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We repormore » t high-precision measurements of the longitudinal double-spin asymmetry, $A_{LL}$, for midrapidity inclusive jet and dijet production in polarized $pp$ collisions at a center-of-mass energy of $\sqrt{s}=200\mathrm{GeV}$. The new inclusive jet data are sensitive to the gluon helicity distribution, $\mathrm{\Delta }g(x,Q^2)$, for gluon momentum fractions in the range from $x\simeq 0.05$ to $x\simeq 0.5$, while the new dijet data provide further constraints on the $x$ dependence of $\mathrm{\Delta }g(x,Q^2)$. The results are in good agreement with previous measurements at $\sqrt{s}=200\mathrm{GeV}$ and with recent theoretical evaluations of prior world data. Our new results have better precision and thus strengthen the evidence that $\mathrm{\Delta }g(x,Q^2)$ is positive for $x>0.05$.« less

Abstract. √s = 0.9 and 1.96 TeV in the Collider Detector at Fermilab has been measured. Events with exactly two particles with opposite charge, in |η(π)| < 1.3, with no other particles detected in |η(π)| < 5.9, were selected. We require the central π+π- state to have rapidity |y(ππ)| < 1. The data are expected to be dominated by double pomeron exchange. Therefore, the quantum numbers of the central state are constrained. The data he results are valuable for light hadron spectroscopy, and for erstanding the nature of the pomeron in a region between non-perturbative and perturbative QCD.

Exclusive $$\pi^{=}\pi^{-}$$ production in proton-antiproton collisions at $$\sqrt{s}$$ = 0.9 and 1.96 TeV in the Collider Detector at Fermilab has been measured. We select events with two particles with opposite charge in pseudorapidity region -1.3 < $$\eta$$ < 1.3 with no other particles detected in -5.9 < $$\eta$$ < 5.9. Particles are assumed to be pions. The $$\pi^{+}\pi^{-}$$system is required to have rapidity -1.0 < $$y$$ < 1.0. The data are expected to be dominated by the double pomeron exchange mechanism. Therefore, the quantum numbers of the central state are constrained. The data extend up to dipion mass M($$\pi^{+}\pi^{-}$$) =more » 5000 MeV/$c^2$. Resonance structures consistent with $$f_0$$ and $$f_2$$(1270) mesons are visible. The results are valuable for light hadron spectroscopy and for providing information about the nature of the pomeron in a region between non-perturbative and perturbative quantum chromodynamics« less