检索结果-南通市图书馆

Weak decays of doubly heavy baryons:"decay constants"

在线全文

学校读者我要写书评

暂无评论

Chinese Physics C 2018年第12期42卷 9-18页

作者： Xiao-Hui nu Yue-Long Shen Wei Wang Zhen-Xing Zhao INPAC Shanghai Key Laboratory for Particle Physics and CosmologyMOE Key Laboratory for Particle PhysicsAstrophysics and CosmologySchool of Physics and AstronomyShanghai Jiao-Tong UniversityShanghai 200240China College of Information Science and Engineering Ocean University of ChinaQingdao 266100China

Inspired by the recent observation of the ∑c^＋c^＋ by the LHCb Collaboration, we explore the ＂decay constants＂ of doubly heavy baryons in the framework of QCD sum rules. With the ∑cc,∑bb, and Ωcc,Ωbc,Ωbb baryons interpolated by three-quark operators, we calculate the correlation functions using the operator product expansion and include the contributions from operators up to dimension six. On the hadron side, we consider both contributions from the lowest-lying states with J^P 1/2^＋ and from negative parity baryons with JP=1/2^-. We find that the results are stable and the contaminations from negative parity baryons are not severe. These results are ingredients for the QCD study of weak decays and other properties of doubly-heavy baryons.

关键词： doubly heavy baryons decay constant QCD sum rules

Deprojection technique for galaxy cluster considering the point spread function

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2010年第S1期53卷 183-186页

作者： WANG YuSa,JIA ShuMei & CHEN Yong key laboratory for particle astrophysics,Institute of High Energy Physics,Chinese Academy of Sciences,Beijing 100049,China key laboratory for particle astrophysics Institute of High Energy Physics Chinese Academy of Sciences Beijing China

We present a new method for the analysis of Abell 1835 observed by *** method is a combination of the Direct Demodulation technique and *** eliminate the effects of the point spread function(PSF) with the Direct Demodulation *** then use a traditional deprojection technique to study the properties of Abell *** to only using a deprojection method,the central electron density derived from this method increases by 30%,while the temperature profile is similar.

关键词： PSF Direct Demodulation deprojection Abell 1835 galaxy cluster XMM-Newton

Light collection of the POLAR detector

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2010年第S1期53卷 43-46页

作者： DONG YongWei,LI YanGuo,WU BoBing,ZHANG YongJie & ZHANG ShuangNan key laboratory of particle astrophysics,Institute of High Energy Physics,Chinese Academy of Sciences,Beijing 100049,China key laboratory of particle astrophysics Institute of High Energy Physics Chinese Academy of Sciences Beijing China

POLAR is a compact polarimeter dedicated to measuring the polarization of GRBs between 50-350 *** light collection of 200 mm×6 mm×6 mm plastic bars has been simulated and optimized in order to get uniform response to X-rays at different points along one single *** to the Monte Carlo results,the amplitude uniformity strongly depends on the level of polishing of the scintillator surface and the covering.A uniformity of 89% is achieved with a prototype constructed by a non position-sensitive PMT and an array of 4×4 bars.

关键词： plastic scintillator light collection gamma-ray burst polarimeter

Probing primordial gravitational waves: Ali CMB Polarization Telescope

在线全文

学校读者我要写书评

暂无评论

National Science Review 2019年第1期6卷 145-154页

作者： Hong Li Si-Yu Li Yang Liu Yong-Ping Li Yifu Cai Mingzhe Li Gong-Bo Zhao Cong-Zhan Liu Zheng-Wei Li He Xu Di Wu Yong-Jie Zhang Zu-Hui Fan Yong-Qiang Yao Chao-Lin Kuo Fang-Jun Lu Xinmin Zhang key laboratory of particle astrophysics Institute of High Energy Physics Chinese Academy of Sciences Theoretical Physics Division Institute of High Energy PhysicsChinese Academy of Sciences University of Chinese Academy of Sciences CAS key laboratory for Researches in Galaxies and Cosmology Department of AstronomyUniversity of Scienceand Technology of China Interdisciplinary Center for Theoretical Study University of Science and Technology of China National Astronomical Observatories Chinese Academy of Sciences Institute of Cosmology& Gravitation University of Portsmouth key laboratory of particle astrophysics Institute of High EnergyPhysics Chinese Academy of Sciences key laboratory of particle astrophysics Institute of High Energy Physics ChineseAcademy of Sciences Department of Astronomy School of Physics Peking University Physics Department Stanford University

