共查询到20条相似文献,搜索用时 31 毫秒
1.
J. Irion H. Seebrunner M. Barone M.M. Block A. Böhm R. Campanini F. Ceradini D. Dibitonto K.L. Giboni D. Hanna H. Ludwig F. Muller B. Naroska F. Navach M. Nussbaum C. Rubbia D. Schinzel A. Staude R. Voss 《Physics letters. [Part B]》1981,99(6):495-501
Production of charmed particles has been investigated at √s = 63 GeV usi ng the Lampshade Magnet detector triggered by electrons and positrons emitted at 30% from the ISR beam axis. The results of a search for Λc and c signals in the K?pπ+ and K+π? channels are presented. Cross sections for the reactions pp → ΛcX and pp → ΛccX, and upper limits. for pp → DX, are evaluated under various models and compared with other values obtained at the ISR. 相似文献
2.
Takashi Okazaki Seiji Ōkubo Yūichi Hoshino Kanji Fujii 《Physics letters. [Part B]》1979,85(1):107-110
The validity of the assumption that decays into mesons proceed via ω, φ and ?0 poles followed by cascade decays is examined. is well reproduced by using and the B → ωπ helicity structure. The structure of OZI-violating transitions including the electromagnetic contribution is examined, and compared with the data on inclusive decay. 相似文献
3.
U. Gensch L. Becker U. Kriegel M. Walter J. Klugow H. Kirk P. Porth F.A. Triantis R. Barloutaud C. Cochet D. Debegri M.L. Faccini-Turluer C. Lewin Y. Arestov E. Kozlovsky M. Levitsky J. MacNaughton 《Nuclear Physics B》1980,173(1):154-174
Lambda production is studied in K?p interactions at 32 GeV/c. The total Λ cross section is 2.31±0.03 mb. Using the measured Λγ combinations we find that (31±4)% of all Λ's are produced via the Σ0→Λγ decay. About 60% of the Λ's are associated with either a pair; about 40% of the Λ's are produced through the hypercharge annihiltion reaction K?p→Λ+π'a. The two-peak structure of the invariant x distribution can be related to fragmentation processes. The Λ is found to be unpolarized in the target fragmentation region, whereas a transverse polarization is observed for forward produced Λ's. As a function of p⊥, a polarization effect is measured at medium p⊥. 相似文献
4.
D. Drijard H.G. Fischer W. Geist P.G. Innocenti V. Korbel A. Minten A. Norton S. Stein O. Ullaland H.D. Wahl P. Burlaud G. Fontaine P. Frenkiel C. Ghesquière G. Sajot P. Hanke W. Hofmann M. Szeptycka 《Physics letters. [Part B]》1979,85(4):452-457
The production of a Λ+c charmed baryon has been observed in pp collisions at the CERN ISR. A sharp peak at 2.26 GeV/c2 was found in the decay mode Λ+c → p in events triggered with a forward K? meson. Also the decay mode Λ+c → K? Δ++ seems to be present. The estimation of the total cross section for Λ+c production is given. However, the resulting value depends on the assumed form of the differential cross section. In addition, Λ+c production in events triggered by the presence of a direct electron is discussed. 相似文献
5.
J.L. Rosner 《Nuclear Physics B》1984,248(3):503-522
An event of the form e+e? → μ+μ? + (2 jets) recently observed at √s = 43.45 GeV is interpreted as production of a pair of neutral heavy leptons N, each with mass 20.5 ± 1.0 Gev/c2. Two possibilities are explored: (i) the lepton is a wak isodoublet neutrino, produced in pairs by virtual Z0 decay. In this case, one expects ; (ii) the lepton is a “right-handed neutrino”, produced in pairs via a new vector boson Zχ. In this case, in one model, the Zχ must lie between about 50 and 67 GeV/c2. More generally, it must be very weakly coupled to ordinary quarks and leptons in order not to conflict with low-q2 neutral-current data. Suggestions are made for further observation of N pairs and other effects of Zχ in forthcoming e+e? and p collisions. 相似文献
6.
