共查询到20条相似文献,搜索用时 62 毫秒
1.
Martin Kretzschmar 《Zeitschrift für Physik A Hadrons and Nuclei》1969,223(5):397-414
Several simple models for theS-waves in isospinI=0 andI=2 pion-pion scattering are constructed. These models are based on unitarity, analyticity in the complexq-plane (q=c.o.m. momentum), approximate crossing symmetry, and the assumption that the forces acting in theS-waves are mainly due to exchange ofρ-mesons,fmesons and a strongI=0S-wave. These models contain between one and three parameters, which are being used to obtain a best fit to Walker'sI=0 data. Our best fits are associated with anI=0 scattering lengtha 0=0.53 μ?1. Having fixed the parameters from theI=0 data, predictions are obtained for theI=2S-wave. Our predictions are generally characterized by a very small positiveI=2 scattering lengtha 2? 0.08 μ?1 and a zero of the phase shift just above threshold, at a total c.o.m. energy of 320 to 360 MeV. The cause for this behaviour is shown to be the strongS-wave in the crossedI=0 channels. Various reasons are discussed, why we might expect this zero to occur at somewhat larger or at smaller energies, even below threshold. Although because of the crudeness of these models the significance of our results is mainly qualitative, certain internal contradictions in the Walker data seem to be indicated. 相似文献
2.
M. P. Grabowski 《Zeitschrift fur Physik C Particles and Fields》1990,48(3):505-509
We compute the finite temperature effective potential in theO(N)xO(N) symmetric model for largeN in spacetime dimensionsd=4, 3, 2 and discuss the spontaneous symmetry breaking patterns. Ford=3 we find that the symmetry, if broken at zero temperature is restored at arbitrarily small nonzero temperature. Ford=4 the model is plagued by an intrinsic instability; in particular, there is no stable ground state at high temperature. 相似文献
3.
《Superlattices and Microstructures》1996,19(3):183-190
The confinement of the flux lines by a lattice of submicron holes (‘antidots’) has been studied in nanostructured superconducting Pb/Ge multilayers. By introducing regular arrays of sufficiently large antidots, multi-quanta vortex lattices have been stabilized. Sharp cusp-like magnetization (M) anomalies, appearing at matching fieldsHm=mφ0/Sin superconducting films with the antidot lattices having a unit cell areaS, are successfully explained. These anomalies are, analogues of the well-knownM(H) cusp atHc1, but for the onset of multi-quanta (m+1)φ0-vortices penetration at each subsequent matching fieldHm. It is shown that theM(H) curve between the matching fieldsHm<H<Hm+1follows a simpleM∝ln(H−Hm) dependence. These experimental observations have revealed an unusual expansion of validity of the London limit in superconductors with lattices of relatively large antidots. The successful high quality fit of theM(H,T) curves convincingly demonstrates that a new type of the critical stateB=const (‘single-terrace critical state’) can be realized in superconductors with the antidot lattices. 相似文献
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5.
Jonathan Dimock 《Communications in Mathematical Physics》1974,35(4):347-356
In theP(φ)2 model it is proved that the perturbation series for the infinite volume Schwinger functionsS(λ) are asymptotic in the limit as the coupling constant λ goes to zero. We also give conditions which imply smoothness ofS(λ) at arbitrary λ. 相似文献
6.
Hai-Yang Cheng 《Zeitschrift fur Physik C Particles and Fields》1986,33(2):237-242
We re-examine QCD sum rules forS-wave charmonium. Dimension 6, 8 contributions for both3 S 1,1 S 0 waves are taken into account using the factorisation model and found to be reasonably small. A good fit to the data requires the confinement parameterφto be much bigger than the generally accepted value. 相似文献
7.
We discuss theO(α S ) corrections to lepton-pair production in a quark-gluon plasma in equilibrium, assuming the quarks are massless at zero temperature. The corrections are found to be very small in the domain of interest for ultrarelativistic heavy ions collisions. Interesting effects, however, appear at the annihilation threshold of the thermalized quarks where the correction factor has a (1/α S ) behavior. 相似文献
8.
The cross section for the reactione + e ?→3S1+1S0 is calculated in the framework of perturbative QCD, using the nonrelativistic approximation for the3S1 and1S0 bound states. The model is applied toJ/Ψ plus η,η,η′, andl production. We find extremely small rates in contrast to previous estimates based on vector meson dominance and discuss possible reasons for this difference. 相似文献
9.
