arXiv subjects

H. Ray

Publications and source records attributed to H. Ray.

At least 73 records · Page 4Linked to original sources

arXiv2019

Identification of nuclear effects in neutrino-carbon interactions at low three-momentum transfer

Two different nuclear-medium effects are isolated using a low three-momentum transfer subsample of neutrino-carbon scattering data from the MINERvA neutrino experiment. The observed hadronic energy in charged-current $ν_μ$ interactions is combined with muon kinematics to permit separation of the quasielastic and $Δ$(1232) resonance processes. First, we observe a small cross section at very low energy transfer that matches the expected screening effect of long-range nucleon correlations. Second, additions to the event rate in the kinematic region between the quasielastic and $Δ$ resonance processes are needed to describe the data. The data in this kinematic region also has an enhanced population of multi-proton final states. Contributions predicted for scattering from a nucleon pair have both properties; the model tested in this analysis is a significant improvement but does not fully describe the data. We present the results as a double-differential cross section to enable further investigation of nuclear models. Improved description of the effects of the nuclear environment are required by current and future neutrino oscillation experiments.

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arXiv2019

First Constraint on Coherent Elastic Neutrino-Nucleus Scattering in Argon

Coherent elastic neutrino-nucleus scattering (CEvNS) is the dominant neutrino scattering channel for neutrinos of energy $E_ν< 100$ MeV. We report a limit for this process using data collected in an engineering run of the 29 kg CENNS-10 liquid argon detector located 27.5 m from the Oak Ridge National Laboratory Spallation Neutron Source (SNS) Hg target with $4.2\times 10^{22}$ protons on target. The dataset yielded $< 7.4$ observed CEvNS events implying a cross section for the process, averaged over the SNS pion decay-at-rest flux, of $<3.4 \times 10^{-39}$ cm$^{2}$, a limit within twice the Standard Model prediction. This is the first limit on CEvNS from an argon nucleus and confirms the earlier CsI non-standard neutrino interaction constraints from the collaboration. This run demonstrated the feasibility of the ongoing experimental effort to detect CEvNS with liquid argon.

hep-ex↗

arXiv2019

Measurement of $\barν_μ$ charged-current single $π^{-}$ production on hydrocarbon in the few-GeV region using MINERvA

The antineutrino scattering channel $\barν_μ \,\text{CH} \rightarrow μ^{+} \,π^{-} \,X$(nucleon(s)) is analyzed in the incident energy range 1.5 to 10 GeV using the MINERvA detector at Fermilab. Differential cross sections are reported as functions of $μ^{+}$ momentum and production angle, $π^{-}$ kinetic energy and production angle, and antineutrino energy and squared four-momentum transfer. Distribution shapes are generally reproduced by simulations based on the GENIE, NuWro, and GiBUU event generators, however GENIE (GiBUU) overestimates (underestimates) the cross-section normalizations by 8% (10%). Comparisons of data with the GENIE-based reference simulation probe conventional treatments of cross sections and pion intranuclear rescattering. The distribution of non-track vertex energy is used to decompose the signal sample into reaction categories, and cross sections are determined for the exclusive reactions $μ^{+} π^{-} n$ and $ μ^+ π^{-} p$. A similar treatment applied to the published MINERvA sample $\barν_μ \,\text{CH} \rightarrow μ^{+} \,π^{0} \,X$(nucleon(s)) has determined the $μ^{+} π^{0} n$ cross section, and the latter is used with $σ(π^{-} n)$ and $σ(π^{-} p)$ to carry out an isospin decomposition of $\barν_μ$-induced CC($π$). The ratio of magnitudes and relative phase for isospin amplitudes $A_{3}$ and $A_{1}$ thereby obtained are: $R^{\barν} = 0.99 \pm 0.19$ and $ϕ^{\barν} = 93^{\circ} \pm 7^{\circ}$. Our results are in agreement with bubble chamber measurements made four decades ago.

