arXiv subjects

N. Graf

Publications and source records attributed to N. Graf.

At least 19 recordsLinked to original sources

arXiv2026

Modeling the Effect of the Heliospheric Magnetic Field on Cosmic Ray Muon Shadows

Shadows cast in the cosmic ray (CR) muon sky by the Sun were located using muon data from the MINOS far detector in Northern Minnesota. The shadows were observed independently across three time periods; near solar minimum, near solar maximum, and over the entire 13 year span of the data. A distribution of muon positions for each shadow was then sampled to simulate CR motions near the Sun using the Parker spiral model of the Heliospheric Magnetic Field (HMF) and a dipole model of the Geomagnetic Field (GMF). The resulting particle distributions were then compared to their position with respect to the Sun. Results show that the Parker spiral model is most consistent with the solar minimum shadow and least consistent with the solar maximum shadow, as expected. The simple Parker spiral is more consistent with the data for a harder CR spectrum than is actually present, indicating the need for a more detailed HMF model. Plausible modifications to the Parker spiral model which would affect the overall shift of the Sun's CR shadow are discussed.

astro-ph.SR↗

arXiv2022

Searching for Prompt and Long-Lived Dark Photons in Electro-Produced $e^+e^-$ Pairs with the Heavy Photon Search Experiment at JLab

The Heavy Photon Search experiment (HPS) at the Thomas Jefferson National Accelerator Facility searches for electro-produced dark photons. We report results from the 2016 Engineering Run consisting of 10608/nb of data for both the prompt and displaced vertex searches. A search for a prompt resonance in the $e^+e^-$ invariant mass distribution between 39 and 179 MeV showed no evidence of dark photons above the large QED background, limiting the coupling of {\epsilon}^2 {\geq} 10^-5, in agreement with previous searches. The search for displaced vertices showed no evidence of excess signal over background in the masses between 60 and 150 MeV, but had insufficient luminosity to limit canonical heavy photon production. This is the first displaced vertex search result published by HPS. HPS has taken high-luminosity data runs in 2019 and 2021 that will explore new dark photon phase space.

hep-ex↗

arXiv2022

Solid State Detectors and Tracking for Snowmass

Tracking detectors are of vital importance for collider-based high energy physics (HEP) experiments. The primary purpose of tracking detectors is the precise reconstruction of charged particle trajectories and the reconstruction of secondary vertices. The performance requirements from the community posed by the future collider experiments require an evolution of tracking systems, necessitating the development of new techniques, materials and technologies in order to fully exploit their physics potential. In this article we summarize the discussions and conclusions of the 2022 Snowmass Instrumentation Frontier subgroup on Solid State and Tracking Detectors (Snowmass IF03).

physics.ins-det↗

arXiv2020

Precision constraints for three-flavor neutrino oscillations from the full MINOS+ and MINOS data set

We report the final measurement of the neutrino oscillation parameters $\Delta m^2_{32}$ and $\sin^2\theta_{23}$ using all data from the MINOS and MINOS+ experiments. These data were collected using a total exposure of $23.76 \times 10^{20}$ protons on target producing $\nu_{mu}$ and $\overline{\nu_\mu}$ beams and 60.75 kt$\cdot$yr exposure to atmospheric neutrinos. The measurement of the disappearance of $\nu_{\mu}$ and the appearance of $\nu_e$ events between the Near and Far detectors yields $|\Delta m^2_{32}|=2.40^{+0.08}_{-0.09}~(2.45^{+0.07}_{-0.08}) \times 10^{-3}$ eV$^2$ and $\sin^2\theta_{23} = 0.43^{+0.20}_{-0.04} ~(0.42^{+0.07}_{-0.03})$ at 68% C.L. for Normal (Inverted) Hierarchy.

hep-ex↗

arXiv2020

Improved Constraints on Sterile Neutrino Mixing from Disappearance Searches in the MINOS, MINOS+, Daya Bay, and Bugey-3 Experiments

Searches for electron antineutrino, muon neutrino, and muon antineutrino disappearance driven by sterile neutrino mixing have been carried out by the Daya Bay and MINOS+ collaborations. This Letter presents the combined results of these searches, along with exclusion results from the Bugey-3 reactor experiment, framed in a minimally extended four-neutrino scenario. Significantly improved constraints on the $\theta_{\mu e}$ mixing angle are derived that constitute the most stringent limits to date over five orders of magnitude in the sterile mass-squared splitting $\Delta m^2_{41}$, excluding the 90% C.L. sterile-neutrino parameter space allowed by the LSND and MiniBooNE observations at 90% CL$_s$ for $\Delta m^2_{41}<5\,$eV$^2$.Furthermore, the LSND and MiniBooNE 99% C.L. allowed regions are excluded at 99% CL$_s$ for $\Delta m^2_{41}$ $<$ 1.2 eV$^2$.