P. Zeyen K. Euler V. Grafen C. Günther M. Marten-Tölle P. Schüler R. Tolle 《Zeitschrift für Physik A Hadrons and Nuclei》1986,325(4):451-456
Low lying levels in203Hg and205Hg were studied with the (d, p) deuteron break-up reaction atE d=14 and 18 MeV. Gamma-rays and conversion-electrons were measured in coincidence with protons. In addition delayed spectra were recorded with us and ms beam pulsing. Thei 13/2 neutron hole state was identified in205Hg and confirmed in203Hg. The known level structure of205Hg below 2 MeV is confirmed and extended. For203Hg we observe theγ-decay of several levels below 1.5 MeV, which were previously known from transfer reactions. 相似文献
10.
S. Büttgenbach R. Dicke G. Gölz F. Träber 《Zeitschrift für Physik A Hadrons and Nuclei》1981,302(4):281-290
The hyperfine structure of the atomic levels 5d 5 6s 2 6 S 5/2 and4 P 5/2 in185Re and187Re has been studied with high precision by atomic-beam magnetic-resonance. Additional measurements were performed in the 5d 5 6s 2 4 G 5/2 and 5d 6 6s 6 D 9/2 states of187Re. For the interpretation of the results eigenvectors in intermediate coupling have been derived by a least squares fit of all known levels of the configurations (5d+6s)7. The ratioB(185Re)/B(187Re) is the same for the6 S 5/2 and the4 P 5/2 state within the error limits of 6 parts in 105. Combining the present results with the known hyperfine structure data of186Re and188Re we find the magnetic-dipole hyperfine anomalies for the isotopic series185?188Re. 相似文献
11.
L. C. L. Hollenberg B. H. J. McKellar 《Zeitschrift fur Physik C Particles and Fields》1990,46(4):609-619
The kaonB parameter is computed in a framework in which static cavity QCD loop corrections to the weak interactions of hadrons are included by extending the Fock state wavefunction to includeO(g) bremsstrahlung and vacuum fluctuation states. Since the QCD corrections are inherent in the calculation of the matrix elements of the bare effective weak ΔS=2 Hamiltonian between hadronic states the scale matching problem of the standard short distance analysis is alleviated. The modified static cavity model used is characterised by four parameters; the effective quarkgluon coupling constant, the confinement pressure, the zero-point energy and a parameter governing the centre-of-mass corrections. These parameters are fitted to the π and ? masses and the charge radii of π andK. Results are given for the ultra-relativistic (m u=m d=0) sector and for a region (m u=m d≈140 MeV) where the ΔI=1/2 rule is uniquely reproduced. For the parameter set which describes the ΔI=1/2 rule we findB K=0.58 at a basis size ofN B=6. 相似文献
12.
We examine the field-theoretical contribution of fermion-antifermion condensates arising from a weak-SU(2) doublet of condensing fermions to electroweak vacuum polarization functions. For the custodial-SU(2) case of equal condensates and masses, we find that the condensate contributions to vacuum polarization functions uphold the electroweak signature relationm w=m zcosθw, and that these contributions are decoupled entirely from oblique radiative corrections. If only the upper member of the doublet forms a fermion-antifermion condensate, the relationm w=m zcosθw is again upheld in the limit that the mass of the lower member of the doublet is small compared to that of the upper member. For this case, the upper-member's fermion-antifermion condensate is shown to enter oblique radiative corrections. In the absense of an explicit Higgs mechanism, identification of this doublet with (t, b) is shown to be excluded by present empirical bounds onS, T, andU parameters. Further phenomenological consequences of fermion-antifermion condensate contributions to theW-Z mass matrix are discussed, both in the absense and in the presence of an explicit Higgs mechanism. 相似文献
13.
Aparajita Chakraborty S. N. Banerjee 《Zeitschrift fur Physik C Particles and Fields》1985,29(3):447-452
Using the statistical model to arrive at |ψ(r)|2 the square modulus of theS state wavefunction of the neutron, the electric dipole moment |d n e | of the neutron as well as its baryon number violating lifetime have been estimated. The baryon asymmetry of the universe depending on |d n e | has also been studied in this context. 相似文献
14.
