The CP violation observables S and C in the decay channel B0→D+D− are determined from a sample of proton-proton collisions at center-of-mass energies of 7 and 8 TeV, collected by the LHCb experiment and corresponding...
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The CP violation observables S and C in the decay channel B0→D+D− are determined from a sample of proton-proton collisions at center-of-mass energies of 7 and 8 TeV, collected by the LHCb experiment and corresponding to an integrated luminosity of 3 fb−1. The observable S describes CP violation in the interference between mixing and the decay amplitude, and C parametrizes direct CP violation in the decay. The following values are obtained from a flavor-tagged, decay-time-dependent analysis: S=−0.54−0.16+0.17(stat)±0.05(syst), C=0.26−0.17+0.18(stat)±0.02(syst). These values provide evidence for CP violation at a significance level of 4.0 standard deviations. The phase shift due to higher-order standard model corrections is constrained to a small value of Δϕ=−0.16−0.21+0.19 rad.
Click fraud-the deliberate clicking on advertisements with no real interest on the product or service offered-is one of the most daunting problems in online advertising. Building an effective fraud detection method is...
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Click fraud-the deliberate clicking on advertisements with no real interest on the product or service offered-is one of the most daunting problems in online advertising. Building an effective fraud detection method is thus pivotal for online advertising businesses. We organized a Fraud Detection in Mobile Advertising (FDMA) 2012 Competition, opening the opportunity for participants to work on real-world fraud data from BuzzCity Pte. Ltd., a global mobile advertising company based in Singapore. In particular, the task is to identify fraudulent publishers who generate illegitimate clicks, and distinguish them from normal publishers. The competition was held from September 1 to September 30, 2012, attracting 127 teams from more than 15 countries. The mobile advertising data are unique and complex, involving heterogeneous information, noisy patterns with missing values, and highly imbalanced class distribution. The competition results provide a comprehensive study on the usability of data mining-based fraud detection approaches in practical setting. Our principal findings are that features derived from fine-grained time-series analysis are crucial for accurate fraud detection, and that ensemble methods offer promising solutions to highly-imbalanced nonlinear classification tasks with mixed variable types and noisy/missing patterns. The competition data remain available for further studies at http://***/fdma2012/.
The Dalitz plot analysis technique is used to study the resonant substructures of B−→D+π−π− decays in a data sample corresponding to 3.0 fb−1 of pp collision data recorded by the LHCb experiment during 2011 and 20...
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The Dalitz plot analysis technique is used to study the resonant substructures of B−→D+π−π− decays in a data sample corresponding to 3.0 fb−1 of pp collision data recorded by the LHCb experiment during 2011 and 2012. A model-independent analysis of the angular moments demonstrates the presence of resonances with spins 1, 2 and 3 at high D+π− mass. The data are fitted with an amplitude model composed of a quasi-model-independent function to describe the D+π− S wave together with virtual contributions from the D*(2007)0 and B*0 states, and components corresponding to the D2*(2460)0, D1*(2680)0, D3*(2760)0 and D2*(3000)0 resonances. The masses and widths of these resonances are determined together with the branching fractions for their production in B−→D+π−π− decays. The D+π− S wave has phase motion consistent with that expected due to the presence of the D0*(2400)0 state. These results constitute the first observations of the D3*(2760)0 and D2*(3000)0 resonances, with significances of 10σ and 6.6σ, respectively.
Amplitude models are applied to studies of resonance structure in D0→KS0K−π+ and D0→KS0K+π− decays using pp collision data corresponding to an integrated luminosity of 3.0 fb−1 collected by the LHCb experiment. R...
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Amplitude models are applied to studies of resonance structure in D0→KS0K−π+ and D0→KS0K+π− decays using pp collision data corresponding to an integrated luminosity of 3.0 fb−1 collected by the LHCb experiment. Relative magnitude and phase information is determined, and coherence factors and related observables are computed for both the whole phase space and a restricted region of 100 MeV/c2 around the K*(892)± resonance. Two formulations for the Kπ S-wave are used, both of which give a good description of the data. The ratio of branching fractions B(D0→KS0K+π−)/B(D0→KS0K−π+) is measured to be 0.655±0.004(stat)±0.006(syst) over the full phase space and 0.370±0.003(stat)±0.012(syst) in the restricted region. A search for CP violation is performed using the amplitude models and no significant effect is found. Predictions from SU(3) flavor symmetry for K*(892)K amplitudes of different charges are compared with the amplitude model results.
The B+→D+K+π− decay is observed in a data sample corresponding to 3.0 fb−1 of pp collision data recorded by the LHCb experiment during 2011 and 2012. The signal significance is 8σ and the branching fraction is mea...
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The B+→D+K+π− decay is observed in a data sample corresponding to 3.0 fb−1 of pp collision data recorded by the LHCb experiment during 2011 and 2012. The signal significance is 8σ and the branching fraction is measured to be B(B+→D+K+π−)=(5.31±0.90±0.48±0.35)×10−6, where the uncertainties are statistical, systematic and due to the normalization mode B+→D−K+π+, respectively. The Dalitz plot appears to be dominated by broad structures. Angular distributions are exploited to search for quasi-two-body contributions from B+→D2*(2460)0K+ and B+→D+K*(892)0 decays. No significant signals are observed and upper limits are set on their branching fractions.
