Quasiclassical teheory of the reaction scattering AB + CD → AC + BD

A quantum-mechanical, three-dimensional, quasiclassical theory is developed for the effective cross section of the chemical reaction AB + CD AC + BD. The quasiclassical approximation is used on the basis of the Born formula for the differential effective cross section. The steady-phase method is used to calculate the integrals appearing in the formula for the differential effective cross section. An analytic solution of the problem is found. The formulas obtained are convenient for use in performing numerical calculations.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 57–62, February, 1982.     

Effect of the Λ n interaction on the cross section of the reaction γd → K+Λ n

Taking into account the n interaction, a nonrelativistic graphical technique is used to calculate the differential cross section of the reaction d K⁺ n as a function of photon energy, K⁺-momentum, and angle of emission of the K⁺. The kinematic region in which variation of the n-scattering parameters gives the most noticeable effect is separated out.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 104–106, August, 1978.The author thanks G. M. Radutskii and V. A. Filimonov for many useful discussions.     

Model-independent analysis of the differential cross section for the reaction n+d→π0+t at medium energies

Experimental values of the differential cross section for the reactionn+d→π ⁰+t at large angles (θ?50°) in the neutron energy range 460–560 MeV and the known values of the coupling constants \(G_{nn\pi ^O }^2 \) andG _tdn ² are used to predictdσ/dΩ at smaller angles. The method is based on the use of general analytic properties of the differential cross section in the cosgq-plane.     

The reaction e− + p → Λ + ν and the contributions of the individual form factors to the differential cross section

We calculate the differential cross section for the weak, strangeness changing, electron scattering process, e⁻ + p → Λ + ν, for incoming electron energies of 0.5, 1.0, 2.0, 4.0, and 6.0 GeV. We obtain as well contributions of the individual form factors to the differential cross sections. We find that the differential cross sections peak as the maximal scattering angle for the Λ is approached and that the peak height increases as the electron energy is increased. The behavior of the differential cross section near the maximal angle is discussed as is the possibility of observing this reaction in a facility such as TJNAF.     

Λ b →Λ c +a 1 decay in the heavy quark effective theory

Using the heavy quark approximation, we have studied the nonleptonic decay mode Λ _b →Λ _c a ₁. We have included nonfactorizable contributions as well as factorizable ones in our analysis. The estimated branching ratio for this process is (1.4±0.1)% and the asymmetry parameter α found to be −0.8.     

Sensitivity of cross section andT 20 to secondary interactions in the reaction indp → ppn at medium energies

Secondary effects in deuteron breakup reactions are reexamined for the process¹ H(d, p) pn with a proton detected at 0° and for the process¹ H (d, pp)n with two fast forward moving protons fixed at the beam line. Sensitivity of the cross section and the tensor asymmetryT ₂₀ to the double-scattering and final-state-interaction corrections is demonstrated. The nonrelativistic method used here incorporates both the energy-conserving and the principal-value part of the free nucleon propagator. The calculations are compared with the inclusive experimental data¹ H(d, p)X at the 1.25 and 2.1 GeV deuteron kinetic energy.The author would like to express his thanks to Prof. B. Tecoult for valuable ideas stimulating this work and Yu.Panebratsev and A. Litvinenko for many helpful discussions. For ideas and advice concerning Sect. 4, I thank to G. Lykasov and S. Shimansky.     

Investigation of the radiative capture reaction t + α → 7Li + γ in the algebraic version of the resonating group method

The radiative capture reaction t + α → ⁷Li + γ is investigated in the framework of the algebraic version of the resonating group method at low energies. The Hasegawa-Nagata nucleon-nucleon potential is used in calculations. The lowest compatible with the Pauli exclusion principle wave functions of a translationally invariant shell model are adopted as the internal wave functions for α and t clusters. The obtained results are in reasonable agreement with the experimental data.     

Fluctuation-dominated kinetics in the a+b→0 reaction between immobile particles

We consider the accumulation of immobile particles landing on a one-dimensional lattice and annihilating via the A + B 0 bimolecular reaction. Here we focus on short-range interactions with cutoff. We investigate through computer simulations both the kinetics of the particles' accumulation and also their spatial distribution. The relation between the exponents describing the growth of the particles' concentration and the correlation length of their distribution shows that the kinetics of accumulation is fluctuation-dominated.This work is dedicated to Prof. George H. Weiss.     

Measurement of the cross section for the e + e ? → ωπ0 → π0π0γ process in the energy range of 1.1–1.9 GeV

The cross section for the e ⁺ e ^? ?? ???⁰ ?? ??⁰??⁰?? process has been measured in the energy range of 1.1?C1.9 GeV. The measurement has been made with the Spherical Neutral Detector at the VEPP-2000 e ⁺ e ^? collider. The data in the energy range of 1.1?C1.4 GeV are in agreement with the earlier measurements with the SND and CMD-2 detectors. The cross section has also been measured above 1.4 GeV.     

A model of turbulent mixing in the A+B→0 reaction

The diffusion limited reaction A+B0 in sufficiently low dimensions results in macroscopically self-regregated systems with anomalous reaction rate laws. When the chemical mixture is embedded in a fluctuating velocity field having statistics mimicking turbulent diffusion the effects of spatial inhomogeneities are washed out and the classical global reaction rate laws in three dimensions result.     

