Lead contamination in the City of Flint, MI has been well documented over the past two years, with lead levels above the EPA Action Level until summer 2016. This resulted from an ill-fated decision to switch from Detr...Lead contamination in the City of Flint, MI has been well documented over the past two years, with lead levels above the EPA Action Level until summer 2016. This resulted from an ill-fated decision to switch from Detroit water（Lake Huron） with corrosion control, to Flint River water without corrosion control. Although lead levels are now closer to normal,reports of skin rashes have sparked questions surrounding tap water in some Flint homes.This study investigated the presence of contaminants, including disinfection by-products（DBPs）, in the hot tap water used for showering in the homes of residents in Flint. Extensive quantitative analysis of 61 regulated and priority unregulated DBPs was conducted in Flint hot and cold tap water, along with the analysis of 50 volatile organic compounds and a nontarget comprehensive, broadscreen analysis, to identify a possible source for the reported skin rashes. For comparison, chlorinated hot and cold waters from three other cities were also sampled, including Detroit, which also uses Lake Huron as its source water.Results showed that hot water samples generally contained elevated levels of regulated and priority unregulated DBPs compared to cold water samples, but trihalomethanes were still within regulatory limits. Overall, hot shower water from Flint was similar to waters sampled from the three other cities and did not have unusually high levels of DBPs or other organic chemicals that could be responsible for the skin rashes observed by residents. It is possible that an inorganic chemical or microbial contaminant may be responsible.展开更多
The Leonid meteor shower in November 1998 was observed widely by astronomers. The first peak, rich in bright meteors, appeared about 16 hours before the predicted maximum of the main shower. The main shower was also o...The Leonid meteor shower in November 1998 was observed widely by astronomers. The first peak, rich in bright meteors, appeared about 16 hours before the predicted maximum of the main shower. The main shower was also observed by both optical and radio methods during 19:00-21:00 UT on Nov. 17, and the radio peak was over 2500h-1. About 18 hours after the main shower, an abnormal phenomenon in the ionosphere was detected by two separate ionosphere observing stations. And the very high abnormal phenomenon maintained over one hour. The phenomenon showed that the ionosphere was injected with a large amount of small dust particles that could not be observed in optical and radio. The Observational results show that the Leonid meteor shower in 1998 had three peaks.展开更多
Human exposure to radon inside different parts of the house has become a great concern. In this study, the distribution of radon and its decay inside the shower will be numerically investigated. In fact, the radon con...Human exposure to radon inside different parts of the house has become a great concern. In this study, the distribution of radon and its decay inside the shower will be numerically investigated. In fact, the radon concentration in water is measured through the use of AlphaGUARD. They are used as an input for CFD simulation. The numerical results proved that temperature and humidity have significant impacts on both radon content and distribution. Also, the equilibrium factor variations between radon and its progeny with the temperature and relative humidity were carefully looked at. The equivalent doses due to <sup>218</sup>Po and <sup>214</sup>Po were evaluated in different tissues of the respiratory tract of the members of the public from the inhalation of air inside the shower. The annual effective dose due to radon short lived decay from the inhalation of air inside the shower by the members of the public was also investigated.展开更多
Technology always brings us surprise and change life everyday. What you said,when you do your wool suits domestic cleaning with warm water at about 40° C,at your bathroom?Crazy?Easy-care?Wow,it's all about Me...Technology always brings us surprise and change life everyday. What you said,when you do your wool suits domestic cleaning with warm water at about 40° C,at your bathroom?Crazy?Easy-care?Wow,it's all about MerinoFreshTM!展开更多
Showers with large zenith angles are observed in emulsion chambers exposed at Mt.Kanbala.The intensity of high energy muons is given and the multicore showers with large zenith angles are found.It is indicated that a ...Showers with large zenith angles are observed in emulsion chambers exposed at Mt.Kanbala.The intensity of high energy muons is given and the multicore showers with large zenith angles are found.It is indicated that a new phenomenon may exist in the high energy nuclear interactions of cosmic rays.展开更多
