126 research outputs found
Regge-cascade hadronization
We argue that the evolution of coloured partons into colour-singlet hadrons
has approximate factorization into an extended parton-shower phase and a
colour-singlet resonance--pole phase. The amplitude for the conversion of
colour connected partons into hadrons necessarily resembles Regge-pole
amplitudes since qq-bar resonance amplitudes and Regge-pole amplitudes are
related by duality. A `Regge-cascade' factorization property of the N-point
Veneziano amplitude provides further justification of this protocol. This
latter factorization property, in turn, allows the construction of general
multi-hadron amplitudes in amplitude-squared factorized form from (1->2) link
amplitudes. We suggest an algorithm with cascade-decay configuration, ordered
in the transverse momentum, suitable for Monte-Carlo simulation. We make a
simple implementation of this procedure in Herwig++, obtaining some improvement
to the description of the event-shape distributions at LEP.Comment: 10 pages, 9 figure
Nonperturbative hyperfine contribution to the and meson masses
Due to the nonperturbative contribution to the hyperfine splitting the mass
of the state is strongly correlated with the center of gravity of the multiplet: is less than by about 40 MeV (20 MeV) for the 1P (2P) state. For
the agreement with experiment is reached only if belongs to the
multiplet. The predicted mass of is MeV.
For the isoscalar meson a correlation between the mass of (1170)
and composed from light (strange) quarks also
takes place.Comment: 22 pages RevTe
Flavour structure of low-energy hadron pair photoproduction
We consider the process where and
are either mesons or baryons. The experimental findings for such quantities as
the and differential cross sections, in the energy range
currently probed, are found often to be in disparity with the scaling behaviour
expected from hard constituent scattering. We discuss the long-distance
pole--resonance contribution in understanding the origin of these phenomena, as
well as the amplitude relations governing the short-distance contribution which
we model as a scaling contribution. When considering the latter, we argue that
the difference found for the and the integrated cross
sections can be attributed to the s-channel isovector component. This
corresponds to the subprocess in the VMD
(vector-meson-dominance) language. The ratio of the two cross sections is
enhanced by the suppression of the component, and is hence constrained.
We give similar constraints to a number of other hadron pair production
channels. After writing down the scaling and pole--resonance contributions
accordingly, the direct summation of the two contributions is found to
reproduce some salient features of the and data.Comment: 12 pages, 9 figures, revised version to be published in EPJ
Total Hadronic Cross Sections and \pi^\mp \pi^+ Scattering
Recent measurements of the inelastic and total proton-proton cross section at
the LHC, and at cosmic ray energies by the Auger experiment, have
quantitatively confirmed fits to lower energy data constrained by the
assumption that the proton is asymptotically a black disk of gluons. We show
that data on \bar p(p)p,\pi^\mp p, and K^\mp p forward scattering support the
related expectation that the asymptotic behavior of all cross sections is
flavor independent. By using the most recent measurements from ATLAS, CMS,
TOTEM and Auger, we predict \sigma^{pp}_{\rm tot} (\sqrt s=8 {\rm TeV})=100.6
\pm 2.9 mb and \sigma^{pp}_{\rm tot} (\sqrt s=14 {\rm TeV})=110.8 \pm 3.5 mb,
as well as refine the total cross section \sigma^{pp}_{\rm tot} (\sqrt s=57
{\rm TeV})=139.6 \pm 5.4 mb. Our analysis also predicts the total \pi^\mp \pi^+
cross sections as a function of \sqrt s.Comment: Final version to be published in PRD (2012
The gluonic condensate from the hyperfine splitting in charmonium
The precision measurement of the hyperfine splitting MeV in the
Fermilab--E835 experiment allows to determine the gluonic condensate with
high accuracy if the gluonic correlation length is fixed. In our
calculations the negative value of MeV is
obtained only if the relatively small fm and
GeV are taken. These values correspond to the ``physical'' string tension
GeV). For fm the hyperfine splitting
is positive and grows for increasing . In particular for fm
and GeV the splitting MeV
is obtained, which is in accord with the recent CLEO result.Comment: 9 pages revtex 4, no figure
Scalar Particles in Lattice QCD
We report a project to study scalar particles by lattice QCD simulations.