hep-ex↗

arXiv2018

Search for a Dark Photon in Electro-Produced $e^{+}e^{-}$ Pairs with the Heavy Photon Search Experiment at JLab

The Heavy Photon Search experiment took its first data in a 2015 engineering run using a 1.056 GeV, 50 nA electron beam provided by CEBAF at the Thomas Jefferson National Accelerator Facility, searching for an electro-produced dark photon. Using 1.7 days (1170 nb$^{-1}$) of data, a search for a resonance in the $e^{+}e^{-}$ invariant mass distribution between 19 and 81 MeV/c$^2$ showed no evidence of dark photon decays above the large QED background, confirming earlier searches and demonstrating the full functionality of the experiment. Upper limits on the square of the coupling of the dark photon to the Standard Model photon are set at the level of 6$\times10^{-6}$. In addition, a search for displaced dark photon decays did not rule out any territory but resulted in a reliable analysis procedure that will probe hitherto unexplored parameter space with future, higher luminosity runs.

hep-ex↗

arXiv2018

Search for a Dark Photon in Electro-Produced $e^{+}e^{-}$ Pairs with the Heavy Photon Search Experiment at JLab

The Heavy Photon Search experiment took its first data in a 2015 engineering run at the Thomas Jefferson National Accelerator Facility, searching for a prompt, electro-produced dark photon with a mass between 19 and 81 MeV/$c^2$. A search for a resonance in the $e^{+}e^{-}$ invariant mass distribution, using 1.7 days (1170 nb$^{-1}$) of data, showed no evidence of dark photon decays above the large QED background, confirming earlier searches and demonstrating the full functionality of the experiment. Upper limits on the square of the coupling of the dark photon to the Standard Model photon are set at the level of 6$\times10^{-6}$. Future runs with higher luminosity will explore new territory.

hep-ex↗

arXiv2017

Search for sterile neutrinos in MINOS and MINOS+ using a two-detector fit

A search for mixing between active neutrinos and light sterile neutrinos has been performed by looking for muon neutrino disappearance in two detectors at baselines of 1.04 km and 735 km, using a combined MINOS and MINOS+ exposure of $16.36\times10^{20}$ protons-on-target. A simultaneous fit to the charged-current muon neutrino and neutral-current neutrino energy spectra in the two detectors yields no evidence for sterile neutrino mixing using a 3+1 model. The most stringent limit to date is set on the mixing parameter $\sin^2\theta_{24}$ for most values of the sterile neutrino mass-splitting $\Delta m^2_{41} > 10^{-4}$ eV$^2$.

hep-ex↗

arXiv2017

The Pandora multi-algorithm approach to automated pattern recognition of cosmic-ray muon and neutrino events in the MicroBooNE detector

The development and operation of Liquid-Argon Time-Projection Chambers for neutrino physics has created a need for new approaches to pattern recognition in order to fully exploit the imaging capabilities offered by this technology. Whereas the human brain can excel at identifying features in the recorded events, it is a significant challenge to develop an automated, algorithmic solution. The Pandora Software Development Kit provides functionality to aid the design and implementation of pattern-recognition algorithms. It promotes the use of a multi-algorithm approach to pattern recognition, in which individual algorithms each address a specific task in a particular topology. Many tens of algorithms then carefully build up a picture of the event and, together, provide a robust automated pattern-recognition solution. This paper describes details of the chain of over one hundred Pandora algorithms and tools used to reconstruct cosmic-ray muon and neutrino events in the MicroBooNE detector. Metrics that assess the current pattern-recognition performance are presented for simulated MicroBooNE events, using a selection of final-state event topologies.

hep-ex↗

arXiv2017

Measurement of cosmic-ray reconstruction efficiencies in the MicroBooNE LArTPC using a small external cosmic-ray counter