Extensive Air Showers(EAS)induced by cosmic ray particles of very low energies,owing to the significantly steep cosmic ray energy spectrum,dominate the secondary particle flux measured by single detectors and small sh...Extensive Air Showers(EAS)induced by cosmic ray particles of very low energies,owing to the significantly steep cosmic ray energy spectrum,dominate the secondary particle flux measured by single detectors and small shower arrays.Such arrays connected in extended networks can be used to determine potentially interesting spatial correlations between showers,which may shed new light on the nature of ultra high-energy cosmic rays.The quantitative interpretation of showers recorded by small local arrays requires a methodology that differs from that used by ordinary large EAS arrays operating in the"knee"region and above.We present"small EAS generator,"a semi-analytical method for integrating cosmic ray spectra over energies of interest and summing over the mass spectra of primary nuclei in arbitrary detector configurations.Furthermore,we provide results on the EAS electron and muon fluxes and particle density spectra.展开更多
Gamma ray source detection above 30 TeV is an encouraging approach for finding galactic cosmic ray sources. All sky survey for gamma ray sources using wide field of view detector is essential for population accumulati...Gamma ray source detection above 30 TeV is an encouraging approach for finding galactic cosmic ray sources. All sky survey for gamma ray sources using wide field of view detector is essential for population accumulation for various types of sources above 100 GeV. In order to target those goals, a large air shower particle detector array of 1 km^2 （the LHAASO project） at 4300 m a.s.l, is proposed, By adding two MagicⅡ- type telescopes in the array as proposed, LHAASO will be enhanced in source morphologic investigation power. The proposed array will be utilized also for energy spectrum measurement for individual cosmic ray species above 30 TeV. By re-configuring the wide field of view telescopes into fluorescence light detector array, the aperture of the detector array can be enlarged to cover an energy region above 100 PeV where the second knee is located. Cosmic ray spectrum and composition will be measured in order to transfer an energy scale to ultra high energy cosmic ray experiments.展开更多
This review focuses on high-energy cosmic rays in the PeV energy range and above. Of particular interest is the knee of the spectrum around 3 PeV and the transition from cosmic rays of Galactic origin to particles fro...This review focuses on high-energy cosmic rays in the PeV energy range and above. Of particular interest is the knee of the spectrum around 3 PeV and the transition from cosmic rays of Galactic origin to particles from extra-galactic sources. Our goal is to establish a baseline spectrum from 1014 to 10^20 eV by combining the results of many measurements at different energies. In combination with measurements of the nuclear composition of the primaries, the shape of the energy spectrum places constraints on the number and spectra of sources that may contribute to the observed spectrum.展开更多
A shower cloud observed in Jiangxi,a hailstorm observed in Hebei and“75.8”torrential rain in Henan are simulated with our microphysical model in a one-dimensional framework.The model,using the radio- sonde data as i...A shower cloud observed in Jiangxi,a hailstorm observed in Hebei and“75.8”torrential rain in Henan are simulated with our microphysical model in a one-dimensional framework.The model,using the radio- sonde data as input,gets its output which shows agreement in many aspects as compared with observations in each case.The glaciation of small cumulus cloud,low precipitation efficiency of hailstorm and the per- sistence of torrential rain are demonstrated.It is also shown that the Bergeron process has little influence, but the warm-rain process plays an important role in the formation of precipitation in cumulonimbus with a warm cloud base.展开更多
In this paper, we studied the development of hadronic shower in an electromagnetic calorimeter of Alpha Magnetic Spectrometer Ⅱ. Two parametrized empirical formulae were proposed to describe the hadronic shower shape...In this paper, we studied the development of hadronic shower in an electromagnetic calorimeter of Alpha Magnetic Spectrometer Ⅱ. Two parametrized empirical formulae were proposed to describe the hadronic shower shape in calorimeter. Using 100 GeV proton beam incident on the center of the ECAL, detailed plots of lateral and longitudinal hadronic shower behavior were given and we found the formulae can describe the development of the hadronic shower with the test beam data. The possible application of the parametrized formulae including e±-π± discrimination and tau jet reconstruction was discussed.展开更多
