共查询到20条相似文献,搜索用时 31 毫秒
1.
A. Quenzer M. Ribes F. Rumpf J.L. Bertrand J.C. Bizot R.L. Chase A. Cordier B. Delcourt P. Eschstruth F. Fulda G. Grosdidier J. Jeanjean M. Jeanjean R.J. Madaras J.L. Masnou J. Perez-Y-Jorba 《Physics letters. [Part B]》1978,76(4):512-516
The pion form factor is measured in the reaction e+e? → π+π? for center of mass energies in the range 480–1100 MeV. Our results are first analysed in terms of the conventional Vector Meson Dominance formalism, and then taking into account the ωπ inelastic channel. The result of this later formalism is a pion form factor (Fπ) which fits quite well all the existing data on Fπ both in the timelike and spacelike regions, and pion mean square radius of 〈rπ2〉 = 0.460 ± 0.011 fm2 or . 相似文献
2.
Michał Praszałowicz 《Physics letters. [Part B]》1985,158(3):264-269
We find that the realistic baryon mass spectrum in the SU(3) Skyrme model with massive 0? mesons can be obtained only for Fπ < 70 MeV. We fit mΛ and and obtain baryon masses within the limits of ± 16% of the experimental val ues, but at the expense of very low ifFπ=46.32 MeV. 相似文献
3.
M.J. Corden J.D. Dowell J. Garvey R.J. Homer M. Jobes I.R. Kenyon T. McMahon R.C. Owen K.C.T.O. Sumorok R.J. Vallance P.M. Watkins J.A. Wilson P. Sonderegger B. Chaurand A. Romana R. Salmeron 《Physics letters. [Part B]》1981,98(3):220-224
J/ψ production at 40 GeV/c by π±, K±, p and incident on hydrogen has been studied and results compared with those obtained on tungsten in the same experiment. On hydrogen, J/ψ cross-section ratios relative to π? have been measured to be (for . The suppression of the proton induced cross sections shows the importance of calence quark-antiquark fusiin J/ψ production at this energy (i.e. MJ2/ψ/s=0.13). 相似文献
4.
H. Taureg G. Zech F. Dydak F.L. Navarria P. Steffen J. Steinberger H. Wahl E.G.H. Williams C. Geweniger K. Kleinknecht 《Physics letters. [Part B]》1976,65(1):92-96
The branching ratio has been determined to be (2.68±0.15)×10?3 for photon energies greater than 50 MeV in the KS0 rest frame. The decay KS0→π+π?γ is found to be dominated by the internal bremsstrahlung transition. The branching rato of a possible direct transition is found to be less than 0.06 × 10?3 at 90% confidence level for . 相似文献
5.
Three enhancements are observed in the final state ω°π+π+π++π?π? selected from the channel at 715 MeV/c: one in ω°π± at 1040 MeV (~ ≈ 55MeV) ω°π+π?, respectively near 1315 MeV (~ ≈ 100 MeV) and 1405 MeV (~ ≈ 40 MeV). The first two effects are strongly correlated and are interpreted in terms of a sequential decay A°2 through a new object, the B1. The second (ωππ) enhancement seems to be an ?°?° effect below threshold and is attributed to a pionic decay of the effect seen around the same mass in other reactions. 相似文献
6.
C. Defoix L. Dobrzynski P. Espigat M. Laloum P.Ladrón de Guevara C. Angelini A. Bigi R. Casali R. Pazzi 《Nuclear Physics B》1980,162(1):12-40
An experimental analysis of interactions between the p threshold (√s = 1878 MeV) and √s = 2 100 MeV leads to clear evidence for an s-channel effect in the reaction . A comparison is made with the backward elastic scattering and charge-exchange behaviour. An interpretation in terms of an object strongly coupled to mesonic decay modes, with small or middle-sized elasticity (x ? 0.135?0.06+0.13) is given. No significant narrow structure is observed in the backward elastic scattering between 1.9 and 2 GeV. The experimental resolution of √s in this case is 2 MeV. 相似文献
7.
R.J. Sparks 《Nuclear Physics A》1976,265(3):416-428
The yield curve of the reaction 34S(p, γ)35Cl has been measured over the energy range Ep = 1.95–2.91 MeV. Proton energies and strengths of 84 resonances are given. The decay schemes of 38 selected resonances have been studied, and for these branching ratios and spin limits are presented. The proton energy of the well known analogue resonance has been measured as Ep = 1211.45 ± 0.09 keV. The reaction Q-value is Q = 6371.6 ± 0.4 keV. 相似文献
8.
