79 research outputs found
Geometric Constructions of Nongeometric String Theories
We advocate a framework for constructing perturbative closed string
compactifications which do not have large-radius limits. The idea is to augment
the class of vacua which can be described as fibrations by enlarging the
monodromy group around the singular fibers to include perturbative stringy
duality symmetries. As a controlled laboratory for testing this program, we
study in detail six-dimensional (1,0) supersymmetric vacua arising from
two-torus fibrations over a two-dimensional base. We also construct some
examples of two-torus fibrations over four-dimensional bases, and comment on
the extension to other fibrations.Comment: Explanations clarified, typos corrected, references adde
Observation of hard scattering in photoproduction events with a large rapidity gap at HERA
Events with a large rapidity gap and total transverse energy greater than 5
GeV have been observed in quasi-real photoproduction at HERA with the ZEUS
detector. The distribution of these events as a function of the
centre of mass energy is consistent with diffractive scattering. For total
transverse energies above 12 GeV, the hadronic final states show predominantly
a two-jet structure with each jet having a transverse energy greater than 4
GeV. For the two-jet events, little energy flow is found outside the jets. This
observation is consistent with the hard scattering of a quasi-real photon with
a colourless object in the proton.Comment: 19 pages, latex, 4 figures appended as uuencoded fil
Observation of Events with an Energetic Forward Neutron in Deep Inelastic Scattering at HERA
In deep inelastic neutral current scattering of positrons and protons at the center of mass energy of 300 GeV, we observe, with the ZEUS detector, events with a high energy neutron produced at very small scattering angles with respect to the proton direction. The events constitute a fixed fraction of the deep inelastic, neutral current event sample independent of Bjorken x and Q2 in the range 3 · 10-4 \u3c xBJ \u3c 6 · 10-3 and 10 \u3c Q2 \u3c 100 GeV2
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