First Measurement of Neutrino and Antineutrino Coherent Charged Pion Production on Argon

Abstract

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)−38 cm 2 /Ar for neutrinos at a mean energy of 9.6 GeV and 5.5−0.7 (syst) × 10 −39 cm 2 /Ar for antineutrinos at a mean energy of 3.6 GeV.Neutrinos can produce single pion final states by coherently scattering from the entire nucleus. Both neutral current (NC) and charged current (CC) processes are possible. In these interactions, the squared fourmomentum transfer to the target nucleus, |t|, is small so the nucleus remains unchanged. In this Letter, we focus on the CC coherent pion production from muon neutrinos and antineutrinos on argon:where the low |t| condition entails that the pions and muons are forward going with respect to the incoming neutrino direction. There are several models from which one can extract cross sections and kinematical predictions for this interaction. The Rein-Seghal [1] model has been used to successfully describe high energy data within experimental uncertainties since the first observation of coherent pion production at the Aachen-Padova spark chamber [2] in 1983. This approach is based on Adler's Partially Conserved Axial Current (PCAC) theorem [3], which relates the pion production cross section to the cross section for the pion-nucleus scattering. This model is still the standard for neutrino generators today, such as genie [4], nuwro [5], and neut [6], with continued updates to the formalism and the pion-nucleus scattering data that is used. With recent interest in coherent pion production in the theoretical community, other PCAC models have been proposed [7,8]. Microscopic models [9][10][11] have also been suggested, which employ a full quantum mechanical treatment that explores the excitation and decay of the ∆ resonance. While the PCAC based models are a simple approach, tailored for the description of high energy data, their extension to the few GeV regime is not straightforward. Notably, the K2K [12] and SciBooNE [13] collaborations found cross section upper limits for the CC coherent pion production well below Rein-Seghal's estimation. The microscopic models are better motivated at lower neutrino energies but currently cannot be used to describe high energy data. Given the differences in these models, more experimental measurements are necessary to validate and tune the models and, in particular, better understand the transition region between microscopic and PCAC validity at E ν ∼ 3 − 5 GeV.In this Letter, a measurement of CC coherent pion production from the ArgoNeuT (Argon Neutrino Test) experiment is presented. ArgoNeuT [14] is a 170 L liquid argon time projection chamber (LArTPC), with dimensions 47 × 40 × 90 cm 3 . The electric field inside the TPC is 481 V/cm, and the drifted charge from particle interactions is read out in two planes of 240 wires with 4 mm pitch (the inductio...

Measurement of total and differential cross sections of neutrino and antineutrino coherent π± production on carbon

“…49. This includes recent measurements from ArgoNEUT [33] and T2K [71] which are significantly less precise than the MINERvA measurements and do not report differential cross sections. The T2K measurement, however, plays a special role here in that it shows consistency of the cross section at lower energies than accessible by MINERvA with the dσ=dE π at low pion energies below the prediction of the GENIE Rein-Sehgal model.…”

“…Many measurements of NC [16][17][18][19][20][21][22][23][24] and CC [19,[25][26][27][28][29][30][31][32][33]] coherent pion production have been made at neutrino energies of 1 ≲ E ν ≲ 100 GeV using both ν μ andν μ beams and a variety of scattering target materials (carbon, neon, aluminum, argon, Freon, glass, marble, and iron). Measurements made before the discovery of neutrino oscillations were mostly made at E ν > 10 GeV.…”

Neutrino trident scattering at near detectors

“…The charged current version serves mainly as a background to µ + µ − tridents, but can also appear as a background for e ± µ ∓ tridents for incoming electron neutrinos or antineutrinos. It has been studied before at MiniBooNE [60], MINERνA [61,62], T2K [28,63], and for the first time in LAr at ArgoNeuT [64]. This process has a very distict low 4-momentum transfer to the nucleus |t| [61], but a much flatter distribution in invariant mass if compared to trident.…”

The Liquid Argon Software Toolkit (LArSoft): Goals, Status and Plan

“…new high performance computing platforms). The ArgoNeuT [4], LArIAT [5], MicroBooNE [6], DUNE [7] and SBND [8] experiments currently use LArSoft, with the ICARUS [9] experiment considering some use of LArSoft as part of the Short Baseline Neutrino (SBN) program at Fermilab. The collaborations contribute algorithms and tools, as well as set requirements and priorities.…”