821 research outputs found
Novi ishodi suradnje NA48 o rijetkim raspadima neutralnih kaona
Recent results obtained by the NA48 collaboration on neutral kaon rare decays are reported. A first observation of KS â Ï 0γγ and a detailed study of KL,S â Ï +Ï âe +e â have been performed.IzvjeĆĄÄujemo o nedavnim ishodima suradnje NA48 o rijetkim raspadima neutralnih kaona. NaÄinili smo prvo opaĆŸanje KS â Ï 0γγ i podrobno prouÄili raspad KL,S â Ï +Ï âe +e â
Novi ishodi suradnje NA48 o rijetkim raspadima neutralnih kaona
Recent results obtained by the NA48 collaboration on neutral kaon rare decays are reported. A first observation of KS â Ï 0γγ and a detailed study of KL,S â Ï +Ï âe +e â have been performed.IzvjeĆĄÄujemo o nedavnim ishodima suradnje NA48 o rijetkim raspadima neutralnih kaona. NaÄinili smo prvo opaĆŸanje KS â Ï 0γγ i podrobno prouÄili raspad KL,S â Ï +Ï âe +e â
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
A new measurement of the K±âϱγγ decay at the NA48/2 experiment
The NA48/2 experiment at CERN collected two data samples with minimum bias trigger conditions in 2003 and 2004. A measurement of the rate and dynamic properties of the rare decay K±âϱγγK±âϱγγ from these data sets based on 149 decay candidates with an estimated background of 15.5±0.715.5±0.7 events is reported. The model-independent branching ratio in the kinematic range z=(mγγ/mK)2>0.2z=(mγγ/mK)2>0.2 is measured to be BMI(z>0.2)=(0.877±0.089)Ă10â6BMI(z>0.2)=(0.877±0.089)Ă10â6, and the branching ratio in the full kinematic range assuming a particular Chiral Perturbation Theory description to be B(KÏγγ)=(0.910±0.075)Ă10â6B(KÏγγ)=(0.910±0.075)Ă10â6
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
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
Study of Ï(2S) production and cold nuclear matter effects in pPb collisions at â sNN = 5 TeV
The production of Ï(2S) mesons is studied in dimuon final states using proton-lead (pPb) collision data collected by the LHCb detector. The data sample corresponds to an integrated luminosity of 1.6 nbâ1. The nucleon-nucleon centre-of-mass energy of the pPb collisions is (Formula presented.) TeV. The measurement is performed using Ï(2S) mesons with transverse momentum less than 14 GeV/c and rapidity y in the ranges 1.5 < y < 4.0 and â5.0 < y < â2.5 in the nucleon-nucleon centre-of-mass system. The forward-backward production ratio and the nuclear modification factor are determined for Ï(2S) mesons. Using the production cross-section results of Ï(2S) and J/Ï mesons from b-hadron decays, the (Formula presented.) cross-section in pPb collisions at (Formula presented.) TeV is obtained
Measurements of long-range near-side angular correlations in âsNN = 5 TeV proton-lead collisions in the forward region
Two-particle angular correlations are studied in proton-lead collisions at a nucleonânucleon centre-of-mass energy of âsNN = 5 TeV , collected with the LHCb detector at the LHC. The analysis is based on data recorded in two beam configurations, in which either the direction of the proton or that of the lead ion is analysed. The correlations are measured in the laboratory system as a function of relative pseudorapidity, Îη, and relative azimuthal angle, ÎÏ, for events in different classes of event activity and for different bins of particle transverse momentum. In high-activity events a long-range correlation on the near side, Î Ï â 0 , is observed in the pseudorapidity range 2.0 < η < 4.9 . This measurement of long-range correlations on the near side in proton-lead collisions extends previous observations into the forward region up to η = 4.9 . The correlation increases with growing event activity and is found to be more pronounced in the direction of the lead beam. However, the correlation in the direction of the lead and proton beams are found to be compatible when comparing events with similar absolute activity in the direction analysed
Measurement of CP violation parameters and polarisation fractions in decays
The first measurement of asymmetries in the decay and an updated measurement of its branching fraction and polarisation fractions are presented. The results are obtained using data corresponding to an integrated luminosity of of proton-proton collisions recorded with the LHCb detector at centre-of-mass energies of and . Together with constraints from , the results are used to constrain additional contributions due to penguin diagrams in the -violating phase , measured through decays to charmonium.The first measurement of CP asymmetries in the decay and an updated measurement of its branching fraction and polarisation fractions are presented. The results are obtained using data corresponding to an integrated luminosity of 3.0 fb^{â}^{1} of proton-proton collisions recorded with the LHCb detector at centre-of-mass energies of 7 and 8 TeV. Together with constraints from B â J/Ï Ï, the results are used to constrain additional contributions due to penguin diagrams in the CP -violating phase Ï , measured through B decays to charmonium.The first measurement of asymmetries in the decay and an updated measurement of its branching fraction and polarisation fractions are presented. The results are obtained using data corresponding to an integrated luminosity of of proton-proton collisions recorded with the LHCb detector at centre-of-mass energies of and . Together with constraints from , the results are used to constrain additional contributions due to penguin diagrams in the -violating phase , measured through decays to charmonium
Measurement of the J/Ï pair production cross-section in pp collisions at TeV
The production cross-section of J/Ï pairs is measured using a data sample of pp collisions collected by the LHCb experiment at a centre-of-mass energy of TeV, corresponding to an integrated luminosity of 279 ±11 pb. The measurement is performed for J/Ï mesons with a transverse momentum of less than 10 GeV/c in the rapidity range 2.0 < y < 4.5. The production cross-section is measured to be 15.2 ± 1.0 ± 0.9 nb. The first uncertainty is statistical, and the second is systematic. The differential cross-sections as functions of several kinematic variables of the J/Ï pair are measured and compared to theoretical predictions.The production cross-section of pairs is measured using a data sample of collisions collected by the LHCb experiment at a centre-of-mass energy of , corresponding to an integrated luminosity of . The measurement is performed for mesons with a transverse momentum of less than in the rapidity range . The production cross-section is measured to be . The first uncertainty is statistical, and the second is systematic. The differential cross-sections as functions of several kinematic variables of the pair are measured and compared to theoretical predictions
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