首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 78 毫秒
1.
SELEX合作组发现的DsJ(2632)引起了很多的讨论, 同时也带来了激烈的争论. 它的自旋宇称还没有最后确定, 如果它真的存在, 它的夸克结构可能是奇特的. 以前有的文献假定DsJ(2632)是1的径向激发态, 我们假定它可能是夸克结构为qq,JP为2+的基态或者0+DsJ(2317)的第一径向激发态, 用Bethe-Salpeter方程重新计算了它的衰变宽度. 计算结果表明, 理论值和实验数据还是存在尖锐的矛盾.  相似文献   

2.
在重夸克极限下,用QCD因子化方法分析Ds→φπ的衰变.讨论了硬旁观者散射等非因子化贡献,并给出了数值结果,理论预言的分支比与实验相符.最后,结合D0→Kπ的测量值,采用纯惟象的方法估计Ds→φπ的分支比.  相似文献   

3.
在正负电子对撞能量4.03GeV处,BES实验在BEPC对撞机上完成了Ds介子纯轻子衰变,半轻子衰变和φπ+分支比的绝对测量.文章详细描述了用于π与K识别的联合置信度方法,Ds单标记和双标记技术,以及计算Ds衰变分支比的最大似然函数.对所得物理结果做了讨论和评述.对未来Ds物理改进测量做了展望  相似文献   

4.
利用北京谱仪在e+e对撞质心能量4.03GeV所取得的约22.3pb-1的数据,用先标记μ,后标记Ds的方法,共找到2个Ds→μv,3个Ds→τv→μvvv衰变候选事例,给出了Ds的纯轻子衰变的绝对分支比为:Br(Ds→μv)+0.72+0.70-0.44),Br(Ds→τv)=(14+11-8)%,并给出不依赖于模型假设的Ds衰变常数为:fDs=(355+96+28-90-28)MeV.  相似文献   

5.
熊兆华 《中国物理 C》2006,30(4):284-288
在似矢量夸克模型中, 具有一个为SU(2)单态的下夸克D以及树图b→sZ*相互作用zsb. 在此框架下,(1) 通过考察描述B→Xsγ的Wilson系数随重正化标度从mD到弱标度的跑动, 研究了D夸克对此衰变的影响.(2) 使用最近对B→Xsl+l的测量,获得了对zsb相当严格的限制. 发现前后不对称的零点值可以与标致模型的预言有大的偏离, 并对zsb十分敏感, 可以用来探测新物理.  相似文献   

6.
通过分析J/ψ→π+π-π0来研究ρω干涉.利用描述J/ψ衰变的一般的唯象模型对PDG-2002关于J/ψ衰变到PP和PV的实验数据做了拟合(P表示赝标介子,V表示矢量介子) ,得到ρ0→π+π-π0反常大的分支比~10-3—10-2.理论的分析结果也与这一反常大的分支比相符合.同时,得到了合理的ηη′混合角和组分夸克质量比:θ=-19.68°±1.49°,mu/ms≈0.6 .  相似文献   

7.
李营  吕才典 《中国物理 C》2003,27(12):1062-1066
在标准模型中,稀有衰变道B+→D+sK*0只有通过纯湮没图才可以发生.这样这个衰变道的分支比很小.利用基于kT?因子化的微扰方法给出分支比的预测,发现它在10-8的量级上.这个衰变道估计在将来的LHC上得到测量,对检验标准模型以及探寻新物理有着重要的意义.  相似文献   

8.
C(γ,η)X反应与N(1535)在核内的性质   总被引:15,自引:0,他引:15  
在N*(1535)共振模型下,研究了γ在原子核上产生η的反应,通过N衰变的实验数据以及γp→ηp反应确定了模型参数,结果表明,MN*=1550MeV才较好地符合γp→ηp的实验,对12C上的η介子光生的总截面计算发现,N*(1535)在核内的宽度由于多体修正而增大,N*-核的相互作用具有排斥性质.  相似文献   

9.
在标准模型中, 三体稀有衰变B0(Bs)→γνν只有通过箱图和企鹅图才可以发生.这个过程对于确定B介子的衰变常数及其波函数有着较重要的物理意义,由于这些衰变道的分支比较小, 因此也是探测新物理理论的比较好的场所.利用B介子强衰变确定的波函数, 得到 B0(Bs)→γνν的分支比的数量级是10-9(10-8), 这些结果可以在未来的实验上得到检验.  相似文献   

