COULOMB EFFECT IN π-NUCLEUS SCATTERING AT LOW ENERGY

The importance of Coulomb effect for π-¹²C, ¹⁶O scatterings is studied at incidentenergy T_π=80, 70, 50, MeV. Results show that the discrepancy between the data andthe calculation that appears in differential cross section for T_π=50 MeV in referenceis not attributed to ignoring Coulomb effect. The Coulomb effect in such energy regionis negligible, except small angle region in the differential cross sections at. T_π=50 MeV.     

THEORY OF （π+,d） REACTION

In this paper the DWBA cross section formula for the（π⁺,d）reaction is deri-ved in the model of one-nucleon absorption of pion,and the differential cross sectionsfor ¹²C（π⁺,d）¹⁰C_g.5.2+reactions are estimated in PWBA.This kind of reaction isregarded as a worthnoting one for the studies of π absorption processes and the nu-clear pair structure.     

π-NUCLEAR DOUBLE CHARGE EXCHANGE REACTION AND NUCLEAR STRUCTURE

Using Glauber's multiple scattering theory, and using coherent fluctuation nuclearmodel, the double charge exchange (DEC) reaction cross sections for πon ¹⁶O and ¹⁸Ohave been calculated. The calculated values of the ratio of σ(¹⁸O(π⁺,π^-)¹⁸Ne)_g.s. toσ(¹⁶O(π⁺,π^-)¹⁶Ne)_g.s. fit the experimental data quite well. Just as predicted by ourcalculation, the angular distribution of ¹⁸O(π⁺,π^-)¹⁸Ne_g.s. in a recent experiment,exhibits an evident dip around 23°.     

S-WAVE πN INTERACTION IN (π+d) REACTION

Based on the two nucleon pion absorption mechanism, the reaction (π⁺d) is studied. The formula of the differential cross section for (π⁺d) reaction is obtained for S-wave πN interaction. A calculation is also performed for ¹²C(π⁺d)¹⁰C(0⁺,2⁺) at the incident energy of 49.3MeV by using the plane wave approximation. The results indicate that the effect of the D-wave component in the deutron wave function is quite important. The antisymmetric space structure of the neutron pair participated in the process is as the important as symmetric one.     

A TWO-NUCLEON MODEL OF THE（p,π-） REACTION

In this paper,we suggest a two-nucleon model of the A（p,π^-） B reaction.Areduced formulation of the reactoin amplitude and a relation between the reactionamplitude and the nuclear structure are given.The differential cross section of ¹³C（p,π^-）¹⁴O_g.s,at E_P=185 MeV is calculated in the plane wave approximation.The results+s can explain the experimental data qualilatively.     

ANALYSIS OF QUASI-△33 DOORWAY STATE MODEL IN π NUCLEUS SCATTERING

Under Quasi-△₃₃ Doorway state model of π nucleus scattering, the differential cross sections and total cross sections of elastic π-⁴He and π-⁴⁰Ca at the different incident energies, (T_x^lab=110, 150, 180, 220, 260 MeV for π-⁴He, T_x^lab=115.5, 163.3, 241.0 MeV for π-⁴⁰Ca) are calculated. The approximate agreement between the theoretical results and experimential data is arrived at.We evaluate further the correction of spin-orbite coupling effects for π-⁴He, and the better agreements with experimential data are obtained.     

Observation of a pp mass threshold enhancement in ψ′→π+π－J/ψ(J/ψ→γpp) decay

The decay channel ψ′→π⁺π^－J/ψ(J/ψ→γpp) is studied using a sample of 1.06×10⁸ ψ′ events collected by the BESIII experiment at BEPCII. A strong enhancement at threshold is observed in the pp invariant mass spectrum. The enhancement can be fitted with an S-wave Breit-Wigner resonance function with a resulting peak mass of M=1861⁺⁶_－13 (stat)⁺⁷_－26 (syst) MeV/c² and a narrow width that is Γ<38 MeV/c² at the 90% confidence level. These results are consistent with published BESII results. These mass and width values do not match with well established mesons.

     

ON THE “DIRECT CHANNEL DIAGRAM” OF THE PRODUCTION OF THE （π+ π-）s S-STATE ATOMS

In this paper we work out the relativistic covariant B-S wave function for the（π⁺ π^-）_s atoms.Some properties of the“direct channel diagram”of the produc-tion the （π⁺ π^-）_s atoms are discussed by calculating the cross-section of the process π⁺ +n→p+（π⁺ π^-）_s with the help of the relativistic covariant wave function and assuming the lowest termin the perturbation expansion series of the quantized composite field theory——the“direct channel diagram”is dominant.Besides this calcuation perhaps presentsa rough estimate for the interesting process μ⁺ +n→（μ⁺ π^-）+p.     

MULTINUCLEON EFFECT IN PION SINGLE CHARGE EXCHANGE REACTION

In the frame of DWBA and by including multinucleon effects in the optical potential and transition matrix elements,we calculate ¹³C(π⁺,π⁰)¹⁹N(IAS) reactions.Angular distribution at 165MeV,forward angle excitation function and integrated cross sections for this reactions are studied.A formula for mass dependence of forward differential cross sections is derived.     

The Spin Effect of Antiproton-Nucleus Inelastic Collison

If the antiproton optical potential is inclusive of the spin orbit interaction term,the A(p,p)A* inelastic scattering not only can excited the normal parity states,but also can excited the abnormal parity states.There are also induced the polarization P_f(θ) at the inelastic scattering.In the framework of DWIA,we derived the inelastic scattering cross section (dσ/dΩ)_f,i,and polarization P_f(θ),and calculated the (dσ/dΩ)_f,i, and P_f(θ) for ¹²C(p,p)¹²C* with 2⁺,3^－ and 1⁺ states at antiproton energies of 46.8 and 179.7MeV.They fited experiment data quite well.Due to the abnormal partity states in the inelastic process have been measured,the spin orbit term can not be neglect.     

