2,663 research outputs found
COMPLEX CONTINUOUS NONLINEAR SYSTEMS: THEIR BLACK BOX IDENTIFICATION AND THEIR CONTROL
Study of decays to the final state and evidence for the decay
A study of decays is performed for the first time
using data corresponding to an integrated luminosity of 3.0
collected by the LHCb experiment in collisions at centre-of-mass energies
of and TeV. Evidence for the decay
is reported with a significance of 4.0 standard deviations, resulting in the
measurement of
to
be .
Here denotes a branching fraction while and
are the production cross-sections for and mesons.
An indication of weak annihilation is found for the region
, with a significance of
2.4 standard deviations.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2016-022.html,
link to supplemental material inserted in the reference
Model-independent evidence for contributions to decays
The data sample of decays acquired with the
LHCb detector from 7 and 8~TeV collisions, corresponding to an integrated
luminosity of 3 fb, is inspected for the presence of or
contributions with minimal assumptions about
contributions. It is demonstrated at more than 9 standard deviations that
decays cannot be described with
contributions alone, and that contributions play a dominant role in
this incompatibility. These model-independent results support the previously
obtained model-dependent evidence for charmonium-pentaquark
states in the same data sample.Comment: 21 pages, 12 figures (including the supplemental section added at the
end
Measurement of the lifetime
Using a data set corresponding to an integrated luminosity of ,
collected by the LHCb experiment in collisions at centre-of-mass energies
of 7 and 8 TeV, the effective lifetime in the
decay mode, , is measured to be ps. Assuming
conservation, corresponds to the lifetime of the light
mass eigenstate. This is the first measurement of the effective
lifetime in this decay mode.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2016-017.htm
Observation of an Excited Bc+ State
Using pp collision data corresponding to an integrated luminosity of 8.5 fb-1 recorded by the LHCb experiment at center-of-mass energies of s=7, 8, and 13 TeV, the observation of an excited Bc+ state in the Bc+Ď+Ď- invariant-mass spectrum is reported. The observed peak has a mass of 6841.2Âą0.6(stat)Âą0.1(syst)Âą0.8(Bc+) MeV/c2, where the last uncertainty is due to the limited knowledge of the Bc+ mass. It is consistent with expectations of the Bcâ(2S31)+ state reconstructed without the low-energy photon from the Bcâ(1S31)+âBc+Îł decay following Bcâ(2S31)+âBcâ(1S31)+Ď+Ď-. A second state is seen with a global (local) statistical significance of 2.2Ď (3.2Ď) and a mass of 6872.1Âą1.3(stat)Âą0.1(syst)Âą0.8(Bc+) MeV/c2, and is consistent with the Bc(2S10)+ state. These mass measurements are the most precise to date
Study of charmonium production in b -hadron decays and first evidence for the decay Bs0
Using decays to Ď-meson pairs, the inclusive production of charmonium states in b-hadron decays is studied with pp collision data corresponding to an integrated luminosity of 3.0 fbâ1, collected by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. Denoting byBC ⥠B(b â C X) Ă B(C â ĎĎ) the inclusive branching fraction of a b hadron to a charmonium state C that decays into a pair of Ď mesons, ratios RC1C2 ⥠BC1 /BC2 are determined as RĎc0Ρc(1S) = 0.147 Âą 0.023 Âą 0.011, RĎc1Ρc(1S) =0.073 Âą 0.016 Âą 0.006, RĎc2Ρc(1S) = 0.081 Âą 0.013 Âą 0.005,RĎc1 Ďc0 = 0.50 Âą 0.11 Âą 0.01, RĎc2 Ďc0 = 0.56 Âą 0.10 Âą 0.01and RΡc(2S)Ρc(1S) = 0.040 Âą 0.011 Âą 0.004. Here and below the first uncertainties are statistical and the second systematic.Upper limits at 90% confidence level for the inclusive production of X(3872), X(3915) and Ďc2(2P) states are obtained as RX(3872)Ďc1 < 0.34, RX(3915)Ďc0 < 0.12 andRĎc2(2P)Ďc2 < 0.16. Differential cross-sections as a function of transverse momentum are measured for the Ρc(1S) andĎc states. The branching fraction of the decay B0s â ĎĎĎ is measured for the first time, B(B0s â ĎĎĎ) = (2.15Âą0.54Âą0.28Âą0.21B)Ă10â6. Here the third uncertainty is due to the branching fraction of the decay B0s â ĎĎ, which is used for normalization. No evidence for intermediate resonances is seen. A preferentially transverse Ď polarization is observed.The measurements allow the determination of the ratio of the branching fractions for the Ρc(1S) decays to ĎĎ and p p asB(Ρc(1S)â ĎĎ)/B(Ρc(1S)â p p) = 1.79 Âą 0.14 Âą 0.32
