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1.
《Physics letters. [Part B]》2002,530(1-4)
A search for the pseudoscalar meson ηb is performed in two-photon interactions at LEP 2 with an integrated luminosity of 699 pb−1 collected at e+e− centre-of-mass energies from 181 GeV to 209 GeV. One candidate event is found in the six-charged-particle final state and none in the four-charged-particle final state, in agreement with the total expected background of about one event. Upper limits of Γγγ(ηb)×BR(ηb→4 charged particles)<48 eV, Γγγ(ηb)×BR(ηb→6 charged particles)<132 eV are obtained at 95% confidence level, which correspond to upper limits of 9.0% and 25% on these branching ratios. 相似文献
2.
A. V. Anisovich D. V. Bugg N. Djaoshvili C. Hodd J. Kisiel L. Montanet A. V. Sarantsev B. S. Zou 《Nuclear Physics A》2001,690(4):364
Data on
at rest show two resonant processes: (a) f0(1370)η,f0(1370)→σσ and ρρ, (b) η(1440)σ, η(1440)→ηπ+π−. The branching ratio BR[f0(1370)→ρρ]/BR[f0(1370)→σσ]=0.98±0.25 in the mass range available here. Using data on
, the ratio Γ4π/Γ2π5 for f0(1370). The effects of the strongly s-dependent width of f0(1370) are discussed in some detail.The η(1440) is observed decaying to ησ and a0(980)π, with strong destructive interference between them. In its decay to a0(980)π, a narrow peak appears in the ηπ mass spectrum, but 30–50 MeV above that usually attributed to a0(980) and significantly above the KK threshold. This effect is explained naturally by a two-step process: η(1440)→K*(890)K followed by rescattering of the two kaons through a0(980) to ηπ above the KK threshold. 相似文献
3.
Let the map f:[−1,1]→[−1,1] have a.c.i.m. ρ (absolutely continuous f-invariant measure with respect to Lebesgue). Let δρ be the change of ρ corresponding to a perturbation X=δf○f−1 of f. Formally we have, for differentiable A,but this expression does not converge in general. For f real-analytic and Markovian in the sense of covering (−1,1) m times, and assuming an analytic expanding condition, we show thatis meromorphic in C, and has no pole at λ=1. We can thus formally write δρ(A)=Ψ(1). 相似文献
4.
John L. Cardy 《Nuclear Physics B》1984,240(4):514-532
Conformal invariance constrains the form of correlation functions near a free surface. In two dimensions, for a wide class of models, it completely determines the correlation functions at the critical point, and yields the exact values of the surface critical exponents. They are related to the bulk exponents in a non-trivial way. For the Q-state Potts model (0 Q 4) we find η<|; = 2/(3v − 1), and for the O(N) model (−2 N 2), η<|; = (2v − 1)/(4v − 1). 相似文献
5.
Takashi Imajo Yuki Kobayashi Yoshihiro Nakashima Keiichi Tanaka Takehiko Tanaka 《Journal of Molecular Spectroscopy》2005,230(2):139-148
Ultraviolet emission spectra of the TiF radical in the 407 nm region have been observed at a resolution of 0.04 cm−1 using a Fourier transform spectrometer. A new electronic assignment of 4Γ–X4Φ has been proposed. Rotational analysis has been obtained for the 0–0 and 1–1 vibrational bands of the 4Γ5/2–X4Φ3/2, 4Γ9/2–X4Φ7/2, and 4Γ11/2–X4Φ9/2 subbands and the 0–0 band of 4Γ7/2–X4Φ5/2. The lower state rotational and centrifugal distortion constants are consistent with the previous results [J. Mol. Spectrosc. 184 (1997) 186; J. Chem. Phys. 119 (2003) 9496], to the conformation that the lower state of the 407 nm band is the 4Φ ground electronic state. Rough estimates of the vibrational interval ΔG(1/2) and the spin–orbit coupling constant A in the 4Γ state were also obtained. 相似文献
6.
J. A. Koutcher R. H. Larkin J. R. Williams S. G. Kukolich 《Journal of Molecular Spectroscopy》1976,60(1-3)
The pure rotational spectrum of CH2F2 was recorded in the 20–100 cm−1 spectral range and analyzed to obtain rotation and centrifugal distortion constants. Analysis of the data yielded rotation constants: A = 1.6392173 ± 0.0000015, B = 0.3537342 ± 0.00000033, C = 0.3085387 ± 0.00000027, τaaaa = −(7.64 ± 0.46) × 10−5, τbbbb = −(2.076 ± 0.016) × 10−6, τcccc = −(9.29 ± 0.12) × 10−7, T1 = (4.89 ± 0.20) × 10−6, and T2 = −(1.281 ± 0.016) × 10−6cm−1. 相似文献
7.
