Towards extracting the timelike pion form factor on CLS twoflavour ensembles

Erben, Felix; Wittig, Hartmut; Mohler, Daniel; Green, Jeremy R.

doi:10.1051/epjconf/201817505027

Cited by 12 publications

(11 citation statements)

References 17 publications

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“…Implications for the calculation of the leading order HVP contribution to the muon anomalous magnetic moment a µ are discussed in Section V. Finally, Section VI summarises our results. Our analysis supersedes previous preliminary results presented in [27,28].…”

Section: Introductionsupporting

confidence: 89%

Rho resonance, timelike pion form factor, and implications for lattice studies of the hadronic vacuum polarization

et al. 2020

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We study isospin-1 P-wave ππ scattering in lattice QCD with two flavours of O(a) improved Wilson fermions. For pion masses ranging from m π = 265 MeV to m π = 437 MeV, we determine the energy spectrum in the centre-of-mass frame and in three moving frames. We obtain the scattering phase shifts using Lüscher's finite-volume quantisation condition. Fitting the dependence of the phase shifts on the scattering momentum to a Breit-Wigner form allows us to determine the resonance parameters m ρ and g ρππ . By combining the scattering phase shifts with the decay matrix element of the vector current, we calculate the timelike pion form factor, F π , and compare the results to the Gounaris-Sakurai representation of the form factor in terms of the resonance parameters. In addition, we fit our data for the form factor to the functional form suggested by the Omnès representation, which allows for the extraction of the charge radius of the pion. As a further application, we discuss the long-distance behaviour of the vector correlator, which is dominated by the two-pion channel. We reconstruct the long-distance part in two ways: one based on the finite-volume energies and matrix elements and the other based on F π . It is shown that this part can be accurately constrained using the reconstructions, which has important consequences for lattice calculations of the hadronic vacuum polarisation contribution to the muon anomalous magnetic moment. * felix.erben@ed.ac.uk

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Section: Introductionsupporting

confidence: 89%

Rho resonance, timelike pion form factor, and implications for lattice studies of the hadronic vacuum polarization

et al. 2020

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“…We choose to fit to the squared scattering momentum p 2 determined from each lattice energy, in a manner similar to what was done for fitting to the lattice energies in Ref. [54]. Fitting to the momentum rather than energy benefits from cancellations of statistical uncertainties that are correlated between E and m Λ .…”

Section: Finite Volume Analysismentioning

confidence: 99%

Lattice QCD study of the H dibaryon using hexaquark and two-baryon interpolators

et al. 2019

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We present a lattice QCD spectroscopy study in the isospin singlet, strangeness −2 sectors relevant for the conjectured H dibaryon. We employ both local and bilocal interpolating operators to isolate the ground state in the rest frame and in moving frames. Calculations are performed using two flavors of O(a)-improved Wilson fermions and a quenched strange quark. Our initial point-source method for constructing correlators does not allow for bilocal operators at the source; nevertheless, results from using these operators at the sink indicate that they provide an improved overlap onto the ground state in comparison with the local operators. We also present results, in the rest frame, using a second method based on distillation to compute a hermitian matrix of correlators with bilocal operators at both the source and the sink. This method yields a much more precise and reliable determination of the ground-state energy. In the flavor-SU(3) symmetric case, we apply Lüscher's finite-volume quantization condition to the rest-frame and moving-frame energy levels to determine the S-wave scattering phase shift, near and below the two-particle threshold. For a pion mass of 960 MeV, we find that there exists a bound H dibaryon with binding energy ∆E = (19 ± 10) MeV. In the 27-plet (dineutron) sector, the finite-volume analysis suggests that the existence of a bound state is unlikely.

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“…It is interesting to note that this correction is reduced by a factor 10 for m π L = 6. A calculation of the timelike pion form factor has been performed for a subset of our previously studied two-flavour ensembles [19]. The implications for a hvp µ will be discussed in a forthcoming publication [20].…”

Section: Preliminary Results: Light Quarksmentioning

confidence: 99%

The hadronic vacuum polarization contribution to $(g-2)_μ$ from $2+1$ flavours of O($a$) improved Wilson quarks

Gérardin¹,

Harris²,

Hippel³

et al. 2018

Preprint

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We report on our ongoing project to determine the leading-order hadronic vacuum polarisation contribution to the muon g−2, using ensembles with N f = 2+1 flavours of O(a) improved Wilson quarks generated by the CLS effort, with pion masses down to the physical value. We employ O(a) improved versions of the local and conserved vector currents to compute the contributions of the light, strange and charm quarks to (g − 2) µ , using the time-momentum representation. We perform a detailed investigation of the systematic effects arising from constraining the longdistance regime of the vector correlator. To this end we make use of auxiliary calculations in the iso-vector channel using distillation and the Lüscher formalism. Our results are corrected for finite-volume effects by computing the timelike pion form factor in finite and infinite volume. For certain parameter choices, the corrections computed in this way can also be confronted with results determined on different volumes. Currently, the overall precision of our results is limited by the uncertainties in the lattice scale.

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Towards extracting the timelike pion form factor on CLS twoflavour ensembles

Cited by 12 publications

References 17 publications

Rho resonance, timelike pion form factor, and implications for lattice studies of the hadronic vacuum polarization

Rho resonance, timelike pion form factor, and implications for lattice studies of the hadronic vacuum polarization

Lattice QCD study of the H dibaryon using hexaquark and two-baryon interpolators

The hadronic vacuum polarization contribution to $(g-2)_μ$ from $2+1$ flavours of O($a$) improved Wilson quarks

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