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- Ablikim, M., et al.
(författare)
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Search for invisible decays of omega and phi with J/psi data at BESIII
- 2018
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Ingår i: Physical Review D. - : American Physical Society. - 2470-0010 .- 2470-0029. ; 98:3
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Tidskriftsartikel (refereegranskat)abstract
- Using a data sample of (1310.6 +/- 7.0) x 10(6) J/psi events collected with the BESIII detector operating at the BEPCII collider, we perform the first experimental search for invisible decays of a light vector meson (V = omega, phi) via J/psi -> V-eta decays. The decay of eta -> pi(+)pi(-)pi(0) is utilized to tag the V meson decaying into the invisible final state. No evidence for a significant invisible signal is observed, and the upper limits on the ratio of branching fractions at the 90% confidence level are determined to be B(omega -> invisible)/B(omega -> pi(+)pi(-)pi(0)) < 8.1 x 10(-5) and B(phi -> invisible)/B(phi -> K+K-) < 3.4 x 10(-4). By using the world average values of B(omega -> pi(+)pi(-)pi(0) and B(phi -> K+K-,) the upper limits on the decay branching fractions at the 90% confidence level are set as B(omega -> invisible) < 7.3 x 10(-5) and B(phi -> invisible) < 1.7 x 10(-4), respectively.
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- Ablikim, M., et al.
(författare)
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First measurement of e(+)e(-) -> pK(S)(0)(n)over-barK(-) + c.c. above open charm threshold
- 2018
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Ingår i: Physical Review D. - 2470-0010 .- 2470-0029. ; 98:3
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Tidskriftsartikel (refereegranskat)abstract
- The process e(+)e(-) -> pK(S)(0)(n) over barK(-) + c.c. and its intermediate processes are studied for the first time, using data samples collected with the BESIII detector at BEPCII at center-of-mass energies of 3.773, 4.008, 4.226, 4.258, 4.358, 4.416, and 4.600 GeV, with a total integrated luminosity of 7.4 fb(-1). The Born cross section of e(+)e(-) -> pK(S)(0)(n) over barK(-) + c.c. is measured at each center-of-mass energy, but no significant resonant structure in the measured cross-section line shape between 3.773 and 4.600 GeV is observed. No evident structure is detected in the pK(-), nK(S)(0), pK(S)(0), nK(+), p (n) over bar, or (KSK-)-K-0 invariant mass distributions except for Lambda(1520). The Born cross sections of e(+)e(-) -> Lambda(1520)(n) over barK(S)(0) + c.c. and e(+)e(-) -> Lambda(1520)(p) over barK(+) + c.c. are measured, and the 90% confidence level upper limits on the Born cross sections of e(+)e(-) -> Lambda(1520)(Lambda) over bar (1520) are determined at the seven center-of-mass energies. There is an evident difference in line shape and magnitude of the measured cross sections between e(+)e(-) -> Lambda(1520)(-> pK(-))(n) over barK(S)(0) and e(+)e(-) -> pK-(Lambda) over bar (1520)(-> (n) over barK(S)(0)).
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- Ablikim, M., et al.
(författare)
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Observation of the Semileptonic Decay D-0 -> a(0)(980)(-)e(+)nu(e) and Evidence for D+ -> a(0)(980)(0)e(+)nu(e)
- 2018
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Ingår i: Physical Review Letters. - : AMER PHYSICAL SOC. - 0031-9007 .- 1079-7114. ; 121:8
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Tidskriftsartikel (refereegranskat)abstract
- Using an e(+)e(-) collision data sample of 2.93 fb(-1) collected at a center-of-mass energy of 3.773 GeV by the BESIII detector at BEPCII, we report the observation of D-0 -> a(0)(980)(-)e(+)nu(e) and evidence for D+ -> a(0)(980)(0)e(+)nu(e) with significances of 6.4 sigma and 2.9 sigma, respectively. The absolute branching fractions are determined to be B(D-0 -> a(0)(980)(-)e(+)nu(e)) x B(a(0)(980)(-) -> eta pi(-)) = [1.33(-0.29)(+0.33)(stat) +/- 0.09(syst)] x 10(-4) and B(D+ -> a(0)(980)(0)e(+)nu(e)) x B(a(0)(980)(0) -> eta pi(0)) = [1.66(-0.66)(+0.81)(stat) +/- 0.11(syst) x 10(-4). This is the first time the a(0)(980) meson has been measured in a D-0 semileptonic decay, which would open one more interesting page in the investigation of the nature of the puzzling a(0)(980) states.
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- Ablikim, M., et al.
(författare)
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Search for the rare decays D -> h(h((')))e(+) e(-)
- 2018
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Ingår i: Physical Review D. - : AMER PHYSICAL SOC. - 2470-0010 .- 2470-0029. ; 97:7
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Tidskriftsartikel (refereegranskat)abstract
- We search for rare decays of D mesons to hadrons accompanied by an electron-positron pair (h(h((')))e(+)e(- )),using an e(+)e(-) collision sample corresponding to an integrated luminosity of 2.93 fb(-1) collected with the BESIII detector at root s = 3.773 GeV. No significant signals are observed, and the corresponding upper limits on the branching fractions at the 90% confidence level are determined. The sensitivities of the results are at the level of 10(-5)-10(-6), providing a large improvement over previous searches.
