1,722,501 research outputs found
Antihelium production in decays
No full textDecays of baryons produced in dark matter annihilating into pairs could enhance the abundance of antihelium in cosmic rays. The LHCb collaboration provides in this paper the first experimental limits on related branching fractions: \begin{align*} \mathcal B({\overline{\it \Lambda}_b^0\to{}^3{\rm\overline He}p p})&<1.9\times10^{-9}\text{ at 90% CL,}\\ \mathcal B({\overline{\it \Lambda}_b^0\to{}^3{\rm\overline He}pp X})&<1.6\times10^{-8}\text{ at 90% CL,}\\ \mathcal B({\overline{\it \Lambda}_b^0\to{}^3{\rm \overline He}pX})&<3.6\times10^{-8}\text{ at 90% CL,} \end{align*} where denotes one or several particles. The limit is extrapolated to the fully inclusive branching fraction . The obtained result significantly restricts the aforementioned scenario for antihelium production
The LHCb collaboration week group photo
No full textMembers of the LHCb collaboration attending the LHCb week gathered on the lawn next to CERN Restaurant 1
Design and performance of the LHCb trigger and full real-time reconstruction in Run 2 of the LHC
No full text© 2019 CERN for the benefit of the LHCb collaboration.. 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
Observation of the suppressed ADS modes B ± → [ π ± K ∓ π + π − ] D K ± and B ± → [ π ± K ∓ π + π − ] D π ±
No full textAn analysis of B± → DK± and B± → Dπ± decays is presented where the D meson is reconstructed in the four-body nal state K±π∓π+π-. Using LHCb data corresponding to an integrated luminosity of 1.0 fb-1, rst observations are made of the suppressed ADS modes B± →[π±K∓π+π-] D K± and B± → [π±K∓π+π-]Dπ± with a signicance of 5.1σ and greater than 10σ, respectively. Measurements of CP asymmetries and CP-conserving ratios of partial widths from this family of decays are also performed. The magnitude of the ratio between the suppressed and favoured B± → DK± amplitudes is determined to be rKB = 0.097±0.011. © CERN for the benet of the LHCb Collaboration
Patrick Koppenburg of the LHCb collaboration
No full textPortrait of Patrick Koppenburg of the LHCb collaboration to be published with an interview in the Dutch Nikhef magazine, which is the National Institute for Subatomic Physics in Holland
Observation of a Narrow Pentaquark State, P c ( 4312 ) + , and of the Two-Peak Structure of the P c ( 4450 ) +
No full text© 2019 CERN. for the LHCb Collaboration. Published by the American Physical Society under the terms of the »https://creativecommons.org/licenses/by/4.0/» Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP 3 . A narrow pentaquark state, Pc(4312)+, decaying to J/ψp, is discovered with a statistical significance of 7.3σ in a data sample of Λb0→J/ψpK- decays, which is an order of magnitude larger than that previously analyzed by the LHCb Collaboration. The Pc(4450)+ pentaquark structure formerly reported by LHCb is confirmed and observed to consist of two narrow overlapping peaks, Pc(4440)+ and Pc(4457)+, where the statistical significance of this two-peak interpretation is 5.4σ. The proximity of the ςc+D̄0 and ςc+D̄∗0 thresholds to the observed narrow peaks suggests that they play an important role in the dynamics of these states
Erratum to: Measurement of the Λc+ to D<sup>0</sup> production ratio in peripheral PbPb collisions at sNN = 5.02 TeV(Journal Of High Energy Physics, (2023), 6, 10.1007/JHEP06(2023)132)
No full textWe report on a measurement of the Λ+c to D0 production ratio in peripheral PbPb collisions at √ sNN = 5.02TeV with the LHCb detector in the forward rapidity region 2 < y < 4.5. The Λ+c (D0) hadrons are reconstructed via the decay channel Λ+c → pK−π+ (D0 → K−π+) for 2 < pT < 8 GeV/c and in the centrality range of about 65–90%. The results show no significant dependence on pT, y or the mean number of participating nucleons. They are also consistent with similar measurements obtained by the LHCb collaboration in pPb and Pbp collisions at √ sNN = 5.02TeV. The data agree well with predictions from PYTHIA in pp collisions at √ s = 5TeV but are in tension with predictions of the Statistical Hadronization model.LPHE-OSSCI-SB-FBLPHE-LSARGUS
Overview of LHCb results on CP violation
No full textPrecision measurements of CP violating observables in the mixing and decay of B mesons provide excellent opportunities to search for possible contributions from New Physics beyond the Standard Model. In this contribution, key measurements pur-sued by the LHCb collaboration at CERN’s Large Hadron Collider (LHC) are described. Important results have been reported on topics including the CP violating phase φs in Bs0 → J/ψφ (and related) decays, the angle γ of the CKM unitarity triangle, and direct CP violation effects in two-and three-body B meson decays to charmless final states. Latest results on CP violation in the charm sector are also reviewed. Results obtained from the analysis of data collected in 2011 already match or even surpass the measurements of previous experiments in their precision. All results obtained so far are compatible with Standard Model predictions
Absolute luminosity measurements with the LHCb detector at the LHC
Full text linkAbsolute luminosity measurements are of general interest for colliding-beam experiments at storage rings. These measurements are necessary to determine the absolute cross-sections of reaction processes and are valuable to quantify the performance of the accelerator. Using data taken in 2010, LHCb has applied two methods to determine the absolute scale of its luminosity measurements for proton-proton collisions at the LHC with a centre-of-mass energy of 7 TeV. In addition to the classic ''van der Meer scan'' method a novel technique has been developed which makes use of direct imaging of the individual beams using beam-gas and beam-beam interactions. This beam imaging method is made possible by the high resolution of the LHCb vertex detector and the close proximity of the detector to the beams, and allows beam parameters such as positions, angles and widths to be determined. The results of the two methods have comparable precision and are in good agreement. Combining the two methods, an overal precision of 3.5% in the absolute luminosity determination is reached. The techniques used to transport the absolute luminosity calibration to the full 2010 data-taking period are presented
Search for the lepton-flavour violating decay D0→e±μ∓
No full text© 2016 CERN for the benefit of the LHCb Collaboration. A search for the lepton-flavour violating decay D0→e±μ∓is made with a dataset corresponding to an integrated luminosity of 3.0 fb-1of proton-proton collisions at centre-of-mass energies of 7TeV and 8TeV, collected by the LHCb experiment. Candidate D0mesons are selected using the decay D*+→D0π+and the D0→e±μ∓branching fraction is measured using the decay mode D0→K-π+as a normalization channel. No significant excess of D0→e±μ∓candidates over the expected background is seen, and a limit is set on the branching fraction, B(D0→e±μ∓)<1.3×10-8, at 90% confidence level. This is an order of magnitude lower than the previous limit and it further constrains the parameter space in some leptoquark models and in supersymmetric models with R-parity violation
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