65 research outputs found
Semileptonic decay of into , ,
We study the semileptonic decay of meson into and
the isospin zero , ,
resonances. We look at the reaction from the perspective that these resonaces
appear as dynamically generated from the vector-vector interaction in the charm
sector, and couple strongly to and
. We also look into the and reactions close to threshold and relate the
and mass distribution to the rate
of production of the resonances.Comment: 7 pages, 9 figure
Collision integral with momentum-dependent potentials and its impact on pion production in heavy-ion collisions
The momentum dependence of the nucleon mean-field potential in a wide
momentum range can be an important factor to determine the resonance
and pion production in intermediate-energy heavy-ion collisions. In particular,
in neutron-rich systems such as
collisions, we need to carefully treat the momentum dependence because the
neutron and proton potentials can have different momentum dependence, as
characterized at low momenta by effective masses. In the present work, we
rigorously calculate the collision terms of and
processes with the precise conservation of
energy and momentum under the presence of momentum-dependent potentials for the
initial and final particles of the process. The potentials affect not only the
threshold condition for the process but also the cross section in general as a
function of the momenta of the initial particles, which is treated in a natural
way in the present work. Calculations are performed by combining the nucleon
dynamics obtained by the antisymmetrized molecular dynamics (AMD) model with a
newly developed transport code which we call sJAM. The calculated results for
central collisions at 270 MeV/nucleon
clearly show that the momentum dependence of the neutron and proton potentials
has a significant impact on the process, and this information
is strongly reflected in the charged pion ratio (). We also
investigate the effects of the high-density symmetry energy and the isovector
part of the potential of resonances on pion production, which we find
are relatively small compared to the effect of the momentum dependence of the
neutron and proton potentials.Comment: 18 pages, 13 figures, 1 tabl
Probing neutron-proton dynamics by pions
In order to investigate the nuclear symmetry energy at high density, we study
the pion production in central collisions of neutron-rich nuclei
at 300 MeV/nucleon using a new
approach by combining the antisymmetrized molecular dynamics (AMD) and a
hadronic cascade model (JAM). The dynamics of neutrons and protons is solved by
AMD, and then pions and resonances in the reaction process are handled
by JAM. We see the mechanism how the resonance and pions are produced
reflecting the dynamics of neutrons and protons. We also investigate the
impacts of cluster correlations as well as of the high-density symmetry energy
on the nucleon dynamics and consequently on the pion ratio. We find that the
production ratio agrees very well with the
neutron-proton squared ratio in the high-density and high-momentum
region. We show quantitatively that production ratio, and therefore
, are directly reflected in the ratio, with modification
in the final stage of the reaction.Comment: 14 pages, 10 figures; Figures 3-8 are updated with corrected
numerical results. No change in the main conclusion
meson under partial restoration of chiral symmetry in nuclear medium
In-medium modification of the eta' mass is discussed in the context of
partial restoration of chiral symmetry in nuclear medium. We emphasize that the
U_A(1) anomaly effects causes the eta'-eta mass difference necessarily through
the chiral symmetry breaking. As a consequence, the eta' mass is expected to be
reduced by order of 100 MeV in nuclear matter where about 30% reduction of
chiral symmetry takes place. The strong attraction relating to the eta' mass
generation eventually implies that there should be also a strong attractive
interaction in the scalar channel of the eta'-N two-body system. We find that
the attraction can be strong enough to form a bound state.Comment: 4 pages, 3 figures. Talk given at the XI International Conference on
Hypernuclear and Strange Particle Physics (HYP2012), Oct. 1-5, 2012,
Barcelona, Spain. Accepted version. Some typos were correcte
Theoretical study of the reaction
We develop a model to study the weak decay, starting
with the color favored external emission and Cabibbo favored mode at the quark
level. A less favored internal emission decay mode is also studied as a source
of small corrections. Some pairs of quarks are allowed to hadronize producing
two pseudoscalar mesons, which posteriorly are allowed to interact to finally
provide the state. The chiral unitary approach is used to take
into account the final state interaction of pairs of mesons, which has as a
consequence the production of the () and the
resonances, very well visible in the invariant mass distributions. We also
introduce the production in a phenomenological way and show
that the -wave pseudoscalar interaction together with this vector excitation
mode are sufficient to provide a fair reproduction of the experimental data.
The agreement with the data, in particular the relative weight of the
to the excitation, provides extra support to the picture
used, in which these two resonances are a consequence of the interaction of
pseudoscalar mesons and not ordinary mesons.Comment: 13 pages, 13 Figure
Role of and in the and reactions
In this work we study the role of the and resonances in
the low and invariant-mass region of the and reactions. The
amplitudes are calculated by using the chiral unitary formalism, in
which these two resonances are dynamically generated from the unitary
pseudocalar-pseudoscalar coupled-channel approach. The amplitudes are then used
as input in the evaluation of the mass distributions with respect to the and invariant-masses, where the contributions
coming from the and components are explicitly assessed.
Furthermore, the contribution of the production and
its influence on the and systems are also
evaluated, showing that there is no significant strength for small invariant mass. Lastly, the final distributions of for the reactions
are estimated and compared with the LHCb data. Our results indicate that the
component tied to the excitation generates the dominant
contribution in the range of low invariant-mass.Comment: 11 pages, 10 figure
- …