Here is the first report on the observation of meteor ablation trails with lidar in China.Four long-lived Na ablation trails were observed during the 18/19 Nov.2001 Leonid meteor shower with a sodium resonance lidar o...Here is the first report on the observation of meteor ablation trails with lidar in China.Four long-lived Na ablation trails were observed during the 18/19 Nov.2001 Leonid meteor shower with a sodium resonance lidar over Wuhan.The mean altitude of the 4 trails is 97.95 km,consistent with Leouid high entry velocity(-72km/s).The peak density averages about 3380±3633cm^-3,and the abundance is(2.33±1.49)×10^(8)cm^(-2),both of which are higher than those previously observed for sporadic meteor trails.The RMS width is 359 m and the meteor's age is 81 min,indicating that they are long duration meteor trails.These observation results are quite different from those of sporadic meteor trails,but comparable to the 1998 and 1999 Leonid report.Five night observations from 17 Nov.to 23 Nov.suggest that the 2001 Leouid meteor shower does not have a significant impact on the abundance of the background Na layer.展开更多
The precision study of W^-W^+H production with subsequent W^±→l^±vl^(-)and H→bb decays at the Large Hadron Collider(LHC)aids in the investigation of Higgs gauge couplings and the search for new physics bey...The precision study of W^-W^+H production with subsequent W^±→l^±vl^(-)and H→bb decays at the Large Hadron Collider(LHC)aids in the investigation of Higgs gauge couplings and the search for new physics beyond the standard model.In this study,we calculate the shower-matched next-to-leading order QCD and electroweak(EW)corrections from the qq annihilation and photon-induced channels to the W^-W^+H production at the 14 TeV LHC.We deal with the subsequent decays of Higgs and W^±bosons by adopting the MADSPIN method.Both the integrated cross section and some kinematic distributions of W^±,H,and their decay products are provided.We find that the QCD correction significantly enhances the leading-order differential cross section,while the EW correction from the qq annihilation channel obviously suppresses it,especially in the high energy phase-space region,due to the Sudakov effect.The qy-and yy-induced relative corrections are positive and insensitive to the transverse momenta of W^±,H,and their decay products.These photon-induced corrections compensate the negative qq-initiated EW correction,and become the dominant EW contribution as the increment of the pp colliding energy.The parton shower(PS)effects on kinematic distributions are not negligible.The relative PS correction to the b-jet transverse momentum distribution can exceed 100%in the high p_(T,b)region.Moreover,we investigate the scale and PDF uncertainties,and find that the theoretical error of the QCD+EW+qγ+γγ-corrected integrated cross section mainly originates from the renormalization scale dependence of the QCD correction.展开更多
By a Monte Carlo simulation, the arrival time (delay time) distribution o?shower particles at large distance (>100 m) from the air shower core has been simulated.The characteristics of the distribution are expresse...By a Monte Carlo simulation, the arrival time (delay time) distribution o?shower particles at large distance (>100 m) from the air shower core has been simulated.The characteristics of the distribution are expressed by three parameters. An approximate formula for the distribution has also been derived. The distribution is found depending strongly on the distance from the core, but almost independent of the age, zenith angle, primary energy, primary compositions. An apparent difference is seen in some cases in the distribution from event to event when the number of particles is small. This is only due to statistical fluctuation. Therefore it is important to take into account the experimental conditions in the comparison of the present results with experimental data.展开更多
It has been found that unknown meteor showers could be efficiently discovered from the single station video meteor database of the International Meteor Organization(IMO) by assuming the geocentric velocity and adjusti...It has been found that unknown meteor showers could be efficiently discovered from the single station video meteor database of the International Meteor Organization(IMO) by assuming the geocentric velocity and adjusting it within the dynamically permitted range. The mean geocentric velocities of new meteor showers can be obtained,as well as the coordinates of the radiants. The activity period and maximum time can also be obtained if there are sufficient shower meteors. All single station video meteor observations between February 13 and 17(from 2000 to 2005) in IMO's database are processed with this method. As a result,two new meteor showers,one near RA=245.10°,Dec=41.82° in Hercules and the other near RA=233.03°,Dec=17.04° in Serpenids,are discovered. Some dynamical characteristics of the new meteor showers are also determined. Considering the random nature on the selection of period in this work,it is expected that there are some more potential new meteor showers in IMO's video database.展开更多
A chondrite shower occurred on April 15, 1986 in the vicinity of Dayianpo Village, Suizhou City, Hubei Province. It is the second large scale meteorite shower following the Jilin Meteorite Shower.
