118 research outputs found
Doppler cooling of Ca+ ions in a Penning trap
Published versio
Measurement of charged particle multiplicities in collisions at TeV in the forward region
The charged particle production in proton-proton collisions is studied with
the LHCb detector at a centre-of-mass energy of TeV in different
intervals of pseudorapidity . The charged particles are reconstructed
close to the interaction region in the vertex detector, which provides high
reconstruction efficiency in the ranges and
. The data were taken with a minimum bias trigger, only requiring
one or more reconstructed tracks in the vertex detector. By selecting an event
sample with at least one track with a transverse momentum greater than 1 GeV/c
a hard QCD subsample is investigated. Several event generators are compared
with the data; none are able to describe fully the multiplicity distributions
or the charged particle density distribution as a function of . In
general, the models underestimate the charged particle production
The Scientific Foundations of Forecasting Magnetospheric Space Weather
The magnetosphere is the lens through which solar space weather phenomena are focused and directed towards the Earth. In particular, the non-linear interaction of the solar wind with the Earth's magnetic field leads to the formation of highly inhomogenous electrical currents in the ionosphere which can ultimately result in damage to and problems with the operation of power distribution networks. Since electric power is the fundamental cornerstone of modern life, the interruption of power is the primary pathway by which space weather has impact on human activity and technology. Consequently, in the context of space weather, it is the ability to predict geomagnetic activity that is of key importance. This is usually stated in terms of geomagnetic storms, but we argue that in fact it is the substorm phenomenon which contains the crucial physics, and therefore prediction of substorm occurrence, severity and duration, either within the context of a longer-lasting geomagnetic storm, but potentially also as an isolated event, is of critical importance. Here we review the physics of the magnetosphere in the frame of space weather forecasting, focusing on recent results, current understanding, and an assessment of probable future developments.Peer reviewe
Measurement of relative branching fractions of B decays to and mesons
The relative rates of B-meson decays into and mesons are
measured for the three decay modes in pp collisions recorded with the LHCb
detector. The ratios of branching fractions () are measured to be
,
,
where the third uncertainty is from the ratio of the and
branching fractions to .Comment: 14 pages, 1 figur
Measurement of prompt hadron production ratios in collisions at 0.9 and 7 TeV
The charged-particle production ratios , , ,
, and are measured with the LHCb detector using of collisions delivered by the LHC at TeV and
at TeV. The measurements are performed as a
function of transverse momentum and pseudorapidity . The
production ratios are compared to the predictions of several Monte Carlo
generator settings, none of which are able to describe adequately all
observables. The ratio is also considered as a function of rapidity
loss, , and is used to constrain models of
baryon transport.Comment: Incorrect entries in Table 2 corrected. No consequences for rest of
pape
Observation of X(3872) production in pp collisions at âs=7TeV
Using 34.7 pbâ1 of data collected with the LHCb
detector, the inclusive production of the X(3872) meson in
pp collisions at âs = 7 TeV is observed for the first time.
Candidates are selected in the X(3872)âJ/ÏÏ+Ïâ decay
mode, and used to measure Ï(ppâX(3872)+anything)B(X(3872)âJ/ÏÏ+Ïâ) = 5.4 ±1.3 (stat)±0.8 (syst) nb, where Ï(pp âX(3872) + anything) is the inclusive production cross section of X(3872) mesons with rapidity in the range 2.5â4.5 and transverse momentum in the range 5â20 GeV/c. In addition the masses of both the X(3872) and Ï(2S) mesons, reconstructed in the J/ÏÏ+Ïâ final state, are measured to be mX(3872) = 3871.95± 0.48 (stat)±0.12 (syst) MeV/c2 and
mÏ(2S) = 3686.12±0.06 (stat) ±0.10 (syst) MeV/c2
Measurement of the forward energy flow in pp collisions at √<span style="text-decoration:overline">s</span>=7 TeV
The energy flow created in pp collisions at sâ=7 TeV is studied within the pseudorapidity range 1.9<η<4.9 with data collected by the LHCb experiment. The measurements are performed for inclusive minimum-bias interactions, hard scattering processes and events with an enhanced or suppressed diffractive contribution. The results are compared to predictions given by Pythia-based and cosmic-ray event generators, which provide different models of soft hadronic interactions
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