Search results for "GASES"
showing 10 items of 1098 documents
Searches for neutral Higgs bosons in e+e− collisions at centre-of-mass energies from 192 to 202 GeV
2000
Searches for neutral Higgs bosons are performed with the 237 pb-1 of data collected in 1999 by the ALEPH detector at LEP, for centre-of-mass energies between 191.6 and 201.6 GeV. These searches apply to Higgs bosons within the context of the Standard Model and its minimal supersymmetric extension (MSSM) as well as to invisibly decaying Higgs bosons. No evidence of a signal is seen. A lower limit on the mass of the Standard Model Higgs boson of 107.7 GeV/c2 at 95% confidence level is set. In the MSSM, lower limits of 91.2 and 91.6 GeV/c2 are derived for the masses of the neutral Higgs bosons h and A, respectively. For a Higgs boson decaying invisibly and produced with the Standard Model cros…
Antihydrogen production in a combined trap
1993
In this paper we study the properties of a Paul trap with a superimposed magnetic field (combined trap) and discuss the possibility of using this trap to simultaneously store positrons and antiprotons to form antihydrogen.
Extremely cold antiprotons for antihydrogen production
1993
The possibility to produce, trap and study antihydrogen atoms rests upon the recent availability of extremely cold antiprotons in a Penning trap. Over the last five years, our TRAP Collaboration has slowed, cooled and stored antiprotons at energies 1010 lower than was previously possible. The storage time exceeds 3.4 months despite the extremely low energy, which corresponds to 4.2 K in temperature units. The first example of measurements which become possible with extremely cold antiprotons is a comparison of the antiproton inertial masses which shows they are the same to a fractional accuracy of 4×10−8. (This is 1000 times more accurate than previous comparisons and large additional incre…
EBIT trapping program
1993
The LLNL electron beam ion trap provides the world's only source of stationary highly charged ions up to bare U. This unique capability makes many new atomic and nuclear physics experiments possible.
Precision studies in traps: Measurement of fundamental constants and tests of fundamental theories
2003
Experiments on single atomic particles confined in Penning ion traps have contributed significantly to the improvements of fundamental constants and to tests of the theory of Quantum Electrodynamics for free and bound electrons. The most precise value of the fine structure constant as well as the electron mass have been derived from trap experiments. Numerous atomic masses of interest for fundamental questions have been determined with precisions of 10 � 9 or below. Further progress is envisaged in the near future.
Search for Higgs bosons of the minimal supersymmetric standard model in pp¯ collisions at s=1.96 TeV
2012
We report results from searches for neutral Higgs bosons produced in p-pbar collisions recorded by the Dzero experiment at the Fermilab Tevatron Collider. We study the production of inclusive neutral Higgs boson in the tautau final state and in association with a b quark in the btautau and bbb final states. These results are combined to improve the sensitivity to the production of neutral Higgs bosons in the context of the minimal supersymmetric standard model (MSSM). The data are found to be consistent with expectation from background processes. Upper limits on MSSM Higgs boson production are set for Higgs boson masses ranging from 90 to 300 GeV. We exclude tanBeta>20-30 for Higgs boson ma…
Bose-Einstein correlations in W-pair decays
2000
Bose-Einstein correlations are studied in semileptonic (WW --> q (q) over bar lv) and fully hadronic (WW --> q (q) over bar q (q) over bar) W-pair decays with the ALEPH detector at LEP at centre-of-mass energies of 172, 183 and 189 GeV. They are compared with those made at the Z peak after correction for the different flavour compositions. A Monte Carlo model of Bose-Einstein correlations based on the JETSET hadronization scheme was tuned to the Z data and reproduces the correlations in the WW --> q (q) over bar lv events. The same Monte Carlo reproduces the correlations in the WW --> q (q) over bar q (q) over bar channel assuming independent fragmentation of the two W's. A variant of this …
Search for a heavy Higgs boson decaying into a Z boson and another heavy Higgs boson in the ℓℓbb final state in pp collisions at s=13 TeV with the AT…
2018
A search for a heavy neutral Higgs boson, A, decaying into a Z boson and another heavy Higgs boson, H, is performed using a data sample corresponding to an integrated luminosity of 36.1 fb(-1) from ...
Heavy mass expansion, light-by-light scattering through pointlike quanta, and the anomalous magnetic moment of the muon
2003
Contributions from light-by-light scattering to ${(g}_{\ensuremath{\mu}}\ensuremath{-}2)/2,$ the anomalous magnetic moment of the muon, are mediated by the exchange of charged fermions or scalar bosons. Assuming large masses M, pointlike couplings for the virtual particles and employing the technique of large mass expansion, analytical results are obtained for virtual fermions and scalars in the form of a series in ${(m}_{\ensuremath{\mu}}{/M)}^{2}.$ This series is well convergent even for the case ${M=m}_{\ensuremath{\mu}}.$ For pointlike virtual fermions, the expansion confirms published analytical formulas. For virtual scalars, the result can be used to evaluate the contribution from poi…
A single trapped antiproton and antiprotons for antihydrogen production
1993
During the last several years, our TRAP collaboration has pioneered techniques for slowing, trapping, cooling and indefinitely storing antiprotons to energies more than 1010 times lower than previously possible. The radio signal from a single trapped antiproton is now being used for precision measurements. Many cold antiprotons are “stacked” as another important step toward the eventual production of antihydrogen, and positrons have been trapped in vacuum.