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1.
We discuss couplings of scalar gluonium σ on the basis of the low energy theorems of broken chiral symmetry and the anomalous trace of the energy—momentum tensor, implemented using a phenomenological lagrangian. Taking the ITEP value of the gluon consensate as input, we find Γ(σ → ππ) ? 0.6 GeV × (mσ1 GeV)5 and Γ(σ → γγ) ? 90 eV × (mσ1 GeV)5, while mσ is undetermined. These results suggest that if the scalar gluonium mass is above 1 GeV, it is probably unobservably wide, while production in γγ collisions is probably too small to be detectable if mσ < 1.5 GeV. We comment on the observability of J/ψσ + γ and on the relevance of our results to other gluonia.  相似文献   

2.
3.
From the measurement of Be+e? = Γ(ppe+e?)Γpp→total = (3.2 ± 10?7), obtained in an experiment at CERN with antiprotons at rest, a value of the proton electromagnetic form factors at the threshold of the time-like region is derived: |GE| = |GM| = 0.51 ± 0.08 at q2 = -3.52 (GeV/c)2.  相似文献   

4.
We report the first observation of the decay ?′→?π+π?l+l?π+π?. The 7 events seen yield a branching ratio B(?′→+π?)=(19±8)%. A consistent value of B=(26±13)% is obtained from the charged multiplicities of the ?′ and ? decays. Using these values we deduce Γtot(?′)=(31+10?8) keV and Bee(?′)=(1.8±0.5)%. Furthermore we estimate Γ(?′→gg?)=(10±5) keV in agreement with QCD predictions using vector gluons while one would expect 100 keV with scalar gluons.  相似文献   

5.
The radiative decays of Jψ into f/γ, f′γ, ππγ and KKγ have been measured using the double arm spectrometer DASP at DORIS. We find B(J/φ)=(J/φ)/(J/φ→all)=(0.9±0.3)×10?3 to (1.5±0.4)×10?3 depending on the multi- pole mode of the Jψ decay and that B(J/φ→f′γ)B(J/γ→fγ)?13.  相似文献   

6.
The polarization of the f0(1270) and ?0(770) produced in the J/ψ decays into f0γ and ?0π0 are measured in e+e? collisions at 3.1 GeV. A fit to the f0 production and decay angular distributions yields the values A1/A0 = 0.6 ± 0.3 and A2/A0 = 0.3 ?1.6+0.6, where Aλ are the f0 helicity amplitudes. These results are in good agreement with the values predicted from a QCD two-gluon-exchange model. In addition an upper limit of 2.3 × 10?4 is obtained for the J/ψf0(1514) γ decay branching ratio which implies Γ(J/ψfγ)/Γ(J/ψf0γ) ? 0.12 ± 0.05.  相似文献   

7.
The e+e?pp cross section has been measured in the energy interval (1975 ? 2E ? 2250) MeV for |cosθ| < 0.7. The measurement is based on ~ 100 events, thus improving by a factor 3 on the previous existing statistics in this energy interval. The form factor |G|2 is given as a function of energy under the assumption |GE| = |GM|. We also give the first measurement of the differential cross section, averaged over the energy interval, and estimate the ratio GM|/|GE| from it.  相似文献   

8.
We discuss the decays ψ';'→J/ψ+π0 and ψ';'→J/ψ+η. We obtain a reliable, model-independent theoretical prediction for the ratio of the decay rates based only on the QCD lagrangian and certain low-energy theorems. The theoretical formula, apart from kinematical factors, contains only the ratio of the current quark masses, md/mu. Under a standard choice of md/mu theory and experiment are in good agreement with each other.  相似文献   

9.
The predictions of a linear mass mixing model for pseudoscalar and vector mesons, which incorporates the effects of radial excitations, are examined. Several analyses are made fitting in each case to a different experimental value of Γ(ψ →η'γ)Γ(ψ→ηγ) upon which the η-η′ mixing pattern is very sensitive. Predictions for radiative transitions among the mesons and for the ratio of production amplitudes σ?p→η′n)σ?p→ηn) are compared with experiments. Results indicate a preferred value of 3.1 for Γ(ψ→η′γ)Γ(ψ→ηγ).  相似文献   

10.
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.  相似文献   

11.
The decay of J/ψ (3.1) into final states containing no charged particles has been studied experimentally. The partial decay width for the observed neutral decays is (470 ± 160) eV. The decay modes J/ψγη → 3γ and J/ψγη′ → 3γ are identified and the branching ratios
Jψ → γηJψall = (1.3 ±0.4) × 10?3, andJψ → γη′Jψ → γη = 1.8 ±0.8
, are derived. Upper limits for the decay modes J/ψγπ0 and J/ψγγ are given.  相似文献   

12.
The width for decays of the type 1?γ + 0? is evaluated using the two gluon mechanism of QCD. In particular we compute Γ(Ψγ + η′), Γ(Ψγ + η) and Γ(?γ + ηc). The first two are found to be in reasonable agreement with the experimental results, while the latter leads to a branching ratio of 2 × 10?5.  相似文献   

