Pion Channels Research Articles

First Measurement of η Meson Production in Neutrino Interactions on Argon with MicroBooNE.

We present a measurement of η production from neutrino interactions on argon with the MicroBooNE detector. The modeling of resonant neutrino interactions on argon is a critical aspect of the neutrino oscillation physics program being carried out by the DUNE and Short Baseline Neutrino programs. η production in neutrino interactions provides a powerful new probe of resonant interactions, complementary to pion channels, and is particularly suited to the study of higher-order resonances beyond the Δ(1232). We measure a flux-integrated cross section for neutrino-induced η production on argon of 3.22±0.84(stat)±0.86(syst) 10^{-41} cm^{2}/nucleon. By demonstrating the successful reconstruction of the two photons resulting from η production, this analysis enables a novel calibration technique for electromagnetic showers in GeV accelerator neutrino experiments.

Non-perturbative quantum chromodynamics and short strings in electron-positron pair annihilation to hadrons

We develop a new mathematical method to study the non-perturbative quantum chromodynamics effects in low-energy processes using ordinary and analytic perturbation theory (PT and APT). We apply this tool to extract the lowest dimensional condensates from the high-precision fits of the data on e+e–-annihilation to pion channels:  e+e− → π+π−, e+e− → 2π+2π−, e+e− → π+π−2π0, e+e− → 3π+3π− and e+e− → 2π+2π−2π0. The special attention is devoted to the existence of the contribution of dimension 2 operator. Our consideration is based on the dependence of Adler function corresponding to e+e−-annihilation into pions on both Q and Borel transform parameter M2. It is shown that within the framework of the proposed method the C2 coefficient of the dimension 2 operator is negative and is closer to zero for analytic perturbation theory, which may therefore be partially responsible for the effect of short strings.

Search for short strings ine+e−-annihilation

In this work the behavior of power corrections to Adler finction in operator product expansion (OPE) is studied, in particular the possible contribution of operator of dimension 2. The OPE terms of dimension 4 and 6 are taken into account. Various experimental data on reactions of $e^+e^-$-annihilation to pion channels ($\pi^+\pi^-$, $2\pi^+2\pi^-$, $\pi^+\pi^-2\pi^0$, $3\pi^+3\pi^-$, $2\pi^+2\pi^-2\pi^0$) are used. The high-precision fits of the experimental data are obtained and used. The method based on Borel transform of Adler function is applied. It is shown that the contribution of operator of dimension 2 is negative being compatible to zero at three standard deviations level. The strong (anti)corellation between short string and local gluon condensate is found.

Erratum: Pseudoscalar meson and charmed baryon scattering lengths [Phys. Rev. D86, 034009 (2012)

We have calculated the scattering lengths between the pseudoscalar meson and charmed triplet, sextet, and excited sextet baryon to the third order with the heavy baryon chiral perturbation theory. The chiral expansion of the pion channels converges well.

Beam-spin asymmetries from semi-inclusive pion electroproduction

We have measured the moment $A_{LU}^{\sin\phi}$ corresponding to the polarized electron beam-spin asymmetry in SIDIS. $A_{LU}^{\sin\phi}$ is a twist-3 quantity providing information about quark-gluon correlations. Data were taken with the CLAS Spectrometer at Jefferson Lab using a 5.498 GeV longitudinally polarized electron beam and an unpolarized liquid hydrogen target. All three pion channels ($\pi^+$, $\pi^0$ and $\pi^-$) were measured simultaneously over a large range of kinematics within the virtuality range $Q^2 \approx$ 1.0-4.5 GeV$^2$. The observable was measured with better than 1% statistical precision over a large range of $z$, $P_T$, $x_B$, and $Q^{2}$, which permits comparison with several reaction models. The discussed measurements provide an upgrade in statistics over previous measurements, and serve as the first evidence for the negative sign of the $\pi^{-}$ $\sin\phi$ moment.

Cross sections and asymmetries for the [formula omitted] reaction from threshold to 1 GeV

Total cross sections, differential cross sections and asymmetries for the reaction p( p,π 0)pp from threshold to 1 GeV have been measured. The outgoing π 0 was detected by a 4π neutral meson spectrometer. Our data are compared with the corresponding np→NN π ± reactions. The isoscalar partial cross sections are extracted from the relevant total cross sections. They are significant throughout the whole energy range. Below the Δ-region, energy-integrated differential cross sections show a large anisotropy difference between the neutral and charged pion channels, respectively. A partial-wave fit shows that the initial T = 0 state is dominated by the 3D 1 wave in this energy region. Finally, predictions of phenomenological models give reasonable good account of the measured observables but cannot reproduce the sign of the asymmetries.

