Predicting D -> sigma pi

We examine the D -> sigma pi amplitude through a constituent quark-meson model, incorporating heavy quark and chiral symmetries, finding a good agreement with the recent E791 data analysis of D -> 3 pi via sigma.Comment: 6 pages, RevTex, One new contribution added, typos correcte

Mass of the Ds(0+,1+D_s(0^+, 1^+) system

Théori

The classical Lenz vector and the two-dimensional quantum harmonic oscillator

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Prospects for Higgs properties determination at the LHC

The strategies recently developed to study Higgs boson properties at the LHC are reviewed. It is shown how to obtain model-independent determinations of couplings to fermions and gauge bosons by exploiting different production and decay channels. We consider in some detail the case of Weak Boson Fusion Higgs production with H --> b \bar b as well as the prospects for the determination of the Higgs self-coupling at the SLHC.Comment: LaTeX (using npb style), 5 pages, 1 .eps figure. Talk presented at RADCOR and Loops and Legs 2002, 8-13 September 2002, Kloster Banz, Germany. Added one referenc

Finite Size Analysis of the U(1) Background Field Effective Action

We apply the finite size scaling analysis to the derivative of the density of the effective action for the lattice U(1) pure gauge theory in an external constant magnetic field. We found the presence of a continuous phase transition. Moreover, our extimate of of the critical parameters gives values consistent with those extracted from the analysis of the specific heat.Comment: LaTeX2e, 12 pages (5 figures

J/psi Absorption in Heavy Ion Collisions

We present a new calculation of the pi-J/psi dissociation cross sections within the Constituent Quark-Meson Model recently introduced. To discuss the absorption of J/psi in heavy-ion collisions, we assume the J/psi to be produced inside a thermalized pion gas, as discussed by Bjorken, and introduce the corrections due to absorption by nuclear matter as well. We fit the absorption length of the J/psi to the data obtained at the CERN SPS by the NA50 Collaboration for Pb-Pb collisions. Collisions of lower centrality allow us to determine the temperature and the energy density of the pion gas. For both these quantities we find values close to those indicated by lattice gauge calculations for the transition to a quark-gluon plasma. A simple extrapolation to more central collisions, which takes into account the increase of the energy deposited due to the increased nucleon flux, fails to reproduce the break in J/psi absorption indicated by NA50, thus lending support to the idea that an unconfined quark-gluon phase may have been produced. This conclusion could be sharpened by analysing in a similar way, as a function of centrality, other observables such as strange particle production.Comment: 12 pages, 7 figure

New bounds on millicharged particles from cosmology

Particles with millicharge q and sub-eV mass can be produced in photon-photon collisions, distorting the energy spectrum of the Cosmic Microwave Background. We derive the conservative bound q < 10^-7 e (as well as model-dependent bounds two orders of magnitude stronger), incompatible with proposed interpretations of the PVLAS anomaly based on millicharged production or on millicharged-mediated axion-like couplings.Comment: 7 pages, 2 figures. Final versio

J/psi couplings to charmed resonances and to pi

We present an evaluation of the strong couplings JD^(*)D^(*) and JD^(*)D^(*)pi by an effective field theory of quarks and mesons. These couplings are necessary to calculate pi+J/psi --> D^(*)+barD^(*) cross sections, an important background to the J/psi suppression signal in the quark-gluon plasma. We write down the general effective lagrangian and compute the relevant couplings in the soft pion limit and beyond.Comment: 11 pages, 4 figures, 2 reference added and minor comments, style changed to RevTe

More loosely bound hadron molecules at CDF?

In a recent paper we have proposed a method to estimate the prompt production cross section of X(3872) at the Tevatron assuming that this particle is a loosely bound molecule of a D and a D*bar meson. Under this hypothesis we find that it is impossible to explain the high prompt production cross section found by CDF at sigma(X(3872)) \sim 30-70 nb as our theoretical prediction is about 300 times smaller than the measured one. Following our work, Artoisenet and Braaten, have suggested that final state interactions in the DD*bar system might be so strong to push the result we obtained for the cross section up to the experimental value. Relying on their conclusions we show that the production of another very narrow loosely bound molecule, the X_s=D_s D_s*bar, could be similarly enhanced. X_s should then be detectable at CDF with a mass of 4080 MeV and a prompt production cross section of sigma(X_s) \sim 1-3 nb.Comment: Minor revisions made. To appear in Phys Lett

e+e- --> e+e- pi0 pi0 at Daphne

The production of the sigma(500) meson in gamma gamma --> pi0 pi0 is studied. In particular, the KLOE data collected during the DAPHNE run at sqrt(s)= 1 GeV are appropriate to this purpose because of the strong reduction of Kaon backgrounds.Comment: 13 pages, 9 figures, few comments adde