共查询到20条相似文献,搜索用时 31 毫秒
1.
It is shown that in the chiral limit, the enhancement of the transitions for mesons is explained by the large size of non-perturbative QCD matrix elements. For we obtain ∣M(KS0 → 2π0) ∣ =(5.2±0.6) × 10?7mK in excellent agreement with experiment. 相似文献
2.
H. Laven G. Otter G. Rudolph R. Klein H.J. Schreiber D.J. Kocher D.R.O. Morrison P. Schmid K.L. Wernhard R.M. Eason T.C. Bacon K.W.J. Barnham P.J. Dornan B. Pollock J. Macnaughton M. Markytan 《Nuclear Physics B》1977,127(1):43-56
The reactions (1) K?p → K+K?Λ and (2) have been studied on samples of 109 and 64 events, respectively, at 10 GeV/c and 125 and 69 events at 16 GeV/c, reasonably free from contaminations. The investigation of the first reaction uses also 84 events of the final state at 10 GeV/c. Analysis of the Van Hove plots indicates that the K+K?Λ and final states are produced by two main mechanisms: (i) a ΔQ = 0 process, with a strong diffractive component near threshold, involving the dissociations p → K+Λ in reaction (1) and in reaction (2) and (ii) a ΔQ = 1 process involving hypercharge exchange, and producing K+K? and systems in reactions (1) and (2), respectively, recoiling off the Λ. With increasing energy, this hypercharge exchange process decreases slowly when K+K? is produced, but fast where the production of , violating the Zweig rule, occurs. 相似文献
3.
Yu.M. Antipov G. Ascoli R. Baud R. Busnello G. Damgaard M.N. Kienzle-Focacci W. Kienzle R. Klanner L.G. Landsberg A.A. Lebedev C. Lechanoine P. Lecomte M. Martin V.N. Roinishvili R.D. Sard A. Snyder F.A. Yotch 《Nuclear Physics B》1975,99(2):189-210
The reaction has been studied at 25 and 40 GeV/c at the Serpukhov proton synchroton using the CERN-IHEP spectrometer. The differential cross section has been determined as a function of four-momentum transfer to the proton (0.05–0.30 (GeV/c)2) and mass (up to 2.2 and 2.6 GeV/c2). At both energies there is a broad low-mass maximum with an enhancement at 1.6–1.8 GeV/c2. The cross section in a given mass band falls rapidly with |t|, with an exponential slope that decreases with increasing mass. In both the background and the 1.7 GeV/c2 peak there is a strong component. Possible spin-parity (JP) contributions to it are discussed. Throughout the range 1.5–2.2 GeV there is at least one state of and there is interference between states of opposite P, |ΔJ| ? 1. At the peak there is a component. There are striking parallels between this reaction and the boson reactions π?p→π?π?π+p and K? → K?π?π+p. 相似文献
4.
Measurements have been made of some parameters of the second and sixth states in 17F. For the second state, the resonance energy was found to be Ep = 12.707 ± 0.001 MeV (En = 12.550±0.001 MeV), which agrees with and improves on the accuracy of earlier work. For the sixth state, at Ep = 14.435 MeV, the γ-decay was determined to be predominantly γ0 with a branch to the first excited state of Γ(γ1)/Γ(γ0) ≦ 0.14. Together with other work, this determines Jπ to be . The capture strength is found to be (2J + 1)ΓpΓγ/Γ = 11.4 ± 2.6 eV. 相似文献
5.
A partial-wave analysis has been carried out on the reaction K?p → K?Δ+(1230) → → K?pπ0 in the centre of mass energy region 1915–2170 MeV. The ∑(2030) is observed with an amplitude at resonance of 0.16 ± 0.03. Strong formation of the is also indicated. 相似文献
6.
S. Al-Harran J. Amirzadeh M. Baubillier I.J. Bloodworth G.J. Bossen A. Burns J.N. Carney G.F. Cox U. Dore Ph. Gavillet J.B. Kinson K. Knudson F. Levy P.F. Loverre H. McCann M. Macdermott P.J. Negus B.Y. Oh R. Zitoun 《Physics letters. [Part B]》1981,101(5):357-360
In a high statistics bubble chamber experiment on K?p interactions at 8.25 , the study of the reaction K?p → KKΛ provides evidence for an enhancement in the KK system with a mass of (1850 ± 10) MeV and a width of (80?30+40) MeV. Its possible identification with the missing isosinglet of the 3? nonet is discussed. A K1 decay mode is also observed. 相似文献
7.
L. Baksay A. Boehm H. Foeth A. Staude W. Lockman M. Medinnis T. Meyer J. Rander P. Schlein T. Trippe R. Webb R. Ellis B. Naroska P. Strolin 《Physics letters. [Part B]》1975,53(5):484-488
In a single-arm magnetic spectrometer experiment at the CERN Intersecting Storage Rings (ISR), a prominent diffractive enhancement is observed for inclusive production of (pπ+π?) systems near x ~ 1 at √s = 53 and 35 GeV. In testing limiting fragmentation and scaling for this system, inclusive pπ+π? diffractive excitation into a fixed invariant mass range is found to possess a cross-section independent of s to within (3 ± 5)%. The main component in the (pπ+π?) system is Δ(1236)π, with a charge structure compatible with the break-up of an isotopic spin system. 相似文献
8.
