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First Measurements of eta_c Decaying into K^+K^-2(pi^+pi^-) and 3(pi^+pi^-)

First Measurements of eta_c Decaying into K^+K^-2(pi^+pi^-) and 3(pi^+pi^-)
First Measurements of eta_c Decaying into K^+K^-2(pi^+pi^-) and 3(pi^+pi^-)

First Measurements of ηc Decaying into K +K ? 2(π +π ? ) and 3(π +π ?)
M. Ablikim1 , J. Z. Bai1 , Y. Ban11 , J. G. Bian1 , X. Cai1 , J. F. Chang1 , H. F. Chen17 , H. S. Chen1 , H. X. Chen1 , J. C. Chen1 , Jin Chen1 , Jun Chen7 , M. L. Chen1 , Y. B. Chen1 , S. P. Chi2 , Y. P. Chu1 , X. Z. Cui1 , H. L. Dai1 , Y. S. Dai19 , Z. Y. Deng1 , L. Y. Dong1a , Q. F. Dong15 , S. X. Du1 , Z. Z. Du1 , J. Fang1, S. S. Fang2, C. D. Fu1 , H. Y. Fu1 , C. S. Gao1 , Y. N. Gao15 , M. Y. Gong1 , W. X. Gong1, S. D. Gu1 , Y. N. Guo1 , Y. Q. Guo1 , Z. J. Guo16 , F. A. Harris16 , K. L. He1 , M. He12 , X. He1 , Y. K. Heng1 , H. M. Hu1 , T. Hu1 , G. S. Huang1b , X. P. Huang1 , X. T. Huang12 , X. B. Ji1 , C. H. Jiang1 , X. S. Jiang1 , D. P. Jin1 , S. Jin1 , Y. Jin1 , Yi Jin1 , Y. F. Lai1 , F. Li1 , G. Li2 , H. H. Li1 , J. Li1 , J. C. Li1 , Q. J. Li1 , R. Y. Li1 , S. M. Li1 , W. D. Li1 , W. G. Li1 , X. L. Li8 , X. Q. Li10 , Y. L. Li4 , Y. F. Liang14 , H. B. Liao6 , C. X. Liu1 , F. Liu6 , Fang Liu17 , H. H. Liu1 , H. M. Liu1 , J. Liu11 , J. B. Liu1 , J. P. Liu18 , R. G. Liu1 , Z. A. Liu1 , Z. X. Liu1 , F. Lu1 , G. R. Lu5 , H. J. Lu17 , J. G. Lu1 , C. L. Luo9 , L. X. Luo4 , X. L. Luo1 , F. C. Ma8 , H. L. Ma1 , J. M. Ma1 , L. L. Ma1 , Q. M. Ma1 , X. B. Ma5 , X. Y. Ma1 , Z. P. Mao1 , X. H. Mo1 , J. Nie1 , Z. D. Nie1 , S. L. Olsen16 , H. P. Peng17 , N. D. Qi1 , C. D. Qian13 , H. Qin9 , J. F. Qiu1 , Z. Y. Ren1 , G. Rong1 , L. Y. Shan1 , L. Shang1 , D. L. Shen1 , X. Y. Shen1 , H. Y. Sheng1 , F. Shi1 , X. Shi11c , H. S. Sun1 , J. F. Sun1 , S. S. Sun1 , Y. Z. Sun1 , Z. J. Sun1 , X. Tang1 , N. Tao17 , Y. R. Tian15 , G. L. Tong1 , G. S. Varner16 , D. Y. Wang1 , J. Z. Wang1 , K. Wang17 , L. Wang1 , L. S. Wang1 , M. Wang1 , P. Wang1 , P. L. Wang1 , S. Z. Wang1 , W. F. Wang1d Y. F. Wang1 , Z. Wang1 , Z. Y. Wang1 , Zhe Wang1 , Zheng Wang2 , C. L. Wei1 , D. H. Wei1 , N. Wu1 , Y. M. Wu1 , X. M. Xia1 , X. X. Xie1 , B. Xin8b , G. F. Xu1 , H. Xu1 , S. T. Xue1 , M. L. Yan17 , F. Yang10 , H. X. Yang1 , J. Yang17 , Y. X. Yang3 , M. Ye1 , M. H. Ye2 , Y. X. Ye17 , L. H. Yi7 , Z. Y. Yi1 , C. S. Yu1 , G. W. Yu1 , C. Z. Yuan1 , J. M. Yuan1 , Y. Yuan1 , S. L. Zang1 , Y. Zeng7 , Yu Zeng1 , B. X. Zhang1 , B. Y. Zhang1 , C. C. Zhang1 , D. H. Zhang1 , H. Y. Zhang1 , J. Zhang1 , J. W. Zhang1 , J. Y. Zhang1 , Q. J. Zhang1 , S. Q. Zhang1 , X. M. Zhang1 , X. Y. Zhang12 , Y. Y. Zhang1 , Yiyun Zhang14 , Z. P. Zhang17 , Z. Q. Zhang5 , D. X. Zhao1 , J. B. Zhao1 , J. W. Zhao1 , M. G. Zhao10 , P. P. Zhao1 , W. R. Zhao1 , X. J. Zhao1 , Y. B. Zhao1, Z. G. Zhao1e , H. Q. Zheng11 , J. P. Zheng1 , L. S. Zheng1 , Z. P. Zheng1 , X. C. Zhong1 , B. Q. Zhou1 , G. M. Zhou1 , L. Zhou1 , N. F. Zhou1 , K. J. Zhu1 , Q. M. Zhu1 , Y. C. Zhu1 , Y. S. Zhu1 , Yingchun Zhu1f , Z. A. Zhu1 , B. A. Zhuang1 , X. A. Zhuang1 , B. S. Zou1 (BES Collaboration)
1
arXiv:hep-ex/0505093v1 28 May 2005
Institute of High Energy Physics, Beijing 100049, People’s Republic of

