中间玻色子理论Ⅱ.超子的非轻子衰变

本文用中间玻色子理论,讨论了超子的非轻子衰变,考虑了各种衰变机构,解释了FMS极点,建立了李氏和则的更广泛的动力学基础,并求得了和实验大致相符的衰变率和不对称系数。     

Evaluation of the rotational temperature of N+2(B2∑+u) in an R.F. discharge at moderate pressure in nitrogen: A comparison of methods

The rotational temperature of the N⁺₂(B²∑⁺_u → X²∑⁺_g) first negative system produced in an r.f. discharge has been evaluated according to various methods and a comparison of the results has been made.     

A constraint from B decay on models with no t quark

We show that if the b quark is assigned to a singlet representation of the weak interaction SU(2) symmetry and if it decays through the usual weak bosons W^± and Z⁰, then neutral current decays occur at such a rate that Λ(B→X?⁺?^?)/Λ(B→X?⁺ν)?0.12, even allowing arbitrarily many quarks with which the b can mix. We discuss the manner in which the experimental exlusion of this inequality would constrain the possibilities for t-free models.     

InclusiveK *'s and∑ *'s production in 360 GeV/cpp interactions using the European hybrid spectrometer

We have studied the inclusive production of strange meson and baryon resonances in 360 GeV/cpp interactions. Cross sections forK ^*+(892) andK ^*?(892) are estimated to be 4.42±0.62 mb and 2.54±0.47 mb respectively and those for∑ ⁺(1385) and∑ ^?(1385) are 0.67±0.11 mb and 0.26±0.07 mb respectively. Longitudinal and transverse momentum distributions forK ^*(892) and Σ(1385) are presented, as well as for their decay productsK ⁰ and Λ. An estimation is given on theK ^*(1430) and∑ ^*(1915) productions.     

Study of the reactionsπ − p→K 0 ∑ 0(1385) andπ − p→K + ∑ −(1385) at 3.95 GeV/c

The reactionsπ ^?p→K ⁰ ∑ ⁰(1385) andπ ^? p→K ⁺ ∑ ^?(1385) are studied at an incident momentum of 3.95 GeV/c using data from a high statistics bubble chamber experiment corresponding to approximately 90 events/μb. The total and differential cross sections and the density matrix elements of the Σ(1385) are presented. The results are compared with those obtained for the related processesπ ^pp→K ⁺ ∑ ⁺(1385) and \(K^ - p \to \pi ^ \mp \sum ^ \pm (1385)\) in this energy range. Evidence is presented for the existence of production mechanisms with exotic exchanges in thet channel.     

K1-Dominance of the Ke3 form factor and Sirlin's relation

We discuss the precise momentum dependence of the K_e3 form factor f₊(t) by studying some of the recent experimental results on K⁰_L → π^± e^? ν decays. The parametrization of f₊(t) based on the assumption of K¹-dominance can considerably improve the agreement of Sirlin's relation with existing data.     

A measurement of the branching ratio for the∑ + →pγ decay

We have measured the weak radiative decay branching ratio (∑ ⁺ →pγ)/(∑ ⁺ →pπ⁰). The experiment was carried out at Brookhaven National Laboratory using a low-energy separatedK ^? beam stopping in liquid hydrogen. The∑ ⁺ was tagged by observing the pion fromK ^? K ⁺ p→∑ ⁺π^? in a range telescope, and the gamma was detected in a segmented NaI detector. The result is (2.81±0.39 _?0.43 ^+0.21 )×10^?3, which is consistent with previous measurements. This corresponds to a branching ratio for (∑ ⁺ →pγ)/(∑ ⁺ → all) of (1.45±0.20 _?0.22 ^+0.11 )×10^?3, where the quoted errors are statistical and systematic, respectively. A total of 408 signal events were observed, doubling the previous world total.     

Inclusive∑ ± production in\bar pp interactions at 12 GeV/c

Inclusive production of∑ ^±(1385) resonances is studied in \(\bar pp\) interactions at 12 GeV/c. The cross sections for∑ ⁺(1385)+cc and∑ ^? are determined to be 251±38 μb and 123±30 μb, respectively. The inclusive spectra are presented as a function of Feynman x, c.m. rapidity and the squared transverse momentump _T ² . Significant differences with the correspondingpp data are found in the longitudinal momentum distributions. The qualitative features of the production can be explained by simple quark ideas.     