13.
W.K. Theumann 《Physica A》1975,83(1):85-120
The two-point correlation function ? (q, ξ) is calculated in the critical region of momentum space q in terms of a suitable correlation lenght ξ, by means of perturbation expansion to order 1/n, for an n-vector system with long-range interactions decaying as |R/a|?(d + σ), for |R/a| a? 1, where a is the spacing on a d-dimensional lattice, σ < d < 2σ and 0 < σ ? 2 ? ηSR. The calculations are done in zero field for T ? Tc. Explicit expansions for long-range propagators are developed for σ « 1 and for the neighborhood of σ ? 2 ? ηSR, in terms of which a universal, cut-off independent scaling function is obtained over the whole range of x = |q| ξ, and it is shown that the amplitude of the correlation-length dependence of the susceptibility becomes a universal parameter. Both the exponents and the coefficients of the expansion for fixed q as (T ? Tc)Tc→0 are calculated explicitly. The former are shown to require the validity of the operator-product expansion and explicit logarithmic correction terms are obtained for d = d1 = 3σ/2. For these and other dimensionalities, the coefficients are shown to be finite functions of d and σ. The correction to the Ornstein-Zernike form is given explicitly, with non-integer powers of x that have finite coefficients.  相似文献   

14.
The properties of the diffractively excited system observed at low missing mass in the inclusive pp → pX reaction at 303 GeVc are presented. For diffraction excitation with |x| > 0.9, the cross section, σD=(5.6±0.8) mb, the mean charged multiplicity depends on the mass of the diffractive system approximately at 〈nc〉 ≈ 0.6Mx + 2, and the slope of the momentum transfer distribution with |t| < 0.5 GeV2 is 7.5±0.8 GeV?2.  相似文献   

15.
Exclusive decays such as G → ππ are studied in the framework ofperturbative QCD. We discuss the possibility of the constituent gluons' virtualness scaling as the glueball mass MG, which is a picture equivalent to a glueball containing a few slow-moving, heavy gluons. In this case, the decay rate exhibits a pinch singularity which enhances it by a factor of order (MG2/mq2)2 over the dimensional scaling expectation. This singularity is partially suppressed by Sudakov effects which reduce the enhancement factor to (MG2/mq2)2n, where n ? 0.4.  相似文献   

16.
In QCD with massless quarks, the effective potential for the color singlet operator (Fμνa)2 can be constructed by the use of the trace anomaly equation and tells us that magnetic gluon condensation, 〈0|(Fμνa)2|0〉 > 0, occurs. When the method is applied to supersymmetric QCD, however, it gives us a puzzle; the gluons condense with negative energy density, and supersymmetry is broken in a pathological manner with the appearance of a negatively normed Nambu-Goldstone fermion. Spurred on by this observation, we examine in detail the properties of the vacuum for the super (and ordinary) O(N) non-linear σ model in two dimensions for which a similar puzzling situation occurs with regard to the lagrangian condensate. We find, in particular, that (i) the chiral condensate plays a crucial role in resolving the puzzle and that (ii) it is the nature of the response of the lagrangian condensate to the test charge, not the sign or the magnitude of the condensate itself, that determines the phase of the system. Implications of these results for (super) QCD, including an unconventional possibility of “electric” gluon condensation, are discussed.  相似文献   

17.
I present estimates of CP-violating asymmetries in the non-leptonic charmonium two-body B0→ψ(2S0 decay and the same decays of B+→ψ(2S+ and B+→ψ(2S)K+ These estimates are based on QCD and improved QCD factorization approach making use of next-to-leading order (NLO) contributions. The CP-violating asymmetry for B0→ψ(2S0 decay is not available, according to the same calculations, it is expected if it can be measured in the future its value will be Sψ(2S)π0(B0 → ψ(2S0)= 0.662 ± 0.197 and Cψ(2S)π0(B0 → ψ(2S0)= 0.024 ± 0.007.  相似文献   

18.
An n-orbital model describing both elastic impurity scattering and exchange interaction is examined near its instability for itinerant ferromagnetism. At the critical point and at zero temperature, long range spin fluctuations cause anomalous enhancements of the density of states near the Fermi energy with ?(E) - ?(EF) ∝ |E ? EF|14 in three-dimensions (3D) and with ln2|E ? EF| in 2D. An estimation of the conductivity σ(Ω) in a continuum analog model reveals Ω14 -and ln2τ|-corrections in 3D and 2D respectively.  相似文献   

19.
The decay F+π+π0 can proceed via isospin violating mechanisms similarly to ψ′ → Jψπ0. 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.  相似文献   

20.
|η+?| can be rather cleanly determined in e+e?→ K0K0 at the φ-resonance position from the π+π? time-distribution of decays of one of the produced kaons within a suitable angular portion of a hemisphere. Our procedure is better than the existing methods.  相似文献   

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