China China Center for Advanced Science and Technology, Beijing 100080, People’s Republic of China 3 Guangxi Normal University, Guilin 541004, People’s Republic of China 4 Guangxi University, Nanning 530004, People’s Republic of China 5 Henan Normal University, Xinxiang 453002, People’s Republic of China 6 Huazhong Normal University, Wuhan 430079, People’s Republic of China 7 Hunan University, Changsha 410082, People’s Republic of China 8 Liaoning University, Shenyang 110036, People’s Republic of China 9 Nanjing Normal University, Nanjing 210097, People’s Republic of China 10 Nankai University, Tianjin 300071, People’s Republic of China 11 Peking University, Beijing 100871, People’s Republic of China 12 Shandong University, Jinan 250100, People’s Republic of China 13 Shanghai Jiaotong University, Shanghai 200030, People’s Republic of China 14 Sichuan University, Chengdu 610064, People’s Republic of China 15 Tsinghua University, Beijing 100084, People’s Republic of China 16 University of Hawaii, Honolulu, Hawaii 96822, USA 17 University of Science and Technology of China, Hefei 230026, People’s Republic of China 18 Wuhan University, Wuhan 430072, People’s Republic of China 19 Zhejiang University, Hangzhou 310028, People’s Republic of China
2 b
e
Current address: Iowa State University, Ames, Iowa 50011-3160, USA. Current address: Purdue University, West Lafayette, Indiana 47907, USA. c Current address: Cornell University, Ithaca, New York 14853, USA. d Current address: Laboratoire de l’Acc′l′ratear Lin′aire, F-91898 Orsay, ee e France. Current address: University of Michigan, Ann Arbor, Michigan 48109, USA. f Current address: DESY, D-22607, Hamburg, Germany.
a
Abstract The decays of ηc to K + K ? 2(π + π ? ) and 3(π + π ? ) are observed for the ?rst time using a sample of 5.8× 107 J/ψ events collected by the BESII detector. The product branching fractions are determined to be B(J/ψ → γηc )·B(ηc → K + K ? π + π ? π + π ? ) ?0 = (1.21 ± 0.32 ± 0.23) × 10?4 , B(J/ψ → γηc ) · B(ηc → K ?0 K π + π ? ) = (1.29 ± 0.43 ± 0.32) × 10?4 , and B(J/ψ → γηc ) · B(ηc → π + π ? π + π ? π + π ? ) = (2.59 ± 0.32 ± 0.48) × 10?4 . The upper limit for ηc → φπ + π ? π + π ? is also obtained as B(J/ψ → γηc ) · B(ηc → φπ + π ? π + π ? ) < 6.03 × 10?5 at the 90% con?dence level. PACS: 13.25.Gv, 14.40.Gx, 13.40.Hq
2