《Physics letters. [Part B]》1996,380(3-4)
In a data sample of four million hadronic Z decays collected with the ALEPH detector at LEP, four Λb baryon candidates are exclusively reconstructed in the Λb → Λc+π− channel, with the Λc+ decaying into pK−π+,
, or Λπ+π+π−. The probability of the observed signal to be due to a background fluctuation is estimated to be 4.2 × 10−4. The mass of the Λb is measured to be 5614±21 (stat.) ± 4 (syst.) MeV/c2. 相似文献
8.
The electronic absorption, and emission spectra as well as fluorescence quantum yield of 3-(benzothiazol-2-yl)-7-hydroxycoumarin (BTHC) were measured in different solvents and are affected by solvent polarity (Δf). The deprotonation of BTHC by triethylamine is a reversible process. BTHC is relatively photostable, the quantum yield of photodecomposition (φc) was found to be 2×10−4 and 2.7×10−4 in EtOH and DMF, respectively. The fluorescence lifetimes of BTHC were measured in the absence and in the presence of molecular oxygen and were found to be 2.82 and 2.78 ns, respectively. BTHC acts as good laser dye upon pumping with nitrogen laser (λex=337.1 nm) in ethanol and gives laser emission with maxima at 508 and 522 nm. 相似文献
9.
《Physics letters. [Part B]》2000,490(3-4)
The process e+e−→W+W−γ is analysed using the data collected with the L3 detector at LEP at a centre-of-mass energy of 188.6 GeV, corresponding to an integrated luminosity of 176.8 pb−1. Based on a sample of 42 selected W+W− candidates containing an isolated hard photon, the W+W−γ cross section, defined within phase-space cuts, is measured to be: σWWγ=290±80±16 fb, consistent with the Standard Model expectation. Including the process
, limits are derived on anomalous contributions to the Standard Model quartic vertices W+W−γγ and W+W−Zγ at 95% CL: −0.043 GeV−2<a0/Λ2<0.043 GeV−2, −0.08 GeV−2<ac/Λ2<0.13 GeV−2, −0.41 GeV−2<an/Λ2<0.37 GeV−2. 相似文献
10.
R. J. Lovell S. J. Daunt M. Dakhil G. W. Halsey W. E. Blass 《Journal of Molecular Spectroscopy》1985,110(2)
The 2ν3(A1) band of 12CD3F near 5.06 μm has been recorded with a resolution of 20–24 × 10−3 cm−1. The value of the parameter (αB − αA) for this band was found to be very small and, therefore, the K structure of the R(J) and P(J) manifolds was unresolved for J < 15 and only partially resolved for larger J values. The band was analyzed using standard techniques and values for the following constants determined: ν0 = 1977.178(3) cm−1, B″ = 0.68216(9) cm−1, D″J = 1.10(30) × 10−6 cm−1, αB = (B″ − B′) = 3.086(7) × 10−3 cm−1, and βJ = (D″J − D′J) = −3.24(11) × 10−7 cm−1. A value of αA = (A″ − A′) = 2.90(5) × 10−3 cm−1 has been obtained through band contour simulations of the R(J) and P(J) multiplets. 相似文献
11.
The microwave spectrum of m-tolunitrile (3-methylbenzonitrile, m-C6H4CH3CN) has been investigated in the frequency range from 1 to 4 and 8 to 26.5 GHz. The spectra in the two lowest states of internal methyl rotation (m = 0, ±1) were recorded by means of pulsed molecular beam Fourier transform microwave (MB-FTMW) spectrometers. The interpretation of the spectra was based on an asymmetric frame–symmetric top Hamiltonian with inclusion of centrifugal distortion terms and first-order contributions from 14N nuclear quadrupole coupling. A least-squares analysis yielded the rotational constants A = 3295.9103(10) MHz, B = 1199.1188(2) MHz, C = 883.9223(1) MHz, all elements of the nuclear quadrupole coupling tensor χaa = −3.626(1) MHz, χbb = 1.684(1) MHz, χcc = 1.943(1) MHz, and χab = −1.870(3) MHz, as well as the threefold barrier to internal rotation, V3 = 14.2 cm−1, and the angle between the internal rotor axis and the principal moment of inertia a axis, θ = 42.66°, using fixed values for the sixfold barrier term V6 (−11 cm−1) and the moment of inertia of the methyl top Iα (3.16 u Å2). 相似文献
12.