The branching fraction of the decay Bs0→Ds(*)+Ds(*)− is measured using pp collision data corresponding to an integrated luminosity of 1.0 fb−1, collected using the LHCb detector at a center-of-mass energy of 7 TeV. ...
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The branching fraction of the decay Bs0→Ds(*)+Ds(*)− is measured using pp collision data corresponding to an integrated luminosity of 1.0 fb−1, collected using the LHCb detector at a center-of-mass energy of 7 TeV. It is found to be B(Bs0→Ds(*)+Ds(*)−)=(3.05±0.10±0.20±0.34)%, where the uncertainties are statistical, systematic, and due to the normalization channel, respectively. The branching fractions of the individual decays corresponding to the presence of one or two Ds*± are also measured. The individual branching fractions are found to be B(Bs0→Ds*±Ds∓)=(1.35±0.06±0.09±0.15)%, B(Bs0→Ds*+Ds*−)=(1.27±0.08±0.10±0.14)%. All three results are the most precise determinations to date.
A study of Bc+→K+K−π+ decays is performed for the first time using data corresponding to an integrated luminosity of 3.0 fb−1 collected by the LHCb experiment in pp collisions at center-of-mass energies of 7 and 8 ...
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A study of Bc+→K+K−π+ decays is performed for the first time using data corresponding to an integrated luminosity of 3.0 fb−1 collected by the LHCb experiment in pp collisions at center-of-mass energies of 7 and 8 TeV. Evidence for the decay Bc+→χc0(→K+K−)π+ is reported with a significance of 4.0 standard deviations, giving σ(Bc+)σ(B+)×B(Bc+→χc0π+)=(9.8−3.0+3.4(stat)±0.8(syst))×10−6. Here B denotes a branching fraction while σ(Bc+) and σ(B+) are the production cross sections for Bc+ and B+ mesons. An indication of b¯c weak annihilation is found for the region m(K−π+)<1.834 GeV/c2, with a significance of 2.4 standard deviations.
A full amplitude analysis of Λb0→J/ψpπ− decays is performed with a data sample acquired with the LHCb detector from 7 and 8 TeV pp collisions, corresponding to an integrated luminosity of 3 fb−1. A significantly ...
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A full amplitude analysis of Λb0→J/ψpπ− decays is performed with a data sample acquired with the LHCb detector from 7 and 8 TeV pp collisions, corresponding to an integrated luminosity of 3 fb−1. A significantly better description of the data is achieved when, in addition to the previously observed nucleon excitations N→pπ−, either the Pc(4380)+ and Pc(4450)+→J/ψp states, previously observed in Λb0→J/ψpK− decays, or the Zc(4200)−→J/ψπ− state, previously reported in B0→J/ψK+π− decays, or all three, are included in the amplitude models. The data support a model containing all three exotic states, with a significance of more than three standard deviations. Within uncertainties, the data are consistent with the Pc(4380)+ and Pc(4450)+ production rates expected from their previous observation taking account of Cabibbo suppression.
Violations of CPT symmetry and Lorentz invariance are searched for by studying interference effects in B0 mixing and in Bs0 mixing. Samples of B0→J/ψKS0 and Bs0→J/ψK+K− decays are recorded by the LHCb detector in ...
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Violations of CPT symmetry and Lorentz invariance are searched for by studying interference effects in B0 mixing and in Bs0 mixing. Samples of B0→J/ψKS0 and Bs0→J/ψK+K− decays are recorded by the LHCb detector in proton-proton collisions at center-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3 fb−1. No periodic variations of the particle-antiparticle mass differences are found, consistent with Lorentz invariance and CPT symmetry. Results are expressed in terms of the standard model extension parameter Δaμ with precisions of O(10−15) and O(10−14) GeV for the B0 and Bs0 systems, respectively. With no assumption on Lorentz (non)invariance, the CPT-violating parameter z in the Bs0 system is measured for the first time and found to be Re(z)=−0.022±0.033±0.005 and Im(z)=0.004±0.011±0.002, where the first uncertainties are statistical and the second systematic.
A proton-proton collision data sample, corresponding to an integrated luminosity of 3 fb−1 collected by LHCb at s=7 and 8 TeV, is used to reconstruct 63±9 Ωb−→Ωc0π−, Ωc0→pK−K−π+ decays. Using the Ξb−→...
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A proton-proton collision data sample, corresponding to an integrated luminosity of 3 fb−1 collected by LHCb at s=7 and 8 TeV, is used to reconstruct 63±9 Ωb−→Ωc0π−, Ωc0→pK−K−π+ decays. Using the Ξb−→Ξc0π−, Ξc0→pK−K−π+ decay mode for calibration, the lifetime ratio and the absolute lifetime of the Ωb− baryon are measured to be τΩb−/τΞb−=1.11±0.16±0.03, τΩb−=1.78±0.26±0.05±0.06 ps, where the uncertainties are statistical, systematic and from the calibration mode (for τΩb− only). A measurement is also made of the mass difference, mΩb−−mΞb−, and the corresponding Ωb− mass, which yields mΩb−−mΞb−=247.4±3.2±0.5 MeV/c2, mΩb−=6045.1±3.2±0.5±0.6 MeV/c2. These results are consistent with previous measurements.
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