745 research outputs found
Quark Model and Neutral Strange Secondary Production by Neutrino and Antineutrino Beams
The experimental data on and production by and
beams are compared with the predictions of quark model assuming
that the direct production of secondaries dominates. Disagreement of these
predictions with the data allows one to suppose that there exists considerable
resonance decay contribution to the multiplicities of produced secondaries.Comment: 6 pages, no figures, 2 table
Radiative decays of quarkonium states, momentum operator expansion and nilpotent operators
We present the method of calculation of radiative decays of composite
quark-antiquark systems with different J^{PC}: (Q\bar Q)_{in} -> gamma (Q\bar
Q)_{out}. The method is relativistic invariant, it is based on the double
dispersion relation integrals over the masses of composite mesons, it can be
used for the high spin particles and provides us with the gauge invariant
transition amplitudes. We apply this method to the case when the photon is
emitted by a constituent in the intermediate state (additive quark model). We
perform the momentum operator expansion of the spin amplitudes for the decay
processes. The problem of nilpotent spin operators is discussed.Comment: 21 pages, 1 figur
Chemical Freeze-out of Strange Particles and Possible Root of Strangeness Suppression
Two approaches to treat the chemical freeze-out of strange particles in
hadron resonance gas model are analyzed. The first one employs their
non-equillibration via the usual \gamma_s factor and such a model describes the
hadron multiplicities measured in nucleus-nucleus collisions at AGS, SPS and
RHIC energies with \chi^2/dof = 1.15. Surprisingly, at low energies we find not
the strangeness suppression, but its enhancement. Also we suggest an
alternative approach to treat the strange particle freeze-out separately, but
with the full chemical equilibration. This approach is based on the
conservation laws which allow us to connect the freeze-outs of strange and
non-strange hadrons. Within the suggested approach the same set of hadron
multiplicities can be described better than within the conventional approach
with \chi^2/dof = 1.06. Remarkably, the fully equilibrated approach describes
the strange hyperons and antihyperons much better than the conventional one.Comment: 6 pages, 5 figure
Evolution of Baryon-Free Matter Produced in Relativistic Heavy-Ion Collisions
A 3-fluid hydrodynamic model is introduced for simulating heavy-ion
collisions at incident energies between few and about 200 AGeV. In addition to
the two baryon-rich fluids of 2-fluid models, the new model incorporates a
third, baryon-free (i.e. with zero net baryonic charge) fluid which is created
in the mid-rapidity region. Its evolution is delayed due to a formation time
, during which the baryon-free fluid neither thermalizes nor interacts
with the baryon-rich fluids. After formation it thermalizes and starts to
interact with the baryon-rich fluids. It is found that for =0 the
interaction strongly affects the baryon-free fluid. However, at reasonable
finite formation time, =1 fm/c, the effect of this interaction turns out
to be substantially reduced although still noticeable. Baryonic observables are
only slightly affected by the interaction with the baryon-free fluid.Comment: 17 pages, 3 figures, submitted to the issue of Phys. of Atomic Nuclei
dedicated to S.T. Belyaev on the occasion of his 80th birthday, typos
correcte
The study of the proton-proton collisions at the beam momentum 1628 MeV/c
The detailed investigation of the single pion production reactions and at the incident proton momentum 1628 MeV/c has
been carried out. The data are analyzed in the framework of the event-by-event
maximum likelihood method together with the data measured
earlier in the energy region below 1 GeV. At 1628 MeV/c the largest
contributions stem from the , , ,
and initial partial waves.Comment: 7 pages, 9 figure
Broadband optical gain via interference in the free electron laser: principles and proposed realizations
We propose experimentally simplified schemes of an optically dispersive
interface region between two coupled free electron lasers (FELs), aimed at
achieving a much broader gain bandwidth than in a conventional FEL or a
conventional optical klystron composed of two separated FELs. The proposed
schemes can {\it universally} enhance the gain of FELs, regardless of their
design when operated in the short pulsed regime
- …