1
Introduction
The ηc , a 1 S0 state in the charmonium family, was found in the inclusive photon spectra from J/ψ and ψ(2S) [1] decays, as well as in hadronic decays [2]. A number of decay modes of ηc were then measured [3]. More recent measurements of hadronic decays of ηc are listed in Ref. [4]. According to Ref. [5], the ηc is expected to have numerous decay modes into hadronic ?nal states. Although a number of decay modes of ηc have been measured by di?erent experimental collaborations, the number of measured ηc decay channels are few. This means that many decay modes of ηc are unknown. The 58 million, (57.70 ± 2.72) × 106 [6], J/ψ events taken at BESII provide a chance to observe new decays. In this analysis, ηc decaying into K + K ? π + π ? π + π ? and π + π ? π + π ? π + π ? are studied using J/ψ → γηc . The upgraded Beijing Spectrometer detector, located at the Beijing ElectronPositron Collider (BEPC), is a large solid-angle magnetic spectrometer which is described in detail in Ref. [7]. The momentum of the charged particle is determined by a 40-layer cylindrical main drift chamber (MDC) which has a √ momentum resolution of σp /p=1.78% 1 + p2 (p in GeV/c). Particle identi?cation is accomplished by speci?c ionization (dE/dx) measurements in the drift chamber and time-of-?ight (TOF) information in a barrel-like array of 48 scintillation counters. The dE/dx resolution is σdE/dx = 8.0%; the TOF resolution for Bhabha events is σT OF = 180 ps. Radially outside of the time-of-?ight counters is a 12-radiation-length barrel shower counter (BSC) comprised of gas tubes interleaved with lead sheets. The BSC measures the energy and di√ rection of photons with resolutions of σE /E ? 21% E (E in GeV), σφ = 7.9 mrad, and σz = 2.3 cm. The iron ?ux return of the magnet is instrumentd with three double layers of counters that are used to identify muons. A GEANT3 based Monte Carlo package (SIMBES) with detailed consideration of the detector performance is used to obtain the detection e?ciency. The consistency between data and Monte Carlo has been carefully checked in many high purity physics channels, and the agreement is reasonable [8].
2
Analysis of J/ψ → γηc, ηc → K + K ?π + π ?π + π ?
These events are observed in the topology γK + K ? π + π ? π ? π ? . Events with six good charged tracks and at least one isolated photon are selected. The selection criteria for good charged tracks and isolated photons are described in detail in Ref. [9]. Each charged track must be well ?tted to a helix, originating from the interaction region of Rxy < 2 cm and |z| < 20 cm, and have a polar angle θ in the range | cos θ| < 0.8. Here Rxy is the distance from the beam axis, and z 3