After a brief introduction of the current situation of lattice study of the
sigma meson, we describe our numerical simulations of scalar mesons,
and . We observe a low sigma mass, , for
which the disconnected diagram plays an important role. For the kappa meson, we
obtain higher mass than the experimental value, i.e., .Comment: 4 figures, to be published in Proceedings of `International Symposium
on Hadron Spectroscopy, Chiral Symmetry and Relativistic Description of Bound
Systems' (in a series of KEK proceedings
Effects to Scalar Meson Decays of Strong Mixing between Low and High Mass Scalar Mesons
We analyze the mass spectroscopy of low and high mass scalar mesons and get
the result that the coupling strengths of the mixing between low and high mass
scalar mesons are very strong and the strengths of mixing for scalar
mesons and those of I=0 scalar mesons are almost same. Next, we analyze the
decay widths and decay ratios of these mesons and get the results that the
coupling constants for which represents the coupling of high
mass scalar meson -> two pseudoscalar mesons are almost same as the
coupling for the I=0. On the other hand, the coupling constant for
which represents the low mass scalar meson -> are far
from the coupling constant for I=0. We consider a resolution for this
discrepancy. Coupling constant for glueball -> is smaller than
the coupling . is .Comment: 15 pages, 6 figure
Asymptotic Energy Dependence of Hadronic Total Cross Sections from Lattice QCD
The nonperturbative approach to soft high-energy hadron-hadron scattering,
based on the analytic continuation of Wilson-loop correlation functions from
Euclidean to Minkowskian theory, allows to investigate the asymptotic energy
dependence of hadron-hadron total cross sections in lattice QCD. In this paper
we will show, using best fits of the lattice data with proper functional forms
satisfying unitarity and other physical constraints, how indications emerge in
favor of a universal asymptotic high-energy behavior of the kind B log^2 s for
hadronic total cross sections.Comment: Revised and extended version; 29 pages, 4 figure
A Precursor of Chiral Symmetry Restoration in the Nuclear Medium
Spectral enhancement near the 2m_{\pi} threshold in the I=J=0 channel in
nuclei is shown to be a distinct signal of the partial restoration of chiral
symmetry. The relevance of this phenomenon with the possible detection of
2\pi^{0} and 2\gamma in hadron-nucleus and photo-nucleus reactions is
discussed.Comment: Revtex, 4 pages, 3 eps figures, title and introduction changed, to
appear in Phys. Rev. Let
Outcrop Groundwater Prospecting, Drilling, and Well Construction in Hard Rocks in Semi-arid Regions
This chapter presents some recommendations for prospecting, drilling and well construction in hard rocks in semi-arid regions. Considering that these conditions are present in many countries where technology is not always available, the chapter concentrates on the most basic and simple methods to plan where best to drill and maximize success through the direct observation of rock types, weathering and fracturing. The advantage for the geologist and hydrogeologist in an arid or semi-arid environment is that vegetation is normally scarce and the weathering layer thin, allowing a direct view of the rock in circumstances impossible in other climate regions of the world. The close observation of the weathering material, and especially of the fracture network, mainly the fracture density, dip, extension and interconnection, can provide important information for a field hydrogeologist who can then plan the best place for drilling. The most appropriate drilling technique, if available in the area, is rotary percussion, also designated as down-the-hole drilling, with drilling rates that can achieve 100 m per day in normal circumstances. This allows a well to be constructed in about two days, essential in the case of disaster relief. Finally, some information is given about well construction, careful planning of the work, protection to preserve the water quality, avoiding problems of partial or total collapse of the hole during construction or of the well and after completion, and how to avoid direct contact between the surface or sub-surface waters with the aquifer along the walls of the well to protect the well and the aquifer against contamination
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