1,721,797 research outputs found
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Searches for lepton flavour violation and lepton number violation at LHCb
No full textSearches for lepton flavour and lepton number violating decays at LHCb are presented in various τ and D decays. Lepton flavour violating decays are forbidden in the Standard Model, they are considered as a probe for New Physics. Those searches are performed using pp collision data recorded by LHCb experiment in 2011. In addition searches for Majorana neutrinos in B+ decays with like-sign μ pair in the final states are summarized. No signal was observed at 95% confidence level for all these decays. Upper limits are set on the branching fractions of corresponding decay modes
Search for New Physics in the decay channel at LHCb
No full textIn the channel, the phase is predicted to be significantly small in the Standard Model. This observable is an excellent probe for New Physics because the mixing takes place via a loop diagram where new particles is expected to intervene. These two reasons makes the parameter an excellent probe for New Physics processes. We developed a simplified selection for the 2010 data. It avoids any bias on the proper time distribution in order to reduce systematic uncertainty. In addition, we control the tagging performance for events using the similar and channels. With the 2010 data, we obtain 570 signal events in 36 pb of integrated luminosity, a tagging power of (2.2 ± 0.4) % and a proper time resolution of 50 fs. We investigated an alternative selection which maximizes the sensitivity using a proper time biasing cuts. We proposed a data-driven method to correct the proper time acceptance. We designed a fitting program to determine the phase. With the 2010 data, It is found to be: = [−2.7,−0.5] rad at 68 % of confidence. This result is compatible with the Standard Model prediction
Recherche de nouvelle physique dans le canal B⁰s → J/ψφ auprès de l’expérience LHCb
No full textDans le Modèle Standard, la différence de phase apparaissant dans la désintégration B⁰s→J/ψφ est prédite avec une grande précision. Cette observable est une sonde pour mettre en évidence de la Nouvelle Physique car l’oscillation B⁰s-⁻B⁰s s’effectue via un diagramme en boucles sensible aux nouvelles particules. Nous avons développé une sélection simplifiée pour les données de 2010. Elle évite tous biais sur la distribution en temps propre afin de réduire l’incertitude systématique. De plus, nous contrôlons les performances d’étiquetage pour les événements B⁰s→J/ψφ en utilisant les canaux similaires B⁰d→J/ψK∗⁰ et B⁺→J/ψK⁺. Avec les données de 2010, nous obtenons 570 événements de signal avec une luminosité intégré de 36 pb−1, une puissance de d’étiquetage de (2, 2±0, 4)% et une résolution temporelle de 50 fs. Nous avons étudié une sélection alternative, qui maximise la sensibilité à la phase φs en utilisant des coupures biaisant le temps propre. Nous avons proposé une méthode pour corriger la déformation de temps propre à partir des données. Nous avons développé un programme d’ajustement pour déterminer la phase φs. Avec les données 2010, la valeur trouvée est φs ∈ [−2, 7,−0, 5] rad à 68% de confiance. Ce résultat est compatible avec la prédiction du Modèle Standard.In the B⁰s→J/ψφ channel, the phase φs is predicted to be significantly small in the Standard Model. This observable is an excellent probe for New Physics because the B⁰s-⁻B⁰s mixing takes place via a loop diagram where new particles is expected to intervene. These two reasons makes the φs parameter an excellent probe for New Physics processes. We developed a simplified selection for the 2010 data. It avoids any bias on the proper time distribution in order to reduce systematic uncertainty. In addition, we control the tagging performance for B⁰s→J/ψφ events using the similar B⁰d→J/ψK∗⁰ and B⁺→J/ψK⁺ channels. With the 2010 data, we obtain 570 signal events in 36 pb−1of integrated luminosity, a tagging power of (2.2±0.4)% and a proper time resolution of 50 fs. We investigated an alternative selection which maximizes the φs sensitivity using a proper time biasing cuts. We proposed a data-driven method to correct the proper time acceptance. We designed a fitting program to determine the φs phase. With the 2010 data, It is found to be : φs ∈ [−2.7,−0.5] rad at 68% of confidance. This result is compatible with the Standard Model prediction
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