Search results for "elementary"
showing 10 items of 863 documents
Measurements of the top-quark mass using charged particle tracking
2010
21 páginas, 13 figuras, 6 tablas.-- PACS numbers: 12.15.-y, 13.85.-t, 14.60.-z, 14.65.Fy.-- CDF Collaboration: et al.
Search for right-handed W bosons in top quark decay
2005
We present a measurement of the fraction f+ of right-handed W bosons produced in top quark decays, based on a candidate sample of $t\bar{t}$ events in the lepton+jets decay mode. These data correspond to an integrated luminosity of 230pb^-1, collected by the DO detector at the Fermilab Tevatron $p\bar{p}$ Collider at sqrt(s)=1.96 TeV. We use a constrained fit to reconstruct the kinematics of the $t\bar{t}$ and decay products, which allows for the measurement of the leptonic decay angle $\theta^*$ for each event. By comparing the $\cos\theta^*$ distribution from the data with those for the expected background and signal for various values of f+, we find f+=0.00+-0.13(stat)+-0.07(syst). This …
First search for extremely high energy cosmogenic neutrinos with the IceCube Neutrino Observatory.
2010
We report on the results of the search for extremely-high energy (EHE) neutrinos with energies above $10^7$ GeV obtained with the partially ($\sim$30%) constructed IceCube in 2007. From the absence of signal events in the sample of 242.1 days of effective livetime, we derive a 90% C.L. model independent differential upper limit based on the number of signal events per energy decade at $E^2 \phi_{\nu_e+\nu_\mu+\nu_\tau}\simeq 1.4 \times 10^{-6}$ GeV cm$^{-2}$ sec$^{-1}$ sr$^{-1}$ for neutrinos in the energy range from $3\times10^7$ to $3\times10^9$ GeV.
Measurement of the b hadron lifetime with the dipole method
1993
A measurement of the average lifetime of b hadrons has been performed with the dipole method on a sample of 260000 hadronic Z decays recorded with the ALEPH detector during 1991. The dipole is the distance between the vertices built in the opposite hemispheres. The mean dipole is extracted from all the events without attempting b enrichment. Comparing the average of the data dipole distribution with a Monte Carlo calibration curve obtained with different b lifetimes, an average b hadron lifetime of 1.51 +/- 0.08 ps is extracted. RI ANTONELLI, ANTONELLA/C-6238-2011; Buttar, Craig/D-3706-2011; Stahl, Achim/E-8846-2011; Passalacqua, Luca/F-5127-2011; Murtas, Fabrizio/B-5729-2012; St.Denis, Ric…
Role of statistical fluctuations in the emission ofδelectrons from dissipative heavy-ion collisions
1990
Energy spectra of {delta} electrons emitted in coincidence with deep-inelastic heavy-ion collisions are calculated within a Langevin Monte Carlo description using the surface-friction model. We investigate the effects that wipe out the originally expected oscillatory pattern of the spectra. Emphasis is placed on the role of statistical fluctuations in extracting interaction time distributions of deep-inelastic collisions from the measured {delta}-electron spectra. The calculations are compared to data for U+Au at 8.65 MeV/nucleon.
Heavy-mesons exchange and the backward deuteron electrodisintegration
1992
Backward electrodisintegration of the deuteron is calculated using an exchange-current operator containing π, η, ρ, ω, δ, σ, andA1 exchanges. The deuteron and1S0np wave functions are derived from the Bonn OBEPs. For completeness, we introduced theA1-meson exchange into the OBEP's as well. As a consequence, the value ofD-state probabilityPD is increased by 0.2%–0.8%. The computed cross sections are compared with new data.
What can be learnt about nuclear polarization from a consistency analysis ofe ? cross sections and muonic X-rays for208Pb and the isotone pair209Bi/2…
1977
A joint analysis of recent electron scattering cross sections and muonic atom X-ray energies is performed for208Pb and the isotone pair209Bi/208Pb. From the compatibility of the experimental data one can learn about the nuclear polarisation correction. However, we find this information not to be as accurate as other authors claimed when we take into consideration the ambiguities in the treatment of the corrections of the higher levels.
Exchange currents in electric transitions and the r�le of siegert's theorem: A case study in deuteron photodisintegration
1981
The size of exchange corrections to electric transitions is investigated for deuteron photodisintegration. Large contributions are found in El transitions, which become dominant above 40 MeV. Most of them are already included by using Siegert's theorem together with classical one-body operators. Higher multipoles are only little affected except for rather high energies. The Born approximation for the final states gives in general a poor description.
Evidence for excited 0+ states in94Sr
1982
Beta-delayed neutron measurements on95Rb have indicated evidence for two heretofore unknown excited O+ states in94Sr which are not fed by s -decay from the Jπ = 3− ground state of94Rb.
Half-lives and delayed neutron emission probabilities of short-lived Rb and Cs precursors
1979
Half-lives and delayed-neutron emission probabilities (P n ) of short-lived Rb and Cs precursors in the mass chains 94–98 and 143–147 were measured. Sources of isotope separated nuclides were obtained from the on-line mass-separator OSTIS installed at the Grenoble high-flux reactor.