Showing papers by "Universidad Iberoamericana Ciudad de México published in 2007"

CMS physics technical design report, volume II: Physics performance

Abstract: CMS is a general purpose experiment, designed to study the physics of pp collisions at 14 TeV at the Large Hadron Collider (LHC). It currently involves more than 2000 physicists from more than 150 institutes and 37 countries. The LHC will provide extraordinary opportunities for particle physics based on its unprecedented collision energy and luminosity when it begins operation in 2007. The principal aim of this report is to present the strategy of CMS to explore the rich physics programme offered by the LHC. This volume demonstrates the physics capability of the CMS experiment. The prime goals of CMS are to explore physics at the TeV scale and to study the mechanism of electroweak symmetry breaking--through the discovery of the Higgs particle or otherwise. To carry out this task, CMS must be prepared to search for new particles, such as the Higgs boson or supersymmetric partners of the Standard Model particles, from the start-up of the LHC since new physics at the TeV scale may manifest itself with modest data samples of the order of a few fb−1 or less. The analysis tools that have been developed are applied to study in great detail and with all the methodology of performing an analysis on CMS data specific benchmark processes upon which to gauge the performance of CMS. These processes cover several Higgs boson decay channels, the production and decay of new particles such as Z' and supersymmetric particles, Bs production and processes in heavy ion collisions. The simulation of these benchmark processes includes subtle effects such as possible detector miscalibration and misalignment. Besides these benchmark processes, the physics reach of CMS is studied for a large number of signatures arising in the Standard Model and also in theories beyond the Standard Model for integrated luminosities ranging from 1 fb−1 to 30 fb−1. The Standard Model processes include QCD, B-physics, diffraction, detailed studies of the top quark properties, and electroweak physics topics such as the W and Z0 boson properties. The production and decay of the Higgs particle is studied for many observable decays, and the precision with which the Higgs boson properties can be derived is determined. About ten different supersymmetry benchmark points are analysed using full simulation. The CMS discovery reach is evaluated in the SUSY parameter space covering a large variety of decay signatures. Furthermore, the discovery reach for a plethora of alternative models for new physics is explored, notably extra dimensions, new vector boson high mass states, little Higgs models, technicolour and others. Methods to discriminate between models have been investigated. This report is organized as follows. Chapter 1, the Introduction, describes the context of this document. Chapters 2-6 describe examples of full analyses, with photons, electrons, muons, jets, missing ET, B-mesons and τ's, and for quarkonia in heavy ion collisions. Chapters 7-15 describe the physics reach for Standard Model processes, Higgs discovery and searches for new physics beyond the Standard Model

CMS physics technical design report: Addendum on high density QCD with heavy ions

Abstract: This report presents the capabilities of the CMS experiment to explore the rich heavy-ion physics programme offered by the CERN Large Hadron Collider (LHC). The collisions of lead nuclei at energies , will probe quark and gluon matter at unprecedented values of energy density. The prime goal of this research is to study the fundamental theory of the strong interaction ? Quantum Chromodynamics (QCD) ? in extreme conditions of temperature, density and parton momentum fraction (low-x).This report covers in detail the potential of CMS to carry out a series of representative Pb-Pb measurements. These include bulk observables, (charged hadron multiplicity, low pT inclusive hadron identified spectra and elliptic flow) which provide information on the collective properties of the system, as well as perturbative probes such as quarkonia, heavy-quarks, jets and high pT hadrons which yield tomographic information of the hottest and densest phases of the reaction.

Analysis of the quantum numbers J(PC) of the X(3872) particle.

Abstract: The authors present an analysis of angular distributions and correlations of the X(3872) in the exclusive decay mode X(3872) {yields} J/{psi}{pi}{sup +}{pi}{sup -} with J/{psi} {yields} {mu}{sup +}{mu}{sup -}. They use 780 pb{sup -1} of data from p{bar p} collisions at {radical}s = 1.96 TeV collected with the CDF II detector at the Fermilab Tevatron. They derive constraints on spin, parity, and charge conjugation parity of the X(3872) by comparing measured angular distributions of the decay products with predictions for different J{sup PC} hypotheses. The assignments J{sup PC} = 1{sup ++} and 2{sup -+} are the only ones consistent with the data.