is along the beam axis. Isolated photons are those that have energy deposited in the BSC greater than 60 MeV, the angle between the direction at the ?rst layer of the BSC and the developing direction of the cluster less than 30? , and the angle between photons and any charged tracks larger than 5? . Two of the charged tracks should be identi?ed as kaons by combined TOF and dE/dx information. A four-constraint (4C) kinematic ?t is performed under the hypothesis of J/ψ → γK + K ? π + π ? π + π ? , and the χ2 + K ? π+ π? π+ π? is required to be less γK than 10. To reject background from J/ψ → γγK + K ? π + π ? π + π ? , χ2 + K ? π+ π? π+ π? γK is required to be less than χ2 + K ? π+ π? π+ π? . Background events from J/ψ → γγK K + K ? π + π ? π + π ? are eliminated by requiring χ2 + K ? π+ π? π+ π? < χ2 + K ? π+ π? π+ π? γK K and Pmiss > 55 MeV/c, where Pmiss is the missing momentum of charged tracks.
40
EVENTS/(6MeV/c2)
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0 2.75
2.8
2.85
2.9
2.95
2
3
3.05
m(K K π π π π ) (GeV/c )
+ - + - + -
Fig. 1. The distribution of mK + K ? π+ π? π+ π? for selected events. The histogram with error bars is from data, the shaded part is the background estimated from J/ψ → anything Monte Carlo simulation, and the curve represents the ?tting results described in the text.
After the above selection, the K + K ? π + π ? π + π ? invariant mass, mK + K ? π+ π? π+ π? , distribution is shown in Fig. 1. A peak at the ηc mass is observed. The shaded histogram is the background estimated from 58 million J/ψ → anything Monte-Carlo events generated with the Lund-charm generator [10]; no prominent signal in the ηc mass region is seen. Also, 100,000 events for the two possible background channels J/ψ → K + K ? 2(π + π ? ) and J/ψ → γ3(π + π ? ) are simulated. After ?nal selection, no events remain in the ηc mass region. A Breit-Wigner folded with a Gaussian to take into account the mass resolution of 12.3 MeV/c2 at the ηc and a polynomial background are used in the ?t. The ?t gives 100 ± 26 ηc events with a statistical signi?cance of 4.0 σ, where the mass and width of ηc are ?xed to the PDG values [11]. 4

Using this sample, we search for the decay mode ηc → K ?0 K π + π ? . To ?0 select K ?0 K π + π ? events, we require that the invariant masses of K + π ? and ?0 K ? π + must statisfy |mKπ ? 0.896| < 0.05 GeV/c2 . After the K ?0 and K selection, the K + K ? 2(π + π ? ) invariant mass is shown in Fig. 2. A small peak at the ηc mass is observed. The background events corresponding to the shaded ?0 histogram in Fig. 2 are estimated from K ?0 and K sidebands (0.1 GeV/c2 < |mK + π? ? 0.896| < 0.15 GeV// c2 and 0.1 GeV/c2 < |mK ? π+ ? 0.896| < 0.15 GeV// c2 ), and there is no evident ηc signal. 45 ± 15 events are obtained by ?tting the mass spectrum with a Breit-Wigner folded with a Gaussian to account for the ηc mass resolution plus a second polynomial background. The corresponding mass and width of the ηc are ?xed to PDG values [11]. Since the signi?cance of the peak is only 3σ, we also give the upper limit for ?0 ηc → K ?0 K π + π ? . With the Bayes method, the ?t of this distribution yields 65 events at the 90% con?dence level.
?0
20 17.5
EVENTS/6MeV
15
12.5 10 7.5 5 2.5 0 2.75 2.8 2.85 2.9 2.95 3
2
3.05
m(K K π π π π ) (GeV/c )
+ - + - + -
Fig. 2. The distribution of mK + K ? π+ π? π+ π? for ηc → K ?0 K π + π ? candidate events. The histogram with error bars is for data, the shaded part is the back?0 ground estimated from K ?0 (K ) sidebands, and the curve is the ?tting results described in the text.
?0
The J/ψ → γK + K ? π + π ? π + π ? sample can also be used to search for ηc → φπ + π ? π + π ? . For selecting a φ signal, the K + K ? mass, mK + K ? , is required to be in the region |mK + K ? ? 1.02| < 0.015 GeV/c2 . After this selection, no clear ηc signal is found in the distribution of mK + K ? π+ π? π+ π? , as shown in Fig. 3. Using Bayes method, a ?t to ηc → K + K ? π + π ? π + π ? with a Breit-Wigner folded with a Gaussian and a polynomial background gives 13.5 ηc events at the 90% con?dence level. From Monte-carlo simulation, in which the angle (θ) between the direction of the e+ and ηc in the laboratory frame is generated according to a 1+cos2 θ distribution and uniform phase-space is used for ηc decaying into K + K ? 2(π + π ? ) 5

