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.Comment: minute text changes, one ref. added, version as published in Phys. Re

Neutrino-nucleus interactions

Interactions of neutrinos with nuclei in the energy ranges relevant for the MiniBooNE, T2K, NO$\nu$A, MINER$\nu$A and MINOS experiments are discussed. It is stressed that any theoretical treatment must involve all the relevant reaction mechanisms: quasielastic scattering, pion production and DIS. In addition, also many-body interactions play a role. In this talk we show how a misidentification of the reaction mechanism can affect the energy reconstruction. We also discuss how the newly measured pion production cross sections, as reported recently by the MiniBooNE collaboration, can be related to the old cross sections obtained on elementary targets. The MiniBooNE data seem to be compatible only with the old BNL data. Even then crucial features of the nucleon-pion-Delta interaction are missing in the experimental pion kinetic energy spectra. We also discuss the meson production processes at the higher energies of the NO$\nu$A, MINER$\nu$A and MINOS experiments. Here final state interactions make it impossible to gain knowledge about the elementary reaction amplitudes. Finally, we briefly explore the problems due to inaccuracies in the energy reconstruction that LBL experiments face in their extraction of oscillation parameters.Comment: Invited plenary Talk at NUFACT 2012. International Workshop on Neutrino Factories, Super Beams and Beta Beams, July 23-28, 2012. Williamsburg, VA U

Invariant dynamics of scalar perturbations of inflanton and gravitational fields

A gauge-independent, invariant theory of linear scalar perturbations of inflation and gravitational fields has been created. This invariant theory allows one to compare gauges used in the work of other researchers and to find the unambiguous criteria to separate the physical and coordinate effects. It is shown, in particular, that the so-called longitudial gauge, commonly used when considering inflation instability, leads to a fundamental overestimation of the effect because of non-physical perturbations of the proper time in the frame of reference specified by this gauge. Back reaction theories employing this sort of gauge [1] also involve coordinate effects. The invariant theory created here shows that the classical Lifshitz (1946) [2] gauge does not lead to non-physical perturbations of the proper time and can be used to analyze the inflation regime and the back reaction of perturbations on this regime properly. The first theory of back reaction on background of all types of perturbations (scalar, vector and tensor) based on this gauge was published in 1975 [3] and has been applied recently to the inflation [4]. The investigation of long-length perturbations, which characterize the stability of the inflationary process, and quantum fluctuations, which form the Harrison-Zel'dovich spectrum at the end of inflation, is performed in the invariant form. The invariant theory proposed allows one to examine the effect of quantum fluctuations on the inflationary stage when the periodic regime changes to an aperiodic one. That only the invariant theory must be used to analyze space experiments is one of the conclusions of the present work.Comment: poster at Symposium "The Dark Universe: Matter, Energy, and Gravity" 2 - 5 April 2001, Space Telescope Science Institute, Baltimore, Maryland 2121

Energy reconstruction in quasielastic scattering in the MiniBooNE and T2K experiments

Neutrino oscillation probabilities, which are being measured in long-baseline experiments, depend on neutrino energy. The energy in a neutrino beam, however, is broadly smeared so that the neutrino energy in a particular event is not directly known, but must be reconstructed from final state properties. In this paper we investigate the contributions from different reaction mechanisms on the energy-reconstruction method widely used in long-baseline neutrino experiments. Difference between the true-QE and QE-like cross sections in MiniBooNE experiment is investigated in details. It is shown, that fake QE-like events lead to significant distortions in neutrino energy reconstruction. Flux-folded and unfolded cross sections for QE-like scattering are calculated as functions of both true and reconstructed energies. Flux-folded momentum transfer distributions are calculated as functions of both true and reconstructed momentum transfer. Distributions versus reconstructed values are compared with the experimental data. Also presented are the conditional probability densities of finding a true energy for a given reconstructed energy. It is shown, how the energy reconstruction procedure influences the measurement of oscillation parameters in T2K experiment. For the reconstruction procedure based on quasielastic (QE) kinematics, all other reaction channels beside true-QE scattering show a shift of the reconstructed energy towards lower values as compared to the true energy. On average in the MiniBooNE and T2K experiments the shift is 100 - 200 MeV and depends on energy. The oscillation signals are similarly affected. These uncertainties may limit the extraction of a CP violating phase from an oscillation result.Comment: 15 pages, 15 figures; v2: misprint corrections, minor text correction

