282 research outputs found
Ground-state baryons in nonperturbative quark dynamics
We review the results obtained in an Effective Hamiltonian (EH) approach for
the three-quark systems. The EH is derived starting from the Feynman--Schwinger
representation for the gauge-invariant Green function of the three quarks
propagating in the nonperturbative QCD vacuum and assuming the minimal area law
for the asymptotic of the Wilson loop. It furnishes the QCD consistent
framework within which to study baryons. The EH has the form of the
nonrelativistic three-quark Hamiltonian with the perturbative Coulomb-like and
nonperturbative string interactions and the specific mass term. After outlining
the approach, methods of calculations of the baryon eigenenergies and some
simple applications are explained in details. With only two parameters: the
string tension and the strong coupling constant
a unified quantitative description of the ground state light
and heavy baryons is achieved. The prediction of masses of the doubly heavy
baryons not discovered yet are also given. In particular, a mass of
for the lightest baryon is found by employing the hyperspherical
formalism to the three quark confining potential with the string junction.Comment: 25 pages, 4 figures included, LaTeX 2e; to be published in Phys.
Atom. Nuc
Pentaquarks in the Jaffe-Wilczek approximation
The masses of , and pentaquarks are
evaluated in a framework of both the Effective Hamiltonian approach to QCD and
spinless Salpeter using the Jaffe--Wilczek diquark approximation and the string
interaction for the diquark--diquark--antiquark system. The pentaquark masses
are found to be in the region above 2 GeV. That indicates that the Goldstone
boson exchange effects may play an important role in the light pentaquarks. The
same calculations yield the mass of pentaquark 3250 MeV
and pentaquark 6509 MeV.Comment: 14 pages, 2 tables, LaTeX2e. References correcte
Nucleon matrix elements and baryon masses in the Dirac orbital model
Using the expansion of the baryon wave function in a series of products of
single quark bispinors (Dirac orbitals), the nonsinglet axial and tensor
charges of a nucleon are calculated. The leading term yields in
good agreement with experiment. Calculation is essentially parameter-free and
depends only on the strong coupling constant value . The importance
of lower Dirac bispinor component, yielding 18% to the wave function
normalization is stressed. As a check, the baryon decuplet masses in the
formalism of this model are also computed using standard values of the string
tension and the strange quark mass ; the results being in a good
agreement with experiment.Comment: 8 pages, 2 tables; LaTeX2
Measurement of the analysing power in proton-proton elastic scattering at small angles
The proton analysing power in elastic scattering has been measured
at small angles at COSY-ANKE at 796 MeV and five other beam energies between
1.6 and 2.4 GeV using a polarised proton beam. The asymmetries obtained by
detecting the fast proton in the ANKE forward detector or the slow recoil
proton in a silicon tracking telescope are completely consistent. Although the
analysing power results agree well with the many published data at 796 MeV, and
also with the most recent partial wave solution at this energy, the ANKE data
at the higher energies lie well above the predictions of this solution at small
angles. An updated phase shift analysis that uses the ANKE results together
with the World data leads to a much better description of these new
measurements.Comment: 5 pages, 3 figure
The heavy baryons in the nonperturbative string approach
We present some piloting calculations of the short-range correlation
coefficients for the light and heavy baryons and masses of the doubly heavy
baryons and () in the framework of the
simple approximation within the nonperturbative QCD approach.Comment: 21 pages; to appear in Phys. Atom. Nuc
Measurement of the absolute differential cross section of proton-proton elastic scattering at small angles
The differential cross section for proton-proton elastic scattering has been
measured at a beam energy of 1.0 GeV and in 200 MeV steps from 1.6 to 2.8 GeV
for centre-of-mass angles in the range from 12-16 degrees to 25-30 degrees,
depending on the energy. Absolute normalisations of typically 3% were achieved
by studying the energy losses of the circulating beam of the COSY storage ring
as it passed repeatedly through the windowless hydrogen target of the ANKE
magnetic spectrometer. It is shown that the data have a significant impact upon
a partial wave analysis. After extrapolating the differential cross sections to
the forward direction, the results are broadly compatible with the predictions
of forward dispersion relations
History of exotic Meson (4-quark) and Baryon (5-quark) States
I briefly review the history of exotic meson (4-quark) and baryon (5-quark)
states, which is rooted in the formalism of Regge pole and duality. There are
robust model-independent predictions for the exchange of 4-quark (Baryonium)
Regge trajectories in several processes, which are strongly supported by
experiment. On the other hand the predictions for the spectroscopy of 4-quark
resonances are based on specific QCD inspired models, with some experimental
support. The corresponding predictions for the recently discovered exotic
baryon (Pentaquark) state are briefly discussed.Comment: 14 pages Latex including 4 eps figures, final version to appear as a
topical review in J. Phys.