Photofission of235U and238U at intermediate energies: absolute cross sections and fragment mass distributions

The total photofission cross section σγ,F for235U and238U has been measured in the energy range 50≤E γ≤800 MeV at the 855 MeV Mainz Microtron MAMI using energy and time tagged photons (Glasgow Tagger) and a 4π arrangement of position sensitive fragment detectors. Besides the absolute photofission cross section σγF , which almost completely exhausts the total photon absorption cross section for these nuclei, fragment mass distributions in this energy domain were determined via time of flight techniques (TOF). The results for the total photofission cross sections σγ,F normalized to the atomic numberA for both isotopes coincide, and agree in theΔ-resonance region, within the systematic errors, with the socalled“Universal Curve” σγ,T /A of the total photon absorption cross section σγ,T . At higher energies the cross sections exhibit a smooth behaviour. In particular, it is shown for the first time that there isno resonance-like shape near the D13 resonance (at ≈710 MeV) as observed for the free proton. This complete suppression of the D13 resonance in complex nuclei is not yet understood on a microscopic level. The fragment mass distributions show a predominantly mass symmetric fission. However, contributions from mass asymmetric fission at some photon energies may give a hint of an increased mass asymmetric fission after the onset of the pion and two pion channels.

Strong decays of strange charmed P-wave mesons.

Goldstone boson decays of P-wave $D_s^{**}$ mesons are studied within the framework of Heavy Hadron Chiral Perturbation Theory. We first analyze the simplest single kaon decays of these strange charmed mesons. We derive a model independent prediction for the width of $D_{s2}$ and use experimental information on $D_{s1}$ to constrain the S-wave contribution to $D_1^0$ decay. Single and double pion decay modes are then discussed and shown to be significantly restricted by isospin conservation. We conclude that the pion channels may offer the best hope for detecting one strange member of an otherwise invisible P-wave flavor multiplet.

Systematics of hadron-proton diffractive scattering at high energies

We apply the eikonal formalism to existingπ±,K±,p,\(\bar p\),∑− andΞ− elastic scattering data on a target proton in order to perform a detailed test of the additivity of eikonals of the constituent quark-quark interaction. The difference between the pion and kaon channels imposes an obvious flavor dependence. In addition, the systematic treatment of meson and baryon scattering for all values oft requires a renormalization of the fundamental interaction strength which persists in a rescattering treatment of the problem as well as with the inclusion of gluonic degrees of freedom. A variety of form factors and elementary amplitudes are studied with wide ranging consequences on the quality of the reproduction of the data.

Cancer radiotherapy using negative pi-mesons

The energy released by the annihilation of negative pions on capture at the end of their range makes a beam of pions particularly promising for treating deep-seated malignancies by reducing unnecessary damage done to surrounding normal tissues. Biomedical pion channels were constructed in all meson facilities and routine clinical trials are now being conducted. This paper briefly reviews the development of the pion radiotherapy program at TRIUMF over the past decade.

Distortion effects in a relativistic one-nucleon model for the (p,π+) reaction

A relativistic distorted-wave Born approximation model is developed for (p,..pi../sup +/) reactions within the framework of the one-nucleon mechanism. The nucleon motion is described by solutions to the Dirac equation with appropriate nuclear potentials. Distortion effects in both the proton and pion channels are taken into account and are found to be important. Both pseudovector and pseudoscalar forms of the ..pi..NN vertex are considered. The former is found to lead invariably to better agreement with the data. Calculations have been carried out for proton energies < or =200 MeV. Good agreement is obtained with the cross section data for reactions on /sup 40/Ca and /sup 16/O leading to the ground state of the residual nucleus. For reactions on /sup 12/C, the cross section shapes, but not their magnitudes, are reproduced. The calculated analyzing powers are found to be in good agreement with the forward angle data.

