1,224 research outputs found
Effective dynamics of an electrically charged string with a current
Equations of motion for an electrically charged string with a current in an
external electromagnetic field with regard to the first correction due to the
self-action are derived. It is shown that the reparametrization invariance of
the free action of the string imposes constraints on the possible form of the
current. The effective equations of motion are obtained for an absolutely
elastic charged string in the form of a ring (circle). Equations for the
external electromagnetic fields that admit stationary states of such a ring are
revealed. Solutions to the effective equations of motion of an absolutely
elastic charged ring in the absence of external fields as well as in an
external uniform magnetic field are obtained. In the latter case, the frequency
at which one can observe radiation emitted by the ring is evaluated. A model of
an absolutely nonstretchable charged string with a current is proposed. The
effective equations of motion are derived within this model, and a class of
solutions to these equations is found.Comment: 14 pages, 3 figures, format changed, minor change
Artificial Intelligence to Enhance Mission Science Output for In-situ Observations: Dealing with the Sparse Data Challenge
In the Earth's magnetosphere, there are fewer than a dozen dedicated probes
beyond low-Earth orbit making in-situ observations at any given time. As a
result, we poorly understand its global structure and evolution, the mechanisms
of its main activity processes, magnetic storms, and substorms. New Artificial
Intelligence (AI) methods, including machine learning, data mining, and data
assimilation, as well as new AI-enabled missions will need to be developed to
meet this Sparse Data challenge.Comment: 4 pages, 1 figure; Heliophysics 2050 White Pape
Properties of Neutral Charmed Mesons in Proton--Nucleus Interactions at 70 GeV
The results of treatment of data obtained in the SERP-E-184experiment
"Investigation of mechanisms of the production of charmed particles in
proton-nucleus interactions at 70 GeV and their decays" by irradiating the
active target of the SVD-2 facility consisting of carbon, silicon, and lead
plates, are presented. After separating a signal from the two-particle decay of
neutral charmed mesons and estimating the cross section for charm production at
a threshold energy {\sigma}(c\v{c})=7.1 \pm 2.4(stat.) \pm 1.4(syst.)
\mub/nucleon, some properties of D mesons are investigated. These include the
dependence of the cross section on the target mass number (its A dependence);
the behavior of the differential cross sections d{\sigma}/dpt2 and
d{\sigma}/dxF; and the dependence of the parameter {\alpha} on the kinematical
variables xF, pt2, and plab. The experimental results in question are compared
with predictions obtained on the basis of the FRITIOF7.02 code.Comment: 9 pages, 9 figures,3 table
The Speed of Fronts of the Reaction Diffusion Equation
We study the speed of propagation of fronts for the scalar reaction-diffusion
equation \, with . We give a new integral
variational principle for the speed of the fronts joining the state to
. No assumptions are made on the reaction term other than those
needed to guarantee the existence of the front. Therefore our results apply to
the classical case in , to the bistable case and to cases in
which has more than one internal zero in .Comment: 7 pages Revtex, 1 figure not include
Observation of narrow baryon resonance decaying into in pA-interactions at with SVD-2 setup
SVD-2 experiment data have been analyzed to search for an exotic baryon
state, the -baryon, in a decay mode at on IHEP
accelerator. The reaction with a limited multiplicity was
used in the analysis. The invariant mass spectrum shows a resonant
structure with and . The statistical significance of this peak was estimated to be of . The mass and width of the resonance is compatible with the recently
reported - baryon with positive strangeness which was predicted as an
exotic pentaquark () baryon state. The total cross section for
production in pN-interactions for was estimated to be
and no essential deviation from A-dependence for inelastic
events was found.Comment: 8 pages, 7 figures, To be submitted to Yadernaya Fizika. v3-v5 - Some
references added, minor typos correcte
Precision luminosity measurements at LHCb
Measuring cross-sections at the LHC requires the luminosity to be determined accurately at each centre-of-mass energy âs. In this paper results are reported from the luminosity calibrations carried out at the LHC interaction point 8 with the LHCb detector for âs = 2.76, 7 and 8 TeV (proton-proton collisions) and for âsNN = 5 TeV (proton-lead collisions). Both the "van der Meer scan" and "beam-gas imaging" luminosity calibration methods were employed. It is observed that the beam density profile cannot always be described by a function that is factorizable in the two transverse coordinates. The introduction of a two-dimensional description of the beams improves significantly the consistency of the results. For proton-proton interactions at âs = 8 TeV a relative precision of the luminosity calibration of 1.47% is obtained using van der Meer scans and 1.43% using beam-gas imaging, resulting in a combined precision of 1.12%. Applying the calibration to the full data set determines the luminosity with a precision of 1.16%. This represents the most precise luminosity measurement achieved so far at a bunched-beam hadron collider
Performance of the LHCb vertex locator
The Vertex Locator (VELO) is a silicon microstrip detector that surrounds the proton-proton interaction region in the LHCb experiment. The performance of the detector during the first years of its physics operation is reviewed. The system is operated in vacuum, uses a bi-phase CO2 cooling system, and the sensors are moved to 7 mm from the LHC beam for physics data taking. The performance and stability of these characteristic features of the detector are described, and details of the material budget are given. The calibration of the timing and the data processing algorithms that are implemented in FPGAs are described. The system performance is fully characterised. The sensors have a signal to noise ratio of approximately 20 and a best hit resolution of 4 ÎŒm is achieved at the optimal track angle. The typical detector occupancy for minimum bias events in standard operating conditions in 2011 is around 0.5%, and the detector has less than 1% of faulty strips. The proximity of the detector to the beam means that the inner regions of the n+-on-n sensors have undergone space-charge sign inversion due to radiation damage. The VELO performance parameters that drive the experiment's physics sensitivity are also given. The track finding efficiency of the VELO is typically above 98% and the modules have been aligned to a precision of 1 ÎŒm for translations in the plane transverse to the beam. A primary vertex resolution of 13 ÎŒm in the transverse plane and 71 ÎŒm along the beam axis is achieved for vertices with 25 tracks. An impact parameter resolution of less than 35 ÎŒm is achieved for particles with transverse momentum greater than 1 GeV/c
Search for Decay
We have searched for the charmless hadronic decay of B0 mesons into two
neutral pions. Using 9.13fb^-1 taken at the Upsilon(4S) with the CLEO detector,
we obtain an improved upper limit for the branching fraction BR(B0-->pi0pi0) <
5.7*10^-6 at the 90% confidence level.Comment: pages postscript, also available through
http://w4.lns.cornell.edu/public/CLN
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