EVENTS/(5MeV/c2)
6
4
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0
2.8
2.9
+ - + - + 2
3
m(K K π π π π ) (GeV/c )
Fig. 3. The distribution of mK + K ? π+ π? π+ π? for ηc → φπ + π ? π + π ? candidate events.
and φ2(π + π ? ), the detection e?ciencies of J/ψ → γηc (ηc → K + K ? π + π ? π + π ? ), ?0 J/ψ → γηc (ηc → K ?0 K π + π ? ), and J/ψ → γηc (ηc → φπ + π ? π + π ? ) are determined as (1.43 ± 0.04)%, (1.36 ± 0.04)%, and (1.01 ± 0.02)%, respectively. Therefore, the branching fractions obtained are B(J/ψ → γηc ) · B(ηc → K + K ? π + π ? π + π ? ) = (1.21 ± 0.32) × 10?4 , B(J/ψ → γηc ) · B(ηc → K ?0 K π + π ? ) = (1.29 ± 0.43) × 10?4 ?0 B(J/ψ → γηc ) · B(ηc → K ?0 K π + π ? ) < 1.86 × 10?4 , and B(J/ψ → γηc ) · B(ηc → φπ + π ? π + π ? ) < 4.72 × 10?5 . 3 Analysis of J/ψ → γηc ,ηc → π + π ? π + π ? π + π ?
?0
These events are observed in the topology J/ψ → γπ + π ? π + π ? π + π ? . Events with six good charged tracks and at least one isolated photon are selected. No particle identi?cation is required. To suppress background, a 4C kinematic ?t is performed under the hypothesis γπ + π ? π + π ? π + π ? , and the χ2 is required to be less than 10. To reject background from J/ψ → 3(π + π ? ) and J/ψ → 3(π + π ? )π 0 , we require χ2 + π? π+ π? π+ π? to be less than χ2 + π? π+ π? π+ π? and γπ π χ2 + π? π+ π? π+ π? π0 . π Figure 4 shows the π + π ? π + π ? π + π ? invariant mass spectrum after the above selection. A clear ηc peak is observed. The shaded histogram in Fig. 4 cor6

200
EVENTS/(6MeV/c2)
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0 2.75
2.8
2.85
2.9
2.95
2
3
3.05
m(π π π π π π ) (GeV/c )
+ - + - + -
Fig. 4. The distribution of mπ+ π? π+ π? π+ π? for selected events. The histogram with error bars is data, the shaded part is the background estimated from Monte Carlo simulation, and the curve is the ?tting result described in the text.
responds to background estimated from 58 million J/ψ → anything MonteCarlo events generated using the Lund-Charm generator [10], where no ηc signal is evident. A ?t of the mπ+ π? π+ π? π+ π? distribution, which is shown as the solid curve in Fig. 4, using a Breit-Wigner convoluted with a Gaussian to represent the signal and a polynomial for the background, yields 427 ± 64 ηc events with a statistical signi?cance of 6.9σ. In the ?t, the mass and width of ηc are again ?xed to PDG values [11]. The detection e?ciency for J/ψ → γηc , ηc → π + π ? π + π ? π + π ? is determined to be (3.21 ± 0.04)%, by Monte-Carlo simulation with the distribution of θ, the angle between the directions of e+ and ηc in the laboratory frame, being generated with a 1 + cos2 θ and with ηc decaying into 3(π + π ? ) being generated with a uniform phase-space distribution. The branching ratio is then found to be B(J/ψ → γηc ) · B(ηc → π + π ? π + π ? π + π ? ) = (2.59 ± 0.32) × 10?4 . 4 Systematic errors
The systematic errors mainly come from the following sources: (1) MDC tracking e?ciency ˉ This has been measured with clean channels like J/ψ → ΛΛ and ψ(2S) → + ? + ? π π J/ψ, J/ψ → μ μ . It is found that the Monte Carlo simulation agrees with data within 1-2% for each charged track. Therefore, 12% is conservatively 7

