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STAR's measurements of directed flow (v1) around midrapidity for π±, K±, K0S, p and p¯ in Au + Au collisions at $\sqrtsNN = 200$ GeV are presented. A negative v1(y) slope is observed for most of produced particles (π±, K±, K0S and p¯). The proton v1(y) slope is found to be much closer to zero compared to antiprotons. A sizable difference is seen between v1 of protons and antiprotons in 5-30% central collisions. The v1 excitation function is presented. Comparisons to model calculations (RQMD, UrQMD, AMPT, QGSM with parton recombination, and a hydrodynamics model with a tilted source) are made. Anti-flow alone cannot explain the centrality dependence of the difference between the v1(y) slopes of protons and antiprotons.
STAR's measurements of directed flow (v1) around midrapidity for π±, K±, K0S, p and p¯ in Au + Au collisions at $\sqrtsNN = 200$ GeV are presented. A negative v1(y) slope is observed for most of produced particles (π±, K±, K0S and p¯). In 5-30% central collisions a sizable difference is present between the v1(y) slope of protons and antiprotons, with the former being consistent with zero within errors. The v1 excitation function is presented. Comparisons to model calculations (RQMD, UrQMD, AMPT, QGSM with parton recombination, and a hydrodynamics model with a tilted source) are made. For those models which have calculations of v1 for both pions and protons, none of them can describe v1(y) for pions and protons simultaneously. The hydrodynamics model with a tilted source as currently implemented cannot explain the centrality dependence of the difference between the v1(y) slopes of protons and antiprotons.
We report a high precision measurement of the transverse single spin asymmetry AN at the center of mass energy √s=200 GeV in elastic proton–proton scattering by the STAR experiment at RHIC. The AN was measured in the four-momentum transfer squared t range 0.003⩽|t|⩽0.035 (GeV/c)2, the region of a significant interference between the electromagnetic and hadronic scattering amplitudes. The measured values of AN and its t-dependence are consistent with a vanishing hadronic spin-flip amplitude, thus providing strong constraints on the ratio of the single spin-flip to the non-flip amplitudes. Since the hadronic amplitude is dominated by the Pomeron amplitude at this √s, we conclude that this measurement addresses the question about the presence of a hadronic spin flip due to the Pomeron exchange in polarized proton–proton elastic scattering.
Ichneumonidae are incredibly diverse, yet there have been few Guatemalan ichneumonid studies. We studied the phenology of 215 specimens of Zagryphus zulaya Gauld (Hymenoptera: Ichneumonidae: Tryphoninae), most captured in a light trap and two Malaise traps in a montane (1850m) forest from 2002 to 2014. One of the Malaise traps caught over 95% of the specimens. The results suggest that Z. zulaya is most abundant in May, June, July, and August, the rainy season. Zagryphus vegai Gauld is newly recorded from Guatemala; it was previously known only from Costa Rica. It was found at an altitude of 1850m, though its previous known range was 700m to 1500m.
Bicellonycha amoena (Gorham, 1880) (Coleoptera: Lampyridae) usually flies one meter above ground level over grass, water, or open areas, where males produce a simple single flash every 2–4 seconds, having their most active flashing period from mid to late dusk and early night. In addition, nothing else is known about the behavior of this species. We conducted field observations at the “Mayan Golf Club” in Guatemala Department, and Santiago Sacatepéquez, Sacatepéquez Department, Guatemala; and analyzed B. amoena flashes with a spectroscope. Fireflies displayed a lime-green bioluminescence color. The male flashing activity began ~30 minutes after sunset and lasted approximately 70 minutes. For B. amoena, the spectral composition of the flash is intermediate between those known from twilight-active fireflies and nocturnalactive fireflies.
ZooBank registration. urn:lsid:zoobank.org:pub:512FB867-8E8F-47E6-AD02-B3B13C97C25D