Searcharxiv⌕ Search

arXiv subjects

Antonio Pineda

Publications and source records attributed to Antonio Pineda.

At least 37 records · Page 2Linked to original sources
arXiv2017

Relativistic corrections to the static energy in terms of Wilson loops at weak coupling

We consider the ${\mathcal O}(1/m)$ and the spin-independent momentum-dependent ${\mathcal O}(1/m^2)$ quasi-static energies of heavy quarkonium (with unequal masses). They are defined nonperturbatively in terms of Wilson loops. We determine their short-distance behavior through ${\mathcal O}(α^3)$ and ${\mathcal O}(α^2)$, respectively. In particular, we calculate the ultrasoft contributions to the quasi-static energies, which requires the resummation of potential interactions. Our results can be directly compared to lattice simulations. In addition, we also compare the available lattice data with the expectations from effective string models for the long-distance behavior of the quasi-static energies.

hep-ph↗
arXiv2017

Model-independent determination of the two-photon exchange contribution to hyperfine splitting in muonic hydrogen

We obtain a model-independent prediction for the two-photon exchange contribution to the hyperfine splitting in muonic hydrogen. We use the relation of the Wilson coefficients of the spin-dependent dimension-six four-fermion operator of NRQED applied to the electron-proton and to the muon-proton sectors. Their difference can be reliably computed using chiral perturbation theory, whereas the Wilson coefficient of the electron-proton sector can be determined from the hyperfine splitting in hydrogen. This allows us to give a precise model-independent determination of the Wilson coefficient for the muon-proton sector, and consequently of the two-photon exchange contribution to the hyperfine splitting in muonic hydrogen, which reads $δ\bar E_{pμ,\rm HF}^{\rm TPE}(nS)=-\frac{1}{n^3}1.161(20)$ meV. Together with the associated QED analysis, we obtain a prediction for the hyperfine splitting in muonic hydrogen that reads $E^{\rm th}_{pμ,\rm HF}(1S)=182.623(27)$ meV and $E^{\rm th}_{pμ,\rm HF}(2S)=22.8123(33)$ meV. The error is dominated by the two-photon exchange contribution.

nucl-th↗
arXiv2017

Proton radius from electron-proton scattering and chiral perturbation theory

We determine the root-mean-square proton charge radius, $R_{\rm p}$, from a fit to low-$Q^2$ electron-proton elastic scattering cross section data with the higher moments fixed (within uncertainties) to the values predicted by chiral perturbation theory. We obtain $R_{\rm p}=0.857(11)$ fm. This number falls between the value obtained from muonic hydrogen analyses and the CODATA value (based upon atomic hydrogen spectroscopy and electron-proton scattering determinations).

nucl-th↗
arXiv2016

Mass of the bottom quark from Upsilon(1S) at NNNLO: an update

We update our perturbative determination of MSbar bottom quark mass mb(mb), by including the recently obtained four-loop coefficient in the relation between the pole and MSbar mass. First the renormalon subtracted (RS or RS') mass is determined from the known mass of the Upsilon(1S) meson, where we use the renormalon residue Nm obtained from the asymptotic behavior of the coefficient of the 3-loop static singlet potential. MSbar mass is then obtained using the 4-loop renormalon-free relation between the RS (RS') and MSbar mass. We argue that the effects of the charm quark mass are accounted for by effectively using Nf=3 in the mass relations. The extracted value is mb(mb) = 4222(40) MeV, where the uncertainty is dominated by the renormalization scale dependence.

hep-ph↗
arXiv2015

The Lamb shift in muonic hydrogen and the proton radius from effective field theories

We comprehensively analyse the theoretical prediction for the Lamb shift in muonic hydrogen, and the associated determination of the proton radius. We use effective field theories. This allows us to relate the proton radius with well-defined objects in quantum field theory, eliminating unnecessary model dependence. The use of effective field theories also helps us to organize the computation so that we can clearly state the parametric accuracy of the result. In this paper we review all (and check several of) the contributions to the energy shift of order $α^5$, as well as those that scale like $α^6\times$logarithms in the context of non-relativistic effective field theories of QED.

hep-ph↗
arXiv2015

The two-photon exchange contribution to muonic hydrogen from chiral perturbation theory

