Indication for π⁺π⁻ scattering in p + p collisions at GeV

Abstract

A ρ(770) 0 mass shift of about -40 MeV/c 2 was measured in p+p collisions at √ s N N = 200 GeV at RHIC. Previous mass shifts have been observed at CERN-LEBC-EHS and CERN-LEP. We will show that phase space does not account for the ρ(770) 0 mass shift measured at RHIC, CERN-LEBC-EHS and CERN-LEP and conclude that there are significant scattering interactions in p + p collisions.

Hadronic resonance production ind+Aucollisions atsNN=200Abelev1, Aggarwal2, Ahammed3 et al. 2008Phys. Rev. C635210View full textAdd to dashboardCite

“…All these explanations require an interaction, which implies a medium such as the one formed in A+A collisions. However, the ρ 0 mass shift measured in p+p collisions [3] can be described without a medium [35]. The ++ width and the * mass and width measured are in agreement with previous measurements [26].…”

“…Dynamical interactions with the surrounding matter, interference between various π + π − scattering channels, phase-space distortions due to the rescattering of pions forming ρ 0 , and Bose-Einstein correlations between ρ 0 decay daughters and pions in the surrounding matter were previously given as the possible explanations [3]. It has been proposed [35] that the mass shift observed in p+p collisions is due to ππ rescattering, which requires no medium. Since one also does not expect a medium to be formed in d+Au collisions, if dynamical interactions are also the explanation for the mass shift, then the rescattering of the ρ 0 with the surrounding particles must exist.…”

“…In p+p collisions, it has been proposed that the mass shift is due to ππ rescattering, even in the absence of a medium [35]. If this is the case, π + π − rescattering might regenerate the ρ 0 .…”

Baryon Resonances in the STAR Experiment at RHIC

“…Several explanations have been offered for the observed mass shift of the Δ ++ in d+Au, including dynamical interactions with the surrounding matter, distortions of the phase space due to re-scattering of the daughters, and Bose-Einstein correlations with pions in the surrounding matter [3]. For the mass shift observed in p + p it has been suggested that ππ re-scattering may be responsible since it does not require the presence of a medium [9]. Residual background in the case of the Σ(1385) comes mostly from the Ξ and Ξ, which have the same decay channels as the Σ(1385) and Σ(1385).…”

A Heavy Ion Fireball freeze-out Dipion Cocktail for Au-Au Collisions at root s =200GeV (Part 1)

“…Since we are projecting in p t this weighting will be an exponential function of the transverse mass divided by the temperature [6,[9][10][11][12][13].…”