1,721,219 research outputs found
Measurement of Bs oscillations at CDF
No full textThe first precise measurement of the B0
s − ̄B 0
s oscillation frequency Δms with the CDFII experiment is summarized
in this talk. The measurement is performed with 1 fb−1 of data collected at the Fermilab Tevatron hadron
collider. We find a signal consistent with flavour oscillations; the probability that such a signal is originated by
random fluctuations is 0.2%. We measure Δms = 17.31+0.33
−0.18(stat.)±0.07(syst.) ps−1 [1]. After a brief theoretical
overview, I will describe the experimental technique and show the results of the CDF analysis and the |Vtd/Vts|
value we infer from this measurement
Measurement of the top quark mass with the ATLAS detector
No full textAn overview is presented of the measurements of the top quark mass performed by the ATLAS experiment at the LHC with an integrated luminosity varying between 35 pb and 4.7 fb. Different techniques are used to measure the top quark mass looking at events in all three signatures: fully-hadronic, lepton+jets and di-leptonic ones. The most precise measurement, using a template method on lepton+jets events, yields a top quark mass of 174.5 0.6 (stat) 2.3 (syst) GeV. The dominant systematic uncertainties are related to the determination of the jet energy scale and the modelling of additional radiation accompanying the pair production
ATLAS Electroweak results
No full text{We present the first results on electroweak physics obtained by the ATLAS experiment at the CERN Large Hadron Collider (LHC), using collisions at a centre-of-mass energy of 7 TeV. The observation of the and electroweak bosons in leptonic decays and the first measurements of their production cross-section at represent one of the most important benchmarks of the first stage of data-taking at the LHC and provide a first confirmation of the Standard Model (SM) predictions. Furthermore they are an important candle to understand and calibrate the ATLAS detector with early data. We describe the experimental techniques, issues and the measurement results, together with a comparison with SM expectations, using up to 225 of integrated luminosity. A first look at the and production as a function of the number of accompanying jets is also provided. Finally, a first search for production and a comparison of the identified candidates with the expected kinematic distributions from simulation is described
Techniques for Bs mixing at CDF
No full textThe techniques used to perform a measurement of the mixing frequency of the B{sub s} meson ({Delta}M{sub s}) with the CDF detector at the TeVatron collider are described. Particular stress is put on CDF techniques for flavor tagging, which is possibly the major issue for mixing measurements at a hadron collider. Also CDF performances on lifetime and final state reconstruction are described. The final result of the amplitude scanning presented at 2005 Winter Conferences is reported
Present and Future of 0ν2β Searches with Germanium
No full textAmong the several experiments and techniques conceived of to search for neutrinoless double β decay (0ν2β) in a handful of isotopes, presently the best lower limit on the half-life for this rare process, is provided by those using 76Ge, a rare isotope of germanium. Such a lower limit is of 1.8 × 1026 y. Building from such a successful achievement of the GERDA and Majorana Demonstrator experiments, the baton with 76Ge passes now to the LEGEND experiment. Using a two-stage approach with about 200 kg and then 1 t of germanium, LEGEND aims to attain a sensitivity of around 1028 y, which will enable it to probe the standard inverted-ordering neutrino mass scenario. We touch upon the past generation of experiments to illustrate their strong and weak points, review the general concept and design of LEGEND, and describe the LEGEND-200 detector and its preliminary performance. We also illustrate how the backgrounds can have a dramatic effect on the search and in which way the latter can be mitigated
Measurement of the production cross section of prompt j/psi mesons in association with a W (+/-) boson in pp collisions root s=7 TeV with the ATLAS detector
No full textThe process pp -> W (+/-) J/psi provides a powerful probe of the production mechanism of charmonium in hadronic collisions, and is also sensitive to multiple parton interactions in the colliding protons. Using the 2011 ATLAS dataset of 4.5 fb(-1) of root s= 7 TeV pp collisions at the LHC, the first observation is made of the production of W (+/-) + prompt J/psi events in hadronic collisions, using W (+/-) -> mu nu(mu) and J/psi -> mu(+)mu(-) center dot A yield of W (+/-) + prompt J/psi events is observed, with a statistical significance of 5.1 sigma. The production rate as a ratio to the inclusive W (+/-) boson production rate is measured, and the double parton scattering contribution to the cross section is estimated
Measurement of the production of a W boson in association with a charm quark in pp collisions at root s=7 TeV with the ATLAS detector
No full textThe production of a W boson in association with a single charm quark is studied using 4.6 fb(-1) of pp collision data at root s = 7 TeV collected with the ATLAS detector at the Large Hadron Collider. In events in which a W boson decays to an electron or muon, the charm quark is tagged either by its semileptonic decay to a muon or by the presence of a charmed meson. The integrated and differential cross sections as a function of the pseudorapidity of the lepton from the W-boson decay are measured. Results are compared to the predictions of next-to-leading-order QCD calculations obtained from various parton distribution function parameterisations. The ratio of the strange-to-down sea-quark distributions is determined to be 0.96(-0.30)(+0.26) at Q (2) = 1.9 GeV2, which supports the hypothesis of an SU(3)-symmetric composition of the light-quark sea. Additionally, the cross-section ratio sigma(W (+) +)/sigma(W (-) + c) is compared to the predictions obtained using parton distribution function parameterisations with different assumptions about the s-(s) over bar quark asymmetry
Searches for heavy long-lived sleptons and R-hadrons with the ATLAS detector in pp collisions at √s = 7 TeV
No full text"\"A search for long-lived particles is performed using a data sample of 4.7 fb(-1) from proton-proton collisions at a centre-of-mass energy. root s = 7 TeV collected by the ATLAS detector at the LHC. No excess is observed above the estimated background and lower limits, at 95% confidence level, are set on the mass of the long-lived particles in different scenarios, based on their possible interactions in the inner detector, the calorimeters and the muon spectrometer. Long-lived staus in gauge-mediated SUSY-breaking models are excluded up to a mass of 300 GeV for tan beta = 5-20. Directly produced long-lived sleptons are excluded up to a mass of 278 GeV. R-hadrons, composites of gluino (stop, sbottom) and light quarks, are excluded up to a mass of 985 GeV (683 GeV, 612 GeV) when using a generic interaction model. Additionally two sets of limits on R-hadrons are obtained that are less sensitive to the interaction model for R-hadrons. One set of limits is obtained using only the inner detector and calorimeter observables, and a second set of limits is obtained based on the inner detector alone. (c) 2013 CERN. Published by Elsevier B.V. All rights reserved.\"
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