Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99


Any time

2020 ( 55 )

2019 ( 650 )

2018 ( 704 )

2017 ( 696 )

Custom range...

Search Results: 1 - 10 of 401462 matches for " M. Campanelli "
All listed articles are free for downloading (OA Articles)
Page 1 /401462
Display every page Item
Physics of W bosons at LEP2
M. Campanelli
Physics , 1999, DOI: 10.1142/S0217751X99001548
Abstract: After the first observations of W bosons in leptonic interactions, about 4000 WW candidate events per experiment have been collected at LEP2. This data allows the measurement of the WW production cross section at different centre-of-mass energies, as well as W decay branching fractions. The W hadronic branching fraction can be converted into a test of the unitarity of the CKM matrix, or into an indirect determination of the matrix element $|V_{cs}|$. A more direct measurement coming from charm tagging is also performed. The W mass has been measured via the cross section (in the threshold region) and the direct reconstruction of the W decay products, using different techniques to account for the distortions due to experimental effects. The main systematic error to the mass reconstruction in the fully hadronic channel comes from QCD effects like Color reconnections and Bose-Einstein correlations, extensively studied in WW events. In $e^+e^-$ collisions W pairs can be produced in s-channel via a three vector boson vertex, so a direct study of the trilinear gauge boson couplings is possible. Modification of WW cross section and distributions of W production and decay angles would be an indication of non-standard couplings, thus a first hint for the presence of new physics.
Making use of geometrical invariants in black hole collisions
J. Baker,M. Campanelli
Physics , 2000, DOI: 10.1103/PhysRevD.62.127501
Abstract: We consider curvature invariants in the context of black hole collision simulations. In particular, we propose a simple and elegant combination of the Weyl invariants I and J, the {\sl speciality index} ${\cal S}$. In the context of black hole perturbations $\cal S$ provides a measure of the size of the distortions from an ideal Kerr black hole spacetime. Explicit calculations in well-known examples of axisymmetric black hole collisions demonstrate that this quantity may serve as a useful tool for predicting in which cases perturbative dynamics provide an accurate estimate of the radiation waveform and energy. This makes ${\cal S}$ particularly suited to studying the transition from nonlinear to linear dynamics and for invariant interpretation of numerical results.
"Are Black Holes in Brans-Dicke Theory precisely the same as in General Relativity?"
M. Campanelli,C. O. Lousto
Physics , 1993, DOI: 10.1142/S0218271893000325
Abstract: We study a three-parameters family of solutions of the Brans-Dicke field equations. They are static and spherically symmetric. We find the range of parameters for which this solution represents a black hole different from the Schwarzschild one. We find a subfamily of solutions which agrees with experiments and observations in the solar system. We discuss some astrophysical applications and the consequences on the "no hair" theorems for black holes.
Second order gauge invariant gravitational perturbations of a Kerr black hole
M. Campanelli,C. O. Lousto
Physics , 1998, DOI: 10.1103/PhysRevD.59.124022
Abstract: We investigate higher than the first order gravitational perturbations in the Newman-Penrose formalism. Equations for the Weyl scalar $\psi_4,$ representing outgoing gravitational radiation, can be uncoupled into a single wave equation to any perturbative order. For second order perturbations about a Kerr black hole, we prove the existence of a first and second order gauge (coordinates) and tetrad invariant waveform, $\psi_I$, by explicit construction. This waveform is formed by the second order piece of $\psi_4$ plus a term, quadratic in first order perturbations, chosen to make $\psi_I$ totally invariant and to have the appropriate behavior in an asymptotically flat gauge. $\psi_I$ fulfills a single wave equation of the form ${\cal T}\psi_I=S,$ where ${\cal T}$ is the same wave operator as for first order perturbations and $S$ is a source term build up out of (known to this level) first order perturbations. We discuss the issues of imposition of initial data to this equation, computation of the energy and momentum radiated and wave extraction for direct comparison with full numerical approaches to solve Einstein equations.
Efeitos de épocas e de modos de aplica??o do sulfato de am?nio- 15N e intera??o nitrogênio - 15N - fósforo - 32P, na quantidade e teores de N, P, K na planta e na folha do milho, na produ??o, na quantidade de proteína e eficiência do nitrogênio do fertilizante convertido em proteína
Neptune, André M. Louis;Campanelli, Antonio;
Anais da Escola Superior de Agricultura Luiz de Queiroz , 1980, DOI: 10.1590/S0071-12761980000200030
Abstract: the experiment herein described was carried on a podzolic soil, in the state of s?o paulo, brazil with the double hybrid corn hd-6999b. the following conclusions were drawn: 1 - in respect of placement and times of application of superphosphate-32p and ammonium sulfate-15n the data showed that: a) greater yield and fair quantity of protein were obtained when the nitrogen and phosphorus were mixed and applied in banding at seeding time; b) lower yield and lower quantity of protein were obtained when phosphorus and applied in banding and nitrogen applied at side-dressing, 83 days after seeding; c) phosphorus application in banding and nitrogen application in side-dressing, 63 days afeter seeding, gave a fair yield and a higher quantity of protein and a higher efficiency of nitrogen of the fertilizer in its conversion into protein. 2 - in respect of % fppf, it seemed there was an effect of nh? on phosphorus uptake, but this effect disapeared at 63 days after seeding. regarding the % nppf, there was also an effect of phosphorus on nitrogen uptake, but of short duration. 3 - the corn plants still continue to take up the nitrogen of the fertilizer even at 73 and 83 days after seeding, not to increase yield, but to increase the contents and quantity of protein. 4 - the maize leaf +2 can be taken for analisys at 73 days after seeding as an indicator of the nutritional status of maize plant in nitrogen and phosphorus. in the case of potassium, the leaf will be taken for analisys at 117 days after seeding. 5 - the superphosphate at the level applied constituted a limiting factor for better yield.
