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Antonio Pineda

Publications and source records attributed to Antonio Pineda.

At least 73 records · Page 4Linked to original sources
arXiv2006

Renormalization Group Improved Sum Rule Analysis for the Bottom Quark Mass

We study the effect of resumming large logarithms in the determination of the bottom quark mass through a non-relativistic sum rule analysis. Our result is complete at next-to-leading-logarithmic accuracy and includes some known contributions at next-to-next-to-leading logarithmic accuracy. Compared to finite order computations, the reliability of the theoretical evaluation is greatly improved, resulting in a substantially reduced scale dependence and a faster convergent perturbative series. This allows us to significantly improve over previous determinations of the $\MS$ bottom quark mass, $\bar{m}_b$, from non-relativistic sum rules. Our final figure reads $\bar{m}_b(\bar{m}_b)=4.19\pm 0.06$ GeV.

hep-ph↗
arXiv2005

Fit to the Bjorken, Ellis-Jaffe and Gross-Llewellyn-Smith sum rules in a renormalon based approach

We study the large order behaviour in perturbation theory of the Bjorken, Ellis-Jaffe and Gross-Llewellyn-Smith sum rules. In particular, we consider their first infrared renormalons, for which we obtain their analytic structure with logarithmic accuracy and also an approximate determination of their normalization constant. Estimates of higher order terms of the perturbative series are given. The Renormalon subtracted scheme is worked out for these observables and compared with experimental data. Overall, good agreement with experiment is found. This allows us to obtain {\hat a}_0 and some higher-twist non-perturbative constants from experiment: {\hat a}_0=0.141\pm 0.089; f_{3,RS}(1 GeV)=-0.124^{+0.137}_{-0.142} GeV^2.

hep-ph↗
arXiv2005

Lattice and renormalons in heavy quark physics

Perturbative expansions of QCD observables in powers of $α_s$ are believed to be asymptotic and non-Borel summable due to the existence of singularities in the Borel plane (renormalons). This fact is connected with the factorization of scales (which is inherent to QCD and asymptotic freedom) and jeopardizes the convergence of the perturbative expansion and the accurate determination of power-suppressed corrections. This problem is more acute for physical systems composed by one or more heavy quarks. In lattice regulations, it reflects on the appearance of power-like divergences in the inverse of the lattice spacing for a series of quantities ($\bar Λ$, gluelump masses, the singlet and hybrid potentials, ...) making that the continuum limit can not be reached for them. Nevertheless, all these problems are solved within the framework of effective field theories with renormalon substraction. This allows us to obtain convergent perturbative series and to unambiguously define power corrections. In particular, one can connect with lattice results. Remarkably enough the dependence on the lattice spacing can be predicted by perturbation theory. This framework has been applied to the prediction of the gluelump masses and the singlet and octet (hybrid) potentials at short distances, as well as to their comparison with lattice simulations. Overall, very good agreement with data is obtained.

hep-lat↗
arXiv2005

Effective field theories for heavy quarkonium

We review recent theoretical developments in heavy quarkonium physics from the point of view of Effective Field Theories of QCD. We discuss Non-Relativistic QCD and concentrate on potential Non-Relativistic QCD. Our main goal will be to derive QCD Schrödinger-like equations that govern the heavy quarkonium physics in the weak and strong coupling regime. We also discuss a selected set of applications, which include spectroscopy, inclusive decays and electromagnetic threshold production.

hep-ph↗
arXiv2004

The chiral structure of the Lamb shift and the definition of the proton radius

The standard definition of the electromagnetic radius of a charged particle (in particular the proton) is ambiguous once electromagnetic corrections are considered. We argue that a natural definition can be given within an effective field theory framework in terms of a matching coefficient. The definition of the neutron radius is also discussed. We elaborate on the effective field theory relevant for the hydrogen and muonic hydrogen, specially for the latter. We compute the hadronic corrections to the lamb shift (for the polarizability effects only with logarithmic accuracy) within heavy baryon effective theory. We find that they diverge in the inverse of the pion mass in the chiral limit.

