83 research outputs found
X(1576) as Diquark-Antidiquark Bound State
We propose that the broad resonance structure recently discovered by
BES in is the P-wave excitation of a
diquark-antidiquark bound state. This interpretation implies that there exists
a negative parity, vector nonet. A rough estimate of the mass spectrum of the
nonet is presented, and the prediction for the mass of X(1576) is consistent
with the experimental data. The OZI allowed strong decays are studied, it can
decay into two pseudoscalars or one pseudoscalar plus one vector meson. A
crucial prediction is that X(1576) should dominantly decay into ,
, . Since the isospin of X(1576) is , the
observation of or states which predominantly decays into
strange mesons could provide another important test to our proposal. To search
the charged isospin partner associated with X(1576) in , , , is suggested.Comment: 15 pages, 1 figur
Chromomagnetism, flavour symmetry breaking and S-wave tetraquarks
The chromomagnetic interaction, with full account for flavour-symmetry
breaking, is applied to S-wave configurations containing two quarks and two
antiquarks. Phenomenological implications are discussed for light, charmed,
charmed and strange, hidden-charm and double-charm mesons, and extended to
their analogues with beauty.Comment: 16 pages, 2 figures, RevTeX, Refs. updated, further typos corrected,
to appear in EPJ
Isovector and hidden-beauty partners of the X(3872)
The isovector partners of the X(3872), recently found at BES III, Belle and
CLEO-c were predicted in a simple model based on the chromomagnetic interaction
among quarks (H. Hogaasen, J-M. Richard and P. Sorba, Phys. Rev. D73, 054013,
2006). The extension to the hidden-beauty sector is discussed.Comment: Some references added. More details on the width and decay modes. To
appear in Phys. Lett.
Grozdovi obojenih s-valnih kvarkova s lomljenjem okusne simetrije
We study the properties of coloured three-particle s-wave quark clusters when flavour symmetry is broken. The relevance of such clusters for models of pentaquarks is shortly mentioned.ProuÄavamo svojstva obojenih troÄestiÄnih s-valnih kvarkovskih grozdova s lomljenjem okusne simetrije. Kratko se spominje vaĆŸnost tih grozdova za pentakvarkovske modele
Diquarks and antiquarks in exotics: a menage a trois and a menage a quatre
A menage a trois is very different from an ordinary family. Similarly, exotic
hadrons with both qq and qbar q pairs have important color-space correlations
that are completely absent in ordinary mesons and baryons. The presence of both
types of pairs requires attention to the basic QCD physics that the q qbar
interaction is much stronger than the qq interaction. This new physics in
multiquark systems produces color structures totally different from those of
normal hadrons, for example the ud system is utterly unlike the ud diquark in
the uds Lambda baryon. The color-space correlations produce unusual
experimental properties in tetraquarks with heavy quark pairs which may be
relevant for newly discovered mesons like the X(3872) resonance. Tetraquark
masses can be below the two-meson threshold for sufficiently high quark masses.
A simple model calculation shows the b q bbar ubar and b q cbar qbar
tetraquarks below the B Bbar and B Dbar thresholds. Some of these states have
exotic electric charge and their decays might have striking signatures
involving monoenergetic photons and/or pions.Comment: Journal version (PLB
Spectrum of the Y=2 Pentaquarks
By assuming a mass formula for the spectrum of the Y=2 pentaquarks, where the
chromo-magnetic interaction plays a main role, and identifying the lightest
state with the Theta^+(1540), we predict a spectrum in good agreement with the
few I=0 and I=1 candidates proposed in the past.Comment: 12 pages, 4 figures, LaTe
The discovery and properties of pentaquarks
The pentaquarks are exotic baryons formed of four quarks and an antiquarks.
Their existence has been discussed in the literature over the last 30 years or
more, first in connection with kaon nucleon scattering data. The subject has
been revived by the end of 2002 when experimental evidence of a narrow baryon
of strangeness = + 1, and mass 1530 MeV has been found. This is
interpreted as the lightest member of an SU(3)-flavor antidecuplet. Here we
shall mainly review the predictions of pentaquark properties as e.g. mass, spin
and parity, within constituent quark models.
Both light and heavy pentaquarks will be presented.Comment: Plenary talk, MESON2004 Conference Proceedings, Crakow, June 4-8 200
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