16,078 research outputs found
On the polarization properties of the charmed baryon Lambda^+_c in the Lambda^+_c -> p + K^- + pi^+ + pi^0 decay
The polarization properties of the charmed Lambda^+_c baryon are investigated
in weak non-leptonic four-body Lambda^+_c -> p + K^- + pi^+ + pi^0 decay. The
probability of this decay and the angular distribution of the probability are
calculated in the effective quark model with chiral U(3)XU(3) symmetry
incorporating Heavy Quark Effective theory (HQET) and the extended
Nambu-Jona-Lasinio model with a linear realization of chiral U(3)XU(3)
symmetry. The theoretical value of the probability of the decay Lambda^+_c -> p
+ K^- + pi^+ + pi^0 relative to the probability of the decay Lambda^+_c -> p +
K^- + pi^+ does not contain free parameters and fits well experimental data.
The application of the obtained results to the analysis of the polarization of
the Lambda^+_c produced in the processes of photo and hadroproduction is
discussed.Comment: 10 pages, no figures, Late
Diffractive Hard Dijets and Nuclear Parton Distributions
Diffraction plays an exceptional role in DIS off heavy nuclei. First,
diffraction into hard dijets is an unique probe of the unintegrated glue in the
target. Second, because diffraction makes 50 per cent of total DIS off a heavy
target, understanding diffraction in a saturation regime is crucial for a
definition of saturated nuclear parton densities. After brief comments on the
Nikolaev-Zakharov (NZ) pomeron-splitting mechanism for diffractive hard dijet
production, I review an extension of the Nikolaev-Schafer-Schwiete (NSS)
analysis of diffractive dijet production off nuclei to the definition of
nuclear partons in the saturation regime. I emphasize the importance of
intranuclear final state interactions for the parton momentum distributions.Comment: 9 pages, 2 figures, to be published in Proceedings of the Workshop on
Exclusive Processes at High Momentum Transfer, Jefferson Lab, May 15-18,
2002. Typos corrected, discussion of the results extende
High Density QCD, Saturation and Diffractive DIS
We review a consistent description of the fusion and saturation of partons in
the Lorentz-contracted ultrarelativistic nuclei in terms of a nuclear
attenuation of color dipole states of the photon and collective
Weizs\"acker-Williams (WW) gluon structure function of a nucleus. Diffractive
DIS provides a basis for the definition of the WW nuclear glue. The point that
all observables for DIS off nuclei are uniquely calculable in terms of the
nuclear WW glue amounts to a new form of factorization in the saturation
regime.Comment: 13 pages, 4 figures, Invited talk at NATO Advanced Research Workshop
On Diffraction 2002, 31 Aug - 6 Sep 2002, Alushta, Ukrain
The hard scale in the exclusive rho-meson production in diffractive DIS
We re-examine the issue of the pQCD factorization scale in the exclusive rho
production in diffractive DIS from the k_t-factorization point of view. We find
that this scale differs significantly from, and possesses much flatter Q^2
behavior than widely used value (Q^2 + m_\rho^2)/4. With these results in mind,
we discuss the Q^2 shape of the rho meson production cross section. We
introduce rescaled cross sections, which might provide further insight into the
dynamics of rho production. We also comment on the recent ZEUS observation of
energy-independent ratio sigma(gamma* p --> rho p) / sigma_{tot}(gamma*p).Comment: 14 pages, 7 eps 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
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