We compute the spin-dependent and spin-independent structure functions of the forward virtual-photon Compton tensor of the proton at one loop using heavy baryon effective theory including the Delta particle. We compare with previous results when existing. Using these results we obtain the leading hadronic contributions, associated to the pion and Delta particles, to the Wilson coefficients of the lepton-proton four fermion operators in NRQED. The spin-independent coefficient yields a pure prediction for the two-photon exchange contribution to the muonic hydrogen Lamb shift, $ΔE_{\rm TPE}(π\&Δ)=34(13)$ $μ$eV. We also compute the charge, $\langle r^n \rangle$, and Zemach, $\langle r^n \rangle_{(2)}$, moments for $n \geq 3$. Finally, we discuss the spin-dependent case, for which we compute the difference between the four-fermion Wilson coefficients relevant for hydrogen and muonic hydrogen.

hep-ph↗
arXiv2015

Phenomenology of renormalons and the OPE from lattice regularization: the gluon condensate and the heavy quark pole mass

We study the operator product expansion of the plaquette (gluon condensate) and the self-energy of an infinitely heavy quark. We first compute their perturbative expansions to order $α^{35}$ and $α^{20}$, respectively, in the lattice scheme. In both cases we reach the asymptotic regime where the renormalon behavior sets in. Subtracting the perturbative series, we obtain the leading non-perturbative corrections of their respective operator product expansions. In the first case we obtain the gluon condensate and in the second the binding energy of the heavy quark in the infinite mass limit. The results are fully consistent with the expectations from renormalons and the operator product expansion.

hep-ph↗
arXiv2014

Improved determination of Heavy Quarkonium magnetic dipole transitions in pNRQCD

We compute the magnetic dipole transitions between low lying Heavy Quarkonium states in a model independent way. We use the weak-coupling version of the effective field theory named potential NRQCD with the static potential exactly incorporated in the leading order Hamiltonian. The precision we reach is $k_γ^3/m^2\times{\cal O}(α_s^2,v^2)$ and $k_γ^3/m^2\times{\cal O}(v^4)$ for the allowed and forbidden transitions respectively. We also resum the large logarithms associated to the heavy quark mass scale. The specific transitions considered in this paper are the following: $Υ(1S) \to η_b(1S)\,γ$, $J/ψ(1S) \to η_c(1S)\,γ$, $h_b(1P) \to χ_{b0,1}(1P)\,γ$, $χ_{b2}(1P) \to h_b(1P)\,γ$, $Υ(2S) \to η_b(2S)\,γ$, $Υ(2S) \to η_b(1S)\,γ$ and $η_b(2S)\toΥ(1S)\,γ$. The effect of the new power counting is found to be large and the exact treatment of the soft logarithms of the static potential makes the factorization scale dependence much smaller. The convergence for the $b\bar b$ ground state is quite good, and also quite reasonable for the $c\bar c$ ground state and the $b\bar b$ 1P state. For all of them we give solid predictions. For the 2S decays the situation is less conclusive, yet our results are perfectly consistent with existing data, as the previous disagreement with experiment for the $Υ(2S) \to η_b(1S)\,γ$ decay fades away. We also profit to compute some expectation values like the electromagnetic radius, r^2, or p^2. We find r^2 to be nicely convergent in all cases, whereas the convergence of p^2 is typically worse.

hep-ph↗
arXiv2014

The bottom quark mass from the $Υ(1S)$ system at NNNLO

We obtain an improved determination of the normalization constant of the first infrared renormalon of the pole mass (and the singlet static potential). For $N_f=3$ it reads $N_m=0.563(26)$. Charm quark effects in the bottom quark mass determination are carefully investigated. Finally, we determine the bottom quark mass using the NNNLO perturbative expression for the $Υ(1S)$ mass. We work in the renormalon subtracted scheme, which allows us to control the divergence of the perturbation series due to pole mass renormalon. Our result for the ${\overline {\rm MS}}$ mass reads ${\overline m}_{b}({\overline m}_{b})=4201(43)$ MeV.

hep-ph↗
arXiv2014

Review of Heavy Quarkonium at weak coupling

We review weakly-bound heavy quarkonium systems using effective field theories of QCD. We concentrate on potential Non-Relativistic QCD, which provides with a well founded connection between QCD and descriptions of the heavy quarkonium dynamics in terms of Schrödinger-like equations. This connection is obtained using standard quantum field theory techniques such as dimensional regularization, which is used throughout, and renormalization. Renormalization group equations naturally follow. Certain effort is made to illustrate how computations are performed and the necessary techniques, providing some examples. Finally, we briefly review a selected set of applications, which include spectroscopy, radiative transitions, Non-Relativistic sum rules, inclusive decays, and electromagnetic threshold production.

