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

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

A new look at scalar mesons

Light scalar mesons are found to fit rather well a diquark-antidiquark description. The resulting nonet obeys mass formulae which respect, to a good extent, the OZI rule. OZI allowed strong decays are reasonably reproduced by a single amplitude describing the switch of a qbar-q pair, which transforms the state into two colourless pseudoscalar mesons. Predicted heavy states with one or more quarks replaced by charm or beauty are briefly described; they should give rise to narrow states with exotic quantum numbers.Comment: 4 pages, 1 figure, misprints corrected, references added, accepted for publication in Phys. Rev. Let