arXiv subjects
Publications and source records attributed to A. Pineda.
We compute the hyperfine splitting in a heavy quarkonium composed of different flavors in next-to-leading logarithmic approximation using the nonrelativistic renormalization group. We predict the mass difference of the vector and pseudoscalar charm-bottom mesons to be $M(B^*_c)-M(B_c)=46 \pm 15 {(\rm th)} {}^{+13}_{-11} (δα_s)$ MeV.
We obtain the Potential NRQCD Lagrangian relevant for S-wave states with next-next-to-next-to-leading logarithmic (NNNLL) accuracy. We compute the heavy quarkonium mass of spin-averaged $l= 0$ (angular momentum) states, with otherwise arbitrary quantum numbers, with NNNLL accuracy. These results are complete up to a missing contribution of the two-loop soft running.
The ratio of the photon mediated production or annihilation rates of spin triplet and spin singlet heavy quarkonium states is computed to the next-to-next-to-leading logarithmic accuracy within the nonrelativistic renormalization group approach. The result is presented in analytical form and applied to the phenomenology of $t\bar{t}$, $b\bar{b}$ and $c\bar{c}$ systems. The use of the nonrelativistic renormalization group considerably improves the behaviour of the perturbative expansion and is crucial for accurate theoretical analysis. For bottomonium decays we predict $Γ(η_b(1S) \to γγ)=0.659\pm 0.089 ({\rm th.}) {}^{+0.019}_{-0.018} (δα_{\rm s})\pm 0.015 ({\rm exp.}) {\rm keV}$. Our results question the accuracy of the existing extractions of the strong coupling constant from the bottomonium annihilation. As a by-product we obtain novel corrections to the ratio of the ortho- and parapositronium decay rates: the corrections of order $α^4\ln^2α$ and $α^5\ln^3α$.
We sum up the next-to-leading logarithmic corrections to the heavy-quarkonium hyperfine splitting using the nonrelativistic renormalization group. On the basis of this result, we predict the mass of the $η_b$ meson to be $M(η_b)=9419 \pm 11 {(\rm th)} {}^{+9}_{-8} (δα_s) MeV$. The experimental measurement of $M(η_b)$ with a few MeV error would be sufficient to determine $α_s(M_Z)$ with an accuracy of $\pm 0.003$. The use of the nonrelativistic renormalization group is mandatory to reproduce the experimental value of the hyperfine splitting in charmonium.
This physics book provides detailed discussions on important topics in $τ$-charm physics that will be explored during the next few years at \bes3 . Both theoretical and experimental issues are covered, including extensive reviews of recent theoretical developments and experimental techniques. Among the subjects covered are: innovations in Partial Wave Analysis (PWA), theoretical and experimental techniques for Dalitz-plot analyses, analysis tools to extract absolute branching fractions and measurements of decay constants, form factors, and CP-violation and \DzDzb-oscillation parameters. Programs of QCD studies and near-threshold tau-lepton physics measurements are also discussed.
This report is the result of the collaboration and research effort of the Quarkonium Working Group over the last three years. It provides a comprehensive overview of the state of the art in heavy-quarkonium theory and experiment, covering quarkonium spectroscopy, decay, and production, the determination of QCD parameters from quarkonium observables, quarkonia in media, and the effects on quarkonia of physics beyond the Standard Model. An introduction to common theoretical and experimental tools is included. Future opportunities for research in quarkonium physics are also discussed.
We investigate the effects produced by the three-momentum scale $\sqrt{mΛ_{QCD}}$ in the strong coupling regime of heavy quarkonium. We compute the leading non-vanishing contributions due to this scale to the masses and inclusive decay widths. We find that they may provide leading corrections to the S-wave decay widths but only subleading corrections to the masses.
We show that some NRQCD colour-octet matrix elements can be written in terms of (derivatives of) wave functions at the origin and non-perturbative universal constants once the factorization between the soft and ultrasoft scale is achieved by using an effective field theory where only ultrasoft degrees of freedom are kept as dynamical entities. This allows us to derive a new set of relations between inclusive heavy-quarkonium P-wave decays into light hadrons with different principal quantum number and with different heavy flavour. In particular, we can estimate the branching ratios of bottomonium P-wave states by using charmonium data.