ARGO-YBJ, located at the Yangbajing Cosmic Ray Observatory （4300 m a.s.l., Tibet, China）, is a full coverage air shower array, with an energy threshold of -300 GeV for gamma-ray astronomy. Most of the recorded event...ARGO-YBJ, located at the Yangbajing Cosmic Ray Observatory （4300 m a.s.l., Tibet, China）, is a full coverage air shower array, with an energy threshold of -300 GeV for gamma-ray astronomy. Most of the recorded events are single front showers, satisfying the trigger requirement of at least 20 particles detected in a given time window. However, in -11.5% of the events, two randomly arriving showers may be recorded in the same time window, and the second one, generally smaller, does not need to satisfy the trigger condition. These events are called double shower front events. By using these small showers, well under the trigger threshold, the detector primary energy threshold can be lowered to a few tens of GeV. In this paper, the angular resolution that can be achieved with these events is evaluated by a full Monte Carlo simulation. The ARGO-YBJ sensitivity in detecting gamma-ray bursts （GRBs） by using double shower front events is also studied for various cutoff energies, time durations, and zenith angles of GRBs in ARGO＇s field of view.展开更多
Aiming at the observation of cosmic-ray chemical composition in the ＂knee＂ energy region, we have been developing a new type of air-shower core detector （YAC, Yangbajing Air shower Core detector array） to be set u...Aiming at the observation of cosmic-ray chemical composition in the ＂knee＂ energy region, we have been developing a new type of air-shower core detector （YAC, Yangbajing Air shower Core detector array） to be set up at Yangbajing （90.522° E, 30.102° N, 4300 m above sea level, atmospheric depth： 606 g/m2） in Tibet, China. YAC works together with the Tibet air-shower array （Tibet-Ⅲ） and an underground water Cherenkov muon detector array （MD） as a hybrid experiment. Each YAC detector unit consists of lead plates of 3.5 cm thickness and a scintillation counter which detects the burst size induced by high energy particles in the air-shower cores. The burst size can be measured from 1 MIP （Minimum Ionization Particle） to 106 MIPs. The first phase of this experiment, named ＂YAC- I ＂, consists of 16 YAC detectors each with a size of 40 cm×50 cm and distributed in a grid with an effective area of 10 m2. YAC- I is used to check hadronic interaction models. The second phase of the experiment, called ＂YAC-Ⅱ＂, consists of 124 YAC detectors with coverage of about 500 m2. The inner 100 detectors of 80 cm×50 cm each are deployed in a 10×10 matrix with a 1.9 m separation; the outer 24 detectors of 100 cm×50 cm each are distributed around these to reject non-core events whose shower cores are far from the YAC- Ⅱ array. YAC- Ⅱ is used to study the primary cosmic-ray composition, in particular, to obtain the energy spectra of protons, helium and iron nuclei between 5× 1013 eV and 1016 eV, covering the ＂knee＂ and also connected with direct observations at energies around 100 TeV. We present the design and performance of YAC- Ⅱ in this paper.展开更多
The separation and reconstructions of charged hadron and neutral hadron from their overlapped showers in an electromagnetic calorimeter is very important for the reconstructions of some particles with hadronic decays,...The separation and reconstructions of charged hadron and neutral hadron from their overlapped showers in an electromagnetic calorimeter is very important for the reconstructions of some particles with hadronic decays, for example the tau reconstruction in the searches for the Standard Model and supersymmetric Higgs bosons at the LHC. In this paper, a method combining the shower cluster in an electromagnetic calorimeter and the parametric formula for hadron showers, was developed to separate the overlapped showers between charged hadron and neutral hadron. Taking the hadronic decay containing one charged pion and one neutral pion in the final status of tau for example, satisfied results of the separation of the overlapped showers, the reconstructions of the energy and positions of the hadrons were obtained. An improved result for the tau reconstruction with this decay model can be also achieved after the application of the proposed method.展开更多
