Effectiveness-ntu computation with a mathematical model for cross-flow heat exchangers

Due to the wide range of design possibilities, simple manufactured, low maintenance and low cost, cross-flow heat exchangers are extensively used in the petroleum, petrochemical, air conditioning, food storage, and others industries. In this paper a mathematical model for cross-flow heat exchangers with complex flow arrangements for determining epsilon -NTU relations is presented. The model is based on the tube element approach, according to which the heat exchanger outlet temperatures are obtained by discretizing the coil along the tube fluid path. In each cross section of the element, tube-side fluid temperature is assumed to be constant because the heat capacity rate ratio C*=Cmin/Cmax tends toward zero in the element. Thus temperature is controlled by effectiveness of a local element corresponding to an evaporator or a condenser-type element. The model is validated through comparison with theoretical algebraic relations for single-pass cross-flow arrangements with one or more rows. Very small relative errors are obtained showing the accuracy of the present model. epsilon -NTU curves for several complex circuit arrangements are presented. The model developed represents a useful research tool for theoretical and experimental studies on heat exchangers performance.

HEAVY-LEPTON PRODUCTION IN THE MINIMAL SUPERSYMMETRIC STANDARD MODEL

We study the production of a charged-heavy-lepton pair considering the minimal supersymmetric standard model. We show that the cross section for the process pp --> gg --> l+l- is enhanced for large values of the ratio between the two-Higgs-doublet vacuum expectation values, in comparison with the standard model result. The gluon fusion mechanism is the most important contribution to the lepton pair production for M(l) > 50 GeV.

Glueballs in peripheral heavy-ion collisions

We estimate the cross-section for glueball production in peripheral heavy-ion collisions through two-photon and double-Pomeron exchange, at energies that will be available at RHIC and LHC. Glueballs will be produced at large rates, opening the possibility to study decays with very small branching ratios. In particular, we discuss the possibility of observing the subprocess γγ(PP) → G → γγ.

The action for the (propagating) torsion and the limits on the torsion parameters from present experimental data

Starting from the well established form of the Dirac action coupled to the electromagnetic and torsion field we find that there is some additional softly broken local symmetry associated with torsion. This symmetry fixes the form of divergences of the effective action after the spinor fields are integrated out. Then the requirement of renormalizability fixes the torsion field to be equivalent to some massive pseudovector and its action is fixed with accuracy to the values of coupling constant of torsion-spinor interaction, mass of the torsion and higher derivative terms. Implementing this action into the abelian sector of the Standard Model we establish the upper bounds on the torsion mass and coupling. In our study we used results of present experimental limits on four-fermion contact interaction (LEP, HERA, SLAC, SLD, CCFR) and TEVATRON limits on the cross section of new gauge boson, which could be produced as a resonance at high energy pp̄ collisions. © 1998 Elsevier Science B.V. All rights reserved.

Torsion action and its possible observables

The methods of effective field theory are used to explore the theoretical and phenomenological aspects of the torsion field. The spinor action coupled to the electromagnetic field and torsion possesses an additional softly broken gauge symmetry. This symmetry enables one to derive the unique form of the torsion action compatible with unitarity and renormalizability. It turns out that the antisymmetric torsion field is equivalent to a massive axial vector field. The introduction of scalars leads to serious problems which are revealed after the calculation of the leading two-loop divergences. Thus the phenomenological aspects of torsion may be studied only for the fermion-torsion systems. In this part of the paper we obtain upper bounds for the torsion parameters using present experimental data on forward-backward Z-pole asymmetries, data on the experimental limits on four-fermion contact interaction (LEP, HERA, SLAC, SLD, CCFR) and also TEVATRON limits on the cross section of a new gauge boson, which could be produced as a resonance at high energy pp collisions. The present experimental data enable one to put limits on the torsion parameters for the various ranges of the torsion mass. We emphasize that for a torsion mass of the order of the Planck mass no independent theory for torsion is possible, and one must directly use string theory. © 1999 Elsevier Science B.V.