Within an effective field theory framework, we obtain an expression for the next-to-leading term in the $1/m$ expansion of the singlet $Q{\bar Q}$ QCD potential in terms of Wilson loops, which holds beyond perturbation theory. The ambiguities in the definition of the QCD potential beyond leading order in $1/m$ are discussed and a specific expression for the $1/m$ potential is given. We explicitly evaluate this expression at one loop and compare the outcome with the existing perturbative results. On general grounds we show that for quenched QED and fully Abelian-like models this expression exactly vanishes.
We compute the complete leading-log terms of the next-to-next-to-next-to-leading-order corrections to potential NRQCD. As a by-product we obtain the leading logs at $O(mα_s^5)$ in the heavy quarkonium spectrum. These leading logs, when $Λ_{QCD} \ll mα_s^2$, give the complete $O(mα_s^5 \ln α_s)$ corrections to the heavy quarkonium spectrum.
Within an effective field theory framework we study heavy-quark--antiquark systems with a typical distance between the heavy quark and the antiquark smaller than $1/Λ_{\rm QCD}$. A suitable definition of the potential is given within this framework, while non-potential (retardation) effects are taken into account in a systematic way. We explore different physical systems. Model-independent results on the short distance behavior of the energies of the gluonic excitations between static quarks are obtained. Finally, we show how infrared renormalons affecting the static potential get cancelled in the effective theory.
We study some general aspects of the formalism of potential NRQCD (pNRQCD), an effective field theory that deals with ultrasoft degrees of freedom in Heavy Quarkonium systems. Specific attention is paid to its effective Lagrangian that it is displayed at the present level of accuracy.
The definition of the quark-antiquark static potential is given within an effective field theory framework. The leading infrared divergences of the static singlet potential in perturbation theory are explicitly calculated.
In a recent paper, we included two loop, relativistic one loop and second order relativistic tree level corrections, plus leading nonperturbative contributions, to obtain a calculation of the lower states in the heavy quarkonium spectrum correct up to, and including, $O(α_s^4)$ and leading $\Lambdav^4/m^4$ terms. The results were obtained with, in particular, the value of the two loop static coefficient due to Peter; this been recently challenged by Schröder. In our previous paper we used Peter's result; in the present one we now give results with Schröder's, as this is likely to be the correct one. The variation is slight as the value of $b_1$ is only one among the various $O(α_s^4)$ contributions. With Schröder's expression we now have, $$m_b=5\,001^{+104}_{-66}\;\mev;\quad \bar{m}_b(\bar{m}_b^2)=4\,440^{+43}_{-28}\;\mev,$$ $$m_c=1\,866^{+190}_{-154}\;\mev;\quad \bar{m}_c(\bar{m}_c^2)=1\,531^{+132}_{-127}\;\mev.$$ Moreover, $$\Gammav(\Upsilonv\rightarrow e^+e^-)=1.07\pm0.28\;\kev \;(\hbox{exp.}=1.320\pm0.04\,\kev)$$ and the hyperfine splitting is predicted to be $$M(\Upsilonv)-M(η)=47^{+15}_{-13}\;\mev.$$
We discuss in detail potential NRQED (pNRQED), a previously proposed effective field theory for ultrasoft photons. The pNRQED lagrangian for the equal mass case is presented and it is shown that it correctly reproduces the positronium spectrum at order $mα^5$. The pNRQED lagrangian for the unequal mass case is also presented at the same order. Dimensional regularization is used throughout.
The matching coefficients for the four-quark operators in NRQCD (NRQED) are calculated at one loop using dimensional regularization for ultraviolet and infrared divergences. The matching for the electromagnetic current follows easily from our results. Both the unequal and equal mass cases are considered. The role played by the Coulomb infrared singularities is explained in detail.
We present a simple derivation of the Lamb shift using effective field theory techniques and dimensional regularisation.
We propose an effective field theory for heavy quark-antiquark bound states once the soft gluons have been integrated out. We also give new results for the matching between QCD (QED) and NRQCD (NRQED).