共查询到20条相似文献,搜索用时 62 毫秒
1.
The threshold behaviour of pion production presented in our earlier work is successfully compared with the new SPEAR data. By using duality and sum rules we derive FT(π+)(x) ≈ FL(π+)(x) ≈ FT(π0)(x) ? FL(π0)(x) for x near 1. An accompanying results is for large s. 相似文献
2.
Assuming that the sea quark distribution vanishes for x > 0.3, we analyse the F2Fe(x, Q2) and F2D(x, Q2) structure functions measured by the European Muon Collaboration in the framework of a thermodynamical model of the valence quarks. The experimental ratio is well reproduced over the whole x range by the ratio of two valence quark distributions at different temperatures T and confinement volumes V. We obtain TD?TFe≈3 MeV and . 相似文献
3.
Victor Elias 《Physics letters. [Part B]》1977,68(4):335-338
The Callan-Gross relation is shown to be consistent with MIT-SLAC data for for x ? 0.33 in deep inelastic eN scattering, despite the fact that these data are taken in the large Q2 region where F1 and F2 individually exhibit scaling violation. Comparison is made with asymptotic freedom predictions, and color excitation is proposed to explain large values of at small x. 相似文献
4.
Robert W. Field Richard A. Gottscho E. Miescher 《Journal of Molecular Spectroscopy》1975,58(3):394-413
No perturbation between two valence states of NO has ever been identified, although many valence-Rydberg and several Rydberg-Rydberg perturbations have been extensively studied. The first valence-valence crossing to be experimentally documented for NO is reported here and occurs between the 15N18O B2Π (v = 18) and B′2Δ (v = 1) levels. No level shifts larger than the detection limit of 0.1 cm?1 are observed at the crossings near and ; two crossings involving higher rotational levels could not be examined. Semi-empirical calculations of spin-orbit and Coriolis perturbation matrix elements indicate that although the electronic part of the interaction is large, a small vibrational factor renders the 15N18O B (v = 18) ? B′ (v = 1) perturbation unobservable. Semi-empirical estimates are given for all perturbation matrix elements of the operators and which connect states belonging to the configurations , , and . 相似文献
5.
H.-P. Dürr 《Physics letters. [Part B]》1982,115(1):33-39
A theory based solely on a 2×(N=2)-component Weyl spinor field χ(x) of subcanonical dimension allows the local construction (without derivatives) of effective fermi and bose fields with spins up to N=2. It is demonstrated that the lagrangian studied earlier is invariant under a global N=2 supersymmetry transformation and can be cast into a form involving the scalar chiral superfield the components of which are finite part products of the basic field. The theory can be generalized to an N-supersymmetric theory in a 2N-dimensional space-time yielding the Thirring model as special case for N=1. 相似文献
6.
The cross-channel isospin amplitude is measured in the single reaction γn → ?0(pπ?) at 7.5 GeV assuming the ?0 dominance model. A low-mass enhancement is found for in the range of m(pπ?) of ~1.2 to ~1.7 GeV. The reaction strongly violates s-channel helicity conservation but is consistent with t-channel helicity conservation. The features are found to be very similar to those obtained in previous analyses of πp → π(Nπ) reactions. 相似文献
7.
The predictions of perturbative QCD are derived in the deep euclidean region, whereas the physical region for most observables is timelike. The confrontation of these predictions with experiment thus necessitates an analytic continuation. This we find introduces large higher order corrections in terms of αs(|Q2|), the usual choice ofperturbative expansion parameter. These corrections are naturally absorbed by changing to the expansion parameter , where αs(Q2)n is the leading term in the spacelike region. For the intermediate range of Q2 experimentally accessible at present, where is significantly smaller than αs(|Q2|), we find the resulting phenomenology is improved. In particular, we demonstrate how the values of obtained from analyses of quarkonium decays become consistent. 相似文献
8.
G. Gidal J.W. Chapman R.P. Ely W. Michael P. Oddone D. Scharre 《Physics letters. [Part B]》1978,76(5):657-662
Interference between the and baryon exchange amplitudes is observed in the reaction π?p → pπ?π0, with the proton produced forward with . The Dalitz plot shows that the reaction is dominated by the quasi two body final states ρ?p(δ exchange) and , with δ(1238), N1(1520) and higher mass N1's also produced. The relative phase between the ρ and the N1(1670) production amplitudes is measured to be 135° ± 10° and is compared with the Regge pole signature factor phase predictions. 相似文献
9.
We make a theoretical and phenomenological study of correlations between neutral and charged pions in multiparticle production in the framework of the so-called σ, π, ? and ?-? models. Following the method of Drijard and Pokorski, we express the predictions of various models in terms of the negative multiplicity distribution, which is known experimentally. In particular we compute the average number of , and the integral of π0?π0 correlations, f02(n_), as a function of the number of negative pions; we study also the total multiplicity distribution P(N) and its first two moments . We show that with the present experimental accuracy neither allow us to discriminate between the different models. 相似文献
10.
Nuclear spectroscopic quadrupole moments of the radioactive isotopes 131Cs, 132Cs, and 136Cs have been determined from the hyperfine structure of the state by the level crossing method. The results including a Sternheimer correction are: , , . The quadrupole moments of all the Cs isotopes from A = 131 to A = 137 are recalculated. It is shown, that nuclear quadrupole moments of a specific isotope obtained from different atomic P-states only agree within the limits of error after application of the Sternheimer correction. The increase of Qs with decreasing neutron number conforms with other observations and theoretical calculations stating that for elements around Z = 55 nuclear deformation develops below N = 82. The staggering of the sign of Qs may be interpreted as consequence of an oblate-prolate degeneracy of the nuclear energy surface. Some magnetic moments have been slightly improved: , (corrected for diamagnetism). 相似文献
11.