taken as the systematic error in the tracking e?ciencies for the 6-prong ?nal states analyzed here. (2) Photon detection e?ciency This has been studied using di?erent methods with J/ψ → ρ0 π 0 events [12]. The di?erence between data and Monte Carlo simulation is less than 2% for each photon, and 2% is taken as the systematic error for the photon e?ciency in this analysis. (3) Particle identi?cation (PID) This has been studied with J/ψ → K + K ? π 0 . The e?ciency of the PID from data is consistent with that from Monte Carlo simulation. The average di?erence is less than 2%. For J/ψ → γK + K ? π + π ? π + π ? decay, 4% is taken as the systematic error from PID. (4) Kinematic Fit The kinematic ?t is useful to reduce background. Using the same method for estimating the systematic error as in Ref. [9], the decay mode J/ψ → 3(π + π ? )π 0 is also analyzed. The e?ciency di?erence of the kinematic ?t for data and Monte Carlo is 7.7%. Since the decay of J/ψ → 3(π + π ? )π 0 is similar to the two channels analyzed in this paper, 7.7% is also taken here as the systematic error of the kinematic ?t. (5) ηc parameters Although the ηc signal is clear, the number of events is not large enough to determine the Breit-Wigner parameters and the background shape well. The variation of the ?t solution due to changes of the ηc mass and width corresponding to the uncertainties in the PDG, as well as changes in the ?tting mass region used, is taken as a systematic error and listed in Table 1. (6) Background 0 0 For ηc → K + K ? π + π ? π + π ? , the biggest background comes from ηc → KS KS K + K ? . 0 When the invariant mass of π + π ? is required to be within the KS mass region (|mπ+ π? ? 0.497| < 0.02 GeV/c2 ), ?ve events remain in the ηc mass 0 0 region. If all of them are regarded as signal from ηc → KS KS K + K ? , the background from this decay mode is about 5.1%, and this is taken as the systematic error associated with background for this channel. No events remain ?0 for ηc → K ?0 K π + π ? and the upper limit is 2.3 events at 90% con?dence 0 0 level. Then the uncertainty caused by ηc → KS KS π + π ? is 5.1%. For the ηc → 3(π + π ? ), Monte Carlo simulation is used to estimate the back0 0 0 ground from ηc → KS KS π + π ? . Using the branching fraction for ηc → K 0 K π + π ? , obtained from B(ηc → K + K ? π + π ? ) [11], Monte Carlo simulation indicates that 33 background events contribute to the ηc signal. Compared to the 416 signal events from ?tting the mass spectrum, the background fraction is 7.9% 8

which is taken as the background systematic error for this channel. (7) Number of J/ψ events The number of J/ψ events is (57.70 ± 2.72) × 106 , determined from J/ψ inclusive four-prong events. The uncertainty is taken as a systematic error in the branching ratio measurement. Table 1 lists the systematic errors from all sources, and the total systematic error is the sum of them added in quadrature.
Table 1 Systematic error sources and contributions (%) Sources MDC tracking Paticle ID Photon e?ciency Kinematic ?t ηc parameters MC statistics Background uncertainty B(φ → K + K ? ) Number of J/ψ events Total 4.7 19.4 4.7 25.0 K + K ? 2(π + π ? ) 12 4 2 7.7 9.9 2.6 5.1 K ?0 K π + π ? 12 4 2 7.7 18.6 2.9 5.1 1.4 4.7 21.7 4.7 18.6
?0
φ2(π + π ? ) 12 4 2 7.7 14.7 2.9
3(π + π ? ) 12 negligible 2 7.7 7.4 1.1 7.9
5
Results
The decays of ηc → K + K ? π + π ? π + π ? and ηc → π + π ? π + π ? π + π ? are observed for the ?rst time, and their decay branching ratios are measured. The upper ?0 limits of ηc → φπ + π ? π + π ? and ηc → K ?0 K π + π ? are also set at the 90% con?dence level. To conservatively estimate the upper limit, the systematic error is included by lowering the e?ciency by one standard deviation. Table 2 shows the branching ratio results including systematic errors. Using the branching fraction of J/ψ → γηc as B(J/ψ → γηc ) = (1.3 ± 0.4)% from the PDG [11], we obtain: B(ηc → K + K ? π + π ? π + π ? ) = (0.93 ± 0.25 ± 0.34) × 10?2 B(ηc → K ?0 K π + π ? ) = (0.99 ± 0.33 ± 0.39) × 10?2 B(ηc → K ?0 K π + π ? ) < 2.36 × 10?2 9
?0 ?0

