Baryon numbers are theorized to be carried by valence quarks in the standard QCD picture of the baryon structure.Another theory proposed an alternative baryon number carrier,a non-perturbative Y-shaped configuration o...Baryon numbers are theorized to be carried by valence quarks in the standard QCD picture of the baryon structure.Another theory proposed an alternative baryon number carrier,a non-perturbative Y-shaped configuration of the gluon field,called the baryon junction in the 1970s.However,neither of these theories has been verified experimentally.Recently,searching for the baryon junction by investigating the correlation of net-charge and net-baryon yields at midrapidity in heavy-ion collisions has been suggested.This paper presents studies of such correlations in collisions of various heavy ions from oxygen to uranium with the UrQMD Monte Carlo model.The UrQMD model implements valence quark transport as the primary means of charge and baryon stopping at midrapidity.Detailed studies are also conducted for isobaric ^(96)_(40)Zr+^(96)_(40)Zr and ^(96)_(44)Ru+^(96)_(44)Ru collisions.We found a universal trend of charge stopping with respect to baryon stopping and discovered that the charge stopping is always greater than the baryon stopping.This study provides a model baseline in valence quark transport for what is expected in net-charge and net-baryon yields at the midrapidity of relativistic heavy-ion collisions.展开更多
Understanding the gluonic structure in nuclei is one of the most important goals in modern nuclear physics,for which J/ψphotoproduction is suggested as a powerful tool to probe the gluon density distribution.The expe...Understanding the gluonic structure in nuclei is one of the most important goals in modern nuclear physics,for which J/ψphotoproduction is suggested as a powerful tool to probe the gluon density distribution.The experimental investigation of the photoproduction process is conventionally studied in ultra-peripheral heavy-ion collisions,and has recently been extended to hadronic collisions.However,theoretical efforts in hadronic heavy-ion collisions are still lacking in the literature.In this paper,we build up a phenomenological framework to calculate the differential momentum transfer spectra for J/ψphotoproduction in hadronic heavy-ion collisions based on a vector meson dominance model.For the first time,we include the effect of internal photon radiation in the calculations,and we find that the results with internal photon radiation could describe the experimental measurements from STAR very well.展开更多
Purpose In order to improve the charged particle identi-fication capability,end-cap time-of-flight(ETOF)detector of the Beijing Spectrometer(BESIII)has been upgraded with multi-gap resistive plate chamber(MRPC)technol...Purpose In order to improve the charged particle identi-fication capability,end-cap time-of-flight(ETOF)detector of the Beijing Spectrometer(BESIII)has been upgraded with multi-gap resistive plate chamber(MRPC)technology,aiming at an overall time resolution of 80 ps for minimum-ionization particles to extend the K/πseparation(2σ)momentum range to 1.4 GeV/c.Methods The previous version of ETOF in BESIII consisted of plastic scintillators.The multi-hit events distort both shape and amplitude of the output signals.MRPC technique was chosen for the BESIII ETOF upgrade as it provides high time resolution and high detection efficiency,is of relatively low cost and is insensitive to neutral particles.Most importantly,the fine segmentation of the MRPC readout stripes can suppress multi-hit events effectively.Results The final design of MRPC module for ETOF is characterized by double-stack(2×6)structure,dual-end readout mode and precision electronics.To batch-produce and test these MRPC modules,a series of tools and production procedures as well as related performance simulation and test methods were developed.Results showed that each MRPC module’s intrinsic time resolution(including the electronics contribution)is around 50 ps and the efficiency is better than 97%.The overall performance of the upgraded ETOF is better than the designed index.The new ETOF has been successfully installed at BESIII and run in 2016.展开更多
基金the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB34030000)the National Key Research and Development Program of China(2022YFA1604900)the U.S.DOE Office of Science365 under contract(DE-SC0012704,DE-FG02-10ER41666,DE-AC02-98CH10886)。
文摘Baryon numbers are theorized to be carried by valence quarks in the standard QCD picture of the baryon structure.Another theory proposed an alternative baryon number carrier,a non-perturbative Y-shaped configuration of the gluon field,called the baryon junction in the 1970s.However,neither of these theories has been verified experimentally.Recently,searching for the baryon junction by investigating the correlation of net-charge and net-baryon yields at midrapidity in heavy-ion collisions has been suggested.This paper presents studies of such correlations in collisions of various heavy ions from oxygen to uranium with the UrQMD Monte Carlo model.The UrQMD model implements valence quark transport as the primary means of charge and baryon stopping at midrapidity.Detailed studies are also conducted for isobaric ^(96)_(40)Zr+^(96)_(40)Zr and ^(96)_(44)Ru+^(96)_(44)Ru collisions.We found a universal trend of charge stopping with respect to baryon stopping and discovered that the charge stopping is always greater than the baryon stopping.This study provides a model baseline in valence quark transport for what is expected in net-charge and net-baryon yields at the midrapidity of relativistic heavy-ion collisions.
基金Supported by the National Natural Science Foundation of China (12005220, 12175223)MOST (2018YFE0104900)
文摘Understanding the gluonic structure in nuclei is one of the most important goals in modern nuclear physics,for which J/ψphotoproduction is suggested as a powerful tool to probe the gluon density distribution.The experimental investigation of the photoproduction process is conventionally studied in ultra-peripheral heavy-ion collisions,and has recently been extended to hadronic collisions.However,theoretical efforts in hadronic heavy-ion collisions are still lacking in the literature.In this paper,we build up a phenomenological framework to calculate the differential momentum transfer spectra for J/ψphotoproduction in hadronic heavy-ion collisions based on a vector meson dominance model.For the first time,we include the effect of internal photon radiation in the calculations,and we find that the results with internal photon radiation could describe the experimental measurements from STAR very well.
基金supported by the National Natural Science Foundation of China(Nos.10979003,11675172,U1232206)Chinese Academy of Sciences(No.1G201331231172010).
文摘Purpose In order to improve the charged particle identi-fication capability,end-cap time-of-flight(ETOF)detector of the Beijing Spectrometer(BESIII)has been upgraded with multi-gap resistive plate chamber(MRPC)technology,aiming at an overall time resolution of 80 ps for minimum-ionization particles to extend the K/πseparation(2σ)momentum range to 1.4 GeV/c.Methods The previous version of ETOF in BESIII consisted of plastic scintillators.The multi-hit events distort both shape and amplitude of the output signals.MRPC technique was chosen for the BESIII ETOF upgrade as it provides high time resolution and high detection efficiency,is of relatively low cost and is insensitive to neutral particles.Most importantly,the fine segmentation of the MRPC readout stripes can suppress multi-hit events effectively.Results The final design of MRPC module for ETOF is characterized by double-stack(2×6)structure,dual-end readout mode and precision electronics.To batch-produce and test these MRPC modules,a series of tools and production procedures as well as related performance simulation and test methods were developed.Results showed that each MRPC module’s intrinsic time resolution(including the electronics contribution)is around 50 ps and the efficiency is better than 97%.The overall performance of the upgraded ETOF is better than the designed index.The new ETOF has been successfully installed at BESIII and run in 2016.
