Magnesium alloys,a novel functional material for the fabrication of fracturing tools,are being paid more and more attentions recently due to their relatively high mechanical properties and fast dissolubility ability a...Magnesium alloys,a novel functional material for the fabrication of fracturing tools,are being paid more and more attentions recently due to their relatively high mechanical properties and fast dissolubility ability after fracturing.In this study,the novel extruded Mg-10Gd-3Y-0.3Zr-xNi alloys will be reported and their microstructure,mechanical and corrosion behaviors will be also studied.The results show that Ni contents influence phase precipitation behaviors.With adding 0.2 wt%Ni,a large amount of Zr_(7)Ni_(10)phases will be precipitated insidesα-Mg matrix,directly leading to degradation of strength and large corrosion rate.With further increasing Ni contents,the precipitation phases can be changed from Mg_(5)RE to 18R-LPSO structure,resulting in higher mechanical properties and faster corrosion rate.Moreover,adding Ni element also change the texture orientation by influencing the precipitation behavior of the alloys.The alloys invented in this paper have attained the highest compressive and tensile properties among all the reported dissoluble magnesium alloys.This work is beneficial in understanding the role of Ni in the magnesium alloys and provides more materials alternatives for the fabrication of dissoluble fracturing tools.展开更多
In this paper,a method for analyzing the high-frequency attenuation property of polyurea-matrix composites is developed by combining experimental,computational and theoretical approaches.First,the ultrasonic experimen...In this paper,a method for analyzing the high-frequency attenuation property of polyurea-matrix composites is developed by combining experimental,computational and theoretical approaches.First,the ultrasonic experimental platform is established by solving the difficulties of high-frequency ultrasonic testing as high-frequency signal distortion,insufficient driving voltage and sampling rate failure,to study the dynamic mechanical properties(1-5 MHz)of pure polyurea and polyurea-matrix composites.Then,the influences of composite parameters including the size and volume fraction of inclusions on wave attenuation performance under different frequencies are obtained and further verified by numerical simulations.Next,the contribution of inclusions to the wave attenuation performance is also theoretically analyzed.It is found that the increase of inclusion volume fraction and inclusion diameter will increase the attenuation coefficient of the composites.And the attenuation of composites with the inclusions of a 150-μm diameter and 30%as volume fraction can be 82%higher than pure matrix.This amplifying attenuation effect of inclusions is mainly attributed to the scattering effect,which is verified by comparing numerical and theoretical results.展开更多
The formation of shear bands in metallic glasses(MGs)was examined by tailoring localized complex stress fields(LCSFs).The findings have shown that the LCSFs in MGs can increase the localization of strained atoms and a...The formation of shear bands in metallic glasses(MGs)was examined by tailoring localized complex stress fields(LCSFs).The findings have shown that the LCSFs in MGs can increase the localization of strained atoms and accelerate the release of accumulated deformation energy for initiating a shear band in confined and thin-layered regions.The findings not only add more knowledge to the formation mechanisms of shear bands in MGs,but also provide possible rationale for the discrepancies in the mechanical properties of different-sized MGs.As compared with the bulk samples,the higher strength and larger elastic limits in nanoscaled MGs could be attributed to the elimination of stress-concentrators,which can serve as LCSFs.展开更多
In order to investigate the response of cellular spacing to the variation of growth velocity under near-rapid directional solidification condition, Al-0.53wt%Zn alloy is directionally solidified with Bridgman apparatu...In order to investigate the response of cellular spacing to the variation of growth velocity under near-rapid directional solidification condition, Al-0.53wt%Zn alloy is directionally solidified with Bridgman apparatus. The results show that at the given temperature gradient the obtained microstrvctures are all cells and there exists a wide distribution range of cellular spacing. The maximum, λmax, minimum, λmin, and average cellular spacing, λ, as functions of growth rate, V, can be given by λmax=948.51V-0.4961, λmin= 661.16V-0.5015 and λ=412.41V-0.5049, respectively. The experimental results are compared with that predicted by KGT model, and a good agreement is found. Moreover,it is found that the average cellular spacing is also remarkably history-dependent.展开更多
The influence of the bilayer number on the microstructure,mechanical properties,adhesion strength and tribological behaviors of the WB_(2)/Cr multilayer films was systematically investigated in the present study.Five ...The influence of the bilayer number on the microstructure,mechanical properties,adhesion strength and tribological behaviors of the WB_(2)/Cr multilayer films was systematically investigated in the present study.Five groups of WB_(2)/Cr films with the same modulation ratio were synthesized by magnetron sputtering technique.The crystalline structure of the films was determined by X-ray diffraction.The morphologies and the microstructure of the films were observed by scanning electron microscopy,atomic force microscopy and transmission electron microscopy.Furthermore,Nano indenter,scratch tester and ball-on-disc tribometer were used to evaluate the mechanical and tribological properties.As bilayer numbers varied from 5 to 40,the hardness increased first and then decreased with the maximum hardness of 33.9 GPa when the bilayer number is 30.The H/E^(*)and H^(3)/E^(*2)values calculated to evaluate the fracture toughness showed the similar changing trend with hardness.The adhesion strength reached the maximum of 67 N when the bilayer number is 30.The surface roughness and friction coefficient decreased with increasing bilayer number.The wear mechanism was also investigated,and the results suggested that the multilayer film with bilayer number of 30 exhibited the best wear resistance(1.78×10^(–7)mm^(3)/Nm),benefiting from the contribution of high hardness,fracture toughness and adhesion strength.展开更多
By analyzing ψ(3686) data sample containing (107.7±0.6)×10^(6) events taken with the BESIII detector at the BEPCII storage ring in 2009,the χ_(c 0) resonance parameters are precisely measured using χ_(c 0...By analyzing ψ(3686) data sample containing (107.7±0.6)×10^(6) events taken with the BESIII detector at the BEPCII storage ring in 2009,the χ_(c 0) resonance parameters are precisely measured using χ_(c 0,c 2)→π^(+)π^(−)/K^(+)K^(−) events.The mass of χ_(c 0) is determined to be M (χ_(c 0))=(3415.63±0.07±0.07±0.07)MeV/c^(2),and its full width is F (χ_(c 0))=(12.52±0.12±0.13)MeV,where the first uncertainty is statistical,the second systematic,and the third for mass comes from χ_(c 2) mass uncertainty.These measurements improve the precision of χ_(c 0) mass by a factor of four and width by one order of magnitude over the previous individual measurements,and significantly boost our knowledge about the charmonium spectrum.Together with additional (345.4±2.6)×10^(6)(3686) data events taken in 2012,the decay branching fractions of χ_(c 0,c 2)→π^(+)π^(−)/K^(+)K^(−) are measured as well,with precision improved by a factor of three compared to previous measurements.These χ_(c 0) decay branching fractions provide important inputs for the study of glueballs.展开更多
