360 research outputs found
Event Data Definition in LHCb
We present the approach used for defining the event object model for the LHCb
experiment. This approach is based on a high level modelling language, which is
independent of the programming language used in the current implementation of
the event data processing software. The different possibilities of object
modelling languages are evaluated, and the advantages of a dedicated model
based on XML over other possible candidates are shown. After a description of
the language itself, we explain the benefits obtained by applying this approach
in the description of the event model of an experiment such as LHCb. Examples
of these benefits are uniform and coherent mapping of the object model to the
implementation language across the experiment software development teams, easy
maintenance of the event model, conformance to experiment coding rules, etc.
The description of the object model is parsed by means of a so called
front-end which allows to feed several back-ends. We give an introduction to
the model itself and to the currently implemented back-ends which produce
information like programming language specific implementations of event objects
or meta information about these objects. Meta information can be used for
introspection of objects at run-time which is essential for functionalities
like object persistency or interactive analysis. This object introspection
package for C++ has been adopted by the LCG project as the starting point for
the LCG object dictionary that is going to be developed in common for the LHC
experiments.
The current status of the event object modelling and its usage in LHCb are
presented and the prospects of further developments are discussed.Comment: Talk from the 2003 Computing in High Energy and Nuclear Physics
(CHEP03), La Jolla, Ca, USA, March 2003, 7 pages, LaTeX, 2 eps figures. PSN
MOJT00
Design and engineering of a simplified workflow execution for the MG5aMC event generator on GPUs and vector CPUs
Physics event generators are essential components of the data analysis
software chain of high energy physics experiments, and important consumers of
their CPU resources. Improving the software performance of these packages on
modern hardware architectures, such as those deployed at HPC centers, is
essential in view of the upcoming HL-LHC physics programme. In this paper, we
describe an ongoing activity to reengineer the Madgraph5_aMC@NLO physics event
generator, primarily to port it and allow its efficient execution on GPUs, but
also to modernize it and optimize its performance on vector CPUs. We describe
the motivation, engineering process and software architecture design of our
developments, as well as the current challenges and future directions for this
project. This paper is based on our submission to vCHEP2021 in March
2021,complemented with a few preliminary results that we presented during the
conference. Further details and updated results will be given in later
publications.Comment: 17 pages, 6 figures, submitted to vCHEP2021 proceedings in EPJ Web of
Conferences; minor changes to address comments from the EPJWOC reviewe
Speeding up Madgraph5 aMC@NLO through CPU vectorization and GPU offloading: towards a first alpha release
The matrix element (ME) calculation in any Monte Carlo physics event
generator is an ideal fit for implementing data parallelism with lockstep
processing on GPUs and vector CPUs. For complex physics processes where the ME
calculation is the computational bottleneck of event generation workflows, this
can lead to large overall speedups by efficiently exploiting these hardware
architectures, which are now largely underutilized in HEP. In this paper, we
present the status of our work on the reengineering of the Madgraph5_aMC@NLO
event generator at the time of the ACAT2022 conference. The progress achieved
since our previous publication in the ICHEP2022 proceedings is discussed, for
our implementations of the ME calculations in vectorized C++, in CUDA and in
the SYCL framework, as well as in their integration into the existing MadEvent
framework. The outlook towards a first alpha release of the software supporting
QCD LO processes usable by the LHC experiments is also discussed.Comment: 7 pages, 4 figures, 4 tables; submitted to ACAT 2022 proceedings in
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A Roadmap for HEP Software and Computing R&D for the 2020s
