arXiv subjects

Artur M. Ankowski

Publications and source records attributed to Artur M. Ankowski.

At least 37 records · Page 2Linked to original sources

arXiv2015

Missing energy and the measurement of the CP-violating phase in neutrino oscillations

In the next generation of long-baseline neutrino oscillation experiments, aiming to determine the charge-parity violating phase $δ_{CP}$ in the appearance channel, fine-grained time-projection chambers are expected to play an important role. In this Letter, we analyze an influence of realistic detector capabilities on the $δ_{CP}$ sensitivity for a setup similar to that of the Deep Underground Neutrino Experiment. We find that the effect of the missing energy, carried out by undetected particles, is sizable. Although the reconstructed neutrino energy can be corrected for the missing energy, the accuracy of such procedure has to exceed 20\%, to avoid a sizable bias in the extracted $δ_{CP}$ value.

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arXiv2015

Comparison of the calorimetric and kinematic methods of neutrino energy reconstruction in disappearance experiments

To be able to achieve their physics goals, future neutrino-oscillation experiments will need to reconstruct the neutrino energy with very high accuracy. In this work, we analyze how the energy reconstruction may be affected by realistic detection capabilities, such as energy resolutions, efficiencies, and thresholds. This allows us to estimate how well the detector performance needs to be determined a priori in order to avoid a sizable bias in the measurement of the relevant oscillation parameters. We compare the kinematic and calorimetric methods of energy reconstruction in the context of two muon-neutrino disappearance experiments operating in different energy regimes. For the calorimetric reconstruction method, we find that the detector performance has to be estimated with a ~10% accuracy to avoid a significant bias in the extracted oscillation parameters. On the other hand, in the case of kinematic energy reconstruction, we observe that the results exhibit less sensitivity to an overestimation of the detector capabilities.

hep-ph↗

arXiv2015

Charged-current quasielastic scattering of muon antineutrino and neutrino in the MINERvA experiment

One of the largest sources of systematic uncertainties in ongoing neutrino-oscillation measurements is the description of nuclear effects. Its considerable reduction is expected thanks to the dedicated studies of (anti)neutrino-nucleus interactions in the MINERvA experiment. In this article, the calculations within the spectral function approach are compared to the charged-current quasielastic cross sections reported from MINERvA. The obtained results show that the effect of final-state interactions on the (anti)muon kinematics plays pivotal role in reproducing the experimental data.

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arXiv2015

Estimate of the theoretical uncertainty of the cross sections for nucleon knockout in neutral-current neutrino-oxygen interactions

Free nucleons propagating in water are known to produce gamma rays, which form a background to the searches for diffuse supernova neutrinos and sterile neutrinos carried out with Cherenkov detectors. As a consequence, the process of nucleon knockout induced by neutral-current quasielastic interactions of atmospheric (anti)neutrinos with oxygen needs to be under control at the quantitative level in the background simulations of the ongoing and future experiments. In this paper, we provide a quantitative assessment of the uncertainty associated with the theoretical description of the nuclear cross sections, estimating it from the discrepancies between the predictions of different models.

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arXiv2015

Improving the accuracy of neutrino energy reconstruction in charged-current quasielastic scattering off nuclear targets

We report the results of a theoretical study of quasielastic electron and neutrino interactions with carbon. Our approach takes into account the effects of final-state interactions between the struck nucleon and the residual nucleus, neglected in the impulse approximation, through a generalization of the spectral function formalism. The calculated electron-scattering cross sections turn out to be in very good agreement with the available data over a broad kinematical region. The impact of nuclear effects on the reconstruction of neutrino energy in charged-current quasielastic processes is also studied, and the results of our approach are compared to the predictions of the relativistic Fermi gas model, routinely employed in most Monte Carlo simulations. Finally, we discuss the limitations of the existing procedure for energy reconstruction and propose a new, improved, one. At energy ~600 MeV, we observe a sizable difference between neutrino and antineutrino scattering, important for the measurements of charge-parity symmetry violation. Our analysis suggests that a reliable determination of neutrino energy can only be obtained from models validated by a systematic comparison to the available electron-scattering data.

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arXiv2013

Neutron knockout in neutral-current neutrino-oxygen interactions

The ongoing and future searches for diffuse supernova neutrinos and sterile neutrinos carried out with large water-Cherenkov detectors require a precise determination of the backgrounds, especially those involving gamma rays. Of great importance, in this context, is the process of neutron knockout through neutral-current scattering of atmospheric neutrinos on oxygen. Nuclear reinteractions of the produced neutron may in fact lead to the production of gamma rays of energies high enough to mimic the processes of interest. In this Letter, we focus on the kinematical range suitable for simulations of atmospheric-neutrino interactions and provide the neutron-knockout cross sections computed using the formalism based on realistic nuclear spectral function. The role of the strange-quark contribution to the neutral-current axial form factor is also analyzed. Based on the available experimental information, we give an estimate of the associated uncertainty.

