Purpose Cosmogenic isotopes,known for their diverse types and relatively long lifetimes,are frequently treated as significant backgrounds in neutrino experiments.Particularly in the correlation events of inverse beta ...Purpose Cosmogenic isotopes,known for their diverse types and relatively long lifetimes,are frequently treated as significant backgrounds in neutrino experiments.Particularly in the correlation events of inverse beta decay(IBD)events of reactor neutrinos,addressing and removing'Li and 8He background is necessary.Similarly,for elastic scattering(ES)events of solar neutrinos,isotopes such as 12B and°Li have significant impacts.This study aims to identify an appropriate method for reducing the backgrounds in neutrino experiments.Methods In this paper,we conducted simulations of muon backgrounds in a liquid scintillator detector using Geant4 and explored the correlation between cosmogenic isotopes and muons.We introduced a novel method to distinguish cosmogenic isotopes from neutrino signals.Utilizing the relationship between the distance and time of spallation isotopes to muons and neutrons,we employed the TMVA(tools for multi-variable analysis)to distinguish neutrino signals from isotope backgrounds,achieving good performance.Results Compared with the traditional veto method,the efficiency has been improved by 1%for correlated events and 18%for single-event signals at the same background level.Conclusion This study presents a novel method for discriminating cosmogenic isotopic backgrounds,achieving a higher signal-to-noise ratio compared to traditional approaches,and showing good potential applicability to similar analyses in the future.展开更多
The Large High Altitude Air Shower Observatory(LHAASO) is a composite cosmic ray observatory consisting of three detector arrays: kilometer square array(KM2 A), which includes the electromagnetic detector array and mu...The Large High Altitude Air Shower Observatory(LHAASO) is a composite cosmic ray observatory consisting of three detector arrays: kilometer square array(KM2 A), which includes the electromagnetic detector array and muon detector array, water Cherenkov detector array(WCDA) and wide field-of-view Cherenkov telescope array(WFCTA). One of the main scientific objectives of LHAASO is to precisely measure the cosmic rays energy spectrum of individual components from 10^14 eV to 10^18 eV. The hybrid observation will be employed by the LHAASO experiment, in which the lateral and longitudinal distributions of extensive air shower can be observed simultaneously. Thus, many kinds of parameters can be used for primary nuclei identification. In this paper, high purity cosmic ray simulation samples of the light nuclei component are obtained using multi-variable analysis. The apertures of 1/4 LHAASO array for pure proton and mixed proton and helium(H&He) samples are 900 m^2 Sr and1800 m^2 Sr, respectively. Prospect of obtaining proton and H&He spectra from 100 TeV to 4 PeV is discussed.展开更多
In the LHC experiment, the H →γγ channel provides a clean final state with an effective mass peak that is reconstructed with great precision, despite the small branching ratio. As a consequence, the H →γγ channe...In the LHC experiment, the H →γγ channel provides a clean final state with an effective mass peak that is reconstructed with great precision, despite the small branching ratio. As a consequence, the H →γγ channel is one of the most promising channels for the Higgs discovery in the very low mass region. In order to increase the sensitivity of the Higgs search, background rejection rate is very important, so γ/π 0 discrimination is one of the key points in the analysis. At least 40% of photons will convert with the experience of ATLAS and CMS. We constructed electromagnetic calorimeter (ECAL) in GEANT4 simulation, using 6 variables which have different shapes between converted γ and π 0 , with the TMVA (Toolkit for Multivariate Data Analysis) to do the separation. With this method we can get 30% to 60% π 0 rejection efficiency when keeping 90% converted γ efficiency, in the region of transverse momentum 15 GeV to 75 GeV, not only in MC sumulation but also in real data.展开更多
文摘Purpose Cosmogenic isotopes,known for their diverse types and relatively long lifetimes,are frequently treated as significant backgrounds in neutrino experiments.Particularly in the correlation events of inverse beta decay(IBD)events of reactor neutrinos,addressing and removing'Li and 8He background is necessary.Similarly,for elastic scattering(ES)events of solar neutrinos,isotopes such as 12B and°Li have significant impacts.This study aims to identify an appropriate method for reducing the backgrounds in neutrino experiments.Methods In this paper,we conducted simulations of muon backgrounds in a liquid scintillator detector using Geant4 and explored the correlation between cosmogenic isotopes and muons.We introduced a novel method to distinguish cosmogenic isotopes from neutrino signals.Utilizing the relationship between the distance and time of spallation isotopes to muons and neutrons,we employed the TMVA(tools for multi-variable analysis)to distinguish neutrino signals from isotope backgrounds,achieving good performance.Results Compared with the traditional veto method,the efficiency has been improved by 1%for correlated events and 18%for single-event signals at the same background level.Conclusion This study presents a novel method for discriminating cosmogenic isotopic backgrounds,achieving a higher signal-to-noise ratio compared to traditional approaches,and showing good potential applicability to similar analyses in the future.
基金Supported by the National Key R&D Program of China(2018YFA0404201,2018YFA0404202)the Key Laboratory of Particle Astrophysics,Institute of High Energy Physics,CAS(Y5113D005C)National Natural Science Foundation(NSFC)(11563004,11775248)
文摘The Large High Altitude Air Shower Observatory(LHAASO) is a composite cosmic ray observatory consisting of three detector arrays: kilometer square array(KM2 A), which includes the electromagnetic detector array and muon detector array, water Cherenkov detector array(WCDA) and wide field-of-view Cherenkov telescope array(WFCTA). One of the main scientific objectives of LHAASO is to precisely measure the cosmic rays energy spectrum of individual components from 10^14 eV to 10^18 eV. The hybrid observation will be employed by the LHAASO experiment, in which the lateral and longitudinal distributions of extensive air shower can be observed simultaneously. Thus, many kinds of parameters can be used for primary nuclei identification. In this paper, high purity cosmic ray simulation samples of the light nuclei component are obtained using multi-variable analysis. The apertures of 1/4 LHAASO array for pure proton and mixed proton and helium(H&He) samples are 900 m^2 Sr and1800 m^2 Sr, respectively. Prospect of obtaining proton and H&He spectra from 100 TeV to 4 PeV is discussed.
基金Supported by Natural Science Foundation of China (10435070, 10773011, 10721140381, 10099630)China Ministry of Science and Technology (2007CB16101, 2010CB833000)
文摘In the LHC experiment, the H →γγ channel provides a clean final state with an effective mass peak that is reconstructed with great precision, despite the small branching ratio. As a consequence, the H →γγ channel is one of the most promising channels for the Higgs discovery in the very low mass region. In order to increase the sensitivity of the Higgs search, background rejection rate is very important, so γ/π 0 discrimination is one of the key points in the analysis. At least 40% of photons will convert with the experience of ATLAS and CMS. We constructed electromagnetic calorimeter (ECAL) in GEANT4 simulation, using 6 variables which have different shapes between converted γ and π 0 , with the TMVA (Toolkit for Multivariate Data Analysis) to do the separation. With this method we can get 30% to 60% π 0 rejection efficiency when keeping 90% converted γ efficiency, in the region of transverse momentum 15 GeV to 75 GeV, not only in MC sumulation but also in real data.