arXiv subjects

U. Mosel

Publications and source records attributed to U. Mosel.

At least 19 recordsLinked to original sources

arXiv2024

In-medium changes of nucleon cross sections tested in neutrino-induced reactions

Historically studied in the context of heavy-ion collisions, the extent to which free nucleon-nucleon cross sections are modified in-medium remains undetermined by these data sets. Therefore, we investigate the impact of NN in-medium modifications on neutrino-nucleus cross section predictions using the GiBUU transport model. We find that including an in-medium lowering of the NN cross section and density dependence on $\Delta$ excitation improves agreement with MicroBooNE neutrino-argon scattering data. This is observed for both proton and neutral pion spectra in charged-current muon neutrino and neutral-current single pion production datasets. The impact of collision broadening of the $\Delta$ resonance is also investigated. The absence of $\Delta$ broadening is slightly favored, but the larger uncertainties on the pion production data prevent definitive conclusions.

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arXiv2023

Lepton-induced reactions on nuclei in a wide kinematical regime

Inclusive differential cross sections for various $e A$ and $\nu A$ reactions are analyzed within the GiBUU theoretical framework and code. The treatment of electron-nuclus reactions has been significantly improved by implementing a parametrized description of electron-nucleon interactions for a nucleon. Using the momentum of a nucleon inside the Fermi sea the electron-nucleon cross sections are then Lorentz-boosted to obtain the electron structure functions for nuclei. The neutrino structure functions are obtained from the ones for electrons by a transformation that involves the axial formfactors and kinematical factors that account for the difference of vector and axial currents. Special emphasis is put on analyzing data from various different experiments in different neutrino energy regimes with one and the same theoretical input.

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arXiv2022

Dilepton Decay of Low-mass $ρ$ Mesons

The HADES collaboration has extracted dilepton mass spectra for $π^-$ induced reactions on the proton from a comparison of data taken on C and CH$_2$ targets. The spectra were interpreted in terms of different versions of vector meson dominance. Here we present results obtained from the theory and generator GiBUU. We first check the subtraction procedure used and then discuss the obtained mass spectra for the proton target. We point out that any conclusions on the version of VMD requires the knowledge of the $ρ$ spectral function in the interesting mass region.

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arXiv2021

Dilepton production in microscopic transport theory with in-medium $ρ$-meson spectral function

We use the microscopic GiBUU transport model to calculate dilepton ($e^+e^-$) production in heavy-ion collisions at SIS18 energies focusing on the effect of collisional broadening of the $ρ$-meson. The collisional width of the $ρ$-meson at finite temperature and baryon density in nuclear matter is calculated on the basis of the collision integral of the GiBUU model. A systematic comparison with HADES data on dilepton production in heavy-ion collisions is performed. The collisional broadening of the $ρ$ improves the agreement between theory and experiment for the dilepton invariant-mass distributions near the $ρ$ pole mass and for the excess radiation in Au+Au at $1.23 A$ GeV. We furthermore show that some remaining underprediction of the experimental dilepton spectra in C+C at $1 A$ GeV and Au+Au at $1.23 A$ GeV at intermediate invariant masses $0.2-0.4$ GeV can be accounted for by adjusting the $pn$ bremsstrahlung cross section in a way to agree with the inclusive dilepton spectrum from $dp$ collisions at $1.25 A$ GeV.

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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.

hep-ph↗

arXiv2020

Comment on "Comparison of optical potential for nucleons and $Δ$ resonances" by Arie Bodek and Tejin Cai

In \cite{Bodek:2020wbk} Bodek and Cai have tried to extract the potentials for nucleons and $Δ$ resonances from electron-nucleus inclusive scattering data. They find that the $Δ$ potential is considerably more attractive than that of the nucleons. This result is at variance with the results of a multitude of analyses of (e,A) and ($γA$) interactions, performed about 35 years ago.

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arXiv2019

Cross Sections for A(e,e')X Reactions

Recent JLAB measurements of inclusive (e,A) cross sections as a function of outgoing lepton momentum may provide information on the nucleon spectral function in targets that will be relevant for the planned DUNE neutrino long-baseline experiment. They also provide an important testing ground for neutrino generators. We have therefore used the transport theoretical framework and code GiBUU to calculate the cross sections for the targets C, Ar and Ti. We compare the calculations with the experimental data. The overall agreement is good. Relatively small discrepancies appear mainly on the low-electronenergy side of the QE-peak where QE and 2p2h excitation processes overlap.

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arXiv2019

Addendum: Muon-neutrino-induced charged current pion production

This short paper is an addendum to a recent publication on charged current neutrino-induced pion production (Phys.\ Rev.\ C96 (2017) no.1, 015503). It presents comparisons of pion production cross sections measured at the T2K near detector for a CH target.

