2,005 research outputs found
A prototype personal aerosol sampler based on electrostatic precipitation and electrowetting-on-dielectric actuation of droplets
This is an Open Access article, distributed under the terms of the Open Government Licence. http://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/ Crown Copyright © 2016. Published by Elsevier Ltd. All rights reserved. The version of record (T. G. Foat, et al, 'A prototype personal aerosol sampler based on electrostatic precipitation and electrowetting-on-dielectric actuation of droplets', Journal of Aerosol Science, Vol. 95, pp. 43-53, May 2016) is available online at doi: https://doi.org/10.1016/j.jaerosci.2016.01.007.An electrostatic precipitator (ESP) based personal sampler with a laboratory based electrowetting-on-dielectric (EWOD) concentrator could provide a high concentration rate personal aerosol sampler system. A prototype system has been developed based on the concept of a lightweight personal ESP collecting aerosol particles onto a hydrophobic surface followed by the use of an EWOD actuated droplet system to transfer the deposited sample into a microlitre size water droplet.A personal sampler system could provide military or civilian personnel with a wide area biological monitoring capability supplying information on who has been infected, what they have been infected with, how much material they were exposed to and possibly where and when they were infected. Current commercial-off-the-shelf (COTS) personal sampler solutions can be bulky and use volumes of water to extract the sample that are typically a thousand times greater than the proposed method.Testing of the prototype ESP at a sample flow rate of 5Lmin-1 demonstrated collection efficiencies greater than 80% for sodium fluorescein particles larger than 4μm diameter and of approximately 50% at 1.5μm. The ESP-EWOD system collection efficiency measured for Bacillus atrophaeus (BG) spores with an air sample flow rate of 20L min-1 was 2.7% with a concentration rate of 1.9×105 min-1. This was lower than expected due to the corona ions from the ESP affecting the hydrophobicity of the collection surface and hence the EWOD efficiency. However, even with this low efficiency the concentration rate is more than an order of magnitude higher than the theoretical maximum of the best current COTS personal sampler. For an optimised system, ESP-EWOD system efficiency should be higher than 32% with a comparable increase in concentration rate.Peer reviewe
Improved performance of the LHCb Outer Tracker in LHC Run 2
The LHCb Outer Tracker is a gaseous detector covering an area of with 12 double layers of straw tubes. The performance of the detector is
presented based on data of the LHC Run 2 running period from 2015 and 2016.
Occupancies and operational experience for data collected in , pPb and
PbPb collisions are described. An updated study of the ageing effects is
presented showing no signs of gain deterioration or other radiation damage
effects. In addition several improvements with respect to LHC Run 1 data taking
are introduced. A novel real-time calibration of the time-alignment of the
detector and the alignment of the single monolayers composing detector modules
are presented, improving the drift-time and position resolution of the detector
by 20\%. Finally, a potential use of the improved resolution for the timing of
charged tracks is described, showing the possibility to identify low-momentum
hadrons with their time-of-flight.Comment: 29 pages, 20 figures, minor changes to match the published versio
Charge collection properties of prototype sensors for the LHCb VELO upgrade
An extensive sensor testing campaign is presented, dedicated to measuring the
charge collection properties of prototype candidates for the Vertex Locator
(VELO) detector for the upgraded LHCb experiment. The charge collection is
measured with sensors exposed to fluences of up to , as well as with nonirradiated prototypes. The results are
discussed, including the influence of different levels of irradiation and bias
voltage on the charge collection properties. Charge multiplication is observed
on some sensors that were nonuniformly irradiated with 24 GeV protons, to the
highest fluence levels. An analysis of the charge collection near the guard
ring region is also presented, revealing significant differences between the
sensor prototypes. All tested sensor variants succeed in collecting the minimum
required charge of 6000 electrons after the exposure to the maximum fluence
Bose-Einstein correlations of same-sign charged pions in the forward region in pp collisions at √s=7 TeV
Bose-Einstein correlations of same-sign charged pions, produced in protonproton collisions at a 7 TeV centre-of-mass energy, are studied using a data sample collected
by the LHCb experiment. The signature for Bose-Einstein correlations is observed in the
form of an enhancement of pairs of like-sign charged pions with small four-momentum
difference squared. The charged-particle multiplicity dependence of the Bose-Einstein correlation parameters describing the correlation strength and the size of the emitting source
is investigated, determining both the correlation radius and the chaoticity parameter. The
measured correlation radius is found to increase as a function of increasing charged-particle
multiplicity, while the chaoticity parameter is seen to decreas
Observation of two new baryon resonances
Two structures are observed close to the kinematic threshold in the mass spectrum in a sample of proton-proton collision data, corresponding
to an integrated luminosity of 3.0 fb recorded by the LHCb experiment.
