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 343 毫秒
1.
Conclusion We have constructed the pion form factor model satisfying fundamental principles, providing some freedom for the asymptotic behaviour and depending only on the adjustable parameters with a definite physical interpretation. The explicit incorporation of the pion form factor left-hand cut from the second Riemann sheet into a model was carried out for the first time. As a result we have described (contrary to the previous attempts [18, 19]) the pion form factor data from the range of momenta –9·770 GeV2 t 9·579 GeV2 and data on theP-wave isovector phase shift in the elastic region simultaneously with the adjustable parameters acquiring very reasonable values. The asymptotic behaviour was enforced by the data to be consistent with the naive quark model prediction. The calculated values of the pion charge radius as well as theP-wave isovector scattering length coincide with the world averaged values. With regard to these positive features of our pion form factor model it can be employed for the reliable calculation (via unitarity) of theP-wave isovector scattering partial amplitude outside the physical region, which could be useful in a saturation of various sum rules in scattering physics.  相似文献   

2.
Using the approximative expression for the elastic energy density of the antiferroelectric (AF) liquid crystal the elastic self-energy of (, b)-wedge-screw dispiration is estimated. Then the elastic interaction between (, b)-wedge-screw dispiration and (2)-wedge dischnation in AF liquid crystals is investigated. The attraction of dislocation part of dispiration with (2)-wedge disclination can lead to the formation of (3)-wedge-screw dispiration. When (2)-wedge disclination is trapped by (2d)-screw dislocation the resulting (2, 2d)-dispiration can dissociate into a pair of two (, d)-dispirations.The authors express their thanks to Professors A. Fukuda, H. Takezoe, Dr. Y. Takanishi and to Dr. K. Miyachi for discussions concerning their experimental observations of (3, d)-wedge-screw dispirations and (, d)-twist-edge dispirations in AF structures. This work was supported by the grant No. 19062 from Acad. Sci. Cz. R. and also benefited by the grant No.: 202/93/155 from the Grant Agency of the Czech Republic.  相似文献   

3.
A heuristic model for deriving the anomalous magnetic moment of the electron is presented. A term /2 – 0.327(/)2 is deduced, in better agreement with experiment than is the QED derivation of /2 – 0.328(/)2. The result is strengthened by the recent non-QED account of the Lamb shift by Yu and Sachs.  相似文献   

4.
In the present paper, the feasibility of constructing a model of elementary and particles based on the Poincaré model of the electron [1] is examined with allowance for schemes of particle decay. The muon and pion in stopped states are considered as spherical resonators for virtual neutrino quanta excited inside an elastic lepton shell; the number of these quanta is determined by the scheme of the corresponding particle decay. In the model, the muon differs from the electron by two additional quanta of the neutrino field. The e, , and masses are calculated with the help of a single parameter. The ratio of and e masses is about (6c/e 2)2/3, and the ratio of ° and e masses is (3/2)2/3. The calculated e, , and ° masses are in the 0.547:105.71:134.963 ratios, which is in good agreement with the available experimental data. The calculated electromagnetic radius of the charged pion (±) = 0.5f is close to that calculated from the experimental data. The neutrino mass e is found to be m( e ) 0.02 eV.  相似文献   

5.
Several recent developments in the meson exchange theory of hadronic interactions are reviewed. After some introductory remarks about the relevance of the meson exchange concept in the era of QCD we will describe a dynamical model for correlated 2-exchange in the NN as well as the N interaction; for the NN system, it should replace the (sharp mass) and exchange used in the Bonn potential. Next we turn our attention to the interaction. A recently proposed meson exchange model can resolve in a natural way apparent discrepancies occurring in the analysis of different experiments in connection with the A1 meson and leads to an appreciable softening of the NN form factor.Lecture presented at the Indian-Summer School on Interaction in Hadronic Systems, Praha (The Czech Republic), 25–31 August 1993.  相似文献   

6.
Conclusions We have presented soms of our preliminary results on the coupled NN-NN problem. The overall result obtained so far is rather encouraging and we are currently making the model more sophisticated in order to be able to make more quantitative arguments which may hopefully serve somehow to clarify the dibaryon resonance problems. To end we would like to emphasize that since all the channels (viz.d d, d NN, NN NN, etc.) are unitarily coupled, one cannot arbitrarily change some input parameters to attain a better fit in one of the channels alone: all the channels are closely linked, which serves as a very strong constraint to the input. In near future we wish to extend our model to calculate processes with three-body final statesWork supported in part by Bundesministerium für Forschung und Technologie.Invited talk at the symposium Mesons and Light Nuclei, Liblice, Czechoslovakia, June 1981.I am grateful to my collaborators, Y. Avishai, C. Fayard, G. -H. Lamot and S. Nahabetian for numerous discussions.  相似文献   

7.
    
