Excited state contamination in nucleon structure calculations

Green, Jeremy R.; Krieg, Stefan; Negele, John W.; Pochinsky, Andrew; Syritsyn, Sergey

doi:10.22323/1.139.0157

Cited by 15 publications

(21 citation statements)

References 11 publications

(12 reference statements)

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“…The most straightforward strategy to address this problem is to include the first excitation into the fit ansatz for R(t, t s ) (see ref. [26]) or to investigate larger values of t and t s [27].…”

Section: R(t T S )mentioning

confidence: 99%

Nucleon axial charge in lattice QCD with controlled errors

et al. 2012

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We report on our calculation of the nucleon axial charge gA in QCD with two flavours of dynamical quarks. A detailed investigation of systematic errors is performed, with a particular focus on contributions from excited states to three-point correlation functions. The use of summed operator insertions allows for a much better control over such contamination. After performing a chiral extrapolation to the physical pion mass, we find gA = 1.223 ± 0.063 (stat) +0.035 −0.060 (syst), in good agreement with the experimental value.

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Section: R(t T S )mentioning

confidence: 99%

Nucleon axial charge in lattice QCD with controlled errors

et al. 2012

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“…In general, excited states can cause significant systematic errors in three-point functions and hadron matrix elements [23]. We compute our form factor values as averages of three central points in the plateaus.…”

mentioning

confidence: 99%

Lattice calculation of composite dark matter form factors

et al. 2013

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Composite dark matter candidates, which can arise from new strongly-coupled sectors, are wellmotivated and phenomenologically interesting, particularly in the context of asymmetric generation of the relic density. In this work, we employ lattice calculations to study the electromagnetic form factors of electroweak-neutral dark-matter baryons for a three-color, QCD-like theory with N f = 2 and 6 degenerate fermions in the fundamental representation. We calculate the (connected) charge radius and anomalous magnetic moment, both of which can play a significant role for direct detection of composite dark matter. We find minimal N f dependence in these quantities. We generate mass-dependent cross-sections for dark matter-nucleon interactions and use them in conjunction with experimental results from XENON100, excluding dark matter candidates of this type with masses below 10 TeV.PACS numbers: 11.10. Hi, 11.15.Ha, 95.35.+d Introduction Experimental bounds on the interaction of the dark matter with Standard-Model (SM) particles have strengthened by many orders of magnitude in recent years. In particular, dark-matter particles cannot have SMstrength couplings to electroweak gauge bosons, based on direct-detection constraints [1, 2]. At the same time, there is a strong motivation for the dark matter to couple to the SM in some way for the purpose of relic density generation, either as a thermal relic via the so-called "WIMP miracle" (see [3] for a recent review) or through an asymmetric scenario which may be related to the creation of baryon asymmetry [4][5][6][7][8][9][10][11]. Construction of dark matter models thus requires a careful balance between the presence and absence of dark-sector interactions with the SM.Composite dark matter models provide a simple mechanism for attaining this balance, one which can lead to interesting and unique phenomenology. By hypothesizing a new, confining gauge force in the dark sector, an electroweak-neutral composite dark matter candidate can be constructed as a bound state of electroweak-charged constituents. In this way, electroweak interactions can be active in the early Universe for the generation of relic density, but only neutral bound states survive to the present day. Electroweak coupling to the constituents is still possible, leading to form-factor suppressed interactions with the neutral composites. They can be roughly estimated from QCD analogs, but in general can be determined quantitatively only by lattice calculations.In this paper, we consider an underlying SU (3) gauge theory with fermions in the fundamental representation, but

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“…This yields improved asymptotic behaviour [3,4], with the leading excited-state contaminants decaying as Te −∆E min T . Other approaches such as various forms of multistate fits [5][6][7][8][9][10][11] and the use of a variational basis of interpolating operators [12][13][14][15] have also been explored. Besides excited states, important systematics include the following:…”

Section: Arxiv:14124637v1 [Hep-lat] 15 Dec 2014mentioning

confidence: 99%

“…However, this discrepancy persisted as pion masses were reduced. Studies of contributions from excited states have found large effects [5,10,15,18], and that by reducing them and using relatively light pion masses, much of the gap between lattice calculations and experiment could be closed. This is displayed in Fig.…”

Section: Electromagnetic Form Factorsmentioning

confidence: 99%

Hadron structure from lattice QCD

Green¹

2016

AIP Conference Proceedings

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Abstract. Recent progress in lattice QCD calculations of nucleon structure will be presented. Calculations of nucleon matrix elements and form factors have long been difficult to reconcile with experiment, but with advances in both methodology and computing resources, this situation is improving. Some calculations have produced agreement with experiment for key observables such as the axial charge and electromagnetic form factors, and the improved understanding of systematic errors will help to increase confidence in predictions of unmeasured quantities. The long-omitted disconnected contributions are now seeing considerable attention and some recent calculations of them will be discussed.

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Excited state contamination in nucleon structure calculations

Cited by 15 publications

References 11 publications

Nucleon axial charge in lattice QCD with controlled errors

Nucleon axial charge in lattice QCD with controlled errors

Lattice calculation of composite dark matter form factors

Hadron structure from lattice QCD

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