共查询到20条相似文献,搜索用时 15 毫秒
1.
BES Collaboration 《中国物理C(英文版)》2002,26(11):1093-1102
We report the results of a search for the semileptonic decays D+→e+ν,D+→K-π+e+ν,D0→K-e+ν and D0→K-μ+ν using the BES detector at the BEPC e+e- Collider. Using a data sample of 22.3pb-1 collected at the center of mass energy s=4.03GeV, we select 2472±87D 0 tag DX and 7628±149D 0 tag DX singly tagged D events, where the X could be γ, π 0 and/or π±. Based on the method of "combined D+and D0 single and double tags", we determine that 2471±218 D+X and 7629±251 D0 X are contained in the recoil side of the singly tagged neutral and charged D mesons, respectively. No events for the 4 semileptonic decay modes are observed in the recoil side of the tagged D mesons. The 90% confidence level upper limits of B(D+→e+ν)<1.38%,B(D+→K-π+e+ν)<2.01%,B(D0→K-e+ν)<0.53% and B(D0→K-μ+ν)<0.53% are determined from the search for the semileptonic decays of D+ and D0. 相似文献
2.
THE COULOMB DISINTEGRATION CROSS-SECTION AND DECAY RATE OF THE SPIN (0-3/2) ELECTROMAGNETIC BOUND SYSTEM
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In this paper, the coulomb disintegration cross-section and decay rate of the atom (π+Ω-) are calculated by using perturbation expansion of the quantized composite field theory and relativistic B-S wave function for spin (0-3/2) electromagnetic bound system. The disintegration cross-section of the high energy atom (π+Ω-) in screened coulomb field of nuclei is about σ=Z4/3×2.9×10-18cm2, and the calculation result of the decay rate is w[(π+Ω-)→π+Λ0K-]/w[Ω-→Λ0K-]=1+O(α). 相似文献
3.
Under conditions near the center of the Sun, it shows that 7Be atoms are completely ionized between R=0 to R=0.1217R⊙. The newly calculated 7Be and 8B solar neutrino fluxes are about 4.00×109cm-2·s-1 and 6.18×106cm-2·s-1, while the corresponding predicted values of the standard solar model are 4.80×109cm-2·s-1 and 5.15×106cm-2·s-1,respectively. It will further increase the discrepancy between the observed and the predicted neutrino fluxes in Super Kamiokande neutrino experiment. 相似文献
4.
BES Collaborator 《中国物理C(英文版)》1998,22(11):961-968
We have analysed the e+e- collision data collected with Beijing Spectrometer at the center-of-mass energy 4.03 GeV and selected e+e-→τ±τ+→e±X+v's events, X± required as μ±、π± and ρ±. From fitting electron energy spectrum in τ→ev's decay, the measurement value of Michel parameter is given as ρτ→e=0.705, this result is in good agreement with the prediction of standrd Model. 相似文献
5.
THE MEASUREMENT OF THE EXCITATION FUNCTIONS OF ISOTOPES OF Fr AND At,PRODUCED IN THE BOMBARDMENT OF 12C ON 209Bi
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Excitation functions for Fr and At isotopes produced in 12C on 209Bi had been measured in the energy range 60—72 MeV. It was quite obvious that 213Fr and 214Fr were formed by the reactions 209Bi (12C,4n) 217Ac and 209Bi (12C,3n) 218Ac following the a decay of the Ac isotopes respectively, and 214mFr was produced probably by compound nucleus evaporation of neutrons and an α particle, i.e. (12C, α 3n). 211At was mainly contributed by a multi-nucleon transfer reaction (e.g. 8Be transfer). The experimental data for neutron evaporation reaction were fitted by the Jackson formula. 相似文献
6.