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arXiv2013

Consistent analysis of neutral- and charged-current (anti)neutrino scattering off carbon

Good understanding of the cross sections for (anti)neutrino scattering off nuclear targets in the few-GeV energy region is a prerequisite for the correct interpretation of results of ongoing and planned oscillation experiments. To clarify a possible source of disagreement between recent measurements of the cross sections on carbon, we analyze the available data within an approach based on the realistic spectral function of carbon, treating neutral-current elastic (NCE) and charged-current quasielastic (CCQE) processes on equal footing. We show that the axial mass from the shape analysis of the MiniBooNE data is in good agreement with the results reported by the BNL E734 and NOMAD Collaborations. However, the combined analysis of the NCE and CCQE data does not seem to support the contribution of multinucleon final states being large enough to explain the normalization of the MiniBooNE-reported cross sections.

hep-ph↗

arXiv2012

Consistent analysis of neutral- and charged-current neutrino scattering off carbon

Background: Good understanding of the cross sections for (anti)neutrino scattering off nuclear targets in the few-GeV energy region is a prerequisite for correct interpretation of results of ongoing and planned oscillation experiments. Purpose: Clarify possible source of disagreement between recent measurements of the cross sections on carbon. Method: Nuclear effects in (anti)neutrino scattering off carbon nucleus are described using the spectral function approach. The effect of two- and multi-nucleon final states is accounted for by applying an effective value of the axial mass, fixed to 1.23 GeV. Neutral-current elastic (NCE) and charged-current quasielastic (CCQE) processes are treated on equal footing. Results: The differential and total cross sections for the energy ranging from a few hundreds of MeV to 100 GeV are obtained and compared to the available data from the BNL E734, MiniBooNE, and NOMAD experiments. Conclusions: Nuclear effects in NCE and CCQE scattering seem to be very similar. Within the spectral function approach, the axial mass from the shape analysis of the MiniBooNE data is in good agreement with the results reported by the BNL E734 and NOMAD Collaborations. However, the combined analysis of NCE and CCQE data does not seem to support the contribution of multi-nucleon final states being large enough to explain the normalization of the MiniBooNE-reported cross sections.

nucl-th↗

arXiv2012

Gamma-ray production in neutral-current neutrino-oxygen interactions at energies above 200 MeV

We report the results of a calculation of the neutrino- and antineutrino-induced gamma-ray production cross section for oxygen target. Our analysis is focused on the kinematical region of neutrino energy larger than ~200MeV, in which single-nucleon knockout is known to be the dominant reaction mechanism. The numerical results have been obtained using a realistic model of the target spectral function, extensively tested against electron-nucleus scattering data. We find that at neutrino energy 600 MeV the fraction of neutral-current interactions leading to emission of gamma-rays of energy larger than 6 MeV is ~41%, and that the contribution of the p_{3/2} state is overwhelming.

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arXiv2012

Analysis of gamma-ray production in neutral-current neutrino-oxygen interactions at energies above 200 MeV

It has long been recognized that observation of gamma rays originating from nuclear deexcitation can be exploited to identify neutral-current neutrino-nucleus interactions in water-Cherenkov detectors. We report the results of a calculation of the neutrino- and antineutrino-induced gamma-ray production cross section for oxygen target. Our analysis is focused on the kinematical region of neutrino energy larger than ~200 MeV, in which single-nucleon knockout is known to be the dominant reaction mechanism. The numerical results have been obtained using for the first time a realistic model of the target spectral function, extensively tested against electron-nucleus scattering data. We find that at neutrino energy 600 MeV the fraction of neutral-current interactions leading to emission of gamma-rays of energy larger than 6 MeV is ~41%, and that the contribution of the p_3/2 state is overwhelming.

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arXiv2011

Electroweak nuclear response at moderate momentum transfer

We discuss the convergence of the expansion of the nuclear electroweak current in powers of |k|/M, where M is the nucleon mass and k denotes either the momentum transfer or the momentum of the struck nucleon. We have computed the electron and neutrino scattering cross sections off uniform nuclear matter at equilibrium density using correlated wave functions and the cluster expansion formalism. The results of our work suggest that the proposed approach provides accurate estimates of the measured electron scattering cross sections. On the other hand, the description of the current based on the widely used leading-order approximation does not appear to be adequate, even at momentum transfer as low as 300 MeV.