G. Otter H. Remplewski G. Rudolph L. Becker R. Klein W. Lohmann H.J. Schreiber K. Böckmann U. Idschok J. Lowsky B. Schröder D.J. Kocher D.R.O. Morrison K.-L. Wernhard T. Coghen K.W.J. Barnham R. Eason H. Rohringer 《Nuclear Physics B》1979,155(2):295-306
Results are presented for p → (ΛK+) dissociation in the reactions K?p → ΛK+K? and and π±p → ΛK+π±at 10 and 16 GeV/c. The cross sections for the low-mass ΛK+ enhancement are compatible with the energy dependence σ ∝ plab?0.3. The t′ spectra or the (ΛK+) threshold enhancement are exponential in shape. Its decay angular distribution reveals neither s-channel nor t-channel helicity conservation. The relative probabilities of the processes dissociation are in the ratios 100 : 10 : 0.2, independent of the nature of the incident particle. 相似文献
9.
The reaction 12C(7Li, t)16O has been studied at with the LASL tandem accelerator and QDDD magnetic spectrometer. Angular distributions to levels with Ex < 11 MeV have been obtained from 0° to 90°, including 0°. The results have been analyzed with finite-range distorted-wave Born approximation theory. The α-particle spectroscopic factors and reduced widths obtained are compared with those calculated with group theory (SU(3)) and other models. The analysis of data for the 7.1 and 9.6 MeV Jπ = 1? levels, which are of great importance in stellar helium buring, yields a ratio, R, of dimensionless reduced α-widths . The observed line width of the 9.6 MeV level (Γc.m. = 390 ± 60 keV) is less than the accepted value (Γc.m. = 510 ± 60 keV) and implies θ2a(9.6 MeV) ≈ 0.6. These results as well as data for the 6.92 MeV Jπ = 2+ and 10.35 MeV Jπ = 4+ “α-cluster” states indicate 0.09 < θ2a(7.1 MeV) < 0.33 with a mean value θ2a(7.1 MeV) = 0.14 ± 0.04. The implication for stellar helium burning is discussed. 相似文献
10.
D. Ziemińska 《Nuclear Physics A》1975,242(3):461-466
The branching ratios are calculated for 11ΛB decay to the 11C ground and excited states below 8 MeV for two possible spin values of 11ΛB. It is found that the decay rate to the 11C★ state at E★ = 6.48 MeV is comparable in magnitude to that leading to the 11C ground state if is assumed. This result, unlike the branching ratios calculated for the case, is in accord with experiment and lends support to the assumption that holds for 11ΛB. The necessity of the reinterpretation of some of the so-called 13ΛC events in terms of is indicated. 相似文献
11.
H. Takeda I. Arai T. Fujii H. Ikeda H. Iwasaki N. Kajiura T. Kamae S. Kawabata K. Ogawa T. Sumiyoshi H. Fujii S. Homma M. Kanazawa N. Yamashita 《Nuclear Physics B》1980,168(1):17-31
The recoil proton polarization for γn → π?p was measured around the third resonance region. Both momentum vectors of the proton and the pion were determined by the magnetic spectrometers. The proton polarization was measured by means of proton-carbon scattering in the polarization analyzer located behind the proton spectrometer. Below 900 MeV incident photon energy, our data are consistent with the other existing experimental data () and the predictions of partial-wave analyses. Above 1000 MeV, however, a large discrepancy was observed between our data and the predictions of the partial-wave analyses. The discrepancy stands out as the pion c.m. angle increases. A new partial-wave analysis was made for γn → π?p including our polarization data, and the accuracy of the experimentally determined electromagnetic coupling constant of the third resonances were greatly improved. In particular, a finite amount of the helicity amplitude for the γn → F15(1688) resonance was obtained against the predictions of the quark models, by Copley, Karl and Obryk and by Feynman, Kislinger and Ravendal but in agreement with the relativistic quark models of Sugimoto and Toya, and Kubota and Ohta. 相似文献
12.
S. Lichtman J.M. Bishop N.N. Biswas N.M. Cason E.A. Harrington V.P. Kenney W.D. Shephard P.H. Stuntebeck 《Nuclear Physics B》1976,105(2):229-240
Studies have been made of the rare reactions and , and of and , with cross sections of 18.5 ± 5.5, 10.7 ± 3.0, 12.0 ± 5.0, and 19.7 ± 4.8 μb, respectively. Production characteristics of these reactions are examined and effective-mass spectra are presented. There is no significant evidence in the data for production of Ψ(3095) in the baryon-antibaryon system, or for any other high-mass resonances. 相似文献
13.
The cross section for the reaction has been measured at θlab = 135° over the proton energy range 93 ≦ Ep ≦ 418 keV. The results are in good agreement with the less precise but much earlier measurements of Schardt, Fowler and Lauritsen (1952). An analysis of the present data in terms of a two-level calculation including the 338 keV (1?) and 1028 keV (1?) resonances determines a zero-energy intercept for the astrophysical S-factor of S(0) = 78 ± 6 MeV · b. 相似文献
14.
