Open and Hidden Charm Production in 920 GeV Proton-Nucleus Collisions

The HERA-B collaboration has studied the production of charmonium and open charm states in collisions of 920 GeV protons with wire targets of different materials. The acceptance of the HERA-B spectrometer covers negative values of xF up to xF=-0.3 and a broad range in transverse momentum from 0.0 to 4.8 GeV/c. The studies presented in this paper include J/psi differential distributions and the suppression of J/psi production in nuclear media. Furthermore, production cross sections and cross section ratios for open charm mesons are discussed.Comment: 5 pages, 9 figures, to be published in the proceedings of the 6th International Conference on Hyperons, Charm & Beauty Hadrons (BEACH04), Chicago, IL, June 27 - July 3, 200

Search for the Flavor-Changing Neutral Current Decay D0→μ+μ−D^0 \to \mu^+\mu^- with the HERA-B Detector

We report on a search for the flavor-changing neutral current decay $D^0 \to \mu^+\mu^-$ using $50 \times 10^6$ events recorded with a dimuon trigger in interactions of 920 GeV protons with nuclei by the HERA-B experiment. We find no evidence for such decays and set a 90% confidence level upper limit on the branching fraction $Br(D^0 \to \mu^+\mu^-) <2.0 \times 10^{-6}$.Comment: 17 pages, 4 figures (of which 1 double), paper to be submitted to Physics Letters

Measurement of the J/Psi Production Cross Section in 920 GeV/c Fixed-Target Proton-Nucleus Interactions

The mid-rapidity (dsigma_(pN)/dy at y=0) and total sigma_(pN) production cross sections of J/Psi mesons are measured in proton-nucleus interactions. Data collected by the HERA-B experiment in interactions of 920 GeV/c protons with carbon, titanium and tungsten targets are used for this analysis. The J/Psi mesons are reconstructed by their decay into lepton pairs. The total production cross section obtained is sigma_(pN)(J/Psi) = 663 +- 74 +- 46 nb/nucleon. In addition, our result is compared with previous measurements

Clinical Practice Guideline for the Diagnosis and Management of Adult Patients with Functional Chronic Constipation

Resumen Objetivo: diseñar una guía de práctica clínica para orientar el diagnóstico, y establecer la clasificación y el tratamiento farmacológico y no farmacológico en los pacientes adultos con estreñimiento crónico funcional en Colombia. Materiales y métodos: el grupo desarrollador de la presente guía estuvo conformado por un equipo multidisciplinario con apoyo de la Asociación Colombiana de Gastroenterología, el Grupo Cochrane ITS y el Instituto de Investigaciones Clínicas de la Universidad Nacional de Colombia. Se desarrollaron preguntas clínicas relevantes y se realizó la búsqueda de guías nacionales e internacionales en bases de datos especializadas. Las guías existentes fueron evaluadas en términos de calidad y aplicabilidad; ninguna de ellas cumplió criterios de adaptación, por lo que se decidió desarrollar una guía de novo. El Grupo Cochrane realizó la búsqueda sistemática de la literatura. Las tablas de evidencia y recomendaciones fueron realizadas usando la metodología GRADE. Resultados: se desarrolló una guía de práctica clínica basada en la evidencia para el diagnóstico, clasificación y tratamiento farmacológico y no farmacológico de los pacientes con estreñimiento crónico funcional en Colombia. Conclusiones: se establecieron los criterios clínicos y signos de alarma, las pruebas diagnósticas y los esquemas terapéuticos que se recomiendan en la atención de los pacientes con estreñimiento crónico funcional en Colombia.Guías de práctica clínica basadas en la evidencia57-66Abstract Objective: Design a clinical practice guideline to orient the diagnosis and establishing the classification and pharmacological and non-pharmacological treatment in adult patients with chronic functional constipation in Colombia. Materials and Methods: This guide was developed by a multidisciplinary team with the support of the Colombian Association of Gastroenterology, Cochrane STI Group and Clinical Research Institute of the Universidad Nacional de Colombia. Relevant clinical questions were developed and the search for national and international guidelines in databases was performed. Existing guidelines were evaluated for quality and applicability. None of the guidelines met the criteria for adaptation, so the group decided to develop a de novo guideline. Systematic literature searches were conducted by the Cochrane Group. The tables of evidence and recommendations were made based on the GRADE methodology. Results: A clinical practice based on evidence was developed for the diagnosis, classification and pharmacological and non-pharmacological treatment of patients with chronic functional constipation in Colombia. Conclusions: The clinical criteria and warning signs, diagnostic tests and therapeutic regimens that are recommended in the care of patients with chronic functional constipation were established in Colombi

