5,144 research outputs found
In-situ Determination of the ATLAS Muon Performance
The ATLAS detector allows for the precise and efficient reconstruction of muons. Muon
tracks are reconstructed with 97% efficiency with a momentum resolution of approximately 2-3%
over most of the kinematic range and better than 10% for transverse momenta up to 1 TeV and
|η| <2.7. We present methods to measure the performance of the muon identification during the
operation of the ATLAS detector using muons from Z and J/ψdecays
Choice and the composition of general practice patient registers
Choice of general practice (GP) in the National Health Service (NHS), the UKs universal healthcare
service, is a core element in the current trajectory of NHS policy. This paper uses an accessibility-based
approach to investigate the pattern of patient choice that exists for GPs in the London
Borough of Southwark. Using a spatial model of GP accessibility it is shown that particular population
groups make non-accessibility based decisions when choosing a GP. These patterns are assessed by
considering differences in the composition of GP patient registers between the current patient
register, and a modelled patient register configured for optimal access to GPs. The patient
population is classified in two ways for the purpose of this analysis: by geodemographic group, and
by ethnicity. The paper considers choice in healthcare for intra-urban areas, focusing on the role of
accessibility and equity
Tachyons, Supertubes and Brane/Anti-Brane Systems
We find supertubes with arbitrary (and not necessarily planar) cross section;
the stability against the D2-brane tension is due to a compensation by the
local momentum generated by Born-Infeld fields. Stability against long-range
supergravity forces is also established. We find the corresponding solutions of
the infinite-N M(atrix) model. The supersymmetric D2/anti-D2 system is a
special case of the general supertube, and we show that there are no
open-string tachyons in this system via a computation of the open-string
one-loop vacuum energy.Comment: 1+23 pages, 2 figures, LaTeX. V2, 1+28 pages: Further generalization
to non-planar cross-sections and addition of an entirely new section with the
explicit supergravity solutions. V3, 1+30 pages: Bound on the angular
momentum added, other minor changes in Section
Search for a Heavy Particle Decaying into an Electron and a Muon with the ATLAS Detector in √s = 7 TeV pp collisions at the LHC
This Letter presents the first search for a heavy particle decaying into an e^±μ^∓ final state in √s=7 TeV pp collisions at the LHC. The data were recorded by the ATLAS detector during 2010 and correspond to a total integrated luminosity of 35 pb^(-1). No excess above the standard model background expectation is observed. Exclusions at 95% confidence level are placed on two representative models. In an R-parity violating supersymmetric model, tau sneutrinos with a mass below 0.75 TeV are excluded, assuming all R-parity violating couplings are zero except λ'_(311)=0.11 and λ_(312)=0.07. In a lepton flavor violating model, a Z′-like vector boson with masses of 0.70–1.00 TeV and corresponding cross sections times branching ratios of 0.175–0.183 pb is excluded. These results extend to higher mass R-parity violating sneutrinos and lepton flavor violating Z’s than previous constraints from the Tevatron
Measurement of the Υ (1S) production cross-section in pp collisions at √s = 7 TeV in ATLAS
A measurement of the cross-section for Υ (1S)→μ^+μ^− production in proton–proton collisions at centre of mass energy of 7 TeV is presented. The cross-section is measured as a function of the Υ (1S) transverse momentum in two bins of rapidity, |y^(Υ(1S))| 4 GeV and pseudorapidity |η^μ| < 2.5 in order to reduce theoretical uncertainties on the acceptance, which depend on the poorly known polarisation. The results are based on an integrated luminosity of 1.13 pb^(−1), collected with the ATLAS detector at the
Large Hadron Collider. The cross-section measurement is compared to theoretical predictions: it agrees
to within a factor of two with a prediction based on the NRQCD model including colour-singlet and
