201 research outputs found
Angular and Current-Target Correlations in Deep Inelastic Scattering at HERA
Correlations between charged particles in deep inelastic ep scattering have
been studied in the Breit frame with the ZEUS detector at HERA using an
integrated luminosity of 6.4 pb-1. Short-range correlations are analysed in
terms of the angular separation between current-region particles within a cone
centred around the virtual photon axis. Long-range correlations between the
current and target regions have also been measured. The data support
predictions for the scaling behaviour of the angular correlations at high Q2
and for anti-correlations between the current and target regions over a large
range in Q2 and in the Bjorken scaling variable x. Analytic QCD calculations
and Monte Carlo models correctly describe the trends of the data at high Q2,
but show quantitative discrepancies. The data show differences between the
correlations in deep inelastic scattering and e+e- annihilation.Comment: 26 pages including 10 figures (submitted to Eur. J. Phys. C
Searches for excited fermions in ep collisions at HERA
Searches in ep collisions for heavy excited fermions have been performed with the ZEUS detector at HERA. Excited states of electrons and quarks have been searched for in e^+p collisions at a centre-of-mass energy of 300 GeV using an integrated luminosity of 47.7 pb^-1. Excited electrons have been sought via the decays e*->egamma, e*->eZ and e*->nuW. Excited quarks have been sought via the decays q*->qgamma and q*->qW. A search for excited neutrinos decaying via nu*->nugamma, nu*->nuZ and nu*->eW is presented using e^-p collisions at 318 GeV centre-of-mass energy, corresponding to an integrated luminosity of 16.7 pb^-1. No evidence for any excited fermion is found, and limits on the characteristic couplings are derived for masses below 250 GeV
Search for n-nbar oscillation in Super-Kamiokande
A search for neutron-antineutron () oscillation was undertaken in
Super-Kamiokande using the 1489 live-day or neutron-year
exposure data. This process violates both baryon and baryon minus lepton
numbers by an absolute value of two units and is predicted by a large class of
hypothetical models where the seesaw mechanism is incorporated to explain the
observed tiny neutrino masses and the matter-antimatter asymmetry in the
Universe. No evidence for oscillation was found, the lower limit of
the lifetime for neutrons bound in O, in an analysis that included all
of the significant sources of experimental uncertainties, was determined to be
~years at the 90\% confidence level. The corresponding
lower limit for the oscillation time of free neutrons was calculated to be ~s using a theoretical value of the nuclear suppression factor of
~s and its uncertainty.Comment: 8 pages, 2 figure
Search for n-nbar oscillation in Super-Kamiokande
A search for neutron-antineutron () oscillation was undertaken in
Super-Kamiokande using the 1489 live-day or neutron-year
exposure data. This process violates both baryon and baryon minus lepton
numbers by an absolute value of two units and is predicted by a large class of
hypothetical models where the seesaw mechanism is incorporated to explain the
observed tiny neutrino masses and the matter-antimatter asymmetry in the
Universe. No evidence for oscillation was found, the lower limit of
the lifetime for neutrons bound in O, in an analysis that included all
of the significant sources of experimental uncertainties, was determined to be
~years at the 90\% confidence level. The corresponding
lower limit for the oscillation time of free neutrons was calculated to be ~s using a theoretical value of the nuclear suppression factor of
~s and its uncertainty.Comment: 8 pages, 2 figure
Angular and Current-target Correlations in Deep Inelastic Scattering at HERA
Correlations between charged particles in deep inelastic e+ p scattering have been studied in the Breit frame with the ZEUS detector at HERA using an integrated luminosity of 6.4pb-1. Short-range correlations are analysed in terms of the angular separation between current-region particles within a cone centred around the virtual photon axis. Long-range correlations between the current and target regions have also been measured. The data support predictions for the scaling behaviour of the angular correlations at high Q2 and for anti-correlations between the current and target regions over a large range in Q2 and in the Bjorken scaling variable x. Analytic QCD calculations and Monte Carlo models correctly describe the trends of the data at high Q2, but show quantitative discrepancies. The data show differences between the correlations in deep inelastic scattering and e+e- annihilation
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