Separated Response Function Ratios in Exclusive, Forward<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mi>π</mml:mi><mml:mo>±</mml:mo></mml:msup></mml:math>Electroproduction

Huber, G. M.; Blok, H. P.; Butuceanu, C.; Gaskell, D.; Horn, T.; Mack, D.; Abbott, D.; Aniol, K.; Anklin, H.; Armstrong, Christopher; Arrington, J.; Assamagan, K.; Avery, S.; Baker, O. K.; Barrett, B.; Beise, E. J.; Bochna, C.; Boeglin, W.; Brash, E. J.; Breuer, H.; Cc, Chang; Chant, N. S.; Christy, M. E.; Dunne, J.; Eden, T.; Ent, R.; Fenker, H.; Gibson, E. F.; Gilman, R.; Gustafsson, K.; Hinton, W.; Holt, R. J.; Jackson, H. E.; Jin, S.; Jones, M.; Keppel, C.; Kim, P. H.; Kim, W.; P, King; Klein, A.; Koltenuk, D.; Kovaltchouk, V.; Liang, M.; Liu, J.; Lolos, G. J.; Lung, A.; Margaziotis, D. J.; Markowitz, P.; Matsumura, Akihiko; McKee, D.; Meekins, D.; Mitchell, J.; Miyoshi, T.; Mkrtchyan, H.; Mueller, B.; Niculescu, G.; Niculescu, I.; Okayasu, Y.; Pentchev, L.; Perdrisat, C. F.; Pitz, D.; Potterveld, D. H.; Punjabi, V.; Qin, L. M.; Reimer, P. E.; Reinhold, J.; Roche, J.; Roos, P.G.; Sarty, A. J.; Shin, I. K.; Smith, G. R.; Stepanyan, S.; Tang, L.; Tadevosyan, V.; Tvaskis, V.; Meer, R. L. J. van der; Vansyoc, K.; Westrum, Derek van; Vidakovic, S.; Volmer, J.; Vulcan, W.; Warren, G.; Wood, S. A.; Xu, Chang; Yan, Chao; Wenheng, Zhao; Zheng, X.; Zihlmann, B.

doi:10.1103/physrevlett.112.182501

Cited by 8 publications

(8 citation statements)

References 21 publications

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“…The dominance of the t-channel process in σ L was verified in Ref. [82] through the charged-pion longitudinal cross-section ratios, R L = σ L [n(e, e ′ π − )p]/σ L [p(e, e ′ π + )n], obtained with a deuterium target. The tchannel diagram is purely isovector and so any isoscalar background contributions, like b 1 (1235) to the t channel, will dilute the ratio.…”

Section: Importance and Nature Of The Pion Within The Standard Modelmentioning

confidence: 77%

The pion: an enigma within the Standard Model

Horn

Roberts

2016

J. Phys. G: Nucl. Part. Phys.

189

219

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Quantum Chromodynamics (QCD) is the strongly interacting part of the Standard Model. It is supposed to describe all of nuclear physics; and yet, almost fifty years after the discovery of gluons and quarks, we are only just beginning to understand how QCD builds the basic bricks for nuclei: neutrons and protons, and the pions that bind them together. QCD is characterised by two emergent phenomena: confinement and dynamical chiral symmetry breaking (DCSB). They have far-reaching consequences, expressed with great force in the character of the pion; and pion properties, in turn, suggest that confinement and DCSB are intimately connected. Indeed, since the pion is both a Nambu-Goldstone boson and a quark-antiquark bound-state, it holds a unique position in Nature and, consequently, developing an understanding of its properties is critical to revealing some very basic features of the Standard Model. We describe experimental progress toward meeting this challenge that has been made using electromagnetic probes, highlighting both dramatic improvements in the precision of charged-pion form factor data that have been achieved in the past decade and new results on the neutral-pion transition form factor, both of which challenge existing notions of pion structure. We also provide a theoretical context for these empirical advances, which begins with an explanation of how DCSB works to guarantee that the pion is unnaturally light; but also, nevertheless, ensures that the pion is the best object to study in order to reveal the mechanisms that generate nearly all the mass of hadrons. In canvassing advances in these areas, our discussion unifies many aspects of pion structure and interactions, connecting the charged-pion elastic form factor, the neutral-pion transition form factor and the pion's leading-twist parton distribution amplitude. It also sketches novel ways in which experimental and theoretical studies of the charged-kaon electromagnetic form factor can provide significant contributions. Importantly, it appears that recent predictions for the large-Q 2 behaviour of the chargedpion form factor can be tested by experiments planned at the upgraded 12 GeV Jefferson Laboratory. Those experiments will extend precise charged-pion form factor data up to momentum transfers that it now appears may be large enough to serve in validating factorisation theorems in QCD. If so, they may expose the transition between the nonperturbative and perturbative domains and thereby reach a goal that has driven hadro-particle physics for around thirty-five years.Keywords: Abelian anomaly, confinement, dynamical chiral symmetry breaking, elastic and transition form factors, π-meson, K-meson, non-perturbative QCD, parton distribution amplitudes and functions The pion: an enigma within the Standard Model 2. Form factors: experimental history, current status, and futureForm factors are of primary importance in hadron physics because they provide Poincaré-invariant information about the nonpointlike nature of QCD's observable bound-states, and the d...