Using 20.3 fb^(-1)of e^(+)e^(-)annihilation data collected at a center-of-mass energy of 3.773 GeV with the BESⅢdetector,we report on an improved search for the radiative leptonic decay D^(+)→γe^(+)ve.An upper limi...Using 20.3 fb^(-1)of e^(+)e^(-)annihilation data collected at a center-of-mass energy of 3.773 GeV with the BESⅢdetector,we report on an improved search for the radiative leptonic decay D^(+)→γe^(+)ve.An upper limit on its partial branching fraction for photon energies E_(γ)>10 MeV was determined to be 1.2×10^(-5)at a 90%confidence level;this excludes most current theoretical predictions.A sophisticated deep learning approach,which includes thorough validation and is based on the Transformer architecture,was implemented to efficiently distinguish the signal from massive backgrounds.展开更多
Using an electron-positron collision data sample corresponding to(1.0087±0.0044)×10^(10)events collected using the BESIII detector at the BEPCII collider,we firstly search for the lepton number violation de...Using an electron-positron collision data sample corresponding to(1.0087±0.0044)×10^(10)events collected using the BESIII detector at the BEPCII collider,we firstly search for the lepton number violation decayφ→π^(+)π^(+)e^(-)e^(-)via J/ψ→φη.No obviously signals are found.The upper limit on the branching fraction ofφ→π^(+)π^(+)e^(-)e^(-)is set to be 1.3×10^(-5)at the 90%confidence level.展开更多
Lepton number violation decayω→π^(+)π^(+)e^(-)e^(-)+c.c.is searched for via J/ψ→ωηusing a data sample of(1.0087±0.0044)×10^(10)J/ψevents collected via the BESIII detector at the BEPCII collider.No s...Lepton number violation decayω→π^(+)π^(+)e^(-)e^(-)+c.c.is searched for via J/ψ→ωηusing a data sample of(1.0087±0.0044)×10^(10)J/ψevents collected via the BESIII detector at the BEPCII collider.No significant signal is observed,and the upper limit on the branching fraction ofω→π^(+)π^(+)e^(-)e^(-)+c.c.at the 90%confidence level is determined for the first time to be 2.8×10^(-6).展开更多
We search for the leptonic decay D^(+)→e^(+)ν_(e)using an e+e-collision data sample with an integrated luminosity of 20.3 fb-1collected with the BESIII detector at a center-of-mass energy of 3.773 GeV.Significant si...We search for the leptonic decay D^(+)→e^(+)ν_(e)using an e+e-collision data sample with an integrated luminosity of 20.3 fb-1collected with the BESIII detector at a center-of-mass energy of 3.773 GeV.Significant signal is not observed,and an upper limit on the branching fraction of D^(+)→e^(+)ν_(e)is set as 9.7×10^(-7),at a confidence level of 90%.Our upper limit is an order of magnitude smaller than the previous limit for this decay mode.展开更多
Utilizing 4.5 fb^(-1)ofe^(+)e^(-)annihilation data collected at center-of-mass energies ranging from 4599.53 MeV to 4698.82 MeV by the BESIII detector at the BEPCII collider,we searched for singly Cabibbo-suppressed h...Utilizing 4.5 fb^(-1)ofe^(+)e^(-)annihilation data collected at center-of-mass energies ranging from 4599.53 MeV to 4698.82 MeV by the BESIII detector at the BEPCII collider,we searched for singly Cabibbo-suppressed hadronic decaysΛ_(c)^(+)→Σ^(0)K^(+)π^(0)andΛ_(c)^(+)→Σ^(0)K^(+)π^(+)π^(−)and with a single-tag method.No significant signals were observed for both decays.The upper limits on the branching fractions at the 90%confidence level were determined to be 5.0×10^(-4)for and forΛ_(c)^(+)→Σ^(0)K^(+)π^(0)and 6.5×10^(-4)forΛ_(c)^(+)→Σ^(0)K^(+)π^(+)π^(−).展开更多
The superτ-charm facility(STCF)is an electron–positron collider proposed by the Chinese particle physics community.It is designed to operate in a center-of-mass energy range from 2 to 7 GeV with a peak luminosity of...The superτ-charm facility(STCF)is an electron–positron collider proposed by the Chinese particle physics community.It is designed to operate in a center-of-mass energy range from 2 to 7 GeV with a peak luminosity of 0.5×10^(35) cm^(–2)·s^(–1) or higher.The STCF will produce a data sample about a factor of 100 larger than that of the presentτ-charm factory—the BEPCII,providing a unique platform for exploring the asymmetry of matter-antimatter(charge-parity violation),in-depth studies of the internal structure of hadrons and the nature of non-perturbative strong interactions,as well as searching for exotic hadrons and physics beyond the Standard Model.The STCF project in China is under development with an extensive R&D program.This document presents the physics opportunities at the STCF,describes conceptual designs of the STCF detector system,and discusses future plans for detector R&D and physics case studies.展开更多
Using e^(+)e^(−)annihilation data corresponding to an integrated luminosity of 2.93 fb^(−1)taken at the center-of-mass energy√s=3.773 GeV with the BESIII detector,a joint amplitude analysis is performed on the decays...Using e^(+)e^(−)annihilation data corresponding to an integrated luminosity of 2.93 fb^(−1)taken at the center-of-mass energy√s=3.773 GeV with the BESIII detector,a joint amplitude analysis is performed on the decays D^(0)→π^(+)π^(−)π^(+)π^(−)and D^(0)→π^(+)π^(−)π^(0)π^(0)(non-η).The fit fractions of individual components are obtained,and large interferences among the dominant components of the decays D^(0)→a_(1)(1260)π,D^(0)→π(1300)π,D^(0)→ρ(770)ρ(770),and D^(0)→2(ππ)_(S)are observed in both channels.With the obtained amplitude model,the CP-even fractions of D^(0)→π^(+)π^(−)π^(+)π^(−)and D^(0)→π^(+)π^(−)π^(0)π^(0)(non-η)are determined to be(75.2±1.1_(stat).±1.5_(syst.))%and(68.9±1.5_(stat).±2.4_(syst.))%,respectively.The branching fractions of D^(0)→π^(+)π^(−)π^(+)π^(−)and D^(0)→π^(+)π^(−)π^(0)π^(0)(non-η)are measured to be(0.688±0.010_(stat.)±0.010_(syst.))%and(0.951±0.025_(stat.)±0.021_(syst.))%,respectively.The amplitude analysis provides an important model for the binning strategy in measuring the strong phase parameters of D^(0)→4πwhen used to determine the CKM angleγ(ϕ_(3))via the B^(−)→DK^(−)decay.展开更多
The number ofψ(3686)events collected by the BESⅢdetector during the 2021 run period is determined to be(2259.3±11.1)×10~6 by counting inclusiveψ(3686)hadronic events.The uncertainty is systematic and the ...The number ofψ(3686)events collected by the BESⅢdetector during the 2021 run period is determined to be(2259.3±11.1)×10~6 by counting inclusiveψ(3686)hadronic events.The uncertainty is systematic and the statistical uncertainty is negligible.Meanwhile,the numbers ofψ(3686)events collected during the 2009 and 2012run periods are updated to be(107.7±0.6)×10~6 and(345.4±2.6)×10~6,respectively.Both numbers are consistent with the previous measurements within one standard deviation.The total number ofψ(3686)events in the three data samples is(2712.4±14.3)×10~6.展开更多
We present a measurement of the integrated luminosity of e^(+)e^(-)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 ...We present a measurement of the integrated luminosity of e^(+)e^(-)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.展开更多
