2,059 research outputs found
On the low x behaviour of nuclear shadowing
We calculate the x dependence of nuclear shadowing at moderate values of Q^2
by using HERA diffractive data and, for consistency, F2 parameterization of
ZEUS. We show that no decrease of shadowing occurs down to very low x (x =
10^-4).Comment: 9 pages, submitted on june for publicatio
Longitudinal and Transverse Nuclear Shadowing
Nuclear shadowing arises from multiple scattering of the hadronic
fluctuations of the virtual photon in a nucleus. We predict different
longitudinal and transverse shadowing and an A-dependence of R which can be up
to a 50% effect. The possibility of detecting nuclear effects on R at HERA is
discussed.Comment: latex, 6 page
Limit quantum efficiency for violation of Clauser-Horne Inequality for qutrits
In this paper we present the results of numerical calculations about the
minimal value of detection efficiency for violating the Clauser - Horne
inequality for qutrits. Our results show how the use of non-maximally entangled
states largely improves this limit respect to maximally entangled ones. A
stronger resistance to noise is also found.Comment: Phys. Rev. A in pres
Testing Ultrafast Two-Photon Spectral Amplitudes via Optical Fibres
We test two-dimensional TPSA of biphoton light emitted via ultrafast
spontaneous parametric down-conversion (SPDC) using the effect of
group-velocity dispersion in optical fibres. Further, we apply this technique
to demonstrate the engineering of biphoton spectral properties by acting on the
pump pulse shape
The time as an emergent property of quantum mechanics, a synthetic description of a first experimental approach
The "problem of time" in present physics substantially consists in the fact
that a straightforward quantization of the general relativistic evolution
equation and constraints generates for the Universe wave function the
Wheeler-De Witt equation, which describes a static Universe. Page and Wootters
considered the fact that there exist states of a system composed by entangled
subsystems that are stationary, but one can interpret the component subsystems
as evolving: this leads them to suppose that the global state of the universe
can be envisaged as one of this static entangled state, whereas the state of
the subsystems can evolve. Here we synthetically present an experiment, based
on PDC polarization entangled photons, that allows showing with a practical
example a situation where this idea works, i.e. a subsystem of an entangled
state works as a "clock" of another subsystem
Non universality of structure functions and measurement of the strange sea density
We show that there is no real conflict between the two determinations of the
strange sea density from the opposite--sign dimuon production and from the
difference of the structure functions measured in neutrino and muon deep
inelastic scattering. Once non universal sea parton densities are introduced,
which take into account the effects of different mass thresholds and different
longitudinal contributions, the discrepancy is shown to disappear and both sets
of data are simultaneously well reproduced. No need for a large strange sea
content of the nucleon emerges.Comment: latex, DFTT-93-3
The Strange Quark Distribution
We discuss the latest CCFR determination of the strange sea density of the
proton. We comment on the differences with a previous, leading--order, result
and point out the relevance of quark mass effects and current non--conservation
effects. By taking them into account it is possible to solve the residual
discrepancy with another determination of the strange quark distribution. Two
important sources of uncertainties are also analyzed.Comment: 19page
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