In the LHC experiment, the neutral pions produced during jet fragmentation are the background sources for all physics channels with high-energy photons in their final state. In this paper, the application of the three...In the LHC experiment, the neutral pions produced during jet fragmentation are the background sources for all physics channels with high-energy photons in their final state. In this paper, the application of the three-dimensional parametric formula for electromagnetic （EM） showers, which we developed in the Alpha Magnetic Spectrometer II experiment, is presented to distinguish the unconverted photons from the neutral pions. With the constructed electromagnetic calorimeter （ECAL） in a GEANT4 simulation, the parametric formulae were validated and the unconverted γ/π0 discrimination was performed with the Toolkit for Multivariate Data Analysis （TMVA） package in ROOT for different transverse energies ranging from 15 GeV to 75 GeV, which is the most sensitive region for light Higgs （with mass ～120 GeV） searches with the channel H → γγ. With this discrimination method and the selected transverse energy region, we can reject π0 with the effciency from ～ 40% （65–75 GeV） to ～ 90% （15–25 GeV） when keeping 90% γ effciency.展开更多
基金funding from the U.S.Environmental Protection Agency, Meghan Franco for assistance with XAD resin extractions, Shealy Environmental, Inc.for VOC analyses
文摘Lead contamination in the City of Flint, MI has been well documented over the past two years, with lead levels above the EPA Action Level until summer 2016. This resulted from an ill-fated decision to switch from Detroit water（Lake Huron） with corrosion control, to Flint River water without corrosion control. Although lead levels are now closer to normal,reports of skin rashes have sparked questions surrounding tap water in some Flint homes.This study investigated the presence of contaminants, including disinfection by-products（DBPs）, in the hot tap water used for showering in the homes of residents in Flint. Extensive quantitative analysis of 61 regulated and priority unregulated DBPs was conducted in Flint hot and cold tap water, along with the analysis of 50 volatile organic compounds and a nontarget comprehensive, broadscreen analysis, to identify a possible source for the reported skin rashes. For comparison, chlorinated hot and cold waters from three other cities were also sampled, including Detroit, which also uses Lake Huron as its source water.Results showed that hot water samples generally contained elevated levels of regulated and priority unregulated DBPs compared to cold water samples, but trihalomethanes were still within regulatory limits. Overall, hot shower water from Flint was similar to waters sampled from the three other cities and did not have unusually high levels of DBPs or other organic chemicals that could be responsible for the skin rashes observed by residents. It is possible that an inorganic chemical or microbial contaminant may be responsible.
文摘The Leonid meteor shower in November 1998 was observed widely by astronomers. The first peak, rich in bright meteors, appeared about 16 hours before the predicted maximum of the main shower. The main shower was also observed by both optical and radio methods during 19:00-21:00 UT on Nov. 17, and the radio peak was over 2500h-1. About 18 hours after the main shower, an abnormal phenomenon in the ionosphere was detected by two separate ionosphere observing stations. And the very high abnormal phenomenon maintained over one hour. The phenomenon showed that the ionosphere was injected with a large amount of small dust particles that could not be observed in optical and radio. The Observational results show that the Leonid meteor shower in 1998 had three peaks.
文摘Human exposure to radon inside different parts of the house has become a great concern. In this study, the distribution of radon and its decay inside the shower will be numerically investigated. In fact, the radon concentration in water is measured through the use of AlphaGUARD. They are used as an input for CFD simulation. The numerical results proved that temperature and humidity have significant impacts on both radon content and distribution. Also, the equilibrium factor variations between radon and its progeny with the temperature and relative humidity were carefully looked at. The equivalent doses due to <sup>218</sup>Po and <sup>214</sup>Po were evaluated in different tissues of the respiratory tract of the members of the public from the inhalation of air inside the shower. The annual effective dose due to radon short lived decay from the inhalation of air inside the shower by the members of the public was also investigated.
文摘Technology always brings us surprise and change life everyday. What you said,when you do your wool suits domestic cleaning with warm water at about 40° C,at your bathroom?Crazy?Easy-care?Wow,it's all about MerinoFreshTM!
文摘Showers with large zenith angles are observed in emulsion chambers exposed at Mt.Kanbala.The intensity of high energy muons is given and the multicore showers with large zenith angles are found.It is indicated that a new phenomenon may exist in the high energy nuclear interactions of cosmic rays.