By using the ultrasound-assisted liquid phase exfoliation method, Bi_2Te_3 nanosheets are synthesized and deposited onto a quartz plate to form a kind of saturable absorber(SA), in which nonlinear absorption propertie...By using the ultrasound-assisted liquid phase exfoliation method, Bi_2Te_3 nanosheets are synthesized and deposited onto a quartz plate to form a kind of saturable absorber(SA), in which nonlinear absorption properties around 2 μm are analyzed with a home-made mode-locked laser. With the as-prepared Bi_2Te_3 SA employed,a stable passively Q-switched all-solid-state 2 μm laser is successfully realized. Q-switched pulses with a maximum average output power of 2.03 W are generated under an output coupling of 5%, corresponding to the maximum single-pulse energy of 18.4 μJ and peak power of 23 W. The delivered shortest pulse duration and maximum repetition rate are 620 ns and 118 k Hz under an output coupling of 2%, respectively. It is the first presentation of such Bi_2Te_3 SA employed in a solid-state Q-switched crystalline laser at 2 μm, to the best of our knowledge. In comparison with other 2 D materials suitable for pulsed 2 μm lasers, the saturable absorption performance of Bi_2Te_3 SA is proved to be promising in generating high power and high-repetition-rate 2 μm laser pulses.展开更多
A search for the rare decays W^(+)→D_(s)^(+)γ and Z→D0γis performed using proton-proton collision data collected by the LHCb experiment at a centre-of-mass energy of 13TeV,corresponding to an integrated luminosity...A search for the rare decays W^(+)→D_(s)^(+)γ and Z→D0γis performed using proton-proton collision data collected by the LHCb experiment at a centre-of-mass energy of 13TeV,corresponding to an integrated luminosity of 2.0fb−1.No significant signal is observed for either decay mode and upper limits on their branching fractions are set using W^(+)→D_(s)^(+)γ and Z→μ+μ−decays as normalization channels.The upper limits are 6.5×10^(−4) and 2.1×10^(−3) at 95% confidence level for the W^(+)→D_(s)^(+)γ and Z→D^(0)γ decay modes,respectively.This is the first reported search for the Z→D^(0)γ decay,while the upper limit on the W+→D+sγbranching fraction improves upon the previous best limit.展开更多
Using data taken at 29 center-of-mass energies between 4.16 and 4.70 GeV with the BESⅢdetector at the Beijing Electron Positron Collider corresponding to a total integrated luminosity of approximately 18.8 fb^(-1),th...Using data taken at 29 center-of-mass energies between 4.16 and 4.70 GeV with the BESⅢdetector at the Beijing Electron Positron Collider corresponding to a total integrated luminosity of approximately 18.8 fb^(-1),the process e^(+)e^(-)→pppñπ+c.c.is observed for the first time with a statistical significance of 11.5σ.The average Born cross sections in the energy ranges of(4.160,4.380)GeV,(4.400,4.600)GeV and(4.610,4.700)GeV are measured to be(21.5±5.7±1.2)fb,(46.3±10.6±2.5)fb and(59.0±9.4±3.2)fb,respectively,where the first uncertainties are statistical and the second are systematic.The line shapes of the pñ and ppπ^(-)invariant mass spectra are consistent with phase space distributions,indicating that no hexaquark or di-baryon state is observed.展开更多
We report a search for a heavier partner of the recently observed Z_(cs)(3985)^(-) state,denoted as Z_(cs)^('-),in the process e^(+)e^(−)→K^(+)D_(s)^(∗−) D^(∗0 )+ c.c.,based on e^(*)e^(-)collision data collected ...We report a search for a heavier partner of the recently observed Z_(cs)(3985)^(-) state,denoted as Z_(cs)^('-),in the process e^(+)e^(−)→K^(+)D_(s)^(∗−) D^(∗0 )+ c.c.,based on e^(*)e^(-)collision data collected at the center-of-mass energies of √s=4.661,4.682 and 4.699 GeV with the BESIII detector.The Z_(cs)^('-) is of interest as it is expected to be a candidate for a hidden-charm and open-strange tetraquark.A partial-reconstruction technique is used to isolate K^(+)recoil-mass spectra,which are probed for a potential contribution from Z_(cs)^('-)→D_(s)^(∗−) D^(∗0 )+ c.c.We find an excess of Z_(cs)^('-)→D_(s)^(*-)-D^(*0)(c.c.)candidates with a significance of 2.1o,after considering systematic uncertainties,at a mass of(4123.5±0.7_(sat)±4.7_(syst.))MeV/c^(2).As the data set is limited in size,the upper limits are evaluated at the 90%confidence level on the product of the Born cross sections(σ^(Borm))and the branching fraction(B)of Z_(cs)^('-)→D_(s)^(*-)-D^(*0),under different assumptions of the Z_(cs)^('-) mass from 4.120 to 4.140 MeV and of the width from 10 to 50 MeV at the three center-of-mass energies.The upper limits of σ^(Born).B are found to be at the level of O(1)pb at each energy.Larger data samples are needed to confirm the Z_(cs)^('-) state and clarify its nature in the coming years.展开更多
Purpose A structure,used as a complex source of X-rays and neutron source,is designed with the assistance of CST module tool.Methods Particles of H-and electron,attracted from a plasma source,are designed to be separa...Purpose A structure,used as a complex source of X-rays and neutron source,is designed with the assistance of CST module tool.Methods Particles of H-and electron,attracted from a plasma source,are designed to be separated by an energy selector.Soon after the separation,the trajectory and beam quality of H-are controlled by a special designation of potential barrier and potential well.And both particles are then accelerated by three pairs of pierce similar pole to an energy of 150 keV to produce X-rays/neutron.Results With proper optimization of structure and potential combination,a binocular structure with beam center distance of 15 mm,beam diameter smaller than 3.5 mm has been devised,which gives a feasible suggestion to produce two rays with one structure in the same time.展开更多
基金The National Natural Science Foundation of China(Nos.51671017,51971020)the Major State Research and Development Program of China(No.2016YFB0300801)+4 种基金Beijing Municipal Natural Science Foundation(No.2202033)Beijing Laboratory of Metallic Materials and Processing for Modern Transportationthe fund of the State Key Laboratory of Solidification Processing in NWPU(No.SKLSP201835)the Fundamental Research Funds for the Central Universities(No.FRF-IC-19–010,FRF-IC-19–015)the Opening Research Fund of State Key Laboratory for Advanced Metals and Materials(2018-Z04)。
文摘Magnesium alloys,a novel functional material for the fabrication of fracturing tools,are being paid more and more attentions recently due to their relatively high mechanical properties and fast dissolubility ability after fracturing.In this study,the novel extruded Mg-10Gd-3Y-0.3Zr-xNi alloys will be reported and their microstructure,mechanical and corrosion behaviors will be also studied.The results show that Ni contents influence phase precipitation behaviors.With adding 0.2 wt%Ni,a large amount of Zr_(7)Ni_(10)phases will be precipitated insidesα-Mg matrix,directly leading to degradation of strength and large corrosion rate.With further increasing Ni contents,the precipitation phases can be changed from Mg_(5)RE to 18R-LPSO structure,resulting in higher mechanical properties and faster corrosion rate.Moreover,adding Ni element also change the texture orientation by influencing the precipitation behavior of the alloys.The alloys invented in this paper have attained the highest compressive and tensile properties among all the reported dissoluble magnesium alloys.This work is beneficial in understanding the role of Ni in the magnesium alloys and provides more materials alternatives for the fabrication of dissoluble fracturing tools.