Particle physics has an ambitious and broad experimental programme for the coming decades. This programme requires large investments in detector hardware, either to build new facilities and experiments, or to upgrade existing ones. Similarly, it requires commensurate investment in the R&D of software to acquire, manage, process, and analyse the shear amounts of data to be recorded. In planning for the HL-LHC in particular, it is critical that all of the collaborating stakeholders agree on the software goals and priorities, and that the efforts complement each other. In this spirit, this white paper describes the R&D activities required to prepare for this software upgrade.Peer reviewe
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
Observation of the B0 â Ï0Ï0 decay from an amplitude analysis of B0 â (Ï+Ïâ)(Ï+Ïâ) decays
Protonâproton collision data recorded in 2011 and 2012 by the LHCb experiment, corresponding to an integrated luminosity of 3.0 fbâ1 , are analysed to search for the charmless B0âÏ0Ï0 decay. More than 600 B0â(Ï+Ïâ)(Ï+Ïâ) signal decays are selected and used to perform an amplitude analysis, under the assumption of no CP violation in the decay, from which the B0âÏ0Ï0 decay is observed for the first time with 7.1 standard deviations significance. The fraction of B0âÏ0Ï0 decays yielding a longitudinally polarised final state is measured to be fL=0.745â0.058+0.048(stat)±0.034(syst) . The B0âÏ0Ï0 branching fraction, using the B0âÏKâ(892)0 decay as reference, is also reported as B(B0âÏ0Ï0)=(0.94±0.17(stat)±0.09(syst)±0.06(BF))Ă10â6
Observation of the decay B0sâÏ(2S)K+Ïâ
The decay BÂŻs0âÏ(2S)K+Ïâ is observed using a data set corresponding to an integrated luminosity of 3.0 fbâ1 collected by the LHCb experiment in pp collisions at centre-of-mass energies of 7 and 8 TeV. The branching fraction relative to the B0âÏ(2S)K+Ïâ decay mode is measured to be B(BÂŻs0âÏ(2S)K+Ïâ)B(B0âÏ(2S)K+Ïâ)=5.38±0.36(stat)±0.22(syst)±0.31(fs/fd)%, where fs/fd indicates the uncertainty due to the ratio of probabilities for a b quark to hadronise into a Bs0 or B0 meson. Using an amplitude analysis, the fraction of decays proceeding via an intermediate Kâ(892)0 meson is measured to be 0.645±0.049(stat)±0.049(syst) and its longitudinal polarisation fraction is 0.524±0.056(stat)±0.029(syst) . The relative branching fraction for this component is determined to be B(BÂŻs0âÏ(2S)Kâ(892)0)B(B0âÏ(2S)Kâ(892)0)=5.58±0.57(stat)±0.40(syst)±0.32(fs/fd)%. In addition, the mass splitting between the Bs0 and B0 mesons is measured as M(Bs0)âM(B0)=87.45±0.44(stat)±0.09(syst) MeV/c2
A study of CP violation in B-+/- -> DK +/- and B-+/- -> D pi(+/-) decays with D -> (KSK +/-)-K-0 pi(-/+) final states
A first study of CP violation in the decay modes and , where labels a or meson and labels a or meson, is performed. The analysis uses the LHCb data set collected in collisions, corresponding to an integrated luminosity of 3 fb. The analysis is sensitive to the CP-violating CKM phase through seven observables: one charge asymmetry in each of the four modes and three ratios of the charge-integrated yields. The results are consistent with measurements of using other decay modes
Study of the rare B-s(0) and B-0 decays into the pi(+) pi(-) mu(+) mu(-) final state
A search for the rare decays and is performed in a data set corresponding to an integrated luminosity of 3.0 fb collected by the LHCb detector in proton-proton collisions at centre-of-mass energies of 7 and 8 TeV. Decay candidates with pion pairs that have invariant mass in the range 0.5-1.3 GeV/ and with muon pairs that do not originate from a resonance are considered. The first observation of the decay and the first evidence of the decay are obtained and the branching fractions are measured to be and , where the third uncertainty is due to the branching fraction of the decay , used as a normalisation.A search for the rare decays Bs0âÏ+ÏâÎŒ+ÎŒâ and B0âÏ+ÏâÎŒ+ÎŒâ is performed in a data set corresponding to an integrated luminosity of 3.0 fbâ1 collected by the LHCb detector in protonâproton collisions at centre-of-mass energies of 7 and 8 TeV . Decay candidates with pion pairs that have invariant mass in the range 0.5â1.3 GeV/c2 and with muon pairs that do not originate from a resonance are considered. The first observation of the decay Bs0âÏ+ÏâÎŒ+ÎŒâ and the first evidence of the decay B0âÏ+ÏâÎŒ+ÎŒâ are obtained and the branching fractions, restricted to the dipion-mass range considered, are measured to be B(Bs0âÏ+ÏâÎŒ+ÎŒâ)=(8.6±1.5 (stat)±0.7 (syst)±0.7(norm))Ă10â8 and B(B0âÏ+ÏâÎŒ+ÎŒâ)=(2.11±0.51(stat)±0.15(syst)±0.16(norm))Ă10â8 , where the third uncertainty is due to the branching fraction of the decay B0âJ/Ï(âÎŒ+ÎŒâ)Kâ(892)0(âK+Ïâ) , used as a normalisation.A search for the rare decays Bs0âÏ+ÏâÎŒ+ÎŒâ and B0âÏ+ÏâÎŒ+ÎŒâ is performed in a data set corresponding to an integrated luminosity of 3.0 fbâ1 collected by the LHCb detector in protonâproton collisions at centre-of-mass energies of 7 and 8 TeV . Decay candidates with pion pairs that have invariant mass in the range 0.5â1.3 GeV/c2 and with muon pairs that do not originate from a resonance are considered. The first observation of the decay Bs0âÏ+ÏâÎŒ+ÎŒâ and the first evidence of the decay B0âÏ+ÏâÎŒ+ÎŒâ are obtained and the branching fractions, restricted to the dipion-mass range considered, are measured to be B(Bs0âÏ+ÏâÎŒ+ÎŒâ)=(8.6±1.5 (stat)±0.7 (syst)±0.7(norm))Ă10â8 and B(B0âÏ+ÏâÎŒ+ÎŒâ)=(2.11±0.51(stat)±0.15(syst)±0.16(norm))Ă10â8 , where the third uncertainty is due to the branching fraction of the decay B0âJ/Ï(âÎŒ+ÎŒâ)Kâ(892)0(âK+Ïâ) , used as a normalisation.A search for the rare decays and is performed in a data set corresponding to an integrated luminosity of 3.0 fb collected by the LHCb detector in proton-proton collisions at centre-of-mass energies of 7 and 8 TeV. Decay candidates with pion pairs that have invariant mass in the range 0.5-1.3 GeV/ and with muon pairs that do not originate from a resonance are considered. The first observation of the decay and the first evidence of the decay are obtained and the branching fractions, restricted to the dipion-mass range considered, are measured to be and , where the third uncertainty is due to the branching fraction of the decay , used as a normalisation
Measurement of the (eta c)(1S) production cross-section in proton-proton collisions via the decay (eta c)(1S) -> p(p)over-bar
The production of the state in proton-proton collisions is probed via its decay to the final state with the LHCb detector, in the rapidity range GeV/c. The cross-section for prompt production of mesons relative to the prompt cross-section is measured, for the first time, to be at a centre-of-mass energy TeV using data corresponding to an integrated luminosity of 0.7 fb, and at TeV using 2.0 fb. The uncertainties quoted are, in order, statistical, systematic, and that on the ratio of branching fractions of the and decays to the final state. In addition, the inclusive branching fraction of -hadron decays into mesons is measured, for the first time, to be , where the third uncertainty includes also the uncertainty on the inclusive branching fraction from -hadron decays. The difference between the and meson masses is determined to be MeV/c.The production of the state in proton-proton collisions is probed via its decay to the final state with the LHCb detector, in the rapidity range . The cross-section for prompt production of mesons relative to the prompt cross-section is measured, for the first time, to be at a centre-of-mass energy using data corresponding to an integrated luminosity of 0.7Â fb , and at using 2.0Â fb . The uncertainties quoted are, in order, statistical, systematic, and that on the ratio of branching fractions of the and decays to the final state. In addition, the inclusive branching fraction of -hadron decays into mesons is measured, for the first time, to be , where the third uncertainty includes also the uncertainty on the inclusive branching fraction from -hadron decays. The difference between the and meson masses is determined to be .The production of the state in proton-proton collisions is probed via its decay to the final state with the LHCb detector, in the rapidity range GeV/c. The cross-section for prompt production of mesons relative to the prompt cross-section is measured, for the first time, to be at a centre-of-mass energy TeV using data corresponding to an integrated luminosity of 0.7 fb, and at TeV using 2.0 fb. The uncertainties quoted are, in order, statistical, systematic, and that on the ratio of branching fractions of the and decays to the final state. In addition, the inclusive branching fraction of -hadron decays into mesons is measured, for the first time, to be , where the third uncertainty includes also the uncertainty on the inclusive branching fraction from -hadron decays. The difference between the and meson masses is determined to be MeV/c
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