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.Comment: 24 pages, 13 figures; v3: published erratum merged into text around eqs. (15) - (17). Results not affecte

Reaction Mechanisms at MINERν\nuA

The MINER$\nu$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$\nu$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$\nu$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.Comment: Discussion of results on QE enhanced. Added data in Fig. 5. Version close to one being published in Phys. Rev.

Neutrino nucleus reactions within the GiBUU model

The GiBUU model, which implements all reaction channels relevant at medium neutrino energy, is used to investigate the neutrino and antineutrino scattering on iron. Results for integrated cross sections are compared with NOMAD and MINOS data. It is shown, that final state interaction can noticeably change the spectra of the outgoing hadrons. Predictions for the Miner$\nu$a experiment are made for pion spectra, averaged over NuMI neutrino and antineutrino fluxes.Comment: Contribution to NUFACT 11, XIIIth International Workshop on Neutrino Factories, Super beams and Beta beams, 1-6 August 2011, CERN and University of Genev

The Selforganization of Vacuum, Phase Transitions and the Cosmological Constant

The problem of the physical nature and the cosmological genesis of Lambda-term is discussed. This problem can't be solved in terms of the current quantum field theory which operates with Higgs and non-perturbative vacuum condensates and takes into account the changes of these condensates during relativistic phase transitions. The problem can't be completely solved also in terms of the conventional global quantum theory: Wheeler-DeWitt quantum geometrodynamics does not describe the evolution of the Universe in time (RPT in particular). We have investigated this problem in the context of energies density of different vacuum subsystems characteristic scales of which pervaid all energetic scale of the Universe. At first the phemenological solution of Lambda-term problem and then the hypothesis about the possible structure of a new global quantum theory are proposed. The main feature of this theory is the inreversible evolution of geometry and vacuum condensates in time in the regime of their selforganization. The transformation of the cosmological constant in dynamical variable is inevitably.Comment: LaTex 2.09, 10 page

Total gamma-N cross section in the energy range sqrt(s)=40-250 GeV

The results of measurements of gamma-N total cross section, obtained by the method of photoproduction processes registration at the Baksan Underground Scintillation Telescope, are presented. These data at energies sqrt(s)=40-130 GeV confirm the effect of more rapid photon-hadron cross-section rise as compared to the hadron-hadron ones. It is shown, the increasing of the additive quark number in the products of photon hadronization can be one of the causes responsible for this effect. On the basis of the analysis of experimental data on both gamma-N and gamma-gamma total cross sections, the status of direct and indirect cross-section measurements is discussed

The New Scenario of the Initial Evolution of the Universe

We propose that the Universe created from "nothing" with relatively small particles number and quickly relaxed to quasiequilibrium state at the Planck parameters. The classic cosmological solution for this Universe with Lambda-term has two branches divided by the gap. The quantum process of tunneling between the cosmological solution branches and kinetic of the second order relativistic phase transition in supersymmetric SU(5) model on the GUT scale are investigated by numerical methods. Einstein equations was solved together with the equations of relaxation kinetics. Other quantum geometrodynamics process (the bounce from singularity) and the Wheeler- De Witt equation are investigated also. For the formation of observable particles number the model of the slowly swelling Universe in the result of the multiple reproduction of cosmological cycles is arised naturally.Comment: 11 pages (RevTex), 5 PostScript figures. Submitted to Physical Review Letter