文摘In this paper,a method for analyzing the high-frequency attenuation property of polyurea-matrix composites is developed by combining experimental,computational and theoretical approaches.First,the ultrasonic experimental platform is established by solving the difficulties of high-frequency ultrasonic testing as high-frequency signal distortion,insufficient driving voltage and sampling rate failure,to study the dynamic mechanical properties(1-5 MHz)of pure polyurea and polyurea-matrix composites.Then,the influences of composite parameters including the size and volume fraction of inclusions on wave attenuation performance under different frequencies are obtained and further verified by numerical simulations.Next,the contribution of inclusions to the wave attenuation performance is also theoretically analyzed.It is found that the increase of inclusion volume fraction and inclusion diameter will increase the attenuation coefficient of the composites.And the attenuation of composites with the inclusions of a 150-μm diameter and 30%as volume fraction can be 82%higher than pure matrix.This amplifying attenuation effect of inclusions is mainly attributed to the scattering effect,which is verified by comparing numerical and theoretical results.
基金financially supported by the National Natural Science Foundation of China(Nos.51801049 and 51801174)the State Key Laboratory of Metastable Materials Science and Technology,Yanshan University(No.201809)the Fundamental Research Funds for the Central Universities of China(Nos.PA2019GDZC0096 and JD2019JGPY0015)。
文摘The formation of shear bands in metallic glasses(MGs)was examined by tailoring localized complex stress fields(LCSFs).The findings have shown that the LCSFs in MGs can increase the localization of strained atoms and accelerate the release of accumulated deformation energy for initiating a shear band in confined and thin-layered regions.The findings not only add more knowledge to the formation mechanisms of shear bands in MGs,but also provide possible rationale for the discrepancies in the mechanical properties of different-sized MGs.As compared with the bulk samples,the higher strength and larger elastic limits in nanoscaled MGs could be attributed to the elimination of stress-concentrators,which can serve as LCSFs.
文摘In order to investigate the response of cellular spacing to the variation of growth velocity under near-rapid directional solidification condition, Al-0.53wt%Zn alloy is directionally solidified with Bridgman apparatus. The results show that at the given temperature gradient the obtained microstrvctures are all cells and there exists a wide distribution range of cellular spacing. The maximum, λmax, minimum, λmin, and average cellular spacing, λ, as functions of growth rate, V, can be given by λmax=948.51V-0.4961, λmin= 661.16V-0.5015 and λ=412.41V-0.5049, respectively. The experimental results are compared with that predicted by KGT model, and a good agreement is found. Moreover,it is found that the average cellular spacing is also remarkably history-dependent.
基金supported by the National Natural Science Foundation of China(No.51701157)。
文摘The influence of the bilayer number on the microstructure,mechanical properties,adhesion strength and tribological behaviors of the WB_(2)/Cr multilayer films was systematically investigated in the present study.Five groups of WB_(2)/Cr films with the same modulation ratio were synthesized by magnetron sputtering technique.The crystalline structure of the films was determined by X-ray diffraction.The morphologies and the microstructure of the films were observed by scanning electron microscopy,atomic force microscopy and transmission electron microscopy.Furthermore,Nano indenter,scratch tester and ball-on-disc tribometer were used to evaluate the mechanical and tribological properties.As bilayer numbers varied from 5 to 40,the hardness increased first and then decreased with the maximum hardness of 33.9 GPa when the bilayer number is 30.The H/E^(*)and H^(3)/E^(*2)values calculated to evaluate the fracture toughness showed the similar changing trend with hardness.The adhesion strength reached the maximum of 67 N when the bilayer number is 30.The surface roughness and friction coefficient decreased with increasing bilayer number.The wear mechanism was also investigated,and the results suggested that the multilayer film with bilayer number of 30 exhibited the best wear resistance(1.78×10^(–7)mm^(3)/Nm),benefiting from the contribution of high hardness,fracture toughness and adhesion strength.
基金Supported in part by National Key R&D Program of China(2020YFA0406300,2020YFA0406400,2023YFA1606000)National Natural Science Foundation of China(NSFC)(11635010,11735014,11935015,11935016,11935018,12025502,12035009,12035013,12061131003,12192260,12192261,12192262,12192263,12192264,12192265,12221005,12225509,12235017,12361141819)+17 种基金the Chinese Academy of Sciences(CAS)Large-Scale Scientific Facility Programthe CAS Center for Excellence in Particle Physics(CCEPP)Joint Large-Scale Scientific Facility Funds of the NSFC and CAS(U1832207)100 Talents Program of CAS(ZR2022JQ02,ZR2024QA151)supported by Shandong Provincial Natural Science Foundationsupported by the China Postdoctoral Science Foundation(2023M742100)The Institute of Nuclear and Particle Physics(INPAC)and Shanghai Key Laboratory for Particle Physics and CosmologyGerman Research Foundation DFG(FOR5327,GRK 2149)Istituto Nazionale di Fisica Nucleare,ItalyKnut and Alice Wallenberg Foundation(2021.0174,2021.0299)Ministry of Development of Turkey(DPT2006K-120470)National Research Foundation of Korea(NRF-2022R1A2C1092335)National Science and Technology fund of MongoliaNational Science Research and Innovation Fund(NSRF)via the Program Management Unit for Human Resources&Institutional Development,Research and Innovation of Thailand(B16F640076,B50G670107)Polish National Science Centre(2019/35/O/ST2/02907)Swedish Research Council(2019.04595)The Swedish Foundation for International Cooperation in Research and Higher Education(CH2018-7756)U.S.Department of Energy(DE-FG02-05ER41374)。
文摘By analyzing ψ(3686) data sample containing (107.7±0.6)×10^(6) events taken with the BESIII detector at the BEPCII storage ring in 2009,the χ_(c 0) resonance parameters are precisely measured using χ_(c 0,c 2)→π^(+)π^(−)/K^(+)K^(−) events.The mass of χ_(c 0) is determined to be M (χ_(c 0))=(3415.63±0.07±0.07±0.07)MeV/c^(2),and its full width is F (χ_(c 0))=(12.52±0.12±0.13)MeV,where the first uncertainty is statistical,the second systematic,and the third for mass comes from χ_(c 2) mass uncertainty.These measurements improve the precision of χ_(c 0) mass by a factor of four and width by one order of magnitude over the previous individual measurements,and significantly boost our knowledge about the charmonium spectrum.Together with additional (345.4±2.6)×10^(6)(3686) data events taken in 2012,the decay branching fractions of χ_(c 0,c 2)→π^(+)π^(−)/K^(+)K^(−) are measured as well,with precision improved by a factor of three compared to previous measurements.These χ_(c 0) decay branching fractions provide important inputs for the study of glueballs.
