Measurement of the Spin-Density Matrix Elements in Exclusive Electroproduction of rho^0 Mesons at HERA

Abstract

Exclusive electroproduction of rho^0 mesons has been measured using the ZEUS detector at HERA in two Q^2 ranges, 0.25<Q^2<0.85 GeV^2 and 3<Q^2<30 GeV^2. The low-Q^2 data span the range 20<W<90 GeV; the high-Q^2 data cover the 40<W<120 GeV interval. Both samples extend up to four-momentum transfers of |t|=0.6 GeV^2. The distribution in the azimuthal angle between the positron scattering plane and the rho^0 production plane shows a small but significant violation of s-channel helicity conservation, corresponding to the production of longitudinally polarised (i.e. helicity zero) rho^0 mesons from transverse photons. Measurements of the 15 combinations of spin-density matrix elements which completely define the angular distributions are presented and discussed.

arXiv comment32 pages, 8 figures. This version has been accepted by The European Physics Journal C and incorporates the referee's comments

References in corpus (1)

• Exclusive Production of Neutral Vector Mesons at the Electron-Proton Collider HERA

Cited by in corpus (44)

• Generalized Parton Distributions
• The role of the quark and gluon GPDs in hard vector-meson electroproduction
• Deeply virtual Compton scattering at small x_B and the access to the GPD H
• Exclusive electroproduction of J/psi mesons at HERA
• Vector meson electroproduction at small Bjorken-x and generalized parton distributions
• Towards a fitting procedure for deeply virtual Compton scattering at next-to-leading order and beyond
• Diffractive Electroproduction of rho and phi Mesons at HERA
• Diffractive Vector Meson Production at HERA: from Soft to Hard QCD
• Deep inelastic leptoproduction of spin-one hadrons
• Partial-wave analysis of two-hadron fragmentation functions
• Exclusive electroproduction of $\varphi$ mesons at HERA
• Q^2 dependence of diffractive vector meson electroproduction
• Study of deep inelastic inclusive and diffractive scattering with the ZEUS forward plug calorimeter
• The Hadronic Final State at HERA
• Dissociation of virtual photons in events with a leading proton at HERA
• A phenomenological study of helicity amplitudes of high energy exclusive leptoproduction of the rho meson
• Sum rules and dualities for generalized parton distributions: is there a holographic principle?
• Spin Density Matrix Elements in Exclusive rho^0 Electroproduction on 1H and 2H Targets at 27.5 GeV Beam Energy
• Exclusive ${\rho }^0$ meson electroproduction from hydrogen at CLAS
• Saturation effects in exclusive rhoT, rhoL meson electroproduction
• Coherent pion production by neutrinos on nuclei
• Deeply Virtual Compton Scattering at a Proposed High-Luminosity Electron-Ion Collider
• Vector meson production from a polarized nucleon
• Genuine twist 3 in exclusive electroproduction of transversely polarized vector mesons
• Deep inelastic inclusive and diffractive scattering at $Q^2$ values from 25 to 320 GeV${}^2$ with the ZEUS forward plug calorimeter
• A measurement of the t dependence of the helicity structure of diffractive rho meson electroproduction at HERA
• Vector meson's spin alignments in high energy reactions
• Double spin asymmetry in exclusive rho^0 muoproduction at COMPASS
• Ratios of Helicity Amplitudes for Exclusive rho-0 Electroproduction
• Exclusive rho^0 muoproduction on transversely polarised protons and deuterons
• Probing the transverse spin of quarks in deep inelastic scattering
• Production of Polarized Vector Mesons off Nuclei
• On hard electroproduction of mesons: helicity flip amplitudes with tensor gluon contributions
• Exclusive electroproduction of two pions at HERA
• Electroproduction of vector mesons - factorization of end-point contributions
• Effects of Longitudinal Photons
• Production of orbitally excited vector mesons in diffractive DIS
• Helicity in diffractive vector-meson production
• Experimental Results on the Diffractive Production of Light Vector Mesons at HERA
• Factorization of the Q^2 dependence in electroproduction of vector mesons
• Anomalous f_1 exchange in vector meson photoproduction asymmetries
• Evidence for Quark Spin-flip in Pomeron Exchange
• Spin Physics at Compass
• Diffraction at HERA and Prospects with H1