arXiv subjects

M. Kabirnezhad

Publications and source records attributed to M. Kabirnezhad.

11 recordsLinked to original sources

arXiv2026

Single Pion Production off Free Nucleons: Analysis of Photon, Electron, Pion and Neutrino Induced Processes

In this paper, I introduce a unified model for single-pion production across photo-, electro-, and neutrino-nucleon interactions, designed to be valid over a broad kinematic range that is crucial for accelerator-based neutrino experiments. This model includes vector and axial-vector nucleon transition form factors for all excited nucleons or resonances up to 2 GeV, as well as non-resonant backgrounds, within a meson dominance framework that adheres to QCD principles and ensures unitarity. This approach guarantees accurate asymptotic behaviour at high momentum transfer and effectively addresses the transition region. Additionally, the model employs the Conserved Vector Current and Partially Conserved Axial Current relations to provide reliable predictions at very low momentum transfer, tackling challenges encountered by current neutrino experiments. The unified model facilitates a comprehensive analysis by integrating all available data from electron, photon, pion, and neutrino scattering experiments. This integration enables a detailed investigation of nucleon structure within the resonance region and is particularly valuable for probing weak interactions, where neutrino-nucleon data are limited. The combined analysis allows for the simultaneous parameterisation and constraint of the model free parameters, while quantifying associated uncertainties, thus providing a robust and reliable framework for future neutrino measurements.

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arXiv2025

Implementation of a relativistic distorted wave impulse approximation model into the NEUT event generator

We describe the implementation of a model for charged-current quasi-elastic (CCQE) neutrino-nucleus scattering in the NEUT Monte Carlo event generator. This model employs relativistic momentum distributions obtained from mean field theory and relativistic distorted waves to describe the initial and final nucleon states. Final state interactions, both elastic and inelastic, are modelled by combining distorted waves with the NEUT intranuclear cascade, offering a more accurate representation of the interactions experienced by scattered nucleons. The model and its implementation in NEUT are described in detail and benchmarked against $ν_μ$-$^{12}$C scattering cross-section measurements from T2K and MINER$ν$A, as well as $ν_μ$-$^{40}$Ar measurements from MicroBooNE. Results, including transverse kinematic imbalance variables and scattered nucleon kinematics, show improved $χ^2$ values compared to other CCQE models in NEUT. Furthermore, the model consistently predicts lower cross sections in CCQE-dominated regions, indicating potential for further refinement, such as incorporating two-body currents or the use of more advanced nucleon axial form factors consistent with lattice QCD calculations.

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arXiv2023

Single pion production in electron-proton interactions

This paper presents an extension of the MK single pion production model \cite{MK, MK2} to high hadron invariant mass ($W$) and high momentum transfer to conform to the predictions of perturbative QCD due to quark-hadron duality. New form factors for several resonant interactions and non-resonant background in the electron-nucleon cross-sections are determined taking into account the experimental data and improved evaluation techniques. Fits to electron-proton scattering data are used to calculate the vector-current form factors, and to assign uncertainties to the constrained free parameters of the model. The %hadron currents results from this work can be used to determine the vector current in the corresponding neutrino-nucleon cross-sections, which are an important input for event generators in long baseline neutrino oscillation measurements.

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arXiv2020

T2K measurements of muon neutrino and antineutrino disappearance using $3.13\times 10^{21}$ protons on target

We report measurements by the T2K experiment of the parameters $θ_{23}$ and $Δm^2_{32}$ which govern the disappearance of muon neutrinos and antineutrinos in the three-flavor PMNS neutrino oscillation model at T2K's neutrino energy and propagation distance. Utilizing the ability of the experiment to run with either a mainly neutrino or a mainly antineutrino beam, muon-like events from each beam mode are used to measure these parameters separately for neutrino and antineutrino oscillations. Data taken from $1.49 \times 10^{21}$ protons on target (POT) in neutrino mode and $1.64 \times 10^{21}$ POT in antineutrino mode are used. The best-fit values obtained by T2K were $\sin^2\left(θ_{23}\right)=0.51^{+0.06}_{-0.07} \left(0.43^{+0.21}_{-0.05}\right)$ and $Δm^2_{32}=2.47^{+0.08}_{-0.09} \left(2.50^{+0.18}_{-0.13}\right)$\evmass for neutrinos (antineutrinos). No significant differences between the values of the parameters describing the disappearance of muon neutrinos and antineutrinos were observed. An analysis using an effective two-flavor neutrino oscillation model where the sine of the mixing angle is allowed to take non-physical values larger than 1 is also performed to check the consistency of our data with the three-flavor model. Our data were found to be consistent with a physical value for the mixing angle.

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arXiv2020

Snowmass 2021 LoI: Neutrino-induced Shallow- and Deep-Inelastic Scattering

In neutrino interactions with nucleons and nuclei, Shallow Inelastic Scattering (SIS) refers to processes, dominated by non-resonant contributions, in the kinematic region where $Q^2$ is small and the invariant mass of the hadronic system, $W$, is above the pion production threshold. The extremely rich science of this complex region, poorly understood both theoretically and experimentally, encompasses the transition from interactions described in terms of hadronic degrees of freedom to interactions with quarks and gluons described by perturbative QCD. Since a large fraction of events in NOvA and DUNE, and in atmospheric neutrino measurements such as IceCube-Upgrade, KM3NeT, Super- and Hyper-Kamiokande, are from this SIS region, there is a definite need to improve our knowledge of this physics. This LoI summarizes the current understandings of the SIS physics and a series of proposals for the path to forward.