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arXiv2010

Analysis of the Q^2-dependence of charged-current quasielastic processes in neutrino-nucleus interactions

We discuss the observed disagreement between the Q^2 distributions of neutrino-nucleus quasielastic events, measured by a number of recent experiments, and the predictions of Monte Carlo simulations based on the relativistic Fermi gas model. The results of our analysis suggest that these discrepancies are likely to be ascribable to both the breakdown of the impulse approximation and the limitations of the Fermi gas description. Several issues related to the extraction of the Q^2 distributions from the experimental data are also discussed, and new kinematical variables, which would allow for an improved analysis, are proposed.

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arXiv2009

Nuclear effects in proton decay

An experimental observation of proton decay would be a spectacular proof of grand unification. Currently, the best constraint on the proton lifetime for the p->e+ pi0 decay channel, coming from the Super-Kamiokande experiment, reaches 8*10^33 years. To improve the measurement, much bigger detectors should be constructed. Moreover, a better description of the bound-nucleon states and of the propagation of the proton-decay products through nuclear matter have to be developed. In this article special attention is paid to the argon nucleus because a liquid argon detector is a promising candidate for the future large apparatus.

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arXiv2008

Spectral functions of argon and calcium

Precise knowledge of the cross sections for neutrino interactions with nuclei is important not only for existing experiments but also for development of future detectors. When momentum transferred to the nucleus by the probe is high enough, the impulse approximation is valid, i.e. the nucleus can be described as composed of independent nucleons and the interaction happens between neutrino and a single bound nucleon. The cross section of the nucleus is then expressed as an integral of the free cross section (modified by the off-shell effect) folded with the so-called spectral function, describing the distribution of nucleon momenta and energies. I present results obtained for the approximate spectral functions of argon and calcium. The accuracy of the approach is verified by comparison with a broad spectrum of precise electron-scattering data for the calcium target. Some of these data lie in the kinematical region corresponding to neutrino interactions what indirectly shows that a similar level of accuracy is achieved for neutrinos. The calculated Ar(nu_mu,mu) cross section is significantly lower than the one predicted within the Fermi gas model.

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arXiv2008

Breakdown of the impulse approximation and its consequences: the low-Q^2 problem

Neutrino scattering data and the standard calculations of the cross section show a discrepancy in the low-Q^2 (four-momentum transfer squared) region. The calculations rely on the assumption, called the impulse approximation, that the nucleus the neutrino scatters off can be described as a collection of independent nucleons and therefore only one nucleon takes part in the interaction. It is known from electron scattering that such picture is valid only when transferred momentum |q|>400 MeV/c. For lower |q|'s, the nucleus is probed with a lower spatial resolution and a few nucleons are involved in the scattering, so the use of the impulse approximation is unjustified. It means that the standard calculations of the cross sections are unreliable for |q|<400 MeV/c. I show that the contribution of low-momentum interactions to the quasielastic neutrino cross section cannot be reduced below ~19% by any selection of the beam energy in the few-GeV region. Moreover, low-Q^2 neutrino events happen only when transferred momentum is low too. Hence the discrepancy in the low-Q^2 region is caused by the inappropriate description of low-|q| interactions in the models commonly used in Monte Carlo simulations.

nucl-th↗

arXiv2008

Construction of spectral functions for medium nuclei

This article is aimed at improving the description of lepton-nucleus interactions in the sub-GeV energy range. Approximate spectral functions for oxygen, calcium, and argon are constructed and used to obtain the electron cross sections in a given scattering angle. Comparison with a sample of available experimental data shows satisfactory agreement. Discrepancy between the presented model and the systematic computations available for oxygen [O. Benhar et al., Phys. Rev. D 72, 053005 (2005)] is also found to be very small. Analysis of appropriate kinematical regions leads to the conclusion that the obtained argon spectral function should describe well neutrino scattering in the 800-MeV energy region. Several approximations used in the model are critically reviewed. All the details needed to implement the presented approach in Monte Carlo simulations are given.

nucl-th↗

arXiv2007

Spectral functions for medium-sized nuclei

The spectral functions for calcium and argon are constructed. It is verified that their predictions for the quasielastic electron-nucleus cross sections in the energy range ~1 GeV agree with the data. The argon spectral function is then used to obtain the quasielastic neutrino-nucleus cross section.

nucl-th↗

arXiv2006

Argon spectral function and neutrino interactions

The argon spectral function is constructed and applied to neutrino-argon cross section computations in the plane wave impulse approximation with the Pauli blocking final state interaction effect taken into account. The approximations of the construction method are critically analyzed using the example of oxygen for which more detailed computations are available. An effective description of nucleus based on the information contained in a spectral function is proposed. It is demonstrated that its predictions are close to those obtained from the complete spectral function. The effective description can be easily applied in Monte Carlo event generators.

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