986 research outputs found
Transport properties of bottomed mesons in a hot mesonic gas
In this work we evaluate the B-meson drag and diffusion coefficients in a hot
medium constituted of light mesons (pions, kaons and eta mesons). We treat the
B-meson and B*-meson interaction with pseudo-Goldstone bosons in chiral
perturbation theory at next-to-leading order within the constraints from heavy
quark symmetry, and employ standard unitarization techniques of NLO amplitudes
in order to account for dynamically generated resonances (leading to a more
efficient heavy-flavor diffusion) and thus reach higher temperatures. We
estimate individual meson contributions from the gas to the transport
coefficients and perform a comparison with other findings in literature. We
report a bottom relaxation length of about 80 fm at a temperature of 150 MeV
and for typical momenta of 1 GeV, at which our approach is reliable. Compared
to a charm relaxation length of 40 fm in the same conditions, we conclude that
the B mesons provide a cleaner probe of the early stages of a heavy-ion
collision.Comment: 14 pages, 16 figures, 3 tables. Version published in Phys.Rev.D87,
034019 (2013). Only minor improvements with respect to v1: corrected typos,
further clarifications and updated reference
Heavy mesons in a hadronic medium: interaction and transport coefficients
We review the recent results of heavy meson diffusion in thermal hadronic
matter. The interactions of D and B-bar mesons with other hadrons (light mesons
and baryons) are extracted from effective field theories based on chiral and
heavy-quark symmetries. When these guiding principles are combined with exact
unitarity, physical values of the cross sections are obtained. These cross
sections (which contain resonant contributions) are used to calculate the drag
and diffusion coefficients of heavy mesons immersed in a thermal and dense
medium. The transport coefficients are computed using a Fokker-Planck reduction
of the Boltzmann equation.Comment: 4 pages, 3 figures. Contribution to the proceedings of the 15th
International Conference on Strangeness in Quark Matter (SQM 2015), 06-11 Jul
2015. Dubna, Moscow region, Russi
D-meson diffusion in hadronic matter
We present effective-field-theory results with unitarized interactions on the
D-meson transport coefficients in a gas populated by light mesons and baryons
at finite temperature and baryochemical potential. The Fokker-Planck equation
is used to compute the drag force, the relaxation time and the diffusion
coefficients of D mesons for collisions at FAIR. At finite baryochemical
potential, the combined effect of net baryonic density and sizable meson-baryon
interaction makes the D mesons to relax more efficiently than in the case at
zero baryochemical potential. We also describe the connection with the
quark-gluon plasma phase in adiabatic trajectories on the phase diagram at both
zero and finite baryochemical potential.Comment: 5 pages, 4 figures. Contribution to the FAIRNESS 2013 - Workshop for
young scientists with research interests focused on FAIR physics. 15-21
September 2013, Berlin (Germany
Heating triangle singularities in heavy ion collisions
We predict that triangle singularities of hadron spectroscopy are strongly
affected in heavy ion collisions. To do it we examine various effects of finite
temperature on the triangle loop yielding the singularity within the hadron
phase. Pion-containing triangles can be enhanced by exchanging them with the
medium, but in other cases, especially with heavy-quark hadrons, known thermal
effects over the particles mass and width can quickly reduce the singularity:
at temperatures of about 150 MeV, below the transition to a quark-gluon plasma,
even by two orders of magnitude. It appears that peaks seen in central heavy
ion collisions are more likely to be hadrons than rescattering effects unless
perhaps if a pion is involved in the triangle. The medium then acts as a
spectroscopic filter.Comment: 5 pages, 7 plot
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
Traces of the new resonance in the reaction
We study the decay, looking for differences in the
production rates of or in the region of 1700-1800 MeV,
where two resonances appear dynamically generated from the vector-vector
interaction. Two resonances are known experimentally in that region, the
and a new resonance reported by the BABAR and BESIII
collaborations. The should be produced with in that reaction,
but due to the different and masses some isospin violation
appears. Yet, due to the large width of the , the violation obtained is
very small and the rates of or production are equal
within . However, we also find that due to the step needed to convert two
vectors into , a shape can appear in the mass distribution
that can mimic the production around the threshold, and is
simply a threshold effect.Comment: 13 pages; 11 figure
Inverse magnetic catalysis and size-dependent effects on the chiral symmetry restoration
We investigate the combined finite-size and thermo-magnetic effects on the
properties of the quark matter, in the context of the two-flavored
Nambu--Jona-Lasinio model. In particular, by using the mean-field approximation
and the Schwinger proper time method in a toroidal topology with periodic or
antiperiodic conditions, we evaluate the chiral phase transition, the
constituent quark mass and the thermal and spatial susceptibilities under the
change of the size, temperature and strength of external magnetic field. To
take into account the inverse magnetic catalysis phenomenon, we make use of a
recently proposed magnetized coupling constant. The findings suggest that the
observables are strongly affected by the variation of the variables and also by
the periodicity of the boundary conditions, with the final outcomes depending
on the balance of these competing phenomena.Comment: 21 pages, 7 figure
A note on the tensor and vector exchange contributions to and reactions
In this note we study the tensor and vector exchange contributions to the
elastic reactions involving the pseudoscalars mesons ,
and . In the case of the tensor-exchange contributions
we assume that an intermediate tensor is dynamically generated from
the interaction of two virtual mesons, with the use of a pole
approximation. The calculation of the two-loop amplitude is facilitated since
the triangle loops can be factorized and computed separately. The results show
very small contributions coming from the tensor-exchange mechanisms when
compared with those from the vector-exchange processes.Comment: 8 pages, 5 figure
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