Gluon saturation and proton - Anti-proton cross sections

We study proton - anti-proton cross sections in the framework of an updated minijet eikonal model. We propose a different scheme for fixing the parameters, in which we make use of the measured minijet cross section. We compare the results obtained with the GRV98, MRST98, CTEQ6-L and KLN gluon distributions. The latter includes gluon saturation effects. We conclude that in the very high energy regime the use of the KLN distribution improves significantly the behavior of the cross sections. However this improvement is due to the shape of the KLN gluon density and has little to do with saturation effects.

Search for Randall-Sundrum gravitons with 1 fb(-1) of data from p(p)over-bar collisions at root s=1.96 TeV

We search for decays of Kaluza-Klein excitations of the graviton in the Randall-Sundrum model of extra dimensions to e+e- and in 1 fb-1 of pp collisions at s=1.96 TeV collected by the D0 detector at the Fermilab Tevatron. We set 95% confidence level upper limits on the production cross section times branching fraction, which translate into lower limits on the mass of the lightest excitation between 300 and 900 GeV for values of the coupling k/M Pl between 0.01 and 0.1. © 2008 The American Physical Society.

Search for W H associated production in 5.3 fb(-1) of p(p)over-bar collisions at the Fermilab Tevatron

We present a search for associated production of Higgs and W bosons in pp̄ collisions at a center of mass energy of s=1.96 TeV in 5.3 fb-1 of integrated luminosity recorded by the D0 experiment. Multivariate analysis techniques are applied to events containing one lepton, an imbalance in transverse energy, and one or two b-tagged jets to discriminate a potential WH signal from Standard Model backgrounds. We observe good agreement between data and expected backgrounds, and set an upper limit of 4.5 (at 95% confidence level and for mH=115 GeV) on the ratio of the WH cross section multiplied by the branching fraction of H→bb̄ to its Standard Model prediction, which is consistent with an expected limit of 4.8. © 2011 Elsevier B.V.

Measuring and analyzing color and texture information in anatomical leaf cross sections: An approach using computer vision to aid plant species identification

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Combined search for the standard model Higgs boson decaying to bb̄ using the D0 run II data set

We present the results of the combination of searches for the standard model Higgs boson produced in association with a W or Z boson and decaying into bb̄ using the data sample collected with the D0 detector in pp̄ collisions at √s=1.96TeV at the Fermilab Tevatron Collider. We derive 95% C.L. upper limits on the Higgs boson cross section relative to the standard model prediction in the mass range 100GeV≤M H≤150GeV, and we exclude Higgs bosons with masses smaller than 102 GeV at the 95% C.L. In the mass range 120GeV≤M H≤145GeV, the data exhibit an excess above the background prediction with a global significance of 1.5 standard deviations, consistent with the expectation in the presence of a standard model Higgs boson. © 2012 American Physical Society.

Search in leptonic channels for heavy resonances decaying to long-lived neutral particles

A search is performed for heavy resonances decaying to two long-lived massive neutral particles, each decaying to leptons. The experimental signature is a distinctive topology consisting of a pair of oppositely charged leptons originating at a separated secondary vertex. Events were collected by the CMS detector at the LHC during pp collisions at √s = 7 TeV, and selected from data samples corresponding to 4.1 (5.1) fb-1 of integrated luminosity in the electron (muon) channel. No significant excess is observed above standard model expectations, and an upper limit is set with 95% confidence level on the production cross section times the branching fraction to leptons, as a function of the long-lived massive neutral particle lifetime. Copyright CERN.

Estudo de Monte Carlo da produção de nova ressonância neutra decaindo em dois bósons vetoriais no experimento CMS

Pós-graduação em Física - IFT

Busca por dimensões extras no detector CMS do large hadron collider

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Measurement of the differential and double-differential Drell-Yan cross sections in proton-proton collisions at root s=7 TeV

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Measurement of Higgs boson production and properties in the WW decay channel with leptonic final states

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)