1,397 research outputs found
Comparing fragmentation of strange quark in Z decays and K+p reactions
The ratios of the production rates K*(892)/K, phi/K, rho^0/pi, omega/pi,
Delta^{++}/p, Sigma+(1385)/Lambda, Xi^-/Lambda and their x_p dependences
obtained from results of the LEP and SLD experiments in Z hadronic decays are
analysed. The corresponding ratios for promptly produced mesons are estimated
at x_p -> 1. A comparison of the LEP results with those from the Mirabelle and
BEBC K+p experiments at 32 and 70 GeV/c shows striking similarity in
fragmentation of the strange valence quark of the incident K+ and strange
quarks produced in Z decays. The JETSET model describes the LEP, Mirabelle and
BEBC results. The model of Pei is consistent with the data for mesons, but
presumably underestimates the fractions of primary octet baryons. The quark
combinatorics model of Anisovich et al.is incompatible with the data.Comment: tex and sty files and 6 eps-figure
Multiplicity distributions in e+e- annihilation into hadrons and pure birth branching processes
Recursive solution for a general homogeneous in time pure birth branching
process with simultaneous production of any number of particles and with
continuous evolution parameter is given. Calculational algorithm based on the
use of Koenigs function and functional Schroder equation is described. It is
shown that multiplicity distributions in e+e- annihilation into hadrons for
c.m. energies up to 189 GeV are well described by the modified negative
binomial distribution, explained by simple pure birth branching process without
multiple simultaneous particle production. The energy dependence of the
evolution parameter is also discussed.Comment: 10 pages, Latex2e, JHEP.cls, 2 EPS figures, to be published in
Phys.Lett.
Analysis of Cumulant Moments in High Energy Hadron-Hadron Collisions by Truncated Multiplicity Distributions
Oscillatory behavior of cumulant moments obtained from the experimental data
in collisions and collisions are analyzed by the modified
negative binomial distribution (MNBD) and the negative binomial distribution
(NBD). Both distributions well describe the cumulant moments obtained from the
data. This fact shows sharp contrast to the result in collisions,
which is described by the the MNBD much better than by the NBD.Comment: 7 pages, Latex type, 7 figure
Relating production and masses of the vector and P-wave mesons for light and heavy flavours al LEP
The production rates of primary vector and P-wave mesons in Z hadronic decays are analysed. The mass dependence of production rates for the bottom, charm, strange charm and three families of the light-flavour mesons is found to be very similar, allowing to relate the relative production rates for mesons with different flavours and, possibly, their masses. The strange axial mesons K_1(1273) and K_1(1402) might be assigned to the 1^+(1/2) and 1^+(3/2) levels degenerate with the 0^+(1/2) and 2^+(3/2) levels of the K^*_0(1430) and K^*_2(1430), respectively, if the observed K^*_0(1430) mass is replaced by its ``bare'' q\bar{q} mass corresponding to the K-matrix pole and close to the K_1(1273) mass. Then the 0^+(1/2) and 1^+(1/2) levels are below the 1^+(3/2) and 2^+(3/2) levels for the strange, charm and bottom mesons
Description of local multiplicity fluctuations and genuine multiparticle correlations
Various parametrizations of the multiplicity distribution are studied using
the recently published large statistics OPAL results on multidimensional local
fluctuations and genuine correlations in e+e- -> Z -> hadrons. The measured
normalized factorial and cumulant moments are compared to the predictions of
the negative binomial distribution, the modified and generalized versions of
it, the log-normal distribution and the model of the generalized birth process
with immigration. This is the first study which uses the multiplicity
distribution parametrizations to describe high-order genuine correlations.
Although the parametrizations fit well the measured fluctuations and
correlations for low orders, they do show certain deviations at high orders. We
have shown that it is necessary to incorporate the multiparticle character of
the correlations along with the property of self-similarity to attain a good
description of the measurements.Comment: 15 pages, 2 ps figure
Modified Negative Binomial Description of the Multiplicity Distributions in Lepton-nucleon Scattering
It is shown that charged hadron multiplicity distributions in lepton-nucleon
scattering are fairly well described by the modified negative binomial
distribution in the energy range from 3-4 to 220 GeV. The energy behaviour of
the parameter k is similar to the dependence observed for e+e- annihilation.Comment: 12 pages, Latex, 2 Poscript figures, epsfig is used, to be published
in Physics Letters
Power Law in Hadron Production
In high energy p+p(bar) interactions the mean multiplicity and transverse
mass spectra of neutral mesons from eta to Upsilon (m = 0.5 - 10 GeV/c^2) and
the transverse mass spectra of pions (m_T > 1 GeV/c^2) reveal a remarkable
behaviour: they follow, over more than 10 orders of magnitude, the power-law
function:The parameters C and P are energy dependent, but similar for all
mesons produced at the same collision energy. This scaling resembles that
expected in the statistical description of hadron production: the parameter P
plays the role of a temperature and the normalisation constant C is analogous
to the system volume. The fundamental difference is, however, in the form of
the distribution function. In order to reproduce the experimental results and
preserve the basic structure of the statistical approach the Boltzmann factor
e^(-E/T) appearing in standard statistical mechanics has to be substituted by a
power-law factor (E/Lambda)^(-P).Comment: significantly revised version to appear in Phys. Lett.
Experimental studies of QCD using flavour tagged jets with DELPHI
Identified and events from DELPHI are
used to measure the ratio of the mean charged particle multiplicity
distribution between gluon and quark jets. The dependence of this ratio with
the jet energy is established using about three million Z decays. Results
from all other detectors are discussed and compared. A nice agreement is found
among all them. The ratio between the normalized total three-jet cross sections
of and events is also
determined. The preliminary value obtained indicates that quarks are
experimentaly seen to radiate less than light quarks due to their higher mass.
The suggested experimental error is 300 MeV for the mass
determination at the M scale.Comment: Latex, 5 pages, 3 figures,to appear in the Proceedings of the High
Energy Physics International Euroconference on Quantum Chromodynamics (QCD
'96), Montpellier, France, 4-12th July 1996. Ed. S. Narison, Nucl Phys. B
(Proc. Suppl.
Vector-to-Pseudoscalar and Meson-to-Baryon Ratios in Hadronic Z Decays at LEP
Mass dependences of the total production rates per hadronic Z decay of all
light-flavour hadrons measured so far at LEP are extrapolated to the zero mass
limit (m=0) using phenomenological laws of hadron production related to the
spin, isospin, strangeness content and mass of the particles. The
vector-to-pseudoscalar and meson-to-baryon ratios at m=0 are found to be: rho^+
/ 3 pi^+ = 1.2 +/- 0.3 and pi^+ / p = 2.9 +/- 0.3, in good agreement with the
predictions of quark combinatorics.Comment: LaTeX with sprocl.sty; 6 pages with 2 eps-figures; minor Editor's
corrections. Talk given at the 30th International Symposium on Multiparticle
Dynamics, Tihany, Lake Balaton, Hungary, October 9-15, 2000. To be published
in the Proceedings (World Scientific, Singapore
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