How to measure the pion structure function at HERA

Holtmann, H.; Levman, G.; Nikolaev, N. N.; Szczurek, Antoni; Speth, J.

doi:10.1016/0370-2693(94)91392-7

Cited by 96 publications

(129 citation statements)

References 19 publications

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“…There exists a variety of models for the exact form of the pion flux [33][34][35][36][37][38][39][40] which typically leads to a ∼30 % spread in the predicted cross section according to Eq. (4).…”

Section: Cross Sections Definitionsmentioning

confidence: 99%

Exclusive $$\rho ^0$$ ρ 0 meson photoproduction with a leading neutron at HERA

et al. 2016

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A first measurement is presented of exclusive photoproduction of ρ 0 mesons associated with leading neutrons at HERA. The data were taken with the H1 detector in the years 2006 and 2007 at a centre-of-mass energy of √ s = 319 GeV and correspond to an integrated luminosity of 1.16 pb −1 . The ρ 0 mesons with transverse momenta p T < 1 GeV are reconstructed from their decays to charged pions, while leading neutrons carrying a large fraction of the incoming proton momentum, x L > 0.35, are detected in the Forward Neutron Calorimeter. The phase space of the measurement is defined by the photon virtuality Q 2 < 2 GeV 2 , the total energy of the photon-proton system 20 < W γ p < 100 GeV and the polar angle of the leading neutron θ n < 0.75 mrad. The cross section of the reaction γ p → ρ 0 nπ + is mea- † Deceased a e-mail: sschmitt@mail. Sciences, sured as a function of several variables. The data are interpreted in terms of a double peripheral process, involving pion exchange at the proton vertex followed by elastic photoproduction of a ρ 0 meson on the virtual pion. In the framework of one-pion-exchange dominance the elastic cross section of photon-pion scattering, σ el (γ π + → ρ 0 π + ), is extracted. The value of this cross section indicates significant absorptive corrections for the exclusive reaction γ p → ρ 0 nπ + .

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Section: Cross Sections Definitionsmentioning

confidence: 99%

Exclusive $$\rho ^0$$ ρ 0 meson photoproduction with a leading neutron at HERA

et al. 2016

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“…There are several parameterisations of the pion flux [50][51][52][53][54] and the one used here is taken from [51]. The details of the pion flux parameterisation are described in [7].…”

Section: Monte Carlo Simulations and Corrections To The Datamentioning

confidence: 99%

Measurement of Feynman- $$x$$ x spectra of photons and neutrons in the very forward direction in deep-inelastic scattering at HERA

Andreev¹,

Baghdasaryan²,

Begzsuren³

et al. 2014

Eur. Phys. J. C

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Measurements of normalised cross sections for the production of photons and neutrons at very small angles with respect to the proton beam direction in deep-inelastic ep scattering at HERA are presented as a function of the Feynman variable x F and of the centre-of-mass energy of the virtual photon-proton system W . transfer squared at the positron vertex 6 < Q 2 < 100 GeV 2 , of inelasticity 0.05 < y < 0.6 and of 70 < W < 245 GeV.To test the Feynman scaling hypothesis the W dependence of the x F dependent cross sections is investigated. Predictions of deep-inelastic scattering models and of models for hadronic interactions of high energy cosmic rays are compared to the measured cross sections.

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“…As discussed in section 2 the reggeon exchange contribution and decays of the ∆ resonances constitute a sizeable background to the pionic contribution especially at large transverse momenta of leading nucleons. The same peripheral processes are at work in the production of leading neutrons in electron deep inelastic scattering at HERA,where leading neutron tagged DIS is presently studied experimentally as the method of determination of the pion structure function [41,43,44]. The quality of the neutron tagging can be judged from the pion purity factor shown in fig.8, here we present the ratio R(z, t) defined as…”

Section: Non-pionic Background In the Production Of Leading Neutromentioning

confidence: 99%

Do the E866 Drell-Yan data change our picture of the chiral structure of the nucleon?

et al. 1999

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We revisit the evaluation of the pionic mechanism of theū −d-asymmetry in the proton structure function. Our analysis is based on the extended AGK unitarity relation between contributions of different mechanisms to the inclusive particle production and the total photoabsorption cross-section (i.e. the proton structure function). We reanalyze the role of isovector reggeons in inclusive production of nucleons and Delta isobars in hadronic reactions. We find rather large contribution of reggeonexchange induced production of Delta isobars. This leaves much less room for the pion-exchange induced mechanism of ∆ production and provides a constraint on the πN ∆ form factor. The production of leading pions in proton-proton collisions at ISR puts additional constraints on the πN N vertex form factors. An extension of the AGK-rules to reggeon exchange suggests a negligible contribution to the proton structure function from DIS off the exchanged ρ, a2 reggeons. All these constraints are used then to estimate the pion content of the nucleon and allow to calculate parameter-free the x-dependence ofd −ū. We discuss the violation of the Gottfried Sum Rule andd-ū asymmetry and compare to the one obtained from the E866 experiment at Fermilab. We estimate the background to the pion structure function being determined by the ZEUS and H1 collaborations at HERA from leading neutron experiments.

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How to measure the pion structure function at HERA

Cited by 96 publications

References 19 publications

Exclusive $$\rho ^0$$ ρ 0 meson photoproduction with a leading neutron at HERA

Exclusive $$\rho ^0$$ ρ 0 meson photoproduction with a leading neutron at HERA

Measurement of Feynman- $$x$$ x spectra of photons and neutrons in the very forward direction in deep-inelastic scattering at HERA

Do the E866 Drell-Yan data change our picture of the chiral structure of the nucleon?

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