Motivated by recent experimental data, we study solar neutrino oscillations in the range δm2/E ε [10−10, 10−7] eV2/MeV. In this range vacuum oscillations become increasingly affected by (solar and terrestrial) matter effects for increasing δm2, smoothly reaching the MSW regime. A numerical study of matter effects in such “quasi-vacuum” regime is performed. The results are applied to the analysis of the recent solar neutrino phenomenology. 相似文献
13.
A microscopic theory of π-meson double charge exchange (DCE) on light nuclei has been suggested and developed on the supposition that the corresponding elementary process proceeds by quasi-α-particle formation within the nucleus. Light nuclei consisting of both α-particles and α-particles and clusters of other kinds are considered. To describe the bound state of the quasi-α- particle and the continuum spectrum state of four identical nucleons, the four-body hyperspherical basis has been applied, while to obtain the wave functions of the centers of mass of the cluster relative motion we solve either the three-body Schrödinger equation (in the case of a three-body cluster configuration) or the two-body Schrödinger equation (in the case of a two-body cluster configuration). The reactions π± + 12C → π + 4p(4n) + 2α, π− + 7Li → π+ + 4n + 3H, π± + 6Li → π + 4p(4n) + n + p, π± + 6Li → π + 4p(4n) + d are investigated. It is shown that the effect of the final-state interaction between the four nucleons emitted by the nucleus in the process of π-meson DCE is rather important. The available experimental data on the 7Li nucleus can be explained quite satisfactorily on the supposition that this nucleus has a two-body cluster structure, and, hence, the π-meson DCE process occurs only on the α-particle.The differential and total cross sections of the reactions under investigation calculated as functions of the incident pion energy are essentially different for different nucleon-nucleon potentials. Experimental study of DCE on α-particle nuclei is shown to be a timely problem. 相似文献
14.
In this work we study the flavor changing neutral current (FCNC) decays of the top quark, t→cγ and t→cg, in the framework of the unparticle physics. The Standard Model predictions for the branching ratios of these decays are about 5×10−14, and 1×10−12, respectively. The parameter space of λ, Λ, and d is obtained by taking into account the SM predictions and the results of the simulation performed by the ATLAS Collaboration for the branching ratios of t→cγ and t→cg decays. 相似文献
15.
Y. Kabbadj M. Herman G. Di Lonardo L. Fusina J. W. C. Johns 《Journal of Molecular Spectroscopy》1991,150(2)
Absorption spectra of C2H2 have been recorded between 50 and 1450 cm−1, with a resolution always better than 0.005 cm−1, using two different Fourier transform spectrometers. Analysis of the data provided two sets of results. First, the bending levels with Σt Vt(t = 4, 5) ≤ 2 were characterized by a coherent set of 34 parameters derived from the simultaneous analysis of 15 bands, performed using a matrix Hamiltonian. The following main parameters were obtained (in cm−1): ω40 = 608.985196(14), ω50 = 729.157564(10); B0 = 1.17664632(18), α4 = −1.353535(86) × 10−3, α5 = −2.232075(40) × 10−3; q40 = 5.24858(12) × 10−3, and q50 = 4.66044(12) × 10−3, with the errors (1σ) on the last quoted digit. Second, a more complete set of bending levels with Σt Vt ≤ 4, some of which have never previously been reported, and also including V2 = 1 have been fitted to 80 parameters. This simultaneous fit involved 43 bands and used the same full Hamiltonian matrix. Some perturbations which affect the higher excited levels are discussed. 相似文献
16.