10.
We study the perspectives of resonant and nonresonant charmed-meson production in ˉp + A reactions within the Multiple Scattering Monte Carlo (MSMC) approach. We calculate the production of the resonances Ψ(3770),Ψ(4040) and Ψ(4160) on various nuclei, their propagation and decay to D,ˉD, D *,ˉD*, D s,ˉDs in the medium and vacuum, respectively. The modifications of the open charm vector mesons in the nuclear medium are found to be rather moderate or even small such that dilepton spectroscopy will require an invariant mass resolution of a few MeV. Furthermore, the elastic and inelastic interactions of the open charm mesons in the medium are taken into account, which can be related to (u, d )-, s- or c-quark exchange with nucleons. It is found that by studying the D/ˉD ratio for low momenta in the laboratory ( ? 2 - 2.2 GeV/c) as a function of the target mass A stringent constraints on the c-quark exchange cross-section can be obtained. On the other hand, the ratios D - s/D + s as well as D/D - s and D/D + s at low momenta as a function of A will permit to fix independently the strength of the s-quark exchange reaction in D - s N scattering. Received: 1 March 2002 / Accepted: 21 March 2002  相似文献   

11.
12.
A procedure is presented for the calculation of the double vibrational collision-induced absorption CO(2) (nu(3) = 1) + N(2) (nu(1) = 1) <-- CO(2) (nu(3) = 0) + N(2) (nu(1) = 0) on the basis of quantum lineshapes computed using an isotropic potential and dipole-induced dipole functions. The linestrengths and energies of the vibration-rotation transitions are treated explicitly for N(2), utilizing the HITRAN database for CO(2). The theoretical absorption profile is compared to recent experimental results. By narrowing the width of the individual lines contributing to the overall absorption profile relative to their values determined for N(2)-N(2) collision-induced absorption, excellent agreement between theory and experiment is obtained. Copyright 2000 Academic Press.  相似文献   

13.
An analysis of the nu(17)-nu(4) difference bands near 800 cm(-1) of two isotopic species, (10)B(2)H(6) and (11)B(2)H(6), of diborane has been carried out using infrared spectra recorded with a resolution of ca. 0.003 cm(-1). In addition, the nu(17) band of (10)B(2)H(6) has been recorded and assigned. Since this band in (11)B(2)H(6) had already been studied (R. L. Sams, T. A. Blake, S. W. Sharpe, J.-M. Flaud, and W. J. Lafferty, J. Mol. Spectrosc. 191, 331-342 (1998)), it was possible to derive precise energy levels and Hamiltonian constants for the 4(1) vibrational states of both isotopic species. Copyright 2000 Academic Press.  相似文献   

14.
Using pulsed perturbation-facilitated optical-optical double resonance (PFOODR) spectroscopy, the 2(3)Delta(g) state of (7)Li(2) (electronic configuration (varsigma(g)2s) (4ddelta(g)), effective principal quantum number n* = 4.101) has been observed and assigned. Molecular constants and a RKR potential energy curve were obtained. The major molecular constants are Copyright 2000 Academic Press.  相似文献   

15.
We have observed the rotational levels in the v = 2, 3, 5, 6, 7, and 8 vibrational manifolds of the 2(1)Delta(g) state of (7)Li(2) via the A(1)Sigma(+)(u) intermediate levels by DeltaLambda = 2 transitions. This violation of the DeltaLambda = 0, +/-1 selection rule is due to the interaction with the G(1)Pi(g) state. Band-by-band deperturbations of the G(1)Pi(g) approximately 2(1)Delta(g) (v(Pi), v(Delta)) = (11, 2), (12, 3), (15, 5), (16, 6), (18, 7), and (19, 8) bands have been performed. Deperturbed molecular constants and rotational-electronic interaction parameters are reported here. Copyright 2000 Academic Press.  相似文献   