Gaia Early Data Release 3: Summary of the contents and survey properties

Context. We present the early installment of the third Gaia data release, Gaia EDR3, consisting of astrometry and photometry for 1.8 billion sources brighter than magnitude 21, complemented with the list of radial velocities from Gaia DR2. Aims. A summary of the contents of Gaia EDR3 is presented, accompanied by a discussion on the differences with respect to Gaia DR2 and an overview of the main limitations which are present in the survey. Recommendations are made on the responsible use of Gaia EDR3 results. Methods. The raw data collected with the Gaia instruments during the first 34 months of the mission have been processed by the Gaia Data Processing and Analysis Consortium and turned into this early third data release, which represents a major advance with respect to Gaia DR2 in terms of astrometric and photometric precision, accuracy, and homogeneity. Results. Gaia EDR3 contains celestial positions and the apparent brightness in G for approximately 1.8 billion sources. For 1.5 billion of those sources, parallaxes, proper motions, and the (GBP − GRP) colour are also available. The passbands for G, GBP, and GRP are provided as part of the release. For ease of use, the 7 million radial velocities from Gaia DR2 are included in this release, after the removal of a small number of spurious values. New radial velocities will appear as part of Gaia DR3. Finally, Gaia EDR3 represents an updated materialisation of the celestial reference frame (CRF) in the optical, the Gaia-CRF3, which is based solely on extragalactic sources. The creation of the source list for Gaia EDR3 includes enhancements that make it more robust with respect to high proper motion stars, and the disturbing effects of spurious and partially resolved sources. The source list is largely the same as that for Gaia DR2, but it does feature new sources and there are some notable changes. The source list will not change for Gaia DR3. Conclusions. Gaia EDR3 represents a significant advance over Gaia DR2, with parallax precisions increased by 30 per cent, proper motion precisions increased by a factor of 2, and the systematic errors in the astrometry suppressed by 30-40% for the parallaxes and by a factor ~2.5 for the proper motions. The photometry also features increased precision, but above all much better homogeneity across colour, magnitude, and celestial position. A single passband for G, GBP, and GRP is valid over the entire magnitude and colour range, with no systematics above the 1% leve

A reforma educacional no México e no Chile: apontamentos sobre as rupturas e continuidades

Este artigo busca resgatar a inflexão ocorrida recentemente nas políticas educacionais da América Latina a partir de duas situações específicas, a do México e a do Chile. Considerando que tais políticas têm sido implementadas a partir de uma lógica relacionada à globalização capitalista em curso e são expressões da correlação de forças sociais num espaço concreto, propõe-se identificar de que forma diretrizes comuns, definidas por organismos internacionais, interagem com as características culturais vigentes em cada país. Tal preocupação advém da percepção acerca da função social da área educacional e de sua dinâmica como expressão das contradições. Conclui-se que, embora alvo de políticas semelhantes, a realidade educacional nos dois países expressa situações distintas: no México, tem-se uma "ruptura conservadora", pelo seu caráter regressivo, e no Chile uma "continuidade conservadora"

DIRAC Experiment and Test of Low-Energy QCD

The low-energy QCD predictions to be tested by the DIRAC experiment are revised. The experimental method, the setup characteristics and capabilities, along with first experimental results are reported. Preliminary analysis shows good detector performance: alignment error via $\Lambda$ mass measurement $m_\Lambda = 1115.6 MeV/c^2$ with $\sigma = 0.92 MeV/c^2$, $p \pi^-$ relative momentum resolution $\sigma_Q \approx 2.7 MeV/c$, and evidence for $\pi^

Search for lepton-number violating B+ -> X(-)l(+)l '(+) decays

We report on a search for eleven lepton-number violating processes B+ -> X(-)l(+)l'(+) with X- = K-, pi(-), rho(-), K*(-), or D- and l(+)/l'(+) = e(+) or mu(+), using a sample of 471 +/- 3 million B (B) over bar events collected with the BABAR detector at the PEP-II e(+)e(-) collider at the SLAC National Accelerator Laboratory. We find no evidence for any of these modes and place 90% confidence level upper limits on their branching fractions in the range (1.5-26) x 10(-7)

DIRAC: A High Resolution Spectrometer for Pionium Detection

The DIRAC spectrometer has been commissioned at CERN with the aim of detecting $\pi^+ \pi^-$ atoms produced by a 24 GeV/$c$ high intensity proton beam in thin foil targets. A challenging apparatus is required to cope with the high interaction rates involved, the triggering of pion pairs with very low relative momentum, and the measurement of the latter with resolution around 0.6 MeV/$c$. The general characteristics of the apparatus are explained and each part is described in some detail. The main features of the trigger system, data-acquisition, monitoring and setup performances are also given.Comment: 49 pages, 37 figures. Figures 1, 2, 5 and 28 are removed because of size limitations imposed by hep-ex. They don't offer essential information. Latex class file 'elsart.cls' also provide

First measurement of the π+π−\pi^+\pi^- atom lifetime

The goal of the DIRAC experiment at CERN (PS212) is to measure the $\pi^+\pi^-$ atom lifetime with 10% precision. Such a measurement would yield a precision of 5% on the value of the $S$-wave $\pi\pi$ scattering lengths combination $|a_0-a_2|$. Based on part of the collected data we present a first result on the lifetime, $\tau=[2.91 ^{+0.49}_{-0.62}]\times 10^{-15}$ s, and discuss the major systematic errors. This lifetime corresponds to $|a_0-a_2|=0.264 ^{+0.033}_{-0.020} m_{\pi}^{-1}$.Comment: 18 pages, 6 figure