Finite-volume and partial quenching effects in the magnetic polarizability of the neutron

Hall, Jonathan M. M.; Leinweber, Derek B.; Young, R.

doi:10.1103/physrevd.89.054511

Cited by 42 publications

(55 citation statements)

References 84 publications

(219 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The uniform background-field method [1][2][3] has a long history of use in lattice QCD to investigate and calculate quantities such as hadronic magnetic moments [2,[4][5][6], polarisabilities [4,[6][7][8][9], and the spatial distribution of quarks in a magnetic field [10]. Recently, it has been demonstrated that the background-field method introduces unphysical changes in the fermion energy when the Wilson quark formulation is used [11,12].…”

Section: Introductionmentioning

confidence: 99%

Pion in a uniform background magnetic field with clover fermions

2019

View full text Add to dashboard Cite

Background field methods provide an important nonperturbative formalism for the determination of hadronic properties which are complementary to matrix-element calculations. However, new challenges are encountered when utilising a fermion action exposed to additive mass renormalisations. In this case, the background field can induce an undesired field-dependent additive mass renormalisation that acts to change the quark mass as the background field is changed. For example, in a calculation utilising Wilson fermions in a uniform background magnetic field, the Wilson term introduced a field-dependent renormalisation to the quark mass which manifests itself in an unphysical increase of the neutral-pion mass for large magnetic fields. Herein, the clover fermion action is studied to determine the extent to which the removal of O(a) discretisation errors suppresses the field-dependent changes to the quark mass. We illustrate how a careful treatment of nonperturbative improvement is necessary to resolve this artefact of the Wilson term. Using the 32 3 × 64 dynamical-fermion lattices provided by the PACS-CS Collaboration we demonstrate how our technique suppresses the unphysical mass renormalisation over a broad range of magnetic field strengths.

show abstract

Section: Introductionmentioning

confidence: 99%

Pion in a uniform background magnetic field with clover fermions

2019

View full text Add to dashboard Cite

show abstract

“…[644][645][646][647][648][649] and Refs. therein, the main theoretical tools to address CS are 'hadronic' descriptions such as chiral perturbation theory, which provides a systematic expansion of the CS amplitude at low energies and low momenta, and dispersion relations which establish a direct link to experimental data.…”

Section: Overview Of Two-photon Physicsmentioning

confidence: 99%

Baryons as relativistic three-quark bound states

Eichmann

Sanchis-Alepuz

Williams

et al. 2016

Progress in Particle and Nuclear Physics

421

530

View full text Add to dashboard Cite

We review the spectrum and electromagnetic properties of baryons described as relativistic three-quark bound states within QCD. The composite nature of baryons results in a rich excitation spectrum, whilst leading to highly non-trivial structural properties explored by the coupling to external (electromagnetic and other) currents. Both present many unsolved problems despite decades of experimental and theoretical research. We discuss the progress in these fields from a theoretical perspective, focusing on nonperturbative QCD as encoded in the functional approach via Dyson-Schwinger and Bethe-Salpeter equations. We give a systematic overview as to how results are obtained in this framework and explain technical connections to lattice QCD. We also discuss the mutual relations to the quark model, which still serves as a reference to distinguish 'expected' from 'unexpected' physics. We confront recent results on the spectrum of non-strange and strange baryons, their form factors and the issues of two-photon processes and Compton scattering determined in the DysonSchwinger framework with those of lattice QCD and the available experimental data. The general aim is to identify the underlying physical mechanisms behind the plethora of observable phenomena in terms of the underlying quark and gluon degrees of freedom.

show abstract

“…As the loop is correlated with the quarks carrying the quantum numbers of the state only via gluon exchange, resolving a nontrivial signal requires high statistics and innovative methods. While there has been recent success in isolating the relevant disconnected-loop contributions in ground-state baryon matrix elements [3,4], challenges in isolating baryon excitations in lattice QCD [10,40,[45][46][47][48][49][50][51][52][53][54][55][56][57] render the resolution of disconnected contributions elusive.Here, we draw on partially-quenched chiral effective field theory [44,[58][59][60][61][62][63][64][65][66] to understand the relative weight of these disconnected contributions to the form factors in QCD. With this insight, one can test quantitatively whether the light-quark contribution to the magnetic form factor of the Λ(1405), calculated in lattice QCD, is consistent with a molecular KN description of the internal structure.…”

mentioning

confidence: 99%

Light-quark contributions to the magnetic form factor of the Λ(1405)

et al. 2017

View full text Add to dashboard Cite

In a recent study of the Λ(1405), the suppression of the strange-quark contribution to the magnetic form factor was interpreted as the discovery of a dominant antikaon-nucleon composition for this low-lying state. We confirm this result by calculating the light u-and d-quark contributions to the Λ(1405) magnetic form factor in lattice QCD in order to determine the extent to which their contributions support this exotic molecular description. Drawing on the recent graded-symmetry approach for the flavor-singlet components of the Λ(1405), the separation of connected and disconnected contributions is performed in both the flavor-octet and singlet representations. The relationship between light-quark contributions to the Λ(1405) magnetic form factor and the connected contributions of the nucleon magnetic form factors is established and compared with lattice calculations of the same quantities, confirming the KN molecular structure of the Λ(1405) in lattice QCD.Resolving and understanding the internal structure of hadronic excited states is an important contemporary problem in the field of nonperturbative QCD. While lattice QCD simulation methods are increasingly able to probe the chiral regime of ground state observables with unprecedented accuracy [1][2][3][4], the resolution of excited-baryon form factors is still at a very early stage [5][6][7][8][9][10].Interest in the Λ(1405) resonance has continued unabated for more than 50 years [10-44] because of its unusually low mass -lower even than the corresponding mass of the negative parity nucleon, despite containing a heavier strange quark. The unexpected position of the Λ(1405) in the spectrum has been explored in several studies, which typically indicate a significant contribution from a KN bound state . The πΣ channel also plays a nontrivial role. It is now widely agreed that there is a two-pole structure in this resonance region [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] stemming from attractive interactions in both the πΣ and KN channels. In making contact with results from lattice QCD [10,40,41], a description of the Λ(1405) over a range of quark masses has been developed [10,32,45], bridging constituent-quark ideas at heavy quark masses and the molecular KN dominance of the Λ(1405) at light quark masses.A recent lattice QCD study of the Λ(1405) reported evidence of a molecular KN structure [10]. There, the role of the strange quark was paramount in signaling the presence of a dominant KN structure. At heavier quark masses approaching the strange quark mass, the three quark flavors (u, d, s) are found to make approximately equal contributions to the magnetic form factor when their charges are set to unity. The underlying flavor symmetry is manifest. However, as the u and d quarks become light, flavor symmetry in the quark contributions to the magnetic form factor is found to be badly broken, and the strange-quark contribution drops by an order of magnitude from its maximum to a nearly vanishing value at the smallest quark mass. This feature h...

show abstract

Finite-volume and partial quenching effects in the magnetic polarizability of the neutron

Cited by 42 publications

References 84 publications

Pion in a uniform background magnetic field with clover fermions

Pion in a uniform background magnetic field with clover fermions

Baryons as relativistic three-quark bound states

Light-quark contributions to the magnetic form factor of the Λ(1405)

Contact Info

Product

Resources

About