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We report on the measurement of the Central Exclusive Production of charged particle pairs $h^{+}h^{-}$ ($h = pi, K, p$) with the STAR detector at RHIC in proton-proton collisions at $sqrt{s} = 200$ GeV. The charged particle pairs produced in the reaction $ppto p^prime+h^{+}h^{-}+p^prime$ are reconstructed from the tracks in the central detector, while the forward-scattered protons are measured in the Roman Pot system. Differential cross sections are measured in the fiducial region, which roughly corresponds to the square of the four-momentum transfers at the proton vertices in the range $0.04~mbox{GeV}^2 < -t_1 , -t_2 < 0.2~mbox{GeV}^2$, invariant masses of the charged particle pairs up to a few GeV and pseudorapidities of the centrally-produced hadrons in the range $|eta|<0.7$. The measured cross sections are compared to phenomenological predictions based on the Double Pomeron Exchange (DPE) model. Structures observed in the mass spectra of $pi^{+}pi^{-}$ and $K^{+}K^{-}$ pairs are consistent with the DPE model, while angular distributions of pions suggest a dominant spin-0 contribution to $pi^{+}pi^{-}$ production. The fiducial $pi^+pi^-$ cross section is extrapolated to the Lorentz-invariant region, which allows decomposition of the invariant mass spectrum into continuum and resonant contributions. The extrapolated cross section is well described by 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 $t_1$ and $t_2$ enable 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 present particle spectra for charged hadrons $pi^pm, K^pm, p$ and $bar{p}$ from pp collisions at $sqrt{s}=200$ GeV measured for the first time at forward rapidities (2.95 and 3.3). The kinematics of these measurements are skewed in a way that prob
Heavy quarks (charm and beauty) are produced in hard-scattering processes and the study of their production in proton--proton (pp) collisions is an important test for calculations based on perturbative Quantum Chromodynamics (pQCD). Heavy-flavor prod
We report a new high-precision measurement of the mid-rapidity inclusive jet longitudinal double-spin asymmetry, $A_{LL}$, in polarized $pp$ collisions at center-of-mass energy $sqrt{s}=200$ GeV. The STAR data place stringent constraints on polarized
We report results on the total and elastic cross sections in proton-proton collisions at $sqrt{s}=200$ GeV obtained with the Roman Pot setup of the STAR experiment at the Relativistic Heavy Ion Collider (RHIC). The elastic differential cross section
We present measurements of the differential cross sections of inclusive $J/psi$ meson production as a function of transverse momentum ($p_{T}^{J/psi}$) using the $mu^{+}mu^{-}$ and $e^{+}e^{-}$ decay channels in proton+proton collisions at center-of-