15369742
J/Ψ photo-production at large z in soft collinear effective theory
One of the outstanding problems in J/{psi} physics is a systematic understanding of the differential photo-production cross section d{sigma}/dz({gamma} + p {yields} J/{psi} + X), where z = E{sub {psi}}/E{sub {gamma}} in the proton rest frame. The theoretical prediction based on the non-relativistic QCD (NRQCD) factorization formalism has a color-octet contribution which grows rapidly in the endpoint region, z {yields} 1, spoiling perturbation theory. In addition there are subleading operators which are enhanced by powers of 1/(1-z) and they must be resumed to all orders. Here an update of a systematic analysis is presented. The approach used to organize the endpoint behavior of the photo-production cross section is based on a combination of NRQCD and soft collinear effective theory. While a final result is not yet available, an intermediate result indicates that better agreement between theory and data will be achieved in this framework.
2000018
Systematics of quarkonium production at the LHC and double parton fragmentation
In this paper we discuss the systematics of quarkonium production at the LHC. In particular, we focus on the necessity to sum logs of the form log(Q/p⊥) and log(p⊥/mQ). We show that the former contributions are power suppressed, while the latter, whose contribution in fragmentation is well known, also arise in the short distance (i.e., non-fragmentation) production mechanisms. Though these contributions are suppressed by powers of mQ/p⊥, they can be enhanced by inverse powers of v, the relative velocity between heavy quarks in the quarkonium. In the limit p⊥ ≫ mQ short distance production can be thought of as the fragmentation of a pair of partons (i.e., the heavy quark and anti-quark) into the final state quarkonium. We derive an all order factorization theorem for this process in terms of double parton fragmentation functions (DPFF) and calculate the one-loop anomalous dimension matrix for the DPFF.
14054009
Extracting |Vub| from the hadronic mass spectrum of inclusive B decays
Abstract Following a strategy introduced earlier by the authors, we show that it is possible to extract | V ub | from the cut hadronic mass spectrum of B decays without large systematic errors which usually arise from having to model the Fermi motion of the heavy quark. We present a closed form expression for | V ub |/| V ts | which is accurate up to corrections of order α s 2 , α s ρ , ( Λ / m b ) 2 / ρ , where ρ is the experimental cut ( s c / m b 2 ) on the hadronic mass used to veto charmed decays. Modulo duality violation errors, which are intrinsic to all inclusive predictions, we estimate the theoretical error in the extraction to be at the 5% level.
14733049
Extracting V(ub) without recourse to structure functions
We present a closed form expression for $|{V}_{\mathrm{ub}}{|}^{2}/|{V}_{\mathrm{tb}}{V}_{\mathrm{ts}}^{*}{|}^{2}$ in terms of the end point photon and lepton spectra from the inclusive decays $\stackrel{\ensuremath{\rightarrow}}{B}{X}_{s}\ensuremath{\gamma}$ and $\stackrel{\ensuremath{\rightarrow}}{B}{X}_{u}\mathcal{l}\ensuremath{\nu},$ respectively, which includes the resummation of the end point logarithms at next to leading order and is completely independent of the B meson structure function. The use of this expression for extracting ${V}_{\mathrm{ub}}$ would eliminate the large systematic errors usually incurred due to the modeling of the heavy quarks' Fermi motion.
14803760
A comment on the extractions of V ub from radiative decays
Abstract We present a model independent closed form expression for |V ub | 2 /|V tb V ts ∗ | 2 , which includes the resummation of large endpoint logarithms as well as the interference effects from the operators O 2 and O 8 . We demonstrate that the method to extract | V ub | presented by the authors in hep-ph/9909404, and modified in this Letter to include interference effects, is not just a refinement of the method introduced in hep-ph/9312311. We also discuss the model dependence of the latter proposal. Furthermore, we show that the resummation is not negligible and that the Landau pole does not introduce any significant uncertainties.
20543615
Finite size corrections to the radiation reaction force in classical electrodynamics.
We introduce an effective field theory approach that describes the motion of finite size objects under the influence of electromagnetic fields. We prove that leading order effects due to the finite radius R of a spherically symmetric charge is order R2 rather than order R in any physical model, as widely claimed in the literature. This scaling arises as a consequence of Poincaré and gauge symmetries, which can be shown to exclude linear corrections. We use the formalism to calculate the leading order finite size correction to the Abraham-Lorentz-Dirac force.
15369742
J/Ψ photo-production at large z in soft collinear effective theory
One of the outstanding problems in J/{psi} physics is a systematic understanding of the differential photo-production cross section d{sigma}/dz({gamma} + p {yields} J/{psi} + X), where z = E{sub {psi}}/E{sub {gamma}} in the proton rest frame. The theoretical prediction based on the non-relativistic QCD (NRQCD) factorization formalism has a color-octet contribution which grows rapidly in the endpoint region, z {yields} 1, spoiling perturbation theory. In addition there are subleading operators which are enhanced by powers of 1/(1-z) and they must be resumed to all orders. Here an update of a systematic analysis is presented. The approach used to organize the endpoint behavior of the photo-production cross section is based on a combination of NRQCD and soft collinear effective theory. While a final result is not yet available, an intermediate result indicates that better agreement between theory and data will be achieved in this framework.