16.
Absolute line intensities of (12)C(16)O(2) are experimentally measured for the first time for the (00(0)3)(I) <-- (10(0)0)(II) band at 5687.17 cm(-1) and the (00(0)3)(I) <-- (10(0)0)(I) band at 5584.39 cm(-1). The spectra were obtained using a Bomem DA8 Fourier transform spectrometer and a 25-m base-path White cell at NASA-Ames Research Center. The rotationless bandstrengths at a temperature of 296 K and the Herman-Wallis parameters are S(0)(vib) = 6.68(30) x 10(-25) cm(-1)/(molecule/cm(2)); A(1) = 1.4(9) x 10(-4), and A(2) = -1.1(5) x 10(-5) for the (00(0)3)(I) <-- (10(0)0)(II) band and S(0)(vib) = 6.07(22) x 10(-25) cm(-1)/(molecule/cm(2)); A(1) = 5.2(1.5) x 10(-4) and A(2) = -4.0(7) x 10(-5) for the (00(0)3)(I) <-- (10(0)0)(I) band.  相似文献   

17.
18.
王君  齐建起 《光散射学报》2009,21(3):226-231
本文主要研究了CO2的三种同位素分子16O12C16O , 16O12C17O ,16O13C17O 70 K~6000 K的总内配分函数 (TIPS)。在总内配分函数的计算中, 转动配分函数的计算采用了McDowell的解析式法, 振动配分函数则采用了简谐振动近似(HOA)获得。最后通过将两配分函数乘积近似计算得出TIPS, 并将其70~3000 K的数据和HITRAN04数据进行了比较, 发现所得结果和数据库符合的较好, 且其误差可以近似看成一条直线。并通过对误差的拟合修订了高温区(3000~6000 K)的计算数据, 给出了在高温下的较为准确的TIPS值。  相似文献   

19.
Using 0.002 cm(-1) resolution Fourier transform absorption spectra of an (17)O enriched ozone sample, an extensive analysis of the v(1)+v(3) bands of the (16)O(17)O(16)O and (16)O(16)O(17)O isotopomers of ozone has been performed for the first time. The experimental rotational levels of the (101) vibrational states were satisfactorily reproduced using a Hamiltonian matrix that takes into account the observed rovibrational resonances. More precisely, for (16)O(17)O(16)O, as for the other C(2v)-type ozone isotopomers, it was necessary to account for the Coriolis type resonances linking the (101) rotational levels with the levels of the (200) and (002) vibrational states and the Darling-Dennison interaction coupling the levels of (200) with those of (002). For the C(s)-type isotopomer, namely (16)O(16)O(17)O, as for (16)O(16)O(18)O and (16)O(18)O(18)O, it proved necessary to also account for an additional DeltaK(a)&equals+/-2 resonance involving the rotational levels from (101) and (002) (J.-M. Flaud and R. Bacis, Spectrochimica Acta Part A 54, 3-16 (1998)). Using a Hamiltonian matrix which takes these resonances explicitly into account, precise vibrational energies and rotational and coupling constants were deduced, leading to the following band centers: v(0)(v(1)+v(3))=2078.3496 cm(-1) for (16)O(17)O(16)O and v(0)(v(1)+v(3))=2098.8631 cm(-1) for (16)O(16)O(17)O. Copyright 2001 Academic Press.  相似文献   

20.
Measurements of magnetic and transport properties were performed on needle-shaped single crystals of Ce_(12)Fe_(57.5)As_(41)and La_(12)Fe_(57.5)As_(41).The availability of a complete set of data enabled a side-by-side comparison between these two rare earth compounds.Both compounds exhibited multiple magnetic orders within 2-300 K and metamagnetic transitions at various fields.Ferromagnetic transitions with Curie temperatures of 100 and 125 K were found for Ce_(12)Fe_(57.5)As_(41)and La_(12)Fe_(57.5)As_(41),respectively,followed by antiferromagnetic type spin reorientations near Curie temperatures.The magnetic properties underwent complex evolution in the magnetic field for both compounds.An antiferromagnetic phase transition at about 60 K and 0.2 T was observed merely for Ce_(12)Fe_(57.5)As_(41).The field-induced magnetic phase transition occurred from antiferromagnetic to ferromagnetic structure.A strong magnetocrystalline anisotropy was evident from magnetization measurements of Ce_(12)Fe_(57.5)As_(41).A temperature-field phase diagram was present for these two rare earth systems.In addition,a logarithmic temperature dependence of electrical resistivity was observed in the two compounds within a large temperature range of 150-300 K,which is rarely found in 3D-based compounds.It may be related to Kondo scattering described by independent localized Fe 3d moments interacting with conduction electrons.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号