hep-ex↗

arXiv2019

Antineutrino Charged-Current reactions on Hydrocarbon with Low Momentum Transfer

We report on multinucleon effects in low momentum transfer ($< 0.8$ GeV/c) anti-neutrino interactions on plastic (CH) scintillator. These data are from the 2010-2011 antineutrino phase of the MINERvA experiment at Fermilab. The hadronic energy spectrum of this inclusive sample is well described when a screening effect at low energy transfer and a two-nucleon knockout process are added to a relativistic Fermi gas model of quasielastic, $Δ$ resonance, and higher resonance processes. In this analysis, model elements introduced to describe previously published neutrino results have quantitatively similar benefits for this antineutrino sample. We present the results as a double-differential cross section to accelerate investigation of alternate models for antineutrino scattering off nuclei.

hep-ex↗

arXiv2018

Search for pair and single production of vectorlike quarks in final states with at least one $Z$ boson decaying into a pair of electrons or muons in $pp$ collision data collected with the ATLAS detector at $\sqrt{s} = 13$ TeV

A search for vectorlike quarks is presented, which targets their decay into a $Z$ boson and a third-generation Standard Model quark. In the case of a vectorlike quark $T$ ($B$) with charge $+2/3e$ ($-1/3e$), the decay searched for is $T \rightarrow Zt$ ($B \rightarrow Zb$). Data for this analysis were taken during 2015 and 2016 with the ATLAS detector at the Large Hadron Collider and correspond to an integrated luminosity of 36.1 fb$^{-1}$ of $pp$ collisions at $\sqrt{s} = 13$ TeV. The final state used is characterized by the presence of $b$-tagged jets, as well as a $Z$ boson with high transverse momentum, which is reconstructed from a pair of opposite-sign same-flavor leptons. Pair and single production of vectorlike quarks are both taken into account and are each searched for using optimized dileptonic exclusive and trileptonic inclusive event selections. In these selections, the high scalar sum of jet transverse momenta, the presence of high-transverse-momentum large-radius jets, as well as - in the case of the single-production selections - the presence of forward jets are used. No significant excess over the background-only hypothesis is found and exclusion limits at 95% confidence level allow masses of vectorlike quarks of $m_T > 1030$ GeV ($m_T > 1210$ GeV) and $m_B > 1010$ GeV ($m_B > 1140$ GeV) in the singlet (doublet) model. In the case of 100% branching ratio for $T\rightarrow Zt$ ($B\rightarrow Zb$), the limits are $m_T > 1340$ GeV ($m_B > 1220$ GeV). Limits at 95% confidence level are also set on the coupling to Standard Model quarks for given vectorlike quark masses.

hep-ex↗

arXiv2018

Reducing model bias in a deep learning classifier using domain adversarial neural networks in the MINERvA experiment

We present a simulation-based study using deep convolutional neural networks (DCNNs) to identify neutrino interaction vertices in the MINERvA passive targets region, and illustrate the application of domain adversarial neural networks (DANNs) in this context. DANNs are designed to be trained in one domain (simulated data) but tested in a second domain (physics data) and utilize unlabeled data from the second domain so that during training only features which are unable to discriminate between the domains are promoted. MINERvA is a neutrino-nucleus scattering experiment using the NuMI beamline at Fermilab. $A$-dependent cross sections are an important part of the physics program, and these measurements require vertex finding in complicated events. To illustrate the impact of the DANN we used a modified set of simulation in place of physics data during the training of the DANN and then used the label of the modified simulation during the evaluation of the DANN. We find that deep learning based methods offer significant advantages over our prior track-based reconstruction for the task of vertex finding, and that DANNs are able to improve the performance of deep networks by leveraging available unlabeled data and by mitigating network performance degradation rooted in biases in the physics models used for training.

physics.data-an↗

arXiv2018

Measurement of Quasielastic-Like Neutrino Scattering at $\left< E_ν\right> \sim 3.5$~ GeV on a Hydrocarbon Target

