No Arabic abstract
The fixed-target MIPP experiment, Fermilab E907, was designed to measure the production of hadrons from the collisions of hadrons of momenta ranging from 5 to 120 GeV/c on a variety of nuclei. These data will generally improve the simulation of particle detectors and predictions of particle beam fluxes at accelerators. The spectrometer momentum resolution is between 3 and 4%, and particle identification is performed for particles ranging between 0.3 and 80 GeV/c using $dE/dx$, time-of-flight and Cherenkov radiation measurements. MIPP collected $1.42 times10^6$ events of 120 GeV Main Injector protons striking a target used in the NuMI facility at Fermilab. The data have been analyzed and we present here charged pion yields per proton-on-target determined in bins of longitudinal and transverse momentum between 0.5 and 80 GeV/c, with combined statistical and systematic relative uncertainties between 5 and 10%.
The COMPASS collaboration at CERN has investigated pion Compton scattering, $pi^-gammarightarrow pi^-gamma$, at centre-of-mass energy below 3.5 pion masses. The process is embedded in the reaction $pi^-mathrm{Ni}rightarrowpi^-gamma;mathrm{Ni}$, which is initiated by 190,GeV pions impinging on a nickel target. The exchange of quasi-real photons is selected by isolating the sharp Coulomb peak observed at smallest momentum transfers, $Q^2<0.0015$,(GeV/$c$)$^2$. From a sample of 63,000 events the pion electric polarisability is determined to be $alpha_pi = (,2.0 pm 0.6_{mbox{scriptsize stat}} pm 0.7_{mbox{scriptsize syst}},) times 10^{-4},mbox{fm}^3$ under the assumption $alpha_pi=-beta_pi$, which relates the electric and magnetic dipole polarisabilities. It is the most precise measurement of this fundamental low-energy parameter of strong interaction, that has been addressed since long by various methods with conflicting outcomes. While this result is in tension with previous dedicated measurements, it is found in agreement with the expectation from chiral perturbation theory. An additional measurement replacing pions by muons, for which the cross-section behavior is unambigiously known, was performed for an independent estimate of the systematic uncertainty.
We report on the first cross section measurements for charged current coherent pion production by neutrinos and antineutrinos on argon. These measurements are performed using the ArgoNeuT detector exposed to the NuMI beam at Fermilab. The cross sections are measured to be $2.6^{+1.2}_{-1.0}(stat)^{+0.3}_{-0.4}(syst) times 10^{-38} textrm{cm}^{2}/textrm{Ar}$ for neutrinos at a mean energy of $9.6$ GeV and $5.5^{+2.6}_{-2.1}(stat)^{+0.6}_{-0.7}(syst) times 10^{-39} textrm{cm}^{2}/textrm{Ar}$ for antineutrinos at a mean energy of $3.6$ GeV.
The electric (${alpha}_{pi}$) and the magnetic (${beta}_{pi}$) polarisabilities are fundamental properties of the pion characterising the rigidity of its internal structure. They have been precisely measured at the COMPASS experiment at CERN with a ${pi}^{-}$ beam of 190~GeV/c assuming ${alpha}_{pi}+{beta}_{pi}=0$. Muons of the same momentum were used for controlling of systematic effects. The obtained result ${alpha}_{pi}=-{beta}_{pi}=(2.0pm 0.6_{stat.}pm 0.7_{syst.})times 10^{-4} fm^3$ is in agreement with the prediction of the Chiral Perturbation Theory.
We report the measurements of single and double differential cross section of muon neutrino charged-current interactions on carbon with a single positively charged pion in the final state at the T2K off-axis near detector using $5.56times10^{20}$ protons on target. The analysis uses data control samples for the background subtraction and the cross section signal, defined as a single negatively charged muon and a single positively charged pion exiting from the target nucleus, is extracted using an unfolding method. The model dependent cross section, integrated over the T2K off-axis neutrino beam spectrum peaking at $0.6$~GeV, is measured to be $sigma = (11.76 pm 0.44 text{(stat)} pm 2.39 text{(syst)}) times 10^{-40} text{cm}^2$~$text{nucleon}^{-1}$. Various differential cross sections are measured, including the first measurement of the Adler angles for single charged pion production in neutrino interactions with heavy nuclei target.
We report the result from a search for charged-current coherent pion production induced by muon neutrinos with a mean energy of 1.3 GeV. The data are collected with a fully active scintillator detector in the K2K long-baseline neutrino oscillation experiment. No evidence for coherent pion production is observed and an upper limit of $0.60 times 10^{-2}$ is set on the cross section ratio of coherent pion production to the total charged-current interaction at 90% confidence level. This is the first experimental limit for coherent charged pion production in the energy region of a few GeV.