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.
The first model-independent measurement of the charm mixing parameters in the decay $D^0 \to K_S \pi^+ \pi^-$ is reported, using a sample of $pp$ collision data recorded by the LHCb experiment, ...corresponding to an integrated luminosity of 1.0 fb$^{-1}$ at a centre-of-mass energy of 7 TeV. The measured values are \begin{eqnarray*} x &=& (+0.86 \pm 0.53 \pm 0.17) \times 10^{-2}, \\ y &=& (+0.03 \pm 0.46 \pm 0.13) \times 10^{-2}, \end{eqnarray*} where the first uncertainties are statistical and include small contributions due to the external input for the strong phase measured by the CLEO collaboration, and the second uncertainties are systematic. The results are consistent with the current world averages.
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.
Observation of the decay Bs0→D¯0ϕ Amhis, Y.; Barter, W.; Bedeschi, F. ...
Physics letters. B,
12/2013, Letnik:
727, Številka:
4-5
Journal Article
Recenzirano
Odprti dostop
First observation of the decay Bs0→D¯0ϕ is reported using pp collision data, corresponding to an integrated luminosity of 1.0 fb−1, collected by the LHCb experiment at a centre-of-mass energy of ...7 TeV. The significance of the signal is 6.5 standard deviations. The branching fraction is measured relative to that of the decay Bs0→D¯0K¯⁎0 to beB(Bs0→D¯0ϕ)B(Bs0→D¯0K¯⁎0)=0.069±0.013 (stat)±0.007 (syst). The first measurement of the ratio of branching fractions for the decays Bs0→D¯0K¯⁎0 and B0→D¯0K⁎0 is found to beB(Bs0→D¯0K¯⁎0)B(B0→D¯0K⁎0)=7.8±0.7 (stat)±0.3 (syst)±0.6 (fs/fd), where the last uncertainty is due to the ratio of the Bs0 and B0 fragmentation fractions.
A
bstract
The cross-section for inelastic proton-proton collisions, with at least one prompt long-lived charged particle of transverse momentum
p
T
>
0
.
2GeV
/c
in the pseudorapidity range 2
.
0
< η ...<
4
.
5, is measured by the LHCb experiment at a centre-of-mass energy of
s
= 7 TeV. The cross-section in this kinematic range is determined to be
σ
inel
acc
= 55
.
0 ± 2
.
4 mb with an experimental uncertainty that is dominated by systematic contributions. Extrapolation to the full phase space, using P
ythia
6, yields
σ
inel
= 66
.
9 ± 2
.
9 ± 4
.
4 mb, where the first uncertainty is experimental and the second is due to the extrapolation.
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.
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