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Bhuyan, B.

Publications and source records attributed to Bhuyan, B..

At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Neutron detector response modeling in NOvA

Neutrons can present a significant challenge for neutrino experiments in which energy reconstruction is critical. With the ability to escape detection completely and with a weak correlation between their kinetic energy and any eventual energy deposition, it is difficult to fully account for neutrons produced in neutrino interactions. This in turn leads to significant model dependence when evaluating neutron-related systematic uncertainties. The NOvA experiment is a long-baseline neutrino oscillation experiment with a high-statistics sample of antineutrino data collected by its near detector. We report an excess relative to data of simulated neutron candidates with low energy depositions when using standard Geant4 physics lists. The simulation excess is traced to an overabundance of secondary photons produced from interactions of neutrons with kinetic energy greater than \SI{20}{\mega\eV}. Improved agreement with data is obtained by applying the data-driven neutron-on-carbon \menate model for neutrons between \SI{20}{\mega\eV} and ${\sim}$\SI{100}{\mega\eV}. With \menate, the residual oversimulation is more uniform across the calorimetric neutron energy spectrum, suggesting possible overproduction of primary neutrons by the GENIE neutrino interaction generator. These results motivate the adoption of \menate-supplemented Geant4 simulation as the nominal simulation in the production of future \nova simulation.

Abubakar, S.β†—
DOE OSTI2025

Joint neutrino oscillation analysis from the T2K and NOvA experiments

The landmark discovery that neutrinos have mass and can change type (or flavour) as they propagateβ€”a process called neutrino oscillationβ€”has opened up a rich array of theoretical and experimental questions being actively pursued today. Neutrino oscillation remains the most powerful experimental tool for addressing many of these questions, including whether neutrinos violate charge-parity (CP) symmetry, which has possible connections to the unexplained preponderance of matter over antimatter in the Universe. Oscillation measurements also probe the mass-squared differences between the different neutrino mass states (Ξ”$m^2$), whether there are two light states and a heavier one (normal ordering) or vice versa (inverted ordering), and the structure of neutrino mass and flavour mixing. Here we carry out the first joint analysis of datasets from NOvA and T2K, the two currently operating long-baseline neutrino oscillation experiments (hundreds of kilometres of neutrino travel distance), taking advantage of our complementary experimental designs and setting new constraints on several neutrino sector parameters. This analysis provides new precision on the $Ξ”m_{32}^2$ mass difference, finding $-2.43_{βˆ’0.03}^{+0.04}$ x $10^{-13}$ $\textrm{eV}^2$ in the normal ordering and $-2.43^{+0.03}_{-0.04}$ x $10^{-13}$ $\textrm{eV}^2$ in the inverted ordering, as well as a 3Οƒ interval on Ξ΄ CP of [βˆ’1.38Ο€, 0.30Ο€] in the normal ordering and [βˆ’0.92Ο€, βˆ’0.04Ο€] in the inverted ordering. The data show no strong preference for either mass ordering, but notably, if inverted ordering were assumed true within the three-flavour mixing model, then our results would provide evidence of CP symmetry violation in the lepton sector.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Monte Carlo method for constructing confidence intervals with unconstrained and constrained nuisance parameters in the NOvA experiment

Measuring observables to constrain models using maximum-likelihood estimation is fundamental to many physics experiments. Wilks' theorem provides a simple way to construct confidence intervals on model parameters, but it only applies under certain conditions. These conditions, such as nested hypotheses and unbounded parameters, are often violated in neutrino oscillation measurements and other experimental scenarios. Monte Carlo methods can address these issues, albeit at increased computational cost. In the presence of nuisance parameters, however, the best way to implement a Monte Carlo method is ambiguous. Furthermore, this paper documents the method selected by the NOvA experiment, the profile construction. It presents the toy studies that informed the choice of method, details of its implementation, and tests performed to validate it. It also includes some practical considerations which may be of use to others choosing to use the profile construction.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Search for 𝐢⁒𝑃-Violating Neutrino Nonstandard Interactions with the NOvA Experiment