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- Liu, B. Y., et al.
(författare)
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Explosive radiation and spatial expansion across the cold environments of the Old World in an avian family
- 2017
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Ingår i: Ecology and Evolution. - : Wiley. - 2045-7758. ; 7:16, s. 6346-6357
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Tidskriftsartikel (refereegranskat)abstract
- Our objective was to elucidate the biogeography and speciation patterns in an entire avian family, which shows a complex pattern of overlapping and nonoverlapping geographical distributions, and much variation in plumage, but less in size and structure. We estimated the phylogeny and divergence times for all of the world's species of Prunella based on multiple genetic loci, and analyzed morphometric divergence and biogeographical history. The common ancestor of Prunella was present in the Sino-Himalayan Mountains or these mountains and Central Asia-Mongolia more than 9 million years ago (mya), but a burst of speciations took place during the mid-Pliocene to early Pleistocene. The relationships among the six primary lineages resulting from that differentiation are unresolved, probably because of the rapid radiation. A general increase in sympatry with increasing time since divergence is evident. With one exception, species in clades younger than c. 3.7 my are allopatric. Species that are widely sympatric, including the most recently diverged (2.4 mya) sympatric sisters, are generally more divergent in size/structure than allo-/parapatric close relatives. The distributional pattern and inferred ages suggest divergence in allopatry and substantial waiting time until secondary contact, likely due to competitive exclusion. All sympatrically breeding species are ecologically segregated, as suggested by differences in size/structure and habitat. Colonizations of new areas were facilitated during glacialperiods, followed by fragmentation during interglacials-contrary to the usual view that glacial periods resulted mainly in fragmentations.
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- Liu, G.Q., et al.
(författare)
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Naphthenic acid corrosion characteristic and corrosion product film resistance of carbon steel and Cr5Mo low alloy steel in secondary vacuum gas oil
- 2016
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Ingår i: Corrosion Engineering, Science and Technology. - 1478-422X .- 1743-2782. ; 51:6, s. 445-454
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Tidskriftsartikel (refereegranskat)abstract
- Although naphthenic acid corrosion (NAC) has been studied for many years, the mechanism of NAC is not fully understood. The objective of this paper is to study high-temperature NAC in secondary vacuum gas oil of an industrial crude oil vacuum distillation tower. A high-temperature autoclave was applied to conduct high-temperature corrosion test to investigate NAC behaviour of carbon steel and Cr5Mo low alloy steel at different sulphur contents and total acid numbers (TAN). The result shows that the corrosion rate of carbon steel and low alloy steel is high at low TAN and high TAN while it keeps at a low value at medium TAN. Corrosion product film on Cr5Mo low alloy steel surface is denser and more compact than that of carbon steel at high TAN. The chromium present in Cr5Mo low alloy steel plays an important role in NAC resistance by the formation of Cr7S8 film in the inner layer of the scale. Corrosion rates of the two steels in secondary vacuum gas oil are high at low TAN and high TAN, but low at medium TAN which are strange and different from previous experimental results conducted in non-industrial oil solution. A tentative explanation for this new phenomenon is also put forward.
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| 13. |
- Qu, C. L., et al.
(författare)
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Activation of mu-opioid receptors in the ventrolateral orbital cortex inhibits the GABAergic miniature inhibitory postsynaptic currents in rats
- 2015
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Ingår i: Neuroscience Letters. - : Elsevier BV. - 0304-3940. ; 592, s. 64-69
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Tidskriftsartikel (refereegranskat)abstract
- Previous studies have indicated that mu-opioid receptors in the ventrolateral orbital cortex (VLO) are involved in antinociception in tail flick tests and GABAergic neurons or terminals express mu-opioid receptors in the VLO. The current study examined the effect of selective mu-opioid receptor agonist DAMGO on the GABAergic miniature inhibitory postsynaptic currents (mIPSCs) in the VLO in rats using the whole-cell patch clamp. The results demonstrated that 5 mu M DAMGO application into the rat VLO slices significantly reduced the GABAergic mIPSCs frequency, without any effect on its amplitude, and this effect of DAMGO was reversed by pretreatment with selective mu-opioid receptor antagonist I i.M CTOP. Importantly, application of CTOP alone into the VLO slices did not produce any effect on the frequency and amplitude of GABAergic mIPSCs. These results indicate a presynaptic effect of mu-opioid receptor activation on the GABAergic neurons in the VLO. The current data suggests that a presynaptic inhibition of the GABA release may contribute to the mu-opioid receptor mediated effects in the VLO and provides novel electrophysiological evidence for the underlying mechanisms of mu-opioid receptors in the VLO. (C) 2015 Elsevier Ireland Ltd. All rights reserved.
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