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Section: Importance and Nature Of The Pion Within The Standard Modelmentioning

confidence: 77%

The pion: an enigma within the Standard Model

Horn

Roberts

2016

J. Phys. G: Nucl. Part. Phys.

189

219

View full text Add to dashboard Cite

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“…Measurements over a range of −t are essential as part of the model validation process. The JLab 6 GeV experiments were instrumental in establishing the reliability of this technique up to Q 2 = 2.45 GeV 2 [23,38,39,[179][180][181][182][183][184], and extensive further tests are planned as part of JLab experiment E12-19-006.…”

Section: Meson Form Factorsmentioning

confidence: 99%

Revealing the structure of light pseudoscalar mesons at the Electron-Ion Collider

Arrington,

Gayoso,

Barry

et al. 2021

Preprint

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How the bulk of the Universe's visible mass emerges and how it is manifest in the existence and properties of hadrons are profound questions that probe into the heart of strongly interacting matter. Paradoxically, the lightest pseudoscalar mesons appear to be the key to the further understanding of the emergent mass and structure mechanisms. These mesons, namely the pion and kaon, are the Nambu-Goldstone boson modes of QCD. Unravelling their partonic structure and the interplay between emergent and Higgs-boson mass mechanisms is a common goal of three interdependent approaches -continuum QCD phenomenology, lattice-regularised QCD, and the global analysis of parton distributions -linked to experimental measurements of hadron structure. Experimentally, the foreseen electron-ion collider will enable a revolution in our ability to study pion and kaon structure, accessed by scattering from the "meson cloud" of the proton through the Sullivan process. With the goal of enabling a suite of measurements that can address these questions, we examine key reactions to identify the critical detector system requirements needed to map tagged pion and kaon cross sections over a wide range of kinematics. The excellent prospects for extracting pion structure function and form factor data are shown, and similar prospects for kaon structure are discussed in the context of a worldwide programme. Successful completion of the programme outlined herein will deliver deep, far-reaching insights into the emergence of pions and kaons, their properties, and their role as QCD's Goldstone boson modes.

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“…As a consequence, there are uncertainties associated with the off-shellness of the struck pion and the consequent extrapolation to the physical pion mass pole, which leads to uncertainties in the extraction of the form factor. The errors appear to be under control in the most recent determinations of F π Collaboration at JLab [31,32], as shown in the subsequent analysis [33]. Therefore, as spacelike input (7) we have used the values [31,32]…”

Section: Input In the Extremal Problemmentioning

confidence: 99%

“…The experimental information available on the pion arXiv:1810.09265v2 [hep-ph] 24 Dec 2018 form factor is very rich. This quantity was measured at spacelike values Q 2 > 0 with increasing precision from electron-pion scattering [22] and pion electro-production from nucleons [23][24][25][26][27][28][29][30][31][32], the most precise being the recent results of the JLab collaboration [31][32][33]. On the timelike axis, for t ≥ 4m 2 π , where the form factor is complex, its modulus has been measured from the cross section of the process e + e − → π + π − [34]- [46] and, using isospin symmetry, from the τ → ππντ decay [47]- [51].…”

Section: Introductionmentioning

confidence: 99%

Pion electromagnetic form factor at high precision with implications to aμππ and the onset of perturbative QCD

2018

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We extend recently developed methods used for determining the electromagnetic charge radius and a ππ µ to obtain a determination of the electromagnetic form factor of the pion, F V π (t), in several significant kinematical regions, using a parametrization-free formalism based on analyticity and unitarity, with the inclusion of precise inputs from both timelike and spacelike regions. On the unitarity cut, below the first inelastic threshold, we use the precisely known phase of the form factor, known from ππ elastic scattering via the Fermi-Watson theorem, and above the inelastic threshold a conservative integral condition on the modulus. We also use as input the experimental values of the modulus at several energies in the elastic region, where the data from e + e − → π + π − and τ hadronic decays are mutually consistent, as well as the most recent measurements at spacelike momenta. The experimental uncertainties are implemented by Monte Carlo simulations. At spacelike values Q 2 = −t > 0 near the origin, our predictions are consistent and significantly more precise than the recent QCD lattice calculations. The determinations at larger Q 2 confirm the late onset of perturbative QCD for exclusive quantities. From the predictions of |F V π (t)| 2 on the timelike axis below 0.63 GeV, we obtain the hadronic vacuum polarization (HPV) contribution to the muon anomaly, a ππ µ | ≤0.63 GeV = (132.97 ± 0.70) × 10 −10 , using input from both e + e − annihilation and τ decay, and a ππ µ | ≤0.63 GeV = (132.91 ± 0.76) × 10 −10 using only e + e − input. Our determinations can be readily extended to obtain such contributions in any interval of interest lying between 2mπ and 0.63 GeV.PACS numbers:

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Separated Response Function Ratios in Exclusive, Forwardπ±Electroproduction

Cited by 8 publications

References 21 publications

The pion: an enigma within the Standard Model

The pion: an enigma within the Standard Model

Revealing the structure of light pseudoscalar mesons at the Electron-Ion Collider

Pion electromagnetic form factor at high precision with implications to aμππ and the onset of perturbative QCD

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