Pion exchange effects in nuclear reactions at large momentum transfers

The role of the inelastic pion channels of the nucleon-nucleon interaction at large momentum transfers is examined in view of recent experiments on nucleon transfer and pion production reactions. At energies below the pion production threshold the excitation functions of proton elastic back scattering from $^{2}\mathrm{H}$, $^{3}\mathrm{He}$, and $^{4}\mathrm{He}$ are characteristic of a simple nucleon exchange mechanism. The high energy region can be understood in terms of pion exchange contributions as expressed by triangle diagrams with the subprocesses $\mathrm{pp}\ensuremath{\rightarrow}^{2}\mathrm{H}\ensuremath{\pi}$, $p^{2}\mathrm{H}\ensuremath{\rightarrow}^{3}\mathrm{H}\ensuremath{\pi}$, and $p^{3}\mathrm{He}\ensuremath{\rightarrow}^{4}\mathrm{He}\ensuremath{\pi}$, respectively. Similarly, "hidden" pion exchange effects are suggested as an explanation for the excitation functions of $^{4}\mathrm{He}$($p$,$d$)$^{3}\mathrm{He}$ and $^{4}\mathrm{He}$($p$,$^{3}\mathrm{He}$)$^{2}\mathrm{H}$, invoking the proton backscattering reactions $p^{2}\mathrm{H}\ensuremath{\rightarrow}^{2}\mathrm{H}p$ and $p^{3}\mathrm{He}\ensuremath{\rightarrow}^{3}\mathrm{He}p$ as subprocesses.NUCLEAR REACTIONS ($p$,$p$) backscattering from $^{2}\mathrm{H}$, $^{3}\mathrm{He}$, and $^{4}\mathrm{He}$, and $^{4}\mathrm{He}$($p$,$d$)$^{3}\mathrm{He}$ and $^{4}\mathrm{He}$($p$,$^{3}\mathrm{He}$)$^{2}\mathrm{H}$ for ${T}_{p}\ensuremath{\approx}100\ensuremath{-}700$ MeV; excitation functions of $\frac{d\ensuremath{\sigma}}{d\ensuremath{\Omega}}$ (${\ensuremath{\theta}}_{0}$,$T$) analyzed in terms of nucleon exchange and pion exchange supported reaction mechanisms.

A very reliable pion conversion target

Abstract The pion conversion target of the Linear Accelerator of Saclay has been built to supply two pion channels. It is a solid copper, water-cooled, rotating wheel supporting the full power of the electron beam. It overcomes radiation problems by its simplicity and its easy interchangeability without exposing people to radiation.

Introduction to the use of negative pi-mesons in radiation therapy: Rutherford 1964, revisited

The existence of negative pi-mesons was predicted from considerations of infra-nuclear binding forces by Yukawa in 1935. Direct evidence for these unique particles was discovered during cosmic ray research by Lattes, Occhialini and Powell in 1947. I understand that the possibility that pions might be useful in radiation therapy was discussed by Drs. Chaim Richman and Cornelius Tobias here in Berkeley in about 1952. The fist detailed easy on this possibility, by P. H. Fowler and D. H. Perkins, appeared is Nature in 1961 and predicted many of the pertinent characteristics of the potential therapeutic usefulness of negative pi-mesons. Fowler described these in further detail in the 1964 Rutherford Memorial Lecture, entitled “Pi Mesons Versus Cancer.” These articles stimulated a search for appropriate methods for production of pi-mesons in sufficient quantity for consideration of human therapy. Unfortunately, as the requirements for such a device are severe, it was not until recently that particle accelerators with sufficiently high beam currents became available. Thus, clinically useful pion channels have been added to proton accelerators at Los Alamos and Vancouver. In addition, a high-yield pion concentrator has been constructed at Stanford for use with a high-intensity electron beam, and this is being adapted in Zurich for use with a proton beam. Preliminary treatment planning, using the known characteristics of pion beams, has yielded interesting and apparently unique treatment plans which promise higher biological dose to the target volume and greater protection to normal tissues. This combination may offer greater opportunity for control of neoplasms at the primary site and also control of such neoplasms as carcinoma of the pancreas and osteosarcoma, known poor responders to conventional high-energy X-irradiation.

Study of the R meson produced in 13 GeV/ cπ+p interactions

The missing mass spectrum opposite the proton in a 750 000 picture exposure, 13 GeV/ c π +p bubble chamber experiment, is investigated in two and four pion channels for structures observed or denied by boson spectrometers at the same energy in the reaction π −p→X −p. In the four pion final state the R + enhancement is observed clearly and the possibility of multi-component mass structure is considered. Treating the phenomenon as one object, cross sections and branching ratios are derived for intermediate quasi two and three body decay modes ( ωπ, ϱϱ, A 2 π, ϱππ). The signals in the two pion state and for the neutral state produced opposite Δ ++(1231) are also presented and an elasticity is calculated.

A conceptual study of a 300 MeV pion channel for TRIUMF

Secondary pion channels with good resolution and acceptance are discussed. Various methods of separating pions from protons at small angles are compared including a novel technique which uses a quadropole, septum magnet combination.

Design of Secondary Beam Channels for the Nevis Synchrocyclotron Conversion Program

The modification program includes the design of two pion channels characterized by 0?Po?250 MeV/c with ±1% ??P/Po?±10% and 200? Po?400 MeV/c with ±0.5%??P/Po?±3% and a stopped muon channel with low contamination and average polarization ?70%. Two computer programs instrumental in their design are described. BARTELBE utilizes a function minimizing code in conjunction with first order beam optics to simultaneously optimize any number of desired conditions relating to e.g., a desired optical system and momentum resolution, and a beam acceptance volume. MAGSYS is a Monte Carlo code which generates each pion according to given input parameters and follows its history through a system. In the output are e.g. detailed pion and muon beam profiles and muon polarization.