A search for millicharged particles, a simple extension of the standard model, has been performed with the ArgoNeuT detector exposed to the Neutrinos at the Main Injector beam at Fermilab. The ...ArgoNeuT liquid argon time projection chamber detector enables a search for millicharged particles through the detection of visible electron recoils. We search for an event signature with two soft hits (MeV-scale energy depositions) aligned with the upstream target. For an exposure of the detector of 1.0×10^{20} protons on target, one candidate event has been observed, compatible with the expected background. This search is sensitive to millicharged particles with charges between 10^{-3}e and 10^{-1}e and with masses in the range from 0.1 to 3 GeV. This measurement provides leading constraints on millicharged particles in this large unexplored parameter space region.
MeV-scale energy depositions by low-energy photons produced in neutrino-argon interactions have been identified and reconstructed in ArgoNeuT liquid argon time projection chamber (LArTPC) data. ...ArgoNeuT data collected on the NuMI beam at Fermilab were analyzed to select isolated low-energy depositions in the TPC volume. The total number, reconstructed energies, and positions of these depositions have been compared to those from simulations of neutrino-argon interactions using the fluka Monte Carlo generator. Measured features are consistent with energy depositions from photons produced by deexcitation of the neutrino’s target nucleus and by inelastic scattering of primary neutrons produced by neutrino-argon interactions. This study represents a successful reconstruction of physics at the MeV scale in a LArTPC, a capability of crucial importance for detection and reconstruction of supernova and solar neutrino interactions in future large LArTPCs.
A search for heavy neutral leptons has been performed with the ArgoNeuT detector exposed to the NuMI neutrino beam at Fermilab. We search for the decay signature N → νμ+ μ−, considering decays ...occurring both inside ArgoNeuT and in the upstream cavern. In the data, corresponding to an exposure to 1.25 × 1020 POT , zero passing events are observed consistent with the expected background. This measurement leads to a new constraint at 90% confidence level on the mixing angle |UτN|2 of tau-coupled Dirac heavy neutral leptons with masses mN = 280–970 MeV, assuming |UeN|2 = |UμN|2 = 0.
The capabilities of liquid argon time projection chambers (LArTPCs) to reconstruct the spatial and calorimetric information of neutrino events have made them the detectors of choice in a number of ...experiments, specifically those looking to observe electron neutrino (νe) appearance. The LArTPC promises excellent background rejection capabilities, especially in this “golden” channel for both short and long baseline neutrino oscillation experiments. We present the first experimental observation of electron neutrinos and antineutrinos in the ArgoNeut LArTPC, in the energy range relevant to DUNE and the Fermilab Short Baseline Neutrino Program. We have selected 37 electron candidate events and 274 gamma candidate events, and measured an 80% purity of electrons based on a topological selection. Additionally, we present a separation of electrons from gammas using calorimetric energy deposition, demonstrating further separation of electrons from background gammas.
We present the results of a search for heavy QCD axions performed by the ArgoNeuT experiment at Fermilab. We search for heavy axions produced in the NuMI neutrino beam target and absorber decaying ...into dimuon pairs, which can be identified using the unique capabilities of ArgoNeuT and the MINOS near detector. This decay channel is motivated by a broad class of heavy QCD axion models that address the strong CP and axion quality problems with axion masses above the dimuon threshold. We obtain new constraints at a 95% confidence level for heavy axions in the previously unexplored mass range of 0.2-0.9 GeV, for axion decay constants around tens of TeV.
We report the first electron neutrino cross section measurements on argon, based on data collected by the ArgoNeuT experiment running in the GeV-scale NuMI beamline at Fermilab. A flux-averaged νe + ...νe total and a lepton angle differential cross section are extracted using 13 νe and νe events identified with fully automated selection and reconstruction. We employ electromagnetic-induced shower characterization and analysis tools developed to identify νe / νe-like events among complex interaction topologies present in ArgoNeuT data ( ⟨ E νe ⟩ = 4.3 GeV and ⟨ E νe ⟩ = 10.5 GeV ). The techniques are widely applicable to searches for electron-flavor appearance at short and long baseline using liquid argon time projection chamber technology. Notably, the data-driven studies of GeV-scale νe / νe interactions presented here probe an energy regime relevant for future DUNE oscillation physics.
We report on the first measurement of flux-integrated single differential cross sections for charged-current (CC) muon neutrino (νμ) scattering on argon with a muon and a proton in the final state, ...Ar40 (νμ,μp)X. The measurement was carried out using the Booster Neutrino Beam at Fermi National Accelerator Laboratory and the MicroBooNE liquid argon time projection chamber detector with an exposure of 4.59×1019 protons on target. Events are selected to enhance the contribution of CC quasielastic (CCQE) interactions. The data are reported in terms of a total cross section as well as single differential cross sections in final state muon and proton kinematics. We measure the integrated per-nucleus CCQE-like cross section (i.e., for interactions leading to a muon, one proton, and no pions above detection threshold) of (4.93±0.76stat±1.29sys)×10−38 cm2, in good agreement with theoretical calculations. The single differential cross sections are also in overall good agreement with theoretical predictions, except at very forward muon scattering angles that correspond to low-momentum-transfer events.
We present an analysis of MicroBooNE data with a signature of one muon, no pions, and at least one proton above a momentum threshold of 300 MeV/c(CC0πNp). This is the first differential cross-section ...measurement of this topology in neutrino-argon interactions. We achieve a significantly lower proton momentum threshold than previous carbon and scintillator-based experiments. Using data collected from a total of approximately 1.6 × 1020 protons on target, we measure the muon neutrino cross section for the CC0πNp interaction channel in argon at MicroBooNE in the Booster Neutrino Beam which has a mean energy of around 800 MeV. We present the results from a data sample with estimated efficiency of 29% and purity of 76% as differential cross sections in five reconstructed variables: the muon momentum and polar angle, the leading proton momentum and polar angle, and the muon-proton opening angle. We include smearing matrices that can be used to "forward fold" theoretical predictions for comparison with these data. We compare the measured differential cross sections to a number of recent theory predictions demonstrating largely good agreement with this first-ever dataset on argon.
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