Luminescent properties of Bi-doped polycrystalline KAlCl4
We observed an intensive near-infrared luminescence in Bi-doped KAlCl4
polycrystalline material. Luminescence dependence on the excitation wavelength
and temperature of the sample was studied. Our experimental results allow
asserting that the luminescence peaked near 1 um belongs solely to Bi+ ion
which isomorphically substitutes potassium in the crystal. It was also
demonstrated that Bi+ luminescence features strongly depend on the local ion
surroundings
Nuclear matter at high density: Phase transitions, multiquark states, and supernova outbursts
Phase transition from hadronic matter to quark-gluon matter is discussed for
various regimes of temperature and baryon number density. For small and medium
densities, the phase transition is accurately described in the framework of the
Field Correlation Method, whereas at high density predictions are less certain
and leave room for the phenomenological models. We study formation of
multiquark states (MQS) at zero temperature and high density. Relevant MQS
components of the nuclear matter can be described using a previously developed
formalism of the quark compound bags (QCB).
Partial-wave analysis of nucleon-nucleon scattering indicates the existence
of 6QS which manifest themselves as poles of -matrix. In the framework of
the QCB model, we formulate a self-consistent system of coupled equations for
the nucleon and 6QS propagators in nuclear matter and the G-matrix. The
approach provides a link between high-density nuclear matter with the MQS
components and the cumulative effect observed in reactions on the nuclei, which
requires the admixture of MQS in the wave functions of nuclei kinematically.
6QS determine the natural scale of the density for a possible phase
transition into the MQS phase of nuclear matter. Such a phase transition can
lead to dynamic instability of newly born protoneutron stars and dramatically
affect the dynamics of supernovae. Numerical simulations show that the phase
transition may be a good remedy for the triggering supernova explosions in the
spherically symmetric supernova models. A specific signature of the phase
transition is an additional neutrino peak in the neutrino light curve. For a
Galactic core-collapse supernova, such a peak could be resolved by the present
neutrino detectors. The possibility of extracting the parameters of the phase
of transition from observation of the neutrino signal is discussed also.Comment: 57 pages, 22 figures, 7 tables; RevTeX 4; submitted to Phys. Atom.
Nuc
Higgs bosons in the simplest SUSY models
Nowadays in the MSSM the moderate values of are almost excluded
by LEP II lower bound on the lightest Higgs boson mass. In the Next-to-Minimal
Supersymmetric Standard Model the theoretical upper bound on it increases and
reaches maximal value in the strong Yukawa coupling limit when all solutions of
renormalization group equations are concentrated near the quasi-fixed point.
For calculation of Higgs boson spectrum the perturbation theory method can be
applied. We investigate the particle spectrum in the framework of the modified
NMSSM which leads to the self-consistent solution in the strong Yukawa coupling
limit. This model allows one to get GeV at values of
. In the investigated model the lightest Higgs boson mass
does not exceed GeV. The upper bound on the lightest CP-even
Higgs boson mass in more complicated supersymmetric models is also discussed.Comment: 27 pages, 5 figures included, LaTeX 2e. Plenary talk at the
Conference of RAS Nuclear Physics Department 2000 in ITEP, Moscow, Russia; to
appear in Phys. Atom. Nuc
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