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Krzysztof M. Graczyk

Publications and source records attributed to Krzysztof M. Graczyk.

At least 37 records · Page 2Linked to original sources

Resonant superalgebras for supergravity

Considering supergravity theory is a natural step in the development of gravity models. This paper follows the ``algebraic`` path and constructs possible extensions of the Poincaré and Anti-de-Sitter algebras, which inherit their basic commutation structure. Previously achieved results of this type are fragmentary and show only a limited fraction of possible algebraic realizations. Our paper presents the newly obtained symmetry algebras, evaluated within an efficient pattern-based computational method of generating the so-called 'resonating' algebraic structures. These supersymmetric extensions of algebras, going beyond the Poincaré and Anti-de Sitter ones, contain additional bosonic generators $Z_{ab}$ (Lorentz-like), and $U_a$ (translational-like) added to the standard Lorentz generator $J_{ab}$ and translation generator $P_{a}$. Our analysis includes all cases up to two fermionic supercharges, $Q_α$ and $Y_α$. The delivered plethora of superalgebras includes few past results and offers a vastness of new examples. The list of the cases is complete and contains all superalgebras up to two of Lorentz-like, translation-like, and supercharge-like generators $(JP+Q)+(ZU+Y)=JPZU+QY$. In the latter class, among $667$ founded superalgebras, the $264$ are suitable for direct supergravity construction. For each of them, one can construct a unique supergravity model defined by the Lagrangian. As an example, we consider one of the algebra configurations and provide its Lagrangian realization.

hep-th↗

Model dependence of the polarization asymmetries in weak pion production off the nucleon

The work presents the studies of the polarization observables in the single pion production (SPP) induced by the interaction of the muon neutrino (antineutrino) with nucleons. The SPP cross-sections and spin asymmetries are computed within two phenomenological models. One is basing on the nonlinear sigma model \cite{Hernandez:2007qq}; the other has origin in linear sigma model~\cite{Fogli:1979cz}. Firstly, we show that the final nucleon polarization and target spin asymmetries are good observables to obtain information about the $C_5^A$ axial form factor. Secondly, we demonstrate that the nucleon polarization and the target spin asymmetries are sensitive to the relative phase between resonance and nonresonance amplitudes. We conclude that the polarization of the final nucleon and the target spin asymmetry are promising observables for testing SPP models, including studies of the axial content of $Δ(1232)$ resonance and unitarization procedures.

hep-ph↗

Predicting Porosity, Permeability, and Tortuosity of Porous Media from Images by Deep Learning

Convolutional neural networks (CNN) are utilized to encode the relation between initial configurations of obstacles and three fundamental quantities in porous media: porosity ($φ$), permeability $k$, and tortuosity ($T$). The two-dimensional systems with obstacles are considered. The fluid flow through a porous medium is simulated with the lattice Boltzmann method. It is demonstrated that the CNNs are able to predict the porosity, permeability, and tortuosity with good accuracy. With the usage of the CNN models, the relation between $T$ and $φ$ has been reproduced and compared with the empirical estimate. The analysis has been performed for the systems with $φ\in (0.37,0.99)$ which covers five orders of magnitude span for permeability $k \in (0.78, 2.1\times 10^5)$ and tortuosity $T \in (1.03,2.74)$.

physics.comp-ph↗

Spin asymmetries in quasielastic charged current neutrino-nucleon scattering

The work concerns the quasielastic charged current neutrino-neutron and antineutrino-proton interactions. Single, double, and triple spin asymmetries are computed and analyzed. The spin asymmetries are sensitive to the axial form factor of the nucleon. In particular, the target-recoil double spin asymmetry and the lepton-target-recoil triple spin asymmetry depend strongly on the axial form factor of the nucleon. Indeed, the sign and shape of these components depend on the axial mass parameter. All the asymmetries, except the lepton polarization, are observables well suited to study the nonstandard interactions described by the second class current contribution.

hep-ph↗

Spin asymmetry in single pion production induced by weak interactions of neutrinos with polarized nucleons

The single pion production (SPP) in the charged-current neutrino (antineutrino) scattering off the polarized nucleon is discussed. The spin asymmetry is predicted within two approaches. The spin polarizations of the target nucleon that are longitudinal and perpendicular to the neutrino momentum are considered. It is shown, in several examples, that information about the SPP dynamics coming from the spin asymmetry is complementary to information obtained from measurements of spin averaged cross section. Indeed, the spin asymmetry is sensitive to the nonresonance background description of the SPP model. For the normal polarization of the target, the spin asymmetry is given by the interference between the resonance and the nonresonance contributions.

hep-ph↗

Nucleon axial form factor from a Bayesian neural-network analysis of neutrino-scattering data

