557 research outputs found
Multiparticle production and perturbative QCD
The perturbative quantum chromodynamics (QCD) is quite successful in the
description of main features of multiparticle production processes. Ten most
appealing characteristics are described in this brief review talk and compared
with QCD predictions. The general perturbative QCD approach is demonstrated and
its problems are discussed. It is shown that the analytical calculations at the
parton level with the low-momentum cut-off reproduce experimental data on the
hadronic final state surprisingly accurately even though the perturbative
expansion parameter is not very small. Moreover, the perturbative QCD has been
able not only to {\it describe} the existing data but also to {\it predict}
many new bright qualitative phenomena.Comment: 22 pages, 10 Figs, LATEX. Talk given at the conference "From the
smallest to largest distances", ITEP, Moscow, 24-26 May 200
Search for Higher Flavor Multiplets in Partial Wave Analyses
The possible existence of higher multi-quark flavor multiplets of baryons is
investigated. We argue that the S-matrix should have poles with any quantum
numbers, including those which are exotic. This argument provides a novel
justification for the existence of hadrons with arbitrary exotic structure.
Though it does not constitute a proof, there are still no theoretical arguments
against exotics. We then consider KN and piN scattering. Conventional and
modified partial-wave analyses provide several sets of candidates for
correlated pairs (Theta1, Delta), each of which could label a related 27-plet.
Properties of the pairs (masses, mass orderings, spin-parity quantum numbers)
do not quite correspond to the current theoretical expectations. Decay widths
of the candidates are either wider or narrower than expected. Possible reasons
for such disagreements are briefly discussed.Comment: 12 pages, 1 figure; v2: references corrected; v3: minor changes, to
appear in Eur.Phys.J.
Perturbative universality in QCD jet physics
I survey some recent advances in the applications of the analytical
perturbative approach to the description of particle distributions in multi-jet
processes. New tests of the perturbatively based picture in the (semi) soft
region are discussed.Comment: LaTeX, 15 pages, talk at the XXVII International Symposium on
Multiparticle Dynamics, Frascati (Rome), Italy, 8-12 September 199
Lifetime Differences in Heavy Mesons With Time Independent Measurements
Heavy meson pairs produced in the decays of heavy quarkonium resonances at e+
e- machines (beauty and tau-charm factories) have the useful property that the
two mesons are in the CP-correlated states. By tagging one of the mesons as a
CP eigenstate, a lifetime difference of heavy neutral meson mass eigenstates
width difference may be determined by measuring the leptonic branching ratio of
the other meson. We discuss the use of this and related methods both in the
case where time dependent mixing is small and when it is significant. We
consider the impact of possible CP-violating effects and present the complete
results for CP-entangled decay rates with CP-violation taken into account.Comment: 14 pages, 0 figures; 2 references added, results unchange
A study of gamma-families generated in nucleon-nucleus (NA) and pion-nucleus (pi A) interactions
The separation of the gamma families generated in nucleon-nuclear and pion-nuclear (PI-A) interactions is realized from the analysis of simulated gamma families. Some characteristics of NA and PI families and the influence of the process of inelastic charge-exchange of charged pions neutral ones type of PI + or - A yields are studied
A Conserved Vector Current test using low energy beta-beams
We discuss the possibility of testing the weak currents and, in particular,
the weak magnetism term through the measurement of the electron anti-neutrinos
capture by protons at a low energy beta-beam facility. We analyze the
sensitivity using both the total number of events and the angular distribution
of the positrons emitted in a water Cerenkov detector. We show that the weak
magnetism form factor might be determined with better than several percent
accuracy using the angular distribution. This offers a new way of testing the
Conserved Vector Current hypothesis.Comment: 8 pages, 5 figure
Mixed basis matrix elements for the subgroup reductions of SO(2,1)
By using the irreducible decomposition on the two-dimensional light cone, the mixed basis matrix elements for the three subgroup reductions of SO(2,1) are calculated. These matrix elements are calculated for the principal series only and can be expressed in terms of well-known special functions. As a consequence of appearing in this context, some new properties of these special functions are given
Hidden gauge formalism for the radiative decays of axial-vector mesons
The radiative decay of the axial-vector resonances into a pseudoscalar meson
and a photon is studied using the vector meson Lagrangian obtained from the
hidden gauge symmetry (HGS) formalism. The formalism is well suited to study
this problem since it deals with pseudoscalar and vector mesons in a unified
way, respecting chiral invariance. We show explicitly the gauge invariance of
the set of diagrams that appear in the approach and evaluate the radiative
decay width of the a1(1260) and b1(1235) axial vector meson resonances into pi
gamma. We also include the contribution of loops involving anomalous couplings
and compare the results to those obtained previously within another formalism.Comment: 24 pages, 6 tables, 11 figure
A comparative analysis of gamma and hadron families at the superhigh energies recorded in experiment Pamir
A comparative analysis of hadron and gamma families which have undergone the decascading procedure is made. Results are compared with different models of interactions. In hadron families with energies Summary E sub H sup gamma 20 TeV as well as in gamma families with energies Summary E sub gamma 70 TeV, increasing azimuthal anisotropy is observed
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