In this paper, we will give a general introduction to the Ali CMB Polarization Telescope(Ali CPT) project,which is a Sino–US joint project led by the Institute of High Energy Physics and involves many different institutes in China. It is the first ground-based Cosmic Microwave Background(CMB) polarization experiment in China and an integral part of China’s Gravitational-wave Program. The main scientific goal of the Ali CPT project is to probe the primordial gravitational waves(PGWs) originating from the very early Universe. The AliCPT project includes two stages. The first stage, referred to as AliCPT-1, is to build a telescope in the Ali region of Tibet at an altitude of 5250 meters. Once completed, it will be the highest ground-based CMB observatory in the world and will open a new window for probing PGWs in the northern hemisphere. The AliCPT-1 telescope is designed to have about 7000 transition-edge sensor detectors at 95 GHz and 150 GHz. The second stage is to have a more sensitive telescope(Ali CPT-2) with more than 20 000 detectors. Our simulations show that AliCPT will improve the current constraint on the tensor-to-scalar ratio r by one order of magnitude with three years’ observation. Besides the PGWs, Ali CPT will also enable a precise measurement of the CMB rotation angle and provide a precise test of the CPT symmetry. We show that three years’ observation will improve the current limit by two orders of magnitude.

关键词： primordial gravitational waves cosmic microwave background Ali CMB Polarization Telescope

Bayesian inference on isospin splitting of nucleon effective mass from giant resonances in^(208)Pb

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Chinese Physics C 2021年第6期45卷 158-166页

作者： Zhen Zhang Xue-Bin Feng Lie-Wen Chen Sino-French Institute of Nuclear Engineering and Technology Sun Yat-sen UniversityZhuhai 519082China School of Physics and Astronomy Shanghai Key Laboratory for Particle Physics and Cosmologyand Key Laboratory for Particle Astrophysics and Cosmology(MOE)Shanghai Jiao Tong UniversityShanghai 200240China

From a Bayesian analysis of the electric dipole polarizability,the constrained energy of isovector giant dipole resonance,the peak energy of isocalar giant quadrupole resonance,and the constrained energy of isocalar gi-ant monopole resonance in 208Pb,we extract the isoscalar and isovector effective masses in nuclear matter at satura-tion density ρ0 as m^(*)_(s.0)/m=0.87^(+)_(-004) and m^(*)_(v.0)/m=0.78^(+006)_(-006),respectively,at 90%confdence *** con-straints obtained on m^(*)_(d.0) and m^(*)_(v.0) lead to a positive isospin splitting of nucleon effective mass in asymmetric nuclear matter of isospin asymmetry σ at ρ0 as m^(*)_(n-p)/m=(0.20^(0.15)_(0.14)σ.In addition,the symmetry energy at the subsatura-tion density ρ^(*)=0.05 fm^(-3) is determined to be E_(sym)(ρ^(*))=16.7±1.3 MeV at 90%confidence level.

关键词： nucleon effective mass isospin splitting of nucleon effective mass symmetry energy nuclear giant resonance Bayesian analysis

A Deprojection Analysis of Abell 1650 with XMM-Newton

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Astronomy and astrophysics 2006年第2期6卷 181-196页

作者： Shu-Mei Jia Yong Chen Li Chen Department of Astronomy Beijing Normal University Beijing 100875 key laboratory of particle astrophysics Institute of High Energy Physics Chinese Academyof Sciences Beijing 100049

We revisit the XMM-Newton observation of the galaxy cluster Abell 1650 with a deprojection technique. We find that the radial deprojected spectra of Abell 1650 can be marginally fitted by a single-temperature model. In order to study the properties of the central gas, we fit the spectra of the central two regions with a two- temperature model. The fits then become significantly better and the cool gas about 1～2 keV can be connected with the gas cooling. Fitting the central spectrum （r≤1′） by using a cooling flow model with an isothermal component yields a small mass deposition rate of 10-7^＋11 M. yr^-1, while the standard cooling flow model can not fit this spectrum satisfactorily except that there exists a cut-off temperature having a level of about 3 keV. From the isothermal model we derive the deprojected electron density profile ne（r）, and then together with the deprojected temperature profile the total mass and gas mass fraction of cluster are also determined. We compare the properties of Abell 1650 with those of Abell 1835 （a large cooling flow cluster） and some other clusters, to explore the difference in properties between large and small cooling flow cluster, and what causes the difference in the cooling flow of different clusters. It has been shown that Abell 1835 has a steeper potential well and thus a higher electron density and a lower temperature in its center, indicating that the shape of the gravitational potential well in central region determines the cooling flow rates of clusters. We calculate the potential, internal and radiated energies of these two clusters, and find that the gas energies in both clusters are conserved during the collapsing stage.

