Measurement of exclusive π+π−π+π− and ρ0ρ0 meson photoproduction at HERA



Andreev, V, Baty, A, Baghdasaryan, A, Begzsuren, K, Belousov, A, Bolz, A, Boudry, V, Brandt, G, Britzger, D, Buniatyan, A
et al (show 129 more authors) (2020) Measurement of exclusive π+π−π+π− and ρ0ρ0 meson photoproduction at HERA. EUROPEAN PHYSICAL JOURNAL C, 80 (12).

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Abstract

Exclusive photoproduction of ρ0(770) mesons is studied using the H1 detector at the ep collider HERA. A sample of about 900,000 events is used to measure single- and double-differential cross sections for the reaction γp→π+π−Y. Reactions where the proton stays intact (mY=mp) are statistically separated from those where the proton dissociates to a low-mass hadronic system (mp<mY<10 GeV). The double-differential cross sections are measured as a function of the invariant mass mππ 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 Wγp. The phase space restrictions are 0.5≤mππ≤2.2 GeV, |t|≤1.5 GeV2, and 20≤Wγp≤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 mππ dependence with resonant and non-resonant contributions added at the amplitude level leads to a measurement of the ρ0(770) meson mass and width at mρ=770.8+2.6−2.7 (tot.) MeV and Γρ=151.3+2.7−3.6 (tot.) MeV, respectively. The model is used to extract the ρ0(770) contribution to the π+π− cross sections and measure it as a function of t and Wγp. In a Regge asymptotic limit in which one Regge trajectory α(t) dominates, the intercept α(t=0)=1.0654 +0.0098−0.0067 (tot.) and the slope α′(t=0)=0.233+0.067−0.074 (tot.) GeV−2 of the t dependence are extracted for the case mY=mp.

Item Type: Article
Depositing User: Symplectic Admin
Date Deposited: 12 Feb 2021 14:26
Last Modified: 09 May 2021 11:13
DOI: 10.1140/epjc/s10052-020-08587-3
Open Access URL: https://link.springer.com/article/10.1140%2Fepjc%2...
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URI: https://livrepository.liverpool.ac.uk/id/eprint/3115562