An attempt to understand exclusive π
                     + electroproduction

Goloskokov, S. V.; Kroll, P.

doi:10.1140/epjc/s10052-009-1178-9

Cited by 188 publications

(341 citation statements)

References 77 publications

(213 reference statements)

Supporting

Mentioning

326

Contrasting

Order By: Relevance

“…The theoretical description of these processes is more complicated, and thus measurements that provide information about the reaction mechanism, e.g., tests of hard-soft factorization, are essential. In particular, the emerging transversity GPDs [114][115][116] may be accessed if dominance of the transverse cross section at small values of t <0.3 GeV 2 can be experimentally verified.…”

Section: D Spatial Mapping -Gpdsmentioning

confidence: 99%

Round table: Nucleon tomography. What can we do better today than Rutherford 100 years ago?

et al. 2017

View full text Add to dashboard Cite

Abstract. A survey is presented on the current status of 3D nucleon tomography. Several research frontiers are addressed that dominate modern physics from theory to current and future experiments. We have now a much more detailed spatial image of the nucleon thanks to various theoretical concepts and methods to describe its charge distribution and spin decomposition which are highlighted here. The progress of lattice computations of these quantities is reported and the prospects of what we can come to expect in the near future are discussed. Multi-dimensional maps of the nucleon's partonic structure appear now within reach of forthcoming experiments.

show abstract

Section: D Spatial Mapping -Gpdsmentioning

confidence: 99%

Round table: Nucleon tomography. What can we do better today than Rutherford 100 years ago?

et al. 2017

View full text Add to dashboard Cite

show abstract

“…The Goloskokov-Kroll (GK) GPD-based model [10,12] is a modified perturbative approach, incorporating the full pion electromagnetic form factor (as determined by fits to our F π data [29]) in the longitudinal channel and the H T transversity GPD dominating the transverse channel. The GK model is in good agreement with our R T data at −t min , but predicts too-flat of a t-dependence.…”

Section: B Comparison Of Various Models With the Datamentioning

confidence: 99%

“…For longitudinal photons with Q 2 > 10 GeV 2 and −t ≪ M 2 N , this theorem allows one to relate exclusive N (e, e ′ π ± )N observables to integrals over the quark flavor-dependent GPDs. Pseudoscalar meson-production observables not dominated by the pion pole term, such as σ T in exclusive π ± electroproduction, have also been identified as being especially sensitive to the chiral-odd transverse GPDs [9,10]. However, large higher-order corrections [11] have delayed the application of GPDs to pion electroproduction until recently.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Separated response functions in exclusive, forwardπ±electroproduction on deuterium

Huber¹,

Blok²,

Butuceanu³

et al. 2015

Phys. Rev. C

View full text Add to dashboard Cite

Background: Measurements of forward exclusive meson production at different squared four-momenta of the exchanged virtual photon, Q 2 , and at different four-momentum transfer, t, can be used to probe QCD's transition from meson-nucleon degrees of freedom at long distances to quark-gluon degrees of freedom at short scales. Ratios of separated response functions in π − and π + electroproduction are particularly informative. The ratio for transverse photons may allow this transition to be more easily observed, while the ratio for longitudinal photons provides a crucial verification of the assumed pole dominance, needed for reliable extraction of the pion form factor from electroproduction data.Purpose: Perform the first complete separation of the four unpolarized electromagnetic structure functions L/T /LT /T T in forward, exclusive π ± electroproduction on deuterium above the dominant resonances.Method: Data were acquired with 2.6-5.2 GeV electron beams and the HMS+SOS spectrometers in Jefferson Lab Hall C, at central Q 2 values of 0.6, 1.0, 1.6 GeV 2 at W =1.95 GeV, and Q 2 = 2.45 GeV 2 at W =2.22 GeV. There was significant coverage in φ and ǫ, which allowed separation of σL,T,LT,T T . 2Results: σL shows a clear signature of the pion pole, with a sharp rise at small −t. In contrast, σT is much flatter versus t. The longitudinal/transverse ratios evolve with Q 2 and t, and at the highest Q 2 = 2.45 GeV 2 show a slight enhancement for π − production compared to π + . The π − /π + ratio for transverse photons exhibits only a small Q 2 -dependence, following a nearly universal curve with t, with a steep transition to a value of about 0.25, consistent with s-channel quark knockout. The σT T /σT ratio also drops rapidly with Q 2 , qualitatively consistent with s-channel helicity conservation. The π − /π + ratio for longitudinal photons indicates a small isoscalar contamination at W =1.95 GeV, consistent with what was observed in our earlier determination of the pion form factor at these kinematics. Conclusions: The separated cross sections are compared to a variety of theoretical models, which generally describe σL but have varying success with σT . Further theoretical input is required to provide a more profound insight into the relevant reaction mechanisms for longitudinal and transverse photons, such as whether the observed transverse ratio is indeed due to a transition from pion to quark knockout mechanisms, and provide useful information regarding the twist-3 transversity generalized parton distribution, HT .

show abstract

“…In addition they provide a unique possibility to access "transversity" or chiralodd GPDs through measurements of different azimuthal moments of the cross section. In the handbag approach developed recently by Liuti and Goldstein [10] and Kroll and Goloskokov [11,12] the helicity amplitudes depend on hard partonic subprocess and the GPD and the beam spin asymmetries of exclusive pions combined with other spin and azimuthal asymmetries, which can provide a unique possibility to access the elusive transversity GPDs.…”

Section: Introductionmentioning

confidence: 99%

Structure and spin of the nucleon

Avakian

2014

EPJ Web of Conferences

View full text Add to dashboard Cite

Abstract.Parton distribution functions, describing longitudinal momentum, helicity and transversity distributions of quarks and gluons, have been recently generalized to account also for transverse degrees of freedom. Two new sets of more general distributions, Transverse Momentum Distributions and Generalized Parton Distributions, were introduced to describe transverse momentum and space distributions of partons. Great progress has been made since then in measurements of different Single Spin Asymmetries (SSAs) in semi-inclusive and hard exclusive processes providing access to TMDs and GPDs, respectively. Facilities world-wide involved in studies of the 3D structure of nucleon include HERMES, COMPASS, BELLE, BaBar, Halls A, B, and C at JLab, and PHENIX and STAR at RHIC (BNL). TMD studies in the Drell-Yan process are also becoming an important part of the program of hadron scattering experiments. Studies of TMDs are also among the main driving forces of the JLab 12-GeV upgrade project, several of the forward upgrade proposals of STAR and PHENIX at RHIC, and future facilities, such as the Electron Ion Collider (EIC), FAIR in Germany, and NICA in Russia. In this contribution we present an overview of the latest developments in studies of parton distributions and discuss newly released results, ongoing activities, as well as some future measurements.

show abstract

An attempt to understand exclusive π + electroproduction

Cited by 188 publications

References 77 publications

Round table: Nucleon tomography. What can we do better today than Rutherford 100 years ago?

Round table: Nucleon tomography. What can we do better today than Rutherford 100 years ago?

Separated response functions in exclusive, forwardπ±electroproduction on deuterium

Structure and spin of the nucleon

Contact Info

Product

Resources

About