This Letter reports a search for charge-parity (𝐢⁒𝑃) symmetry violating nonstandard interactions (NSI) of neutrinos with matter using the NOvA Experiment, and examines their effects on the determination of the standard oscillation parameters. Data from 𝜈 πœ‡ ⁑($\bar{𝜈}$ πœ‡ ) β†’ 𝜈 πœ‡ ⁑($\bar{𝜈}$ πœ‡ ) and 𝜈 πœ‡ ⁑($\bar{𝜈}$ πœ‡ ) β†’ 𝜈 𝑒 ⁑( $\bar{𝜈}$ 𝑒 ) oscillation channels are used to measure the effect of the NSI parameters πœ– π‘’β’πœ‡ and πœ– π‘’β’πœ . With 90% CL the magnitudes of the NSI couplings are constrained to be |πœ– π‘’β’πœ‡ | ≲0.3 and |πœ– π‘’β’πœ | ≲ 0.4. A degeneracy at |πœ– π‘’β’πœ | β‰ˆ 1.8 is reported, and we observe that the presence of NSI limits sensitivity to the standard 𝐢⁒𝑃 phase 𝛿 𝐢⁒𝑃 .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Measurement of the double-differential cross section of muon-neutrino charged-current interactions with low hadronic energy in the NOvA Near Detector

The NOvA collaboration reports cross-section measurements for $\nu_{\mu}$ charged-current interactions with low hadronic energy (maximum kinetic energy of 250 MeV for protons and 175 MeV for pions) in the NOvA Near Detector. The results are presented as a double-differential cross section as a function of the direct observables of the final-state muon kinematics. Results are also presented as a single-differential cross section as a function of the derived square of the four-momentum transfer, $Q^{2}$, and as a function of the derived neutrino energy. The data correspond to an accumulated 8.09$\times10^{20}$ protons-on-target (POT) in the neutrino mode of the NuMI beam, with a narrow band of neutrino energies peaked at 1.8 GeV. The analysis provides a sample of neutrino-nucleus interactions with an enhanced fraction of quasi-elastic and two-particle-two-hole (2p2h) interactions. This enhancement allows quantitative comparisons with various nuclear models. We find strong disagreement between data and theory-based models in various regions of the muon kinematic phase space, especially in the forward muon direction.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Expanding neutrino oscillation parameter measurements in NOvA using a Bayesian approach

NOvA is a long-baseline neutrino oscillation experiment that measures oscillations in charged-current Ξ½ ΞΌ β†’ Ξ½ ΞΌ (disappearance) and Ξ½ ΞΌ β†’ Ξ½ e (appearance) channels, and their antineutrino counterparts, using neutrinos of energies around 2 GeV over a distance of 810 km. In this work we reanalyze the dataset first examined in our previous paper [] using an alternative statistical approach based on Bayesian Markov chain Monte Carlo. We measure oscillation parameters consistent with the previous results. We also extend our inferences to include the first NOvA measurements of the reactor mixing angle ΞΈ 13 , where we find 0.071 ≀ sin 2 2 ΞΈ 13 ≀ 0.107 , and the Jarlskog invariant, where we observe no significant preference for the C P -conserving value J = 0 over values favoring C P violation. We use these results to examine the effects of constraints from short-baseline measurements of ΞΈ 13 using antineutrinos from nuclear reactors when making NOvA measurements of ΞΈ 23 . Our long-baseline measurement of ΞΈ 13 is shown to be consistent with the reactor measurements, supporting the general applicability and robustness of the Pontecorvo-Maki-Nakagawa-Sakata framework for neutrino oscillations. Published by the American Physical Society 2024

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Measurement of branching-fraction ratios and CP asymmetries in BΒ± β†’ DCPΒ±KΒ± decays at Belle and Belle II

Abstract We report results from a study ofB Β± β†’ DK Β± decays followed byDdecaying to theCP-even final stateK + K βˆ’ and CP-odd final state$$ {K}_S^0{\pi}^0 $$ K S 0 Ο€ 0 , whereDis an admixture ofD 0 and$$ {\overline{D}}^0 $$ D Β― 0 states. These decays are sensitive to the Cabibbo-Kobayashi-Maskawa unitarity-triangle angleΟ• 3 . The results are based on a combined analysis of the final data set of 772Γ—10 6 $$ B\overline{B} $$ B B Β― pairs collected by the Belle experiment and a data set of 198Γ—10 6 $$ B\overline{B} $$ B B Β― pairs collected by the Belle II experiment, both in electron-positron collisions at the Ξ₯(4S) resonance. We measure the CP asymmetries to be$$ \mathcal{A} $$ A CP+ = (+12.5Β±5.8Β±1.4)% and$$ \mathcal{A} $$ A CPβˆ’ = (βˆ’16.7Β±5.7Β±0.6)%, and the ratios of branching fractions to be$$ \mathcal{R} $$ R CP+ = 1.164Β±0.081Β±0.036 and$$ \mathcal{R} $$ R CPβˆ’ = 1.151Β±0.074Β±0.019. The first contribution to the uncertainties is statistical, and the second is systematic. The asymmetries$$ \mathcal{A} $$ A CP+ and$$ \mathcal{A} $$ A CPβˆ’ have similar magnitudes and opposite signs; their difference corresponds to 3.5 standard deviations. From these values we calculate 68.3% confidence intervals of (8.5 Β° <Ο• 3 < 16.5 Β° ) or (84.5 Β° <Ο• 3 < 95.5 Β° ) or (163.3 Β° <Ο• 3 < 171.5 Β° ) and 0.321 B< 0.465.

