COMPASS measurement of hard exclusive π0 muoproduction cross-section

One of the goals of the COMPASS experimental program is the measurement of exclusive processes. The exclusive processes, such as Deep Virtual Compton Scattering (DVCS) or Hard Exclusive Meson Production, are important inputs for constraining the General Parton Distributions (GPDs). Exclusive π 0 production is the main source of background for DVCS process, while it provides important information on chiral-odd GPDs. The dedicated GPD program started with a one month pilot run in 2012, followed by two full years of data taking in 2016-2017, using 160 GeV/c positive and negative muon beams, a liquid hydrogen target and new detectors such as a recoil proton detector and a large-angle electromagnetic calorimeter. Our results of the exclusive π0 production from the 2012 pilot run, recently submitted to publication, are presented. Using average of both μ + and μ − data, the γ*p cross section is extracted as a function of the squared four-momentum transfer t, and of the azimuthal angle ϕ between the scattering plane and the π 0 production plane. The average kinematics of the measurement are ⟨Q 2⟩ = 2.0 (GeV/c)2, ⟨ν⟩ = 12.8 GeV, ⟨xB ⟩ = 0.093, and ⟨−t⟩ = 0.256 (GeV/c)2. A comparison of our results with the phenomenological Goloskokov-Kroll model are shown. Prospect are given on upcoming results of the 2016/17 measurement.