Abstract
The LHCb Experiment is commissioning its first upgrade to cope with increased luminosity of LHC Run3, being able to improve on many world-best physics measurements. A new scintillating ...fiber-based tracker (SciFi) replaced the outer and inner trackers, providing improved spatial resolution and granularity for the new LHCb trigger-less era, with a readout capable of reading zero suppressed data from ~524k channels at 40 MHz. The fully automated calibration of SciFi Front-End Electronics is based on dedicated software tools and operational procedures, validated during SciFi commissioning. This paper describes the design, implementation, and calibration of SciFi electronics and presents results showing the detector performance after commissioning.
A search for direct CP violation in the Cabibbo-suppressed decay D-s(+) -> K-K+ K+ and in the doubly Cabibbo-suppressed decay D+ -> K- K+ K+ is reported. The analysis is performed with data ...collected by the LHCb experiment in proton-proton collisions at a centre-of-mass energy of 13TeV corresponding to an integrated luminosity of 5.6 fb(-1). The search is conducted by comparing the D-(s)(+) and D-(s)(-) Dalitz-plot distributions through a model-independent binned technique, based on fits to the K-K+K+ invariantmass distributions, with a total of 0.97 (1.27) million D-s(+) (D+) signal candidates. The results are given as p-values for the hypothesis of CP conservation and are found to be 13.3% for the D+ -> K-K+ K+ decay and 31.6% for the D+ -> K-K+ K+ decay. No evidence for CP violation is observed in these decays.
The branching fraction B ( B0 → D*-τ+ντ ) is measured relative to that of the normalization mode B0 → D*-π+π-π+ using hadronic τ+ → π+π-π+ ( π0 ) ν ¯ τ decays in proton-proton collision data at a ...center-of-mass energy of 13 TeV collected by the LHCb experiment, corresponding to an integrated luminosity of 2 fb-1 . The measured ratio is B ( B0 → D*-τ+ντ ) / B ( B0 → D*-π+π-π+ ) =1.70±0.10-0.10+0.11 , where the first uncertainty is statistical and the second is related to systematic effects. Using established branching fractions for the B0 → D*-π+π-π+ and B0 → D*-μ+νμ modes, the lepton universality test R ( D*- ) ≡ B ( B0 → D*-τ+ντ ) / B ( B0 → D*-μ+νμ ) is calculated, R ( D*- ) =0.247±0.015±0.015±0.012 , where the third uncertainty is due to the uncertainties on the external branching fractions. This result is consistent with the Standard Model prediction and with previous measurements.
A simultaneous analysis of the B thorn & RARR; K thorn e thorn e- and B0 & RARR; K & DBLBOND;0e thorn e- decays is performed to test muonelectron universality in two ranges of the square ...of the dilepton invariant mass, q2. The measurement uses a sample of beauty meson decays produced in proton-proton collisions collected with the LHCb detector between 2011 and 2018, corresponding to an integrated luminosity of 9 fb-1. A sequence of multivariate selections and strict particle identification requirements produce a higher signal purity and a better statistical sensitivity per unit luminosity than previous LHCb lepton universality tests using the same decay modes. Residual backgrounds due to misidentified hadronic decays are studied using data and included in the fit model. Each of the four lepton universality measurements reported is either the first in the given q2 interval or supersedes previous LHCb measurements. The results are compatible with the predictions of the Standard Model.
An amplitude analysis of B- -> J/psi Lambda(p) over bar decays is performed using 4400 signal candidates selected on a data sample of pp collisions recorded at center-of-mass energies of 7, 8, and ...13 TeV with the LHCb detector, corresponding to an integrated luminosity of 9 fb(-1). A narrow resonance in the J/psi Lambda system, consistent with a pentaquark candidate with strangeness, is observed with high significance. The mass and the width of this new state are measured to be 4338.2 +/- 0.7 +/- 0.4 MeV and 7.0 +/- 1.2 +/- 1.3 MeV, where the first uncertainty is statistical and the second systematic. The spin is determined to be 1/2 and negative parity is preferred. Because of the small Q-value of the reaction, the most precise single measurement of the B- mass to date, 5279.44 +/- 0.05 +/- 0.07 MeV, is obtained.