文摘Extensive Air Showers(EAS)induced by cosmic ray particles of very low energies,owing to the significantly steep cosmic ray energy spectrum,dominate the secondary particle flux measured by single detectors and small shower arrays.Such arrays connected in extended networks can be used to determine potentially interesting spatial correlations between showers,which may shed new light on the nature of ultra high-energy cosmic rays.The quantitative interpretation of showers recorded by small local arrays requires a methodology that differs from that used by ordinary large EAS arrays operating in the"knee"region and above.We present"small EAS generator,"a semi-analytical method for integrating cosmic ray spectra over energies of interest and summing over the mass spectra of primary nuclei in arbitrary detector configurations.Furthermore,we provide results on the EAS electron and muon fluxes and particle density spectra.
基金Supported by Knowledge Innovation Fund (U-526) of IHEP,China
文摘Gamma ray source detection above 30 TeV is an encouraging approach for finding galactic cosmic ray sources. All sky survey for gamma ray sources using wide field of view detector is essential for population accumulation for various types of sources above 100 GeV. In order to target those goals, a large air shower particle detector array of 1 km^2 （the LHAASO project） at 4300 m a.s.l, is proposed, By adding two MagicⅡ- type telescopes in the array as proposed, LHAASO will be enhanced in source morphologic investigation power. The proposed array will be utilized also for energy spectrum measurement for individual cosmic ray species above 30 TeV. By re-configuring the wide field of view telescopes into fluorescence light detector array, the aperture of the detector array can be enlarged to cover an energy region above 100 PeV where the second knee is located. Cosmic ray spectrum and composition will be measured in order to transfer an energy scale to ultra high energy cosmic ray experiments.
文摘This review focuses on high-energy cosmic rays in the PeV energy range and above. Of particular interest is the knee of the spectrum around 3 PeV and the transition from cosmic rays of Galactic origin to particles from extra-galactic sources. Our goal is to establish a baseline spectrum from 1014 to 10^20 eV by combining the results of many measurements at different energies. In combination with measurements of the nuclear composition of the primaries, the shape of the energy spectrum places constraints on the number and spectra of sources that may contribute to the observed spectrum.
文摘A shower cloud observed in Jiangxi,a hailstorm observed in Hebei and“75.8”torrential rain in Henan are simulated with our microphysical model in a one-dimensional framework.The model,using the radio- sonde data as input,gets its output which shows agreement in many aspects as compared with observations in each case.The glaciation of small cumulus cloud,low precipitation efficiency of hailstorm and the per- sistence of torrential rain are demonstrated.It is also shown that the Bergeron process has little influence, but the warm-rain process plays an important role in the formation of precipitation in cumulonimbus with a warm cloud base.
基金Supported by National Natural Science Foundation of China (10435070,10721140381,10099630)China Ministry of Science and Technology (2007CB16101)Chinese Academy of Sciences (KJCX2-N17,1730911111)
文摘In this paper, we studied the development of hadronic shower in an electromagnetic calorimeter of Alpha Magnetic Spectrometer Ⅱ. Two parametrized empirical formulae were proposed to describe the hadronic shower shape in calorimeter. Using 100 GeV proton beam incident on the center of the ECAL, detailed plots of lateral and longitudinal hadronic shower behavior were given and we found the formulae can describe the development of the hadronic shower with the test beam data. The possible application of the parametrized formulae including e±-π± discrimination and tau jet reconstruction was discussed.
文摘Here is the first report on the observation of meteor ablation trails with lidar in China.Four long-lived Na ablation trails were observed during the 18/19 Nov.2001 Leonid meteor shower with a sodium resonance lidar over Wuhan.The mean altitude of the 4 trails is 97.95 km,consistent with Leouid high entry velocity(-72km/s).The peak density averages about 3380±3633cm^-3,and the abundance is(2.33±1.49)×10^(8)cm^(-2),both of which are higher than those previously observed for sporadic meteor trails.The RMS width is 359 m and the meteor's age is 81 min,indicating that they are long duration meteor trails.These observation results are quite different from those of sporadic meteor trails,but comparable to the 1998 and 1999 Leonid report.Five night observations from 17 Nov.to 23 Nov.suggest that the 2001 Leouid meteor shower does not have a significant impact on the abundance of the background Na layer.
