arXiv subjects

O. Deschamps

Publications and source records attributed to O. Deschamps.

9 recordsLinked to original sources

arXiv2020

Calibration and performance of the LHCb calorimeters in Run 1 and 2 at the LHC

The calibration and performance of the LHCb Calorimeter system in Run 1 and 2 at the LHC are described. After a brief description of the sub-detectors and of their role in the trigger, the calibration methods used for each part of the system are reviewed. The changes which occurred with the increase of beam energy in Run 2 are explained. The performances of the calorimetry for $γ$ and $π^0$ are detailed. A few results from collisions recorded at $\sqrt {s}$ = 7, 8 and 13 TeV are shown.

physics.ins-det↗

arXiv2019

Design and performance of the LHCb trigger and full real-time reconstruction in Run 2 of the LHC

The LHCb collaboration has redesigned its trigger to enable the full offline detector reconstruction to be performed in real time. Together with the real-time alignment and calibration of the detector, and a software infrastructure to make persistent the high-level physics objects produced during real-time processing, this redesign enabled the widespread deployment of real-time analysis during Run 2. We describe the design of the Run 2 trigger and real-time reconstruction, and present data-driven performance measurements for a representative sample of LHCb's physics programme.

hep-ex↗

arXiv2019

Physics case for an LHCb Upgrade II - Opportunities in flavour physics, and beyond, in the HL-LHC era

The LHCb Upgrade II will fully exploit the flavour-physics opportunities of the HL-LHC, and study additional physics topics that take advantage of the forward acceptance of the LHCb spectrometer. The LHCb Upgrade I will begin operation in 2020. Consolidation will occur, and modest enhancements of the Upgrade I detector will be installed, in Long Shutdown 3 of the LHC (2025) and these are discussed here. The main Upgrade II detector will be installed in long shutdown 4 of the LHC (2030) and will build on the strengths of the current LHCb experiment and the Upgrade I. It will operate at a luminosity up to $ 2 \times 10^{34} \rm cm^{-2}s^{-1}$, ten times that of the Upgrade I detector. New detector components will improve the intrinsic performance of the experiment in certain key areas. An Expression Of Interest proposing Upgrade II was submitted in February 2017. The physics case for the Upgrade II is presented here in more depth. $CP$-violating phases will be measured with precisions unattainable at any other envisaged facility. The experiment will probe $b\to s \ell^+\ell^-$ and $b\to d \ell^+\ell^-$ transitions in both muon and electron decays in modes not accessible at Upgrade I. Minimal flavour violation will be tested with a precision measurement of the ratio of $B(B^0\toμ^+μ^-)/B(B_s^0\to μ^+μ^-)$. Probing charm $CP$ violation at the $10^{-5}$ level may result in its long sought discovery. Major advances in hadron spectroscopy will be possible, which will be powerful probes of low energy QCD. Upgrade II potentially will have the highest sensitivity of all the LHC experiments on the Higgs to charm-quark couplings. Generically, the new physics mass scale probed, for fixed couplings, will almost double compared with the pre-HL-LHC era; this extended reach for flavour physics is similar to that which would be achieved by the HE-LHC proposal for the energy frontier.

hep-ex↗

arXiv2019

Opportunities in Flavour Physics at the HL-LHC and HE-LHC

Motivated by the success of the flavour physics programme carried out over the last decade at the Large Hadron Collider (LHC), we characterize in detail the physics potential of its High-Luminosity and High-Energy upgrades in this domain of physics. We document the extraordinary breadth of the HL/HE-LHC programme enabled by a putative Upgrade II of the dedicated flavour physics experiment LHCb and the evolution of the established flavour physics role of the ATLAS and CMS general purpose experiments. We connect the dedicated flavour physics programme to studies of the top quark, Higgs boson, and direct high-$p_T$ searches for new particles and force carriers. We discuss the complementarity of their discovery potential for physics beyond the Standard Model, affirming the necessity to fully exploit the LHC's flavour physics potential throughout its upgrade eras.

