Search results for "COSMOLOGY"
showing 10 items of 2905 documents
Radio signatures from encounters between neutron stars and QCD-axion minihalos around primordial black holes
2021
Probing the QCD axion dark matter (DM) hypothesis is extremely challenging as the axion interacts very weakly with Standard Model particles. We propose a new avenue to test the QCD axion DM via transient radio signatures coming from encounters between neutron stars (NSs) and axion minihalos around primordial black holes (PBHs). We consider a general QCD axion scenario in which the PQ symmetry breaking occurs before (or during) inflation coexisting with a small fraction of DM in the form of PBHs. The PBHs will unavoidably acquire around them axion minihalos with the typical length scale of parsecs. The axion density in the minihalos may be much higher than the local DM density, and the prese…
Dark matter and baryogenesis in Higgs portal models
2016
This work focuses on two of the main issues in current understanding of particle physics described by the Standard Model. The Standard Model, despite of its success, is not complete. Existence of dark matter has been clearly verified, but its nature is unknown. Also, the baryon asymmetry in the Universe hints that the Standard Model has to be extended. In this thesis we study Higgs portal models which both contain dark matter candidates, and can provide for a successful production of the baryon asymmetry.
A giant planet beyond the snow line in microlensing event OGLE-2011-BLG-0251
2013
We present the analysis of the gravitational microlensing event OGLE-2011-BLG-0251. This anomalous event was observed by several survey and follow-up collaborations conducting microlensing observations towards the Galactic Bulge. Based on detailed modelling of the observed light curve, we find that the lens is composed of two masses with a mass ratio q=1.9 x 10^-3. Thanks to our detection of higher-order effects on the light curve due to the Earth's orbital motion and the finite size of source, we are able to measure the mass and distance to the lens unambiguously. We find that the lens is made up of a planet of mass 0.53 +- 0.21,M_Jup orbiting an M dwarf host star with a mass of 0.26 +- 0.…
The relationship between visible light emission and species fraction of the hydrogen ion beams extracted from 2.45 GHz microwave discharge.
2015
The relationship between Balmer-α and Fulcher-band emissions with extracted H + , H + 2 , and H + 3 ions is demonstrated for a 2.45 GHz microwave discharge. Ion mass spectra and optical measurements of Balmer-α and Fulcher-band emissions have been obtained with a Wien Filter having an optical viewport on the plasma chamber axis. The beam of approximately 1 mA is analyzed for different plasma conditions simultaneously with the measurement of light emissions both with temporal resolution. The use of visible light emissions as a valuable diagnostic tool for monitoring the species fraction of the extracted beams is proposed. peerReviewed
The Hamburg/ESO R-process Enhanced Star survey (HERES)
2004
We report on a dedicated effort to identify and study metal-poor stars strongly enhanced in r-process elements ([r/Fe] > 1 dex; hereafter r-II stars), the Hamburg/ESO R-process Enhanced Star survey (HERES). Moderate-resolution (~2A) follow-up spectroscopy has been obtained for metal-poor giant candidates selected from the Hamburg/ESO objective-prism survey (HES) as well as the HK survey to identify sharp-lined stars with [Fe/H] < -2.5dex. For several hundred confirmed metal-poor giants brighter than B~16.5mag (most of them from the HES), ``snapshot'' spectra (R~20,000; S/N~30 per pixel) are being obtained with VLT/UVES, with the main aim of finding the 2-3% r-II stars expected to be a…
Insight into particle production mechanisms via angular correlations of identified particles in pp collisions at √s = 7 TeV
2017
Two-particle angular correlations were measured in pp collisions at s√=7 TeV for pions, kaons, protons, and lambdas, for all particle/anti-particle combinations in the pair. Data for mesons exhibit an expected peak dominated by effects associated with mini-jets and are well reproduced by general purpose Monte Carlo generators. However, for baryon–baryon and anti-baryon–anti-baryon pairs, where both particles have the same baryon number, a near-side anti-correlation structure is observed instead of a peak. This effect is interpreted in the context of baryon production mechanisms in the fragmentation process. It currently presents a challenge to Monte Carlo models and its origin remains an op…
Quantum aspects originated by Gravitation: from cosmology to astrophysics
2018
El estudio de campos cuánticos que se propagan en espacio-tiempos clásicos, curvos y dinámicos, ofrece una primera manera de evaluar las consecuencias de la teoría cuántica cuando los fenómenos gravitatorios no son despreciables. Esta es una cuestión importante que debe ser abordada cuando un campo gravitatorio intenso juega un papel principal en la dinámica de un sistema físico, tal como ocurre durante el universo temprano (inflación cósmica) o en la formación de agujeros negros astrofísicos. Una de las características más sorprendentes de esta materia es quizás el hecho de que el cálculo de observables físicos, incluso para campos sin interacción, frecuentemente involucra operadores cuadr…
Investigating the Structure of Vela X
2018
Vela X is the prototypical example of a pulsar wind nebula whose morphology and detailed structure have been affected by the interaction with the reverse shock of its host supernova remnant. The resulting complex of filamentary structure and mixed-in ejecta embedded in a nebula that is offset from the pulsar provides the best example we have of this middle-age state that characterizes a significant fraction of composite SNRs, and perhaps all of the large-diameter PWNe seen as TeV sources. Here we report on an XMM-Newton Large Project study of Vela X, supplemented by additional Chandra observations. Through broad spectral modeling as well as detailed spectral investigations of discrete emiss…
"Table 18" of "Search for heavy resonances decaying to a photon and a hadronically decaying $Z/W/H$ boson in $pp$ collisions at $\sqrt{s}=13$ $\mathr…
2018
The 95% CL upper limits on cross section times branching ratio for spin-1 resonance decaying to Hgamma.
"Table 1.7" of "Probing the effects of strong electromagnetic fields with charge-dependent directed flow in Pb-Pb collisions at the LHC"
2020
Slope Dv1 charged hadrons 540%