NRQCD Confronts LHCb Data on Quarkonium Production within Jets.

We analyze the recent LHCb measurement of the distribution of the fraction of the transverse momentum, z(J/ψ), carried by the J/ψ within a jet. LHCb data are compared with analytic calculations using the fragmenting jet function (FJF) formalism for studying J/ψ in jets. Logarithms in the FJFs are resummed using Dokshitzer-Gribov-Lipatov-Altarelli-Parisi evolution. We also convolve hard QCD partonic cross sections, showered with pythia, with leading order nonrelativistic quantum chromodynamics (NRQCD) fragmentation functions and obtain consistent results. Both approaches use madgraph to calculate the hard process that creates the jet initiating parton. These calculations give reasonable agreement with the z(J/ψ) distribution that was shown to be poorly described by default pythia simulations in the LHCb paper. We compare our predictions for the J/ψ distribution using various extractions of nonperturbative NRQCD long-distance matrix elements (LDMEs) in the literature. NRQCD calculations agree with LHCb data better than default pythia regardless of which fit to the LDMEs is used. LDMEs from fits that focus exclusively on high transverse momentum data from colliders are in good agreement with the LHCb measurement.

Isospin violation in e+ e- -->BB.

The ratio of the B+ B- and B0B0 production rates in e+ e- annihilation is computed as a function of the B meson velocity and BB*pi coupling constant, using a nonrelativistic effective field theory.

Leading-particle effect from heavy-quark recombination.

The leading particle effect in charm hadroproduction is an enhancement of the cross section for a charmed hadron D in the forward direction of the beam when the beam hadron has a valence parton in common with the D. The large D(+)/D(-) asymmetry observed by the E791 experiment is an example of this phenomenon. We show that the heavy-quark recombination mechanism provides an economical expla-nation for this effect. In particular, the D(+)/D(-) asymmetry can be fit reasonably well using a single parameter whose value is consistent with a recent determination from charm photoproduction.

Dilute Bose-Einstein condensate with large scattering length.

We study a dilute Bose gas of atoms whose scattering length a is large compared to the range of their interaction. We calculate the energy density E of a homogeneous Bose-Einstein condensate (BEC) to second order in the low-density expansion, expressing it in terms of a and a second parameter Lambda* that determines the low-energy observables in the three-body sector. The second-order correction to E has a small imaginary part that reflects the instability due to three-body recombination. In the case of a trapped BEC with large negative a, we calculate the coefficient of the three-body mean-field term in E in terms of a and Lambda*. It can be very large if there is an Efimov state near threshold.