442 research outputs found
Nowcasting of thunderstorm severity with Machine Learning in the Alpine Region
Presentación realizada en la 3rd European Nowcasting Conference, celebrada en la sede central de AEMET en Madrid del 24 al 26 de abril de 2019
Measurement of the Omega_c Lifetime
We present the measurement of the lifetime of the Omega_c we have performed
using three independent data samples from two different decay modes. Using a
Sigma- beam of 340 GeV/c we have obtained clean signals for the Omega_c
decaying into Xi- K- pi+ pi+ and Omega- pi+ pi- pi+, avoiding topological cuts
normally used in charm analysis. The short but measurable lifetime of the
Omega_c is demonstrated by a clear enhancement of the signals at short but
finite decay lengths. Using a continuous maximum likelihood method we
determined the lifetime to be tau(Omega_c) = 55 +13-11(stat) +18-23(syst) fs.
This makes the Omega_c the shortest living weakly decaying particle observed so
far. The short value of the lifetime confirms the predicted pattern of the
charmed baryon lifetimes and demonstrates that the strong interaction plays a
vital role in the lifetimes of charmed hadrons.Comment: 15 pages, including 7 figures; gzipped, uuencoded postscrip
Search for the exotic Resonance in 340GeV/c -Nucleus Interactions
We report on a high statistics search for the resonance in
-nucleus collisions at 340GeV/c. No evidence for this resonance is
found in our data sample which contains 676000 candidates above
background. For the decay channel and the
kinematic range 0.150.9 we find a 3 upper limit for the
production cross section of 3.1 and 3.5 b per nucleon for reactions with
carbon and copper, respectively.Comment: 5 pages, 4 figures, modification of ref. 43 and 4
Centrality dependence of the expansion dynamics in Pb-Pb collisions at 158 A GeV/c
Two-particle correlation functions of negatively charged hadrons from Pb-Pb
collisions at 158 GeV/c per nucleon have been measured by the WA97 experiment
at the CERN SPS. A Coulomb correction procedure that assumes an expanding
source has been implemented. Within the framework of an expanding thermalized
source model the size and dynamical state of the collision fireball at
freeze-out have been reconstructed as a function of the centrality of the
collision. Less central collisions exhibit a different dynamics than central
ones: both transverse and longitudinal expansion velocities are slower, the
expansion duration is shorter and the system freezes out showing smaller
dimensions and higher temperature.Comment: 22 pages, 11 figures, Te
Colour transparency: a novel test of QCD in nuclear interactions
Colour transparency is a cute and indispensable property of QCD as the gauge
theory of strong interaction. CT tests of QCD consist of production of the
perturbative small-sized hadronic state and measuring the strngth of its
non-perturbative diffraction nteraction in a nuclear matter. The energy
depenednce of the final- state interaction in a nuclear matter probes a
dynamical evolution from the perturbative small-sized state to the full-sized
nonperturbative hadron. QCD observables of CT experiments correspond to a novel
mechanism of scanning of hadronic wave functions from the large nonperturbative
to the small perturbative size. In these lectures, which are addressed to
experimentalists and theorists, I discuss the principle ideas of CT physics and
the physics potential of the hadron and electron facilities in the > 10 GeV
energy range. The special effort was made to present the material in the
pedagigical and self-consistent way, with an emphasis on the underlying rich
quantum-mechanical interference phenomena.Comment: 82 pages, 28 figures on request from the author., Landau Institute
rep. 9/93. (Lecture notes), [email protected]
LHC1: a semiconductor pixel detector readout chip with internal, tunable delay providing a binary pattern of selected events
The Omega3/LHCl pixel detector readout chip comprises a matrix of 128 X 16 readout cells of 50 mu m X 500 mu m and peripheral functions with 4 distinct modes of initialization and operation, together more than 800 000 transistors. Each cell contains a complete chain of amplifier, discriminator with adjustable threshold and fast-OR output, a globally adjustable delay with local fine-tuning, coincidence logic and memory. Every cell can be individually addressed for electrical test and masking, First results have been obtained from electrical tests of a chip without detector as well as from source measurements, The electronic noise without detector is similar to 100 e(-) rms. The lowest threshold setting is close to 2000 e(-) and non-uniformity has been measured to be better than 450 e(-) rms at 5000 e(-) threshold. A timewalk of < 10 ns and a precision of < 6 ns rms on a delay of 2 mu s have been measured. The results may be improved by further optimization
Measurement of the beauty production cross-section in 350 GeV/c -Cu interactions
Using a sample of triggered events, produced in --Cu interactions at 350~GeV, we have identified 26 beauty events. The estimated background in this sample is events. From these data, assuming a linear A-dependence, we measure a beauty production cross-section integrated over all of nb/N
WA92: a fixed target experiment to trigger on and identify beauty particle decays
We describe the detectors and trigger system used in the CERN WA92 experiment. The experiment was designed to study the production and decay of beauty particles from 350 GeV/ interactions in copper and tungsten targets. Charged particle tracking is performed using the Omega spectrometer. Silicon microstrip detectors are used to provide precise tracking information in the region of the production and the decay of heavy-flavoured particles and to trigger on the resulting high impact parameter tracks. The precision of vertex reconstruction corresponds to of the mean B-decay proper lifetime. Lepton and high transverse momentum hadron signals are also used in the trigger, which accepts 29\% of B-decays and rejects 98\% of non-beauty interactions
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