A Powerful Optimization Tool for Analog Integrated Circuits Design

This paper presents a new optimization tool for analog circuit design. Proposed tool is based on the robust version of the differential evolution optimization method. Corners of technology, temperature, voltage and current supplies are taken into account during the optimization. That ensures robust resulting circuits. Those circuits usually do not need any schematic change and are ready for the layout.. The newly developed tool is implemented directly to the Cadence design environment to achieve very short setup time of the optimization task. The design automation procedure was enhanced by optimization watchdog feature. It was created to control optimization progress and moreover to reduce the search space to produce better design in shorter time. The optimization algorithm presented in this paper was successfully tested on several design examples

How accurately can we measure the W cross section?

We study the QCD sources of systematic uncertainties in the experimental extraction of the W cross section at hadron colliders. The uncertainties appear in the evaluation of the detector acceptances used to convert the number of observed events into a total production cross section. We consider the effect of NLO corrections, as well as of the inclusion of parton showers, and evaluate the impact of spin correlations and of PDF and scale uncertainties.Comment: 16 pages, 6 figure

Calculating Dilepton Rates from Monte Carlo Simulations of Parton Production

To calculate dilepton rates in a Monte Carlo simulation of ultrarelativistic heavy ion collisions, one usually scales the number of similar QCD processes by a ratio of the corresponding differential probabilities. We derive the formula for such a ratio especially for dilepton bremsstrahlung processes. We also discuss the non-triviality of including higher order corrections to direct Drell-Yan process. The resultant mass spectra from our Monte Carlo simulation are consistent with the semi-analytical calculation using dilepton fragmentation functions.Comment: 14 pages in RevTex, 3 figures in uuencoded files, LBL-3466

The extraction of nuclear sea quark distribution and energy loss effect in Drell-Yan experiment

The next-to-leading order and leading order analysis are performed on the differential cross section ratio from Drell-Yan process. It is found that the effect of next-to-leading order corrections can be negligible on the differential cross section ratios as a function of the quark momentum fraction in the beam proton and the target nuclei for the current Fermilab and future lower beam proton energy. The nuclear Drell-Yan reaction is an ideal tool to study the energy loss of the fast quark moving through cold nuclei. In the leading order analysis, the theoretical results with quark energy loss are in good agreement with the Fermilab E866 experimental data on the Drell-Yan differential cross section ratios as a function of the momentum fraction of the target parton. It is shown that the quark energy loss effect has significant impact on the Drell-Yan differential cross section ratios. The nuclear Drell-Yan experiment at current Fermilab and future lower energy proton beam can not provide us with more information on the nuclear sea quark distribution.Comment: 17 pages, 4 figure

Correction Factors for Reactions involving Quark-Antiquark Annihilation or Production

In reactions with $q \bar q$ production or $q\bar q$ annihilation, initial- and final-state interactions give rise to large corrections to the lowest-order cross sections. We evaluate the correction factor first for low relative kinetic energies by studying the distortion of the relative wave function. We then follow the procedure of Schwinger to interpolate this result with the well-known perturbative QCD vertex correction factors at high energies, to obtain an explicit semi-empirical correction factor applicable to the whole range of energies. The correction factor predicts an enhancement for $q\bar q$ in color-singlet states and a suppression for color-octet states, the effect increasing as the relative velocity decreases. Consequences on dilepton production in the quark-gluon plasma, the Drell-Yan process, and heavy quark production processes are discussed.Comment: 25 pages (REVTeX), includes 2 uuencoded compressed postscript figure

QCD and Yukawa corrections to single-top-quark production via q qbar -> t bbar

We calculate the O(alpha_s) and O(alpha_W m_t^2/M_W^2) corrections to the production of a single top quark via the weak process q qbar -> t bbar at the Fermilab Tevatron and the CERN Large Hadron Collider. An accurate calculation of the cross section is necessary in order to extract |V_tb| from experiment.Comment: LaTeX, 13 pages, replaced with version to appear in Phys. Rev.

QCD threshold corrections to di-lepton and Higgs rapidity distributions beyond N2{}^2LO

We present threshold enhanced QCD corrections to rapidity distributions of di-leptons in the Drell-Yan process and of Higgs particles in both gluon fusion and bottom quark annihilation processes using Sudakov resummed cross sections. We have used renormalisation group invariance and the mass factorisation theorem that these hard scattering cross sections satisfy as well as Sudakov resummation of QCD amplitudes. We find that these higher order threshold QCD corrections stabilise the theoretical predictions under scale variations.Comment: 1+34 pages, four plot

Predictions for Higgs production at the Tevatron and the associated uncertainties

We update the theoretical predictions for the production cross sections of the Standard Model Higgs boson at the Fermilab Tevatron collider, focusing on the two main search channels, the gluon-gluon fusion mechanism $gg \to H$ and the Higgs-strahlung processes $q \bar q \to VH$ with $V=W/Z$, including all relevant higher order QCD and electroweak corrections in perturbation theory. We then estimate the various uncertainties affecting these predictions: the scale uncertainties which are viewed as a measure of the unknown higher order effects, the uncertainties from the parton distribution functions and the related errors on the strong coupling constant, as well as the uncertainties due to the use of an effective theory approach in the determination of the radiative corrections in the $gg \to H$ process at next-to-next-to-leading order. We find that while the cross sections are well under control in the Higgs--strahlung processes, the theoretical uncertainties are rather large in the case of the gluon-gluon fusion channel, possibly shifting the central values of the next-to-next-to-leading order cross sections by more than $\approx 40$. These uncertainties are thus significantly larger than the $\approx 10$ error assumed by the CDF and D0 experiments in their recent analysis that has excluded the Higgs mass range $M_H=$162-166 GeV at the 95% confidence level. These exclusion limits should be, therefore, reconsidered in the light of these large theoretical uncertainties.Comment: 40 pages, 12 figures. A few typos are corrected and some updated numbers are provide

Módulo experimental para el diseño de sistemas solares pasivos

El presente trabajo consiste en desarrollar y ejecutar un proyecto que tenga la incorporación de criterios constructivos Bioambientales cuyo objetivo general es evaluar el ahorro energético en función de la envolvente y la aplicación de una metodología de cálculo para un diseño solar pasivo, para lo cual se desarrolló una programación de mediciones sistemáticas de las temperaturas superficiales, temperaturas del aire, flujos de calor y energías consumidas para mantener el grado de confort en el interior del módulo. En el análisis de este trabajo se buscó relacionando el valor “G" del balance térmico de la envolvente con la energía consumida y las temperaturas exteriores colocando los valores obtenidos en una función lineal que nos permita cuantificar el ahorro energético. Y de esta forma se puede confeccionar o estipular la relación costo - beneficio.Facultad de Arquitectura y Urbanism