3,027 research outputs found
The Z(4430) and a New Paradigm for Spin Interactions in Tetraquarks
Following the recent confirmation of the Z+(4430) resonance with
J^{PG}=1^{++}, we have re-examined the model of S- and P-wave tetraquarks. We
propose a `type-II' diquark-antidiquark model which shows to be very effective
at producing a simple and comprehensive picture of the J^{PG}=1^{++} and 1^{--}
sectors of the recently discovered charged tetraquarks and of the observed Y
resonances. The model is still faced with the unresolved difficulty of
explaining why some states seem to have incomplete isospin multiplets.Comment: 17 pages, 1 figure, comments added, typos corrected, to appear in
Phys Rev
Four-Quark Mesons
The features of a model interpreting the light scalar mesons as
diquark-antidiquark bound states and the consequences of its natural extension
to include heavy quarks are briefly reviewed.Comment: Talk given at the 6th Conference on Quark Confinement and the Hadron
Spectrum, Villasimius, Sardinia, Italy, 21-25 Sep 200
Four Quark Interpretation of Y(4260)
We propose that the Y(4260) particle recently announced by BaBar is the first
orbital excitation of a diquark-antidiquark state ([cs][cbar sbar]). Using
parameters recently determined to describe the X(3872) and X(3940) we show that
the Y mass is compatible with the orbital excitation picture. A crucial
prediction is that Y(4260) should decay predominantly in D_s D_sbar. The
Y(4260) should also be seen in B non-leptonic decays in association with one
kaon. We consider the full nonet of related four-quark states and their
predicted properties. Finally, we comment on a possible narrow resonance in the
same channel.Comment: 3 pages, 2 figures, RevTex, Revised discussion of the Y mas
UTOPIAS AND DYSTOPIAS IN LANDSCAPE AND CULTURAL MOSAIC. VISIONS, VALUES, VULNERABILITY: AN INTRODUCTION
How much is it worth for whom? How long will be worth for?
We must not be scared off by mythical names such as the City of the Sun,
Utopia, New Atlantis, and we must not give in to the chanting of their
Mermaids. Let\u2019s start from Friedman and his definition of urban utopia and
dystopia: \u201cutopian thinking: the capacity to imagine a future that departs
significantly from what we know to be a general condition of the present.\u2026In
the peculiar form of dystopias, utopian thinking may alert us to certain
tendencies in the present, which, if allowed to continue unchecked and carried
to a logical extreme, would result in a world we would find abhorrent\u201d.
Emphasis will not be placed on the urban utopias of the perfect city since this
field has been widely and finely explored by urban planners and architects. It
was, after all, the first topic that was dealt with by many utopians in their
description of their little perfect worlds. Rather, we want to explore the abstract
spatial forms of utopia and dystopias. The term dystopia is not only used to refer
to the extreme consequences of the mistakes of mankind, but also to the
conflicts arising from different utopias and particularly between utopias and the
real world. Such conflicts will enable us to consider spatial forms in their
temporal development, not only as a starting and finishing point but also as a
process having intermediate phases that are often concealed by the saying \u201cthe
ends justify the means\u201d.
The age-old dystopia between city and countryside must be overcome. Border
areas have never been well defined and are formed by the combination of
numerous tesserae that, at times, are juxtaposed like proper mosaic tesserae, and
at times represent mixed areas where the single components become blurred and
indistinguishable. One\u2019s desire to classify and separate must give way to the
analysis of merging, dissolution and enlargement of borders, just like Gottman
did in his much praised (but also criticised) Megalopolis
The observation of light nuclei at ALICE and the X(3872) conundrum
The new data reported by ALICE on the production of light nuclei with pT < 10
GeV in Pb-Pb collisions at sqrt(s_NN) = 2.76 TeV are used to compute an
order-of-magnitude estimate of the expected production cross sections of light
nuclei in proton-proton collisions at high transverse momenta. We compare the
hypertriton, helium-3 and deuteron production cross sections to that of
X(3872), measured in prompt pp collisions by CMS. The results we find suggest a
different production mechanism for the X(3872), making questionable any loosely
bound molecule interpretation.Comment: 5 pages, 2 figures. Version accepted on PR
Is the anomalous decay ratio of D_{sJ}(2632) due to isospin breaking?
Quark pair annihilation into gluons is suppressed at large momenta due to the
asymptotic freedom. As a consequence, mass eigenvalues of heavy states should
be almost diagonal with respect to up and down quark masses, thereby breaking
isospin. We suggest the particle observed by the SELEX Collaboration,
D_{sJ}(2632) to be to a good extent a [cd][dbar sbar] state, which would
explain why its D^0 K^+ mode is anomalously suppressed with respect to D_s eta.
Predictions for the rates of the yet unobserved modes D_s pi^0 and D^+ K^0 are
given.Comment: 3 pages, 1 figur
Four-Quark Mesons in Non-leptonic B Decays--Could They Resolve Some Old Puzzles?
We point out that non-leptonic B decays driven by b-->ccbar s should provide
a favourable environment for the production of hidden charm diquark-antidiquark
bound states that have been suggested to explain the resonances with masses
around 4 GeV recently observed by BaBar and BELLE. Studying their relative
abundances in non-leptonic B decays can teach us novel lessons about their
structure and the strong interactions. Through their decay into psi they can
provide a natural explanation of the excess of B-->psi X observed for p_psi < 1
GeV. Other phenomenological consequences are mentioned as well.Comment: 6 pages, 2 figures, revte
Comment on `Note on X(3872) production at hadron colliders and its molecular structure'
We briefly comment on the paper by Albaladejo et al. [arXiv:1709.09101],
rejecting its conclusions.Comment: This paper was prepared at the request of a journal editor. 3 Pages,
no figure
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