MC GEnerator for Neutrino Interaction Experiments Authors: Costas Andreopoulos, Panos Stamoulis, George Tzanakos Object-Oriented Design Extensive use of Design Patterns & Reusable Software Architectures Extensive use of ROOT & STL Extensive use of XML Network (TCP/IP) Interfaces Modeling of all neutrino interaction processes, calculation of cross sections, form factors, parton densities... Modeling of auxiliary phenomena : 3-D neutrino oscillations, matter effects, muon energy loss mechanisms... GENIE is in prototyping-phase This work was based on Prototype Version 1 Version 2 will be on public domain (distributed under GPL) this summer

3 - flavor oscillations One dominant mass scale approximation Switching matter effects ON/OFF Modeling of Neutrino Oscillations In this framework, the v μ survival probability, for example, is Example: Δm 2 32 =0.004 eV 2 /c 4 θ 23 =45 ο, θ 13 =11.5 ο

Quasi Elastic Scattering : Simple! The neutrino sees a “structureless” target nucleon. Single Pion Production : Complex! Need a dynamical model to describe the bound state of quarks. Deep Inelastic Scattering : Simple again! The neutrino sees the nucleon structure but scatters off a structureless parton. Neutrino Interactions Include: Quasi Elastic Scattering Single Pion Production Deep Inelastic Scattering Leptonic tensor: well known from V-A theory Hadronic tensor?

Neutrino Interactions - Quasi Elastic Scattering We use the parameterization of E.A.Pashos and J.Y.Yu, “Neutrino Interactions in Oscillation Experiments”, hep-ph/ CC QE Form Factors Kinematic Limits

Quasi Elastic Scattering - Predictions & Comparisons with data

Neutrino Interactions - Single Pion Production We use the model of Deiter Rein and Lalit M. Seghal, “Neutrino - Excitation of Baryon Resonances and Single Pion Production”, Ann. Phys, 133, 79 (1981) This model is based on the dynamical model of baryon excitation of R.P. Feynman, M. Kislinger and F. Ravndal, Phys. Rev. D 3, 2706 (1971) Kinematical Limits q 2 : same as in QE (M N  M RES ) W: Helicity components

Single Pion Production Baryonic Resonances Taking into account 16 resonances Single Pion Production is dominated by Δ(1232)P 33 Each resonance is described by a Breit-Wigner distribution with an L-dependent threshold behavior

Single Pion Production Isospin Analysis Cross Sections for different channels are built from cross sections for exciting baryon resonances Using isospin Glebsch-Gordon coefficients Original expressions by Rein- Seghal were modified by assuming non-interference between different resonances

Single Pion Production - Predictions & Comparisons with data

We use the parameterization of E.A.Pashos and J.Y.Yu, “Neutrino Interactions in Oscillation Experiments”, hep-ph/ Neutrino Interactions - Deep Inelastic Scattering Parton Density Functions We use the MRST99 parton density function set MRST99 is described in hep- ph/ (A.D. Martin, R.G. Roberts, W.J. Stirling, R.S. Thorne) The ‘evolution’ stops at Q 2 min =1.25GeV 2. For Q 2 <Q 2 min we consider pdfs to be the same as for Q 2 =Q 2 min

DIS - Predictions & Comparisons with data

All modeled Neutrino Interaction Processes