M.J. Corden J.D. Dowell D. Eastwood J. Garvey R.J. Homer M. Jobes I.R. Kenyon T. McMahon R.J. Vallance P.M. Watkins J.A. Wilson J. Gago M. Jung P. Sonderegger D. Treille P.L. Woodworth V. Eckardt J. Fent K.C.T.O. Sumorok 《Physics letters. [Part B]》1977,68(1):96-100
Measurements have been made of relative production cross sections of the by π±, K±, p and p? at 39.5 GeV/c incident on copper. production rates from π?, K? and p? are similar. The relative particle/anti-particle production cross sections for x>0 are , σ(K+)/σ(K?)=(0.85±0.5) and . The small p/p? cross section ratio disagrees with models of J/ψ production by gluon amalgamation. 相似文献
9.
The reaction has been studied in a kinematically complete experiment using a tensor-polarized deuteron beam to investigate the isospin-forbidden pn final-state interaction. A clear dependence of the cross section near Epn = 0 on the spin state of the incoming deuterons has been found as expected if the bumps observed by several authors at small pn relative energies are indeed due to the isospin-forbidden proton-neutron FSI in the 1S0, T = 1 state. 相似文献
10.
A.A. Carter 《Physics letters. [Part B]》1977,67(1):122-124
We describe a method for examining the differential cross section zeros for the process spin . This is illustrated using the reaction , where three dominant meson spin states are shown to exist in the mass range 2020 to 2580 MeV/c2. 相似文献
11.
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
12.
R. Barloutaud A. Borg F. Brun D. Denegri C. Louedec F. Pierre M. Spiro B. Drevillon B. Chaurand G. Labrosse R. Lestienne D. Linglin R.A. Salmeron T.P. Shah K. Paler R.J. Miller J.J. Phelan 《Nuclear Physics B》1973,59(2):374-411
We have studied the system in the 14.3 GeV/c reactions K?p → K?π+π?p, . The data have been obtained from a 500 000 picture exposure of the CERN 2m HBC. The first two final states are dominated by Q-production in the Kππ system; there is also an L-signal at M (Kππ) ~ 1.75 GeV. The reaction cross sections are compared to K?p data at other energies. We discuss the Kππ mass dependence of the diffractive production slope. Evidence is presented for a Q?p versus Q+p differential cross section cross-over around |t| = 0.17 GeV2. A t-channel isospin analysis for the channels in the Q-region shows that the I = 1 exchange amplitude is of the dominant I = 0 exchange amplitude. The Kππ decay distributions indicate a predominant JP = 1+ state in the Q-region, and an important JP = 2? contribution in the L-region. We find neither s-channel nor t-channel helicity conservation at the meson vertex in the Q- or L-regions. The Kπ angular correlation moments within the Kππ diffractive system are characteristic of Kπ elastic scattering, suggesting a π-exchange Deck-type production mechanism. There is evidence for a Kf0 and κπ contribution (where κ is the JP(Kπ) = 0+ state) to the diffractive Kππ system. A fit to the Dalitz-plot distributions for the Q-re gion indicates that the ratio of decay amplitudes decreases with increasing Kππ mass. 相似文献
13.
A.A. Carter 《Nuclear Physics B》1978,141(4):467-476
The differential cross sections for provide new evidence for mesons with masses between 2.1 and 2.5 GeV/c2. The zeros of the cross sections suggest the existence of JP = 3? states with both I = 1 and I = 0 at masses between 2.1 and 2.18 GeV/c2. The results also support a JP = 4+ state near 2.34 GeV and are consistent with 5? states in both I = 1 and I = 0 close to 2.5 GeV. This analysis confirms the I = 1 3?, 5? and I = 0 4+ states seen previously in and is in agreement with the existing data for the non-annihilation processes. 相似文献
14.
Z. Strachman H. Braun J.P. Gerber G. Maurer A. Michalon B. Schiby R. Strub 《Nuclear Physics B》1975,98(1):120-136
A new approach to the t-channel isospin analysis of ZN → Z′(Nπ) reactions is presented. This approach, useful for when only five independent sets of data are availables, is used to analyse data of reactions obtained in a experiment at experiment at 5.5 GeV/c. the t behaviour of the different isospin exchange amplitudes, suggests their exchange mechanism production. The mass spectrum, MπN, of the contributions produced by exchanged isospin Iex = 1, shows enhancements corresponding to N(1490) N(1670) and Δ(1230) isobars, while the mass spectrum for Iex = 0 presents only a large bump at ~1350 MeV commonly identified as N1(1400). 相似文献
15.