hep-ph↗
arXiv2004

The Renormalization group in non-relativistic theories

The resummation of logarithms in Quantum Field Theories is a long tale plenty of successes, yet the resummation of logarithms in non-relativistic theories has remained elusive. This was the most frustrating, since the first quantum field theory log ever computed was the Lamb shift one. We briefly review recent progress on the resummation of logarithms of $α$, which appear in the physics of non-relativistic states, using effective field theories. We put special emphasis on the basic formalism.

hep-ph↗
arXiv2004

Phenomenological impact of the resummation of logs of alpha in heavy quarkonium

Here we would like to review recent progress on the resummation on logarithms of $α_s$ in heavy quarkonium. We will mainly focus on the phenomenological relevance of these achievements. Determinations of the $η_b(1S)$ mass, $B_c(1S)$ hyperfine splitting, inclusive electromagnetic decays and implications for $t$-$\bar t$ production near threshold.

hep-ph↗
arXiv2003

QCD phenomenology of static sources and gluonic excitations at short distances

New lattice data for the Pi_u and Sigma_u^- potentials at short distances are presented. We compare perturbation theory to the lower static hybrid potentials and find good agreement at short distances, once the renormalon ambiguities are accounted for. We use the non-perturbatively determined continuum-limit static hybrid and ground state potentials at short distances to determine the gluelump energies. The result is consistent with an estimate obtained from the gluelump data at finite lattice spacings. For the lightest gluelump, we obtain Lambda_B^{RS}(nu_f=2.5/r_0)=[2.25\pm 0.10(latt.)\pm 0.21 (th.)\pm 0.08 (Lambda_{MS})]/r_0 in the quenched approximation with r_0^{-1} approx 400 MeV. We show that, to quote sensible numbers for the absolute values of the gluelump energies, it is necessary to handle the singularities of the singlet and octet potentials in the Borel plane. We propose to subtract the renormalons of the short-distance matching coefficients, the potentials in this case. For the singlet potential the leading renormalon is already known and related to that of the pole mass, for the octet potential a new renormalon appears, which we approximately evaluate. We also apply our methods to heavy light mesons in the static limit and from the lattice simulations available in the literature we obtain the quenched result \bar{Lambda}^{RS}(nu_f=2.5/r_0)=[1.17\pm 0.08(latt.)\pm 0.13 (th.) \pm 0.09 (Lambda_{MS})]/r_0. We calculate m_{b,MS}(m_{b,MS}) and apply our methods to gluinonia whose dynamics are governed by the singlet potential between adjoint sources. We can exclude non-standard linear short-distance contributions to the static potentials, with good accuracy.

hep-ph↗
arXiv2003

Learning about the chiral structure of the proton from the hyperfine splitting

The complete analytical $O(m_l^3α^5/m_p^2\times (\log{m_π}, \logΔ, \log{m_l}))$ contribution to the Hyperfine splitting is given. It can explain about 2/3 of the difference between experiment and the pure QED prediction when setting the renormalization scale at the $ρ$ mass. The suppression of the polarizability piece with respect the Zemach one seems to be, to a large extent, a numerical accident. We give an estimate of the matching coefficient of the spin-dependent proton-lepton operator in heavy baryon effective theory.

hep-ph↗
arXiv2003

Leading Chiral Logarithms to the Hyperfine Splitting of the Hydrogen and Muonic Hydrogen

We study the hydrogen and muonic hydrogen within an effective field theory framework. We perform the matching between heavy baryon effective theory coupled to photons and leptons and the relevant effective field theory at atomic scales. This matching can be performed in a perturbative expansion in alpha, 1/m_p and the chiral counting. We then compute the O(m_{l_i}^3 alpha^5/m_p^2 x logarithms) contribution (including the leading chiral logarithms) to the Hyperfine splitting and compare with experiment. They can explain about 2/3 of the difference between experiment and the pure QED prediction when setting the renormalization scale at the rho mass. We give an estimate of the matching coefficient of the spin-dependent proton-lepton operator in heavy baryon effective theory.

