A combined unit, which has the ability to measure the current and emittance of the high intensity direct current（DC）ion beam, is developed at Peking University（PKU）. It is a multi-slit single-wire（MSSW）-type bea...A combined unit, which has the ability to measure the current and emittance of the high intensity direct current（DC）ion beam, is developed at Peking University（PKU）. It is a multi-slit single-wire（MSSW）-type beam emittance meter combined with a water-cooled Faraday Cup, named high intensity beam emittance measurement unit-6（HIBEMU-6）. It takes about 15 seconds to complete one measurement of the beam current and its emittance. The emittance of a 50-mA@50-kV DC proton beam is measured.展开更多
We report the methods and plans for measuring the differential cross section of J/ψ→μ^＋μ^- production, using data to be collected in the first LHC run by the CMS detector. Making use of the large B-hadron lifetim...We report the methods and plans for measuring the differential cross section of J/ψ→μ^＋μ^- production, using data to be collected in the first LHC run by the CMS detector. Making use of the large B-hadron lifetime, we show how to separate the promptly produced J/ψ’s from those coming from B-hadron decays. Since the J/ψ production cross section is expected to be large, the analysis should be viable with relatively small data sets, that will become available early in the startup of the LHC. We also address effects of a non-perfect detector alignment, as well as systematic uncertainties. About 70 thousand J/ψ decays are reconstructed from Monte Carlo data, which corresponds to an integrated luminosity of 3 pb^-1 in 14 TeV collisions, in the range of pT^J/ ψbetween 5 and 40 GeV/c. The precision of the result is limited by systematic uncertainties, and is at the 15% level.展开更多
The state equation for strangeon matter is very stiff due to the non-relativistic nature of its particles and their repulsive interaction, such that pulsar masses as high as ～ 3M would be expected. However, an adiaba...The state equation for strangeon matter is very stiff due to the non-relativistic nature of its particles and their repulsive interaction, such that pulsar masses as high as ～ 3M would be expected. However, an adiabatic sound speed, cs = √P/ρ, is usually superluminal in strangeon matter, and the dynamic response of a strangeon star （e.g., binary merger） is not tractable in numerical simulations. In this study, we examined signal propagation in strangeon matter and calculate the actual propagation speed, Csignal. We found that the causality condition, Csignal 〈 c, is satisfied and the signal speed is presented as a function of stellar radius.展开更多
In this paper the J/ψ→μ^＋μ^- reconstruction performance in the CMS experiment at the LHC is studied in detail by using B8→J/ψφ→μμKK events. The reconstruction efficiencies of J/ψ mesons and their decay muo...In this paper the J/ψ→μ^＋μ^- reconstruction performance in the CMS experiment at the LHC is studied in detail by using B8→J/ψφ→μμKK events. The reconstruction efficiencies of J/ψ mesons and their decay muons are obtained as a function of the transverse momentum PT and the pseudo-rapidity η. We also study the muon trigger efficiency for this channel with the planned Level-1 trigger and High Level Trigger selection criteria. It was observed that the muon reconstruction efficiency decreases when the two decay muons have a small or large 3D angular separation, which further affects the overall J/ψ reconstruction efficiency.展开更多
基金Project supported by the National Basic Research Program of China(Grant No.2014CB845502)the National Natural Science Foundation of China(Grant No.91126004)
文摘A combined unit, which has the ability to measure the current and emittance of the high intensity direct current（DC）ion beam, is developed at Peking University（PKU）. It is a multi-slit single-wire（MSSW）-type beam emittance meter combined with a water-cooled Faraday Cup, named high intensity beam emittance measurement unit-6（HIBEMU-6）. It takes about 15 seconds to complete one measurement of the beam current and its emittance. The emittance of a 50-mA@50-kV DC proton beam is measured.
基金Supported by NSFC (10099630)Ministry of Science and Technology of China (2007CB816101)
文摘We report the methods and plans for measuring the differential cross section of J/ψ→μ^＋μ^- production, using data to be collected in the first LHC run by the CMS detector. Making use of the large B-hadron lifetime, we show how to separate the promptly produced J/ψ’s from those coming from B-hadron decays. Since the J/ψ production cross section is expected to be large, the analysis should be viable with relatively small data sets, that will become available early in the startup of the LHC. We also address effects of a non-perfect detector alignment, as well as systematic uncertainties. About 70 thousand J/ψ decays are reconstructed from Monte Carlo data, which corresponds to an integrated luminosity of 3 pb^-1 in 14 TeV collisions, in the range of pT^J/ ψbetween 5 and 40 GeV/c. The precision of the result is limited by systematic uncertainties, and is at the 15% level.
基金supported by the National Key R&D Program of China(Grant No.2017YFA0402600)the National Natural Science Foundation of China(Grant No.11225314)+1 种基金the Open Project Program of the Key Laboratory of Radio Astronomy and the Open Project Program of the Key Laboratory of FAST,NAOC,Chinese Academy of SciencesThe FAST FELLOWSHIP is supported by Special Funding for Advanced Users,budgeted and administrated by Center for Astronomical Mega-Science,Chinese Academy of Sciences(CAMS)
文摘The state equation for strangeon matter is very stiff due to the non-relativistic nature of its particles and their repulsive interaction, such that pulsar masses as high as ～ 3M would be expected. However, an adiabatic sound speed, cs = √P/ρ, is usually superluminal in strangeon matter, and the dynamic response of a strangeon star （e.g., binary merger） is not tractable in numerical simulations. In this study, we examined signal propagation in strangeon matter and calculate the actual propagation speed, Csignal. We found that the causality condition, Csignal 〈 c, is satisfied and the signal speed is presented as a function of stellar radius.
基金Supported by NSFC (10435070, 10099630)Ministry of Science and Technology of China (2007CB816101)
文摘In this paper the J/ψ→μ^＋μ^- reconstruction performance in the CMS experiment at the LHC is studied in detail by using B8→J/ψφ→μμKK events. The reconstruction efficiencies of J/ψ mesons and their decay muons are obtained as a function of the transverse momentum PT and the pseudo-rapidity η. We also study the muon trigger efficiency for this channel with the planned Level-1 trigger and High Level Trigger selection criteria. It was observed that the muon reconstruction efficiency decreases when the two decay muons have a small or large 3D angular separation, which further affects the overall J/ψ reconstruction efficiency.
