1,256 research outputs found
Spatial resolution and efficiency of prototype sensors for the LHCb VELO Upgrade
A comprehensive study of the spatial resolution and detection efficiency of
sensor prototypes developed for the LHCb VELO upgrade is presented. Data
samples were collected at the CERN SPS H8 beam line using a hadron mixture of
protons and pions with momenta of approximately 180 GeV/c. The sensor
performance was characterised using both irradiated and non-irradiated sensors.
Irradiated samples were subjected to a maximum fluence of
, of both protons and neutrons.
The spatial resolution is measured comparing the detected hits to the position
as predicted by tracks reconstructed by the Timepix3 telescope. The resolution
is presented for different applied bias voltages and track angles, sensor
thickness and implant size.Comment: 18 pages, 15 Figure
Digital Radiography Inspection of Flexible Risers in Offshore Oil and Gas Industry
This paper presents the development of a digital radiography-based system for sub-sea applications that is being implemented within the context of a H2020 EU funded project called "RiserSure". The system is capable of performing semi-automatic in-situ integrity inspections and providing detailed information on any damage to the metallic layers of flexible risers, without the need to remove the coating layer. The integrated system comprises a subsea digital radiography linear detector array coupled to a commercially available marinised gamma ray source, and a bespoke developed versatile scanning system for deploying the radiography units under subsea conditions for performing precise all-round scanning of risers. Preliminary site shallow sea trials of the prototype system were conducted at the Underwater Centre facilities in Fort William, Scotland. The results, discussed in this paper, validated the effective underwater application and performance capabilities of the system in controlled shallow sea operating conditions, and show the potential for offering reliable and highly accurate radiographic inspection of risers. Finally, from the site trials, the requirements for further system improvements were identified for real-world deployment
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
Quantum numbers of the state and orbital angular momentum in its decay
Angular correlations in decays, with , and , are used to measure
orbital angular momentum contributions and to determine the value of
the meson. The data correspond to an integrated luminosity of 3.0
fb of proton-proton collisions collected with the LHCb detector. This
determination, for the first time performed without assuming a value for the
orbital angular momentum, confirms the quantum numbers to be .
The is found to decay predominantly through S wave and an upper limit
of at C.L. is set on the fraction of D wave.Comment: 16 pages, 4 figure
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 the decay
The decay is observed for the first
time, using proton-proton collisions collected with the LHCb detector
corresponding to an integrated luminosity of 3fb. A signal yield of
decays is reported with a significance of 6.2 standard deviations.
The ratio of the branching fraction of \B_c \rightarrow J/\psi K^+ K^- \pi^+
decays to that of decays is measured to be
, where the first uncertainty is statistical and the
second is systematic.Comment: 18 pages, 2 figure
Observation of associated production of a boson with a meson in the~forward region
A search for associated production of a boson with an open charm meson is
presented using a data sample, corresponding to an integrated luminosity of
of proton--proton collisions at a centre-of-mass energy
of 7\,TeV, collected by the LHCb experiment. %% Seven candidate events for
associated production of a boson with a meson and four candidate
events for a boson with a meson are observed with a combined
significance of 5.1standard deviations. The production cross-sections in the
forward region are measured to be where the first uncertainty is statistical and the
second systematic.Comment: 18 pages, 2 figure
Differential branching fraction and angular analysis of the decay B0→K∗0μ+μ−
The angular distribution and differential branching fraction of the decay B 0→ K ∗0 μ + μ − are studied using a data sample, collected by the LHCb experiment in pp collisions at s√=7 TeV, corresponding to an integrated luminosity of 1.0 fb−1. Several angular observables are measured in bins of the dimuon invariant mass squared, q 2. A first measurement of the zero-crossing point of the forward-backward asymmetry of the dimuon system is also presented. The zero-crossing point is measured to be q20=4.9±0.9GeV2/c4 , where the uncertainty is the sum of statistical and systematic uncertainties. The results are consistent with the Standard Model predictions
Observation of the decay
The first observation of the decay is reported. The
study is based on a sample of proton-proton collisions corresponding to
of integrated luminosity collected with the LHCb detector. The
significance of the signal is standard deviations. The branching fraction
is measured to be , where the third uncertainty comes from the
branching fraction that is used as a normalisation.
In addition, the charge asymmetries of and
, which are control channels, are measured to be and , respectively. All results are consistent with
theoretical expectations
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