Measurement of the inclusive jet cross section using the kT algorithm in pp̄ collisions at s=1.96TeV with the CDF II detector

Abstract: The authors report on measurements of the inclusive jet production cross section as a function of the jet transverse momentum in p{bar p} collisions at {radical}s = 1.96 TeV, using the k{sub T} algorithm and a data sample corresponding to 1.0 fb{sup -1} collected with the Collider Detector at Fermilab in Run II. The measurements are carried out in five different jet rapidity regions with |y{sup jet}| < 2.1 and transverse momentum in the range 54 < p{sub T}{sup jet} < 700 GeV/c. Next-to-leading order perturbative QCD predictions are in good agreement with the measured cross sections.

Observation and mass measurement of the baryon Ξb

Abstract: We report the observation and measurement of the mass of the bottom, strange baryon {xi}{sub b}{sup -} through the decay chain {xi}{sub b}{sup -}{yields}J/{psi}{xi}{sup -}, where J/{psi}{yields}{mu}{sup +}{mu}{sup -}, {xi}{sup -}{yields}{lambda}{pi}{sup -}, and {lambda}{yields}p{pi}{sup -}. A signal is observed whose probability of arising from a background fluctuation is 6.6x10{sup -15}, or 7.7 Gaussian standard deviations. The {xi}{sub b}{sup -} mass is measured to be 5792.9{+-}2.5(stat) {+-}1.7(syst) MeV/c{sup 2}.

Simultaneous cyclic scheduling and optimal control of polymerization reactors

Abstract: The simultaneous solution of the optimal sequencing and optimal dynamic transitions of two multigrade polymerization continuous stirred-tank reactors (CSTRs) is presented. The simultaneous formulation leads to a mixed-integer dynamic optimization (MIDO) problem. The profiles of the state variables during dynamic transitions are discretized using orthogonal collocation on finite elements, transforming the MIDO problem into a mixed-integer nonlinear programming (MINLP) problem. The objective of this formulation is to maximize the profit of the manufacturing operation, considering polymer sales, inventory costs and transition costs. The transition cost term is determined by the duration of the transition stages and the manipulated variable profile during transitions. Two industrial reaction systems are used to analyze the optimal solution and compare it to other solutions obtained using different methods. Finally, a sensitivity analysis is carried out to describe the impact of changes in certain problem parameters. © 2007 American Institute of Chemical Engineers AIChE J, 2007

Measurement of the B+ production cross section in pp̄ collisions at s=1960GeV

Abstract: The authors present a new measurement of the B{sup +} meson differential cross section d{sigma}/dP{sub T} at {radical}s = 1960 GeV. The data correspond to an integrated luminosity of 739 pb{sup -1} collected with the upgraded CDF detector (CDF II) at the Fermilab Tevatron collider. B{sup +} candidates are reconstructed through the decay B{sup +} {yields} J/{psi} K{sup +}, with J/{psi} {yields} {mu}{sup +}{mu}{sup -}. The integrated cross section for producing B{sup +} mesons with p{sub T} {ge} 6 GeV/c and |y| {le} 1 is measured to be 2.78 {+-} 0.24 {mu}b.

First Measurement of the W-Boson Mass in Run II of the Tevatron

Abstract: We present a measurement of the W boson mass using 200 pb{sup -1} of data collected in p{bar p} collisions at {radical}s = 1.96 TeV by the CDF II detector at Run II of the Fermilab Tevatron. With a sample of 63964 W {yields} ev candidates and 51128 W W {yields} {mu}v candidates, we measure M{sub W} = (80413 {+-} 34{sub stat} {+-}34{sub syst} = 80413 {+-} 48) MeV/c{sup 2}. This is the most precise single measurement of the W boson mass to date.

Environmental and personal correlates of fruit and vegetable consumption in low income, urban Mexican children.

Abstract: Background Epidemiological evidence suggests that populations with high fruit and vegetable (FV) consumption have a lower risk for childhood obesity, cancer and cardiovascular diseases. There are no studies that address the correlates of FV intake in Mexican children; therefore, the aim of this study was to identify the frequency of FV consumption by children in Mexico City’s low income state schools and their personal (preferences, expectancy, knowledge and self-efficacy) and environmental (accessibility and person in charge of cooking at home) correlates. Methods A validated questionnaire to assess accessibility, expectancy, self-efficacy, preference and knowledge; and a 2-day dietary recall were used to assess the FV intake and its correlates in 327 children. Statistical analysis included chi-square and stepwise logistic regression. Results Average consumption of FV was once a day with a higher proportion of girls consuming FV 3 or more times per day (15.2% versus 6.7%; P < 0.01). The environmental factors that influenced a higher consumption of FV were the mother being responsible for cooking at home (P < 0.02) and accessibility to FV (P < 0.01); whereas the personal factors were self-efficacy (P < 0.05) and preference (P < 0.03) to vegetables. Conclusion Correlates of fruit and vegetable consumption in children from Mexico City’s State Schools were being female and accessibility to fruits and vegetables. Home and school environments are decisive for the children to increase FV consumption. Creative ways to encourage FV consumption in boys should be explored. These factors should be considered when designing programmes aimed at increasing consumption of fruits and vegetables in children.