Table 2 Numbers used in the calculations of branching fractions and upper limits. Decay Modes J/ψ → γηc , ηc → K + K ? 2(π + π ? ) J/ψ → γηc , ηc → K ?0 K π + π ? J/ψ → γηc , ηc → K ?0 K π + π ? J/ψ → γηc , ηc → φ2(π + π ? ) J/ψ → γηc , ηc → 3(π + π ? )
?0 ?0
Nobs 100±26 45 ± 15 < 65 < 13.5 427±64
ε (%) 1.43±0.04 1.36 ± 0.04 1.36 ± 0.04 1.01 ± 0.02 3.21±0.04
Branching Fraction (1.21 ± 0.32 ± 0.23) × 10?4 (1.29 ± 0.43 ± 0.32) × 10?4 < 2.46 × 10?4 (90% C.L.) < 6.03 × 10?5 (90% C.L.) (2.59 ± 0.32 ± 0.48) × 10?4
B(ηc → φπ + π ? π + π ? ) < 5.81 × 10?3 (90% C.L.) B(ηc → π + π ? π + π ? π + π ? ) = (1.99 ± 0.25 ± 0.72) × 10?2 The BES collaboration thanks the sta? of BEPC and the computing center for their hard e?orts. This work is supported in part by the National Natural Science Foundation of China under contracts Nos. 19991480, 10225524, 10225525, the Chinese Academy of Sciences under contract No. KJ 95T-03, the 100 Talents Program of CAS under Contract Nos. U-11, U-24, U-25, and the Knowledge Innovation Project of CAS under Contract Nos. U-602, U-34 (IHEP); and by the National Natural Science Foundation of China under Contract No.10175060 (USTC), and No. 10225522 (Tsinghua University); and by the U. S. Department of Energy under Contract N0. DE-FG02-04ER41291.
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(完整版)高中英语必修一第一单元课文原文和翻译

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外研版英语必修三课文原文

Great European Cities PARIS Paris is the capital and largest city of France, situated on River Seine. It is one of the most beautiful cities in the world and is visited by more than eight million tourists every year. The most popular place for tourists is the Eiffel Tower, the famous symbol of Paris. One of the world’s largest art galleries, the Louvre, is also located in Paris. The city is also located in Paris. The city is also famous for its restaurants, cafes and theatres. About two-thirds of France’s artists and writers live in Paris. BARCELONA Barcelona is the second largest city of Spain and is situated on the northeast coast, about five hundred kilometres east of the Spanish capital, Madrid. One of Barcelona’s most famous landmarks is the Church of Sagrada Familia, which was designed by an architect called Antonio Gaudi. Gaudi worked on the project from 1882 until his death in 1926. The church hasn’t been finished yet! FLORENCE Florence is an Italian city which became famous because of the Renaissance, a great artistic movement which began in the 1300s and lasted for three hundred ears. During the Renaissance, some of the greatest painters of all time lived and worked in Florence. Many of Florence’s most beautiful paintings and sculptures were produced by great artists such as Leonardo da Vinci and Michelangelo. Florence is visited each year by about a million tourists who come to see the art galleries, churches and museums. The Uffizi Palace is the most famous art gallery in the city. ATHENS Athens, the capital of Greece, is known as the birthplace of western civilization. Two thousand four hundred years ago, it was the world’s most powerful city. Buildings such as the Parthenon on the Acropolis Hill were built during this period. Greece’s best writers lived in ancient Athens. Their work has influenced other writers ever since. The Human Development Report In the year 2000, 147 world leaders agreed to work together to reduce poverty by 2015 or earlier. From this agreement came the Human Development Report. One of the most important sections of this report is the Human Development Index. This examines the achievements of 175 countries. The Index measures a country’s achievements in three ways: life expectancy (how long people usually live), education and income. The index has some surprises. Norway is at the top of the list, while the US is at number 7. The other top five countries are: Iceland(2), Sweden(3), Australia(4), the Netherlands(5). The UK is in the thirteenth position, while China is in the middle of the list. The bottom ten countries are all African countries, with Sierra Leone(in West Africa) at the bottom of the list. The report describes eight Development Goals. The most important goals are to: Reduce poverty and hunger; Make sure that all children have education up to the age of 11; Fight AIDS and other diseases; Improve the environment of poor people, e.g. make sure they have safe drinking water; Encourage developed countries to give more help to other countries. The 2003 Human Development Report gives examples of successful development. For example, in nine years, China increased life expectancy by 13 years. In the last ten years in China, 150 million people moved out of poverty. However, the challenges are still great. Every day 799 million people in developing countries are hungry. Over half of these are in South Asia or Africa. Although more than 80% of children in developing countries go to primary school, about 115 million children are not being educated. More than 1 billion people in developing countries do not drink safe water. However, in other regions of the world, e.g. Eastern Europe, water is now mostly safe to drink.

