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High Precision Flavour Physics at LHCb

English title High Precision Flavour Physics at LHCb
Applicant Schneider Olivier
Number 185050
Funding scheme Project funding (Div. I-III)
Research institution Laboratoire de physique des hautes énergies 2 EPFL - SB - IPEP - LPHE2
Institution of higher education EPF Lausanne - EPFL
Main discipline Particle Physics
Start/End 01.04.2019 - 31.03.2023
Approved amount 1'944'740.00
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Keywords (14)

B physics; CP violation; lepton flavour violation (LFV); Standard Model; tracker upgrade; LHCb; scintillating fibres; LHC; B and D mesons; heavy flavour; SiPM; CKM matrix; New Physics; b and c quark

Lay Summary (French)

Lead
Le grand collisionneur de protons (LHC) du laboratoire européen pour la physique des particules (CERN, Genève) a été construit pour explorer, au niveau le plus fondamental possible, les constituants élémentaires de la matière et leurs interactions. L'expérience LHCb porte un nom suggestif; en effet, son but principal est de tirer parti de l'énorme quantité de quark lourds appelés "b" produite au LHC dans les collisions entre protons de très haute énergie (correspondant à l'énergie acquise dans une différence de potentiel électrique de plusieurs fois mille milliards de volts). L'étude de certaines désintégrations rares des particules contenant un quark lourd permet de tester les prédictions du "Modèle Standard", la théorie minimale décrivant tous les processus connus en physique des particules élémentaires. Si l'expérience révélait que certaines prédictions sont incorrectes, alors elle révélerait du même coup l'existence de nouveaux phénomènes encore inconnus.
Lay summary
L'expérience LHCb a été construite par une collaboration internationale de plusieurs centaines de physiciens, y compris les membres du Laboratoire de Physique des Hautes Energies de l'EPFL qui ont pris des responsabilités importantes dans l'élaboration et la mise sur pied du projet dès son origine. Ils ont en particulier développé et construit une partie de l'appareillage de l'expérience, incluant des détecteurs à micro-pistes de silicium et l'électronique de lecture des signaux. LHCb a enregistré efficacement des données d'excellente qualité durant les deux premières périodes d'exploitation du LHC, entre fin 2009 et début 2013, à la moitié de l'énergie nominale, et entre mi-2015 et fin 2018, proche de l'énergie nominale. L'analyse d'une partie de cette énorme masse de données, à laquelle le groupe de l'EPFL prend une part active, a produit de nombreuses nouvelles observations et mesures, publiées dans plus de 470 articles scientifiques, mais n'a pas (encore) permis de trouver la faille du Modèle Standard. Des exemples d'analyses faites à l'EPFL sont l'étude de la violation de la symétrie entre matière et anti-matière dans la désintégration de particules contenant un quark lourd, ainsi que de la polarisation du photon émis dans la désintégration d'un quark "b" en un quark "s". En 2019-2020, l'expérience est mise à jour afin d'en décupler le potentiel. Pour ceci, le groupe de l'EPFL a développé de nouveaux "détecteurs à traces" en fibres scintillantes lues par des photo-détecteurs au silicium. Ce subside permet de financer des doctorants et des postdocs pour analyser les données déjà enregistrées, publier les résultats, installer les nouveaux éléments de détection nécessaires à la mise à jour, et remettre en service l'expérience pour une nouvelle et passionnante campagne de prise de données en 2021-2023. Ces activités pourront avoir un grand impact sur notre compréhension de la Nature, en propulsant l'expérience LHCb à un nouveau niveau de sensibilité pour la recherche de phénomènes physiques au-delà du Modèle Standard, avec une approche originale et très différente des autres expériences du LHC.
Direct link to Lay Summary Last update: 30.03.2019

Lay Summary (English)