基金supported in part by National Key R&D Program of China(2020YFA0406400,2023YFA1606000,2020YFA0406300)National Natural Science Foundation of China(NSFC)(11635010,11735014,11935015,11935016,11935018,12025502,12035009,12035013,12061131003,12192260,12192261,12192262,12192263,12192264,12192265,12221005,12225509,12235017,12361141819)+18 种基金the Chinese Academy of Sciences(CAS)Large-Scale Scientific Facility Programthe CAS Center for Excellence in Particle Physics(CCEPP)Joint Large-Scale Scientific Facility Funds of the NSFC and CAS(U1832207)CAS(YSBR-101)100 Talents Program of CASCAS Project for Young Scientists in Basic Research(YSBR-117)The Institute of Nuclear and Particle Physics(INPAC)and Shanghai Key Laboratory for Particle Physics and CosmologyAgencia Nacional de Investigación y Desarrollo de Chile(ANID),Chile(ANID PIA/APOYO AFB230003)German Research Foundation DFG(FOR5327)Istituto Nazionale di Fisica Nucleare,ItalyKnut and Alice Wallenberg Foundation(2021.0174,2021.0299)Ministry of Development of Turkey(DPT2006K-120470)National Research Foundation of Korea(NRF-2022R1A2C1092335)National Science and Technology fund of MongoliaNational Science Research and Innovation Fund(NSRF)via the Program Management Unit for Human Resources&Institutional Development,Research and Innovation of Thailand(B50G670107)Polish National Science Centre(2019/35/O/ST2/02907)Swedish Research Council(2019.04595)The Swedish Foundation for International Cooperation in Research and Higher Education(CH2018-7756)U.S.Department of Energy(DE-FG02-05ER41374)。
文摘Using 20.3 fb^(-1)of e^(+)e^(-)annihilation data collected at a center-of-mass energy of 3.773 GeV with the BESⅢdetector,we report on an improved search for the radiative leptonic decay D^(+)→γe^(+)ve.An upper limit on its partial branching fraction for photon energies E_(γ)>10 MeV was determined to be 1.2×10^(-5)at a 90%confidence level;this excludes most current theoretical predictions.A sophisticated deep learning approach,which includes thorough validation and is based on the Transformer architecture,was implemented to efficiently distinguish the signal from massive backgrounds.
基金supported in part by the National Key R&D Program of China(2020YFA0406300,2020YFA0406400)National Natural Science Foundation of China(NSFC)(12035009,11635010,11735014,11835012,11935015,11935016,11935018,11961141012,12025502,12035013,12061131003,12192260,12192261,12192262,12192263,12192264,12192265,12221005,12225509,12235017)+17 种基金the Chinese Academy of Sciences(CAS)Large-Scale Scientific Facility Programthe CAS Center for Excellence in Particle Physics(CCEPP)Joint Large-Scale Scientific Facility Funds of the NSFC and CAS(U1832207)CAS Key Research Program of Frontier Sciences(QYZDJ-SSW-SLH003,QYZDJ-SSW-SLH040)100 Talents Program of CASthe Institute of Nuclear and Particle Physics(INPAC)and Shanghai Key Laboratory for Particle Physics and Cosmologythe European Union's Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement(894790)the German Research Foundation DFG(455635585),the Collaborative Research Center CRC 1044,FOR5327,GRK 2149Istituto Nazionale di Fisica Nucleare,ItalyKnut and Alice Wallenberg Foundation(2021.0174,2021.0299)Ministry of Development of Turkey(DPT2006K-120470)National Research Foundation of Korea(NRF2022R1A2C1092335)National Science and Technology Fund of MongoliaNational Science Research and Innovation Fund(NSRF)via the Program Management Unit for Human Resources&Institutional Development,Research and Innovation of Thailand(B16F640076)Polish National Science Centre(2019/35/O/ST2/02907)Swedish Research Council(2019.04595)the Swedish Foundation for International Cooperation in Research and Higher Education(CH2018-7756)the U.S.Department of Energy(DE-FG02-05ER41374).
文摘Using an electron-positron collision data sample corresponding to(1.0087±0.0044)×10^(10)events collected using the BESIII detector at the BEPCII collider,we firstly search for the lepton number violation decayφ→π^(+)π^(+)e^(-)e^(-)via J/ψ→φη.No obviously signals are found.The upper limit on the branching fraction ofφ→π^(+)π^(+)e^(-)e^(-)is set to be 1.3×10^(-5)at the 90%confidence level.
基金Supported in part by National Key R&D Program of China(2023YFA1606000,2023YFA1606704)National Natural Science Foundation of China(NSFC)(12035009,11875170,11635010,11935015,11935016,11935018,12025502,12035013,12061131003,12192260,12192261,12192262,12192263,12192264,12192265,12221005,12225509,12235017,12361141819)+16 种基金the Chinese Academy of Sciences(CAS)Large-Scale Scientific Facility Program,CAS(YSBR-101)100 Talents Program of CASThe Institute of Nuclear and Particle Physics(INPAC)Shanghai Key Laboratory for Particle Physics and CosmologyAgencia Nacional de Investigación y Desarrollo de Chile(ANID)Chile(ANID PIA/APOYO AFB230003)ERC(758462)German Research Foundation DFG(FOR5327)Istituto Nazionale di Fisica Nucleare,ItalyKnut and Alice Wallenberg Foundation(2021.0174,2021.0299)Ministry of Development of Turkey(DPT2006K-120470)National Research Foundation of Korea(NRF-2022R1A2C1092335)National Science and Technology fund of MongoliaPolish National Science Centre(2024/53/B/ST2/00975)STFC(United Kingdom)Swedish Research Council(2019.04595)U.S.Department of Energy(DE-FG02-05ER41374)。
文摘Lepton number violation decayω→π^(+)π^(+)e^(-)e^(-)+c.c.is searched for via J/ψ→ωηusing a data sample of(1.0087±0.0044)×10^(10)J/ψevents collected via the BESIII detector at the BEPCII collider.No significant signal is observed,and the upper limit on the branching fraction ofω→π^(+)π^(+)e^(-)e^(-)+c.c.at the 90%confidence level is determined for the first time to be 2.8×10^(-6).
