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Narrow exotic tetraquark mesons in large-N_c QCD

Hagop Sazdjian

Discussing four-point Green functions of bilinear quark currents in large-N_c QCD, we formulate rigorous criteria for selecting diagrams appropriate for the analysis of potential tetraquark poles. We find that both flavor-exotic and cryptoexotic (i.e., flavor-nonexotic) tetraquarks, if such poles exist, have a width of order O(1/N_c^2), so they are parametrically narrower compared to the ordinary mesons, which have a width of order O(1/N_c). Moreover, for flavor-exotic states, the (...)

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Delta(1232) Dalitz decay in proton-proton collisions at T=1.25 GeV measured with HADES at GSI

We report on the investigation of Δ(1232) production and decay in proton-proton collisions at a kinetic energy of 1.25 GeV measured with HADES. Exclusive dilepton decay channels ppe+e− and ppe+e−γ have been studied and compared with the partial-wave analysis of the hadronic ppπ0 channel. They allow to access both Δ+→pπ0(e+e−γ) and Δ+→pe+e− Dalitz decay channels. The perfect reconstruction of the well-known π0 Dalitz decay serves as a proof of the consistency of the analysis. The Δ Dalitz decay is (...)

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Lee-Yang–inspired functional with a density-dependent neutron-neutron scattering length

M. Grasso, D. Lacroix, and C. J. Yang

Inspired by the low-density Lee-Yang expansion for the energy of a dilute Fermi gas of density ρ and momentum kF, we introduce here a Skyrme-type functional that contains only s-wave terms and provides, at the mean-field level, (i) a satisfactory equation of state for neutron matter from extremely low densities up to densities close to the equilibrium point, and (ii) a good-quality equation of state for symmetric matter at density scales around (...)

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Renormalizability of the nuclear many-body problem with the Skyrme interaction beyond mean field

C. J. Yang, M. Grasso, K. Moghrabi, and U. van Kolck

Phenomenological effective interactions like Skyrme forces are currently used in mean-field calculations in nuclear physics. Mean-field models have strong analogies with the first order of the perturbative many-body problem and the currently used effective interactions are adjusted at the mean-field level. In this work, we analyze the renormalizability of the nuclear many-body problem in the case where the effective Skyrme interaction is employed in (...)

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Power counting in peripheral partial waves: The singlet channels

M. Pavón Valderrama, M. Sánchez Sánchez, C.-J. Yang, Bingwei Long, J. Carbonell, and U. van Kolck

We analyze the power counting of the peripheral singlet partial waves in nucleon-nucleon scattering. In agreement with conventional wisdom, we find that pion exchanges are perturbative in the peripheral singlets. We quantify from the effective field theory perspective the well-known suppression induced by the centrifugal barrier in the pion-exchange interactions. By exploring perturbation theory up to fourth order, we find that the one-pion-exchange (...)

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Institut de Physique Nucléaire Orsay - 15 rue Georges CLEMENCEAU - 91406 ORSAY (FRANCE)
UMR 8608 - CNRS/IN2P3

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