1,782 research outputs found
Kalman Filter Track Fits and Track Breakpoint Analysis
We give an overview of track fitting using the Kalman filter method in the
NOMAD detector at CERN, and emphasize how the wealth of by-product information
can be used to analyze track breakpoints (discontinuities in track parameters
caused by scattering, decay, etc.). After reviewing how this information has
been previously exploited by others, we describe extensions which add power to
breakpoint detection and characterization. We show how complete fits to the
entire track, with breakpoint parameters added, can be easily obtained from the
information from unbroken fits. Tests inspired by the Fisher F-test can then be
used to judge breakpoints. Signed quantities (such as change in momentum at the
breakpoint) can supplement unsigned quantities such as the various chisquares.
We illustrate the method with electrons from real data, and with Monte Carlo
simulations of pion decays.Comment: 27 pages including 10 figures. To appear in NI
A complete simulation of a triple-GEM detector
Since some years the gas electron multipliers (GEM)based detectors have been proposed for many different applications, in particular, in high-energy physics and astrophysics experiments and medical imaging. Many experimental measurements and tests have been performed to investigate their characteristics and performances. To achieve a better understanding of the behavior of this kind of detector the computer simulation is a very important tool. In this paper, a complete and detailed simulation of a triple-GEM-based detector is described. A method has been developed to take into account all the processes from the ionization mechanism up to the signal formation and electronic response. The results obtained are compared with experimental data and a very good agreement is achieved
Aging measurements on triple-GEM detectors operated with CF4-based gas mixtures
We present the results of a global irradiation test of full size triple-GEM detectors operated with CF 4 -based gas mixtures. This study has been performed in the framework of an R&D activity on detectors for the innermost region of the first muon station of the LHCb experiment. The prototypes have been irradiated at the Calliope facility of the ENEA-Casaccia with a high intensity 1.25 MeV Îł 60 Co source. After the irradiation test the detectors performances have been measured with X-rays and with a 3 GeV pion beam at CERN. A SEM analysis on several samples of the detectors has been performed to complete the understanding of the physical processes occurring in a GEM detector during a strong irradiation
Production and performance of LHCb triple-GEM detectors equipped with the dedicated CARDIAC-GEM front-end electronics
The production of the triple-GEM detectors for the innermost region of the first muon station of the LHCb experiment has started in February 2006, and is foreseen to be completed by the end of July. The final design of the detector and the construction procedure and tools, as well as the quality controls are defined. The performances of each detector, composed by two triple-GEM chambers equipped with dedicated CARDIAC-GEM front-end electronics, are studied with a cosmic ray telescope. The cosmic ray telescope has been set up including all the final off-detector components
Impact of depression on circulating endothelial progenitor cells in patients with acute coronary syndromes
Aims: Depression has been identified as a risk factor for an
adverse prognosis and reduced survival in patients with
acute coronary syndrome (ACS). The number of endothelial
progenitor cells (EPCs) is an independent predictor of
clinical outcomes in patients with ACS. The aim was to
evaluate the impact of depression on EPC levels in patients
with ACS.
Methods: Out of 74 ACS patients [23 non-ST-segment
elevation myocardial infarction (NSTEMI), 48 STEMI], 36 had
a diagnosis of major depressive episode (MDE) according
to Diagnostic and Statistical Manual of Mental Disorders 4th
edition (DSM-IV) criteria at the time of the inclusion in the
study. Control groups were as follows: 15 healthy
individuals and 18 patients with current MDE without a
history of cardiovascular diseases. EPCs were defined as
CD34RCD133RKDRR and evaluated by flow cytometry. All
patients underwent standardized cardiological and
psychopathological evaluations. Parametric and
nonparametric statistical tests were performed wherever
appropriate.
Results: ACS patients with MDE showed a significant
decrease in circulating EPC number compared with ACS
patients without MDE (P <0.001). The ACS study population
was then subdivided into STEMI and NSTEMI groups, and
inside each group again patients with MDE showed a
significant decrease in circulating CD34RCD133RKDRR
EPCs compared with others (P <0.001).