基金Supported in part by the National Natural Science Foundation of China(11775211 and 11535002)the Applied Basic Research Programs of Yunnan Provincial Science and Technology Department(2016FB008)the CAS Center for Excellence in Particle Physics(CCEPP)
文摘The precision study of W^-W^+H production with subsequent W^±→l^±vl^(-)and H→bb decays at the Large Hadron Collider(LHC)aids in the investigation of Higgs gauge couplings and the search for new physics beyond the standard model.In this study,we calculate the shower-matched next-to-leading order QCD and electroweak(EW)corrections from the qq annihilation and photon-induced channels to the W^-W^+H production at the 14 TeV LHC.We deal with the subsequent decays of Higgs and W^±bosons by adopting the MADSPIN method.Both the integrated cross section and some kinematic distributions of W^±,H,and their decay products are provided.We find that the QCD correction significantly enhances the leading-order differential cross section,while the EW correction from the qq annihilation channel obviously suppresses it,especially in the high energy phase-space region,due to the Sudakov effect.The qy-and yy-induced relative corrections are positive and insensitive to the transverse momenta of W^±,H,and their decay products.These photon-induced corrections compensate the negative qq-initiated EW correction,and become the dominant EW contribution as the increment of the pp colliding energy.The parton shower(PS)effects on kinematic distributions are not negligible.The relative PS correction to the b-jet transverse momentum distribution can exceed 100%in the high p_(T,b)region.Moreover,we investigate the scale and PDF uncertainties,and find that the theoretical error of the QCD+EW+qγ+γγ-corrected integrated cross section mainly originates from the renormalization scale dependence of the QCD correction.
文摘By a Monte Carlo simulation, the arrival time (delay time) distribution o?shower particles at large distance (>100 m) from the air shower core has been simulated.The characteristics of the distribution are expressed by three parameters. An approximate formula for the distribution has also been derived. The distribution is found depending strongly on the distance from the core, but almost independent of the age, zenith angle, primary energy, primary compositions. An apparent difference is seen in some cases in the distribution from event to event when the number of particles is small. This is only due to statistical fluctuation. Therefore it is important to take into account the experimental conditions in the comparison of the present results with experimental data.
基金the National Natural Science Foundation of China (Grant No. 10373004)
文摘It has been found that unknown meteor showers could be efficiently discovered from the single station video meteor database of the International Meteor Organization(IMO) by assuming the geocentric velocity and adjusting it within the dynamically permitted range. The mean geocentric velocities of new meteor showers can be obtained,as well as the coordinates of the radiants. The activity period and maximum time can also be obtained if there are sufficient shower meteors. All single station video meteor observations between February 13 and 17(from 2000 to 2005) in IMO's database are processed with this method. As a result,two new meteor showers,one near RA=245.10°,Dec=41.82° in Hercules and the other near RA=233.03°,Dec=17.04° in Serpenids,are discovered. Some dynamical characteristics of the new meteor showers are also determined. Considering the random nature on the selection of period in this work,it is expected that there are some more potential new meteor showers in IMO's video database.
文摘A chondrite shower occurred on April 15, 1986 in the vicinity of Dayianpo Village, Suizhou City, Hubei Province. It is the second large scale meteorite shower following the Jilin Meteorite Shower.
基金Supported by National Natural Science Foundation of China(11475141)Fundamental Research Funds for Central Universities(2682014CX091)
文摘ARGO-YBJ, located at the Yangbajing Cosmic Ray Observatory （4300 m a.s.l., Tibet, China）, is a full coverage air shower array, with an energy threshold of -300 GeV for gamma-ray astronomy. Most of the recorded events are single front showers, satisfying the trigger requirement of at least 20 particles detected in a given time window. However, in -11.5% of the events, two randomly arriving showers may be recorded in the same time window, and the second one, generally smaller, does not need to satisfy the trigger condition. These events are called double shower front events. By using these small showers, well under the trigger threshold, the detector primary energy threshold can be lowered to a few tens of GeV. In this paper, the angular resolution that can be achieved with these events is evaluated by a full Monte Carlo simulation. The ARGO-YBJ sensitivity in detecting gamma-ray bursts （GRBs） by using double shower front events is also studied for various cutoff energies, time durations, and zenith angles of GRBs in ARGO＇s field of view.