挖土安全操作规程(新编版)

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挖土安全操作规程(新编版)导语:建立和健全我们的现代企业制度,是指引我们生产劳动的方向。而大力发展我们生产力的前提,是我们必须对我们企业和我们自己的生命安全负责。可用于实体印刷或电子存档(使用前请详细阅读条款)。 1挖土前根据安全技术交底了解地下管线、人防及其他构筑物情况和具体位置。地下构筑物外露时,必须进行加固保护。作业过程中应避开管线和构筑物。在现场电力、通信电缆2m范围内和现场燃气、热力、给排水等管道1m范围内挖土时,必须在主管单位人员监护下采取人工开挖。 2开挖槽、坑、沟深度超过1.5m,必须根据土质和深度情况按安全技术交底放坡或加可靠支撑,遇边坡不稳、有坍塌危险征兆时,必须立即撤离现场。并及时报告施工负责人,采取安全可靠排险措施后,方可继续挖土。 3槽、坑、沟必须设置人员上下坡道或安全梯。严禁攀登固壁支撑上下,或直接从沟;坑边壁上挖洞攀登爬上或跳下。间歇时,不得在槽、坑坡脚下休息。 4挖土过程中遇有古墓、地下管道、电缆或其他不能辨认的异物和液体、气体时,应立即停止作业,并报告施工负责人,待查明处理后,

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4挖土过程中遇有古墓、地下管道、电缆或其他不能辨认的异物和液体、气体时,应立即停止作业,并报告施工负责人,待查明处理后,再继续挖土。 5槽、坑、沟边1m以内不得堆土、堆料、停置机具。堆土高度不得超过1.5m。槽、坑、沟与建筑物、构筑物的距离不得小于1.5m。开挖深度超过2m时,必须在周边设两道牢固护身栏杆,并立挂密目安全网。 6人工开挖土方,两人横向间距不得小于2m,纵向间距不得小于3m。严禁掏洞挖土,搜底挖槽。 7钢钎破冻土、坚硬土时,扶钎人应站在打锤人侧面用长把夹具扶钎,打锤范围内不得有其他人停留。锤顶应平整,锤头应安装牢固。钎子应直且不得有飞刺。打锤人不得戴手套。 8从槽、坑、沟中吊运送土至地面时,绳索、滑轮、钩子、箩筐等垂直运输设备、工具应完好牢固。起吊、垂直运送时,下方不得站人。 9配合机械挖土清理槽底作业时,严禁进入铲斗回转半径范围。

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人工挖土安全操作规程示 范文本 In The Actual Work Production Management, In Order To Ensure The Smooth Progress Of The Process, And Consider The Relationship Between Each Link, The Specific Requirements Of Each Link To Achieve Risk Control And Planning 某某管理中心 XX年XX月

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