S. Cochavi S. Gilad M.A. Moinester J. Alster M. Buenerd P. Martin 《Nuclear Physics A》1974,233(1):73-80
The 91Zr(d, 3He) reaction was studied at a deuteron energy of 28 MeV. Angular distributions were measured from 13° to 47°; lp values were extracted for the prominent lines of 90Y. The lp values and transition strengths were determined by DWBA analysis. The angular distributions for the doublet (g.s. and 0.20 MeV state) exhibit the characteristic l = 1 shape. States at 1.42, 1.57, 1.64 and 1.81 MeV were also populated strongly in the (d, 3He) reaction; the 1.42, 1.57 and 1.81 MeV levels contain l= 1 transition strength and are most likely members of the multiplet. The 2.03 MeV state has a characteristic l = 3 angular distribution and is suggested to be the only member of the sextet to be unambiguously observed in this study, most probably the 5? or 4? member. The members of the sextet were populated weakly (less than 100 μb/sr) in this reaction. 相似文献
15.
O. Häusser T.K. Alexander D.L. Disdier A.J. Ferguson A.B. McDonald I.S. Towner 《Nuclear Physics A》1973,216(3):617-628
The α-decay of several unbound levels in 20Ne has been studied by 16O(α, α) elastic and inelastic scattering. A narrow resonance, Γc.m. = 13±4 eV, with Jπ = 5? was found at and is associated with the lowest K = 2? quasirotational band. Several new, narrow resonances were found between Ex = 16.0?18.4 MeV. Reduced α-decay widths have been obtained for the lowest K = 0+, 2? and 0?bands. For states described predominantly by the (8, 2) representation of SU(3) we note a reduction of the reduced widths with increasing spin. Reduced widths of positive parity bands are reviewed. 相似文献
16.
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
17.
C. Daum L.O. Hertzberger W. Hoogland R.T. Jongerius G. Polok W. Spierenburg H.G. Tiecke L.W. Wiggers D.G. Bardsley J. Malos R.J. Tapper R.J. Whyley M. Bosman M. Cerrada V. Chabaud B. Hyams J.C. Vermeulen F. Wickens 《Physics letters. [Part B]》1981,104(3):246-250
Inclusive øø production has been studied in π?-Be interactions for 100 and 175 GeV incident momentum. An upper limit of 72 nb has been set for . At both momenta the number of øø events is larger than expected for uncorrelated ø pairs. A narrow width enhancement is observed at Møø≈2100 MeV with a 4 standard deviation significance. 相似文献
18.
P.V. Chliapnikov P.A. Gorbunov S.A. Gumenyuk V.V. Kniazev B.A. Manyukov V.M. Perevoztchikov V.N. Riadovikov V.A. Uvarov M.L. Faccini-Turluer M. Loret L. Mosca H. Blumenfeld J. Laberrigue C. Dujardin F. Grard J. Skura R. Windmolders M. Csejthey-Barth M. Gysen 《Nuclear Physics B》1977,131(1):93-106
A study of the inclusive and semi-inclusive Λ and production in K+p interactions at 32 GeV/c is presented. The inclusive cross sections for Λ and amount to 0.78 ± 0.05 and 0.42 ± 0.04 mb thus showing a remarkable growth between 16 and 32 GeV/c with a factor of 1.7 for Λ and 2.8 for . Target and beam fragmentation processes are found to be dominant for Λ and production respectively with the following lower limits for the corresponding cross sections: and . Although the early scaling conditions are fulfilled for the Λ production in the target fragmentation region, and production in the beam fragmentation region, scaling is not observed between 16 and 32 GeV/c in the x and pT2 Feynman variables. The Λ production is found to be very similar in the K+p inclusive reaction at 32 GeV/c and in the semi-inclusive reaction at the same energy. The pair production cross section increases significantly in K+p interactions from 16 to 32 GeV/c where it reaches the value . The cross sections for Λ or produced in association with an identified proton are also given and discussed. 相似文献
19.
I.V. Ajinenko Y.A. Belokopitov P.V. Chliapnikov L.N. Gerdyukov V.V. Kniazev A.I. Kurnosenko A.K. Likhoded V.M. Perevoztchikov V.N. Riadovikov A.M. Rybin O.G. Tchikilev V.F. Tchunikhin V.A. Uvarov A.P. Vorobjev 《Nuclear Physics B》1980,176(1):51-60
The inclusive production of and Ξ? hyperons is investigated in K+ p interactions at 32 GeV/c. The production cross sections, 36.4±9 μb for the and 6.5±3 μb for the Ξ?, are rising strongly with energy similarly to and Λ production in K+ p interactions. The are produced preferentially in the forward direction in the c.m.s., while the Ξ? are produced dominantly backwards. The average transverse momenta and 〈pT〉Ξ?=0.58±0.09 GeV/c. 相似文献
20.
We predict for M?+?M?0 the values -3.4 ± 0.8 MeV using the ?-ω mixing and the quark model, respectively. The extracted parameters indicate the necessity of a relativistic treatment of the old mesons. The problem of extrapolating these parameters to the charmed mesons is discussed. Under conservative assumptions, we predict 1.7 ? MD0 ? 2.2 MeV and . 相似文献