few-GeV Region Research Articles

A substandard candle: the low-nu method at few-GeV neutrino energies

As accelerator-based neutrino oscillation experiments improve oscillation parameter constraints with more data, control over systematic uncertainties on the incoming neutrino flux and interaction models is increasingly important. The intense beams offered by modern experiments permit a variety of options to constrain the flux using in situ “standard candle” measurements. These standard candles must use very well understood interaction processes to avoid introducing additional interaction model dependence. One option often discussed in this context is the “low-nu ” method, which is designed to isolate neutrino interactions where there is low energy-transfer to the nucleus, such that the interaction cross section is expected to be approximately constant as a function of neutrino energy. The shape of the low-energy transfer event sample can then be used to extract the flux shape. Applications of the method at high neutrino energies (many tens of GeV) are well understood. However, the applicability of the method at the lower energies of current and future few-GeV accelerator neutrino experiments remains unclear due to the presence of nuclear and form-factor effects inherent in the interaction models.In this analysis we examine the prospects for improving constraints on the accelerator neutrino fluxes in situ with the low-nu method in an experiment-independent way, using (anti)neutrino interactions on argon and hydrocarbon targets from the GENIE, NEUT, NuWro and GiBUU event generators. We begin by investigating the extent to which deviations from the constant cross-section assumption are dependent on poorly understood aspects of the neutrino interaction model. We then assess whether a low energy-transfer event sample can be confidently identified using experimentally accessible observables. We finally consider how the practicalities of reconstructing the energy spectrum of interacting neutrinos in realistic detectors might further limit the utility of low-nu flux constraints. The results show that flux constraints from the low-nu method would be severely dependent on the interaction model assumptions used in an analysis of neutrinos with energies below 5 GeV, and anti-neutrinos below at least 15 GeV. The spread of model predictions show that a low-nu analysis is unlikely to offer much improvement on typical neutrino flux uncertainties, even with a perfect detector. Notably—running counter to the assumption inherent to the low-nu method—the model-dependence increases with decreasing energy transfer for experiments in the few-GeV region.

Light dark matter in a gauged U(1)Lμ−Lτ model

As experimental null results increase the pressure on heavy weakly interacting massive particles (WIMPs) as an explanation of thermal dark matter (DM), it seems timely to explore previously overlooked regions of the WIMP parameter space. In this work we extend the minimal gauged $U(1)_{L_\mu-L_\tau}$ model studied in \cite{Bauer:2018onh} by a light (MeV-scale) vector-like fermion $\chi$. Taking into account constraints from cosmology, direct and indirect detection we find that the standard benchmark of $M_V=3 m_\chi$ for DM coupled to a vector mediator is firmly ruled out for unit DM charges. However, exploring the near-resonance region $M_V\gtrsim 2 m_\chi$ we find that this model can simultaneously explain the DM relic abundance $\Omega h^2 =0.12$ and the $(g-2)_\mu$ anomaly. Allowing for small charge hierarchies of $\lesssim\mathcal{O}(10)$, we identify a second window of parameter space in the few-GeV region, where $\chi$ can account for the full DM relic density.

Neutrino Interactions in the few-GeV region and the MiniBooNE anomaly

The MiniBooNE experiment reported results from the analysis of νe and appearance searches, which showed an excess of signal-like events at low reconstructed neutrino energies with respect to the expected background. The origin of this anomaly could reside in poorly understood neutrino interactions in the detector, leading to unaccounted backgrounds. We discuss photon emission in neutral current interactions with nucleons and nuclei, finding it insufficient to explain the observed event excess. A proposed alternative scenario in which photons arise from the radiative decay of heavy (∼ 50 MeV) sterile neutrinos produced by νµ electromagnetic and weak interactions in the detector is also considered. We have calculated the expected signal at MicroBooNE. The distinctive shape and total number of photon events from this mechanism makes its experimental investigation appealing.

Measurement of Electron Neutrino Quasielastic and Quasielasticlike Scattering on Hydrocarbon at ⟨E_{ν}⟩=3.6 GeV.

The first direct measurement of electron neutrino quasielastic and quasielasticlike scattering on hydrocarbon in the few-GeV region of incident neutrino energy has been carried out using the MINERvA detector in the NuMI beam at Fermilab. The flux-integrated differential cross sections in the electron production angle, electron energy, and Q^{2} are presented. The ratio of the quasielastic, flux-integrated differential cross section in Q^{2} for ν_{e} with that of similarly selected ν_{μ}-induced events from the same exposure is used to probe assumptions that underpin conventional treatments of charged-current ν_{e} interactions used by long-baseline neutrino oscillation experiments. The data are found to be consistent with lepton universality and are well described by the predictions of the neutrino event generator GENIE.

Neutrino-nucleus interactions in the few-GeV region

Knowledge of neutrino interaction cross sections is an important and necessary ingredient in any neutrino measurement and it is crucial to achieve the precision goals of the neutrino oscillation program, making possible new discoveries like the CP violation in the leptonic sector. We briefly review the major features of the neutrino cross sections in the few-GeV region, paying special attention to nuclear effects.

Inclusive measurements with MINERνA

MINERνA is a neutrino scattering experiment in the NuMI beamline at Fermilab designed to measure neutrino cross-sections, final states and nuclear effects on a variety of targets in the few-GeV region. MINERνA is currently running in the NuMI low energy configuration and will continue in medium energy. We present a preliminary neutrino energy spectra in three beam configurations and a preliminary comparison of iron and lead event rates.