基金Supported in part by the National Key R&D Program of China(2023YFA1606000,2020YFA0406400,2020YFA0406300)the National Natural Science Foundation of China(NSFC)(11635010,11735014,11935015,11935016,11875054,11935018,12025502,12035009,12035013,12061131003,12192260,12192261,12192262,12192263,12192264,12192265,12221005,12225509,12235017,12361141819)+12 种基金the Chinese Academy of Sciences(CAS)Large-Scale Scientific Facility Programthe CAS Center for Excellence in Particle Physics(CCEPP)the Joint Large-Scale Scientific Facility Funds of the NSFC and CAS(U2032104,U1832207)the 100 Talents Program of CAS,the Excellent Youth Foundation of Henan Scientific Commitee(242300421044)the Institute of Nuclear and Particle Physics(INPAC)and Shanghai Key Laboratory for Particle Physics and Cosmology,the German Research Foundation DFG(FOR5327)the Istituto Nazionale di Fisica Nucleare,Italy,the Knut and Alice Wallenberg Foundation(2021.0174,2021.0299)the Ministry of Development of Turkey(DPT2006K-120470),the National Research Foundation of Korea(NRF-2022R1A2C1092335)the National Science and Technology Fund of Mongoliathe National Science Research and Innovation Fund(NSRF)via the Program Management Unit for Human Resources&Institutional Development,Research,and Innovation of Thailand(B16F640076,B50G670107)the Polish National Science Center(2019/35/O/ST2/02907)the Swedish Research Council(2019.04595)the Swedish Foundation for International Cooperation in Research and Higher Education(CH2018-7756)the US Department of Energy(DE-FG02-05ER41374)。
文摘We search for the leptonic decay D^(+)→e^(+)ν_(e)using an e+e-collision data sample with an integrated luminosity of 20.3 fb-1collected with the BESIII detector at a center-of-mass energy of 3.773 GeV.Significant signal is not observed,and an upper limit on the branching fraction of D^(+)→e^(+)ν_(e)is set as 9.7×10^(-7),at a confidence level of 90%.Our upper limit is an order of magnitude smaller than the previous limit for this decay mode.
基金supported in part by National Key R&D Program of China(2020YFA0406300,2020YFA0406400,2023YFA1606000)National Natural Science Foundation of China(NSFC)(12205141,11635010,11735014,11935015,11935016,11935018,12025502,12035009,12035013,12061131003,12192260,12192261,12192262,12192263,12192264,12192265,12221005,12225509,12235017,12361141819)+16 种基金Natural Science Foundation of Hunan Province(2024JJ2044)the Chinese Academy of Sciences(CAS)Large-Scale Scientific Facility Programthe CAS Center for Excellence in Particle Physics(CCEPP)Joint Large-Scale Scientific Facility Funds of the NSFC and CAS(U1832207)100 Talents Program of CASThe Institute of Nuclear and Particle Physics(INPAC)and Shanghai Key Laboratory for Particle Physics and CosmologyGerman Research Foundation DFG(FOR5327)Istituto Nazionale di Fisica Nucleare,ItalyKnut and Alice Wallenberg Foundation(2021.0174,2021.0299)Ministry of Development of Turkey(DPT2006K-120470)National Research Foundation of Korea(NRF2022R1A2C1092335)National Science and Technology fund of MongoliaNational Science Research and Innovation Fund(NSRF)via the Program Management Unit for Human Resources&Institutional Development,Research and Innovation of Thailand(B16F640076,B50G670107)Polish National Science Centre(2019/35/O/ST2/02907)Swedish Research Council(2019.04595)The Swedish Foundation for International Cooperation in Research and Higher Education(CH2018-7756)U.S.Department of Energy(DE-FG02-05ER41374)。
文摘Utilizing 4.5 fb^(-1)ofe^(+)e^(-)annihilation data collected at center-of-mass energies ranging from 4599.53 MeV to 4698.82 MeV by the BESIII detector at the BEPCII collider,we searched for singly Cabibbo-suppressed hadronic decaysΛ_(c)^(+)→Σ^(0)K^(+)π^(0)andΛ_(c)^(+)→Σ^(0)K^(+)π^(+)π^(−)and with a single-tag method.No significant signals were observed for both decays.The upper limits on the branching fractions at the 90%confidence level were determined to be 5.0×10^(-4)for and forΛ_(c)^(+)→Σ^(0)K^(+)π^(0)and 6.5×10^(-4)forΛ_(c)^(+)→Σ^(0)K^(+)π^(+)π^(−).
基金supported by the National Key R&D Program of China under Contract No.2022YFA1602200the International Partnership Program of the Chineses Academy of Sciences under Grant No.211134KYSB20200057the STCF Key Technology Research and Development Project.
文摘The superτ-charm facility(STCF)is an electron–positron collider proposed by the Chinese particle physics community.It is designed to operate in a center-of-mass energy range from 2 to 7 GeV with a peak luminosity of 0.5×10^(35) cm^(–2)·s^(–1) or higher.The STCF will produce a data sample about a factor of 100 larger than that of the presentτ-charm factory—the BEPCII,providing a unique platform for exploring the asymmetry of matter-antimatter(charge-parity violation),in-depth studies of the internal structure of hadrons and the nature of non-perturbative strong interactions,as well as searching for exotic hadrons and physics beyond the Standard Model.The STCF project in China is under development with an extensive R&D program.This document presents the physics opportunities at the STCF,describes conceptual designs of the STCF detector system,and discusses future plans for detector R&D and physics case studies.
基金Supported in part by the National Key R&D Program of China(2020YFA0406300,2020YFA0406400)the National Natural Science Foundation of China(NSFC)(11625523,11635010,11735014,11835012,11935015,11935016,11935018,11961141012,12025502,12035009,12035013,12061131003,12105276,12122509,12192260,12192261,12192262,12192263,12192264,12192265,12221005,12225509,12235017)+15 种基金the Chinese Academy of Sciences(CAS)Large-Scale Scientific Facility Programthe CAS Center for Excellence in Particle Physics(CCEPP)Joint Large-Scale Scientific Facility Funds of the NSFC and CAS(U1732263,U1832103,U1832207,U2032111)CAS Key Research Program of Frontier Sciences(QYZDJ-SSW-SLH003,QYZDJ-SSW-SLH040)100 Talents Program of CASThe Institute of Nuclear and Particle Physics(INPAC)and Shanghai Key Laboratory for Particle Physics and CosmologyEuropean Union's Horizon 2020 research and innovation programme under Marie Sklodowska-Curie grant agreement(894790)German Research Foundation DFG(455635585),Collaborative Research Center CRC 1044,FOR5327,GRK 2149Istituto Nazionale di Fisica Nucleare,ItalyMinistry of Development of Turkey(DPT2006K-120470)National Research Foundation of Korea(NRF-2022R1A2C1092335)National Science and Technology fund of MongoliaNational Science Research and Innovation Fund(NSRF)via the Program Management Unit for Human Resources&Institutional Development,Research and Innovation of Thailand(B16F640076)Polish National Science Centre(2019/35/O/ST2/02907)The Swedish Research CouncilU.S.Department of Energy(DE-FG02-05ER41374)。
文摘Using e^(+)e^(−)annihilation data corresponding to an integrated luminosity of 2.93 fb^(−1)taken at the center-of-mass energy√s=3.773 GeV with the BESIII detector,a joint amplitude analysis is performed on the decays D^(0)→π^(+)π^(−)π^(+)π^(−)and D^(0)→π^(+)π^(−)π^(0)π^(0)(non-η).The fit fractions of individual components are obtained,and large interferences among the dominant components of the decays D^(0)→a_(1)(1260)π,D^(0)→π(1300)π,D^(0)→ρ(770)ρ(770),and D^(0)→2(ππ)_(S)are observed in both channels.With the obtained amplitude model,the CP-even fractions of D^(0)→π^(+)π^(−)π^(+)π^(−)and D^(0)→π^(+)π^(−)π^(0)π^(0)(non-η)are determined to be(75.2±1.1_(stat).±1.5_(syst.))%and(68.9±1.5_(stat).±2.4_(syst.))%,respectively.The branching fractions of D^(0)→π^(+)π^(−)π^(+)π^(−)and D^(0)→π^(+)π^(−)π^(0)π^(0)(non-η)are measured to be(0.688±0.010_(stat.)±0.010_(syst.))%and(0.951±0.025_(stat.)±0.021_(syst.))%,respectively.The amplitude analysis provides an important model for the binning strategy in measuring the strong phase parameters of D^(0)→4πwhen used to determine the CKM angleγ(ϕ_(3))via the B^(−)→DK^(−)decay.