Measurement of the top-quark mass in all-hadronic decays in pp collisions at CDF II.

Abstract: We present a measurement of the top-quark mass M-top in the all-hadronic decay channel t (t) over bar -> W(+)bW(-)(b) over bar -> q(1)(q) over bar (2)bq(3)(q) over bar (4)(b) over bar. The analysis is performed using 310 pb(-1) of root s=1.96 TeV p (p) over bar collisions collected with the CDF II detector using a multijet trigger. The mass measurement is based on an event-by-event likelihood which depends on both the sample purity and the value of the top-quark mass, using 90 possible jet-to-parton assignments in the six-jet final state. The joint likelihood of 290 selected events yields a value of M-top=177.1 +/- 4.9(stat)+/- 4.7(syst) GeV/c(2).

Precision measurement of the top-quark mass from dilepton events at CDF II

Abstract: We report a measurement of the top quark mass, M{sub t}, in the dilepton decay channel of t{bar t} {yields} b{ell}{prime}{sup +} {nu}{sub {ell}}, {bar b}{ell}{sup -}{bar {nu}}{sub {ell}} using an integrated luminosity of 1.0 fb{sup -1} of p{bar p} collisions collected with the CDF II detector. We apply a method that convolutes a leading-order matrix element with detector resolution functions to form event-by-event likelihoods; we have enhanced the leading-order description to describe the effects of initial-state radiation. The joint likelihood is the product of the likelihoods from 78 candidate events in this sample, which yields a measurement of M{sub t} = 164.5 {+-} 3.9(stat.) {+-} 3.9(syst.) GeV/c{sup 2}, the most precise measurement of M{sub t} in the dilepton channel.

Searches for direct pair production of supersymmetric top and supersymmetric bottom quarks in pp̄ collisions at s=1.96TeV

Abstract: We search for direct pair production of supersymmetric top quarks and supersymmetric bottom quarks in proton-antiproton collisions at {radical}(s)=1.96 TeV, using 295 pb{sup -1} of data recorded by the Collider Detector at Fermilab (CDF II) experiment. The supersymmetric top (supersymmetric bottom) quarks are selected by reconstructing their decay into a charm (bottom) quark and a neutralino, which is assumed to be the lightest supersymmetric particle. The signature of such processes is two energetic heavy-flavor jets and missing transverse energy. The number of events that pass our selection for each search process is consistent with the expected standard model background. By comparing our results to the theoretical production cross sections of the supersymmetric top and supersymmetric bottom quarks in the minimal supersymmetric standard model, we exclude, at a 95% confidence level in the frame of that model, a supersymmetric top quark mass up to 132 GeV/c{sup 2} for a neutralino mass of 48 GeV/c{sup 2}, and a supersymmetric bottom quark mass up to 193 GeV/c{sup 2} for a neutralino mass of 40 GeV/c{sup 2}.

Search for new particles leading to Z+jets final states in pp̄ collisions at s=1.96TeV

Abstract: We present the results of a search for new particles that lead to a Z boson plus jets in p{bar p} collisions at {radical}s = 1.96 TeV using the Collider Detector at Fermilab (CDF II). A data sample with a luminosity of 1.06 fb{sup -1} collected using Z boson decays to ee and {mu}{mu} is used. We describe a completely data-based method to predict the dominant background from standard-model Z+jet events. This method can be similarly applied to other analyses requiring background predictions in multi-jet environments, as shown when validating the method by predicting the background from W+jets in t{bar t} production. No significant excess above the background prediction is observed, and a limit is set using a fourth generation quark model to quantify the acceptance. Assuming BR(b{prime} {yields} bZ) = 100% and using a leading-order calculation of the b{prime} cross section, b{prime} quark masses below 268 GeV/c2 are excluded at 95% confidence level.