hep-ph↗

arXiv2017

Isospin analysis of charmless B-meson decays

We discuss the determination of the CKM angle $α$ using the non-leptonic two-body decays $B\to ππ$, $B\to ρρ$ and $B\to ρπ$ using the latest data available. We illustrate the methods used in each case and extract the corresponding value of $α$. Combining all these elements, we obtain the following determination of $α_{\rm dir}=( 86.2^{+4.4}_{-4.0}~~ \cup~~ 178.4^{+3.9}_{-5.1})^\circ$. We assess the uncertainties associated to the breakdown of the isospin hypothesis and the choice of statistical framework in detail. We also determine the hadronic amplitudes (tree and penguin) describing the QCD dynamics involved in these decays, briefly comparing our results with theoretical expectations. For each observable of interest in the $B\to ππ$, $B\to ρρ$ and $B\to ρπ$ systems, we perform an indirect determination based on the constraints from all the other observables available and we discuss the compatibility between indirect and direct determinations. Finally, we review the impact of future improved measurements on the determination of $α$.

hep-ph↗

arXiv2015

Current status of the Standard Model CKM fit and constraints on $ΔF=2$ New Physics

This letter summarises the status of the global fit of the CKM parameters within the Standard Model performed by the CKMfitter group. Special attention is paid to the inputs for the CKM angles $α$ and $γ$ and the status of $B_s\toμμ$ and $B_d\to μμ$ decays. We illustrate the current situation for other unitarity triangles. We also discuss the constraints on generic $ΔF=2$ New Physics. All results have been obtained with the CKMfitter analysis package, featuring the frequentist statistical approach and using Rfit to handle theoretical uncertainties.

hep-ph↗

arXiv2013

The LHCb Trigger and its Performance in 2011

This paper presents the design of the LHCb trigger and its performance on data taken at the LHC in 2011. A principal goal of LHCb is to perform flavour physics measurements, and the trigger is designed to distinguish charm and beauty decays from the light quark background. Using a combination of lepton identification and measurements of the particles' transverse momenta the trigger selects particles originating from charm and beauty hadrons, which typically fly a finite distance before decaying. The trigger reduces the roughly 11\,MHz of bunch-bunch crossings that contain at least one inelastic $pp$ interaction to 3\,kHz. This reduction takes place in two stages; the first stage is implemented in hardware and the second stage is a software application that runs on a large computer farm. A data-driven method is used to evaluate the performance of the trigger on several charm and beauty decay modes.

hep-ex↗

arXiv2011

Predictions of selected flavour observables within the Standard Model

This letter gathers a selection of Standard Model predictions issued from the metrology of the CKM parameters performed by the CKMfitter group. The selection includes purely leptonic decays of neutral and charged B, D and K mesons. In the light of the expected measurements from the LHCb experiment, a special attention is given to the radiative decay modes of B mesons as well as to the B-meson mixing observables, in particular the semileptonic charge asymmetries a^d,s_SL which have been recently investigated by the D0 experiment at Tevatron. Constraints arising from rare kaon decays are addressed, in light of both current results and expected performances of future rare kaon experiments. All results have been obtained with the CKMfitter analysis package, featuring the frequentist statistical approach and using Rfit to handle theoretical uncertainties.

hep-ph↗

arXiv2010

The Two Higgs Doublet of Type II facing flavour physics data

We discuss tests of the charged Higgs sector of the Two Higgs Doublet Model (2HDM) of Type II in the light of recent flavour physics data. Particular attention is paid to recent measurement of purely leptonic decays of heavy-light mesons, which depart more or less significantly from the Standard Model (SM) predictions. We derive constraints on the parameters of the 2HDM type II from leptonic and semileptonic $ΔF=1$ decays as well as loop processes ($b \to s γ$, $B\bar{B}$ mixing or $Z\to\bar{b}b$) sensitive to charged Higgs contributions. The outcome of this work is that while 2HDM Type II can fit individual observable through fine-tuning schemes, in a combined analysis it does not perform better than the SM by favouring a decoupling solution. Assuming that 2HDM Type II is realized in Nature, constraints on its parameters ($m_{H^+}$ and $\tan β$) are derived. A limit on the charged Higgs mass $m_{H^+} > 316 \; {\rm GeV}$ at $95\%$~CL is obtained irrespective of the value of $\tan β$. This limit is dominated by the $b\rightarrow s γ$ branching ratio measurement. All results have been obtained with the \ckmfitter\ analysis package, featuring the frequentist statistical approach \rfit\ to handle theoretical uncertainties.

hep-ph↗