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 15 毫秒
1.
Duality is applied in a quasi-local form to the SU(4) × SU(4) current two-point functions. Interpolating functions for some of their space-time components are assumed to be given by the free quark model. Mass intervals in the finite energy sum rules are taken to be approximately SU(3) × SU(3) invariant and a linear dependence of the hadronic mass spectrum upon the radial quantum number is assumed. The correct order of magnitude of various meson decay constants is reproduced provided the color gauge group is SU(3). The bare uncharmed quark masses are given by the formulae: mu ≌ MπFπ/Fπ √6 ≌ 40 MeV, ms/mu ≌ 1 = 6. The η-η mixing problem is discussed. Predictions are made for the masses and decay constants of the vector mesons of the first L = 2 level of SU(6) × O(3), as well as for the decay constants of the radially excited pseudoscalar mesons; estimates of corrections to PCAC in Goldberger-Treiman relations are presented. The bare charmed quark mass is found to be of the order of 1.1–1.2 GeV. Some decay constants of charmed mesons are evaluated.  相似文献   

2.
In the presence of right-handed currents including (cs)R, it is emphasized that the dominant parity-violating (-conserving) Hamiltonian for nonleptonic decays of charmed hadrons transforms like 45 + 451 (20″ + 84) 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   

3.
Cross sections for charmed baryon pair production near threshold in e+e? annihilation are calculated using pole-dominated form factors modified to take intoccount continuum effects. When the C0+C0? production cross section is normalized with the help of data for e+e?pX it is found that the total charmed baryon production cross (C0C0, C1C1, C1C11 + C11C1, C11C11) reaches a peak value of approximately 2.7 nb at √s = 5 GeV.  相似文献   

4.
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 ?1.4 ± 1.1 ? MD1+? MD10 ? 0.0 ± 0.6 MeV.  相似文献   

5.
R.L. Thews 《Nuclear Physics B》1977,129(1):135-141
The constraints of duality via FESR's are applied to the processes P+P→P+V, using particles with a new quantum number (charm) as both external and internal (resonance saturation) states. The results are independent of any detailed dynamics or symmetry schemes, as well as independent of coupling strengths. We use the masses of the recently-discovered D and D1 to set the scale. We predict mD7 = 2372 ± 39 MeV, mF = 1938 ± 33 MeV, mF7 = 2500 ± 40 MeV. Thus slopes of Regge trajectories for charmed mesons are predicted to be substantially smaller than those for ordinary mesons.  相似文献   

6.
We show that the symmetric quark model calculation of charmed baryon pair creation in e+e?-annihilation has an incorrect threshold structure. The cc?-pair creation model possesses the correct s-wave threshold behaviour, if the cc?-pair and diquark pair are created in orbital s-waves. We show that the two models become identical for a specific orbital configuration and discuss implications for the relative production rates of ΛcΛccΣccΣc1c1Σcc1c1.  相似文献   

7.
We calculate the production of narrow resonances with even charge conjugation 3PJ=1,2 in e+e? annihilation in the quarkonium and vectordominance models. We give unitarity bounds for Γ(3PJ → e+e?) in terms of Γ(3PJ → γγ) and Γ(3PJ → e+e?). The electromagnetic production dominates through the neutral current at low energies independent of details of the model. For masses above 10 GeV the situation is reversed.  相似文献   

8.
The semileptonic and leptonic decay modes of charmed hadrons produced in e+e? collisions above 4 GeV in the cm have been investigated by selecting events with a single electron plus at least two charged tracks. The electron momentum spectrum peaks near 0.5 GeV/c with few events above 0.7 GeV/c. The spectrum excludes large rates for the decays Deve and Deveπ, but is compatible with DeveK1(892), DeveK or a mixture of both. The semileptonic branching ratio is obtained both by comparing the inclusive electron cross section with the total cross section attributable to charm, and by studying the fraction of events containing a second electron. The semileptonic charm branching ratios obtained are 0.11 ± 0.03 and 0.16 ± 0.06 respectively. A single event with three electrons and hadrons is found, consistent with the estimated background. The 90% confidence upper limit for σ(e+e? → 3e + hadrons) is 0.1 nb.  相似文献   

9.
Quark masses     
In quark gluon theory with very small bare masses, -ψMψ, spontaneous breakdown of chiral symmetry generates sizable masses Mu, Md, Ms, … We find (Mu + Md) /2 ≈ mp/ √6 ≈ 312 MeV, and Ms ≈ 432 MeV. Scalar densities have well determined non-zero vaccum expectations 〈0|ua|0〉 ≡ 〈0|ψ(x) (λa/2)ψ(x)/0〉 ≈ ?π2Ma, i.e〈0? uo/vb0〉 ≈ 8 × 10?3 (GeV)3 at an SU(3) breaking of the vacuum c′ ≡ 〈0|u8|〉/〈0|uo|0〉 ≈ ? 16%  相似文献   

10.
We calculate mass splittings of strange and non-strange baryons in the [56, 0+] and the [70, 1?]. As the most important spin-dependent force we only analyse the hyperfine interaction. The exact treatment of the quark mass breaking shows contributions which have not been considered in similar investigations up to now. Taking mp ? 2 and popular values for the slope of the linear potential a, the strong coupling constant αs and the p-quark mass, we get excellent results for the four mass splittings 〈Σ-Λ〉, 〈Σ1 ? Σ〉, 〈Δ-N〉 and 〈Ξ1 ? Ξ〉 in the [56, 0+]. The structure of mass spectrum in the [70, 1?] is well described, too; the strong SU(3) mixing of Σ and Λ states is seen to be due to the quark mass breaking. Predictions for missing Σ states in the [70, 1?] as as for splittings between charmed baryons can be made.  相似文献   