hep-ph↗
arXiv2014

Model-independent determination of the gluon condensate in four-dimensional SU(3) gauge theory

We determine the non-perturbative gluon condensate of four-dimensional SU(3) gauge theory in a model independent way. This is achieved by carefully subtracting high order perturbation theory results from non-perturbative lattice QCD determinations of the average plaquette. No indications of dimension two condensates are found. The value of the gluon condensate turns out to be of a similar size as the intrinsic ambiguity inherent to its definition.

hep-ph↗
arXiv2014

Model independent determination of the muonic hydrogen Lamb shift and proton radius

We obtain a model independent expression for the muonic hydrogen Lamb shift. This expression includes the leading logarithmic ${\cal O}(m_μα^6)$ terms, as well as the leading ${\cal O}(m_μα^5 \frac{m_μ^2}{m_ρ^2})$ hadronic effects. The latter are controlled by the chiral theory, which allows for their model independent determination. In this paper we give the missing piece for their complete expression including the pion and Delta particles. Out of this analysis and the experimental measurement of the muonic hydrogen Lamb shift we determine the electromagnetic proton radius: $r_p=0.8412(15)$ fm. This number is at 6.8$σ$ variance with respect to the CODATA value. The accuracy of our result is limited by uncomputed terms of ${\cal O}(m_μα^5\frac{m_μ^3}{m_ρ^3},m_μα^6)$. This parametric control of the uncertainties allows us to obtain a model independent determination of the error, which is dominated by hadronic effects.

hep-ph↗
arXiv2014

Perturbative expansion of the plaquette to ${\cal O}(α^{35})$ in four-dimensional SU(3) gauge theory

Using numerical stochastic perturbation theory, we determine the first 35 infinite volume coefficients of the perturbative expansion in powers of the strong coupling constant $α$ of the plaquette in SU(3) gluodynamics. These coefficients are obtained in lattice regularization with the standard Wilson gauge action. The on-set of the dominance of the dimension four renormalon associated to the gluon condensate is clearly observed. We determine the normalization of the corresponding singularity in the Borel plane and convert this into the $\overline{\mathrm{MS}}$ scheme. We also comment on the impact of the renormalon on non-perturbative determinations of the gluon condensate.

hep-ph↗
arXiv2014

The QCD static potential in D<4 dimensions at weak coupling

We study the static potential of a color singlet quark-antiquark pair with (fixed) distance r in D=3 and D=2 space-time dimensions at weak coupling (alpha r << 1 and g r << 1, respectively). Using the effective theory pNRQCD we determine the ultrasoft contributions, which cannot be computed in conventional perturbative QCD. We show in detail how the ultrasoft renormalization in pNRQCD is carried out. In three dimensions the precision of our results reaches O(alpha^3 r^2), i.e. NNLO in the multipole expansion, and NNLL in a alpha/DeltaV expansion, where DeltaV ~ alpha ln(alpha r). We even present results up to partly N^4LL order and compare them to existing lattice data. Finally we discuss the relevance of the perturbative calculation in two dimensions, where the exact result is known.

hep-th↗
arXiv2013

The regularization and determination of the Yang-Mills vacuum wave functional in three dimensions at O(e^2)

We complete the computation of the Yang-Mills vacuum wave functional in three dimensions at weak coupling with O(e^2) precision. We use two different methods to solve the functional Schroedinger equation. One of them generalizes to O(e^2) the method followed by Hatfield at O(e). The other uses the weak coupling version of the gauge invariant formulation of the Schroedinger equation and the ground state wave functional followed by Karabali, Nair, and Yelnikov. These methods need to be carefully regularized to yield correct results. This is done in this paper with full detail.

hep-th↗
arXiv2013

The Yang-Mills vacuum wave functional in three dimensions at weak coupling

We compute the Yang-Mills vacuum wave functional in three dimensions at weak coupling with O(e^2) precision. We use two different methods to solve the Schroedinger functional equation. One of them generalizes to O(e^2) the method followed by Hatfield at O(e). The other uses the weak coupling version of the gauge invariant formulation of the Schroedinger equation and the ground state wave functional followed by Karabali, Nair, and Yelnikov. We compare both results and discuss the differences between them.

hep-th↗
arXiv2013

Radiative transitions in pNRQCD

We review recent model independent determinations of the radiative transitions of heavy quarkonium obtained using potential NRQCD.

hep-ph↗