新丰中子核素￣（185）Hf的研究I．合成、分离和鉴别

用（ｎ，２ｐ）反应和快化分离法首次合成和鉴别了新丰中子同位素￣（１８５）Ｈｆ。其半衰期为３．５±０．６ｍｉｎ。另外，还观察到一条能量为１６４．５±０．５ｋｅＶ、半衰期为４．３±０．９ｍｉｎ的属于￣（１８５）Ｈｆ衰变的γ射线。An unreported Hafnium isotope￣185Hf has been identified for first time.Sources of￣185Hfprepared by 14 MeV neutron irradiation of tungsten followed by radiochemical separation have been studied. The new activity is identified by following the time variation of the γ-rays. The half-life of￣185Hf has been determined to be 3.5±0.6min. In addition,a new 164.5±0.5keV γ-ray is found and assigned to￣185Hf based on the rneasurements of transition enertgy and half-life.中国科学院八五重大项目资

Measurement of integrated luminosity of data collected at 3.773 GeV by BESIII from 2021 to 2024

We present a measurement of the integrated luminosity e+e- of collision data collected by the BESIII detector at the BEPCII collider at a center-of-mass energy of Ecm = 3.773 GeV. The integrated luminosities of the datasets taken from December 2021 to June 2022, from November 2022 to June 2023, and from October 2023 to February 2024 were determined to be 4.995±0.019 fb-1, 8.157±0.031 fb-1, and 4.191±0.016 fb-1, respectively, by analyzing large angle Bhabha scattering events. The uncertainties are dominated by systematic effects, and the statistical uncertainties are negligible. Our results provide essential input for future analyses and precision measurements

Determination of the number of ψ(3686) events taken at BESIII

The number of ψ(3686) events collected by the BESIII detector during the 2021 run period is determined to be (2259.3±11.1)×106 by counting inclusive ψ(3686) hadronic events. The uncertainty is systematic and the statistical uncertainty is negligible. Meanwhile, the numbers of ψ(3686) events collected during the 2009 and 2012 run periods are updated to be (107.7±0.6)×106 and (345.4±2.6)×106, respectively. Both numbers are consistent with the previous measurements within one standard deviation. The total number of ψ(3686) events in the three data samples is (2712.4±14.3)×10^