The MicroBooNE detector is a liquid argon time projection chamber at Fermilab designed to study short-baseline neutrino oscillations and neutrino-argon interaction cross-section. Due to its location near the surface, a good understanding of cosmic muons as a source of backgrounds is of fundamental importance for the experiment. We present a method of using an external 0.5 m (L) x 0.5 m (W) muon counter stack, installed above the main detector, to determine the cosmic-ray reconstruction efficiency in MicroBooNE. Data are acquired with this external muon counter stack placed in three different positions, corresponding to cosmic rays intersecting different parts of the detector. The data reconstruction efficiency of tracks in the detector is found to be $\epsilon_{\mathrm{data}}=(97.1\pm0.1~(\mathrm{stat}) \pm 1.4~(\mathrm{sys}))\%$, in good agreement with the Monte Carlo reconstruction efficiency $\epsilon_{\mathrm{MC}} = (97.4\pm0.1)\%$. This analysis represents a small-scale demonstration of the method that can be used with future data coming from a recently installed cosmic-ray tagger system, which will be able to tag $\approx80\%$ of the cosmic rays passing through the MicroBooNE detector.

hep-ex↗

arXiv2017

Noise Characterization and Filtering in the MicroBooNE Liquid Argon TPC

The low-noise operation of readout electronics in a liquid argon time projection chamber (LArTPC) is critical to properly extract the distribution of ionization charge deposited on the wire planes of the TPC, especially for the induction planes. This paper describes the characteristics and mitigation of the observed noise in the MicroBooNE detector. The MicroBooNE's single-phase LArTPC comprises two induction planes and one collection sense wire plane with a total of 8256 wires. Current induced on each TPC wire is amplified and shaped by custom low-power, low-noise ASICs immersed in the liquid argon. The digitization of the signal waveform occurs outside the cryostat. Using data from the first year of MicroBooNE operations, several excess noise sources in the TPC were identified and mitigated. The residual equivalent noise charge (ENC) after noise filtering varies with wire length and is found to be below 400 electrons for the longest wires (4.7 m). The response is consistent with the cold electronics design expectations and is found to be stable with time and uniform over the functioning channels. This noise level is significantly lower than previous experiments utilizing warm front-end electronics.

physics.ins-det↗

arXiv2017

Michel Electron Reconstruction Using Cosmic-Ray Data from the MicroBooNE LArTPC

The MicroBooNE liquid argon time projection chamber (LArTPC) has been taking data at Fermilab since 2015 collecting, in addition to neutrino beam, cosmic-ray muons. Results are presented on the reconstruction of Michel electrons produced by the decay at rest of cosmic-ray muons. Michel electrons are abundantly produced in the TPC, and given their well known energy spectrum can be used to study MicroBooNE's detector response to low-energy electrons (electrons with energies up to ~50 MeV). We describe the fully-automated algorithm developed to reconstruct Michel electrons, with which a sample of ~14,000 Michel electron candidates is obtained. Most of this article is dedicated to studying the impact of radiative photons produced by Michel electrons on the accuracy and resolution of their energy measurement. In this energy range, ionization and bremsstrahlung photon production contribute similarly to electron energy loss in argon, leading to a complex electron topology in the TPC. By profiling the performance of the reconstruction algorithm on simulation we show that the ability to identify and include energy deposited by radiative photons leads to a significant improvement in the energy measurement of low-energy electrons. The fractional energy resolution we measure improves from over 30% to ~20% when we attempt to include radiative photons in the reconstruction. These studies are relevant to a large number of analyses which aim to study neutrinos by measuring electrons produced by $\nu_e$ interactions over a broad energy range.

physics.ins-det↗

arXiv2017

Determination of muon momentum in the MicroBooNE LArTPC using an improved model of multiple Coulomb scattering

We discuss a technique for measuring a charged particle's momentum by means of multiple Coulomb scattering (MCS) in the MicroBooNE liquid argon time projection chamber (LArTPC). This method does not require the full particle ionization track to be contained inside of the detector volume as other track momentum reconstruction methods do (range-based momentum reconstruction and calorimetric momentum reconstruction). We motivate use of this technique, describe a tuning of the underlying phenomenological formula, quantify its performance on fully contained beam-neutrino-induced muon tracks both in simulation and in data, and quantify its performance on exiting muon tracks in simulation. Using simulation, we have shown that the standard Highland formula should be re-tuned specifically for scattering in liquid argon, which significantly improves the bias and resolution of the momentum measurement. With the tuned formula, we find agreement between data and simulation for contained tracks, with a small bias in the momentum reconstruction and with resolutions that vary as a function of track length, improving from about 10% for the shortest (one meter long) tracks to 5% for longer (several meter) tracks. For simulated exiting muons with at least one meter of track contained, we find a similarly small bias, and a resolution which is less than 15% for muons with momentum below 2 GeV/c. Above 2 GeV/c, results are given as a first estimate of the MCS momentum measurement capabilities of MicroBooNE for high momentum exiting tracks.

