Measurement of R (D) and R (D∗) with a Semileptonic Tagging Method
The experimental results on the ratios of branching fractions R(D)=B(B→Dτ-ντ)/B(B→Dℓ-νℓ) and R(D∗)=B(B→D∗τ-ντ)/B(B→D∗ℓ-νℓ), where ℓ denotes an electron or a muon, show a long-standing discrepancy with the standard model predictions, and might hint at a violation of lepton flavor universality. We report a new simultaneous measurement of R(D) and R(D∗), based on a data sample containing 772×106 BB events recorded at the ϒ(4S) resonance with the Belle detector at the KEKB e+e- collider. In this analysis the tag-side B meson is reconstructed in a semileptonic decay mode and the signal-side τ is reconstructed in a purely leptonic decay. The measured values are R(D)=0.307±0.037±0.016 and R(D∗)=0.283±0.018±0.014, where the first uncertainties are statistical and the second are systematic. These results are in agreement with the standard model predictions within 0.2, 1.1, and 0.8 standard deviations for R(D), R(D∗), and their combination, respectively. This work constitutes the most precise measurements of R(D) and R(D∗) performed to date as well as the first result for R(D) based on a semileptonic tagging method. © 2020 authors.
A search for the lepton-flavour violating decay D0 → e ±µ ∓ is made with a dataset corresponding to an integrated luminosity of 3.0 fb−1 of proton-proton collisions at centre-of-mass energies of 7 TeV and 8 TeV, collected by the LHCb experiment. Candidate D0 mesons are selected using the decay D∗+ → D0π + and the D0 → e ±µ ∓ branching fraction is measured using the decay mode D0 → K−π + as a normalisation channel. No significant excess of D0 → e ±µ ∓ candidates over the expected background is seen, and a limit is set on the branching fraction, B(D0 → e ±µ ∓) < 1.3×10−8 , at 90% confidence level. This is an order of magnitude lower than the previous limit and it further constrains the parameter space in some leptoquark models and in supersymmetric models with R-parity violation.
The 25th International Conference on Computing in High Energy and Nuclear Physics (CHEP), organised by CERN, took place as a virtual event from 17–21 May 2021. The conference attracted 1144 registered participants from 46 different countries. There were 207 scientific presentations made over the 5 days of the conference. These were divided between 30 long talks and 2 keynotes, which were presented in plenary sessions; and 175 short talks, which were presented in parallel sessions.
During LHC Run 1, the LHCb experiment recorded around 1011 collision events. This paper describes Event Index — an event search system. Its primary function is to quickly select subsets of events from a combination of conditions, such as the estimated decay channel or number of hits in a subdetector. Event Index is essentially Apache Lucene  optimized for read-only indexes distributed over independent shards on independent nodes.
The dynamics of a two-component Davydov-Scott (DS) soliton with a small mismatch of the initial location or velocity of the high-frequency (HF) component was investigated within the framework of the Zakharov-type system of two coupled equations for the HF and low-frequency (LF) fields. In this system, the HF field is described by the linear Schrödinger equation with the potential generated by the LF component varying in time and space. The LF component in this system is described by the Korteweg-de Vries equation with a term of quadratic influence of the HF field on the LF field. The frequency of the DS soliton`s component oscillation was found analytically using the balance equation. The perturbed DS soliton was shown to be stable. The analytical results were confirmed by numerical simulations.
Radiation conditions are described for various space regions, radiation-induced effects in spacecraft materials and equipment components are considered and information on theoretical, computational, and experimental methods for studying radiation effects are presented. The peculiarities of radiation effects on nanostructures and some problems related to modeling and radiation testing of such structures are considered.
This volume presents new results in the study and optimization of information transmission models in telecommunication networks using different approaches, mainly based on theiries of queueing systems and queueing networks .
The paper provides a number of proposed draft operational guidelines for technology measurement and includes a number of tentative technology definitions to be used for statistical purposes, principles for identification and classification of potentially growing technology areas, suggestions on the survey strategies and indicators. These are the key components of an internationally harmonized framework for collecting and interpreting technology data that would need to be further developed through a broader consultation process. A summary of definitions of technology already available in OECD manuals and the stocktaking results are provided in the Annex section.