Entrance Channel Dependence of the Correlation Function of IMFs in 36Ar+112,124Sn at 35MeV/u
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HU Rong-Jiang XIAO Zhi-Gang WU He-Yu DUAN Li-Min WANG Hong-Wei YUAN Xiao-Hua JIN Gen-Ming ZHU Yong-Tai LI Zu-Yu WANG Su-Fang XU Hu-Shan ZHANG Bao-Guo WEI Zhi-Yong FENG Zhao-Qing FU Fen 《中国物理C(英文版)》2007,31(4):350-356
The reduced velocity correlation functions of the Intermediate Mass Fragments (IMFs) were measured in the reactions of 36Ar+112,124Sn at 35MeV/u. The anti-correlation at small reduced velocities is more pronounced in 36Ar+124Sn system than that in 36Ar+112Sn system. The difference of the correlation functions between the two reactions is mainly contributed by the particle pairs with high momenta. A three-body Coulomb repulsive trajectory code (MENEKA) is employed to calculate the emission time scale of IMFs for the both systems. The time scale is 150fm/c in the 36Ar+112Sn system and 120fm/c in the 36Ar+124Sn system, respectively. A calculation based on an Isospin dependence Quantum Molecular Dynamics code (IQMD) reveals that the emission time spectrum of IMFs is shifted slightly leftwards in 36Ar+124Sn compared with that in the 36Ar+112Sn system, indicating a shorter emission time scale. Correspondingly, the central density of the hot nuclei decreases faster in 36Ar+124Sn than in 36Ar+112Sn. 相似文献
7.
The Cross Section Measurement for the Reactions of 48,46Ti(n,p) 48,46Sc 50Ti(n,α) 47Ca and 58Ni (n,2n) 57Ni 58Ni(n,p)58m+gCo
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The cross sections for the 50Ti(n,α)47Ca,46Ti(n,p)46Sc、48Ti(n,p)48Sc and 58Ni(n,2n)57Ni 58Ni(n,p)58m+gCo reactions have been measured by using the activation method relative to the cross sections of the 27Al(n,α)24Na reaction in the neutron energy range of 13.50—14.81MeV.The neutron energies were determined by the cross section ratios of the 90Zr(n,2N) 89m+gZr and 93Nb (n,2n) 92mNb reactions.The results obtained are compared with the published and to be published data of several authors. 相似文献
8.
We calculate the short range part of π+-π-,K+-K-,K+-π- and K--π+ potentials by using both the conventional quark-antiquark annihilation mechanism and the hybrid medium state model.The result of the scattering length for π+-π- channel favors the hybrid medium state model. 相似文献
9.
庞丹阳叶沿林 郑涛李智焕 李湘庆葛愉成 华辉吴翠娥 楼建玲卢飞 范凤英A. Ozawa Y. Yamaguchi R. Kanungo D. Fang I.Tanihata 《中国物理快报》2007,24(10):2785-2788
The inclusive differential cross sections of the ^7 Li nucleus in a reaction induced by ^6He on a ^9Be target are measured at an incident energy of 25 MeV/nucleon. Finite-range distorted-wave Born approximation calculations suggest that these ^7 Li particles are formed in a direct single-proton pickup reaction ^9Be(^6He,^7 Li)^8Li. The experimental data can be well reproduced by taking into account of the contributions of both the ground states and the first excited states of ^7Li and ^8Li. 相似文献
10.
Cross Section Measurements for (n,2n),(n,p)and (n,α) Reactions on Strontium Isotopes at the Neutron Energy About 14MeV
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Cross-sections for 84Sr(n, 2n)83Sr, 86Sr(n, 2n)85mSr,86Sr(n, 2n)85Sr,88Sr(n, 2n)87mSr,84Sr(n, p)84Rb,86Sr(n, p)86Rb, 88Sr(n, p)88Rb and 88Sr(n,α)85mKr reactions were measured at neutron energies from 13.5 to 14.6MeV using activation technique and γ-ray spectrometry. The neutron flux was determined using the monitor reaction 93Nb(n, 2n)92mNb and the neutron energies were measured by the method of cross section ratios for $^{90}$Zr(n, 2n)$^{89m+g}$Zr to $^{93}$Nb(n, 2n)$^{92m}$Nb reactions. The results of present work were compared with data published previously. 相似文献
11.
Luminescence Spectra of YGG:RE^3+, Bi^3+ (RE = Eu and Tb) and Energy Transfer from Bi^3+ to RE^3+
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We investigate the luminescence properties of Bi^3+ and RE^3+ (RE = Tb or Eu) in a Y3Ga5O12 (YGG) host system. The additional doping of Bi^3+ can enhance the luminescence of Th^3+ or Eu^3+ in this host. Energy transfer from Bi^3+ to Tb^3+ and Eu^3+ is observed and the mechanism of energy transfer is investigated. Mechanism of energy transfer can be explained as electric multipole interaction since the Bi^3+ emission band and Tb^3+ or Eu^3+ excitation band overlaps and the Bi^3+ emission intensity decreases while the intensity of Tb^3+ or Eu^3+ increases with the increase of Tb^3+ or Eu^3+ concentration. Therefore, Bi^3+ ion is a kind of efficient sensitizer to the Tb^3+ and Eu^3+ activators in the Y3Ga5O12 host. 相似文献
12.