Quark model predictions for K → 2π and D → Kπ decays were investigated in dynamical frameworks based on the separable approximation (SA), current algebra (CA), current algebra modified for the meson moment dependence (CAC) and current algebra with final-state interactions (CAF). Relativistic and non-relativistic quark model predictions were compared. The effective weak hamiltonian was modified by changing the relative strengths of its flavour parts. All these approaches were also applied to hyperon and non-leptonic decays. When using standard QCD enhancement, the best approximation for K → 2π (CAC) works poorly with D → Kπ. The best approximatiob for D→Kπ (CAF) fails in the case of K → 2π. Only CAC with the piece of the hamiltonian quenched might be in agreement with studied weak decays. 相似文献
7.
8.
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
9.
M.J. Corden G.F. Cox A. Dartnell I.R. Kenyon S.W. ONeale K.C.T.O. Sumorok P.M. Watkins 《Nuclear Physics B》1975,84(2):306-322
The mass, width and branching fractions of the Λ(1520) into have been determined using a Λ(1520) sample produced in the reaction K?d→Λ(1520)π?ps at K? -neutron centre-of-mass energies between 1.9 and 2.2 GeV. A Dalitz plot analysis of the Λ0π+π? decay mode shows that there is a substantial Σ(1385)π component. The SU(3) octet-singlet mixing angle for the baryons calculated from the partial widths for the s-wave σ(1385)π decay of the Λ(1520) and Λ(1690) is found to be consistent with that obtained from the d-wave decays of the singlet and octet members, within experimental limits. 相似文献
10.
P.H. Damgaard 《Nuclear Physics B》1983,211(3):435-446
Exclusive two-photon processes involving baryons have been calculated within the framework of perturbative QCD. In particular, the angular dependence of the process is predicted as a function of the universal baryonic distribution amplitudes φ(xi). The overall normalization is then found by a comparison with the process , so that we can present a unique, absolutely normalized QCD prediction for the two-photon processes. We argue that these predictions, based on the decay rate, should be more reliable than those based on baryonic form factors. Presently not enough data exist to give a meaningful differential cross section for the process . Nevertheless, a total cross section has been obtained. Excluding the region close to threshold, quite good agreement between our predictions and experimental data is found. The analysis in this paper is trivially generalized to other baryons as well. 相似文献
11.
Mordechai Bishari 《Annals of Physics》1980,129(2):435-465
The dynamical basis for the validity of the expansion is investigated in the context of QCD in 1 + 1 dimensions. This is carried out by studying the first non-leading corrections in to the mass operator in the space of physical states. The correction to the real part of the mass operator has a direct implication for the convergence of the expansion, since a small effective parameter is identified, where its smallness depends on the dynamical circumstances in a known way. The generated imaginary part of the mass operator provides us with an insight concerning the question of the narrowness of hadronic resonances. In order to have a more realistic contact with our world, we include also effects due to the flavor symmetry group SU(Nf). This allows us to understand better the validity and usefulness of the notions of resonance dominance and (smooth) Regge behavior. We also discuss the expansion with fixed and compare the results with those obtained from Dual Resonance Model. It is remarked that a nonuniformity exists between the limits Nc → ∞, Nf = fixed and Nc → ∞, , which may affect physical quantities. 相似文献
12.
S. Toaff S. Dado J. Goldberg L. Berny G. Alexander O. Benary J. Grunhaus S. Dagan A. Levy D. Lissauer Y. Oren Y. Eisenberg B. Haber U. Karshon D. Revel E.E. Ronat R. Yaari G. Yekutieli 《Nuclear Physics B》1978,146(2):368-380
Cross sections for various channels in 3 prong + V0 final states of K?n interactions are obtained at 8.25 GeV/c. An energy dependence study of the quasi two-body reactions Σ?(1385) + vector meson and ΛB? seem to imply the presence of cuts in the Regge exchange formalism, whereas the reaction Δ(1236) 1 (890) does not require such cuts. Upper limits of 1 and 2 μb are found for the reactions K?n → ΛA1 and K?n → ΛA2. 相似文献
13.