We apply vacuum background fields method to correct the coefficient functions of theO + andO ? operators in ΔS=1 effective weak Hamiltonian responsible forK→2π decays. The additional relative octet enhancement factor of 2–3 is obtained by accounting for the gluon condensate corrections if the scale parameterπ 2x is set below 1 GeV2. 相似文献
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16.
The electric dipole polarizabilities of 9 even-parity barium states (6s8s 1 S 0,3 S 1; 6s7d 1 D 2,3 D 1,2; 5d7s 1 D 2 and 6p 2 3 P 0,1,2) in the interval 33,800–35,800 cm?1 have been measured with high resolution laser-atomic-beam spectroscopy. Simultaneously, values of isotope shifts and hyperfine coupling constants for theJ=1 states have been obtained. Comparison of the experimental polarizabilities with calculated values as well as inspection of the data on isotope shifts and hyperfine structure from the present and earlier work strongly suggests erroneous assignments of theJ=2 states, with an exception for the 5d 7s 1 D 2 state. The influence of an electric field on the 3d 2 3 P 0,1,2 states of calcium has also been studied. A marked departure from a quadratic Stark effect has been observed at relatively small field strengths. This can be attributed to the large polarizabilities of neighbouring Rydberg states. The low field data allow the determination of admixtures of Rydberg states into the 3d 2 3 P-states as small as 0.02%. 相似文献
17.
James A. Coakley 《Journal of Quantitative Spectroscopy & Radiative Transfer》1973,13(11):1237-1239
Chandrasekhar's equations for the functions S and T which represent the diffuse scattering and the diffuse transmission, respectively, of a beam of radiation by a planar atmosphere are invariant under the transformations S(τ1; μ, φ - μ0), φ0) exp (-τ1/μ0) = T(τ1; μ, φ; μ0, φ0) and T(τ1; μ, φ; -μ0, φ0) exp(-τt/μ0) = S(τ1; μ, φ; μ0, φ0). This relationship reflects the physical symmetry of radiative transfer in a planar atmosphere. It offers a simple method for obtaining the expression for S (T) when an analytical expression for T (S) exists. However, it does not appear to ofter any simplification of numerical solutions. 相似文献
18.
The isobaric energy splitting ΔE(n, l, j) betweenT >- andT <-single particle states in the shell (2d 5/2, 2d 3/2, 1g 7/2, 3S 1/2) has been experimentally determined for91Nb from a study of the reaction90Zr(3He,d)91Nb. The splitting of the 1g 7/2-states is found to be about 25% larger than that of the3 s 1/2-states. The observed dependence of the energy splitting ΔE(n, l, j) on the shell model quantum numbers (n, l, j) of the states is reproduced by the expression \(\Delta {\rm E}(n, l, j) = \frac{1}{2}(2T + 1) \left\langle {\phi _ > ^{n l j} | U_1 (r)|\phi _ > ^{n l j} } \right\rangle\) , which is based on approximate solutions of Lane's equations.φ > nlj is the wave function of the parent state in the (nC) system. There is evidence, that only a Lane potentialU 1(r) of surface type can reproduce the observed strong dependence of ΔE(n, l, j) on the quantum numbers. The depthū 1 of Lane's potential is found to be 2.0 MeV. 相似文献
19.
A method of classifying quark operators in QCD sum rules is suggested. The expansion coefficients of all thed≦8 bilinear quark condensates in gluon condensates are calculated. The coefficient functions at the gluon operators withd≦8 in the polarization operator ∏(q 2) of the light-quark vector current are obtained. A comparison is performed with the calculations in the covariantly constant fields and self-dual fields. The results obtained can be used in the sum rules for the ρ, ω and ? families. 相似文献
20.
Recently the Navier-Stokes equations have been derived from the duality with the black branes in 5AdS. The zero modes of black branes are reinterpreted as dynamical degrees of freedom of a conformal fluid on the boundary of 5AdS. Here, we derive the corrections to the Navier-Stokes equations due to fermionic zero modes of the black branes. We study only the contributions due to bilinears in the fermionic zero modes in the first order of the parameter expansion. The need of a superextension of the fluid dynamics is a consequence of the full AdS/CFT correspondence and yet to be investigated. 相似文献