Perturbative Metric of Charged Black Holes in Quadratic Gravity
M. Campanelli,C. O. Lousto,J. Audretsch
Physics , 1994, DOI: 10.1103/PhysRevD.51.6810
Abstract: We consider perturbative solutions to the classical field equations coming from a quadratic gravitational lagrangian in four dimensions. We study the charged, spherically symmetric black hole and explicitly give corrections up to third order (in the coupling constant $\beta$ multiplying the $R_{\mu\nu}R^{\mu\nu}$ term) to the Reissner--Nordstr\"om hole metric. We consider the thermodynamics of such black holes, in particular, we compute explicitly its temperature and entropy--area relation which deviates from the usual $S=A/4$ expression.
A Perturbative Method to solve fourth-order Gravity Field Equations
M. Campanelli,C. O. Lousto,J. Audretsch
Physics , 1994, DOI: 10.1103/PhysRevD.49.5188
Abstract: We develop a method for solving the field equations of a quadratic gravitational theory coupled to matter. The quadratic terms are written as a function of the matter stress tensor and its derivatives in such a way to have, order by order, a set of Einstein field equations with an effective $T_{\mu\nu}$. We study the cosmological scenario recovering the de Sitter exact solution, and the first order (in the coupling constants $\alpha$ and $\beta$ appearing in the gravitational Lagrangian) solution to the gauge cosmic string metric and the charged black hole. For this last solution we discuss the consequences on the thermodynamics of black holes, and in particular, the entropy - area relation which gets additional terms to the usual ${1\over4} A$ value.
Long baseline neutrino oscillation disappearance search using a $ν$ beam from muon decays
A. Bueno,M. Campanelli,A. Rubbia
Physics , 1998,
Abstract: We study the feasibility of performing a $\nu_\mu$ disappearance long-baseline experiment using a neutrino beam coming from muon decays. The advantage of such a technique with respect to the production of neutrino beams from pions is that in a muon decay both muon and electron neutrinos are produced in the same quantity. In case of $\nu_\mu\to\nu_{\tau,s}$ oscillations, the $\nu_e$ charged current (CC) events can be used as a control sample, to predict in situ the $\nu_\mu$ rates, thus reducing the systematics due to the knowledge of the neutrino flux, which is the main source of uncertainties for disappearance experiments. We consider as our neutrino target, the ICARUS detector in its final mass configuration of 4.8 kton.
Physics potential at a neutrino factory: can we benefit from more than just detecting muons?
A. Bueno,M. Campanelli,A. Rubbia
Physics , 2000, DOI: 10.1016/S0550-3213(00)00539-3
Abstract: In order to fully address the oscillation processes at a neutrino factory, a detector should be capable of identifying and measuring all three charged lepton flavors produced in charged current interactions {\it and} of measuring their charges to discriminate the incoming neutrino helicity. This is an experimentally challenging task, given the required detector mass for long-baseline experiments. We address the benefit of a high-granularity, excellent-calorimetry non-magnetized target-detector, which provides a background-free identification of electron neutrino charged current and a kinematical selection of tau neutrino charged current interactions. We assume that charge discrimination is only available for muons reaching an external magnetized-Fe spectrometer. This allows the clean classification of events into electron, right-sign muon, wrong-sign muon and no-lepton categories. In addition, high granularity permits a clean detection of quasi-elastic events, which by detecting the final state proton, provide a selection of the neutrino electron helicity without the need of an electron charge measurement. From quantitative analyses of neutrino oscillation scenarios, we conclude that in many cases the discovery sensitivities and the measurements of the oscillation parameters are dominated by the ability to measure the muon charge. However, we identify cases where identification of electron and tau samples contributes significantly.
Three-family oscillations using neutrinos from muon beams at very long baseline
M. Campanelli,A. Bueno,A. Rubbia
Physics , 1999,
Abstract: The planned LBL experiments will be able to prove the hypothesis of flavor oscillation between muon and tau neutrinos. We explore the possibility of a second generation long baseline experiment at very long baseline, i.e. L in the range 5000-7000 km. This distance requires intense neutrino beams that could be available from very intense muon beams as those needed for $\mu$ colliders. Such baselines allow the study of neutrino oscillations with $E/L \approx 2\times 10^{-3} eV^2$ with neutrinos of energy $E_\nu \approx 10 GeV$, i.e. above tau threshold. Moreover, matter effects inside the Earth could lead to observable effects in $\nu_e \to \nu_\mu$ oscillations. These effects are interchanged between neutrinos and antineutrinos, and therefore they can be tested by comparing the oscillated spectra obtained running the storage ring with positive and negative muons.
Page 1 /401462
Display every page Item

Copyright © 2008-2017 Open Access Library. All rights reserved.