Pobreza y apoyo social: un estudio comparativo en tres niveles socioeconómicos

Abstract: Several studies have reported that social support promotes the mental and physical well-being. The people that feel supported by their friends and family, present less anxiety and depression, have a stronger immune system and a greater self-esteem. The current research had the objective the social support perception of three socioeconomic groups (N=918) and its relations with some psychological variables as self-esteem, coping, locus of control, depression, achievement motivation and subjective well-being. The findings show that for the three groups the main source of support is the nuclear family, followed by the church and the religion. However, some differences in the perception of the social support between the groups do exist, and also certain characteristics of personality were found to be associated with a greater social support perceived.

Observation of WZ Production

Abstract: We report the first observation of the associated production of a W boson and a Z boson. This result is based on 1.1 fb;-1 of integrated luminosity from pp collisions at sqrt[s]=1.96 TeV collected with the CDF II detector at the Fermilab Tevatron. We observe 16 WZ candidates passing our event selection with an expected background of 2.7+/-0.4 events. A fit to the missing transverse energy distribution indicates an excess of events compared to the background expectation corresponding to a significance equivalent to 6 standard deviations. The measured cross section is sigma(pp-->WZ)=5.0(-1.6)(+1.8) pb, consistent with the standard model expectation.

Measurement of the pp̄→tt̄ production cross section and the top quark mass at s=1.96TeV in the all-hadronic decay mode

Abstract: We report the measurements of the t{bar t} production cross section and of the top quark mass using 1.02 fb{sup -1} of p{bar p} data collected with the CDF II detector at the Fermilab Tevatron. We select events with six or more jets on which a number of kinematical requirements are imposed by means of a neural network algorithm. At least one of these jets must be identified as initiated by a b-quark candidate by the reconstruction of a secondary vertex. The cross section is measured to be {sigma}{sub t{bar t}} = 8.3 {+-} 1.0(stat. ){sup +2.0}{sub -1.5}(syst.) {+-} 0.5(lumi.) pb, which is consistent with the standard model prediction. The top quark mass of 174.0 {+-} 2.2(stat.){+-}4.8(syst.) GeV/c{sup 2} is derived from a likelihood fit incorporating reconstructed mass distributions representative of signal and background.

Education, employment and human development: illustrations from Mexico

Abstract: By applying Amartya Sen's capability approach, this article questions the functionalist idea that suggests that education can precipitate economic growth and development. It will be argued that the...

Search for heavy long-lived particles that decay to photons at CDF II.

Abstract: We present the first search for heavy, long-lived particles that decay to photons at a hadron collider. We use a sample of gamma + jet + missing transverse energy events in pp[over] collisions at square root[s] = 1.96 TeV taken with the CDF II detector. Candidate events are selected based on the arrival time of the photon at the detector. Using an integrated luminosity of 570 pb(-1) of collision data, we observe 2 events, consistent with the background estimate of 1.3+/-0.7 events. While our search strategy does not rely on model-specific dynamics, we set cross section limits in a supersymmetric model with [Formula: see text] and place the world-best 95% C.L. lower limit on the [Formula: see text] mass of 101 GeV/c(2) at [Formula: see text].

Winners and Losers of Regional Growth in Mexico and their Dynamics

Abstract: The case of Mexico offers an interesting example in the analysis of the evolution of regional disparities in developing countries thet have changed their policies from those of a state-led economy to those of economic liberalization and trade openness in the 1980s. The purpose of this paper is to focus on aspects derived from convergence and divergence, determining the dynamics and their determinants among regions in Mexico. Is doing so, we shall determine the standard Beta and Omega convergence.

Synthesis and structural characterization of novel flower-like titanium dioxide nanostructures

Abstract: Titanium dioxide (TiO 2 -anatase phase) films, consisting of agglomerated flower-like nanoparticles, have been synthesized using an ultrasonic spray pyrolysis method in conjunction with titanium (IV) oxide acetylacetonate (TiO(acac) 2 ) and methanol at 550 °C. These films were subsequently thermally treated in air, at 950 °C for 6 h, and the flower-like particles were transformed into smooth surfaces mainly formed by the TiO 2 rutile phase. In this letter, we characterized these structures using scanning electron microscopy, atomic force micrcoscopy, and low-angle X-ray diffraction measurements. It is proposed that these novel flower-like nanostructures, exhibiting a large number of exposed edges, will be important in the development of efficient gas sensor devices.