Lead
The Large Hadron Collider (LHC) at the European Organization for Nuclear Research (CERN, Geneva) was built to explore, at the most fundamental possible level, the elementary constituents of matter and their interactions. The LHCb experiment has a suggestive name: indeed, its main goal is to exploit the huge number of heavy quarks called “b” produced at the LHC through the collisions between protons of very high energy (corresponding to the energy acquired in an electric potential difference of several thousands of billions of volts). The study of certain rare decays of the particles containing a heavy quark allows tests of predictions from the “Standard Model”, the minimal theory describing all known processes in elementary particle physics. If the experiment revealed that certain predictions are incorrect, it would then at the same time reveal the existence of new yet unknown phenomena.
Lay summary
The LHCb experiment was built by an international collaboration of several hundreds of physicists, including the members of EPFL’s High Energy Physics Laboratory who have taken important responsibilities for the design and realization of the project since its inception. They have in particular developed and built certain scientific equipment of the experiment, including silicon-strip detectors and electronics for the readout of the signals. LHCb has efficiently recorded data of excellent quality during the first two periods of LHC operation, between end 2009 and beginning 2013, at half of the design energy, and between mid-2015 and end 2018, close to the design energy. The analysis of part of this huge dataset, to which the EPFL group is contributing actively, has already resulted in a large number of new observations and measurements, published in more than 470 scientific articles, but has not (yet) unveiled any flaw of the Standard Model. Examples of analyses performed at EPFL are the study of the violation of the symmetry between matter and anti-matter in the decay of particles containing a heavy quark, as well as the investigation of the polarisation of the photon emitted in the decay of a “b” quark into an “s” quark. In 2019-2020,  the experiment undergoes an upgrade in order to multiply its potential. Towards this goal the EPFL group has developed and built new tracking detectors made of scintillating fibres read out with silicon photo-multipliers. This grant provides funding for PhD students and postdocs to analyse the already collected data, publish the results, install new detector elements needed for the upgrade, and re-commission the experiment for a new exciting data period in 2021-2023. These activities may have a large impact on the field, by propelling the LHCb experiment to a new level of sensitivity in the search for physics beyond the Standard Model, with an original approach very different from that of the other LHC experiments.
Direct link to Lay Summary Last update: 30.03.2019

Responsible applicant and co-applicants

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Associated projects

Number Title Start Funding scheme
173598 FLARE: Maintenance & Operation for the LHC Experiments 2017-2020 01.04.2017 FLARE
173580 FLARE 2017-2020: Operation and upgrade of the LHCb experiment 01.04.2017 FLARE
173600 FLARE - GRID Infrastructure for LHC Experiments 01.04.2017 FLARE
201480 FLARE 2021-2022: Operation and upgrade of the LHCb experiment 01.04.2021 FLARE
173104 What's behind Flavour Anomalies? 01.07.2017 SNSF Professorships
166208 High Precision CP Violation Physics at LHCb 01.04.2016 Project funding (Div. I-III)
178969 LHCb experiment at CERN: Detector Upgrades and Analyses with Electroweak Bosons 01.06.2018 Project funding (Div. I-III)
155990 Search for hidden particles: exploring the high intensity frontier 01.01.2016 SNSF Starting Grants

Abstract

The LHCb experiment has been designed to exploit the abundant heavy-quark production at CERN's Large Hadron Collider (LHC) for precise measurements of CP violation and rare B decays. The primary physics aims are to characterize in detail the flavour structure in the quark sector, and look for New Physics in the decay of charm and bottom hadrons.During the first two LHC running periods, LHCb has efficiently recorded 3/fb of pp collisions at centre-of-mass energies up to 8 TeV (Run 1, from November 2009 to February 2013) and an additional integrated luminosity of nearly 6/fb at 13 TeV (Run 2, from June 2015 to November 2018). With these data the LHCb physics programme has been fully deployed: much new territory has been explored resulting in already 472 physics papers published or submitted to peer-reviewed journals, mostly from the Run 1 period. Although some intriguing (but not very significant) deviations have been seen, all results are so far consistent with the expectations of the Standard Model of particle physics. In order to reach the next level in precision, the collaboration is busily preparing a major upgrade of the experiment to enable the collection of 5/fb per year (from 2021 onwards) with improved efficiency. In parallel, the collaboration has expressed its interest to plan for further upgrades, in order to exploit fully the flavour physics opportunities offered throughout the high-luminosity phase of the LHC.Our particle physics group in Lausanne has played important roles in LHCb since the beginning of the project in 1995. We have developed and built the common readout electronics of the experiment, the powering system and analogue transmission electronics for the silicon vertex detector, and the downstream tracking stations (Inner Tracker) of the Silicon Tracker. In addition Switzerland has significantly invested in the upstream tracking stations (through University of Zurich) and in the online system, including the computer farm for the high-level trigger. We are heavily involved in data analysis and, after several years of detector R&D, in the construction of a new downstream tracker, for which we have proposed a novel technology based on scintillating fibres read out with silicon photomultipliers.Our objectives for the four-year funding period 2019-2023 are the following:- Analyze the available LHCb data, most importantly the full Run 2 data, with main emphasis on searches for New Physics effects, mostly through searches of lepton-flavour-violating decays and investigations of CP violating effects in charm decays.- Assemble, test, install and commission the new scintillating-fibre tracker (2019-2020), then maintain and calibrate it to ensure that it is fully functional and performant throughout Run 3 (2021-2023).- Engage in new detector R&D on fibre tracking for possible applications in further upgrades of LHCb or elsewhere.These activities, combining physics analyses and detector work, may have a large impact on the field: not only will they maintain LHCb at the fore-front of flavour physics, but propel it to a new level of sensitivity in the search for physics beyond the Standard Model mostly orthogonal to that of the other LHC experiments.
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