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1.
The time-dependence of the decay rate of initially pure K0 into the final state (π+ππ0) has been studied in search for the decay kS0→π+ππ0. No evidence is found in a sample of 384 observed events. The ratio of the CP -violating KS0 amplitude and the KL0 amplitude is η+−0 = (0.13−0.20+0.17) + i(0.17−0.26+0.27); the ratio of the CP-conserving KS0 amplitude and the KL0 amplitude is < 0.4. The energy dependence of the K0→π+ππ0 matrix element is found to be a+−0 = −0.31 ± 0.03.  相似文献   

2.
The measurement of correlations between like pions in the inclusive processes a + b → π± + π± + X permits us to study the space-time mechanism of multiple production. Similar measurements for neutrons evaporated from highly excited nuclei give the shape of nuclei and their mean lives; for pions from the resonance decay - the mean resonance life.  相似文献   

3.
Differential cross sections for the reactions 16O(γ, ππ+−)16F16F to the sum of the four lowest lying states in 16F and 16N have been measured as a function of angle for pions with a kinetic energy of 30 MeV. The extracted ratios R = σ(γ, π)/σ(γ, π+), the first ones to discrete final states as a function of angle, are in fair agreement with results obtained for the nucleon. For positive pions the energy dependence of the cross section has been measured at the angles of 45° and 90°. Distorted wave impulse approximation calculations fail to describe the energy dependence.  相似文献   

4.
Data were taken at the energy 2E = 990 MeV to search for multibody events, with the same large solid angle detector which has been used for the measurement of the , ω andφ production by e+e annilations. Assuming a π+ππ0π0 production by the quasi two-body process e+e → → ωπ0 we give the correspondi ng cross section σ(e+e → π+ππ0π0) = (1.1 ± 0.5) 10−32 cm2. Since no events with 3 and 4 charged pions have been observed σ(e+e → π+ππ0π) 1.5 × 10−33 cm2.  相似文献   

5.
The nearly energy independent hadron emitter dimension r, measured in e+e annihilation in the energy range 10 to 91 GeV via the Bose–Einstein correlation of two identical charged pions, is shown to be well accounted for by choosing the hadron jets as independent pion sources. To this end the known normalised factorial cumulant moments dependence on particle sources is adapted to the Bose–Einstein correlation formalism to yield a relation between r and these sources. This approach is also able to account for the measured r values obtained for the Z0 decays into two and three hadron jets. Finally the estimated r value of the hadronic (9.46) decay via three gluons is expected to be higher by about 6 to 11% over that predicted for its one photon hadronic decay mode.  相似文献   

6.
We propose to test CP symmetry in the decay J/ψ→γφφ, for which large data sample exists at BESII, and a data sample of 1010 J/ψ's will be collected with BESIII and CLEO-C program. We suggest some CP asymmetries in this decay mode for CP test. Assuming that CP violation is introduced by the electric- and chromo-dipole moment of charm quark, these CP asymmetries can be predicted by using valence quark models. Our work shows a possible way to get information about the electric- and chromo-dipole moment of charm quark, which is little known. Our results show that with the current data sample of J/ψ, electric- and chromo-dipole moment can be probed at order of 10−13 e cm. In the near future with a 1010 data sample, these moments can be probed at order of 10−14 e cm.  相似文献   

7.
We apply the perturbative chiral quark model to give predictions for the electromagnetic O(p2) low-energy couplings of the ChPT effective Lagrangian that define the electromagnetic mass shifts of nucleons and first-order (e2) radiative corrections to the πN scattering amplitude. We estimate the leading isospin-breaking correction to the strong energy shift of the πp atom in the 1s state, which is relevant for the experiment “Pionic Hydrogen” at PSI.  相似文献   

8.
We present an amplitude analysis of the process πp→π+πn at 15 GeV/c assuming spin and phase coherence of the production amplitude. The bearing of the results on aspects of dipion production phenomenology is discussed.  相似文献   

9.
We study the cross sections for the production of neneural, intermediate mass Higgs boson in the process pptq′φ, pptWφ and ppbZ0φ in the Minimal Supersymmetric Standard Model (φ = H0, h0 and A0) at Supercollider energies. The additional heavy particles (t, W, Z) in the final state can be used for tagging purposes, increasing the signal to background ratio. These reactions are dominated by bg and bg fusion. Their relevance for Higgs particle searches is discussed taking into account the expected efficiencies and purities for b-tagging. We find that, for tan β = 30, the cross sections for ppbZ0φ are larger than 14 pb, over the whole intemediate range of MA0, for A0 and at least one of the other two Higgses. Therefore this reaction is an excellent candidate for the discovery of one or more MSSM Higgs particles.  相似文献   

10.
Cross sections for the production of hypernuclei were measured in the reaction A(K, π) ΛA. on light and heavy nuclear targets, using a separated K beam at the CERN Proton Synchrotron. The pions were detected in the forward direction. The results are compared with cross sections calculated under the assumption that the reaction took place on a single neutron. The good agreement between the measured and the calculated cross sections justifies the use of the (K, π) reaction in order to obtain spectroscopic information on hypernuclei.  相似文献   