Using Glauber's multiple scattering theory, and using coherent fluctuation nuclearmodel, the double charge exchange (DEC) reaction cross sections for πon 16O and 18Ohave been calculated. The calculated values of the ratio of σ(18O(π+,π-)18Ne)g.s. toσ(16O(π+,π-)16Ne)g.s. fit the experimental data quite well. Just as predicted by ourcalculation, the angular distribution of 18O(π+,π-)18Neg.s. in a recent experiment,exhibits an evident dip around 23°. 相似文献
13.
WANG Yong-Chang YUAN Jun-Qian YANG Jing-Kang KONG Xiang-Zhong REN Zhong-Liang WANG Hua-Min 《中国物理C(英文版)》1992,16(8):731-735
Measurement of (n,2n) reaction cross sections for some nuclides,whose residues have long half-lives,is described.The activation method relative to the 93Nb(n,2n)92mNb reaction cross section was used.The cross sections of the 151Eu(n,2n)150mEu、153Eu(n,2n)152Eu、159Tb(n,2n)158Tb and 109Ag(n,2n)108mAg reactions in the neutron energy range of 13.50—14.80MeV were measured.The neutron energies in this experiment were determined by means of the method of cross section ratios for 90Zr(n,2n)89m+gZr and 93Nb(n,2n)92mNb reactions.The results obtained were compared with other existing data. 相似文献
14.
在室温下测量了GdoBr:Eu的常压和高压荧光谱,光谱范围在13 000~21 500 cm-1之间,压力至12 GPa。由光谱数据得到了Eu3+晶场能级随压力的变化曲线。7F0~5能级随压力的变化规律比较复杂,而5D0~2各能均随压力的升高几乎线性地降低。在基态谱项7F的49个状态上进行了晶场拟合计算,所得常压下的5个非零晶场参数分别为:B02=-1 124.0 cm-1,B04=-969.6 cm-1,B44=827.9 cm-1,B06=889.6 cm-1,B46=377.0 cm-1。高压下的计算结果表明,B04、B06这两个晶场参数随压力的增加而增大,B46随压力的增加而减小,而B02、B44随压力的变化有些起伏。晶场强度在8 GPa以下随压力增加而减小,其后开始变强。 相似文献
15.
LIU Zu-Hua 《中国物理C(英文版)》2003,27(2):135-137
The experimental data of the 13C(d,p) 14C reaction are used to extract the asymptotic normalization coefficients of the overlap integral, the root-mean-square radii 2>1/2 and the probabilities D1 outside the range of the interaction radius RN for the last neutron of the 1- and 0- excited states in 14C. We obtain 2>1/2=4.57±0.30fm, 5.78±0.36fm and D 1=55.7%, 63.9% for these two states, respectively. These large values are the good sign that the 1- and 0- excited states in 14C are neutron halo states. 相似文献
16.
In this paper, using SU(6) symmetry theory four-baryon system is discussed and a method of analyzing experimental spectra is provided. Because of the gound states of ΛΛ4H, ΛΛ4He, Λ4He and 4He are in the same I. R. of SU(6), on can derives masses for ΛΛ4H, ΛΛ4He from the experimental data of Λ4H, Λ4He, and 4He. Calculation shows that these Jπ=0+ double Λ hypernuclei ΛΛ4H, ΛΛ4He are not likely bound states. 相似文献
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19.
The cross sections of reactions 58Ni(n,2n)57Ni,58Ni(n,p)58mCo,58Ni(n,p)58gCo and 58Ni(n,p)58m+gCo were measured based on 27Al(n,a) 24Na reaction by activation methods.Incident neutron energies were 14.10MeV and 14.62MeV.A comparison was made between present results and other published data.The cross sections for 58gCo nuclei formation are given for the first time. 相似文献
20.
Wang Zhenxia Wang Minmin Zhu Fuying Ji Guifang Luo Wenyun Li Xinnian Wang Chuanshan 《中国物理C(英文版)》1997,21(4):304-310
Measurements of the angular distributions and yields of atoms sputtered from Ag target by bombardment with FeCl+,56Fe+ and 35Cl+ are reported.Large enhancement occurs in the measured Ag atom yield for FeCl+ projectile in comparison with the sum of the sputtering yields for 56Fe+ and 35Cl+ bombardment at same impact velocities.The enhanecment can be explained by a model of the thermal spike-evaporation plus surface topography effect. 相似文献