The Bayesian approach for feed-forward neural networks has been applied to the extraction of the nucleon axial form factor from the neutrino-deuteron scattering data measured by the Argonne National Laboratory (ANL) bubble chamber experiment. This framework allows to perform a model-independent determination of the axial form factor from data.. When the low $0.05 < Q^2 < 0.10$ GeV$^2$ data is included in the analysis, the resulting axial radius disagrees with available determinations. Furthermore, a large sensitivity to the corrections from the deuteron structure is obtained. In turn, when the low-$Q^2$ region is not taken into account, with or without deuteron corrections, no significant deviations from the dipole ansatz have been observed. A more accurate determination of the nucleon axial form factor requires new precise measurements of neutrino-induced quasielastic scattering on hydrogen and deuterium.

hep-ph↗

Polarization Transfer in Weak Pion Production off the Nucleon

Polarization transfer (PT) observables in the single pion production induced by the charged current interaction of the neutrino with the nucleon are examined. The polarization components of the final nucleon and the charged lepton are calculated within two models for the pion production. The predictions are made for neutrino energy of the order of 1~GeV as well as for the T2K energy distribution. It is demonstrated that the PT observables, the degree of polarization and the polarization components of outgoing fermions, are sensitive on assumptions about the nonresonant background model. In particular it is shown that the normal components of the polarization of the outgoing nucleon and the lepton are determined by the interference between the resonant (RES) and nonresonant (NB) amplitudes. Moreover the sign of the normal component of the polarization of the charged lepton is fixed by the relative sign between the RES and the NB amplitudes.

hep-ph↗

NuWro Monte Carlo generator of neutrino interactions - first electron scattering results

NuWro Monte Carlo generator of events is presented. It is a numerical environment containing all necessary ingredients to simulate interactions of neutrinos with nucleons and nuclei in realistic experimental situation in wide neutrino energy range. It can be used both for data analysis as well as studies of nuclear effects in neutrino interactions. The first results and functionalities of eWro - module of NuWro dedicated to electron nucleus scattering - are also presented.

hep-ph↗

The Proton Radius from Bayesian Inference

The methods of Bayesian statistics are used to extract the value of the proton radius from the elastic $ep$ scattering data in a model independent way. To achieve that goal a large number of parametrizations (equivalent to neural network schemes) are considered and ranked by their conditional probability $P(\mathrm{parametrization}\,|\,\mathrm{data})$ instead of using the minimal error criterion. As a result the most probable proton radii values ($r_E^p=0.899\pm 0.003$ fm, $r_M^p=0.879\pm 0.007$ fm) are obtained and systematic error due to freedom in the choice of parametrization is estimated. Correcting the data for the two photon exchange effect turns out to be important to obtain the agreement between the $r_E^p$ and $r_M^p$ values. The results disagree with recent muonic atom measurements.

hep-ph↗

Electroweak Single Pion Production and Form Factors of the Δ(1232) Resonance

We extend and review our analysis of the nucleon \to Δ(1232) transition electroweak form factors from Ref. [1]. New fit of the Δ(1232) vector form factors to electron-proton scattering F_2 structure function is introduced as well, leading to results different from the popular parametrization of Ref. [2]. A clear model dependence of the extracted parameters emerges. Fit to neutrino scattering data is performed in all available isospin channels. The resulting axial mass is M_{AΔ}=0.85^{+0.09}_{-0.08} (GeV) and $C_5^A(0) = 1.10^{+0.15}_{-0.14}. The latter value is in accordance with Goldberger-Treiman relation as long as the deuteron effects are included.

hep-ph↗

Applications of Neural Networks in Hadron Physics

The Bayesian approach for the feed-forward neural networks is reviewed. Its potential for usage in hadron physics is discussed. As an example of the application the study of the the two-photon exchange effect is presented. We focus on the model comparison, the estimation of the systematic uncertainties due to the choice of the model, and the over-fitting. As an illustration the predictions of the cross sections ratio $d σ(e^+ p\to e^+ p)/d σ(e^- p\to e^- p)$ are given together with the estimate of the uncertainty due to the parametrization choice.

hep-ph↗

Electroweak Form Factors of the $Δ$(1232) Resonance

Nucleon $\to Δ(1232)$ transition electroweak form factors are discussed in a single pion production model with nonresonant background terms originating from a chiral perturbation theory. Fits to electron-proton scattering $F_2$ as well as neutrino scattering bubble chamber experimental data are performed. Both $ν$-proton and $ν$-neutron channel data are discussed in a unified statistical model. A new parametrization of the $N\toΔ(1232)$ vector form factors is proposed. Fit to neutrino scattering data gives axial mass $M_{AΔ}=0.85{+0.09}{-0.08}\;$(GeV) and $C_5^A(0) = 1.10{+0.15}{-0.14}$ in accordance with Goldberger-Treiman relation as long as deuteron nuclear effects are considered.

