596 research outputs found
On the mass of the Ds(0+,1+) system
In this note we discuss a determination for the mass of the Ds(0+,1+) system
recently discovered by the BaBar, CLEO II and Belle Collaborations. The value
of the mass is derived by making explicit the prediction obtained in a
quark-meson model prior to the discovery of these states.Comment: 3 pages, revte
Superfluid and Pseudo-Goldstone Modes in Three Flavor Crystalline Color Superconductivity
We study the bosonic excitations in the favorite cubic three flavor
crystalline LOFF phases of QCD. We calculate in the Ginzburg-Landau
approximation the masses of the eight pseudo Nambu-Goldstone Bosons (NGB)
present in the low energy theory. We also compute the decay constants of the
massless NGB Goldstones associated to superfluidity as well as those of the
eight pseudo NGB. Differently from the corresponding situation in the
Color-Flavor-Locking phase, we find that meson condensation phases are not
expected in the present scenario.Comment: 10 pages, RevTeX4 class. Section IIIA enlarged, to appear on Phys.
Rev.
The s-sbar and K-Kbar nature of f_0(980) in D_s decays
We examine the D_s -> f_0(980) pi amplitude through a constituent quark-meson
model, incorporating heavy quark and chiral symmetries, finding a good
agreement with the recent E791 data analysis of D_s -> 3pi via f_0(980). The
f_0(980) resonance is considered at the moment of production as an s sbar
state, later evolving to a superposition of mainly s sbar and K Kbar. The
analysis is also extended to the more frequent process D_s -> phi pi.Comment: 8 pages, 5 figure
Evaluating the phase diagram of superconductors with asymmetric spin populations
The phase diagram of a non-relativistic fermionic system with imbalanced
state populations interacting via a short-range S-wave attractive interaction
is analyzed in the mean field approximation. We determine the energetically
favored state for different values of the mismatch between the two Fermi
spheres in the weak and strong coupling regime considering both homogeneous and
non-homogeneous superconductive states. We find that the homogeneous
superconductive phase persists for values of the population imbalance that
increase with increasing coupling strength. In the strong coupling regime and
for large population differences the energetically stable homogeneous phase is
characterized by one gapless mode. We also find that the inhomogeneous
superconductive phase characterized by the condensate is energetically favored in a range of values
of the chemical potential mismatch that shrinks to zero in the strong coupling
regime.Comment: 9 pages, 5 figure
A Note on the J/psi Strong Couplings
In this note we present an evaluation of the couplings JD(*)D(*) and
JD(*)D(*)pi in the Constituent Quark Model. These couplings are a crucial
ingredient in the calculation of cross sections for the processes pi J/psi ->
D(*)Dbar(*), an important background for the J/psi suppression signal in
quark-gluon plasma.Comment: 7 pages, LaTeX, 4 figures, in Workshop on Hard Probes in Heavy Ion
Collisions at the LH
Neutrino emission from compact stars and inhomogeneous color superconductivity
We discuss specific heat and neutrino emissivity due to direct Urca processes
for quark matter in the color superconductive Larkin-Ovchinnikov-Fulde-Ferrell
(LOFF) phase of Quantum-Chromodynamics. We assume that the three light quarks
are in a color and electrically neutral state and interact by a four
fermion Nambu-Jona Lasinio coupling. We study a LOFF state characterized by a
single plane wave for each pairing. From the evaluation of neutrino emissivity
and fermionic specific heat, the cooling rate of simplified models of compact
stars with a quark core in the LOFF state is estimated.Comment: 16 pages, 5 figures, revtex4 style. Version accepted for publication
in Phys. Rev.
Effective Lagrangian for Heavy and Light Mesons: Semileptonic Decays
We introduce an effective lagrangian including negative and positive parity
heavy mesons containing a heavy quark, light pseudoscalars, and light vector
resonances, with their allowed interactions, using heavy quark spin-flavour
symmetry, chiral symmetry, and the hidden symmetry approach for light vector
resonances. On the basis of such a lagrangian, by considering the allowed weak
currents and by including the contributions from the nearest unitarity poles we
calculate the form factors for semileptonic decays of and mesons into
light pseudoscalars and light vector resonances. The available data, together
with some additional assumptions, allow for a set of predictions in the
different semileptonic channels, which can be compared with those following
{}from different approaches. A discussion of non-dominant terms in our
approach, which attempts at including a rather complete dynamics, will however
have to wait till more abundant data become available.Comment: LaTeX (style article), 19 pages, UGVA-DPT 1992/11-790, BARI-TH/92-12
Semileptonic and Rare -meson transitions in a QCD relativistic potential model
Using a QCD relativistic potential model, previously applied to the
calculation of the heavy meson leptonic constants, we evaluate the form factors
governing the exclusive decays , and . In our approach the heavy meson is described as a
bound state, whose wave function is solution of the relativistic Salpeter
equation, with an instantaneous potential displaying Coulombic behaviour at
small distances and linear behaviour at large distances. The light vector meson
is described by using a vector current interpolating field, according to the
Vector Meson Dominance assumption. A Pauli-Villars regularized propagator is
assumed for the quarks not constituting the heavy meson. Our procedure allows
to avoid the description of the light meson in terms of wave function and
constituent quarks, and consequently the problem of boosting the light meson
wave function.
Assuming as an input the experimental results on , we
evaluate all the form factors describing the semileptonic and
rare transitions. The overall comparison with the data, whenever available, is
satisfactory.Comment: Latex, 19 pages, 3 figure
On the ground state of gapless two flavor color superconductors
This paper is devoted to the study of some aspects of the instability of two
flavor color superconductive quark matter. We find that, beside color
condensates, the Goldstone boson related to the breaking of suffers of
a velocity instability. We relate this wrong sign problem, which implies the
existence of a Goldstone current in the ground state or of gluonic
condensation, to the negative squared Meissner mass of the gluon in
the g2SC phase. Moreover we investigate the Meissner masses of the gluons and
the squared velocity of the Goldstone in the multiple plane wave LOFF states,
arguing that in such phases both the chromo-magnetic instability and the
velocity instability are most probably removed. We also do not expect Higgs
instability in such multiple plane wave LOFF. The true vacuum of gapless two
flavor superconductors is thus expected to be a multiple plane wave LOFF state.Comment: 16 pages, RevTe3X4 styl
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