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arXiv2020

Summary of the NuSTEC Workshop on Neutrino-Nucleus Pion Production in the Resonance Region

The NuSTEC workshop held at the University of Pittsburgh in October 2019 brought theorists and experimentalists together to discuss the state of modeling and measurements related to pion production in neutrino-nucleus scattering in the kinematic region where pions are produced through both resonant and non-resonant mechanisms. Modeling of this region is of critical importance to the current and future accelerator- and atmospheric-based neutrino oscillation experiments. For the benefit of the community, links to the presentations are accompanied by annotations from the speakers highlighting significant points made during the presentations and resulting discussions.

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arXiv2020

MK single pion production model

This paper presents an update to the MK model, which was developed to describe single pion production in neutrino-nucleon interactions. Originally the MK model used the helicity amplitudes and the hadronic current form-factors of the Rein and Sehgal model. The update includes a new definition for the helicity amplitudes in the first and second resonance regions, and new vector-current form factors. Fits to electron-proton scattering data were used to determine these vector-current form factors, and to assign errors to the constrained free parameters of the model.

hep-ph↗

arXiv2019

Single pion production in neutrino-nucleon Interactions

This work represents an extension of the single pion production model proposed by D. Rein. The model consists of resonant pion production and nonresonant background contributions coming from three Born diagrams in the helicity basis. The new work includes lepton mass effects, and nonresonant interaction is described by five diagrams based on a nonlinear σ model. This work provides a full kinematic description of single pion production in the neutrino-nucleon interactions, including resonant and nonresonant interactions in the helicity basis, in order to study the interference effect.

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arXiv2019

Summary of the NuSTEC Workshop on Shallow- and Deep-Inelastic Scattering

The NuSTEC workshop (https://indico.cern.ch/event/727283) held at L'Aquila in October 2018 was devoted to neutrino-nucleus scattering in the kinematic region where hadronic systems with invariant masses above the $Δ(1232)$ resonance are produced: the so-called shallow- and deep-inelastic scattering regime. Not only is the physics in this kinematic region quite intriguing, it is also important for current and future oscillation experiments with accelerator and atmospheric neutrinos. For the benefit of the community, links to the presentations are accompanied by annotations from the speakers.

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arXiv2017

Measurement of neutrino and antineutrino oscillations by the T2K experiment including a new additional sample of $ν_e$ interactions at the far detector

The T2K experiment reports an updated analysis of neutrino and antineutrino oscillations in appearance and disappearance channels. A sample of electron neutrino candidates at Super-Kamiokande in which a pion decay has been tagged is added to the four single-ring samples used in previous T2K oscillation analyses. Through combined analyses of these five samples, simultaneous measurements of four oscillation parameters, $|Δm^2_{32}|$, $\sin^2(θ_{23})$, $\sin^2(θ_{13})$, and $δ_{CP}$ and of the mass ordering are made. A set of studies of simulated data indicates that the sensitivity to the oscillation parameters is not limited by neutrino interaction model uncertainty. Multiple oscillation analyses are performed, and frequentist and Bayesian intervals are presented for combinations of the oscillation parameters with and without the inclusion of reactor constraints on $\sin^2(θ_{13})$. When combined with reactor measurements, the hypothesis of CP conservation ($δ_{CP}$$=0$ or $π$) is excluded at 90% confidence level. The 90% confidence region for $δ_{CP}$ is [-2.95,-0.44] ([-1.47, -1.27]) for normal (inverted) ordering. The central values and 68\% confidence intervals for the other oscillation parameters for normal (inverted) ordering are $Δm^{2}_{32}=2.54\pm0.08$ ($2.51\pm0.08$) $\times 10^{-3}$ eV$^2 / c^4$ and $\sin^2(θ_{23}) = 0.55^{+0.05}_{-0.09}$ ($0.55^{+0.05}_{-0.08}$), compatible with maximal mixing. In the Bayesian analysis, the data weakly prefer normal ordering (Bayes factor 3.7) and the upper octant for $\sin^2(θ_{23})$ (Bayes factor 2.4).

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arXiv2017

Measurement of $\barν_μ$ and $ν_μ$ charged current inclusive cross sections and their ratio with the T2K off-axis near detector

We report a measurement of cross section $σ(ν_μ+{\rm nucleus}\rightarrowμ^{-}+X)$ and the first measurements of the cross section $σ(\barν_μ+{\rm nucleus}\rightarrowμ^{+}+X)$ and their ratio $R(\frac{σ(\bar ν)}{σ(ν)})$ at (anti-)neutrino energies below 1.5 GeV. We determine the single momentum bin cross section measurements, averaged over the T2K $\barν/ν$-flux, for the detector target material (mainly Carbon, Oxygen, Hydrogen and Copper) with phase space restricted laboratory frame kinematics of $θ_μ<32^\circ$ and $p_μ>$500 MeV/c. The results are $σ(\barν)=\left( 0.900\pm0.029{\rm (stat.)}\pm0.088{\rm (syst.)}\right)\times10^{-39}$ and $σ(ν)=\left( 2.41\ \pm0.022{\rm{(stat.)}}\pm0.231{\rm (syst.)}\ \right)\times10^{-39}$ in units of cm$^{2}$/nucleon and $R\left(\frac{σ(\barν)}{σ(ν)}\right)= 0.373\pm0.012{\rm (stat.)}\pm0.015{\rm (syst.)}$.

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