Determination of the ∑+ Timelike Electromagnetic Form Factors

• Based on data samples collected with the BESIII detector at the BEPCII collider, the process e+e- → Σ+Σ− (over bar) is studied at center -of -mass energies √s = 2.3960, 2.6454, and 2.9000 GeV. Using a fully differential angular description of the final state particles, both the relative magnitude and phase information of the Σ+ electromagnetic form factors in the timelike region are extracted. The relative phase between the electric and magnetic form factors is determined to be sin ΔΦ = -0.67 ± 0.29(stat) ± 0.18(syst) at √s  = 2.3960 GeV, AO = 55° ± 19°(stat) ± 14°(syst) at √s = 2.6454 GeV, and 78° ± 22°(stat) ± 9°(syst) at √s = 2.9000 GeV. For the first time, the phase of the hyperon electromagnetic form factors is explored in a wide range of four -momentum transfer. The evolution of the phase along with fourmomentum transfer is an important input for understanding its asymptotic behavior and the dynamics of baryons.

Subject headings

NATURVETENSKAP  -- Fysik -- Subatomär fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Subatomic Physics (hsv//eng)

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art (subject category)