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arXiv2018

Muon-neutrino-induced charged current cross section without pions: Theoretical analysis

We calculate the charged current cross sections obtained at the T2K near detector for $ν_μ$-induced events without pions in the final state. The method used is quantum-kinetic transport theory. Results are shown first, as a benchmark, for electron inclusive cross sections on $^{12}$C and $^{16}$O to be followed with a detailed comparison with the data measured by the T2K collaboration on C$_8$H$_8$ and H$_2$O targets. The contribution of 2p2h processes is found to be relevant mostly for backwards angles; their theoretical uncertainties are within the experimental uncertainties. Particular emphasis is then put on a discussion of events in which pions are first created, but then reabsorbed. Their contribution is found to be essential at forward angles.

hep-ex↗

arXiv2017

Muon-neutrino-induced charged current pion production on nuclei

[Background] Long-Baseline experiments such as T2K, NOvA or the planned Deep Underground Neutrino Experiment (DUNE) require theoretical descriptions of the complete event in a neutrino-nucleus reaction. Since nuclear targets are used this requires a good understanding of neutrino-nucleus interactions. [Purpose] One of the dominant reaction channels in neutrino-nucleus interactions is pion production. This paper aims for a coherent view on all charged current charged pion production data that are avaible from the experiments MiniBooNE, the near detector experiment at T2K and MINERvA. [Methods] Pion production is treated through excitations of nucleon resonances, including background terms, and deep inelastic scattering. The final state interactions of the produced pions are described within the Giessen-Boltzmann-Uehling-Uhlenbeck (GiBUU) implementation of quantum-kinetic transport theory. [Results] Results are given for MiniBooNE, the near detector experiment at T2K and for MINERvA. While the theoretical results for MiniBooNE differ from the data both in shape and magnitude, their agreement both with the T2K and the MINERvA data is good for all pion and lepton observables. Predictions for pion spectra are shown for MicroBooNE and NOvA. [Conclusions] Based on the GiBUU model of lepton-nucleus interactions a consistent, good theoretical description of CC charged pion production data from the T2K ND and the MINERvA experiments is possible, without any parameter tunes. The MiniBooNE data cannot be reproduced.

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arXiv2016

Neutrino-Induced Reactions on Nuclei

Background: Long-baseline experiments such as the planned Deep Underground Neutrino Experiment (DUNE) require theoretical descriptions of the complete event in a neutrino-nucleus reaction. Since nuclear targets are used this requires a good understanding of neutrino-nucleus interactions. Purpose: Develop a consistent theory and code framework for the description of lepton-nucleus interactions that can be used to describe not only inclusive cross sections, but also the complete final state of the reaction. Methods: The Giessen-Boltzmann-Uehling-Uhlenbeck (GiBUU) implementation of quantum-kinetic transport theory is used, with improvements in its treatment of the nuclear ground state and of 2p2h interactions. For the latter an empirical structure function from electron scattering data is used as a basis. Results: Results for electron-induced inclusive cross sections are given as a necessary check for the overall quality of this approach. The calculated neutrino-induced inclusive double-differential cross sections show good agreement with data from neutrino- and antineutrino reactions for different neutrino flavors at MiniBooNE and T2K. Inclusive double-differential cross sections for MicroBooNE, NOvA, MINERvA and LBNF/DUNE are given. Conclusions: Based on the GiBUU model of lepton-nucleus descriptions a good theoretical description of inclusive electron-, neutrino- and antineutrino-nucleus data over a wide range of energies, different neutrino flavors and different experiments is now possible. Since no tuning is involved this theory and code should be reliable also for new energy regimes and target masses. \end{description}

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arXiv2016

Mass dependence and isospin dependence of short-range correlated pairs

The target-mass number dependence of nucleon-nucleon pairs with short-range correlations is explored in a physically transparent geometrical model within a zero-range approximation. The observed $A$ dependence of 2-nucleon ejection cross sections in $(e,e')$ reactions is found to reflect the mass dependence of nuclear density distributions. A parametrization of this $A$ dependence is given. The $A$ dependence of proton-proton vs.\ proton-neutron pairs relative to $^{12}$C is also analyzed in this model. It can be understood using simple combinatorics without any additional isospin dependence.

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arXiv2016

$2π$ production in the Giessen coupled-channel model

We present a coupled-channel Lagrangian approach (GiM) to describe the $πN \to πN$, $2πN$ scattering in the resonance energy region. The $2πN$ production has been significantly improved by using the isobar approximation with $σN$ and $πΔ(1232)$ in the intermediate state. The three-body unitarity is maintained up to interference pattern between the isobar subchannels. The scattering amplitudes are obtained as a solution of the Bethe-Salpeter equation in the $K$ matrix approximation. As a first application we perform a partial wave analysis of the $πN \to πN$, $π^0π^0 N$ reactions in the Roper resonance region. We obtain $R_{σN}(1440)=27^{+4}_{-9}$\,\% and $R_{σN}(1440)=12^{+5}_{-3}$\,\% for the $σN$ and $πΔ$ decay branching ratios of $N^*(1440)$ respectively. The extracted $πN$ inelasticities and reaction amplitudes are consistent with the results from other groups.