关键词： galaxies: clusters: individual: Abell 1650 -galaxies: cooling flowsgalaxies: evolution - galaxies: intergalactic medium - X-rays: galaxies: clusters

Geometry of Broad Line Regions of Active Galactic Nuclei

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Astronomy and astrophysics 2008年第1期8卷 50-62页

作者： Xiao-Rong Lü1 key laboratory for particle astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 2 Graduate School of Chinese Academy of Sciences, Beijing 100049 key laboratory for particle astrophysics Institute of High Energy Physics Chinese Academy of Sciences Beijing 100049 Graduate School of Chinese Academy of Sciences Beijing 100049

It has long remained an open question as to the geometry of the broad line region （BLR） in active galactic nuclei （AGNs）. The reverberation mapping technique which measures the response of the broad emission lines to the ionizing continuum, when combined with multiwavelength continuum fitted by sophisticated accretion disks, provides a way of probing the BLR geometry. We analyze a sample of 35 AGNs, which have been monitored by the reverberation mapping campaign. In view of energy budget, the reverberation-based BH masses are found to be in agreement with those obtained by accretion disk models in two thirds of the present sample while the reverberation mapping methods underestimate the BH masses in about one third of objects, as also suggested by CoUin et al. in a recent work. We point out that there are obviously two kinds of BLR geometry, which are strongly dependent on the Eddington ratio, and separated by the value LBol/LEdd - 0.1. These results prefer a scenario of the disk and wind configuration of the BLR and identify the Eddington ratio as the physical driver regulating the wind in the BLR.

关键词： accretion, accretion disks - galaxies active - galaxies Seyfert - quasars general

New evidence for lack of CMB power on large scales

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2010年第3期53卷 567-570页

作者： LIU Hao1 & LI TiPei1,2,3 1 key laboratory of particle astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China 2 Department of Physics & Center for astrophysics, Tsinghua University, Beijing 100084, China 3 Department of Engineering Physics & Center for astrophysics, Tsinghua University, Beijing 100084, China key laboratory of particle astrophysics Institute of High Energy Physics Chinese Academy of Sciences Beijing China Department of Physics & Center for astrophysics Tsinghua University Beijing China Department of Engineering Physics & Center for astrophysics Tsinghua University Beijing China

A digitalized temperature map is recovered from the first light sky survey image published by the Planck team, from which an angular power spectrum of the cosmic microwave background (CMB) is derived. The amplitudes of the low multipoles (low-l) measured from the preliminary Planck power spectrum are significantly lower than those reported by the WMAP team. Possible systematical effects are far from enough to explain the observed low-l differences.

关键词： cosmology cosmic microwave background data analysis

The rms-flux relation of Cyg X-2 in the horizontal branch

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2010年第S1期53卷 86-90页

作者： LI ZhiBing,LEI YaJuan,QU JinLu,ZHANG Shu & SONG LiMing key laboratory for particle astrophysics,Institute of High Energy Physics,Chinese Academy of Sciences(CAS),Beijing 100049,China key laboratory for particle astrophysics Institute of High Energy Physics Chinese Academy of Sciences (CAS) Beijing China

We have investigated the relation between the root mean square(rms) variability and the X-ray flux(rms-flux relation) of the Z source Cyg X-2,and as well the energy dependence based on the Rossi X-ray Timing Explorer(RXTE) *** currently focus on the horizontal branch(HB),due to the negative correlation in flux of the soft and the hard *** rms-flux correlation has energy dependence as follows:positive at hard X-rays(above 10 keV) but negative at soft X-rays(below 10 keV).This provides a feature different from the previous one,and may be suggestive of different origins of X-rays below and above 10 ***,the overall spectrum can be well fitted with a model consisting of a blackbody and Comptonization components,but the fitting results do not reveal any features around 10 keV that could account for such a change in the rms-flux relation.

关键词： accretion accretion disk—binaries:close-stars:individual(Cygnus X-2)-X-rays:binaries