W. Braunschweig H.-U. Martyn H.G. Sander D. Schmitz W. Sturm W. Wallraff K. Berkelman D. Cords R. Felst E. Gadermann B. Gittelman H. Hultschig P. Joos W. Koch U. Kötz H. Krehbiel D. Kreinick W.A. McNeely S. Yamada 《Physics letters. [Part B]》1976,63(4):487-490
Branching ratios have been determined for the decays of and ψ ′ into π+π?, K+K?, , π±?? and . Results on a search for other two body decays of and ψ′ are given. Also presented are values for the π and K from factors at . 相似文献
16.
The magnetic moments of the 12+ isomers in 192, 196, 198, 200, 206Pb and of the isomer in 205Pb have been measured using the PAD technique. The results for the g-factors are: g(192) = ?0.173(2), g(196) = ?0.1600(15), g(198) = ?0.1552(15), g(200) = ?0.1512(15), g(206) = ?0.1496(18), and g(205) = ?0.148(5). As all states have a rather pure configuration, the values reflect directly the orbital. They show a decrease towards the more neutron-deficient isotopes attributed to the reduced core polarisation as a result of decreasing occupation of the neutron shell. The measured systematics are discussed regarding core polarisation, mesonic corrections, and small admixtures of core-excited states to the wave function. 相似文献
17.
Excitation functions of the capture reaction 12C(p, γ0)13N have been obtained at θγ = 0° and 90° and Ep = 150–2500 keV. The results can be explained if a direct radiative capture process, E1(s and d → p), to the ground state in 13N is included in the analysis in addition to the two well-known resonances in this beam energy range and 1699 . The direct capture component is enhanced through interference effects with the two resonance amplitudes. From the observed direct capture cross section, a spectroscopic factor of C2S(l = 1) = 0.49 ± 0.15 has been deduced for the ground state in 13N. Excitation functions for the reaction have been obtained at θγ = 0° and 90° and Ep = 610–2700 keV. Away from the 1699 keV resonance the capture γ-ray yield is dominated by the direct capture process E1 (p → s) to the unbound state. Above Ep = 1 MeV, the observed excitation functions are well reproduced by the direct capture theory to unbound states (bremsstrahlung theory). Below Ep = 1 MeV, i.e., Ep → 457 keV, the theory diverges in contrast to observation. This discrepancy is well known in bremsstrahlung theory as the “infrared problem”. From the observed direct capture cross sections at , a spectroscopic factor of C2S(l = 0) = 1.02 ± 0.15 has been found for the unbound state. A search for direct capture transitions to the and unbound states resulted in upper limits of C2S(l = 1) ≦ 0.5 and C2S(l = 2) ? 1.0, respectively. The results are compared with available stripping data as well as shell-model calculations. The astrophysical aspect of the 12C(p, γ0)13N reaction also is discussed. 相似文献
18.
C.V.K. Baba D.B. Fossan T. Faestermann F. Feilitzsch M.R. Maier P. Raghavan R.S. Raghavan C. Signorini 《Nuclear Physics A》1976,257(1):135-143
Lifetime and g-factor measurements have been made with pulsed beam-γ time-differential techniques using the 89Y(α, 2n)91Nb and 88Sr(α, n)91Zr reactions. A mean lifetime τ = 14.4 ± 0.5 nsec and a g-factor of 1.26 ± 0.04 were obtained for the 1985 keV level in 91Nb and τ = 41.9 ± 1.2 nsec and g = 0.70 ± 0.01 were obtained for the 2288 keV level in 91Zr. These results are compared to theoretical calculations for and configurations in 91Nb and 91Zr, respectively. 相似文献
19.
The deviations from the exponential decay law of the states of the Dirac hydrogen atom with respect to the transition are numerically estimated. We find |a0(t) ? exp(?λt)|?2.5 × 10?4 for all t, where a0(t) is the “exact” decay amplitude and λ is a complex constant such that (2Re λ)?1 is the “natural lifetime” of the states with respect to the spontaneous transition to . 相似文献
20.
T.G.M. Kleinpenning 《Journal of Physics and Chemistry of Solids》1976,37(10):925-928
Electrical resistivity, thermoelectric power and current noise were measured on Li-doped MnO single crystals in the temperature range from 300 to 1000 K. Below 700 K the crystals are p-type and the activation energy of the resistivity is 0.75 eV. Around 700 K the activation energy changes from 0.75 to 1.25 eV owing to a change from p- to n-type conduction. The depth of the Li acceptor is found to be 0.65 eV. From resistivity and thermoelectric power data it is concluded that the bandgap in first approximation can be written as Es(T) = Eo ? γT between 750 and 1000 K, with Eo = 1.9 eV and γ = 6 × 10?4 eV/K. The current noise spectra show noise. The magnitude of the noise is strongly temperature dependent. From the noise data it is deduced that Eo = 2.2 eV and γ = 10?3 eV/K in the temperature range 430–700 K. 相似文献