FLOWER: soFtware for LOW-Energy Reconstruction

An energy reconstruction script for low-energy events in Hyper-Kamiokande.

FLOWER requires a trigger with a reconstructed event vertex from an external tool, such as (hk-)BONSAI. It then iterates over detected hits in a short time window and applies corrections for detector effects to estimate the total number of Cherenkov photons emitted by the particle. Finally, it matches this number to a reconstructed particle energy based on MC simulations. A detailed description of this method (which is based on the one used in Super-Kamiokande) and the individual corrections can be found in chapter 3.4.3 of Jost Migenda’s PhD thesis.

Compiling WCSimFlower

Make sure the following are sourced

• WCSim ($WCSIM_BUILD_DIR set) Note that the WCSim dependence of the WCSimFlower class is confined to geometry information.

Then

export FLOWERDIR=/path/to/FLOWER
make

Running the FLOWER/BONSAI script bundled here

Make sure the following software is setup correctly

• WCSim ($WCSIM_BUILD_DIR set)
• BONSAI ($BONSAIDIR set)
• FLOWER ($FLOWERDIR set)

Then

export PATH=$FLOWERDIR/rootflower:$PATH
export FLOWERDATADIR=/path/to/writable/directory/ #e.g. $FLOWERDIR/data/
rootflower -b -q flower_with_bonsai.C+'("/path/to/wcsim/file.root",1,"SuperK")'

Note that $FLOWERDATADIR is used to store information that takes a while to calculate, and that only needs to be done once per geometry (e.g. the nearest neighbours of each PMT). If $FLOWERDATADIR is not set, or set to a directory that doesn't exist, $FLOWERDIR/data/ will be used instead

Running in other code

• Construct a class member, giving it a detectorname (it sets default values and determines the exact energy correction factors) and detector geometry

WCSimFlower(const char * detectorname, WCSimRootGeom * geom, int verbose);

• Override default values of parameters with these methods

void SetDarkRate(double darkrate);
void SetNPMTs   (int npmts);
void SetNWorkingPMTs(int nworkingpmts);
void SetNeighbourDistance(double neighbourdistance);
void SetShortDuration(double shortduration);
void SetLongDuration(double longduration);
void SetTopBottomDistance(double hi, double lo);

• Every event/trigger, send it a list of hit times, hit tube IDs, and reconstructed vertex position (x,y,z)

double GetEnergy(std::vector<float> times, std::vector<int> tubeIds, float * vertex);