National University of La Plata

About: National University of La Plata is a education organization based out in La Plata, Argentina. It is known for research contribution in the topics: Population & Large Hadron Collider. The organization has 12993 authors who have published 30013 publications receiving 495118 citations. The organization is also known as: UNLP & Universidad Nacional de La Plata.

Calibration errors on experimental slant total electron content (TEC) determined with GPS

Abstract: The Global Positioning System (GPS) has become a powerful tool for ionospheric studies. In addition, ionospheric corrections are necessary for the augmentation systems required for Global Navigation Satellite Systems (GNSS) use. Dual-frequency carrier-phase and code-delay GPS observations are combined to obtain ionospheric observables related to the slant total electron content (sTEC) along the satellite-receiver line-of-sight (LoS). This observable is affected by inter-frequency biases [IFB; often called differential code biases (DCB)] due to the transmitting and the receiving hardware. These biases must be estimated and eliminated from the data in order to calibrate the experimental sTEC obtained from GPS observations. Based on the analysis of single differences of the ionospheric observations obtained from pairs of co-located dual-frequency GPS receivers, this research addresses two major issues: (1) assessing the errors translated from the code-delay to the carrier-phase ionospheric observable by the so-called levelling process, applied to reduce carrier-phase ambiguities from the data; and (2) assessing the short-term stability of receiver IFB. The conclusions achieved are: (1) the levelled carrier-phase ionospheric observable is affected by a systematic error, produced by code-delay multi-path through the levelling procedure; and (2) receiver IFB may experience significant changes during 1 day. The magnitude of both effects depends on the receiver/antenna configuration. Levelling errors found in this research vary from 1.4 total electron content units (TECU) to 5.3 TECU. In addition, intra-day vaiations of code-delay receiver IFB ranging from 1.4 to 8.8 TECU were detected.

Atmospheric NLTE-models for the spectroscopic analysis of blue stars with winds. II. Line-blanketed models

Abstract: We present new or improved methods for calculating NLTE, line-blanketed model atmospheres for hot stars with winds (spectral types A to O), with particular emphasis on fast performance These methods have been implemented into a previous, more simple version of the model atmosphere code F (Santolaya-Rey et al 1997) and allow us to spec- troscopically analyze large samples of massive stars in a reasonable time-scale, using state-of-the-art physics Although this updated version of the code has already been used in a number of recent investigations, the corresponding methods have not been explained in detail so far, and no rigorous comparison with results from alternative codes has been performed This paper intends to address both topics In particular, we describe our (partly approximate) approach to solve the equations of statistical equilibrium for those elements that are primarily responsible for line-blocking and blanketing, as well as an approximate treatment of the line-blocking itself, which is based on a simple statistical approach using suitable means of line opacities and emissivities Both methods are validated by specific tests Furthermore, we comment on our implementation of a consistent temperature structure In the second part, we concentrate on a detailed comparison with results from two codes used in alternative spectroscopical investigations, namely  (Hillier & Miller 1998) and -Basic (Pauldrach et al 2001) All three codes predict almost identical temperature structures and fluxes for λ> 400 A, whereas at lower wavelengths a number of discrepancies are found Particularly in the He continua, where fluxes and corresponding numbers of ionizing photons react extremely sensitively to subtle differences in the models, we consider any uncritical use of these quantities (eg, in the context of nebula diagnostics) as unreliable Optical H/He lines as synthesized by  are compared with results from , obtaining a remarkable coincidence, except for the He singlets in the temperature range between 36 000 to 41 000 K for dwarfs and between 31 000 to 35 000 K for supergiants, where  predicts much weaker lines Consequences of these discrepancies are discussed Finally, suggestions are presented as to adequately parameterize model-grids for hot stars with winds, with only one additional parameter compared to standard grids from plane-parallel, hydrostatic models

Dimensional renorinalization : The number of dimensions as a regularizing parameter

Abstract: We perform an analytic extension of quantum electrodynamics matrix elements as (analytic) functions of the number of dimensions of space(ν). The usual divergences appear as poles forν integer. The renormalization of those matrix elements (forν arbitrary) leads to expressions which are free of ultraviolet divergences forν equal to 4. This shows thatν can be used as an analytic regularizing parameter with, advantages over the usual analytic regularization method. In particular, gauge invariance is mantained for anyν.

Muon reconstruction performance of the ATLAS detector in proton–proton collision data at √ s =13 TeV

Abstract: This article documents the performance of the ATLAS muon identification and reconstruction using the first LHC dataset recorded at s√ = 13 TeV in 2015. Using a large sample of J/ψ→μμ and Z→μμ decays from 3.2 fb−1 of pp collision data, measurements of the reconstruction efficiency, as well as of the momentum scale and resolution, are presented and compared to Monte Carlo simulations. The reconstruction efficiency is measured to be close to 99% over most of the covered phase space (|η| 2.2, the pT resolution for muons from Z→μμ decays is 2.9% while the precision of the momentum scale for low-pT muons from J/ψ→μμ decays is about 0.2%.