A study of the reactions π+p→ K+∑+ and K−p→π−∑+ at 10 GeV/c

For the first time, the reactions π⁺p→K⁺∑⁺ and K^?p→π^?∑⁺ have been studied in the same apparatus. This has been done at an adequately high momentum (10.1 GeV/c) to allow a check of the prediction of exchange degeneracy, that the differential cross sections should be converging at high energy. We have measured the cross section for momentum transfers t between t_min and t = ?0.3 (GeV/c)². We find that for both reactions the differential cross section shows an exponential fall, with no deviations right in to t =t_min (where some other experiments have shown a dip in the cross section). Furthermore, we find the magnitude of the differential cross sections to be closely similar at t = 0, with a ratio

$\text{R=}\text{(}\text{d}\text{σ}\text{d}\text{t)}{}_{\mathrm{t=0}}\text{(}\text{K}{}^{\mathrm{?}}\text{p}\text{→π}{}^{\mathrm{?}}\text{∑}{}^{\mathrm{+}}\text{)}\text{(}\text{d}\text{σ}\text{d}\text{t)}{}_{\mathrm{t=0}}\text{(π}{}^{\mathrm{+}}\text{p}\text{→}\text{K}{}^{\mathrm{+}}\text{∑}{}^{\mathrm{+}}$

However, the slope for the positive reaction is about 19% steeper than that for the negative reaction.     

Winkelverteilungen elastisch an Edelgas-Atomstrahlen gestreuter Elektronen; Spinpolarisation eines an Argon gestreuten 40 eV-Elektronenstrahls

Various non-leptonic decay modes of baryons are calculated in a simple quark model. Form factors for various matrix elements are taken both from experiment and the quark model. Additionally theK→2π andK→3π decay modes are computed in the same model. The theory has theΔ I=1/2 rule and static SU⁶ built-in. A relation between the∑ ⁺→N ⁺ π ⁺ decay, not calculable in the model, and theK→3π decay is given via an effective six quark interaction. Agreement with experiment is order of magnitude for the baryonic decays and worse for theK decays.     

Franck-Condon factors and R-centroids for the A1∑+-X1∑+ and B3Π(0+)−X1∑+ band system of 63Cu1H and 63Cu2H

The recently reported new RKR potential energy curves for the X¹∑⁺, A¹∑⁺, and B³Π(0⁺) electronic states of ⁶³Cu¹H and ⁶³Cu²H are used to calculate Franck-Condon factors and r-centroids for the A?X and B?X band systems for 0≤v″≤20, 0≤v′≤10 and J = 0, 30, 40. The r-centroid approximation is verified and a physical interpretation of the r-centroid is discussed.     

Inclusive Λ production in\bar p p interactions at 3.0, 3.5, 4.0 and 4.5 GeV/c

Inclusive Λ production in \(\bar p\) p interactions at 3.0, 3.5, 4.0 and 4.5 GeV/c is studied. The inclusive cross sections for Λ and Λ \(\bar \Lambda \) production are measured. The differential cross sections as functions ofx, y, andP _T ² are given for each beam momentum. It is found that the contribution of indirect production of Λ from resonance decay is considerably enhanced in the region of higher missing mass against Λ. The negative polarization is observed for Λ with largerP _T and lower missing mass, and is found to be mainly from two body reactions. Inclusive cross sections for∑ ^±(1385) production and the fraction of indirect Λ from∑ ^±(1385) decay are measured. The ratio between the cross sections for∑ ⁺(1385) and∑ ^?(1385) productions is found to be almost constant for wide range of beam momenta.     

Baryonic resonance production in\bar p p interactions at 32 GeV/c

The inclusive production of (1232) in \(\bar p\) p interactions at 32 GeV/c is studied using data collected in a bubble chamber experiment with a statistics of ～0.7 events/μb. Total and topological cross sections are evaluated and compared to existing data at other energies. The distributions of reduced longitudinal momentum and rapidity show evidence for some central production. Total cross sections for (∑ ⁺(1385)+cc) and (∑ ^?(1385)+cc) are also presented.     

Phenomenology of Σ+→pℓ+ℓ− and the structure of the weak non-leptonic Hamiltonian

The problem of the radiative non-leptonic weak baryon decays is reviewed in light of the new experimental findings. With the aim of exploring the structure of the weak non-leptonic Hamiltonian, we present a detailed phenomenological analysis of Σ⁺→p?⁺?^? transitions. Lower and upper limits for rates derivable with standard physics are determined as Γ(Σ⁺→pe ⁺ e ^?)/Σ⁺→pγ)≧7.2×10^?3 and 1/1210? Γ(Σ⁺→pe ⁺ e ⁺)/Γ(Σ⁺→pe ⁺ e ^?)?1/120. From existing data on Σ⁺→pe ⁺ e ^? we obtain limits on the values of the charge radius form factors |c ₁/b ₁|?5;|c ₂/b ₁|? 10, where the magnetic form factor is given by the Σ⁺→dγ, decay asb ₁(0)= 6.9±0.9 MeV. The short distance contribution of the QCD corrected single quarks→dλ transition is shown not to play a dominant role in these decays.     