Physics↗
DOE OSTI2023

Search for $ {\textrm{B}}_{\textrm{s}}^0 $ β†’ β„“ βˆ“ Ο„ Β± with the semi-leptonic tagging method at Belle

We present a search for the lepton-flavor-violating decays ${B}_s^0$ β†’ β„“ βˆ“ Ο„ Β± , where β„“ = e, ΞΌ, using the full data sample of 121 fb -1 collected at the Ξ₯(5S) resonance with the Belle detector at the KEKB asymmetric-energy e + e - collider. We use ${B}_s^0{\overline{B}}_s^0$ events in which one ${B}_s^0$ meson is reconstructed in a semileptonic decay mode and the other in the signal mode. We find no evidence for (${B}_s^0$ β†’ β„“ βˆ“ Ο„ Β± decays and set upper limits on their branching fractions at 90% confidence level as $\mathcal{B}$(${B}_s^0$ β†’ e βˆ“ Ο„ Β± ) < 14 Γ— 10 -4 and $\mathcal{B}$ (${B}_s^0$ β†’ ΞΌ βˆ“ Ο„ Β± ) < 7.3 Γ— 10 -4 . Our result represents the first upper limit on the ${B}_s^0$ β†’ e βˆ“ Ο„ Β± decay rate.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Search for lepton-flavor-violating Ο„ decays into a lepton and a vector meson using the full Belle data sample

Charged-lepton-flavor-violation is predicted in several new physics scenarios. We update the analysis of Ο„ lepton decays into a light charged lepton (β„“ = e Β± or ΞΌ Β± ) and a vector meson (V 0 = ρ 0 , Ξ¦, Ο‰, K *0 , or $\overline{K}$ *0 ) using 980 fb -1 of data collected with the Belle detector at the KEKB collider. No significant excess of such signal events is observed, and thus 90% credibility level upper limits are set on the Ο„ β†’ β„“V 0 branching fractions in the range of (1.7–4.3) Γ— 10 -8 . These limits are improved by 30% on average from the previous results.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Two-particle angular correlations in e + e - collisions to hadronic final states in two reference coordinates at Belle

We present the analysis of two-particle angular correlations using coordinate systems defined with the conventional beam axis and the event thrust axis. We propose the latter as a good representation for the correlation structure interpretation in the e + e - collision system. The e + e - collisions to hadronic final states at center-of-mass energies of $\sqrt{s}$ = 10.52 GeV and 10.58 GeV are recorded by the Belle detector at KEKB. In this paper, results on the first dataset are supplementary to the previous Belle publication [1]. At the same time, the latter is the first two-particle correlation measurement at collision energy on the Ξ₯(4S) resonance and is sensitive to its decay products. Measurements are reported as a function of the charged-particle multiplicity. Finally, a qualitative understanding of the correlation structure is discussed using a combination of Monte Carlo simulations and experimental data.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Measurement of two-photon decay width of Ο‡ c2 (1 P ) in Ξ³Ξ³ β†’ Ο‡ c2 (1 P ) β†’ J/ψγ at Belle

We report the measurement of the two-photon decay width of Ο‡ c2 (1P) in two-photon processes at the Belle experiment. We analyze the process Ξ³Ξ³ β†’ Ο‡ c2 (1P) β†’ J/ψγ, J/ψ β†’ β„“ + β„“ - (β„“ = e or ΞΌ) using a data sample of 971 fb -1 collected with the Belle detector at the KEKB e + e - collider. In this analysis, the product of the two-photon decay width of Ο‡ c2 (1P) and the branching fraction is determined to be ${\Gamma}_{\gamma \gamma}({\chi}_{c2}(1P))\mathcal{B}({\chi}_{c2}(1P)\to J/\psi \gamma) \mathcal{B} (J/\psi \to {\ell}^{+}{\ell}^{-})=$ 14.8 Β± 0.3(stat.) Β± 0.7(syst.) eV, which corresponds to Ξ“ Ξ³Ξ³ (Ο‡ c2 (1P)) = 653 Β± 13(stat.) Β± 31(syst.) Β± 17(B.R.) eV, where the third uncertainty is from $\mathcal{B}$ (Ο‡ c2 (1P) β†’ J/ψγ) and $\mathcal{B}$ (J/ψ β†’ β„“ + β„“ - ).

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