207 research outputs found
Weakly-bound Hadronic Molecule near a 3-body Threshold
The X(3872) seems to be a loosely-bound hadronic molecule whose constituents
are two charm mesons. A novel feature of this molecule is that the mass
difference of the constituents is close to the mass of a lighter meson that can
be exchanged between them, namely the pion. We analyze this feature in a simple
model with spin-0 mesons only. Various observables are calculated to
next-to-leading order in the interaction strength of the exchanged meson.
Renormalization requires summing a geometric series of next-to-leading order
corrections. The dependence of observables on the ultraviolet cutoff can be
removed by renormalizations of the mass of the heaviest meson, the coupling
constant for the contact interaction between the heavy mesons, and
short-distance coefficients in the operator product expansion. The
next-to-leading order correction has an unphysical infrared divergence at the
threshold of the two heavier mesons that can be eliminated by a further
resummation that takes into account the nonzero width of the heaviest meson.Comment: 37 pages, 13 figures, submitted to Phys.Rev.
Prompt J/psi Polarization at the Tevatron
The polarization of prompt J/psi at the Tevatron is calculated within the
nonrelativistic QCD (NRQCD) factorization framework. The contribution from
radiative decays of P-wave charmonium states decreases, but does not eliminate,
the transverse polarization at large transverse momentum. The prediction agrees
with measurements from the CDF collaboration at intermediate values of p_T, but
disagrees at the large values of p_T measured.Comment: 5 pages, 2 figures, Talk given at 5th Workshop on QCD, 3-7 January
2000, Villefranche-sur-Mer, Franc
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