11.
Recent work in both lattice and continuum QCD shows that the gauge field is massive. We investigate the bound states of massive gluons with a Schrödinger equation and find M(0++) ≈ 2.3 m, M(0−+) ≈ 2.7 m, M(2++) ≈ 3.2 m, where m is the gluon mass; we expect from this as well as earlier work that m ≈ 500 MeV. These glueballs have widths typical of allowed hadronic decays.  相似文献   

12.
The emission of two photons above 25 MeV energy was observed in the capture of stopped pions by beryllium and carbon with a rate of (1.0 ± 0.1) × 10−5, respectively (1.4 ± 0.2) × 10−5 per capture. These rates are about two to four times greater than various free-nucleon estimates based on the π+→γγ annihilation mechanism alone.  相似文献   

13.
We study the ρ0 and φ decays into π+πγ, π0π0γ and φ into π0ηγ using a chiral unitary approach to deal with the final state interaction of the MM system. The final state interaction modifies only moderately the large momenta tail of the photon spectrum of the ρ0→π+πγ decay. In the case of φ decay the contribution to π+πγ and π0π0γ decay proceeds via kaonic loops and gives a distribution of ππ invariant masses in which the f0(980) resonance shows up with a very distinct peak. The spectrum found for φ→π0π0γ decay agrees with the recent experimental results obtained at Novosibirsk. The branching ratio for φ→π0ηγ, dominated by the a0(980), is also in agreement with recent Novosibirsk results.  相似文献   

14.
In e+e annihilations at SPEAR we have searched for narrow neutral resonances in the eπ and μπ channels for masses between 0.5 GeV/c2 and 1.5 GeV/c2. No evidence for such states has been found. Under standard theoretical assumptions for production cross sections and decay branching ratios of heavy leptons a lower limit of 1.2 GeV/c2 can be set on the mass.  相似文献   

15.
The theoretical mechanisms for the decays ψ′ → ψπ0 and ψ′ → ψη, which violate SU2 and SU3, respectively discussed. It is argued that symmetry breaking in the decay amplitudes may be as important as π0 −η −η′ mixing. The π0 −η mechanism ψ′ → ψν → ψπ0 leads to Γ(ψ′ → ψπ0) = (3.3±1.0) × 10−3 Γ(ψ′ → ψν), but this number may be enhanced by a factor as large as 12 by π0−η′ mixing and isospin violation in the decay amplitude. The related decays ψ → ηγ and ψ → η′γ are also discussed.  相似文献   

16.
We show that an important contribution to subthreshold K production in high energy heavy ion collision is the strangeness exchange reactions Yπ→K---N between the hyperons and pions initially produced in the collision. Estimates are given for the number of K produced via this mechanism and it accounts for a large fraction of the experimental observation.  相似文献   

17.
Fluorescence decay curves for 5,10,15,20-tetrakis(4-sulfonatophenyl)-21H,23H-porphine tetraanion (TPPS4−) have been measured in the absence and presence of the methylviologen dication (MV2+) with various ionic strengths in methanol. In the presence of MV2+ the fluorescence decays can be expressed by a double exponential function, I(t = I1exp(−t1) + I2exp(−t2). The contribution by the faster decay component to the total fluorescence signal increases with increasing MV2+ concentration. The faster decay process is attributed to fluorescence from the excited state of a solvent-separated ion pair (SSIP) formed between TPPS4− and MV2+, and the slower process is attributed to fluorescence from free TPPS4− ions in the solution. Rate constants for the quenching of fluorescence from free TPPS4− by MV2+ (kq) and formation constants for the SSIP (KSSIP) were calculated and both are found to decrease with increasing ionic strength. The decrease in kq and KSSIP values can be interpreted in terms of the shielding of electrostatic attraction between the ions.  相似文献   

18.
The arguments are put forward that the many pion decays ω→2π+π0 and π+π0 provide an ideal test site for testing the predictions of chiral models of the vector meson decays into many pions. Using the approach based on the Weinberg Lagrangian or, in a new language, the Lagrangian of hidden local symmetry added with the term induced by the anomalous Lagrangian of Wess and Zumino, the partial widths of these decays are evaluated, and their excitation curves in e+e annihilation are obtained. The discussed are the perspectives of the experimental study of the decays ω→5π in e+e annihilation and photoproduction.  相似文献   

19.
We calculate the heavy quarkonium production in double pomeron exchange processes in perturbative QCD by using two-gluon exchange model. For the P-wave χJ productions, we find χ1 and χ2 production amplitudes which vanish in the forward scattering limit. We also calculate direct J/ψ()+γ production in the same approach, and these direct contributions are much smaller than the feeddown contributions from the P-wave states.  相似文献   

20.
The differential cross section of the reaction γp→π+n has been measured with the PHOENICS detector at ELSA in Bonn. For the first time this cross section has been determined simultaneously over a large range of photon energies (Eγ = 220−900 MeV) and pion angles (Θc.m.pi = 35°−135°) with a tagged photon facility. The experimental set-up allowed a considerable kinematic overdetermination of the investigated reaction. Accordingly, the background contributions have been suppressed to below 1%. The measured differential cross section is in good agreement with existing data. The comparison with different model calculations is presented.  相似文献   

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