InclusiveΔ ++ (1232) and∑ ± (1385) production inK − p interactions at 32 GeV/c

We have studied inclusiveΔ ⁺⁺ (1232),∑ ⁺ (1385), and∑ ^? (1385) baryon resonance production inK ^? p interactions at 32 GeV/c. The inclusive and topological cross sections are estimated and compared with published results at lower energies. No energy variation of the cross section is observed forΔ ⁺⁺ (1232) and only a slight decrease is seen in case of∑ ^± (1385). The production properties are investigated through longitudinal and transverse momentum distributions. TheΔ ⁺⁺ (1232) is dominantly produced in the target fragmentation region. The∑ ⁺ (1385) is produced both in the target fragmentation region and in the central region, while the∑ ^? (1385) is predominantly produced in the central region. About 20% of the final state protons are produced via aΔ ⁺⁺ (1232) decay and about 25% of the Λ produced come from the decay of∑ ⁺ (1385) and∑ ^? (1385).     

Isospin violation in the standard model and the decay F+ → π+π0

The decay F⁺ → π⁺π⁰ can proceed via isospin violating mechanisms similarly to $\text{ψ′ →}\text{J}\text{ψπ}{}^0$. I estimate that π⁰-η-′ mixing together with symmetry breaking in the amplitude lead to Γ(F⁺ → π⁺π⁰)/Γ(F⁺ → π⁺η) = (2.2 ± 0.7) × 10^?3 or (1.0 ± 0.3) × 10^?3, if annihilation processes dominate nonleptonic charmed meson decays. These values correspond to different assumptions for two-meson production in F decays.     

The chiral-bag model andK→2π decays

Nonleptonic kaon decays (K→2π) have been analyzed using the chrial-bag model. This continues the research of nonleptonic decays by the authors (Ref. [7] below). The results obtained are in qualitative agreement with those based on QCD-duality. the decay amplitudeA(K ⁺→π⁺π⁰) (ΔI=3/2) can be explained while the ΔI=1/2 decay amplitudes are 4 to 5 times smaller then the observed values. The ratio ofK ⁰ decay amplitudes ξ=|A(K ⁰→π⁺π^?)/A(K ⁰→π⁰π⁰| is larger than one, as it is experimentally. This is an improvement in comparison with MIT-bag model, where ζ was always smaller than one, even if ΔI=1/2 pieces in the theoretical expressions were enhanced.     

Contributions of parity-violating baryon matrix elements to nonleptonic charmed-baryon decays

Baryon-baryon matrix elements of the parity-violating charm-changing weak Hamiltonian are calculated using the MIT bag model. The changes in thes- andp-wave amplitudes of Cabibbo-favored nonleptonic decays of charmed baryons due to these parity-violating baryon transition elements are in general not substantially significant. However, they can overwhelm or be comparable to the contributions arising from the parity-conserving matrix elements for some reactions such as thes-wave amplitude ofΛ _c ⁺ →Ξ ⁰ K ⁺ and Δ⁺⁺ K ^? and thep-wave amplitude ofΛ _c ⁺ →∑ ⁰π⁺.     

Theoretical evidence for di-molecular rotational behaviour in the hypernuclei ∑ 8 Li and ∑ 8 Be

We have performed microscopic cluster studies of light∑-hypernuclei based on effective nucleon-nucleon and two different sigma-nucleon interactions. Our calculation confirms a bound 0⁺ state in _∑ ⁴ He and _∑ ⁴ H, but reveals no evidence for levels in other partial waves. We have investigated the _∑ ⁸ Li and _∑ ⁸ Be hypernuclei in a microscopic 3-cluster approach. For both hypernuclei, our calculation shows that the lowest levels in the partial wavesJ=0–4 are bound or quasibound states of collective nature and show a strong α _∑ ⁴ H and α + _∑ ⁴ He clustering. These levels form a sequence of states which can be well interpreted as arising from a rotatingα+ _∑ ⁴ H orα+ _∑ ⁴ He di-molecule. Our results are compared to those of similar studies for lightΛ-hypernuclei which do not show evidence for this kind of collective degrees of freedom.