25 research outputs found
Analysis of Bose-Einstein correlations in e+e- -> W+W- events including final state interactions
Recently DELPHI Collaboration reported new data on Bose-Einstein correlations
(BEC) measured in e+e- -> W^+W^- events. Apparently no enhancement has been
observed. We have analyzed these data including final state interactions (FSI)
of both Coulomb and strong (s-wave) origin and found that there is enhancement
in BEC but it is overshadowed by the FSI which are extremely important for
those events. We have found the following values for the size of the
interaction range beta and the degree of coherence lambda: beta=0.87 +/- 0.31fm
and lambda=1.19 +/- 0.48, respectively.Comment: 7pages, 4 figure
S-wave Meson-Meson Scattering from Unitarized U(3) Chiral Lagrangians
An investigation of the s-wave channels in meson-meson scattering is
performed within a U(3) chiral unitary approach. Our calculations are based on
a chiral effective Lagrangian which includes the eta' as an explicit degree of
freedom and incorporates important features of the underlying QCD Lagrangian
such as the axial U(1) anomaly. We employ a coupled channel Bethe-Salpeter
equation to generate poles from composed states of two pseudoscalar mesons. Our
results are compared with experimental phase shifts up to 1.5 GeV and effects
of the eta' within this scheme are discussed.Comment: 18 pages, 6 figure
Another look at scattering in the scalar channel
We set up a general framework to describe scattering below 1 GeV
based on chiral low-energy expansion with possible spin-0 and 1 resonances.
Partial wave amplitudes are obtained with the method, which satisfy
unitarity, analyticity and approximate crossing symmetry. Comparison with the
phase shift data in the J=0 channel favors a scalar resonance near the
mass.Comment: 17 pages, 5 figures, REVTe
Analyticity, Crossing Symmetry and the Limits of Chiral Perturbation Theory
The chiral Lagrangian for Goldstone boson scattering is a power series
expansion in numbers of derivatives. Each successive term is suppressed by
powers of a scale, , which must be less than of order where is the Goldstone boson decay constant and is the
number of flavors. The chiral expansion therefore breaks down at or below . We argue that the breakdown of the chiral expansion is
associated with the appearance of physical states other than Goldstone bosons.
Because of crossing symmetry, some ``isospin'' channels will deviate from their
low energy behavior well before they approach the scale at which their low
energy amplitudes would violate unitarity. We argue that the estimates of
``oblique'' corrections from technicolor obtained by scaling from QCD are
untrustworthy.Comment: harvmac, 18 pages (3 figures), HUTP-92/A025, BUHEP-92-18, new version
fixes a TeX problem in little mod
Meson-Meson Scattering in the Quark Model: Spin Dependence and Exotic Channels
We apply a quark interchange model to spin-dependent and exotic meson-meson
scattering. The model includes the complete set of standard quark model forces,
including OGE spin-orbit and tensor and scalar confinement spin-orbit.
Scattering amplitudes derived assuming SHO and Coulomb plus linear plus
hyperfine meson wavefunctions are compared. In I=2 pi pi we find approximate
agreement with the S-wave phase shift from threshold to 1.5 GeV, where we
predict an extremum that is supported by the data. Near threshold we find rapid
energy dependence that may reconcile theoretical estimates of small scattering
lengths with experimental indications of larger ones based on extrapolation of
measurements at moderate kpi^2. In PsV scattering we find that the quark-quark
L*S and T forces map into L*S and T meson-meson interactions, and the P-wave
L*S force is large. Finally we consider scattering in J^PC-exotic channels, and
note that some of the Deck effect mechanisms suggested as possible nonresonant
origins of the pi_1(1400) signal are not viable in this model.Comment: 51 pages, 10 figures, uses epsf.sty epsfig.st
A Quark Model Calculation of gamma gamma to pi pi Including Final State Interactions
A quark model calculation of the processes gamma gamma -> pi+ pi- and gamma
gamma -> pi0 pi0 is performed. At tree level, only charged pions couple to the
initial state photons and neutral pions are not expected in the final state.
However, a small but significant gamma gamma -> pi0 pi0 cross section is
observed. We demonstrate that this may be accounted for by a rotation in
isospin space induced by final state interactions. The resulting pi+ pi- cross
section is in good agreement with experiment while the pi0 pi0 cross section is
in qualitative agreement with the data.Comment: 22 Revtex pages, 5 postscript figure
The Final State Interaction in , and Related Processes
Final state interactions in the --wave system (I=0,2) are
re-examined on the basis of the Omn\`es-Mus\-khe\-li\-shvili equation and the
coupled channel formalism. The contributions to the pion scalar form factor
from and exchange in the --channel and from the
--channel resonance are separately evaluated and the role of the
nontrivial polynomial in the Omn\`es function in a coupled channel situation is
elucidated. Applications are made to and . It is
found that the contribution from the resonance to the form-factor is
strongly reduced by a nearby zero.Comment: PACS numbers: 13.75.Lb, 13.25.Es, 13.25.+m, 15 pages in plain latex
with epsf.sty, 10 figure
Recovery of the herbaceous layer in the young silver birch and black alder stands that developed spontaneously after a forest fire
The studies, which were conducted in southern Poland, focused on the recovery of the herb layer in
17-year-old post-fire silver birch and black alder forests. Although both types of stands, which are of the same age, developed spontaneously, the alder stands occupied damper sites (with thicker A horizons that survived the fire) than those in the birch forests. We surveyed the migration rates of 44 woodland species, primarily ancient woodland indicators, into both forests and the potential differences in these rates depending on their moisture regime and the community type represented by unburned forests, which were treated as the source of the woodland species pool. Additionally, the role of local depressions with high humidity that were covered by post-fire alder woods in the colonization process, as well as species survivorship and recolonisation, were estimated. Woodland species showed diverse migration paces among the sites; most of them migrated faster on more fertile sites with a higher humidity. Small patches of post-fire alder woods contributed to the recolonisation process since many woodland species in the herb layer survived the fire due to its high humidity, which inhibited the intensity of the forest fire. The recovery of woodland species in post-fire woods is the combined effect of regeneration, which relies on autochthonic propagules, and secondary succession, which is based on allochthonic propagules. Local depressions, which provide
refuges for fire-sensitive, dispersal-limited species, contribute to their survivorship and thus to the successive
recovery of herbaceous layers after a fire
Recovery of the herbaceous layer in the young silver birch and black alder stands that developed spontaneously after a forest fire
Defensive Strongholds and Fortified Castles in Poland—From the Art of Fortifications to Tourist Attractions
The scientific problem undertaken is the importance of castles for the functioning of cultural tourism in the opinion of the inhabitants of Central Europe. What is the use of medieval monuments for the art of fortifications today? The main method of research is a diagnostic survey carried out with the use of a survey on a group of N, important according to the statistics in the number of n = 614 respondents. Statistical analyzes were performed using Statistica version 13.3. On the basis of the presented research results, it can be concluded that the interests of the respondents are very broad and varied. Taking into account the relatively large group of respondents, the research results can be considered reliable. An important goal was supplementing the knowledge, meeting the needs of learning about history, and getting acquainted with the prevailing historical tradition in castles of Europe. The questions presented here accent the interests of castles for the functioning of cultural tourism in the opinion of the inhabitants of Central Europe