Measurement of the CP violating phase Φₛ using B⁰ₛ → J/ψK⁺ K⁻ decays at the LHCb experiment

The LHCb experiment at the Large Hadron Collider (LHC) at CERN is designed to search for indirect evidence of physics beyond the Standard Model (SM) in CP violation and rare decays of beauty and charm hadrons. One of the key measurements is the CP violating phase Φₛ, that arises from the interference between the decay of B⁰ₛ mesons into CP eigenstates directly and via B⁰ₛ- ̅B̅⁰ₛ mixing In this thesis, the phase Φₛ is measured in the B⁰ₛ → J/ψK⁺ K⁻ decay channel using 1.9 fb−¹ of proton-proton collisions collected at a centre-of-mass energy of √s = 13 TeV. Other parameters that are measured are the average decay width of the B⁰ₛ meson with respect to that of the B⁰d meson, Γₛ − Γd, the difference in decay widths of the heavy and light mass eigenstates of the B⁰ₛ- ̅B̅⁰ₛ system, ∆Γₛ, and a further parameter that describes the CP violation in interference between mixing and decay, |λ| .The following results are obtained: Φₛ = -0:080 ± 0:041 ± 0:006 rad Γₛ − Γd = 0.0041 ± 0:0024 ± 0:0015 ps⁻¹ ∆Γₛ = 0:0764 ± 0:0077 ± 0:0026 ps⁻¹ |λ| = 1:014 ± 0:016 ± 0:006 These are the most precise measurements using a single decay channel. Combining this analysis with other decay channels measured at the LHCb experiment that are sensitive to Φₛ yields the most precise measurements to date: Φₛ = -0.042 ± 0.025 rad Γₛ = 0.6566 ± 0.025 ps⁻¹ ∆Γₛ = 0:0811 ± 0.0048 ps⁻¹ |λ| = 0:993 ± 0:01

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 2×1034 cm−2s−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 → sl+l−and b → dl+l− 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(B0 → μ+μ−)/B(Bs → 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

LHCb upgrade software and computing : technical design report

This document reports the Research and Development activities that are carried out in the software and computing domains in view of the upgrade of the LHCb experiment. The implementation of a full software trigger implies major changes in the core software framework, in the event data model, and in the reconstruction algorithms. The increase of the data volumes for both real and simulated datasets requires a corresponding scaling of the distributed computing infrastructure. An implementation plan in both domains is presented, together with a risk assessment analysis

Search for CP violation in Bs0B^0_s mixing at LHCb

One of the main goals of the LHCb experiment is to determine the mixing-induced $CP$ violating phase $\phi_s$ in $b \rightarrow c\bar{c}s$ transitions. Assuming the Standard Model, $\phi_s$ is precisely predicted, hence new physics could easily affect the measurement. The most precise single measurement using $B^0_s \rightarrow J/\psi K^+K^-$ data collected in 2015 and 2016 is presented along with a total combined value including all LHCb $\phi_s^{c\bar{c}s}$ analyses. The result is further combined with Tevatron and other LHC experimental results.Comment: Contribution to the 2019 EW session of the 54th Rencontres de Morion

Measurement of the CPCP violating phase ϕs\phi_{s} using Bs0→J/ψK+K−B^{0}_{s} \rightarrow J/\psi K^{+}K^{-} decays at the LHCb Experiment

The LHCb experiment at the Large Hadron Collider (LHC) at CERN is designed to search for indirect evidence of physics beyond the Standard Model in $CP$ violation and rare decays of beauty and charm hadrons. One of the key measurements is the $CP$ violating phase $\phi_s$, that arises from the interference between the decay of $B^0_s$ mesons into $CP$ eigenstates directly and via $B^0_s - \bar{B^0_s}$ mixing. In this thesis, the phase $\phi_s$ is measured in the $B^{0}_{s} \rightarrow J/ \psi K^{+}K^{-}$ decay channel using 1.9 fb$^{-1}$ of proton-proton collisions collected by the LHCb experiment in the years 2015 and 2016 at a centre-of-mass energy of $\sqrt{s} = 13$ TeV. The following results is obtained: $\phi_s = -0.080 \pm 0.041 \pm 0.006$ rad. This is the most precise measurements using a single decay channel. Combining this analysis with other decay channels measured at the LHCb experiment that are sensitive to $\phi_s$ yields the most precise measurements to date: $\phi_s = -0.042 \pm 0.025$ rad

Measurement of CP violating phase φs\varphi_s in Bs0→J/ψh+h−B^0_s \rightarrow J/\psi h^+h^- Decays at LHCb

