76 research outputs found
The doubly heavy baryons
We present the results for the masses of the doubly heavy baryons
and where obtained in the framework of the simple
approximation within the nonperturbative string approach.Comment: 4 pages, 1 EPS fig., using espcrc2.sty package. Talk presented by
I.M.Narodetskii at the 5th International Conference on Hyperon, Charm and
Beauty Hadrons, Vancouver, Canada, June 200
Spectroscopy of Baryons Containing Two Heavy Quarks in Nonperturbative Quark Dynamics
We have studied the three quark systems in an Effective Hamiltonian approach
in QCD. With only two parameters: the string tension sigma and the strong
coupling constant alpha_s we obtain a good description of the ground state
light and heavy baryons. The prediction of masses of the doubly heavy baryons
not discovered yet are also given. In particular, a mass of 3620 MeV for the
lightest (ccu) baryon is found by employing the hyperspherical formalism to the
three quark confining potential with the string junction.Comment: 8 pages, LaTe
QCD string in light-light and heavy-light mesons
The spectra of light-light and heavy-light mesons are calculated within the
framework of the QCD string model, which is derived from QCD in the Wilson loop
approach. Special attention is payed to the proper string dynamics that allows
us to reproduce the straight-line Regge trajectories with the inverse slope
being 2\pi\sigma for light-light and twice as small for heavy-light mesons. We
use the model of the rotating QCD string with quarks at the ends to calculate
the masses of several light-light mesons lying on the lowest Regge trajectories
and compare them with the experimental data as well as with the predictions of
other models. The masses of several low-lying orbitally and radially excited
heavy--light states in the D, D_s, B, and B_s meson spectra are calculated in
the einbein (auxiliary) field approach, which has proven to be rather accurate
in various calculations for relativistic systems. The results for the spectra
are compared with the experimental and recent lattice data. It is demonstrated
that an account of the proper string dynamics encoded in the so-called string
correction to the interquark interaction leads to an extra negative
contribution to the masses of orbitally excited states that resolves the
problem of the identification of the D(2637) state recently claimed by the
DELPHI Collaboration. For the heavy-light system we extract the constants
\bar\Lambda, \lambda_1, and \lambda_2 used in Heavy Quark Effective Theory
(HQET) and find good agreement with the results of other approaches.Comment: RevTeX, 42 pages, 7 tables, 7 EPS figures, uses epsfig.sty, typos
corrected, to appear in Phys.Rev.
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
Nonperturbative corrections to the quark self-energy
Nonperturbative self-energy of a bound quark is computed gauge-invariantly in
the framework of background perturbation theory. The resulting Delta m^2_q is
negative and is a universal function of string tension and current quark mass.
The shift of hadron mass squared, M^2, due to Delta m^2_q is negative, large
for light quarks, and solves the long-standing problem of Regge intercepts in
relativistic quark models.Comment: LaTeX2e, 13 pages, minor differences are don
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
Baryon magnetic moments in the QCD string approach
Magnetic moments of baryons composed of light and strange quarks are computed
for the first time through the only parameter of the model -- string tension
. Resulting theoretical values differ from the experimental ones
typically by about
10%.Comment: LaTeX, 13 pages; misprints are correcte
Analytic calculation of field-strength correlators
Field correlators are expressed using background field formalism through the
gluelump Green's functions. The latter are obtained in the path integral and
Hamiltonian formalism. As a result behaviour of field correlators is obtained
at small and large distances both for perturbative and nonperturbative parts.
The latter decay exponentially at large distances and are finite at x=0, in
agreement with OPE and lattice data.Comment: 28 pages, no figures; new material added, misprints correcte
Accuracy of Auxiliary Field Approach for Baryons
We provide a check of the accuracy of the auxiliary field formalism used to
derive the Effective Hamiltonian for baryons in the Field Correlator Method. To
this end we compare the solutions for the Effective Hamiltonian with those
obtained from the solution of the Salpeter equation. Comparing these results
gives a first estimate of the systematic uncertainty due to the use of the
auxiliary field formalism for baryons.Comment: 6 pages, 2 tables; published versio
Structural basis of nucleosome assembly by the Abo1 AAA+ ATPase histone chaperone
The fundamental unit of chromatin, the nucleosome, is an intricate structure that requires histone chaperones for assembly. ATAD2 AAA+???ATPases are a family of histone chaperones that regulate nucleosome density and chromatin dynamics. Here, we demonstrate that the fission yeast ATAD2 homolog, Abo1, deposits histone H3???H4 onto DNA in an ATP-hydrolysis-dependent manner by in vitro reconstitution and single-tethered DNA curtain assays. We present cryo-EM structures of an ATAD2 family ATPase to atomic resolution in three different nucleotide states, revealing unique structural features required for histone loading on DNA, and directly visualize the transitions of Abo1 from an asymmetric spiral (ATP-state) to a symmetric ring (ADP- and apo-states) using high-speed atomic force microscopy (HS-AFM). Furthermore, we find that the acidic pore of ATP-Abo1 binds a peptide substrate which is suggestive of a histone tail. Based on these results, we propose a model whereby Abo1 facilitates H3???H4 loading by utilizing ATP
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