Observation and Properties of the X(3872) Decaying to J/ψ π + π − in pp Collisions at √ s= 1.96 TeV

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A new unitarization approach incorporated with chiral symmetry is established and applied to study the πK elastic scatterings. We demonstrate that the κ resonance exists, if the scattering length parameter in the I=1/2, J=0 channel does not deviate much from its value predicted by chiral perturbation theory. The mass and width of the κ resonance is found to be M κ = 594 ± 79M eV , Γ κ = 724 ± 332M eV , obtained by fitting the LASS data up to 1430MeV. Better determination to the pole parameters is possible if the chiral predictions on scattering lengths are taken into account.

We have searched for central production of a pair of photons with high transverse energies in pp collisions at √ s = 1.8 TeV using 70 pb −1 of data collected with the DØ detector at the Fermilab Tevatron in 1994-1996. If they exist, virtual heavy pointlike Dirac monopoles could rescatter pairs of nearly real photons into this final state via a box diagram. We observe no excess of events above background, and set lower 95% C.L. limits of 610, 870, or 1580 GeV/c 2 on the mass of a spin 0, 1/2, or 1 Dirac monopole.