Study of J /Ď production in Jets
The production of J/Ď mesons in jets is studied in the forward region of proton-proton collisions using data collected with the LHCb detector at a center-of-mass energy of 13 TeV. The fraction of the jet transverse momentum carried by the J/Ď meson, z(J/Ď)âĄpT(J/Ď)/pT(jet), is measured using jets with pT(jet)>20 GeV in the pseudorapidity range 2.5<Ρ(jet)<4.0. The observed z(J/Ď)distribution for J/Ď mesons produced in b-hadron decays is consistent with expectations. However, the results for prompt J/Ď production do not agree with predictions based on fixed-order nonrelativistic QCD. This is the first measurement of the pT fraction carried by prompt J/Ď mesons in jets at any experiment
Bose-Einstein correlations of same-sign charged pions in the forward region in pp collisions at âs=7 TeV
Bose-Einstein correlations of same-sign charged pions, produced in protonproton collisions at a 7 TeV centre-of-mass energy, are studied using a data sample collected
by the LHCb experiment. The signature for Bose-Einstein correlations is observed in the
form of an enhancement of pairs of like-sign charged pions with small four-momentum
difference squared. The charged-particle multiplicity dependence of the Bose-Einstein correlation parameters describing the correlation strength and the size of the emitting source
is investigated, determining both the correlation radius and the chaoticity parameter. The
measured correlation radius is found to increase as a function of increasing charged-particle
multiplicity, while the chaoticity parameter is seen to decreas
Measurement of the inelastic pp cross-section at a centre-of-mass energy of 13TeV
The cross-section for inelastic proton-proton collisions at a centre-of-mass energy of 13TeV is measured with the LHCb detector. The fiducial cross-section for inelastic interactions producing at least one prompt long-lived charged particle with momentum p > 2 GeV/c in the pseudorapidity range 2 < Ρ < 5 is determined to be Ď acc = 62:2 Âą 0:2 Âą 2:5mb. The first uncertainty is the intrinsic systematic uncertainty of the measurement, the second is due to the uncertainty on the integrated luminosity. The statistical uncertainty is negligible. Extrapolation to full phase space yields the total inelastic proton-proton cross-section Ď inel = 75:4 Âą 3:0 Âą 4:5mb, where the first uncertainty is experimental and the second due to the extrapolation. An updated value of the inelastic cross-section at a centre-of-mass energy of 7TeV is also reported
Performance of CMS muon reconstruction in pp collision events at sqrt(s) = 7 TeV
The performance of muon reconstruction, identification, and triggering in CMS
has been studied using 40 inverse picobarns of data collected in pp collisions
at sqrt(s) = 7 TeV at the LHC in 2010. A few benchmark sets of selection
criteria covering a wide range of physics analysis needs have been examined.
For all considered selections, the efficiency to reconstruct and identify a
muon with a transverse momentum pT larger than a few GeV is above 95% over the
whole region of pseudorapidity covered by the CMS muon system, abs(eta) < 2.4,
while the probability to misidentify a hadron as a muon is well below 1%. The
efficiency to trigger on single muons with pT above a few GeV is higher than
90% over the full eta range, and typically substantially better. The overall
momentum scale is measured to a precision of 0.2% with muons from Z decays. The
transverse momentum resolution varies from 1% to 6% depending on pseudorapidity
for muons with pT below 100 GeV and, using cosmic rays, it is shown to be
better than 10% in the central region up to pT = 1 TeV. Observed distributions
of all quantities are well reproduced by the Monte Carlo simulation.Comment: Replaced with published version. Added journal reference and DO
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