基金supported in part by National Key R&D Program of China under Contracts Nos.2020YFA0406300,2020YFA0406400National Natural Science Foundation of China(NSFC)under Contracts Nos.12150004,11635010,11735014,11835012,11935015,11935016,11935018,11961141012,12025502,12035009,12035013,12061131003,12192260,12192261,12192262,12192263,12192264,12192265,12221005,12225509,12235017+17 种基金the Program of Science and Technology Development Plan of Jilin Province of China under Contract Nos.20210508047RQ and 20230101021JCthe Chinese Academy of Sciences(CAS)Large-Scale Scientific Facility Programthe CAS Center for Excellence in Particle Physics(CCEPP)Joint Large-Scale Scientific Facility Funds of the NSFC and CAS under Contract No.U1832207CAS Key Research Program of Frontier Sciences under Contracts Nos.QYZDJ-SSW-SLH003,QYZDJ-SSW-SLH040100 Talents Program of CASThe Institute of Nuclear and Particle Physics(INPAC)Shanghai Key Laboratory for Particle Physics and CosmologyEuropean Union's Horizon 2020 research and innovation programme under Marie Sklodowska-Curie grant agreement under Contract No.894790German Research Foundation DFG under Contracts Nos.455635585,Collaborative Research Center CRC 1044,FOR5327,GRK 2149Istituto Nazionale di Fisica Nucleare,ItalyMinistry of Development of Turkey under Contract No.DPT2006K-120470National Research Foundation of Korea under Contract No.NRF-2022R1A2C1092335National Science and Technology fund of MongoliaNational Science Research and Innovation Fund(NSRF)via the Program Management Unit for Human Resources&Institutional Development,Research and Innovation of Thailand under Contract No.B16F640076Polish National Science Centre under Contract No.2019/35/O/ST2/02907The Swedish Research CouncilU.S.Department of Energy under Contract No.DE-FG02-05ER41374。
文摘The number ofψ(3686)events collected by the BESⅢdetector during the 2021 run period is determined to be(2259.3±11.1)×10~6 by counting inclusiveψ(3686)hadronic events.The uncertainty is systematic and the statistical uncertainty is negligible.Meanwhile,the numbers ofψ(3686)events collected during the 2009 and 2012run periods are updated to be(107.7±0.6)×10~6 and(345.4±2.6)×10~6,respectively.Both numbers are consistent with the previous measurements within one standard deviation.The total number ofψ(3686)events in the three data samples is(2712.4±14.3)×10~6.
基金Supported in part by the National Key R&D Program of China(2020YFA0406400,2020YFA0406300,2023YFA1606000)the National Natural Science Foundation of China(123B2077,12035009,11635010,11735014,11875054,11935015,11935016,11935018,11961141012,12025502,12035013,12061131003,12192260,12192261,12192262,12192263,12192264,12192265,12221005,12225509,12235017,12361141819)+8 种基金the Chinese Academy of Sciences(CAS)Large-Scale Scientific Facility Program,the CAS Center for Excellence in Particle Physics(CCEPP),the Joint Large-Scale Scientific Facility Funds of the NSFC and CAS(U2032104,U1832207)the Excellent Youth Foundation of Henan Scientific Commitee(242300421044)100 Talents Program of CASthe Institute of Nuclear and Particle Physics(INPAC)and Shanghai Key Laboratory for Particle Physics and Cosmology,German Research Foundation DFG(455635585,FOR5327,GRK 2149)Istituto Nazionale di Fisica Nucleare,Italy,Ministry of Development of Turkey(DPT2006K-120470)National Research Foundation of Korea(NRF-2022R1A2C1092335)National Science and Technology fund of Mongolia,National Science Research and Innovation Fund(NSRF)via the Program Management Unit for Human Resources&Institutional Development,Research and Innovation of Thailand(B16F640076)Polish National Science Centre(2019/35/O/ST2/02907),the Swedish Research CouncilU.S.Department of Energy(DE-FG02-05ER41374)。
文摘We present a measurement of the integrated luminosity of e^(+)e^(-)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.
基金National Natural Science Foundation of China(NSFC)(61475088,61775119,61378022,61422511)Young Scholars Program of Shandong University(2015WLJH38)Open Research Fund of the State Key Laboratory of Pulsed Power Laser Technology,Electronic Engineering Institute,Hefei,China(SLK2016KF01)
文摘By using the ultrasound-assisted liquid phase exfoliation method, Bi_2Te_3 nanosheets are synthesized and deposited onto a quartz plate to form a kind of saturable absorber(SA), in which nonlinear absorption properties around 2 μm are analyzed with a home-made mode-locked laser. With the as-prepared Bi_2Te_3 SA employed,a stable passively Q-switched all-solid-state 2 μm laser is successfully realized. Q-switched pulses with a maximum average output power of 2.03 W are generated under an output coupling of 5%, corresponding to the maximum single-pulse energy of 18.4 μJ and peak power of 23 W. The delivered shortest pulse duration and maximum repetition rate are 620 ns and 118 k Hz under an output coupling of 2%, respectively. It is the first presentation of such Bi_2Te_3 SA employed in a solid-state Q-switched crystalline laser at 2 μm, to the best of our knowledge. In comparison with other 2 D materials suitable for pulsed 2 μm lasers, the saturable absorption performance of Bi_2Te_3 SA is proved to be promising in generating high power and high-repetition-rate 2 μm laser pulses.