In this paper we present the results of a search for the charmed strange baryon c + in the final states 0++K and ++. The experiment was performed using the magnetic spectrometer BIS-2 with a hydrogen target located in the neutron beam of the Serpukhov accelerator. A narrow peak in the 0++K state is observed at a mass of 2440 and possibly also of 2310 MeV/c2, corresponding to signals for the c + 0++K and c + 0++K (0 0) decays respectively. The statistics obtained for the ++ state is too low to make any conclusion.We are grateful to K. Hiller, F. Mandl, M. Markytan and J.MacNaughton for useful discussions and valuable remarks.  相似文献   

8.
The solvent and temperature effect of fluorescence and phosphorescence and its polarization characteristics for -carboline-3-carboxylic acid N-methylamide were studied. From the results obtained it is concluded that the first excited singlet state changes from the * type in a polar solvent (EPA) to the n* type in a nonpolar solvent (MC) and that the lowest singlet excited states (* type and n* type) interact by vibronic coupling. In the nonpolar solvent (MC) the lowest singlet excited states are very close in energy and consequently the vibronic coupling is stronger. It has been found that the 0–0 band of the phosphorescence emission in EPA is polarized out of plane, using the excitations corresponding to absorptions into the first and second excited * singlet states. This fact and the order of lifetime measured indicate an emitting triplet that is *. The origin of this polarization is very likely mixing as a result of spin–orbit coupling. However, the vibrational structures and changing polarization outside the 0–0 band indicate that second-order effects involving spin–orbit coupling and vibronic interactions are important and the mixing scheme appears to be and . The proximity effect can qualitatively explain the absence of phosphorescence and the stronger vibronic interaction between the n* and the * states of -carboline-3-carboxylic acid .N-methylamide in a hydrocarbon solvent (MC).  相似文献   

9.
The s-wave pion scattering amplitude is analysed with the aim to clarify the mass spectrum of scalar mesons and to find evidence of lightest glueball. The S-matrix and K¯K coupled channel formalism is used. The existence of scalar mesons S* and is implied by the data. The production K¯K and the elastic K¯KK¯K coupled amplitudes are predicted from the scattering data. The couplings c f S* to and K¯K states are determined.  相似文献   

10.
The long-wave * transitions and weak n * transitions are discussed for several compounds of practical importance. Wave functions are presented for aliphatic ketones, acids, and esters.  相似文献   

11.
We present fermionic sum representations of the characters , s (p, p) of the minimal M(p,p) models for all relatively prime integers p>p for some allowed values of r and s. Our starting point is biomial (q-binomial) identities derived from a truncation of the state counting equations of the XXZ spin 1/2 chain of anisotropy –=–cos((p/p)). We use the Takahashi-Suzuki method to express the allowed values of r (and s) in terms of the continued fraction decomposition of {p/p} (and p/p), where {x} stands for the fractional part of x. These values are, in fact, the dimensions of the Hermitian irreducible representations of SU q- (2) (and SU q+ (2)) with q–=exp(i{p/p}) (and q+=exp(i(p/p))). We also establish the duality relation M(p,p) M(p–p,p) and discuss the action of the Andrews-Bailey transformation in the space of minimal models. Many new identities of the Rogers-Ramanujan type are presented.Dedicated to Prof. Vladimir Rittenberg on his 60th birthday  相似文献   

12.
The calculation of the secondary nucleons polarization in thepppp0 andppnp+ reactions at 1000 MeV is effected in the framework of the one-pion exchange model. It is shown that polarization is due to the interference of the resonant amplitude with the non-resonant amplitudes of theN virtual scattering. The angular dependence of the polarization is sensitive to the behaivour of theN scattering amplitudes off the mass shell.Submitted to the symposium Mesons and Light Nuclei, Liblice, Czechoslovakia, June 1981.  相似文献   

