Publications (117) View all
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Dataset: prl 105 102001
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Dataset: prl 91 012003
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Article: Substructures from weak interactions in light of possible threshold signals at LEP and LHC
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ABSTRACT: We present indications of possible substructures from weak interactions, by inspecting LEP and LHC date and inferring threshold effects due to the production of pairs of composite heavy gauge bosons W+-, Z and their hypothetical partners with different spin. Thus, we find possible evidence of scalar or pseudoscalar partners of the W+- and the Z, viz. at 53 and 57 GeV, respectively. Additionally, data may indicate excited states of the Z at 210 and 240 GeV.04/2013; -
Article: X(3872) is not a true molecule
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ABSTRACT: The wave function of the charmonium-like meson X(3872) is expected to have a very significant $D^0\bar{D}^{*0}$ component, as the latter threshold lies only 0.16 MeV above the meson's mass. Some conclude from this mass coincidence that X(3872) is a meson-meson molecule, whatever the dynamics giving rise to the state. This would imply that the $D^0\bar{D}^{*0}$ component of the X(3872) wave function is the only relevant one. In the present paper we study this issue by employing a soluble model for a $^3P_1$ $c\bar{c}$ state coupled to an S-wave $D^0\bar{D}^{*0}$ decay channel, communicating via the $^3P_0$ mechanism. The model is a simplified, coordinate-space version of the resonance-spectrum expansion previously employed in a detailed investigation of X(3872)'s nature. The resulting two-component wave function is calculated for different values of the binding energy (BE) and the transition radius $a$. Thus, a significant $c\bar{c}$ component is found in all situations. However, the long tail of the $D^0\bar{D}^{*0}$ wave function, in the case of small BEs, strongly limits the $c\bar{c}$ probability, which roughly lies in the range 7-11%, for the true BE of 0.16 MeV and $a$ between 2 and 3 GeV$^{-1}$. Furthermore, a reasonable value of 7.8 fm is obtained for the X(3872) r.m.s. radius at the physical mass, as well as an S-wave $D^0\bar{D}^{*0}$ scattering length of 11.6 fm. Finally, the S-matrix pole trajectories as a function of coupling constant show that X(3872) can be generated either as a dynamical pole or as one connected to the bare $c\bar{c}$ confinement spectrum, depending on details of the model. From these results we conclude that X(3872) is not a genuine meson-meson molecule, nor actually any other mesonic system with non-exotic quantum numbers, due to the inevitable mixing with the corresponding quark-antiquark states.12/2012; -
Article: Meson spectroscopy: too much excitement and too few excitations
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ABSTRACT: We briefly review the general status of meson spectroscopy, especially in light of the often made claim that there are too many observed resonances to be accounted for as $q\bar{q}$ states. Also, the adequacy of the usual Coulomb-plus-linear, alias "funnel", confining potential for reproducing the experimental spectra of light, heavy-light, and heavy mesons is critically analysed. Thus, many serious discrepancies are observed and discussed. As possible causes, we suggest the neglect of unitarisation and other coupled-channel effects, as well as the deficiency of the funnel potential itself. In order to illustrate our alternative, "unquenched" approach, we present some recent examples of successfully described puzzling mesonic enhancements and resonances, such as the charmonium states X(4260) and X(3872), as well as the axial-vector charmed mesons $D_1(2420)$, $D_1(2430)$, $D_{s1}(2536)$, and $D_{s1}(2460)$.09/2012;
