the Pierre Auger Observatory
2021
The atmospheric depth of the air shower maximum $X_{\mathrm{max}}$ is an observable commonly used for the determination of the nuclear mass composition of ultra-high energy cosmic rays. Direct measurements of $X_{\mathrm{max}}$ are performed using observations of the longitudinal shower development with fluorescence telescopes. At the same time, several methods have been proposed for an indirect estimation of $X_{\mathrm{max}}$ from the characteristics of the shower particles registered with surface detector arrays. In this paper, we present a deep neural network (DNN) for the estimation of $X_{\mathrm{max}}$. The reconstruction relies on the signals induced by shower particles in the groun…
A Telemetry, Tracking, and Command Antennas System for Small-Satellite Applications
2019
Circularly polarized (CP) antennas are used in space applications for telemetry tracking and command (TT&
Spectroscopy of short-lived radioactive molecules
2020
Molecular spectroscopy offers opportunities for the exploration of the fundamental laws of nature and the search for new particle physics beyond the standard model1–4. Radioactive molecules—in which one or more of the atoms possesses a radioactive nucleus—can contain heavy and deformed nuclei, offering high sensitivity for investigating parity- and time-reversal-violation effects5,6. Radium monofluoride, RaF, is of particular interest because it is predicted to have an electronic structure appropriate for laser cooling6, thus paving the way for its use in high-precision spectroscopic studies. Furthermore, the effects of symmetry-violating nuclear moments are strongly enhanced5,7–9 in molecu…
Measurement of the Higgs boson coupling with tau leptons and search for an additional neutral MSSM Higgs boson with the ATLAS detector
2018
El Modelo Estándar de física de partículas (SM), la teoría que describe el comportamiento de las partículas subatómicas, ha sido un éxito en su precisión y exactitud. Uno de sus pilares básicos es el mecanismo de Higgs, que regula los términos de masa de las partículas fundamentales. La partícula responsable de este mecanismo es el bosón de Higgs, que fue descubierto en 2012 en los experimentos ATLAS y CMS del colisionador de partículas LHC del CERN, mediante el análisis de su acoplamiento a partículas bosónicas (fotones y bosones W y Z). Tras su descubrimiento, es necesario confirmar que el resto sus propiedades se corresponden con las predichas por el SM, como, por ejemplo, su acoplamient…
Supersymmetric technicolor
2011
In this thesis, we consider a supersymmetrized version of the Standard Model extended with a technicolor sector. We specialize in the regime of the model in which the technicolor sector is fully responsible of the electroweak symmetry breaking and the natural elementary Higgses of the supersymmetric model only transmit the breaking to the Standard Model fermions, thereby giving them masses. In particular, we consider the vacuum structure of the effective theory, find it to be different to that of a mere technicolor model and study the contributions of the new sector to the oblique electroweak parameters. Relative to the current experimental limits, we find the model viable.
Global analysis of the pMSSM in light of the Fermi GeV excess: prospects for the LHC Run-II and astroparticle experiments
2016
We present a new global fit of the 19-dimensional phenomenological Minimal Supersymmetric Standard Model (pMSSM-19) that comply with all the latest experimental results from dark matter indirect, direct and accelerator dark matter searches. We show that the model provides a satisfactory explanation of the excess of gamma-rays from the Galactic centre observed by the Fermi~Large Area Telescope, assuming that it is produced by the annihilation of neutralinos in the Milky Way halo. We identify two regions that pass all the constraints: the first corresponds to neutralinos with a mass ~80-100 GeV annihilating into WW with a branching ratio of 95% ; the second to heavier neutralinos, with mass ~…
Balitsky-Kovchegov equation
2011
In high-energy particle physics the energy evolution of various quantities can be calculated from the Balitsky-Kovchegov (BK) equation. Depending on the frame that is used to describe the process, the BK equation can be seen to describe either the energy evolution of the virtual photon wave function or the gluon distribution function of a hadron. In this work the BK equation is derived at leading logarithm accuracy from QCD and solved analytically in some special cases. In order to derive it the quantum field theory on the light cone is introduced. Part of the higher order corrections to the BK equation, namely the running strong coupling constant and the kinematical constraint effects, are…
Hadronic light-by-light contribution to $(g-2)_\mu$ from lattice QCD with SU(3) flavor symmetry
2020
We perform a lattice QCD calculation of the hadronic light-by-light contribution to $(g-2)_\mu$ at the SU(3) flavor-symmetric point $m_\pi=m_K\simeq 420\,$MeV. The representation used is based on coordinate-space perturbation theory, with all QED elements of the relevant Feynman diagrams implemented in continuum, infinite Euclidean space. As a consequence, the effect of using finite lattices to evaluate the QCD four-point function of the electromagnetic current is exponentially suppressed. Thanks to the SU(3)-flavor symmetry, only two topologies of diagrams contribute, the fully connected and the leading disconnected. We show the equivalence in the continuum limit of two methods of computin…
Branching Ratios and Spectral Functions of $\tau$ Decays: final ALEPH measurements and physics implications
2005
The full LEP-1 data set collected with the ALEPH detector at the $Z$ pole during 1991-1995 is analysed in order to measure the $\tau$ decay branching fractions. Extensive systematic studies are performed, in order to match the large statistics of the data sample corresponding to over 300 000 measured and identified $\tau$ decays. Branching fractions are obtained for the two leptonic channels and eleven hadronic channels defined by their respective numbers of charged particles and $\pi^0$'s. Using previously published ALEPH results on final states with charged and neutral kaons, corrections are applied to the hadronic channels to derive branching ratios for exclusive final states without kao…
QCD NLO with Powheg matching and top threshold matching in WHIZARD
2016
We present the status of the automation of NLO processes within the event generator WHIZARD. The program provides an automated FKS subtraction and phase space integration over the FKS regions, while the (QCD) NLO matrix element is accessed via the Binoth Les Houches Interface from an externally linked one-loop program. Massless and massive test cases and validation are shown for several e+e- processes. Furthermore, we discuss work in progress and future plans. The second part covers the matching of the NRQCD prediction with NLL threshold resummation to the NLO continuum top pair production at lepton colliders. Both the S-wave and P-wave production of the top pair are taken into account in t…