文摘A search for the rare decays W^(+)→D_(s)^(+)γ and Z→D0γis performed using proton-proton collision data collected by the LHCb experiment at a centre-of-mass energy of 13TeV,corresponding to an integrated luminosity of 2.0fb−1.No significant signal is observed for either decay mode and upper limits on their branching fractions are set using W^(+)→D_(s)^(+)γ and Z→μ+μ−decays as normalization channels.The upper limits are 6.5×10^(−4) and 2.1×10^(−3) at 95% confidence level for the W^(+)→D_(s)^(+)γ and Z→D^(0)γ decay modes,respectively.This is the first reported search for the Z→D^(0)γ decay,while the upper limit on the W+→D+sγbranching fraction improves upon the previous best limit.
基金Supported in part by National Key R&D Program of China under Contracts Nos.Supported in part by National Key R&D Program of China(2020YFA0406300,2020YFA0406400)National Natural Science Foundation of China(NSFC)(11975118,11625523,11635010,11735014,11822506,11835012,11935015,11935016,11935018,11961141012,12022510,12025502,12035009,12035013,12061131003,12075252,12192260,12192261,12192262,12192263,12192264,12192265)+19 种基金the Natural Science Foundation of Hunan Province of China(2019JJ30019)the Science and Technology Innovation Program of Hunan Province(2020RC3054)the Chinese Academy of Sciences(CAS)Large-Scale Scientific Facility ProgramJoint Large-Scale Scientific Facility Funds of the NSFC and CAS(U1732263,U1832207)CAS Key Research Program of Frontier Sciences(QYZDJ-SSW-SLH040)100 Talents Program of CASINPAC and Shanghai Key Laboratory for Particle Physics and CosmologyERC(758462)European Union Horizon 2020 research and innovation programme under Contract No.Marie Sklodowska-Curie grant agreement(894790)German Research Foundation DFG(43159800)Collaborative Research Center CRC 1044,FOR 2359,GRK 2149Istituto Nazionale di Fisica Nucleare,ItalyMinistry of Development of Turkey(DPT2006K-120470)National Science and Technology fundOlle Engkvist Foundation(200-0605)STFC(United Kingdom)The Knut and Alice Wallenberg Foundation(Sweden)(2016.0157)The Royal Society,UK(DH140054,DH160214)The Swedish Research CouncilU.S.Department of Energy(DE-FG02-05ER41374,DE-SC-0012069)。
文摘Using data taken at 29 center-of-mass energies between 4.16 and 4.70 GeV with the BESⅢdetector at the Beijing Electron Positron Collider corresponding to a total integrated luminosity of approximately 18.8 fb^(-1),the process e^(+)e^(-)→pppñπ+c.c.is observed for the first time with a statistical significance of 11.5σ.The average Born cross sections in the energy ranges of(4.160,4.380)GeV,(4.400,4.600)GeV and(4.610,4.700)GeV are measured to be(21.5±5.7±1.2)fb,(46.3±10.6±2.5)fb and(59.0±9.4±3.2)fb,respectively,where the first uncertainties are statistical and the second are systematic.The line shapes of the pñ and ppπ^(-)invariant mass spectra are consistent with phase space distributions,indicating that no hexaquark or di-baryon state is observed.
基金Supported in part by National Key R&D Program of China(Grant Nos.2020YFA0406400,2020YFA0406300)National Natural Science Foundation of China(NSFC)(Grant Nos.11635010,11735014,11805086,11835012,11935015,11935016,11935018,11961141012,12022510,12025502,12035009,12035013,12192260,12192261,12192262,12192263,12192264,12192265)+18 种基金the Chinese Academy of Sciences(CAS)Large-Scale Scientific Facility ProgramJoint Large-Scale Scientific Facility Funds of the NSFC and CAS(Grant No.U1832207)the CAS Center for Excellence in Particle Physics(CCEPP)100 Talents Program of CASFundamental Research Funds for the Central Universities,Lanzhou University,University of Chinese Academy of SciencesThe Institute of Nuclear and Particle Physics(INPAC)and Shanghai Key Laboratory for Particle Physics and CosmologyERC(Grant No.758462)European Union's Horizon 2020 research and innovation programme under Marie Sklodowska-Curie grant agreement(Grant No.894790)German Research Foundation DFG(Grant No.443159800),Collaborative Research Center CRC 1044,GRK 2149Istituto Nazionale di Fisica Nucleare,ItalyMinistry of Development of Turkey(Grant No.DPT2006K-120470)National Science and Technology fundNational Science Research and Innovation Fund(NSRF)via the Program Management Unit for Human Resources&Institutional Development,Research and Innovation(Grant No.B16F640076)Olle Engkvist Foundation(Grant No.200-0605)STFC(United Kingdom)Suranaree University of Technology(SUT),Thailand Science Research and Innovation(TSRI),and National Science Research and Innovation Fund(NSRF)(Grant No.160355)The Royal Society,UK(Grant Nos.DH140054,DH160214)The Swedish Research CouncilU.S.Department of Energy(Grant No.DE-FG02-05ER41374)。
文摘We report a search for a heavier partner of the recently observed Z_(cs)(3985)^(-) state,denoted as Z_(cs)^('-),in the process e^(+)e^(−)→K^(+)D_(s)^(∗−) D^(∗0 )+ c.c.,based on e^(*)e^(-)collision data collected at the center-of-mass energies of √s=4.661,4.682 and 4.699 GeV with the BESIII detector.The Z_(cs)^('-) is of interest as it is expected to be a candidate for a hidden-charm and open-strange tetraquark.A partial-reconstruction technique is used to isolate K^(+)recoil-mass spectra,which are probed for a potential contribution from Z_(cs)^('-)→D_(s)^(∗−) D^(∗0 )+ c.c.We find an excess of Z_(cs)^('-)→D_(s)^(*-)-D^(*0)(c.c.)candidates with a significance of 2.1o,after considering systematic uncertainties,at a mass of(4123.5±0.7_(sat)±4.7_(syst.))MeV/c^(2).As the data set is limited in size,the upper limits are evaluated at the 90%confidence level on the product of the Born cross sections(σ^(Borm))and the branching fraction(B)of Z_(cs)^('-)→D_(s)^(*-)-D^(*0),under different assumptions of the Z_(cs)^('-) mass from 4.120 to 4.140 MeV and of the width from 10 to 50 MeV at the three center-of-mass energies.The upper limits of σ^(Born).B are found to be at the level of O(1)pb at each energy.Larger data samples are needed to confirm the Z_(cs)^('-) state and clarify its nature in the coming years.
文摘Purpose A structure,used as a complex source of X-rays and neutron source,is designed with the assistance of CST module tool.Methods Particles of H-and electron,attracted from a plasma source,are designed to be separated by an energy selector.Soon after the separation,the trajectory and beam quality of H-are controlled by a special designation of potential barrier and potential well.And both particles are then accelerated by three pairs of pierce similar pole to an energy of 150 keV to produce X-rays/neutron.Results With proper optimization of structure and potential combination,a binocular structure with beam center distance of 15 mm,beam diameter smaller than 3.5 mm has been devised,which gives a feasible suggestion to produce two rays with one structure in the same time.