In the quark model, two baryonic resonances with quark content are
expected in this mass region: the spin-parity and
states, denoted and .
Interpreting the structures as these resonances, we measure the mass
differences and the width of the heavier state to be
MeV,
MeV,
MeV, where the first and second
uncertainties are statistical and systematic, respectively. The width of the
lighter state is consistent with zero, and we place an upper limit of
MeV at 95% confidence level. Relative
production rates of these states are also reported.Comment: 17 pages, 2 figure
Observation of an Excited Bc+ State
Using pp collision data corresponding to an integrated luminosity of 8.5 fb-1 recorded by the LHCb experiment at center-of-mass energies of s=7, 8, and 13 TeV, the observation of an excited Bc+ state in the Bc+π+π- invariant-mass spectrum is reported. The observed peak has a mass of 6841.2±0.6(stat)±0.1(syst)±0.8(Bc+) MeV/c2, where the last uncertainty is due to the limited knowledge of the Bc+ mass. It is consistent with expectations of the Bc∗(2S31)+ state reconstructed without the low-energy photon from the Bc∗(1S31)+→Bc+γ decay following Bc∗(2S31)+→Bc∗(1S31)+π+π-. A second state is seen with a global (local) statistical significance of 2.2σ (3.2σ) and a mass of 6872.1±1.3(stat)±0.1(syst)±0.8(Bc+) MeV/c2, and is consistent with the Bc(2S10)+ state. These mass measurements are the most precise to date
Study of boson production in association with beauty and charm
The associated production of a boson with a jet originating from either a
light parton or heavy-flavor quark is studied in the forward region using
proton-proton collisions. The analysis uses data corresponding to integrated
luminosities of 1.0 and collected with the LHCb detector
at center-of-mass energies of 7 and 8 TeV, respectively. The bosons are
reconstructed using the decay and muons with a transverse
momentum, , larger than 20 GeV in the pseudorapidity range
GeV
and . The sum of the muon and jet momenta must satisfy
GeV. The fraction of jet events that originate from beauty
and charm quarks is measured, along with the charge asymmetries of the
and production cross-sections. The ratio of the jet to
jet production cross-sections is also measured using the
decay. All results are in agreement with Standard Model predictions
Search for the rare decays and
A search for the rare decay of a or meson into the final
state is performed, using data collected by the LHCb experiment
in collisions at and TeV, corresponding to an integrated
luminosity of 3 fb. The observed number of signal candidates is
consistent with a background-only hypothesis. Branching fraction values larger
than for the decay mode are
excluded at 90% confidence level. For the decay
mode, branching fraction values larger than are excluded at
90% confidence level, this is the first branching fraction limit for this
decay.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2015-044.htm
Measurement of the mass and lifetime of the baryon
A proton-proton collision data sample, corresponding to an integrated
luminosity of 3 fb collected by LHCb at and 8 TeV, is used
to reconstruct , decays. Using the , decay mode for calibration, the lifetime ratio and absolute
lifetime of the baryon are measured to be \begin{align*}
\frac{\tau_{\Omega_b^-}}{\tau_{\Xi_b^-}} &= 1.11\pm0.16\pm0.03, \\
\tau_{\Omega_b^-} &= 1.78\pm0.26\pm0.05\pm0.06~{\rm ps}, \end{align*} where the
uncertainties are statistical, systematic and from the calibration mode (for
only). A measurement is also made of the mass difference,
, and the corresponding mass, which
yields \begin{align*} m_{\Omega_b^-}-m_{\Xi_b^-} &= 247.4\pm3.2\pm0.5~{\rm
MeV}/c^2, \\ m_{\Omega_b^-} &= 6045.1\pm3.2\pm 0.5\pm0.6~{\rm MeV}/c^2.
\end{align*} These results are consistent with previous measurements.Comment: 11 pages, 5 figures, All figures and tables, along with any
supplementary material and additional information, are available at
https://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2016-008.htm
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