MINERvA presents a new analysis of neutrino induced quasielastic-like interactions in a hydrocarbon tracking target. We report a double-differential cross section using the muon transverse and longitudinal momentum. In addition, differential cross sections as a function of the square of the four-momentum transferred and the neutrino energy are calculated using a quasielastic hypothesis. Finally, an analysis of energy deposited near the interaction vertex is presented. These results are compared to modified GENIE predictions as well as a NuWro prediction. All results use a dataset produced by $3.34\times10^{20}$ protons on target creating a neutrino beam with a peak energy of approximately 3.5 GeV

hep-ex↗

arXiv2018

Significant Excess of ElectronLike Events in the MiniBooNE Short-Baseline Neutrino Experiment

The MiniBooNE experiment at Fermilab reports results from an analysis of $ν_e$ appearance data from $12.84 \times 10^{20}$ protons on target in neutrino mode, an increase of approximately a factor of two over previously reported results. A $ν_e$ charged-current quasielastic event excess of $381.2 \pm 85.2$ events ($4.5 σ$) is observed in the energy range $200<E_ν^{QE}<1250$~MeV. Combining these data with the $\bar ν_e$ appearance data from $11.27 \times 10^{20}$ protons on target in antineutrino mode, a total $ν_e$ plus $\bar ν_e$ charged-current quasielastic event excess of $460.5 \pm 99.0$ events ($4.7 σ$) is observed. If interpreted in a two-neutrino oscillation model, $ν_μ \rightarrow ν_e$, the best oscillation fit to the excess has a probability of $21.1\%$, while the background-only fit has a $χ^2$ probability of $6 \times 10^{-7}$ relative to the best fit. The MiniBooNE data are consistent in energy and magnitude with the excess of events reported by the Liquid Scintillator Neutrino Detector (LSND), and the significance of the combined LSND and MiniBooNE excesses is $6.0 σ$. A two-neutrino oscillation interpretation of the data would require at least four neutrino types and indicate physics beyond the three neutrino paradigm.Although the data are fit with a two-neutrino oscillation model, other models may provide better fits to the data.

hep-ex↗

arXiv2018

Cross sections for neutrino and antineutrino induced pion production on hydrocarbon in the few-GeV region using MINERvA

Separate samples of charged-current pion production events representing two semi-inclusive channels $ν_μ$-CC($π^{+}$) and $\barν_μ$-CC($π^{0}$) have been obtained using neutrino and antineutrino exposures of the MINERvA detector. Distributions in kinematic variables based upon $μ^{\pm}$-track reconstructions are analyzed and compared for the two samples. The differential cross sections for muon production angle, muon momentum, and four-momentum transfer $Q^2$, are reported, and cross sections versus neutrino energy are obtained. Comparisons with predictions of current neutrino event generators are used to clarify the role of the $Δ(1232)$ and higher-mass baryon resonances in CC pion production and to show the importance of pion final-state interactions. For the $ν_μ$-CC($π^{+}$) ($\barν_μ$-CC($π^{0}$)) sample, the absolute data rate is observed to lie below (above) the predictions of some of the event generators by amounts that are typically 1-to-2 $σ$. However the generators are able to reproduce the shapes of the differential cross sections for all kinematic variables of either data set.

hep-ex↗

arXiv2018

Measurement of the muon anti-neutrino double-differential cross section for quasi-elastic scattering on hydrocarbon at~$E_ν\sim 3.5$ GeV

We present double-differential measurements of anti-neutrino quasi-elastic scattering in the MINERvA detector. This study improves on a previous single differential measurement by using updated reconstruction algorithms and interaction models, and provides a complete description of observed muon kinematics in the form of a double-differential cross section with respect to muon transverse and longitudinal momentum. We include in our signal definition zero-meson final states arising from multi-nucleon interactions and from resonant pion production followed by pion absorption in the primary nucleus. We find that model agreement is considerably improved by a model tuned to MINERvA inclusive neutrino scattering data that incorporates nuclear effects such as weak nuclear screening and two-particle, two-hole enhancements.

