3,340 research outputs found
The Relativity Concept Inventory: development, analysis and results
We report on a concept inventory for special relativity: the development
process, data analysis methods, and results from an introductory relativity
class. The Relativity Concept Inventory tests understanding of kinematic
relativistic concepts. An unusual feature is confidence testing for each
question. This can provide additional information; for example high confidence
correlated with incorrect answers suggests a misconception. A novel aspect of
our data analysis is the use of Monte Carlo simulations to determine the
significance of correlations. This approach is particularly useful for small
sample sizes, such as ours. Our results include a gender bias that was not
present in other assessment, similar to that reported for the Force Concept
Inventory
The Level-0 Muon Trigger for the LHCb Experiment
A very compact architecture has been developed for the first level Muon
Trigger of the LHCb experiment that processes 40 millions of proton-proton
collisions per second. For each collision, it receives 3.2 kBytes of data and
it finds straight tracks within a 1.2 microseconds latency. The trigger
implementation is massively parallel, pipelined and fully synchronous with the
LHC clock. It relies on 248 high density Field Programable Gate arrays and on
the massive use of multigigabit serial link transceivers embedded inside FPGAs.Comment: 33 pages, 16 figures, submitted to NIM
Neutrino Telescopes in the Mediterranean Sea
The observation of high energy extraterrestrial neutrinos can be an
invaluable source of information about the most energetic phenomena in the
Universe. Neutrinos can shed light on the processes that accelerate charge
particles in an incredibly wide range of energies both within and outside our
Galaxy. They can also help to investigate the nature of the dark matter that
pervades the Universe. The unique properties of the neutrino make it peerless
as a cosmic messenger, enabling the study of dense and distant astrophysical
objects at high energy. The experimental challenge, however, is enormous. Due
to the weakly interacting nature of neutrinos and the expected low fluxes very
large detectors are required. In this paper we briefly review the neutrino
telescopes under the Mediterranean Sea that are operating or in progress. The
first line of the ANTARES telescope started to take data in March 2006 and the
full 12-line detector was completed in May 2008. By January 2009 more than one
thousand neutrino events had been reconstructed. Some of the results of ANTARES
will be reviewed. The NESTOR and NEMO projects have made a lot of progress to
demonstrate the feasibility of their proposed technological solutions. Finally,
the project of a km3-scale telescope, KM3NeT, is rapidly progressing: a
conceptual design report was published in 2008 and a technical design report is
expected to be delivered by the end of 2009
Surface step effects on Si (100) under uniaxial tensile stress, by atomistic calculations
This paper reports a study of the influence of the step at a silicon surface
under an uniaxial tensile stress, using an empirical potential. Our aim was to
find conditions leading to nucleation of dislocations from the step. We
obtained that no dislocations could be generated with such conditions. This
behaviour, different from the one predicted for metals, could be attributed
either to the covalent bonding or to the cubic diamond structure
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Search for lepton-flavour-violating decays of Higgs-like bosons.
A search is presented for a Higgs-like boson with mass in the range 45 to 195 GeV/c2 decaying into a muon and a tau lepton. The dataset consists of proton-proton interactions at a centre-of-mass energy of 8 TeV , collected by the LHCb experiment, corresponding to an integrated luminosity of 2 fb-1 . The tau leptons are reconstructed in both leptonic and hadronic decay channels. An upper limit on the production cross-section multiplied by the branching fraction at 95% confidence level is set and ranges from 22 pb for a boson mass of 45 GeV/c2 to 4 pb for a mass of 195 GeV/c2
Differential branching fraction and angular analysis of the decay B 0 → K ∗0 μ + μ −
The angular distribution and differential branching fraction of the decay B[superscript O]→ K*[superscript O]μ⁺μ⁻ are studied using a data sample, collected by the LHCb experiment in pp collisions at s√=7 TeV, corresponding to an integrated luminosity of 1.0 fb⁻¹. Several angular observables are measured in bins of the dimuon invariant mass squared, q². A first measurement of the zero-crossing point of the forward-backward asymmetry of the dimuon system is also presented. The zero-crossing point is measured to be q²₀=4.9±0.9GeV²/c⁴, where the uncertainty is the sum of statistical and systematic uncertainties. The results are consistent with the Standard Model predictions
The pd <--> pi+ t reaction around the Delta resonance
The pd pi+ t process has been calculated in the energy region around the
Delta-resonance with elementary production/absorption mechanisms involving one
and two nucleons. The isobar degrees of freedom have been explicitly included
in the two-nucleon mechanism via pi-- and rho-exchange diagrams. No free
parameters have been employed in the analysis since all the parameters have
been fixed in previous studies on the simpler pp pi+ d process. The
treatment of the few-nucleon dynamics entailed a Faddeev-based calculation of
the reaction, with continuum calculations for the initial p-d state and
accurate solutions of the three-nucleon bound-state equation. The integral
cross-section was found to be quite sensitive to the NN interaction employed
while the angular dependence showed less sensitivity. Approximately a 4% effect
was found for the one-body mechanism, for the three-nucleon dynamics in the p-d
channel, and for the inclusion of a large, possibly converged, number of
three-body partial states, indicating that these different aspects are of
comparable importance in the calculation of the spin-averaged observables.Comment: 40 Pages, RevTex, plus 5 PostScript figure
Observation of two new baryon resonances
Two structures are observed close to the kinematic threshold in the mass spectrum in a sample of proton-proton collision data, corresponding
to an integrated luminosity of 3.0 fb recorded by the LHCb experiment.
In the quark model, two baryonic resonances with quark content are
expected in this mass region: the spin-parity and
states, denoted and .
Interpreting the structures as these resonances, we measure the mass
differences and the width of the heavier state to be
MeV,
MeV,
MeV, where the first and second
uncertainties are statistical and systematic, respectively. The width of the
lighter state is consistent with zero, and we place an upper limit of
MeV at 95% confidence level. Relative
production rates of these states are also reported.Comment: 17 pages, 2 figure
Search for CP violation in decays
A model-independent search for direct CP violation in the Cabibbo suppressed
decay in a sample of approximately 370,000 decays is
carried out. The data were collected by the LHCb experiment in 2010 and
correspond to an integrated luminosity of 35 pb. The normalized Dalitz
plot distributions for and are compared using four different
binning schemes that are sensitive to different manifestations of CP violation.
No evidence for CP asymmetry is found.Comment: 13 pages, 8 figures, submitted to Phys. Rev.
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