Movilidad residencial en la Ciudad de México

Abstract: This paper analyzes the ex-post of one aspect of the process of intra-urban migration, in other words, the effect of the decision to move or seek alternative housing by a high number of family units involved in the process. An aggregate analysis of this nature implies examining the changes experienced by the metropolitan structure of Mexico City at the end of the period when the phenomenon of intra-metropolitan mobility was registered (1995-2000). The point, then, is not to show the pattern of spatial differentiation at a specific time, but rather to reveal the changing trends experienced by urban structure over time, unlike a synchronic section that uses stock variables to show the spatial distribution pattern of these variables. The authors have sub-divided the Metropolitan Zone of Mexico City into concentric rings and urban zones or sectors. This recourse has long been used in urban social geography to simplify the distribution patterns of individuals and households with numerous economic and social characteristics that interact in a complex fashion within urban space. The use of these spatial models shows the relationships that occur between housing characteristics, residents’ attributes and their location in urban space.

Inflation and the public deficit when the utility of money is insatiable

Abstract: When the marginal utility of money is positive even at very high levels of the asset (Yoshiyasu Ono’s, 1994, assumption), the relationship between inflation and the public deficit at full employment may result in a unique perverse equilibrium where higher deficits reduce inflation. If there are two equilibria, the low inflation equilibrium is one where the perverse effect between inflation and the public deficit prevails; while in the high inflation equilibrium higher public deficits increase inflation. These results contrast sharply with traditional results found in the literature.

The Informal Sector in Mexico: characteristics and Dynamics

Abstract: This work analyzes the dynamics of the informal labor market in Mexico using information from the National Survey of Urban Employment (ENEU) and the urban section of the Quarterly National Employment Survey (ENET). In the first part, it compares three periods: 1990-1991, 1995-1996 and 200�-2004 to study the changes in eight of the labor market categories using transition matrices. The categories include dependent informal, dependent formal, employer, self-employed, public sector, not remunerated, unemployed and, inactive. In the second part, it uses a multinomial logit model with the mentioned categories as the dependent variable and it finds that age increases the probability of be ing in the informal sector and that education increases the probability of being employed in the formal or public sectors. The third part uses quantile regressions to explore the determination of salaries as function of the labor market categories. It is found that the categories employer and public sector have the highest returns.

Body movement induced by electrical stimulation of toe muscles during standing.

Abstract: The purpose of this study was to investigate whether artificially induced muscle contractions of toe muscles using functional electrical stimulation (FES) would cause center of pressure (COP) displacement and corresponding body acceleration. Ten able-bodied subjects were asked to stand still on force plates. The flexor digitorum brevis and the flexor hallucis brevis in both legs were simultaneously stimulated using a transcutaneous FES device. The muscles were stimulated 20 times at random intervals with four different stimulation intensities. We demonstrated that the toe muscle activity induced by electrical stimulation evoked COP displacement, which generated body acceleration. As expected, a larger stimulation induced a larger COP movement and acceleration. Therefore, we propose the use of FES-induced contractions of the toe muscles as a means to control balance during FES-assisted quiet standing. Spinal cord-injured and severe-stroke patients could benefit from this electrical stimulation technique for improving FES-assisted standing.

Measurement of σ(pp̄→Z)·B(Z→ττ) in pp̄ collisions at s=1.96TeV

Abstract: We present a measurement of the inclusive production cross section for Z bosons decaying to tau leptons in pp collisions at {radical}(s)=1.96 TeV. We use a channel with one hadronically-decaying and one electronically-decaying tau. This measurement is based on 350 pb{sup -1} of CDF Run II data. Using a sample of 504 opposite sign e{tau} events with a total expected background of 190 events, we obtain {sigma}(pp{yields}4Z){center_dot}B(Z{yields}{tau}{tau})=264{+-}23(stat){+-}14(syst){+-}15(lumi) pb, in agreement with the next-to-next-to-leading order QCD prediction. This is the first CDF cross section measurement using hadronically-decaying taus in Run II.

Optimal Start-Up and Product Transition Policies of a Reactive Distillation Column

Abstract: In the processing industry, there is the need to approach the operation of industrial equipment so they increase their energy efficiency, leading to more-economical and environmentally oriented processes. A feasible way to achieve these purposes lies in the optimal dynamic operation of industrial operations. In this work, we address the dynamic optimal operation of a highly energy-intensive industrial operation (distillation) under two common operating scenarios: start-up and steady-state transition operations. The start-up operations and steady-state transitions of a reactive distillation column were addressed in this paper by approaching the problem as a dynamic optimization problem. A detailed tray-by-tray model that considers internal tray hydraulics, but ignores vapor dynamics, was derived and used for calculations. Several manipulated variables were considered, besides the reboiler heat duty. The large scale nonlinear programming (NLP) problems generated from the application of the simultaneous dyn...