15 research outputs found
Hadron-nucleon Total Cross Section Fluctuations from Hadron-nucleus Total Cross Sections
The extent to which information about fluctuations in hadron-nucleon total
cross sections in the frozen approximation can be extracted from very high
energy hadron-nucleus total cross section measurements for a range of heavy
nuclei is discussed. The corrections to the predictions of Glauber theory due
to these fluctuations are calculated for several models for the distribution
functions, and differences of the order of 50 mb are found for heavy nuclei.
The generating function for the moments of the hadron-nucleon cross section
distributions can be approximately determined from the derivatives of the
hadron-nucleus total cross sections with respect to the nuclear geometric cross
section. The argument of the generating function, however, it limited to the
maximum value of a dimensionless thickness function obtained at zero impact
parameter for the heaviest nuclear targets: about 1.8 for pions and 3.0 for
nucleons.Comment: 14 pages, revtex 3.0, 4 figures available upon reques
Diffractive photon dissociation in the saturation regime from the Good and Walker picture
Combining the QCD dipole model with the Good and Walker picture, we formulate
diffractive dissociation of a photon of virtuality Q^2 off a hadronic target,
in the kinematical regime in which Q is close to the saturation scale and much
smaller than the invariant mass of the diffracted system. We show how the
obtained formula compares to the HERA data and discuss what can be learnt from
such a phenomenology. In particular, we argue that diffractive observables in
these kinematics provide useful pieces of information on the saturation regime
of QCD.Comment: 17 pages, 7 figures, revte
Nonperturbative Effects in Gluon Radiation and Photoproduction of Quark Pairs
We introduce a nonperturbative interaction for light-cone fluctuations
containing quarks and gluons. The interaction squeezes the transverse
size of these fluctuations in the photon and one does not need to simulate this
effect via effective quark masses. The strength of this interaction is fixed by
data. Data on diffractive dissociation of hadrons and photons show that the
nonperturbative interaction of gluons is much stronger. We fix the parameters
for the nonperturbative quark-gluon interaction by data for diffractive
dissociation to large masses (triple-Pomeron regime). This allows us to predict
nuclear shadowing for gluons which turns out to be not as strong as
perturbative QCD predicts. We expect a delayed onset of gluon shadowing at shadowing of quarks. Gluon shadowing turns out to be nearly scale
invariant up to virtualities due to presence of a semihard
scale characterizing the strong nonperturbative interaction of gluons. We use
the same concept to improve our description of gluon bremsstrahlung which is
related to the distribution function for a quark-gluon fluctuation and the
interaction cross section of a fluctuation with a nucleon. We expect
the nonperturbative interaction to suppress dramatically the gluon radiation at
small transverse momenta compared to perturbative calculations.Comment: 58 pages of Latex including 11 figures. Shadowing for soft gluons and
Fig. 6 are added as well as a few reference
Unitarity bounds for inelastic diffraction
Unitarity in the s-channel is invoked to derive an upper bound for the inelastic diffractive cross-section as a function of impact parameter. The application of this bound to high-energy proton-proton scattering strongly suggests that inelastic diffraction should be peripheral in the impact parameter space.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/22059/1/0000478.pd
Experimental tests of the factorisation of Regge trajectories in the proton fragmentation region
We present double differential cross sections for the reactions K- + p → π± + anything at 8.25 GeV/c. Using published data for reactions K+ + p→ π- + anything and p + p → π+ anything we predict the differential cross sections for γ + p → π- + anything, π- + p → π- + anything and π- + p → π+ + anything in the target fragmentation region based on factorisation of the pomeron and Regge trajectories. Our predictions agree with the experimental data and support the hypothesis of factorisation of the Regge trajectories in the target fragmentation region. © 1973
A case-control study of the effect of environmental sanitation on diarrhoea morbidity in Malawi.
Connections between single-level and bilevel multiobjective optimization
The relationship between bilevel optimization and multiobjective optimization has been studied by several authors, and there have been repeated attempts to establish a link between the two. We unify the results from the literature and generalize them for bilevel multiobjective optimization. We formulate sufficient conditions for an arbitrary binary relation to guarantee equality between the efficient set produced by the relation and the set of optimal solutions to a bilevel problem. In addition, we present specially structured bilevel multiobjective optimization problems motivated by real-life applications and an accompanying binary relation permitting their reduction to single-level multiobjective optimization problems.peerReviewe