7,734 research outputs found
Inclusive Particle Production at LEP
New results on inclusive production of Sigma^- and Lambda(1520) and on proton
production in quark and gluon jets are presented. These results are based on 2
million hadronic Z decays collected with the DELPHI detector at LEP. They are
compared with the results of other LEP experiments and with models. It has been
shown that the total production rates of all light-flavour hadrons measured so
far at LEP 1 follow phenomenological laws related to the spin, isospin,
strangeness and mass of the particles. A significant proton enhancement in
gluon jets is observed, indicating that baryon production proceeds directly
from colour objects.Comment: LaTeX with moriond.sty; 4 pages with 2 eps-figures. Talk given at the
35th Rencontres de Moriond on QCD and High Energy Hadronic Interactions, Les
Arcs, France, March 18-25, 2000. To be published in the Proceeding
Determination of the strangeness contents of light-flavour isoscalars from its production rates in hadronic Z decays measured at LEP
A new phenomenological approach is suggested to determine the strangeness
contents of light-flavour isoscalars. This approach is based on
phenomenological laws of hadron production related to the spin, isospin,
strangeness content and mass of the particles. The ``effective'' numbers of s
and \bar{s} quarks in the isoscalar partners i_1 and i_2 are given by the
nonstrange-strange mixing angle \phi: k(i_1)=2\sin^2\phi and
k(i_2)=2\cos^2\phi. From the total production rates per hadronic Z decay of all
light-flavour hadrons measured so far at LEP the values for k are found to be:
k(\eta) \equiv 2-k(\eta^{\prime}) = 0.91 \pm 0.12, k(\phi) \equiv 2-k(\omega) =
1.94 \pm 0.09, k(f_2^{\prime}) \equiv 2-k(f_2) = 1.84 \pm 0.21 and k(f_0) =
0.09 \pm 0.13. Our results on the \eta--\eta^{\prime}, \omega--\phi and
f_2--f_2^{\prime} isoscalar mixing are consistent with the present experimental
evidence. Quite remarkably, our value for k(\eta) corresponds to the
singlet-octet mixing angle \theta_P = -12.4^{\circ} \pm 3.5^{\circ}. The
obtained strangeness content of the f_0(980) scalar/isoscalar is not consistent
with the values supported by different model studies. However, taking the
f_0(980) in our analysis with the mass of the bare state (K-matrix pole)
f_0^{bare}(720 \pm 100), the mixing angle is found to be: |\phi_S^{bare}| =
73^{\circ} \pm 7^{\circ} \pm 24^{\circ}, in good agreement with the prediction
of the K-matrix analysis.Comment: 12 pages, 2 figure
Determination of the strangeness content of light-flavour isoscalars from their production rates in hadronic Z decays at LEP
A new phenomenological approach is suggested for determining the strangeness
content of light-flavour isoscalars. This approach is based on phenomenological
laws of hadron production related to the spin, isospin, strangeness content and
mass of the particles. From the total production rates per hadronic Z decay of
all light-flavour hadrons, measured so far at LEP, the values of the
nonstrange-strange mixing angles are found to be |\phi_P| = 42.3^{\circ} \pm
3.5^{\circ}, |\phi_V| = 10^{\circ} \pm 8^{\circ}, |\phi_T| = 16^{\circ} \pm
11^{\circ} and |\phi_S| = 13^{\circ} \pm 9^{\circ}. Our results on the
\eta-\eta^{\prime}, \omega-\phi and f_2-f_2^{\prime} isoscalar mixing are
consistent with the present experimental evidence. The strangeness content
obtained for the f_0(980) scalar/isoscalar is not consistent with the values
supported by recent model studies and is discussed further in the framework of
our approach and the K-matrix analysis.Comment: Talk given at the 9th International Conference on Hadron Spectroscopy
(Protvino, 2001), 4 pages with 2 figure
Study of charge multiplicity in hadronic three-jet Z decays at LEP
The mean charge multiplicity in hadronic three-jet Z decays has been measured
with the DELPHI detector as a function of the event topology and compared with
recent theoretical calculations. The QCD colour factor ratio C_A/C_F was
determined, and the gluon contribution to this multiplicity was extracted
giving a measurement of the mean charge multiplicity of a two-gluon
colour-singlet system as a function of the effective c.m. energy covering the
range from 16 to 52 GeV.Comment: Talk given at the 32nd International Symposium on Multiparticle
Dynamics (ISMD 2002), Alushta, Ukraine, September 7 - 13, 2002; 4 pages with
2 eps-figure
Massless spinning particle and null-string on : projective-space approach
Massless spinning particle and tensionless string models on
background in the projective-space realization are proposed as constrained
Hamiltonian systems. Various forms of particle and string Lagrangians are
derived and classical mechanics is studied including the Lax-type
representation of the equations of motion. After that transition to the quantum
theory is discussed. Analysis of potential anomalies in the tensionless string
model necessitates introduction of ghosts and BRST charge. It is shown that
quantum BRST charge is nilpotent for any if coordinate-momentum ordering
for the phase-space bosonic variables, Weyl ordering for the fermions and
() ordering for ghosts is chosen, while conformal
reparametrizations and space-time dilatations turn out to be anomalous for the
ordering in terms of positive and negative Fourier modes of the phase-space
variables and ghosts.Comment: 23 pages, v4: In the title and abstract added adjective 'Massless'.
In subsection 2.2 the material has been rearranged to streamline the
presentation and also a comment added to explain the notation. Minor
improvements of the text and further typos corrected. Version accepted for
publicatio
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