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arXiv2015

Rôle of the pion electromagnetic form factor in the $Δ(1232) \to γ^\ast N$ timelike transition

The $Δ(1232) \to γ^\ast N$ magnetic dipole form factor ($G_M^\ast$) is described here within a new covariant model that combines the valence quark core together with the pion cloud contributions. The pion cloud term is parameterized by two terms: one connected to the pion electromagnetic form factor, the other to the photon interaction with intermediate baryon states. The model can be used in studies of pp and heavy ion collisions. In the timelike region this new model improves the results obtained with a constant form factor model fixed at its value at zero momentum transfer. At the same time, and in contrast to the Iachello model, this new model predicts a peak for the transition form factor at the expected position, i.e. at the $ρ$ mass pole. We calculate the decay of the $Δ\to γN$ transition, the Dalitz decay ($Δ\to e^+ e^- N$), and the $Δ$ mass distribution function. The impact of the model on dilepton spectra in pp collisions is also discussed.

hep-ph↗

arXiv2014

Many-Body Interactions of Neutrinos with Nuclei - Observables

Background: The total inclusive cross sections obtained for quasielastic (QE) scattering in the Mini Booster Neutrino Experiment (MiniBooNE) are significantly larger than those calculated by all models based on the impulse approximation and using the world average value for the axial mass of $M_A \approx 1 \GeV$. This discrepancy has led to various, quite different explanations in terms of increased axial masses, changes in the functional form of the axial form factor, increased vector strength in nuclei, and initial two-particle interactions. This is disconcerting since the neutrino energy reconstruction depends on the reaction mechanism. Purpose: We investigate whether exclusive observables, such as nucleon knock-out, can be used to distinguish between the various proposed reaction mechanisms. We determine the influence of 2p-2h excitations on the energy reconstruction. Method: We use the Giessen Boltzmann--Uehling--Uhlenbeck (GiBUU) model to predict numbers and spectra of knock-out nucleons. The model is extended by incorporating a simple, but realistic treatment of initial 2p-2h excitations. Results: We show numbers and spectra of knock-out nucleons and show their sensitivity to the presence of 2p-2h initial excitations. We also discuss the influence of 2p-2h excitations on the neutrino energy reconstruction. Conclusions: 2p-2h excitations do lead to an increase in the number $n$ of knock-out nucleons for $n \ge 2$ while only the $n=1$ knock-out remains a clean signal of true QE scattering. The spectra of knock-out nucleons do also change, but their qualitative shape remains as before. In the energy reconstruction 2p-2h interactions lead to a downward shift of the reconstructed energy; this effect of 2p-2h excitations disappears at higher energies because the 2p-2h influence is spread out over a wider energy range.

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arXiv2014

Reaction Mechanisms at MINER$ν$A

The MINER$ν$A experiment investigates neutrino interactions with nucleons needed for an understanding of electroweak interactions of hadrons. Since nuclear targets are being used many-body effects may affect the extracted cross sections and the energy reconstruction. The latter is essential for the extraction of neutrino oscillation properties. We investigate the influence of nuclear effects on neutrino interaction cross sections and make predictions for charged current quasielastic (QE) scattering, nucleon-knock-out and pion- and kaon-production on a CH target. The Giessen Boltzmann--Uehling--Uhlenbeck (GiBUU) model is used for the description of neutrino-nucleus reactions. Integrated and differential cross sections for inclusive neutrino scattering, QE processes and particle production for the MINER$ν$A neutrino flux are calculated. The influence of final state interactions on the identification of these processes is discussed. In particular, energy and $Q^2$ reconstruction for the MINER$ν$A flux are critically examined. The $Q^2$ dependence of the inclusive cross sections is found to be sensitive to the energy reconstruction. Cut-offs in flux distributions have a large effect. Final state interactions affect the pion kinetic energy spectra significantly and increase the kaon cross sections by cross feeding from other channels.

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arXiv2013

Pion production in the T2K experiment

Background: Pion production gives information on the axial form factors of nucleon resonances. It also introduces a noticeable background to quasi-elastic measurements on nuclear targets and thus has a significant impact on precision studies of neutrino oscillation parameters. Purpose: To clarify neutrino-induced pion production on nucleons and nuclei. Method: The Giessen Boltzmann--Uehling--Uhlenbeck (GiBUU) model is used for the description of neutrino-nucleus reactions. Results: Theoretical results for differential cross sections for the T2K neutrino flux at the ND280 detector and integrated cross sections as a function of neutrino energy are given. Two sets of pion production data on elementary targets are used as inputs to obtain limits for pion production in neutrino-nucleus reactions. Conclusions: Pion production in the T2K ND280 detector can help to narrow down the uncertainties in the elementary pion production cross sections. It can also give valuable information on the nucleon-Delta axial form factor.

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