hep-ph↗
arXiv2002

Inclusive Decays of Heavy Quarkonium to Light Particles

We derive the imaginary part of the potential NRQCD Hamiltonian up to order 1/m^4, when the typical momentum transfer between the heavy quarks is of the order of Lambda_{QCD} or greater, and the binding energy E much smaller than Lambda_{QCD}. We use this result to calculate the inclusive decay widths into light hadrons, photons and lepton pairs, up to O(mv^3 x (Lambda_{QCD}^2/m^2,E/m)) and O(mv^5) times a short-distance coefficient, for S- and P-wave heavy quarkonium states, respectively. We achieve a large reduction in the number of unknown non-perturbative parameters and, therefore, we obtain new model-independent QCD predictions. All the NRQCD matrix elements relevant to that order are expressed in terms of the wave functions at the origin and six universal non-perturbative parameters. The wave-function dependence factorizes and drops out in the ratio of hadronic and electromagnetic decay widths. The universal non-perturbative parameters are expressed in terms of gluonic field-strength correlators, which may be fixed by experimental data or, alternatively, by lattice simulations. Our expressions are expected to hold for most of the charmonium and bottomonium states below threshold. The calculations and methodology are explained in detail so that the evaluation of higher order NRQCD matrix elements in this framework should be straightforward. An example is provided.

hep-ph↗
arXiv2002

The static potential: lattice versus perturbation theory in a renormalon-based approach

We compare, for the static potential and at short distances, perturbation theory with the results of lattice simulations. We show that a renormalon-dominance picture explains why in the literature sometimes agreement, and another disagreement, is found between lattice simulations and perturbation theory depending on the different implementations of the latter. We also show that, within a renormalon-based scheme, perturbation theory agrees with lattice simulations.

hep-ph↗
arXiv2002

Renormalization group improvement of the spectrum of Hydrogen-like atoms with massless fermions

We obtain the next-to-next-to-leading-log renormalization group improvement of the spectrum of Hydrogen-like atoms with massless fermions by using potential NRQED. These results can also be applied to the computation of the muonic Hydrogen spectrum where we are able to reproduce some known double logs at O(mα^6). We compare with other formalisms dealing with log resummation available in the literature.

hep-ph↗
arXiv2002

Renormalization group improvement of the NRQCD Lagrangian and heavy quarkonium spectrum

We complete the leading-log renormalization group scaling of the NRQCD Lagrangian at $O(1/m^2)$. The next-to-next-to-leading-log renormalization group scaling of the potential NRQCD Lagrangian (as far as the singlet is concerned) is also obtained in the situation $mα_s \gg Λ_{QCD}$. As a by-product, we obtain the heavy quarkonium spectrum with the same accuracy in the situation $mα_s^2 \simg Λ_{QCD}$. When $Λ_{QCD} \ll mα_s^2$, this is equivalent to obtain the whole set of $O(mα_s^{(n+4)} \ln^n α_s)$ terms in the heavy quarkonium spectrum. The implications of our results in the non-perturbative situation $mα_s \sim Λ_{QCD}$ are also mentioned.

hep-ph↗
arXiv2002

Next-to-leading-log renormalization-group running in heavy-quarkonium creation and annihilation

In the framework of potential NRQCD, we obtain the next-to-leading-log renormalization-group running of the matching coefficients for the heavy quarkonium production currents near threshold. This allows to obtain S-wave heavy-quarkonium production/annihilation observables with next-to-leading-log accuracy within perturbative QCD. In particular, we give expressions for the decays of heavy quarkonium to e^+e^- and to two photons. We also compute the O(mα^8\ln^3α) corrections to the Hydrogen spectrum.

hep-ph↗
arXiv2002

Heavy Quarkonium Potential and inclusive decay widths in terms of Wilson loops

We briefly summarize some results obtained by potential NRQCD in the non perturbative regime: 1) a systematic procedure to obtain the heavy quarkonium potential in the 1/m expansion (with explicit expressions up to O(1/m^2) in terms of Wilson loops), and 2) a description of the heavy quarkonium inclusive decays to light particles, and of the NRQCD matrix elements (also the octet ones), in terms of the wave-function at the origen and some gluonic field-strength correlators.

hep-ph↗