1,485 research outputs found
Relation between and from QCD
We have studied, using double ratio of QCD (spectral) sum rules, the ratio
between the masses of and X(3872) assuming that they are respectively
described by the and molecular currents. We found
(within our approximation) that the masses of these two states are almost
degenerate. Since the pion exchange interaction between these mesons is exactly
the same, we conclude that if the observed X(3872) meson is a
molecule, then the molecule should also exist with approximately the
same mass. An extension of the analysis to the -quark case leads to the same
conclusion. We also study the SU(3) breakings for the mass
ratios. Motivated by the recent Belle observation of two states, we
revise our determination of by combining results from exponential and
FESR sum rules.Comment: revised version to appear on Phys. Lett.
Self-bound Interacting QCD Matter in Compact Stars
The quark gluon plasma (QGP) at zero temperature and high baryon number is a
system that may be present inside compact stars. It is quite possible that this
cold QGP shares some relevant features with the hot QGP observed in heavy ion
collisions, being also a strongly interacting system. In a previous work we
have derived from the QCD Lagrangian an equation of state (EOS) for the cold
QGP, which can be considered an improved version of the MIT bag model EOS.
Compared to the latter, our equation of state reaches higher values of the
pressure at comparable baryon densities. This feature is due to perturbative
corrections and also to non-perturbative effects. Here we apply this EOS to the
study of neutron stars, discussing the absolute stability of quark matter and
computing the mass-radius relation for self-bound (strange) stars. The maximum
masses of the sequences exceed two solar masses, in agreement with the recently
measured values of the mass of the pulsar PSR J1614-2230, and the corresponding
radii around 10-11 km
Virtual Meson Cloud of the Nucleon and Intrinsic Strangeness and Charm
We have applied the Meson Cloud Model (MCM) to calculate the charm and
strange antiquark distribution in the nucleon. The resulting distribution, in
the case of charm, is very similar to the intrinsic charm momentum distribution
in the nucleon. This seems to corroborate the hypothesis that the intrinsic
charm is in the cloud and, at the same time, explains why other calculations
with the MCM involving strange quark distributions fail in reproducing the low
x region data. From the intrinsic strange distribution in the nucleon we have
extracted the strangeness radius of the nucleon, which is in agreement with
other meson cloud calculations.Comment: 9 pages RevTex, 4 figure
Heavy quark & direct photon production and heavy quark parton densities
Direct photon production in association with a heavy quark can serve as an
excellent tool for the study of the heavy quark distributions. Currently it is
believed that heavy quarks are produced radiatively inside the nucleon, and so
there is no need to take into account heavy quark parameters inside global PDF
analyses. Certain models taking into account the possibility of an intrinsic
charm component exist. Here we present how these affect the \gamma + c cross
section. While at pA collisions the potential of this process to constrain the
gluon nuclear PDF which is currently largely unconstrained is presented.Comment: Quarkonium 2010 Proceeding
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