基金Supported by grants from the National Natural Science Foundation of China(11078002,11275212,11165013)the Chinese Academy of Sciences(H9291450S3,Y4293211S5)the Knowledge Innovation Fund of Institute of High Energy Physics(IHEP),China(H95451D0U2,H8515530U1)
文摘Aiming at the observation of cosmic-ray chemical composition in the ＂knee＂ energy region, we have been developing a new type of air-shower core detector （YAC, Yangbajing Air shower Core detector array） to be set up at Yangbajing （90.522° E, 30.102° N, 4300 m above sea level, atmospheric depth： 606 g/m2） in Tibet, China. YAC works together with the Tibet air-shower array （Tibet-Ⅲ） and an underground water Cherenkov muon detector array （MD） as a hybrid experiment. Each YAC detector unit consists of lead plates of 3.5 cm thickness and a scintillation counter which detects the burst size induced by high energy particles in the air-shower cores. The burst size can be measured from 1 MIP （Minimum Ionization Particle） to 106 MIPs. The first phase of this experiment, named ＂YAC- I ＂, consists of 16 YAC detectors each with a size of 40 cm×50 cm and distributed in a grid with an effective area of 10 m2. YAC- I is used to check hadronic interaction models. The second phase of the experiment, called ＂YAC-Ⅱ＂, consists of 124 YAC detectors with coverage of about 500 m2. The inner 100 detectors of 80 cm×50 cm each are deployed in a 10×10 matrix with a 1.9 m separation; the outer 24 detectors of 100 cm×50 cm each are distributed around these to reject non-core events whose shower cores are far from the YAC- Ⅱ array. YAC- Ⅱ is used to study the primary cosmic-ray composition, in particular, to obtain the energy spectra of protons, helium and iron nuclei between 5× 1013 eV and 1016 eV, covering the ＂knee＂ and also connected with direct observations at energies around 100 TeV. We present the design and performance of YAC- Ⅱ in this paper.
基金Supported by National Natural Science Foundation of China(10721140381,11061140514)China Ministry of Science and Technology(2007CB816100,2013CB838700)
文摘The separation and reconstructions of charged hadron and neutral hadron from their overlapped showers in an electromagnetic calorimeter is very important for the reconstructions of some particles with hadronic decays, for example the tau reconstruction in the searches for the Standard Model and supersymmetric Higgs bosons at the LHC. In this paper, a method combining the shower cluster in an electromagnetic calorimeter and the parametric formula for hadron showers, was developed to separate the overlapped showers between charged hadron and neutral hadron. Taking the hadronic decay containing one charged pion and one neutral pion in the final status of tau for example, satisfied results of the separation of the overlapped showers, the reconstructions of the energy and positions of the hadrons were obtained. An improved result for the tau reconstruction with this decay model can be also achieved after the application of the proposed method.
基金Supported by National Natural Science Foundation of China (10435070, 10721140381, 10099630)China Ministry of Science and Technology (2007CB16101)Chinese Academy of Sciences (KJCX2-N17, 1730911111)
文摘In the LHC experiment, the neutral pions produced during jet fragmentation are the background sources for all physics channels with high-energy photons in their final state. In this paper, the application of the three-dimensional parametric formula for electromagnetic （EM） showers, which we developed in the Alpha Magnetic Spectrometer II experiment, is presented to distinguish the unconverted photons from the neutral pions. With the constructed electromagnetic calorimeter （ECAL） in a GEANT4 simulation, the parametric formulae were validated and the unconverted γ/π0 discrimination was performed with the Toolkit for Multivariate Data Analysis （TMVA） package in ROOT for different transverse energies ranging from 15 GeV to 75 GeV, which is the most sensitive region for light Higgs （with mass ～120 GeV） searches with the channel H → γγ. With this discrimination method and the selected transverse energy region, we can reject π0 with the effciency from ～ 40% （65–75 GeV） to ～ 90% （15–25 GeV） when keeping 90% γ effciency.