physics.ins-det↗

arXiv2017

Constraints on Large Extra Dimensions from the MINOS Experiment

We report new constraints on the size of large extra dimensions from data collected by the MINOS experiment between 2005 and 2012. Our analysis employs a model in which sterile neutrinos arise as Kaluza-Klein states in large extra dimensions and thus modify the neutrino oscillation probabilities due to mixing between active and sterile neutrino states. Using Fermilab's NuMI beam exposure of $10.56 \times 10^{20}$ protons-on-target, we combine muon neutrino charged current and neutral current data sets from the Near and Far Detectors and observe no evidence for deviations from standard three-flavor neutrino oscillations. The ratios of reconstructed energy spectra in the two detectors constrain the size of large extra dimensions to be smaller than $0.45\,μ\text{m}$ at 90% C.L. in the limit of a vanishing lightest active neutrino mass. Stronger limits are obtained for non-vanishing masses.

hep-ex↗

arXiv2016

Design and Construction of the MicroBooNE Detector

This paper describes the design and construction of the MicroBooNE liquid argon time projection chamber and associated systems. MicroBooNE is the first phase of the Short Baseline Neutrino program, located at Fermilab, and will utilize the capabilities of liquid argon detectors to examine a rich assortment of physics topics. In this document details of design specifications, assembly procedures, and acceptance tests are reported.

physics.ins-det↗

arXiv2016

A search for flavor-changing non-standard neutrino interactions using $ν_{e}$ appearance in MINOS

We report new constraints on flavor-changing non-standard neutrino interactions from the MINOS long-baseline experiment using $ν_{e}$ and $\barν_{e}$ appearance candidate events from predominantly $ν_μ$ and $\barν_μ$ beams. We used a statistical selection algorithm to separate $ν_{e}$ candidates from background events, enabling an analysis of the combined MINOS neutrino and antineutrino data. We observe no deviations from standard neutrino mixing, and thus place constraints on the non-standard interaction matter effect, $|\varepsilon_{eτ}|$, and phase, $(δ_{CP}+δ_{eτ})$, using a thirty-bin likelihood fit.

hep-ex↗

arXiv2016

Search for time-independent Lorentz violation using muon neutrino to muon antineutrino transitions in MINOS

Data from the MINOS experiment has been used to search for mixing between muon neutrinos and muon antineutrinos using a time-independent Lorentz-violating formalism derived from the Standard-Model Extension (SME). MINOS is uniquely capable of searching for muon neutrino-antineutrino mixing given its long baseline and ability to distinguish between neutrinos and antineutrinos on an event-by-event basis. Neutrino and antineutrino interactions were observed in the MINOS Near and Far Detectors from an exposure of 10.56$\times10^{20}$ protons-on-target from the NuMI neutrino-optimized beam. No evidence was found for such transitions and new, highly stringent limits were placed on the SME coefficients governing them. We place the first limits on the SME parameters $(c_{L})^{TT}_{μμ} $ and $(c_{L})^{TT}_{ττ}$ at $-8.4\times10^{-23} < (c_{L})^{TT}_{μμ} < 8.0\times10^{-23}$ and $-8.0\times10^{-23} < (c_{L})^{TT}_{ττ} < 8.4\times10^{-23}$, and the world's best limits on the $\tilde{g}^{ZT}_{μ\overlineμ}$ and $\tilde{g}^{ZT}_{τ\overlineτ}$ parameters at $|\tilde{g}^{ZT}_{μ\overlineμ}| < 3.3\times 10^{-23}$ and $|\tilde{g}^{ZT}_{τ\overlineτ}| < 3.3\times 10^{-23}$, all limits quoted at $3σ$.

hep-ex↗

arXiv2016

Convolutional Neural Networks Applied to Neutrino Events in a Liquid Argon Time Projection Chamber

We present several studies of convolutional neural networks applied to data coming from the MicroBooNE detector, a liquid argon time projection chamber (LArTPC). The algorithms studied include the classification of single particle images, the localization of single particle and neutrino interactions in an image, and the detection of a simulated neutrino event overlaid with cosmic ray backgrounds taken from real detector data. These studies demonstrate the potential of convolutional neural networks for particle identification or event detection on simulated neutrino interactions. We also address technical issues that arise when applying this technique to data from a large LArTPC at or near ground level.

physics.ins-det↗