11.
A statistical model for baryons was suggested leading to an analytical expression for the square modulus ∥ψ(r)∥2 of baryon wavefunctions, which is not only free of constituent quark masses but also devoid of the interaction parameters of the effective linear potential in which a quark moves. Using ∥ψ(r)∥2 as an input the lifetimes of the newly established charmed baryon (Λc+) and the proton were studied and compared with other existing theoretical estimates.  相似文献   

12.
The simplest four-quark SU(2) ? U(1) models with an anomally-free heavy lepton sector can have two charged heavy leptons and one or two neutral leprons. Such models also explain the rise in R (the ratio of hadronic to muon pair production in e+e? collisions). We study some consequences of different choices of leptonic numbers for L1 and L2. In particular, we derive, the leptonic decay width when several final-stae leptons are massive; the cross section for e+e?L1L2 production; the branching ratio for e+e?L2L2e3μ+missing energy.  相似文献   

13.
Hyperfine structure of the (0, 0, 1) - (1, 0, 1) transition of methanol has been investigated by beam absorption and of the (J, 1, 3?) → (J, 1, 3+) transitions for J = 2, 3, and 6 by beam-maser spectroscopy. The best-fit results for the spin-rotation and spin-spin coupling constants CJKτ±(i) and DJKτ±(i), respectively, are in kHz1: C101(1) = 2.4(10), C101(2) = ?0.6(10), D101(1) = ?13.8(9), D101(2) = 7.0(9), C213?(1) = ?5.0(10), C213?(2) = ?5.5(10) and (CJ13?(2) - CJ13+(2)) = 0.98(9).  相似文献   

14.
R.L. Thews 《Nuclear Physics B》1977,129(1):142-156
Energy scale factors ν0 for PP → PP scattering amplitudes are related via the absence of exotic resonances to ratios of tensor to vector coupling strengths. These same ratios are extracted from FESR's for non-exotic reactions. The scale factors obtained are all of the order of 1.0 GeV2or less, independent of quantum numbers. This contradicts the expectations of dual amplitudes in which ν0 = 1/α′, and trajectory slopes are smaller for charmed mesons. Decay widths for tensor mesons are predicted. An observed SU(3) violation for the ratio A2KK/K7Kπ is shown to be consistent with the FESR results. Charmed meson decays are predicted to be factors of 2–3 larger than those predicted by SU(4).  相似文献   

15.
Molecular beam electric resonance spectroscopy has been used to measure the l-type doubling transitions in carbonyl sulfide. Transitions in J = 4 to J = 20 have been observed for the (0220) vibrational state and for J = 1 and J = 2 for the (0310) state. The data has been analyzed to give the v = 2 energy separation EΔ0 - EΣ0 = ?5.7861(2) + 8.36(1) × 10?5 J(J + 1) cm?1, and the vibrational dependence of q to be 86.52(9)(v2 + 1) KHz. The dipole moment of the (0220) vibrational state is 0.6936(3) D.  相似文献   

16.
Molecular constants of the first E 0+ ion-pair state of IBr vapor have been determined using polarization-labeling spectroscopy applied to the sequential transitions E 0+B′ 0+X 0+, while the second f 0+ ion-pair state is reported and characterized for the first time. A least-squares, simultaneous analysis of data for the I79Br and I81Br isotopes gives the following constants (in cm?1) for I79Br:
E state: Te = 39487.32(12), ωe = 119.518(21), ωeξe = 0.2109(12)
,
ωeye = ? 2.34(22) × 10?4, Be = 2.9701(14) × 10?2
,
αe = 5.43(59) × 10?5, and γe = ? 6.8(16) × 10?7
.
F state: Te = 45382.58(17), ωe = 128.805(66), ωeξe = 0.3630(69)
,
ωeye = ? 9.7(22) × 10?4, Be = 3.0073(30) × 10?2, and αe = 8.52(48) × 10?5
. Preliminary data for the first Ω = 1 ion-pair state, accessed in the sequence 1(3P2) ← A(Ω = 1) ← X 0+, indicate that Te is ?30 cm?1 higher in energy than that of the E state.  相似文献   

17.
It is proved that the quantum mechanical Hamiltonian H = Σi=1N (p2 + m2)12 ? κ Σi>j|xi ? xj|?1 for bosons (resp, fermions) is bounded from below if Ncbκ?1 (resp. N ≤ cfκ?32). H is unbounded from below if Ncblκ?1 (resp. N ≥ cflκ?32). The constants cb and cbl (resp. cf and cfl) differ by about a factor 2 (resp. 4).  相似文献   

18.
19.
We calculate the decay rates of the charmed baryon state C0+(2.26) into 25 two body and quasi two body states involving baryons and mesons with JP = 12+, 32+, 0?and 1?. These modes yield a width of Γ = 16.3 × 1012s?1and an inclusive yield of Λ/p ? 40%.  相似文献   

20.
We consider the effects of multiplicity in semileptonic decays of charmed D(1.87) mesons, produced near threshold in e+e? collisions. We calculate the decay distributions from uncorrelated D → (nπ)Kev and resonance dominated DK1ev modes. Recent data from DORIS suggest that modes with two or more final hadrons dominate strongly.  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