1,410 research outputs found
Chandrasekhar-Kendall functions in astrophysical dynamos
Some of the contributions of Chandrasekhar to the field of
magnetohydrodynamics are highlighted. Particular emphasis is placed on the
Chandrasekhar-Kendall functions that allow a decomposition of a vector field
into right- and left-handed contributions. Magnetic energy spectra of both
contributions are shown for a new set of helically forced simulations at
resolutions higher than what has been available so far. For a forcing function
with positive helicity, these simulations show a forward cascade of the
right-handed contributions to the magnetic field and nonlocal inverse transfer
for the left-handed contributions. The speed of inverse transfer is shown to
decrease with increasing value of the magnetic Reynolds number.Comment: 10 pages, 5 figures, proceedings of the Chandrasekhar Centenary
Conference, to be published in PRAMANA - Journal of Physic
Search for the rare decay
A search for the decay is performed, based on a data sample of 1.0 fb of collisions at collected by the LHCb experiment at the Large Hadron Collider. The observed number of candidates is consistent with the background-only hypothesis, yielding an upper limit of at 95 (90)% confidence level. This limit is a factor of thirty below the previous measurement
Commissioning and performance of the LHCb Silicon Tracker
The LHCb Silicon Tracker is a silicon micro-strip detector with a sensitive area of 12 m2 and a total of 272k readout channels. The Silicon Tracker consists of two parts that use different detector modules. The detector installation was completed by early summer 2008 and the commissioning without beam has reached its final stage, successfully overcoming most of the encountered problems. Currently, the detector has more than 99% of the channels fully functioning. Commissioning with particles has started using beam-induced events from the LHC injection tests in 2008 and 2009. These events allowed initial studies of the detector performance. Especially, the detector modules could be aligned with an accuracy of about 20μm. Furthermore, with the first beam collisions that took place end of 2009 we could further study the performance and improve the alignment of the detector
Angular analysis of the decay in the low- region
An angular analysis of the decay is performed using a data sample, corresponding to an integrated luminosity of 3.0 {\mbox{fb}^{-1}}, collected by the LHCb experiment in collisions at centre-of-mass energies of 7 and 8 TeV during 2011 and 2012. For the first time several observables are measured in the dielectron mass squared () interval between 0.002 and 1.120. The angular observables and which are related to the polarisation and to the lepton forward-backward asymmetry, are measured to be and , where the first uncertainty is statistical and the second systematic. The angular observables and which are sensitive to the photon polarisation in this range, are found to be and . The results are
consistent with Standard Model predictions
Measurement of asymmetries and polarisation fractions in decays
An angular analysis of the decay is performed using collisions corresponding to an integrated luminosity of collected by the LHCb experiment at a centre-of-mass energy TeV. A combined angular and mass analysis separates six helicity amplitudes and allows the measurement of the longitudinal polarisation fraction for the decay. A large scalar contribution from the and resonances is found, allowing the determination of additional asymmetries. Triple product and direct asymmetries are determined to be compatible with the Standard Model expectations. The branching fraction is measured to be
Observation of the decay from an amplitude analysis of decays
Proton-proton collision data recorded in 2011 and 2012 by the LHCb experiment, corresponding to an integrated luminosity of 3.0\invfb, are analysed to search for the charmless decay. More than 600 signal decays are selected and used to perform an amplitude analysis from which the decay is observed for the first time with 7.1 standard deviations significance. The fraction of decays yielding a longitudinally polarised final state is measured to be . The branching fraction, using the decay as reference, is also reported as
Evidence for the strangeness-changing weak decay
Using a collision data sample corresponding to an integrated luminosity of 3.0~fb, collected by the LHCb detector, we present the first search for the strangeness-changing weak decay . No hadron decay of this type has been seen before. A signal for this decay, corresponding to a significance of 3.2 standard deviations, is reported. The relative rate is measured to be , where and are the and fragmentation fractions, and is the branching fraction. Assuming is bounded between 0.1 and
0.3, the branching fraction would lie in the range from to
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