A.H. Mueller 《Nuclear Physics B》1984,241(1):141-154
The order correction to the particle multiplicity ratio in gluon and quark jets is calculated in QCD. We find with r=〈n〉gluon jet/〈n〉quark jet. The method used is systematic and could be used for an order α(Q2) calculation. 相似文献
12.
Otto Nachtmann 《Nuclear Physics B》1974,74(3):422-428
Recent experimental results on electroproduction off protons show that the ratio σ(ep → eK+Σ0)/σ(ep → eK+Λ) decreases strongly with increasing Q2. A simple argument is given in the framework of the quark parton model which could provide a qualitative understanding of this fact. The decrease of the Σ0/Λ ratio is related to the decrease of the ratio as Q2 increases, where are the usual structure functions for deep inelastic electron-nucleon scattering. 相似文献
13.
K. Moriyasu T. Burnett D. Holmgren H.J. Lubatti D. Rees G. Swider B. Yuldashiev K. Dziunikowska A. Eskreys K. Eskreys A. Gula D. Kisielewska H. Rudnicka P. Stopa W. Ko R.L. Lander J.S. Pearson D. Pellett A. Zieminski 《Nuclear Physics B》1978,137(4):377-389
Double-scattering effects are studied in π?d interactions at 360 GeV/c. The partial cross sections are presented. The double-scattering probability per πd collision is found to be . We have extracted the partial cross section XN of the double-scattering plus interference contributions, and find that XN obeys KNO scaling. The data are compared with various theoretical predictions. 相似文献
14.
The charged current neutrino–nucleon interaction differential cross section are evaluated in the kinematical range 30<Eν<300 GeV, 0.1<x<0.8 and 0<y<1 using QCD inspired Thermodynamic Bag Model (TBM). We also discuss the x and Q2 dependence of nucleon structure functions F2(x,Q2) and xF3(x,Q2) estimated with statistical approach. The contribution of strange quark distribution function to the cross section is explored and the results obtained have been compared with relevant data from NuTeV and CHORUS experiments. 相似文献
15.
D. Denegri Y. Pons R. Barloutaud A. Borg C. Louedec M. Spiro K. Paler T.P. Shah S.N. Tovey B. Chaurand B. Drevillon G. Labrosse R. Lestienne R.A. Salmeron 《Nuclear Physics B》1975,91(1):54-68
We have studied the reaction K-p → K-π+π-π+π-p at 14.3 GeV/c to search for evidence of the double dissociation process . In the channel π1-π2-Δ++ (1236) there is evidence for simultaneous production of low-mass enhancements in the and Δ++(1236)π2- subsystems which correspond to the and decay modes. In this particular final state the double fragmentation system is produced with a cross section of the order of a few microbarns. Our data are consistent with the factorizable pomeron exchange model of double diffractive dissociation. 相似文献
16.
Jan T. łopuszański 《Reports on Mathematical Physics》1976,9(3):301-307
It is shown that for spinorial charges Q(L))α (α = 1, 2, L = 1, …, S) satisfying the commutation relations where Q is a scalar charge commuting with the spinor charges as well aswith the energy- momentum vector Pμ, there can exist several different multiplets for free massive scalar and spinor fields. 相似文献
17.
P. Brauel F.-W. Büsser Th. Canzler D. Cords W.R. Dix R. Felst G. Grindhammer W.-D. Kollmann H. Krehbiel J. Meyer G. Weber 《Physics letters. [Part B]》1973,45(4):389-393
The reaction e + p → e′ + π+ + n was measured near the one pion threshold, detecting the final electron and neutron in coincidence for values of q2 = 0.2, 0.4 and 0.6 GeV2. The normalized axial vector form factor to the nucleon was determined from the data within a theoretical framework based on PCAC and current algebra. 相似文献
18.
Mahiko Suzuki 《Nuclear Physics B》1974,69(2):413-425
By use of the generalized scaling sum rules the vector-axial vector interference terms in the scaling limit of the inelastic neutrino reactions are calculated from the absorptive parts of the single-pion photoproduction amplitudes at zero momentum transfer. The photoproduction amplitudes are evaluated by use of the results of multipole analysis. With the optimum values for the two parameters of the generalized scaling as determined in previous works, we have obtained F3νN(ω) which leads to good agreement with experiment in the ration of . However, the zeroth moment in turns out to be smaller than half of the value predicted in the fractionally charged quark model. 相似文献
19.
H. Braun J-P. Gerber G. Maurer A. Michalon B. Schiby R. Strub Z. Strachman 《Nuclear Physics B》1975,95(3):503-515
A cross-channel isospin analysis has been performed on the channels in terms of three isospin amplitudes , and where the upper index is the isospin of the exchanged “object” in the t-channel and the lower index is the isospin of the system. Enhancements are observed in the low Nπ) invariant mass region for an final state when the isospin of the exchanged object in cross channel is IE = 0 and 1. 相似文献
20.
The total cross section for the production of a muon pair of invariant mass Q2via the Drell-Yan mechanism and the Feynman xF differential cross section are calculated in QCD retaining all terms up to order αs(Q2. The calculations are performed using dimensional regularisation of the intermediary infrared and collinear singularities, but we present our results in a form independent of such details. The corrections to both these cross sections coming from radiative corrections to the lowest-order annihilation diagram are found to be large at present values of Q2 and S when the cross section is expressed in terms of parton densities derived from leptonproduction, for all Drell-Yan processes of practical interest. Numerical calculations are presented which show, for any reasonable parametrisation of the parton densities, that the neglect of higher-order terms in αs(Q2) is not justifiable. The quark-gluon diagrams on the other hand give small corrections in this order and are only important for PP scattering. 相似文献