183 research outputs found
Classification of Complex Polynomial Vector Fields in One Complex Variable
A classification of the global structure of monic and centered one-variable
complex polynomial vector fields is presented.Comment: 57 pages, 35 figures, submitted to the Journal of Difference
Equations and Application
Effect of initial conditions on the speed of reaction-diffusion fronts
The effect of initial conditions on the speed of propagating fronts in reaction-diffusion equations is examined in the framework of the Hamilton-Jacobi theory. We study the transition between quenched and nonquenched fronts both analytically and numerically for parabolic and hyperbolic reaction diffusion. Nonhomogeneous media are also analyzed and the effect of algebraic initial conditions is also discussed
A new measurement of direct CP violation in two pion decays of the neutral kaon
The NA48 experiment at CERN has performed a new measurement of direct CP
violation, based on data taken in 1997 by simultaneously collecting K_L and K_S
decays into pi0pi0 and pi+pi-. The result for the CP violating parameter
Re(epsilon'/epsilon) is (18.5 +/- 4.5(stat)} +/- 5.8 (syst))x10^{-4}.Comment: 18 pages, 6 figure
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
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
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
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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