XXVIII International Workshop on Deep-Inelastic Scattering and Related Subjects

Recent results on Central Exclusive Production with the STAR detector

14 Apr 2021, 12:33

18m

Virtual (Stony Brook, NY)

Contributed Talk Small-x, Diffraction and Vector Mesons Small-x, Diffraction and Vector Mesons

Speaker

Rafal Sikora (AGH University of Science and Technology)

Description

We present results on the Central Exclusive Production of charged particle pairs $h^{+}{h}^{-}$ ($h=\pi ,K,p$) obtained in the STAR experiment at RHIC in proton-proton collisions at center-of-mass energy of $\sqrt{s}=200$ GeV. All final-state particles of the process $pp\to p^{\prime }+h^{+}{h}^{-}+p^{\prime }$ were reconstructed, including forward-scattered protons detected in the Roman Pot system. As a result, the Double Pomeron Exchange (DPE) events were selected and the non-exclusive backgrounds were efficiently rejected.

Differential fiducial cross sections were measured as functions of observables related to the central hadronic final state and to the forward-scattered protons. The measured cross sections were compared to phenomenological predictions based on the DPE model. Structures observed in the mass spectra of ${\pi }^{+}{\pi }^{-}$ and $K^{+}{K}^{-}$ pairs were found consistent with the DPE model, while angular distributions of pions suggested a dominant spin-0 contribution to ${\pi }^{+}{\pi }^{-}$ production.

For ${\pi }^{+}{\pi }^{-}$ production, the fiducial cross section was extrapolated to the Lorentz-invariant region and was successfully modeled assuming the continuum production and at least three resonances, the $f_0(980)$, $f_2(1270)$, and $f_0(1500)$, with a possible small contribution from the $f_0(1370)$.
Fits to the extrapolated differential cross section as a function of squared four-momentum transfers in proton vertices enabled extraction of the exponential slope parameters in several bins of the invariant mass of ${\pi }^{+}{\pi }^{-}$ pairs. These parameters are sensitive to the size of the interaction region.

We also present preliminary results on the measurement of the same physics process at higher $\sqrt{s}=510$ GeV. The data demonstrate features similar to those observed at $\sqrt{s}=200$ GeV.

Presentation materials

DIS2021_RafalSikora.pdf

Youtube Link