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Register a new userOpposite-side flavour tagging of B mesons at the LHCb experiment
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The calibration and performance of the opposite-side flavour tagging algorithms used for the measurements of time-dependent asymmetries at the LHCb experiment are described. The algorithms have been developed using simulated events and optimized and calibrated with B+ -> J/psi K+, B0 -> J/psi K*0 and B0 -> D*- mu+ nu_mu decay modes with 0.37 fb^-1 of data collected in pp collisions at sqrt(s) = 7 TeV during the 2011 physics run. The opposite-side tagging power is determined in the B+ -> J/psi K+ channel to be (2.10 +- 0.08 +- 0.24) %, where the first uncertainty is statistical and the second is systematic.
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An algorithm is described for tagging the flavour content at production of neutral $B$ mesons in the LHCb experiment. The algorithm exploits the correlation of the flavour of a $B$ meson with the charge of a reconstructed secondary charm hadron from the decay of the other $b$ hadron produced in the proton-proton collision. Charm hadron candidates are identified in a number of fully or partially reconstructed Cabibbo-favoured decay modes. The algorithm is calibrated on the self-tagged decay modes $B^+ to J/psi , K^+$ and $B^0 to J/psi , K^{*0}$ using $3.0mathrm{,fb}^{-1}$ of data collected by the LHCb experiment at $pp$ centre-of-mass energies of $7mathrm{,TeV}$ and $8mathrm{,TeV}$. Its tagging power on these samples of $B to J/psi , X$ decays is $(0.30 pm 0.01 pm 0.01) %$.
The direct searches for Beyond Standard Model (BSM) particles have been constraining their mass scale to the extent where it is now becoming consensual that such particles are likely to be above the energy reach of the LHC. Meanwhile, the studies of indirect probes of BSM physics, with all their diversity, have been progressing both in accurracy and in setting up observables with reduced theoretical uncertainties. The observation of flavour anomalies in $b$ hadron decays represents an important part of the program of indirect detection of BSM physics. Several benchmark analyses involving leptonic or semileptonic decays are presented, with an emphasis on intriguing patterns which are systematic in their trend, though not individually significant yet.
A new algorithm for the determination of the initial flavour of $B_s^0$ mesons is presented. The algorithm is based on two neural networks and exploits the $b$ hadron production mechanism at a hadron collider. The first network is trained to select charged kaons produced in association with the $B_s^0$ meson. The second network combines the kaon charges to assign the $B_s^0$ flavour and estimates the probability of a wrong assignment. The algorithm is calibrated using data corresponding to an integrated luminosity of 3 fb$^{-1}$ collected by the LHCb experiment in proton-proton collisions at 7 and 8 TeV centre-of-mass energies. The calibration is performed in two ways: by resolving the $B_s^0$-$bar{B}_s^0$ flavour oscillations in $B_s^0 to D_s^- pi^+$ decays, and by analysing flavour-specific $B_{s 2}^{*}(5840)^0 to B^+ K^-$ decays. The tagging power measured in $B_s^0 to D_s^- pi^+$ decays is found to be $(1.80 pm 0.19({rm stat}) pm 0.18({rm syst}))$%, which is an improvement of about 50% compared to a similar algorithm previously used in the LHCb experiment.
These proceedings present the current status of measurements of the CP-violating phase $phi_s$ by the LHCb collaboration, reviewing the measurements in channels such as $B_s^0to J/psiphi$, $B_s^0to J/psi pi^+pi^-$ and $B_s^0 to psi(2S)phi$. The observation of the $B_s^0toeta_cphi$ decay mode is presented for the first time, which can be used to measure $phi_s$ with larger data samples that will be collected over the coming years by the LHCb experiment. Finally, the expected increase in precision from LHCb measurements of $phi_s$ over the next decade is presented.
The LHCb experiment is designed to study the decays and properties of heavy flavoured hadrons produced in the forward region from proton-proton collisions at the CERN Large Hadron Collider. During Run 1, it has recorded the worlds largest data sample of beauty and charm hadrons, enabling precise studies into the spectroscopy of such particles, including discoveries of new states and measurements of their masses, widths and quantum numbers. An overview of recent LHCb results in the area of exotic hadron spectroscopy is presented, focussing on the discovery of the first pentaquark states in the $Lambda_b^0 to J/psi p K^-$ channel and a search for them in the related $Lambda_b^0 to J/psi ppi^-$ mode. The LHCb non-confirmation of the D0 tetraquark candidate in the $B_s^0pi^+$ invariant mass spectrum is presented.
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