Kazuhiko Ishikawa Hitomi Yamano Ki-ichiro Kagawa Katsuhiko Asada Koichi Iwata Masahiro Ueda 《Optics and Lasers in Engineering》2004,41(1):19-29
An optical method for directly measuring the thickness of a thin transparent film has been proposed by means of multi-wave laser interference at many incident angles, and confirmed experimentally by means of equipment made on an experimental basis. Two methods are available: one can be used when an index of refraction of the film, a wavelength λ, and two successive angles of incidence at which the sinusoidal light intensity has minimum values, are known (Method I), and another can be used without an index of film refraction when three successive angles of incidence and a wavelength are known (Method II). The smallest measurable thickness is 1.43λ for Method I, and 2.5λ for Method II. The largest measurable thickness is about 100λ for both methods. The measurement error by means of numerical calculation is Δh/h−1.01×10−2, and that obtained experimentally with an angular resolution of incident light of 0.3° is Δh/h7×10−2 for Method I. The refractive index can also be measured by means of Method II. 相似文献
17.
I.L. Drichko A.M. Diakonov V.I. Kozub I.Yu. Smirnov Yu.M. Galperin A.I. Yakimov A.I. Nikiforov 《Physica E: Low-dimensional Systems and Nanostructures》2005,26(1-4):450
Dense (n=4×1011 cm-2) arrays of Ge quantum dots in a Si host were studied using attenuation of surface acoustic waves (SAWs) propagating along the surface of a piezoelectric crystal located near the sample. The SAW magneto-attenuation coefficient, ΔΓ=Γ(ω,H)-Γ(ω,0), and change of velocity of SAW, ΔV/V=(V(H)-V(0))/V(0), were measured in the temperature interval T=1.5–4.2 K as a function of magnetic field H up to 6 T for the waves in the frequency range f=30–300 MHz. Based on the dependences of ΔΓ on H, T and ω, as well as on its sign, we believe that the AC conduction mechanism is a combination of diffusion at the mobility edge with hopping between localized states at the Fermi level. The measured magnetic field dependence of the SAW attenuation is discussed based on existing theoretical concepts. 相似文献
18.
Guojian Wang Zhoubin Lin Lizhen Zhang Yisheng Huang Guofu Wang 《Journal of luminescence》2009,129(11):1398-1400
This paper reports the spectral properties and energy levels of Cr3+:Sc2(MoO4)3 crystal. The crystal field strength Dq, Racah parameter B and C were calculated to be 1408 cm−1, 608 cm−1 and 3054 cm−1, respectively. The absorption cross sections σα of 4A2→4T1 and 4A2→4T2 transitions were 3.74×10−19 cm2 at 499 nm and 3.21×10−19 cm2 at 710 nm, respectively. The emission cross section σe was 375×10−20 cm2 at 880 nm. Cr3+:Sc2(MoO4)3 crystal has a broad emission band with a broad FWHM of 176 nm (2179 cm−1). Therefore, Cr3+:Sc2(MoO4)3 crystal may be regarded as a potential tunable laser gain medium. 相似文献
19.
Analysis of autoionizing Rydberg states in the vacuum ultraviolet absorption spectrum of HBr and DBr
The photographic absorption spectrum of HBr and DBr above the first ionization limit (800–1000 Å) has been analyzed. No analyzable rotational structure was observed, indicating that the autoionization rate is faster than the rotational period. Two Rydberg series converging to the second ionization limit (2Σ+) have been identified, one with n* = 2.75, 3.74, ,14.7, and the other with n* = 2.35, 3.38. The symmetries cannot be determined conclusively, but the most probable assignment for the first series is 4pσ 4pπ4nsσ (1Σ+) N = 6, 7, , 18, and for the second, 4pσ 4pπ·npσ and/or npπ[1Σ+, 1Π] N = 5, 6. Assuming that the intensity maxima assigned are band origins of vibronic states, a new ionization limit can be determined for HBr+(2Σ+): T0 = 123 373 ± 20 cm−1. 相似文献
20.
As a sequel to our previous paper on extending the Fast Multipole Method (FMM) for charges inside a dielectric sphere [J. Comput. Phys. 223 (2007) 846–864], this paper further extends the FMM to the electrostatic calculation for charges inside a dielectric sphere immersed in an ionic solvent, a scenery with more relevance in biological applications. The key findings include two fourth-order multiple discrete image approximations in terms of u = λa to the reaction field induced by the ionic solvent, provided that u = λa < 1 where λ is the inverse Debye screening length of the ionic solvent and a is the radius of the dielectric sphere. A 10−4 relative accuracy in the reaction field of a source charge within the sphere can be achieved with only 3–4 point image charges. Together with the image charges, the FMM can be used to speed up the calculation of electrostatic interactions of charges in a dielectric sphere immersed in an ionic solvent. 相似文献