hep-ph↗

Comparison of Neural Network and Hadronic Model Predictions of Two-Photon Exchange Effect

Predictions for the two-photon exchange (TPE) correction to unpolarized $ep$ elastic cross section, obtained within two different approaches, are confronted and discussed in detail. In the first one the TPE correction is extracted from experimental data by applying the Bayesian neural network (BNN) statistical framework. In the other the TPE is given by box diagrams, with the nucleon and the $P_{33}$ resonance as the hadronic intermediate states. Two different form factor parametrizations for both the proton and the $P_{33}$ resonance are taken into consideration. Proton form factors are obtained from the global fit of the full model (with the TPE correction) to the unpolarized cross section data. Predictions of both methods agree well in the intermediate $Q^2$ range, $(1,3)$ GeV$^2$. Above $Q^2=3$ GeV$^2$ the agreement is on $2σ$ level. Below $Q^2=1$ GeV$^2$ the consistency between both approaches is broken. The values of the proton radius extracted within both models are given. In both cases predictions for VEPP-3 experiment have been obtained and confronted with the preliminary experimental results.

hep-ph↗

Relevance of Two Boson Exchange Effect in Quasi-Elastic Charged Current Neutrino-Nucleon Interaction

Two boson exchange (TBE) correction to the cross section for the quasi-elastic charged current $νn$ and $\barν p$ scattering is evaluated. The TBE is given by $Wγ$ box diagrams. The calculations are performed for 1 GeV neutrinos. The averaged TBE correction is of the order of $2\div4 %$ (with respect to Born contribution) in the case of $ν_e$ and $\barν_e$ and $1\div2 %$ in the case of $ν_μ$ and $\barν_μ$. The impact of the TBE effect on the systematic discrepancy between the $ν_e$ and $ν_μ$ cross sections is discussed.

hep-ph↗

Extraction of Axial Mass and Strangeness Values from the MiniBooNE Neutral Current Elastic Cross Section Measurement

Results of the analysis of the MiniBooNE experiment data for the neutral current elastic neutrino scattering off the $CH_{2}$ target with the NuWro Monte Carlo generator are presented. Inclusion in the NuWro the two body current contribution leads to the axial mass value $M_A = 1.10^{+0.13}_{-0.15}$ GeV consistent with the older evaluations based on the neutrino-deuteron scattering data. The strange quark contribution to the nucleon spin is estimated with the value $g_A^s = -0.4^{+0.5}_{-0.3}$.

hep-ph↗

Two-Photon Exchange Effect Studied with Neural Networks

An approach to the extraction of the two-photon exchange (TPE) correction from elastic $ep$ scattering data is presented. The cross section, polarization transfer (PT), and charge asymmetry data are considered. It is assumed that the TPE correction to the PT data is negligible. The form factors and TPE correcting term are given by one multidimensional function approximated by the feed forward neural network (NN). To find a model-independent approximation the Bayesian framework for the NNs is adapted. A large number of different parametrizations is considered. The most optimal model is indicated by the Bayesian algorithm. The obtained fit of the TPE correction behaves linearly in epsilon but it has a nontrivial Q2 dependence. A strong dependence of the TPE fit on the choice of parametrization is observed.

hep-ph↗

Neural Network Parameterizations of Electromagnetic Nucleon Form Factors

The electromagnetic nucleon form-factors data are studied with artificial feed forward neural networks. As a result the unbiased model-independent form-factor parametrizations are evaluated together with uncertainties. The Bayesian approach for the neural networks is adapted for chi2 error-like function and applied to the data analysis. The sequence of the feed forward neural networks with one hidden layer of units is considered. The given neural network represents a particular form-factor parametrization. The so-called evidence (the measure of how much the data favor given statistical model) is computed with the Bayesian framework and it is used to determine the best form factor parametrization.

hep-ph↗

Quark-hadron duality in lepton scattering off nucleons

Quark-hadron (QH) duality in lepton scattering off nucleons is studied with the resonance quark model. It is shown that in the case of neutrino scattering off an isoscalar target the duality is simultaneously observed for charged and neutral currents $xF_1^{νN}$, $F_2^{νN}$, and $xF_3^{νN}$ weak structure functions. We demonstrate that the QH duality can be useful property for modeling structure functions in the so-called resonance region. As an example it is shown that combining relativistic quark model predictions with duality arguments allows a construction of the inclusive resonance $F_2^{ep}$ structure function.

hep-ph↗