The four LEP collaborations, ALEPH, DELPHI, L3 and OPAL, have searched for the neutral Higgs bosons which are predicted by the Minimal Supersymmetric Standard Model (MSSM). The data of the four collaborations are statistically combined and examined for their consistency with the background hypothesis and with a possible Higgs boson signal. The combined LEP data show no significant excess of events which would indicate the production of Higgs bosons. The search results are used to set upper bounds on the cross-sections of various Higgs-like event topologies. The results are interpreted within the MSSM in a number of "benchmark" models, including CP-conserving and CP-violating scenarios. These interpretations lead in all cases to large exclusions in the MSSM parameter space. Absolute limits are set on the parameter tan β and, in some scenarios, on the masses of neutral Higgs bosons.

Development of efficient and durable oxygen evolution reaction (OER) catalysts has a direct impact on the water splitting efficiency and cost effectiveness.

The aim of this work is to investigate the microstructure development of cerium oxide nanocrystal, prepared by the microemulsion process, as a function of annealing temperature in air. Combined with the HRTEM and the thermogravimetric−differential thermal analysis (TG−DTA), the XRD patterns reveal that the sample annealed at 623 K is amorphous, and the formation of cerium oxide nanocrystal occurs above 773 K. The local structural and electronic properties in the nanocrystallization process are probed by X-ray absorption spectra (XAS) at the Ce L3 edge. It is found that the phase structure changes from triclinic to cubic (CeO2), and the electronic structure changes from Ce3+ to Ce4+ upon increasing the annealing temperature.

We study the evolution of the temporal properties of MAXIJ1820+070 during the 2018 outburst in its hard state from MJD58,190 to 58,289 with Insight-HXMT in a broad energy band 1-150 keV. We find different behaviors of the hardness ratio, the fractional rms and time lag before and after MJD58,257, suggesting a transition occurred around this point. The observed time lags between the soft photons in the 1-5 keV band and the hard photons in higher energy bands, up to 150 keV, are frequency-dependent: the time lags in the low-frequency range, 2-10mHz, are both soft and hard lags with a timescale of dozens of seconds but without a clear trend along the outburst; the time lags in the high-frequency range, 1-10Hz, are only hard lags with a timescale of tens of milliseconds; they first increase until around MJD58,257 and decrease after this date. The high-frequency time lags are significantly correlated to the photon index derived from the fit to the quasi-simultaneous NICER spectrum in the 1-10 keV band. This result is qualitatively consistent with a model in which the high-frequency time lags are produced by Comptonization in a jet.Unified Astronomy Thesaurus concepts: Black holes (162); Compact objects (288); Low-mass x-ray binary stars (939)

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We performed the broadband (1–100 keV) spectral analysis of the first Galactic Be ultraluminous X-ray pulsar (BeULX) Swift J0243.6+6124 observed by Insight-HXMT during the 2017−2018 outburst. The results show spectral transitions at two typical luminosities, roughly consistently with those reported previously via pure timing analysis. We find that the spectrum evolves and becomes softer and has higher cutoff energies until the luminosity reaches L 1 (∼1.5  ×  1038 erg s−1). Afterwards the spectrum becomes harder with lower cutoff energies until the luminosity increases to L 2 (∼4.4  × 1038 erg s−1), around which the second spectral transition occurs. Beyond L 2, the spectrum softens again and has larger cutoff energies. Similar behaviors were observed previously in other high-mass X-ray binary systems (HMXBs), especially for the second transition at higher luminosities, which is believed to have a correlation with the magnetic field of the harbored neutron star. Accordingly, we speculate that Swift J0243.6+6124 owns a neutron star with magnetic field strength >1013 G. The spectral transition at around L 1 of Swift J0243.6+6124 is first observed thoroughly for any HMXB outburst characterized by strong evolution of the thermal component: the temperature of the blackbody drops sharply accompanied by a sudden increase of the blackbody radius. These spectral transitions can in principle be understood in a general scenario of balancing the emission patterns between the pencil and the fan beams at the magnetic pole, for which the extreme brightness of Swift J0243.6+6124 may provide an almost unique lab to probe the details.

The mass of the W boson is determined from the direct reconstruction of W decays in WW → qqqq and WW → ℓνqq events in e + e − collisions at LEP. The data sample corresponds to an integrated luminosity of 683 pb −1 collected with the ALEPH detector at centre-of-mass energies up to 209 GeV. To minimise any effect from colour reconnection a new procedure is adopted in which low energy particles are not considered in the mass determination from the qqqq channel. The combined result from all channels is m W = 80.440 ± 0.043(stat.) ± 0.024(syst.) ± 0.009(FSI) ± 0.009(LEP) GeV/c 2 ,where FSI represents the possible effects of final state interactions in the qqqq channel and LEP indicates the uncertainty in the beam energy. From twoparameter fits to the W mass and width, the W width is found to be Γ W = 2.14 ± 0.09(stat.) ± 0.04(syst.) ± 0.05(FSI) ± 0.01(LEP) GeV.To be published in Eur. Phys. J. C---------------

A search for the production and non-standard decay of a Higgs boson, h, into four taus through intermediate pseudoscalars, a, is conducted on 683 pb −1 of data collected by the ALEPH experiment at centre-of-mass energies from 183 to 209 GeV. No excess of events above background is observed, and exclusion limits are placed on the combined production cross section times branching ratio, ξ 2 = σ(e + e − →Zh). For m h < 107 GeV/c 2 and 4 < m a < 10 GeV/c 2 , ξ 2 > 1 is excluded at the 95% confidence level.