A two-channel separable potential model is given such that the T-matrix is given in the form of a N/D matrix. This model is used to examine the relationships between the three different definitions for a resonance in the two-channel problem, particularly for a 3S1 Λp resonance. In order to obtain a phenomenological hyperon-nucleon (YN) scattering T-matrix in the present model, a least-squares fit is performed to the existing available data for the scattering cross sections and angular distributions at low energies using the s- and p-wave N/D solutions which carry sixteen independent parameters. Several solution sets of potential parameters are found, for which we can obtain good fits to the Λp → Λp, Σ?p → Λn and ΣN → ΣN data, particularly to the cross-section data for these processes. The p-wave contributions are estimated, and particularly the possibility of p-wave YN resonances is pointed out for the solutions for which we do not assume a 31 Λp resonance. 相似文献
14.
We construct a model of mesons as q pairs in the infinite momentum frame. The basic symmetry is spontaneously broken chiral SU2 × SU2. We compute the rates for the decays ? → 2π, σ → 2π, A1 → ?π, A1 → σπ, A2 → ηπ, πN → ηπ, D → ηπ, f → 2π and the coupling constant, g2?ωπ. We find qualitative agreement with the experimental values. The theory is similar to that of Gilman and Harari. 相似文献
15.
We show that at collider energies heavy quarks are dominantly produced by the fragmentation of gluon jets into with Q = c,b. This is because the underlying gg → gg jet cross section exceeds the fusion process by over two orders of magnitude. We compute the perturbative contribution to the gluon fragmentation from 2 → 3 processes such as gg . We point out the observable consequences for single-lepton production and same-opposite charge dileptons. In particular, the observed production of dileptons with large pT and low effective mass is explained. 相似文献
16.
In reactions such as e → anything, N → anything, the final state (neglecting secondary isospin violating decays) is customarily supposed to have isospin zero or one. We show that for such states the average fraction (X) of the energy carried away by neutral pions is bounded by , when I3 = 0 (e.g., for ee, pp, nn) and by , when I3=±1 (e.g., for pn or np). 相似文献
17.
B.L. Ioffe 《Nuclear Physics B》1981,188(2):317-341
The polarization operator of quark currents with baryon quantum numbers is considered in quantum chromodynamics. The non-zero mean vacuum values of the field operator products are taken into account. The sum rules are obtained assuming that in the virtuality region ~1 GeV, among the mean vacuum values violating the chiral invariance, the most important is . Saturating these sum rules by the lowest baryonic states one is able to calculate the masses of the isobar Δ and nucleon N, MΔ = 1.4 GeV, MN = 1 GeV, up to 15% through the known value . The mass splitting in the baryonic decuplet is calculated in first order in the current strange quark mass ms = 150 MeV. Certain results for other baryonic resonances have also been obtained. 相似文献
18.
Peter Minkowski 《Nuclear Physics B》1980,174(1):258-268
The color bond structure of a quark-antiquark system is extended, in the long-range approximation, self-consistently to the baryonic three-quark bond structure for SU(3)c and generally to the N-quark bond structure for SU(N)c. The universal (N-independent) mass square eigenvalues for massless quarks are . 相似文献
19.
In the presence of right-handed currents including , it is emphasized that the dominant parity-violating (-conserving) Hamiltonian for nonleptonic decays of charmed hadrons transforms like of SU(4), and leads to distinctive results especially in D+ → KSπ+, F+ → μ+νμ and D0 → K?e+νe, etc. 相似文献
20.
A detailed study of the electrical resistance, R(T), of a c-axis single crystal of holmium has been made in the vicinity of its Néel point. The results suggest that the critical temperature dependence of is determined by short range correlations for both T → T-N and T → T+N, although long range correlations become important in the paramagnetic state. 相似文献