Determination of J/ψ Leptonic Branching Fraction Via ψ(2S)→π+π－J/ψ

Two processes ψ(2S)→π⁺π^－J/ψ,J/ψ→1⁺1^－ and J/ψ→anything are carefully studied to get the J/ψ leptonic branching fractions with the ψ(2S)data at BES/BEPC.The results are B(J/ψ→e⁺e^－)=(5.90±0.07±0.16)% and B(J/ψ→μ⁺μ^－)=(5.96 ±0.08±0.16)%,and B_e/B_μ is estimated to be 0.990±0.018±0.024.Assuming B_e=B_μ,the leptonic branching fraction of the J/ψ is B(J/ψ→1⁺1^－)=(5.93±0.05 ± 0. 16 )%.This result is used to estimate the QCD scale factor ∧(nf/MS) and the strong coupling constant α_s.     

APPLICATION OF THE EIKONAL WAVE FUNCTION TO QUASIFREE SCATTERING

In this paper. we have used the Eikonal wave functionφ_E(r)=(2π)^-3/2 exp(ik.r)X(r)whereexp{-i/hv∫_-∞^zV(x,y,z,')dz'}and V=nk/m to investigate the quasifree scattering ⁶Li (p, pd)α with E_p=156 MeV,590MeV and 670 MeV. In V(x, y, z), the nuclear interaction and the Coulomb inte-raction are included. For the case of 156 MeV, the nuclear potential is taken to be the Woods-Saxon type.The result is shown in fig. 1. This result is compared with those obtained by themethod of partial waves. For the cases of 590MeV and 670MeV, a new method is used to describe thenuclear potential, and the results are showh in fig. 3 and fig. 4, respectively.     

THE DIFFICULTY OF THE DECAY τ→πντ AND SPIN 3/2 HEAVY LEPTON

We discuss the suppression of the decay of heavy lepton τ into πv_τ,by assuming that τ and/or v_τ carry spin 3/2. For the case of spin 3/2 T and spin 1/2 v_τ, using the weak current ψ_μ^(τ)(a+b_^γ5)Ψ^(v_τ)we find that the πv_τ decay channel relative to the v_τv_ll^-channel is suppressed 12/5 times, while other decay channels are not changed appreciably. △R=σ（e⁺e^-→τ⁺τ^-）/σ（e⁺e^-→μ⁺μ^-） is also discussed.     

DECAY PROCESSES IN MASSIVE STRATON MODEL OF MESONS

Using the B-S wave functions of mesons in the massive straton model^[1], we discuss their weak decay, electromagnetic decay, and particularly hadronic decay processes. Not only f_π≈f_K, 1^－→l⁺l^－ rate are successfully explained, the predicted widths for various hadronic decays are also in good agreement with experimental data.     

Structure Analysis of the l/η(1440)

By an amplitudes analysis of the KKπ system in the J/ψ radiative decay to the K⁺K^－π^O and the K⁰_SK^±π⁺ final states, we find that there is one 0^－+ resonance (M=1467±3MeV,Γ=89±6MeV) and two 1⁺⁺ resonances (M=1435±3MeV,Γ=59±5MeV and M=1497±2MeV,Γ=44±7MeV), Which are consistent with the η(1440), the f₁(1420), and the f₁(1510).     

Measurement of J/ψ→ηcγ at KEDR

We present a study of the inclusive photon spectra from 5.9 million J/ψ decays collected with the KEDR detector at the VEPP-4M e⁺e^－ collider. We measure the branching fraction of radiative decay J/ψ→η_cγ, η_c width and mass. Our preliminary results are: M(η_c)=2979.4±1.5±1.9 MeV/c², Γ(η_c) = 27.8±5.1±3.3 MeV, B(J/ψ→η_cγ)=(2.34±0.15±0.40)%.

     

π− Production in16O +27Al at 38, 65 and 93 MeV/u

Negative pion production cross-sections are measured at 38, 65 and 93 MeV per nucleon in O + Al reaction. Rough estimations of the total cross sections are given and compared to previous neutral pion data. Double differential cross sections at 93 and 65 MeV/u show enhancement for pions with velocity close to the beam. At variance no effect is observed at 38 MeV, where π^? and π⁰ distributions are identical. Fewπ ⁺ detected at 38 MeV support this result. This indicates that at the lowest incident energy nearly the whole projectile participates in the production reaction.     

TESTING GLUON DISTRIBUTION FUNCTION OF HADRONS IN LARGE PT PROCESS WITH DIRECT PHOTON EMISSION

In this paper we disscuse disscuse the physicsical aspect of cross-section differences Δ_AB^cγ=dσ(AB→cγX)-dσ(AB→cγX) and give the simple rules to select the elementary subprocesses which contribute to cross-section differences.
We bind a way to test the gluon distribution functions of hadrons through the measurement of cross-section difference or combination of cross-section differences in the large P_T process with direct photon emission. Moreover we obtain simple relations between each combination of cross-sections and the corresponding gluon distribution functions of proton, neutron, pion and daon:
G_p⁸(x)/(Δ_pp^hγ－Δ_pp^hγ)=G_n⁸(x)/(Δ_pp^hγ)=G_π⁸(x)/(Δ_π+p^hγ+Δ_π－p^hγ=G_K⁸(x)/(Δ_K+p^hγ+Δ_K－p^hγ)which are expected to be test in experiment.