Measurements of a partial cross section for the reaction 58Ni(n, γ0)59Ni

The partial cross section for radiative neutron capture accompanied by gamma transitions to the ground state of the ⁵⁹Ni nucleus was measured as a function of energy by a new neutron-spectrometry method that employed the shift of a primary gamma transition in response to a change in the energy of the captured neutron. The reaction ⁷Li(p, n)⁷Be was used as source of neutrons for the present measurements. The protons that induced this reaction were accelerated by a Van de Graaff electrostatic generator to energies exceeding the reaction threshold by 60 keV, in which case an appropriate geometry of the experiment permitted irradiation of the sample under study with neutrons whose energy ranged between 10 and 120 keV. The partial widths of some resonances and radiative strength function for hard primary M1 gamma transitions were determined in addition to the above cross sections.     

Production of a0 +-mesons in the reaction pp↦da0 +

We investigate the reaction pp↦da ₀ ⁺ at COSY and SIS energies together with accompanying background reactions and inclusive particle yields. The a ₀ ⁺ is considered as a usual u quark model state with two decay channels a ₀ ⁺↦K ⁺ and a ₀ ⁺↦π⁺η. Calculated cross-sections for a ₀ ⁺ production as well as for the corresponding non-resonant channels pp↦dK ⁺ and pp↦dπ⁺η are compared. Especially, in case of the final channel dπ⁺η, high statistics measurements are necessary to extract the a ₀ ⁺ signal from the high non-resonant background. Received: 20 December 2000 / Accepted: 7 May 2001     

On the possibility of observation of a 0-f 0 mixing in the pn → da 0 reaction

It is shown that, if isospin is not conserved in a ₀ ⁰ -and f ₀-meson mixing, forward-backward asymmetry arises in the pn→da ₀ ⁰ reaction. This effect increases near the reaction threshold. The asymmetry is estimated within the framework of a model in which the a ₀ ⁰ -f ₀ mixing is due to the virtual π⁰?η transition and the difference in masses of the charged and neutral kaons in decay channels. The angular asymmetry near the threshold of the pn→da ₀ ⁰ reaction was found to be large, of the order of 8–15%.     

Study of spectator tagging in the reaction np → ppπwith a deuteron beam

The reaction has been studied in a kinematically complete experiment at a single beam momentum GeV/c (T = 759MeV). All four ejectiles have been detected in the large-acceptance time-of-flight spectrometer COSY-TOF. We analyzed the data along the lines of the spectator model as a means to isolate the quasi-free reaction. The spectator proton was identified by its momentum and flight direction thus yielding access to the associated Fermi motion of the bound neutron. A comparison is carried out with Monte Carlo simulations based on two different parameterizations of the deuteron wave function. Up to a Fermi momentum of roughly 150MeV/c no significant deviations between experimental and simulated data of various observables were found from which we conclude that the deuteron can indeed be taken as a valid substitute for the neutron.     

Measurement of the total photoabsorption cross section on a proton in the energy range 600–1500 MeV at the GRAAL

The total photoabsorption cross section on a free proton was measured at the GRAAL facility in the energy range E _γ = 600−1500 MeV. The large-aperture LAGRANγE detector and a liquid hydrogen target were used in the experiment performed with a back-scattered Compton gamma beam. To improve the accuracy, two alternative methods were employed. First, a subtraction method of using empty-target measurements allowed the cross section σ _tot to be evaluated directly because of a low level of the electromagnetic background. Second, an algorithm for evaluating σ _tot on the basis of summing the dominating partial cross sections was developed. Experimental results obtained for σ _tot by the two methods are compared with existing data. The article was translated by the authors. Published in Russian in Yadernaya Fizika, 2008, Vol. 71, No. 1, pp. 76–83.     

Scaling in the mean of the p+p→π0+X inclusive reaction data and the energy dependence of Feynman variable

We have studied the p+p⁰+X inclusive reaction data of Carey et al. in the framework of the scaling in the mean hypothesis first proposed by Dao et al. These data have been used to obtain the gamma ray spectrum in terms of the average value of the Feynman variablex, written as x.A comparison with the observed gamma ray spectrum at Mt. Chacaltaya by the Japanese and Brazilian Group gives the energy dependence of x at very high energy.     

Measurement of the e + e − → ηπ+π− cross section in the \sqrt s = 1.04–1.38-GeV energy range with a spherical neutral detector at the VEPP-2M collider

The e ⁺ e ^? → ηπ⁺π^? cross section in the η → 2γ channel has been measured in the $ \sqrt s $ = 1.04- to 1.38-GeV energy range. The data with a total integrated luminosity of 9.05 pb^?1 were collected on a spherical neutral detector at the VEPP-2M collider. The results are consistent with the BaBar and CMD2 data and have a higher statistical accuracy.     

Precise measurement of the e^＋e^- →π^＋π^-（γ） cross section with the initial state radiation method at BABAR

We present a precise BABAR measurement on the cross section of the process e^＋e^- →π^＋π^-（γ） from threshold to an energy of 3 GeV with the initial state radiation （ISR） technique, using 232 fb^-1 of data collected with the BABAR detector at e^＋e^- center-of-mass energies near 10.58 GeV. The ISR luminosity is determined from a study of the leptonic process e^＋e^- →μ^＋μ^-γ（γ）. The leading-order hadronic contribution to the muon magnetic anomaly calculated using the ππ cross section measured from threshold to 1.8 GeV is （514.1± 2.2（stat） ± 3.1（syst）） × 10^-10.