hep-ex↗

arXiv2018

First Measurement of Monoenergetic Muon Neutrino Charged Current Interactions

We report the first measurement of monoenergetic muon neutrino charged current interactions. MiniBooNE has isolated 236 MeV muon neutrino events originating from charged kaon decay at rest ($K^+ \rightarrow μ^+ ν_μ$) at the NuMI beamline absorber. These signal $ν_μ$-carbon events are distinguished from primarily pion decay in flight $ν_μ$ and $\overlineν_μ$ backgrounds produced at the target station and decay pipe using their arrival time and reconstructed muon energy. The significance of the signal observation is at the 3.9$σ$ level. The muon kinetic energy, neutrino-nucleus energy transfer ($ω=E_ν-E_μ$), and total cross section for these events is extracted. This result is the first known-energy, weak-interaction-only probe of the nucleus to yield a measurement of $ω$ using neutrinos, a quantity thus far only accessible through electron scattering.

hep-ex↗

arXiv2018

COHERENT Collaboration data release from the first observation of coherent elastic neutrino-nucleus scattering

This release includes data and information necessary to perform independent analyses of the COHERENT result presented in Akimov et al., arXiv:1708.01294 [nucl-ex]. Data is shared in a binned, text-based format, including both "signal" and "background" regions, so that counts and associated uncertainties can be quantitatively calculated for the purpose of separate analyses. This document describes the included information and its format, offering some guidance on use of the data. Accompanying code examples show basic interaction with the data using Python.

nucl-ex↗

arXiv2018

COHERENT 2018 at the Spallation Neutron Source

The primary goal of the COHERENT collaboration is to measure and study coherent elastic neutrino-nucleus scattering (CEvNS) using the high-power, few-tens-of-MeV, pulsed source of neutrinos provided by the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL). The COHERENT collaboration reported the first detection of CEvNS [Akimov:2017ade] using a CsI[Na] detector. At present the collaboration is deploying four detector technologies: a CsI[Na] scintillating crystal, p-type point-contact germanium detectors, single-phase liquid argon, and NaI[Tl] crystals. All detectors are located in the neutron-quiet basement of the SNS target building at distances 20-30 m from the SNS neutrino source. The simultaneous measurement in all four COHERENT detector subsystems will test the $N^2$ dependence of the cross section and search for new physics. In addition, COHERENT is measuring neutrino-induced neutrons from charged- and neutral-current neutrino interactions on nuclei in shielding materials, which represent a non-negligible background for CEvNS as well as being of intrinsic interest. The Collaboration is planning as well to look for charged-current interactions of relevance to supernova and weak-interaction physics. This document describes concisely the COHERENT physics motivations, sensitivity, and next plans for measurements at the SNS to be accomplished on a few-year timescale.

physics.ins-det↗

arXiv2018

Measurement of Total and Differential Cross Sections of Neutrino and Antineutrino Coherent $π^\pm$ Production on Carbon

Neutrino induced coherent charged pion production on nuclei, $\overlineν_μA\toμ^\pmπ^\mp A$, is a rare inelastic interaction in which the four-momentum squared transfered to the nucleus is nearly zero, leaving it intact. We identify such events in the scintillator of MINERvA by reconstructing |t| from the final state pion and muon momenta and by removing events with evidence of energetic nuclear recoil or production of other final state particles. We measure the total neutrino and antineutrino cross sections as a function of neutrino energy between 2 and 20 GeV and measure flux integrated differential cross sections as a function of $Q^2$, $E_π$ and $θ_π$. The $Q^2$ dependence and equality of the neutrino and anti-neutrino cross-sections at finite $Q^2$ provide a confirmation of Adler's PCAC hypothesis.

