The Level-0 muon trigger for the LHCb experiment Aslanides, E.; Cachemiche, J.-P.; Cogan, J. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
09/2007, Letnik:
579, Številka:
3
Journal Article
Recenzirano
Odprti dostop
A very compact architecture has been developed for the first level muon trigger of the LHCb experiment that processes
40
×
10
6
proton–proton collisions per second. For each collision, it receives ...3.2
kBytes of data and it finds straight tracks within a
1.2
μ
s
latency. The trigger implementation is massively parallel, pipelined and fully synchronous with the LHC clock. It relies on 248 high density Field Programable Gate Arrays and on the massive use of multigigabit serial link transceivers embedded inside FPGAs.
The B0, B0s, B+ and Λ0b hadron production asymmetries are measured using a data sample corresponding to an integrated luminosity of 3.0 fb−1, collected by the LHCb experiment in proton-proton ...collisions at centre-of-mass energies of 7 and 8 TeV. The measurements are performed as a function of transverse momentum and rapidity of the b hadrons within the LHCb detector acceptance. The overall production asymmetries, integrated over transverse momentum and rapidity, are also determined.
The production cross-section of J/ψ pairs is measured using a data sample of pp collisions collected by the LHCb experiment at a centre-of-mass energy of s√=13TeV, corresponding to an integrated ...luminosity of 279±11pb−1. The measurement is performed for J/ψ mesons with a transverse momentum of less than 10GeV/c in the rapidity range 2.0<y<4.5. The production cross-section is measured to be 13.5±0.9±0.8nb. The first uncertainty is statistical, and the second is systematic. The differential cross-sections as functions of several kinematic variables of the J/ψ pair are measured and compared to theoretical predictions.
A search for the rare decays B0s→τ+τ− and B0→τ+τ− is performed using proton--proton collision data collected with the LHCb detector. The data sample corresponds to an integrated luminosity of 3fb−1 ...collected in 2011 and 2012. The τ leptons are reconstructed through the decay τ−→π−π+π−ντ. Assuming no contribution from B0→τ+τ− decays, an upper limit is set on the branching fraction B(B0s→τ+τ−)<6.8×10−3 at 95\% confidence level. If instead no contribution from B0s→τ+τ− decays is assumed, the limit is B(B0→τ+τ−)<2.1×10−3 at 95\% confidence level. These results correspond to the first direct limit on B(B0s→τ+τ−) and the world's best limit on B(B0→τ+τ−).
Search for the B0s→η′φ decay Aaij, R.; Beaucourt, L.; Chefdeville, M. ...
The journal of high energy physics,
05/2017, Letnik:
5
Journal Article
Recenzirano
A search for the charmless B0s→η′ϕ decay is performed using pp collision data collected by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of ...3 fb−1. No signal is observed and upper limits on the B0s→η′ϕ branching fraction are set to 0.82×10−6 at 90% and 1.01×10−6 at 95% confidence level.
An amplitude analysis of the decay Λ0b→D0pπ− is performed in the part of the phase space containing resonances in the D0p channel. The study is based on a data sample corresponding to an integrated ...luminosity of 3.0 fb−1 of pp collisions recorded by the LHCb experiment. The spectrum of excited Λ+c states that decay into D0p is studied. The masses, widths and quantum numbers of the Λc(2880)+ and Λc(2940)+ resonances are measured. The constraints on the spin and parity for the Λc(2940)+ state are obtained for the first time. A near-threshold enhancement in the D0p amplitude is investigated and found to be consistent with a new resonance, denoted the Λc(2860)+, of spin 3/2 and positive parity.
The suppressed decay Λ0b→pπ−μ+μ−, excluding the J/ψ and ψ(2S)→μ+μ− resonances, is observed for the first time with a significance of 5.5 standard deviations. The analysis is performed with ...proton-proton collision data corresponding to an integrated luminosity of 3fb−1 collected with the LHCb experiment. The Λ0b→pπ−μ+μ− branching fraction is measured relative to the Λ0b→J/ψ(→μ+μ−)pπ− branching fraction givingB(Λ0b→pπ−μ+μ−)B(Λ0b→J/ψ(→μ+μ−)pπ−)=0.044±0.012±0.007,where the first uncertainty is statistical and the second is systematic. This is the first observation of a b→d transition in a baryonic decay.
The first observation of the decays Λb0→χc 1p K- and Λb0→χc 2p K- is reported using a data sample corresponding to an integrated luminosity of 3.0 fb-1, collected by the LHCb experiment in p p ...collisions at center-of-mass energies of 7 and 8 TeV. The following ratios of branching fractions are measured: B/(Λb0→χc 1p K-) B (Λb0→J /ψ p K-) =0.242 ±0.014 ±0.013 ±0.009 ,B/(Λb0→χc 2p K-) B (Λb0→J /ψ p K-) =0.248 ±0.020 ±0.014 ±0.009 ,B/(Λb0→χc 2p K-) B (Λb0→χc 1p K-) =1.02 ±0.10 ±0.02 ±0.05 , where the first uncertainty is statistical, the second systematic, and the third due to the uncertainty on the branching fractions of the χc 1→J /ψ γ and χc 2→J /ψ γ decays. Using both decay modes, the mass of the Λb0 baryon is also measured to be mΛb0=5619.44 ±0.28 ±0.26 MeV /c2 , where the first and second uncertainties are statistical and systematic, respectively.
A search for the rare decays Bs0→μ+μ- and B0→μ+μ- is performed at the LHCb experiment using data collected in p p collisions corresponding to a total integrated luminosity of 4.4 fb-1. An excess of ...Bs0→μ+μ- decays is observed with a significance of 7.8 standard deviations, representing the first observation of this decay in a single experiment. The branching fraction is measured to be B (Bs0→μ+μ- )=(3.0 ±0. 6-0.2+0.3) ×10-9 , where the first uncertainty is statistical and the second systematic. The first measurement of the Bs0→μ+μ- effective lifetime, τ (Bs0→μ+μ- )=2.04 ±0.44 ±0.05 ps , is reported. No significant excess of B0→μ+μ- decays is found, and a 95% confidence level upper limit, B (B0 →μ+μ-) <3.4 ×10-10 , is determined. All results are in agreement with the standard model expectations.
The Ξc+K- mass spectrum is studied with a sample of p p collision data corresponding to an integrated luminosity of 3.3 fb-1, collected by the LHCb experiment. The Ξc+ is reconstructed in the decay ...mode p K-π+. Five new, narrow excited Ωc0 states are observed: the Ωc(3000 )0, Ωc(3050 )0, Ωc(3066 )0, Ωc(3090 )0, and Ωc(3119 )0. Measurements of their masses and widths are reported.
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