6,390 research outputs found
Hadronic and radiative three-body decays of J/psi involving the scalars f0(1370), f0(1500) and f0(1710)
We study the role of the scalar resonances f0(1370), f0(1500) and f0(1710) in
the strong and radiative three-body decays of J/psi with J/psi to V + P P
(gamma gamma) and J/psi to gamma + P P (V V), where P (V) denotes a
pseudoscalar (vector) meson. We assume that the scalars result from a
glueball-quarkonium mixing scheme while the dynamics of the transition process
is described in an effective chiral Lagrangian approach. Present data on J/psi
to V + P P are well reproduced, predictions for the radiative processes serve
as further tests of this scenario.Comment: 15 page
Colloids dragged through a polymer solution: experiment, theory and simulation
We present micro-rheological measurments of the drag force on colloids pulled
through a solution of lambda-DNA (used here as a monodisperse model polymer)
with an optical tweezer. The experiments show a violation of the
Stokes-Einstein relation based on the independently measured viscosity of the
DNA solution: the drag force is larger than expected. We attribute this to the
accumulation of DNA infront of the colloid and the reduced DNA density behind
the colloid. This hypothesis is corroborated by a simple drift-diffusion model
for the DNA molecules, which reproduces the experimental data surprisingly
well, as well as by corresponding Brownian dynamics simulations.Comment: 9 pages, 13 figures, 3 table
B_s(d) - bar B_s(d) mixing constraints on flavor changing decays of t and b quarks
We study those dimension 6 effective operators which generate flavor-changing
quark-gluon transitions of the third generation quarks, with t -> g + u(c) and
b -> g + d(s), and which could be of interest for LHC experiments. We analyze
the contribution of these operators to B_s(d) - bar B_s(d) mixing and derive
limits on the corresponding effective couplings from the existing experimental
data. The Standard Model gauge invariance relates these couplings to the
couplings controlling t -> g + u(c). On this basis we derive upper limits for
the branching ratios of these processes. We further show that forthcoming LHC
experiments might be able to probe the studied operators and the physics beyond
the Standard Model related to them.Comment: 6 pages, 1 figur
Relativistic structure of one-meson and one-gluon exchange forces and the lower excitation spectrum of the Nucleon and the Delta
The lower excitation spectrum of the nucleon and is calculated in a
relativistic chiral quark model. Corrections to the baryon mass spectrum from
the second order self-energy and exchange diagrams induced by pion and gluon
fields are estimated in the field -theoretical framework. Convergent results
for the self-energy terms are obtained when including the intermediate quark
and antiquark states with a total momentum up to . Relativistic
one-meson and color-magnetic one-gluon exchange forces are shown to generate
spin 0, 1, 2, etc. operators, which couple the lower and the upper components
of the two interacting valence quarks and yield reasonable matrix elements for
the lower excitation spectrum of the Nucleon and Delta. The only contribution
to the ground state nucleon and comes from the spin 1 operators, which
correspond to the exchanged pion or gluon in the l=1 orbit, thus indicating,
that the both pion exchange and color-magnetic gluon exchange forces can
contribute to the spin of baryons. Is is shown also that the contribution of
the color-electric component of the gluon fields to the baryon spectrum is
enormously large (more than 500 MeV with a value ) and one needs
to restrict to very small values of the strong coupling constant or to exclude
completely the gluon-loop corrections to the baryon spectrum. With this
restriction, the calculated spectrum reproduces the main properties of the
data, however needs further contribution from the two-pion exchange and
instanton induced exchange (for the nucleon sector) forces in consistence with
the realistic NN-interaction models.Comment: 15 pages, 4 figures, 7 table
Video reflectometry to specify optical properties of tissue in vivo
The measurement of tissue optical properties is often required for proper design of therapeutic or diagnostic uses of light in medicine. The ability of light to spread into a tissue and the rate of light absorption by the tissue are two related but distinct processes. The two independent optical parameters which affect these processes are absorption and scattering. To understand light propagation, two independent optical measurements must be made. In this paper, we discuss the measurements of total diffuse reflectance and lateral spread of light in response to a point source of irradiance. In this paper, we call this technique 'video reflectometry'. The video reflectometry technique is a noncontact measurement. Therefore, it can be used with living tissues with their in situ water balance and blood content. The technique includes two measurements: (1) a photodiode measurement of total diffuse reflectance, R_d, and (2) a video camera measurement of the lateral spread of light in the tissue which is expressed as the local diffuse reflectance, R(r). Although it is possible to obtain the value of R_d from the integration of the video R(r) data, the independent photodiode measurement of R_d is more reliable and more easily calibrated. Therefore, we employ the two methods in video reflectometry
Strong and Electromagnetic Decays of X(1835) as a Baryonium State
With the assumption that the recently observed X(1835) is a baryonium state
we have studied the strong decays of and the electromagnetic decay of in the framework of effective Lagrangian formalism. In the present
investigation we have included the contributions from the iso-singlet light
scalar resonances but we have not included the isospin violating effect. Our
result for the strong decay of is
smaller than the observed data. The decay width for the radiative decay of
is consistent with the assumption that it decays through
the glueball. In addition, the width for the strong decay of is larger than that of the strong decay of due to the large phase space and coupling constant
. From our investigation, it is not possible to interpret
X(1835) as a baryonium.Comment: Corrected typo
Light baryon magnetic moments and N -> Delta gamma transition in a Lorentz covariant chiral quark approach
We calculate magnetic moments of light baryons and N -> Delta gamma
transition characteristics using a manifestly Lorentz covariant chiral quark
approach for the study of baryons as bound states of constituent quarks dressed
by a cloud of pseudoscalar mesons.Comment: 29 pages, 10 figures, accepted for publication in Phys. Rev.
- …