The measurement of the CP violating phase $\phi_s$ is one of the key goals of the LHCb experiment. A time-dependent amplitude analysis of $B^-0_s \rightarrow J/\psi h^+ h^-$ decays allows the determination of this theoretically precisely predicted phase. New Physics could significantly affect the measured $\phi_s$ value, making it experimentally very interesting. This poster shows the Run 1 analyses results, and a prospect of the precision that can be expected when analysing data from 2015 and 2016, leading to the the World's most precise determination of $\phi_s$

Search for long-lived particles decaying to e±μ∓νe^\pm \mu^\mp \nu

International audienceLong-lived particles decaying to ${e ^\pm } {\mu ^\mp } {\nu }$, with masses between 7 and $50 \,\text {GeV/}c^2$ and lifetimes between 2 and $50 \,\text {ps}$, are searched for by looking at displaced vertices containing electrons and muons of opposite charges. The search is performed using $5.4 \,\text {fb} ^{-1}$ of $p p$ collisions collected with the LHCb detector at a centre-of-mass energy of $\sqrt{s} = 13 \,\text {TeV}$. Three mechanisms of production of long-lived particles are considered: the direct pair production from quark interactions, the pair production from the decay of a Standard-Model-like Higgs boson with a mass of $125 \,\text {GeV/}c^2$, and the charged current production from an on-shell $W$ boson with an additional lepton. No evidence of these long-lived states is obtained and upper limits on the production cross-section times branching fraction are set on the different production modes

Observation of Multiplicity Dependent Prompt χc1(3872)\chi_{c1}(3872) and ψ(2S)\psi(2S) Production in pppp Collisions

The production of $χ_{c1}$(3872) and $ψ$(2S) hadrons is studied as a function of charged particle multiplicity in pp collisions at a center-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 2 fb-1. For both states, the fraction that is produced promptly at the collision vertex is found to decrease as charged particle multiplicity increases. The ratio of $χ_{c1}$(3872) to $ψ$(2S) cross sections for promptly produced particles is also found to decrease with multiplicity, while no significant dependence on multiplicity is observed for the equivalent ratio of particles produced away from the collision vertex in b-hadron decays. This behavior is consistent with a calculation that models the $χ_{c1}$(3872) structure as a compact tetraquark. Comparisons with model calculations and implications for the binding energy of the $χ_{c1}$(3872) state are discussed

First observation of the decay Λb0→ηc(1S)pK−\Lambda_b^0 \to \eta_c(1S) p K^-

International audienceThe decay Λb0→ηc(1S)pK- is observed for the first time using a data sample of proton-proton collisions, corresponding to an integrated luminosity of 5.5  fb-1, collected with the LHCb experiment at a center-of-mass energy of 13 TeV. The branching fraction of the decay is measured, using the Λb0→J/ψpK- decay as a normalization mode, to be B(Λb0→ηc(1S)pK-)=(1.06±0.16±0.06-0.19+0.22)×10-4, where the quoted uncertainties are statistical, systematic and due to external inputs, respectively. A study of the ηc(1S)p mass spectrum is performed to search for the Pc(4312)+ pentaquark state. No evidence is observed and an upper limit of B(Λb0→Pc(4312)+K-)×B(Pc(4312)+→ηc(1S)p)B(Λb0→ηc(1S)pK-)<0.24 is obtained at the 95% confidence level

Measurement of χc1_{c1}(3872) production in proton-proton collisions at s \sqrt{s} = 8 and 13 TeV

International audienceThe production cross-section of the χ$_{c1}$(3872) state relative to the ψ(2S) meson is measured using proton-proton collision data collected with the LHCb experiment at centre-of-mass energies of $\sqrt{s}$ = 8 and 13 TeV, corresponding to integrated luminosities of 2.0 and 5.4 fb$^{−1}$, respectively. The two mesons are reconstructed in the J/ψπ$^{+}$π$^{−}$ final state. The ratios of the prompt and nonprompt χ$_{c1}$(3872) to ψ(2S) production cross-sections are measured as a function of transverse momentum, p$_{T}$, and rapidity, y, of the χ$_{c1}$(3872) and ψ(2S) states, in the kinematic range 4 < p$_{T}$< 20 GeV/c and 2.0 < y < 4.5. The prompt ratio is found to increase with p$_{T}$, independently of y. For the prompt component, the double ratio of the χ$_{c1}$(3872) and ψ(2S) production cross-sections between 13 and 8 TeV is observed to be consistent with unity, independent of p$_{T}$ and centre-of-mass energy.[graphic not available: see fulltext