hep-ex↗

arXiv2018

Measurement of the antineutrino to neutrino charged-current interaction cross section ratio in MINERvA

We present measurements of the neutrino and antineutrino total charged-current cross sections on carbon and their ratio using the MINERvA scintillator-tracker. The measurements span the energy range 2-22 GeV and were performed using forward and reversed horn focusing modes of the Fermilab low-energy NuMI beam to obtain large neutrino and antineutrino samples. The flux is obtained using a sub-sample of charged-current events at low hadronic energy transfer along with precise higher energy external neutrino cross section data overlapping with our energy range between 12-22 GeV. We also report on the antineutrino-neutrino cross section ratio, Rcc, which does not rely on external normalization information. Our ratio measurement, obtained within the same experiment using the same technique, benefits from the cancellation of common sample systematic uncertainties and reaches a precision of 5% at low energy. Our results for the antineutrino-nucleus scattering cross section and for Rcc are the most precise to date in the energy range $E_ν <$ 6GeV.

hep-ex↗

arXiv2017

Dark Matter Search in a Proton Beam Dump with MiniBooNE

The MiniBooNE-DM collaboration searched for vector-boson mediated production of dark matter using the Fermilab 8 GeV Booster proton beam in a dedicated run with $1.86 \times 10^{20}$ protons delivered to a steel beam dump. The MiniBooNE detector, 490~m downstream, is sensitive to dark matter via elastic scattering with nucleons in the detector mineral oil. Analysis methods developed for previous MiniBooNE scattering results were employed, and several constraining data sets were simultaneously analyzed to minimize systematic errors from neutrino flux and interaction rates. No excess of events over background was observed, leading to a 90\% confidence limit on the dark-matter cross section parameter, $Y=ε^2α_D(m_χ/m_V)^4 \lesssim10^{-8}$, for $α_D=0.5$ and for dark-matter masses of $0.01<m_χ<0.3~\mathrm{GeV}$ in a vector portal model of dark matter. This is the best limit from a dedicated proton beam dump search in this mass and coupling range and extends below the mass range of direct dark matter searches. These results demonstrate a novel and powerful approach to dark matter searches with beam dump experiments.

hep-ex↗

arXiv2017

Observation of Coherent Elastic Neutrino-Nucleus Scattering

The coherent elastic scattering of neutrinos off nuclei has eluded detection for four decades, even though its predicted cross-section is the largest by far of all low-energy neutrino couplings. This mode of interaction provides new opportunities to study neutrino properties, and leads to a miniaturization of detector size, with potential technological applications. We observe this process at a 6.7-sigma confidence level, using a low-background, 14.6-kg CsI[Na] scintillator exposed to the neutrino emissions from the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory. Characteristic signatures in energy and time, predicted by the Standard Model for this process, are observed in high signal-to-background conditions. Improved constraints on non-standard neutrino interactions with quarks are derived from this initial dataset.

nucl-ex↗

arXiv2017

Measurement of neutral-current $K^+$ production by neutrinos using MINERvA

Neutral-current production of $K^{+}$ by atmospheric neutrinos is a background in searches for the proton decay $p \rightarrow K^{+} \barν$. Reactions such as $νp \rightarrow νK^{+} Λ$ are indistinguishable from proton decays when the decay products of the $Λ$ are below detection threshold. Events with $K^{+}$ are identified in MINERvA by reconstructing the timing signature of a $K^{+}$ decay at rest. A sample of 201 neutrino-induced neutral-current $K^{+}$ events is used to measure differential cross sections with respect to the $K^{+}$ kinetic energy, and the non-$K^{+}$ hadronic visible energy. An excess of events at low hadronic visible energy is observed relative to the prediction of the NEUT event generator. Good agreement is observed with the cross section prediction of the GENIE generator. A search for photons from $π^{0}$ decay, which would veto a neutral-current $K^{+}$ event in a proton decay search, is performed, and a 2$σ$ deficit of detached photons is observed relative to the GENIE prediction.

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