New supernova neutrino spectrum

Gleb SinevLArSoft Coordination Meeting

April 12, 2016

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New SNν energy spectrum

● Original spectrum is not cross-sectionweighted → is not what we expect to see

● New spectrum exposed a bug – fixed

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Input νe spectrum

Livermore model (LArSoft default) GVKM modelcross-section weighted

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Output electron spectrum

Livermore model (LArSoft default) GVKM modelcross-section weighted

All plots in this talk are made for generator-levelMC truth, before detector simulation or LArGeant

This change should greatly increasenumber of observable neutrinos

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Bug in output energy

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Sampling neutrino energy(no interpolation)

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Bug● Problem with the way energy is sampled● Y values normalized to 1 instead of total area● The bug disappears if the total area

is normalized to 1● Doesn't matter if the input TGraph

spectrum does not have gaps (all points are equidistant in energy)

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Sampling neutrino energy now

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Bug is fixed

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Conclusions● New spectrum is already in larsoft_data

(gvkm_nue_spectrum.root)● Would like to change the spectrum

used by default in larsim/EventGenerator/supernova.fcl

● Will merge the bug fix later(I would like to use a ROOT TF1/TH1 method to sample energy – the new spectrum is not affected)

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Backup slides

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Livermore final particle energy spectra

Unfortunately the electron spectrumis quite different from the neutrinospectrum – this will make determination of the initial neutrino energy challenging

All plots in this talk are made for generator-levelMC truth, before detector simulation or LArGeant

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GVKM final particle energy spectra

Input neutrinos are more energetic→ electron energy is much closerto the neutrino energy→ this model doesn't take into account 40Ar excitations above ~7 MeV,so I'm not sure how accurate it isfor higher energy neutrinos All plots in this talk are made for generator-levelMC truth, before detector simulation or LArGeant

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Supernova neutrino generator● A generator written by AJ Roeth

(LBNE-doc-8225-v1)● Calculates νe-40Ar CC cross section

using 21-level model● Produces an electron and several γs

using 73-level model● Simulates νe-40Ar CC interactions in a box

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Simulation model

40Ar 40K

21 levelsto calculate

cross section

νe → e-γ

γ

73 levelsto simulategammas

40K*

Nearest level(not a transition)