In this paper we present quantitative results for coherent pion production by neutrinos scattered off nuclei within the framework developed by Gounaris, Kartavtsev and Paschos. The method is based on PCAC and uses helicity cross sections for the scattering of weak gauge bosons on nuclei. The process relies on experimental data for elastic pion-nucleus scattering. A detailed analysis of the differential and integrated cross sections is presented for neutral and charged currents, with special emphasis on the regions of integrations. The results are extended to energies of 10.0 GeV and are compared with experimental data.
Coherent pion production in low energy neutrino reactions is discussed in the framework of the partially conserved axial vector current theory (PCAC). The role of lepton mass effects in suppressing production of positively charged pions is discussed. Instead of using models of pion nucleus scattering, the available data on pion carbon scattering are implemented for an analysis of the PCAC prediction. Our results agree well with the published upper limits for positively charged production but are much below the recent MiniBooNE result for neutral pion production.
Coherent pion production by neutrinos has been interpreted in the framework of the Partially Conserved Axial Current hypothesis (PCAC) and explicit model calculations are available. In this article we compute angular correlations for the produced pions which may help to separate the signal from the background. We present many figures useful for the experiments and compare them with another model.
We present a microscopic model for neutrino induced one-pion production off the nucleon and its implementation for the purpose of calculating coherent pion production in nuclei. We further criticize the use of the Rein--Sehgal model for coherent pion production by low energy neutrinos. In particular, we show how the approximations in that model give rise to a much flatter differential cross section in the $η=E_π(1-\cosθ_π)$ variable. We discuss the limitations intrinsic to any approach based on the partial conservation of the axial current hypothesis and the inability of such models to properl…
The coherent production of the nP states of the $π^+π^-$ atoms ($A_{2π}$) in relativistic nucleus-nucleus collisions is considered as a possible source of the $A_{2π}(nP)$ beam for the pionium Lamb-shift measurement. A general expression for estimation of the $A_{2π}(nP)$ yield is derived in the framework of the equivalent photon approximation.
We present a new analysis to extract pion parton distribution functions (PDFs) within the framework of the statistical model. Starting from the statistical model first developed for the spin-1/2 nucleon, we extend this model to describe the spin-0 pion. Based on a combined fit to both the pion-induced Drell-Yan data and the pion-induced $J/Ψ$ production data, a new set of pion PDFs has been obtained. The inclusion of the $J/Ψ$ production data in the combined fit has provided additional constraints for better determining the gluon distribution in the pion. We also compare the pion PDFs obtained…
In this talk I review the main features of the coherent/diffractive pion production by neutrinos on nuclei. The method is based on PCAC and relates the reaction $\textbf{boson} + \textbf{nucleus} \to \textbf{pion} + \textbf{nucleus}$ to elastic pion-nucleus scattering. Estimates for the expected rates and distributions in neutrino reactions are presented with the help of hadronic data. The absolute rates are significantly smaller than the older estimates which brings theory in agreement with the neutral current measurements and the bounds in charged current reactions.
For a continued progress in the pursuit of neutrino oscillation parameters, we require to have a precise knowledge of the pion production processes which act as a source of backgrounds and systematic uncertainties in neutrino oscillation experiments because pions can mimic a final state electron (positron). Therefore a pion production principal interaction may appear to be quasi-elastic if the pion is absorbed in the final state interactions. Charged-current single pion production processes induced by $ν_μ$ and $\bar{ν_μ}$ interactions with hydrocarbon target $(CH_{2})$ has been studied using …
We discuss different parameterizations of the $C_5^A(q^2)$ $NΔ$ axial form factor, fitted to the old Argonne bubble chamber data for pion production by neutrinos, and we use coherent pion production to test their low $q^2$ behavior. We find moderate effects that will be difficult to observe with the accuracy of present experiments. We also discuss the use of the Rein-Sehgal model for low energy coherent pion production. By comparison to a microscopic calculation, we show the weaknesses of some of the approximations in that model that lead to very large cross sections as well as to the wrong sh…
This work represents an extension of the single pion production model proposed by D. Rein. The model consists of resonant pion production and nonresonant background contributions coming from three Born diagrams in the helicity basis. The new work includes lepton mass effects, and nonresonant interaction is described by five diagrams based on a nonlinear σ model. This work provides a full kinematic description of single pion production in the neutrino-nucleon interactions, including resonant and nonresonant interactions in the helicity basis, in order to study the interference effect.
We re-evaluate our model predictions in Phys. Rev. D 79, 013002 (2009) for different observables in neutrino induced coherent pion production. This comes as a result of the new improved fit to old bubble chamber data of the dominant axial C_5^A nucleon-to-Delta form factor. We find an increase of 20%-30% in the values for the total cross sections. Uncertainties induced by the errors in the determination of C_5^A are computed. Our new results turn out to be compatible within about $1σ$ with the former ones. We also stress the existing tension between the recent experimental determination of the…
The top-color assisted technicolor (TC2) mode predicts the existence of a pair of charged top-pions $π^{\pm}_t$. In this paper, we study the production of the charged top-pions pair $π^{\pm}_t$ at next generation $γγ$ colliders. The results show that the production rates can reach the level of $10^2$ fb with reasonable parameter space. With a large number of events and the clean background, the charged top-pion should be observable at the $γγ$ colliders. Therefore, our studies can help us to search for charged top-pion, and furthermore, to test the TC2 model.
The study of the properties of pion pairs emitted in pp Central Production Experiments (CEP) shows that a) scalar and tensor mesons production dominates at increasing energies and that 2++ production is suppressed by selecting events with low four momentum transfer square -t at both proton vertices and b) pion+pion- decays of the f0(1370) meson are directly observable as an isolated peak over a vanishing background between 1.1 and 1.6 GeV in measurements at high energies and low -t. Together with the measurements of the decay branching ratios of the f0(1370) into sigma sigma, rho rho, pion pio…
Pion production in deeply virtual Compton scattering
利用基于手征对称性的软π介子定理和$Δ(1232)$共振模型，提出了深虚康普顿散射（DVCS）过程中低能π介子产生截面的一个估计.特别是，我们表示的$e p \to e γπN$过程的广义部分子分布。我们提供的估计污染的$e p \to e γp$ DVCS观测值，由于这种相关的π介子生产过程中的实验数据是不完全排他性的，为一组代表目前或计划在JLab，HERMES和COMPASS实验的运动学条件。
Resonance production and decay into pion pairs is simulated in a non-extensive quark matter with multi-particle interactions. Final state pion spectra are found to take the form of the Tsallis distribution, in accordance with measurements. It has also been shown that, if a large number of particles with these multi-particle interactions are constrained to a constant energy hyper-surface in phase space, the one-particle distribution is the Tsallis distribution.
A new mechanism for the pion production in the high energy reactions is suggested. It is related to the possibility for direct production of the pions induced by instantons, topologically nontrivial gluonic excitations of QCD vacuum. This mechanism does not require any fragmentation functions for production of pseudoscalar mesons in high energy reactions with hadrons. We calculate the contribution of a new mechanism to the inclusive $π^0$-meson production in high energy proton-proton collision. It is shown that it gives the dominated contribution to the inclusive cross-sections in the few GeV …
Calculations of central exclusive diffractive di-pion continuum production are presented in the Regge-eikonal approach. Data from ISR, STAR, CDF and CMS were analyzed and compared with theoretical description. We also consider theoretical predictions for LHC, possible nuances and problems of calculations and prospects of investigations at present and future hadron colliders.
