%0 Conference Paper
%A Bolz, Arthur
%T Exclusive π<sup>+</sup> π<sup>−</sup> and ρ<sup>0</sup> Meson Photoproduction at HERA
%I DESY
%M PUBDB-2022-07877
%D 2022
%X Exclusive photoproduction of ρ<sup>0</sup>(770) mesons is studied using the H1 detector at the ep collider HERA. A sample of about 900000 events is used to measure single- and double-differential cross sections for the reaction γp→π<sup>+</sup>π<sup>−</sup>Y. Reactions where the proton stays intact (m<sub>Y</sub>=m<sub>p</sub>) are statistically separated from those where the proton dissociates to a low-mass hadronic system (m<sub>p</sub> <  m<sub>Y</sub>  <  10 GeV). The double-differential cross sections are measured as a function of the invariant mass m<sub>ππ</sub> of the decay pions and the squared 4-momentum transfer t at the proton vertex. The measurements are presented in various bins of the photon-proton collision energy W<sub>γp</sub>. The phase space restrictions are 0.5 <  m<sub>ππ</sub> <  2.2 GeV, |t| <  1.5 GeV<sup>2</sup>, and 20 <  W<sub>γp</sub> <  80 GeV. Cross section measurements are presented for both elastic and proton-dissociative scattering. The observed cross section dependencies are described by analytic functions. Parametrising the m<sub>ππ</sub> dependence with resonant and non-resonant contributions added at the amplitude level leads to a measurement of the ρ<sup>0</sup>(770) meson mass and width at m<sub>ρ</sub>=770.8<sup>+2.6</sup><sub>−2.7</sub> (tot.) MeV and Γ<sub>ρ</sub>=151.3<sup>+2.7</sup><sub>−3.6</sub> (tot.) MeV, respectively. The model is used to extract the ρ<sup>0</sup>(770) contribution to the π<sup>+</sup>π<sup>−</sup> cross sections and measure it as a function of t and W<sub>γp</sub>. In a Regge asymptotic limit in which one Regge trajectory α(t) dominates, the intercept α(t=0)=1.0654<sup>+0.0098</sup><sub>−0.0067</sub> (tot.) and the slope α′(t=0)=0.233<sup>+0.067</sup><sub>−0.074</sub> (tot.) GeV<sup>−2</sup> of the t dependence are extracted for the case m<sub>Y</sub>=m<sub>p</sub>. Eur.Phys.J.C80 (2020), 1189 [arxiv:2005.14471]
%B Lepton-Photon 2021
%C 10 Jan 2022 - 14 Jan 2022, Manchester (UK)
Y2 10 Jan 2022 - 14 Jan 2022
M2 Manchester, UK
%F PUB:(DE-HGF)24
%9 Poster
%U https://bib-pubdb1.desy.de/record/490642