Meson Mass Corrections Research Articles

NNLO charmed-meson fragmentation functions and their uncertainties in the presence of meson mass corrections

The main aim of this paper is to present new sets of non-perturbative fragmentation functions (FFs) for D^0 and D^+ mesons at next-to-leading (NLO) and, for the first time, at next-to-next-to-leading order (NNLO) in the overline{mathrm {MS}} factorization scheme with five massless quark flavors. This new determination of FFs is based on the QCD fit to the OPAL experimental data for hadron production in the electron-positron single-inclusive annihilation (SIA). We discuss in detail the novel aspects of the methodology used in our analysis and the validity of obtained FFs by comparing with previous works in literature which have been carried out up to NLO accuracy. We will also incorporate the effect of charmed meson mass corrections into our QCD analysis and discuss the improvements upon inclusion of these effects. The uncertainties in the extracted FFs as well as in the corresponding observables are estimated using the “Hessian” approach. For a typical application, we use our new FFs to make theoretical predictions for the energy distributions of charmed mesons inclusively produced through the decay of unpolarized top quarks, to be measured at the CERN LHC. As a result of this analysis, suggestions are discussed for possible future studies on the current topic to consider any theory improvements and other available experimental observables.

First direct lattice-QCD calculation of the x -dependence of the pion parton distribution function

We present the first direct lattice-QCD calculation of the $\mathrm{Bjorken}\text{\ensuremath{-}}x$ dependence of the valence quark distribution of the pion. Using large-momentum effective theory (LaMET), we calculate the boosted pion state with long Wilson link operators. After implementing the one-loop matching and meson mass corrections, our result at ${m}_{\ensuremath{\pi}}\ensuremath{\approx}310\text{ }\text{ }\mathrm{MeV}$ is in agreement with those extracted from experimental data as well as from the Dyson-Schwinger equation in the $\mathrm{small}\text{\ensuremath{-}}x$ region, but there is a sizeable discrepancy in the $\mathrm{large}\text{\ensuremath{-}}x$ region. This discrepancy provides a nice opportunity to systematically study and disentangle the artifacts in the LaMET approach, which will eventually help to discern various existing analyses in the literature.

B(s), D(s)→ π, K, η, ρ, K*, ω, ϕ TRANSITION FORM FACTORS AND DECAY RATES WITH EXTRACTION OF THE CKM PARAMETERS |Vub|, |Vcs|, |Vcd|

A systematic calculation for the transition form factors of heavy to light mesons (B, Bs, D, Ds→ π, K, η, ρ, K*, ω, ϕ) is carried out by using light-cone sum rules in the framework of heavy quark effective field theory. The heavy quark symmetry at the leading order of 1/mQexpansion enables us to reduce the independent wave functions and establish interesting relations among form factors. Some relations hold for the whole region of momentum transfer. The meson distribution amplitudes up to twist-4 including the contributions from higher conformal spin partial waves and light meson mass corrections are considered. The CKM matrix elements |Vub|, |Vcs| and |Vcd| are extracted from some relatively well-measured decay channels. A detailed prediction for the branching ratios of heavy to light meson decays is then presented. The resulting predictions for the semileptonic and radiative decay rates of heavy to light mesons (B, Bs, D, Ds→ π, K, η, ρ, K*, ω, ϕ) are found to be compatible with the current experimental data and can be tested by more precise experiments at B-factory, LHCb, BEPCII and CLEOc.

Vector meson mass corrections at [formula omitted] in PQChPT with Wilson and Ginsparg–Wilson quarks

We derive the mixed as well as unmixed lattice heavy meson chiral Lagrangian up to order O(a2), with Wilson and Ginsparg–Wilson fermions. We consider two flavor partially quenched QCD and calculate vector meson mass corrections up to order O(a2), including the corrections associated with the violation of rotational O(4) symmetry down to the hypercubic group. Our calculations also include the one-loop, phenomenological contribution from the ρ→ππ decay channel. The final result is a chiral-continuum extrapolation formula with model dependent coefficients from which one can recover the physical ρ meson mass from the large amount of current lattice data. As a verification of our result, the chiral-continuum extrapolation formula is compared with that used in numerical simulations.

Extending the utility of partially quenched QCD

It has been proposed that partially quenched chiral perturbation theory can be used together with partially quenched lattice QCD to determine the low-energy constants of real QCD. We point out a complication of this approach and show how it can be resolved. Partial quenching changes the chiral symmetry group and introduces a new independent four-derivative operator. We explore the effects of this new operator. We describe tree-level scattering processes to which it contributes, and show how they can be used, in principle, to deterimine its unknown coefficient. We also calculate its lowest-order (one-loop) contribution to charged meson masses and decay constants. In addition, we present the form of the analytic next-to-next-to-leading order meson mass and decay constant corrections, which are needed for lattice fits.

Higher twist distribution amplitudes of vector mesons in QCD: twist-4 distributions and meson mass corrections

We present a systematic study of twist-4 light-cone distribution amplitudes of vector mesons in QCD, which is based on conformal expansion. The structure of meson mass corrections is studied in detail. A complete set of distribution amplitudes is constructed, which satisfies all (exact) equations of motion and constraints from conformal expansion. Non-perturbative input parameters are estimated from QCD sum rules. Our study suggests that meson mass corrections may present a dominant source of higher twist effects in exclusive processes.

Theoretical update of pseudoscalar meson distribution amplitudes of higher twist: the nonsinglet case

We discuss the two and three particle light-cone distribution amplitudes (DAs) of pseudoscalar nonsinglet mesons of twist 3 and 4. Using nonlocal operator identities and conformal expansion, we derive closed expressions for several DAs. We also include meson-mass corrections which prove to be dominant in the twist 4 DAs of K and eta mesons. Explicit parametrizations for the DAs of pi, K and eta mesons are given, with the numerical input parameters determined from QCD sum rules.

Higher twist distribution amplitudes of vector mesons in QCD: Formalism and twist 3 distributions

We present a systematic study of twist 3 light-cone distribution amplitudes of vector mesons in QCD, which is based on conformal expansion and takes into account meson and quark mass corrections. A complete set of distribution amplitudes is constructed for ϱ, ω, K ∗ and φ mesons, which satisfies all (exact) equations of motion and constraints from conformal expansion. Nonperturbative input parameters are calculated from QCD sum rules, including an update of SU(3) breaking corrections in the leading twist distributions.