Update on neutrino simulation with GENIE Carla Distefano

GENIE based neutrino generation code Main code: gSeaNuEvGen Libraries: GSeaAtmoFluxflux driver: generation of neutrinos GSeaRealAtmoFluxflux driver: definition of the physical flux GSeaGeometrygeometry driver: building of the interaction volume EvtWrite class: writing of the evt output file (same tags in GenHen) New organization of the code:

The main code: gSeaNuEvGen gSeaNuEvGen Generation of electron and muon flavours Generation of neutrinos and anti-neutrinos at the same time (e.g. ν μ + anti-ν μ ) Simulation of CC, NC but also CC+NC For muons: propagation still done with Music but now the code is linked with PropMusic Spectrum binned in equal divisions in Log10(E ν ): - Probabilities are scaled-up at each bin (P scale ) -> higher stat. at low energy - For muons: scaled volumes and number of events (GenHen approach) Same output of GenHen (class EvtWrite linked to Antares io library)

Geometry Driver: GSeaGeometry A new geometry driver to build the neutrino interaction volume (just a function in the first code version) The class: Reads the.det geometry file and defines the detector CAN. Loads the muon maximum ranges from an input file. They will be used to build the muon neutrino interaction volume. Define the interaction media: Seawater (Density= 1,050 kg/m 3 ): Rock (Density= 2,650 kg/m 3 ): Silicon dioxide: SiO 2

Geometry Driver: GSeaGeometry Builds the interaction volume using the TGeoManager ROOT class: Calculates the R T and R L radii defining the neutrino generation surface (see next slides) Interaction Volume for muon neutrinos: R=R can +R maxSW Seawater H=min(H can +R maxSW, Depth) Rock H=R maxR E max =450 GeV The interaction volume is built for each energy bin. Interaction Volume for electron neutrinos: Seawater The geometrical volume coincides with the detector CAN The interaction volume is the same for each energy bin.

Flux Drivers: GSeaAtmoFlux and GSeaRealAtmoFlux The flux driver generates the flux of incident neutrinos GSeaAtmoFlux based on the standard atmospheric neutrino flux driver GAtmoFlux, but: Weighted simulation with spectral index set by user (also α=1) Possibility to set the neutrino angular range Computation of the generation weight Physical flux evaluated by interpolation (already introduced in present simulations) Rejection of neutrinos not passing within fGCut m of the CAN for ANTARES can fGCut=533 m (in GenHen GCUT=500 m set by the user in the input card).

Flux Drivers: GSeaAtmoFlux and GSeaRealAtmoFlux For each generated direction (θ,φ), the flux generation surface is a circular area, with radius R T, which is tangent to a sphere of radius R L centred at the coordinate system origin R T and R L are computed by GSeaGeometry as R T = 2R. sinΘ (with tanΘ =H/2R);R L = D where H, R and D are respectively the height, radius and diagonal of the interaction volume R T and R L are set at each energy bin interaction volume Event weight computation Generation weight: Including P earth in progress (Column Depth computation done) Physical flux: Bartol or Fluka fluxes defined using the GSeaReaAltmoFlux driver (where other fluxes could be easily implemented) GAtmoFlux

Generation of muon (anti-)neutrinos Energy range: GeV (α=-1.4) Up-going events, flat in solid angle Neutrinos and anti-neutrinos Flux driver: GSeaAtmoFlux + GSeaRealAtmoFlux Bin Generation Volume detector CAN+R μ,max Medium: seawater+rock Geometry driver: GSeaGeometry in 1yr: GenHen= Genie= GenHen/Genie=1.15 Bartol flux: ν μ + anti-ν μ 1yr The code takes a time a factor 10 larger than GenHen (due to the full simulation); The difference will increase at high energy; We’ll consider the possibility to implement a fast simulation mode (GenHen approach).

Generation of muon (anti-)neutrinos

Generation of electron (anti-)neutrinos CC int. Ntot: generated neutrinos Nbin: interacting neutrinos Ntot Running time (Ntot=10 6 ): 453 s102 s Interacting neutrinos (evt in the output): but GENHEN time at these energies is a factor 40 shorter comparison of results still in progress…. Energy range: GeV (α=-1.4) Up-going events, flat in solid angle Neutrinos and anti-neutrinos Flux driver: GSeaAtmoFlux Generation Volume (detector CAN) Can: Medium: seawater Geometry driver: GSeaGeometry in both cases, the processing time per event is 0.05 s

Generation of electron (anti-)neutrinos E v >100 GeV in 1yr: GenHen= Genie= GenHen/Genie=1.26 Physical flux: Bartol (using GSeaRealAtmoFlux) CC Interaction type: CC