Measurement of elastic Upsilon photoproduction at HERA

Journal article

Elastic ρ 0 photoproduction has been measured using the ZEUS detector at HERA. Untagged photoproduction events from ep interactions were used to measure the reaction γp→ρ 0 p(ρ 0)→π +π-) at photon-proton centre-of-mass energies between 60 and 80 GeV and |t|<0.5 GeV2, where t is the square of the four-momentum transferred at the proton vertex. The differential cross section dσ/d M ππ where M ππ is the invariant mass of the two pions, and the integrated cross section, σγp→ρ{variant}0ρ{variant}, are presented; the latter was measured to be 14.7±0.4 (stat.) ±2.4 (syst.)μb. The differential cross section dσ/dt has an approximately exponential shape; a fit of the type A t ′ exp(-b t ′ |t|+c t ′ t 2) yields a t-slope b t ′ =9.9±1.2 (stat.) ±1.4 (syst.) GeV-2. The results, when compared to low energy data, show a weak energy dependence of both σγp→ρ{variant}0p and of the t-slope. The ρ 0 is produced predominantly with transverse polarisation, demostrating that s-channel helicity conservation holds at these energies. © 1996 Springer-Verlag.

Authors: Breitweg, J; Derrick, M; Krakauer, D; Magill, S; Mikunas, D

• Publication status: Published
• Journal: Physics Letters B
• Volume: 437
• Issue: 3-4
• Pages: 432-444
• Publication date: 1998-10-08
• DOI: 10.1016/S0370-2693(98)01081-8
• EISSN: 1431-5858
• ISSN: 0370-2693
• Language: English