13.
Nucleon polarizations are examined in the hypernucleus decays5He, 4He + p + ,4H, 3H + p + , and4H, 3He + n + . The effect of the strong interaction in the final state is taken into account. A significant role is predicted for the resonance interaction in the p-4He system in the formation of the proton polarization in the5He decay. It is also shown that in the4H, 3H + p + decay the proton-polarization components should attain significant magnitudes, while in the charge-exchange decay4H, 3He + n + , the neutron polarization is expected to be not too large.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 100–103, October, 1988.  相似文献   

14.
P-odd effects in the photoproduction of pions on6Li nuclei, +6Li + +6He, are studied. Collisions of linearly and circularly polarized photons with a polarized nuclear target are studied, and in addition both vectorial and tensorial polarization are taken into account. It is shown that in the general case P-odd effects in +6Li + +6He are characterized by 18 real structure functions, which determine different P-odd asymmetries in the angular distribution of the pions. The structure functions in their turn depend on different products of three p-even and three p-odd amplitudes of the process +6Li + +6He. The P-odd effects at the threshold of the reaction +6Li ++6He are analyzed. Using available experimental data on the behavior of the cross section of the reaction +6Li + +6He at threshold, the 6Li6He strong-interaction constant is evaluated.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 78–82 July 1985.  相似文献   

15.
Summary There has been remarkable experimental and theoretical progress in the field ofd interactions in the last few years. Within the uncertainties of the theory the experimental data in thed breakup and thed elastic scattering reaction can be fairly well reproduced. Theoretical problems remain in the absorption channel, but there is a hope that with a few additional measurements of tensor polarization and spin transfer observables in this reaction a partial wave amplitude analysis may localize the theoretical difficulties. In addition it is very important to provide data on the deuteron tensor polarizations and the spin transfer parameters for thed elastic scattering reaction in order to obtain a reliable set of phase shifts, which may reveal resonance structures in this reaction channel.Invited talk to the symposium Mesons and Light Nuclei, Bechyn, Czechoslovakia, May 27–June 1, 1985.  相似文献   

16.
The paper considers the processes of formation of pseudoscalar mesons by the interaction of an antineutrino with a leptonv ll K, , K.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 139–143, August, 1974.  相似文献   

17.
LetA be aC*-algebra andG be a locally compact group acting as strongly continuous automorphisms onA. Let be a representation ofA then we say is a covariant representation if there exists a strongly continuous unitary representation of the group acting onH which implements the automorphisms. We give necessary and sufficient conditions on a representation ofA such that a) is subrepresentation of a covariant representation and b) is subrepresentation of a covariant representation quasi-equivalent to .  相似文献   

18.
The ultraviolet stability for the cosine interaction in two dimensions and finite volume is rederived for values 2 [4, 32/5[ and proven for the remaining 2 [4, 8[ by using renormalization group methods developed in [G, GN1] to portray renormalized effective potentials arising from a multiscale decomposition.Supported by the Studienstiftung des Deutschen VolkesSupported in part by the Schweizerischer Nationalfonds  相似文献   

19.
We report an experimental and theoretical (PPP method) study of the UV absorption spectra of 2-azaanthracene and four of its methyl-substituted derivatives. We find that the p bands of these compounds consist of two different vibronic * bands. Our experimental and theoretical results suggest a rule for evaluating the effect of methyl groups on * transition energies as a function of the charge on the atoms. We interpret the reasons for the different effects of a polar solvent and hydrogen bonding on the * bands of these compounds.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 7–15, June, 1977.  相似文献   

20.
The collective structures of 131Cs have been investigated by in-beam -ray spectroscopic techniques following the 124Sn (^11B , 4n) reaction at a beam energy Elab = 57MeV. The previously established rotational bands, built on g7/2, d5/2 and the unique-parity h11/2 orbitals, have been extended and evolve into new bands involving rotationally aligned (h11/2)2 and (h11/2)2 quasiparticles. In addition, a new multiquasiparticle band based on the g7/2 g7/2 h11/2 configuration has also been observed. Theoretical interpretations for the assigned configurations are discussed in the framework of Total Routhian Surface (TRS) and Tilted Axis Cranking (TAC) model calculations. TAC model calculations predict a decrease in the B(M1) values with increasing rotational frequency for the g7/2/d5/2 (h11/2)2 and h11/2 (h11/2)2 bands, thus indicating a magnetic rotation character for these bands.  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