Conclusion: We showed that ACS patients with MDE
have a reduced number of circulating CD34RCD133RKDRR
cells compared with ACS patients without MDE, suggesting
that the presence of MDE reduces the response of bone
marrow to acute ischemic events. Considering the
reparative role of EPCs in ACS patients, we suppose that
patients with MDE might be protected less than patients
without MDE
Fabrication and Characterisation of 3D Diamond Pixel Detectors With Timing Capabilities
Diamond sensors provide a promising radiation hard solution to the challenges posed by the future experiments at hadron machines. A 3D geometry with thin columnar resistive electrodes orthogonal to the diamond surface, obtained by laser nanofabrication, is expected to provide significantly better time resolution with respect to the extensively studied planar diamond sensors. We report on the development, production, and characterisation of innovative 3D diamond sensors achieving 30% improvement in both space and time resolution with respect to sensors from the previous generation. This is the first complete characterisation of the time resolution of 3D diamond sensors and combines results from tests with laser, beta rays and high energy particle beams. Plans and strategies for further improvement in the fabrication technology and readout systems are also discussed
Intrinsic time resolution of 3D-trench silicon pixels for charged particle detection
In the last years, high-resolution time tagging has emerged as the tool to
tackle the problem of high-track density in the detectors of the next
generation of experiments at particle colliders. Time resolutions below 50ps
and event average repetition rates of tens of MHz on sensor pixels having a
pitch of 50m are typical minimum requirements. This poses an important
scientific and technological challenge on the development of particle sensors
and processing electronics. The TIMESPOT initiative (which stands for TIME and
SPace real-time Operating Tracker) aims at the development of a full prototype
detection system suitable for the particle trackers of the next-to-come
particle physics experiments. This paper describes the results obtained on the
first batch of TIMESPOT silicon sensors, based on a novel 3D MEMS (micro
electro-mechanical systems) design. Following this approach, the performance of
other ongoing silicon sensor developments has been matched and overcome, while
using a technology which is known to be robust against radiation degradation. A
time resolution of the order of 20ps has been measured at room temperature
suggesting also possible improvements after further optimisations of the
front-end electronics processing stage.Comment: This version was accepted to be published on JINST on 21/07/202
Observation of resonances consistent with pentaquark states in decays
Observations of exotic structures in the channel, that we refer to
as pentaquark-charmonium states, in decays are
presented. The data sample corresponds to an integrated luminosity of 3/fb
acquired with the LHCb detector from 7 and 8 TeV pp collisions. An amplitude
analysis is performed on the three-body final-state that reproduces the
two-body mass and angular distributions. To obtain a satisfactory fit of the
structures seen in the mass spectrum, it is necessary to include two
Breit-Wigner amplitudes that each describe a resonant state. The significance
of each of these resonances is more than 9 standard deviations. One has a mass
of MeV and a width of MeV, while the second
is narrower, with a mass of MeV and a width of MeV. The preferred assignments are of opposite parity, with one
state having spin 3/2 and the other 5/2.Comment: 48 pages, 18 figures including the supplementary material, v2 after
referee's comments, now 19 figure
Les droits disciplinaires des fonctions publiques : « unification », « harmonisation » ou « distanciation ». A propos de la loi du 26 avril 2016 relative à la déontologie et aux droits et obligations des fonctionnaires
The production of tt⟠, W+bb⟠and W+cc⟠is studied in the forward region of protonâproton collisions collected at a centre-of-mass energy of 8 TeV by the LHCb experiment, corresponding to an integrated luminosity of 1.98±0.02 fbâ1 . The W bosons are reconstructed in the decays WââÎœ , where â denotes muon or electron, while the b and c quarks are reconstructed as jets. All measured cross-sections are in agreement with next-to-leading-order Standard Model predictions.The production of , and is studied in the forward region of proton-proton collisions collected at a centre-of-mass energy of 8 TeV by the LHCb experiment, corresponding to an integrated luminosity of 1.98 0.02 \mbox{fb}^{-1}. The bosons are reconstructed in the decays , where denotes muon or electron, while the and quarks are reconstructed as jets. All measured cross-sections are in agreement with next-to-leading-order Standard Model predictions
Multidifferential study of identified charged hadron distributions in -tagged jets in proton-proton collisions at 13 TeV
Jet fragmentation functions are measured for the first time in proton-proton
collisions for charged pions, kaons, and protons within jets recoiling against
a boson. The charged-hadron distributions are studied longitudinally and
transversely to the jet direction for jets with transverse momentum 20 GeV and in the pseudorapidity range . The
data sample was collected with the LHCb experiment at a center-of-mass energy
of 13 TeV, corresponding to an integrated luminosity of 1.64 fb. Triple
differential distributions as a function of the hadron longitudinal momentum
fraction, hadron transverse momentum, and jet transverse momentum are also
measured for the first time. This helps constrain transverse-momentum-dependent
fragmentation functions. Differences in the shapes and magnitudes of the
measured distributions for the different hadron species provide insights into
the hadronization process for jets predominantly initiated by light quarks.Comment: All figures and tables, along with machine-readable versions and any
supplementary material and additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-013.html (LHCb
public pages
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