The STAR experiment at the Relativistic Heavy Ion Collider (RHIC) performs
studies of diffractive processes with the focus on the exclusive production of
particles in central range of rapidity. In 2015 STAR collected 18~pb$^{-1}$
of data in polarized proton-proton collisions at $\sqrt{s}$~=~200~GeV to
measure Central Exclusive Production (CEP) process $pp\to pXp$
through Double Pomeron Exchange (DPE) mechanism, which is
expected to be dominant at this center-of-mass energy.

The intact protons moving inside the RHIC beam pipe after the collision were measured
in Roman Pot detectors. The CEP events were identified using transverse momentum balance
of the central diffractive system measured in the Time Projection Chamber (TPC)
and of the forward protons measured in the Roman Pots. With the use of ionization energy
loss in the TPC, d$E$/d$x$, as well as velocity measured with the Time-Of-Flight detector (TOF),
it was possible to identify various production channels in $pp\to pXp$ reaction.

We shall present preliminary results on exclusive production of two opposite-charge particles
($\pi^{+}\pi^{-}$, $K^{+}K^{-}$, $p\bar{p}$) in midrapidity region with small squared
four-momentum transfer of forward protons, $0.03\lesssim|t_{1}|,|t_{2}|\lesssim0.2~(\textrm{GeV}/c)^{2}$.