colour-octet matrix elements as implemented in Pythia while it disagrees by up to a factor of ten with
the next-to-leading order prediction based on the colour-singlet model
Search for pair production of first or second generation leptoquarks in proton-proton collisions at √s = 7 TeV using the ATLAS detector at the LHC
This paper describes searches for the pair production of first or second generation scalar leptoquarks using 35 pb^(-1) of proton-proton collision data recorded by the ATLAS detector at √s=7 TeV. Leptoquarks are searched in events with two oppositely-charged muons or electrons and at least two jets, and in events with one muon or electron, missing transverse momentum and at least two jets. After event selection, the observed yields are consistent with the predicted backgrounds. Leptoquark production is excluded at the 95% CL for masses M_(LQ)<376 (319) GeV and M_(LQ)<422 (362) GeV for first and second generation scalar leptoquarks, respectively, when assuming the branching fraction of a leptoquark to a charged lepton is equal to 1.0 (0.5)
Limits on the production of the standard model Higgs boson in pp collisions at √s = 7 TeV with the ATLAS detector
A search for the Standard Model Higgs boson at the Large Hadron Collider (LHC) running at a centre-of-mass energy of 7 TeV is reported, based on a total integrated luminosity of up to 40 pb^(−1) collected by the ATLAS detector in 2010. Several Higgs boson decay channels: H→γγ, H→ZZ^((∗))→ℓℓℓℓ, H→ZZ→ℓℓνν, H→ZZ→ℓℓqq, H→WW^((∗))→ℓνℓν and H→WW→ℓνqq (ℓ is e, μ) are combined in a mass range from 110 GeV to 600 GeV. The highest sensitivity is achieved in the mass range between 160 GeV and 170 GeV, where the expected 95% CL exclusion sensitivity is at Higgs boson production cross sections 2.3 times the Standard Model prediction. Upper limits on the cross section for its production are determined. Models with a fourth generation of heavy leptons and quarks with Standard Model-like couplings to the Higgs boson are also investigated and are excluded at 95% CL for a Higgs boson mass in the range from 140 GeV to 185 GeV
Statistical evaluation of the flux cross-calibration of the XMM-Newton EPIC cameras
The second XMM-Newton serendipitous source catalogue, 2XMM, provides the
ideal data base for performing a statistical evaluation of the flux
cross-calibration of the XMM-Newton European Photon Imaging Cameras (EPIC). We
aim to evaluate the status of the relative flux calibration of the EPIC cameras
on board XMM-Newton (MOS1, MOS2, and pn) and investigate the dependence of the
calibration on energy, position in the field of view of the X-ray detectors,
and lifetime of the mission. We compiled the distribution of flux percentage
differences for large samples of 'good quality' objects detected with at least
two of the EPIC cameras. The mean offset of the fluxes and dispersion of the
distributions was then found by Gaussian fitting. Count rate to flux conversion
was performed with a fixed spectral model. The impact on the results of varying
this model was investigated. Excellent agreement was found between the two EPIC
MOS cameras to better than 4% from 0.2 keV to 12.0 keV. MOS cameras register
7-9% higher flux than pn below 4.5 keV and 10-13% flux excess above 4.5 keV. No
evolution of the flux ratios is seen with time, except at energies below 0.5
keV, where we found a strong decrease in the MOS to pn flux ratio with time.
This effect is known to be due to a gradually degrading MOS redistribution
function. The flux ratios show some dependence on distance from the optical
axis in the sense that the MOS to pn flux excess increases with off-axis angle.
Furthermore, in the 4.5-12.0 keV band there is a strong dependence of the MOS
to pn excess flux on the azimuthal-angle. These results strongly suggest that
the calibration of the Reflection Grating Array (RGA) blocking factors is
incorrect at high energies. Finally, we recommend ways to improve the
calculation of fluxes in future versions of XMM-Newton source catalogues.Comment: 11 pages, 10 figures, 3 tables. Abridged Abstract. Accepted for
publication in Astronomy and Astrophysic
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