Neutrino interactions: Challenges in the current theoretical picture

The present theoretical status of neutrino interactions in the few-GeV region is reviewed. Quasielastic scattering, pion production, photon emission and their importance for neutrino oscillation studies are discussed, making emphasis on the open questions that arise in the comparison with new experimental data.

10.1007/s11450-008-3013-4

The possibility of studying q 4 \( \bar q \) exotic baryon states by means of N(e, e’M)B reactions proceeding via an extremely simple mechanism and involving the quasielastic knockout of various mesons from a nucleon by electrons of energy in the few-GeV region is considered as a development of the previous investigations of our group. A quark microscopic formalism based on the cluster model of q 4 \( \bar q \) states, which makes it possible to determine momentum distributions of mesons in various channels of B → N + M virtual decays (in principle, these distributions can be compared with experimental data), is expounded by considering the example of the pentaquark (B = Θ+). The decay widths of the q 4 \( \bar q \) baryon states being discussed are governed by the degree of separation of quark clusters (this is a parameter of the model used). The electroproduction cross sections prove to be small because of kinematical constraints requiring that physically admissible values of the momentum ‖k‖ of the virtual meson M lie in the region where relevant amplitudes are suppressed substantially by form factors in pentaquark vertices. In particular, N (e, e′π ±)B reactions involving pion knockout furnish direct information about nonstrange components of baryon B; however, the expected cross sections for such reactions are an order of magnitude smaller than their counterparts for analogous reactions leading to the production of a pentaquark Θ+. Because of the smallness of the electroproduction cross sections, it is reasonable to consider the production of a pentaquark and other q 4 \( \bar q \) exotic states in reactions characterized by quasielastic kinematics and initiated by pions of energy in the range between about 1 and 5 GeV and in similar stripping and pickup nuclear reactions.

Potential of quasielastic meson knockout from a nucleon by high-energy electrons and pions for studying the structure of exotic excited states of a final-state baryon

The possibility of studying q4\( \bar q \) exotic baryon states by means of N(e, e’M)B reactions proceeding via an extremely simple mechanism and involving the quasielastic knockout of various mesons from a nucleon by electrons of energy in the few-GeV region is considered as a development of the previous investigations of our group. A quark microscopic formalism based on the cluster model of q4\( \bar q \) states, which makes it possible to determine momentum distributions of mesons in various channels of B → N + M virtual decays (in principle, these distributions can be compared with experimental data), is expounded by considering the example of the pentaquark (B = Θ+). The decay widths of the q4\( \bar q \) baryon states being discussed are governed by the degree of separation of quark clusters (this is a parameter of the model used). The electroproduction cross sections prove to be small because of kinematical constraints requiring that physically admissible values of the momentum ‖k‖ of the virtual meson M lie in the region where relevant amplitudes are suppressed substantially by form factors in pentaquark vertices. In particular, N (e, e′π±)B reactions involving pion knockout furnish direct information about nonstrange components of baryon B; however, the expected cross sections for such reactions are an order of magnitude smaller than their counterparts for analogous reactions leading to the production of a pentaquark Θ+. Because of the smallness of the electroproduction cross sections, it is reasonable to consider the production of a pentaquark and other q4\( \bar q \) exotic states in reactions characterized by quasielastic kinematics and initiated by pions of energy in the range between about 1 and 5 GeV and in similar stripping and pickup nuclear reactions.

NuInt05. Proceedings of the 4th International Workshop on Neutrino-Nucleus Interactions in the Few-GeV Region

NuInt05. Proceedings of the 4th International Workshop on Neutrino-Nucleus Interactions in the Few-GeV Region

Welcome to The Okayama University

On helalf of The Okayama University, we are very happy to host the Fourth International Workshop on Neutrino-Nucleus Interactions In the Few-GeV Region (NuInt05), and we would like to address a hearty welcome to all participants who have come from all over the world to discuss about “Neutrinos”.

The Gran Sasso National Laboratory

The Gran Sasso Laboratory is glad to host NuInt04 , the Third International Workshop on Neutrino-Nucleus Interactions in the Few-GeV Region , and addresses the warmest welcome to all the over a hundred participants from many countries in the World.

Results from low-energy neutrino-nucleus scattering experiments

The experimental data of neutrino-nucleus interactions in the few-GeV region are reviewed. We comment on how to test the calculations of neutrino-nucleus interactions using the existing data of electron-nucleus interactions. We also explain the kinematics of the neutrino-nucleus quasi-elastic reaction.

A gas sampling electromagnetic calorimeter using conductive plastic tubes

A prototype of gas sampling electromagnetic calorimeter with conductive plastic tubes was studied under practical conditions. An energy resolution of σ E E = 20.4 (E( GeV)) − 1 2 (%) was obtained in the few-GeV region and the spatial resolu for 4 GeV electrons was σ x = 5.4 mm for pads and σ x = 2.2 mm for strips. No appreciable effect on the energy resolution was found by magnetic field of 1 kG applied perpendicularly to the anode wire.

Model of heavy-ion collisions in the few-GeV region.

We present in detail a new mechanism by which energy can be released from a quark-gluon plasma in ultrarelativistic nucleus-nucleus collisions. In this model, fireballs are created inside the plasma via two-gluon fusion and decay outside. We assume thermal equilibrium among all plasma constituents but chemical equilibrium among the light quarks only. As an illustration, the model is applied to central ArKCl collisions at 12 GeV/nucleon. Using reasonable values for the parameters, we find that about 12% of the energy available goes into fireball formation.