Introduction

The efficiency to find a hit in an active detector volume can be described using the following components:

P_measured = (P_instrumental + P_background) * P_corr * P_tracking

where

P_instrumental (aka P_detector) is the probability for the detector active media to produce a signal that can be recorded (Includes efficiency of hardware and/or low level thresholds, pedestals, etc)
P_background is the probability to have a hit within the window that is not produced by the considered track (for example detector noise, other tracks, etc)
P_corr include cluster/hit reconstruction efficiency, uncorrected unknown distortions, inefficiency of known corrected distortions
P_tracking is the pure tracking efficiency, i.e. the probability to assign a hit to the track by the tracking algo. Includes algo specific requirements such as number of time hits can be used/reused, hit acceptance/rejection cuts (chi^2), etc.

How to use

To build the library and the executable follow the installation instructions in the project's ../README.md "README.md". Once the StiHify library is built it can be loaded and the StiHifyTreeMaker can be added to the reconstruction chain by using the StiHifyTreeMaker option as:

root4star -b -q -l 'bfc.C(<first_event>, <last_event>, "<your_bfc_options> StiHifyTreeMaker", "<input_file>")'

In order to disable a sensitive Sti volume (with hits) one can provide a file called deactivate_sti_detectors.txt with a list of regex patterns matching the name of the volume to skip in tracking. Providing this file is optional but required if one would like to estimate the true single hit efficiency of a detector.

By default, all tracks and track nodes will be saved in the output tree. This is an unlikely desirable feature as it can lead to a very large output tree. To limit the number of saved track and track nodes one can provide another text file called save_sti_detectors.txt containing regex patterns matching the name of the Sti volumes crossed by tracks. In the simplest case both the deactivate_sti_detectors.txt and save_sti_detectors.txt files can contain the same set of regex patterns.

Once the tree is produced one can run the stihify program over it to create a set of histograms with hit efficiencies.

Reconstruction chain examples

Note that in the following example the PXL hits are excluded from tracking by using the NoPxlIToption.

root4star -q -b -l 'bfc.C(1, 100, "P2014a mtd btof pxlHit istHit NoPxlIT BEmcChkStat CorrX OSpaceZ2 OGridLeak3D -hitfilt StiHifyTreeMaker", "st_physics_file.daq")'

The following command is for the pretty much standard reconstruction with all HFT hits used in tracking.

root4star -q -b -l 'bfc.C(1, 100, "P2014a mtd btof pxlHit istHit sstHit BEmcChkStat CorrX OSpaceZ2 OGridLeak3D -hitfilt StiHifyTreeMaker", "st_physics_file.daq")'

Regular expressions matching geometry volumes used at STAR

Beam pipe                   ^.*IDSM_1/PIPI_1/PBES_1$
Field cages                 ^.*TPCE_1/T[IO]FC.*$
PXL all volumes             ^.*IDSM_1/PXMO_.*$
PXL sensitive volumes       ^.*IDSM_1/PXMO_1/PXLA_[\d]+/LADR_\d/PXSI_[\d]+/PLAC_1.*$
PXL ribs                    ^.*IDSM_1/PXMO_1/PXLA_[\d]+/PXRB.*$
                            ^.*IDSM_1/PXMO_1/PXLA_[\d]+/PXLB.*$
IST all volumes             ^.*IDSM_1/IBMO_.*$
IST sensitive volumes       ^.*IDSM_1/IBMO_1/IBAM_[\d]+/IBLM_\d/IBSS_1.*$
SST all volumes             ^.*IDSM_1/SFMO_.*$
SST sensitive volumes       ^.*IDSM_1/SFMO_1/SFLM_[\d]+/SFSW_[\d]+/SFSL_1/SFSD_1.*$