StGammaJetAnalysisInPP

This repository compiles the major pieces of code from the STAR $p+p$ $\gamma$+jet analysis. Each module is detailed below, where the order of the list corresponds to the overall flow of the analysis.

1. Third Maker: This reads in STAR $p+p$ data in the form of MuDSTs, and constructs compact ROOT trees (referred to internally as FemtoDSTs) containing $p+p$ collisions tagged by potential energetic $\pi^{0}$ or direct photon based on the algorithm developed by Ahmed Hamed and Saskia Mioduszewski. This algorithm was adapted to save output in the FemtoDST format by Nihar Sahoo.
2. Data Jet Maker: This reads in the output of the Third Maker, reconstructs jets from TPC tracks, and saves them to a compact ROOT tree.
3. Data QA Maker: This also reads in the output of the Third Maker, reconstructs jets from TPC tracks, and produces several QA plots of event-, trigger-, track-, and jet-level quantities.
4. MuDst Matcher: This reads in MuDSTs from the Run9 dijet embedding sample, matches them to the corresponding PYTHIA-6 event record, and saves the reconstructed events in FemtoDSTs and the simulated events in small trees.
5. Embed Jet Maker: These three modules read in the output of the MuDST Matcher and reconstructs jets from various stages of the embedding sample.
   • StGeantJetTreeMaker: This reconstructs jets from simulated charged particles from the StMcEvent collection stored in FemtoDSTs. Ultimately, this was not used for any physics results.
   • StMcJetTreeMaker: This reconstructs jets from simulated charged particles from the McArray branch of the MuDSTs stored in a compact tree.
   • StMuDstJetTreeMaker: This reconstructs jets from the reconstructed events of the Run9 embedding sample stored in FemtoDSTs.
   • StTrackEfficiencyCalculator: This reads in the same events as the StMuDstJetTreeMaker and calculates the tracking efficiency and resolution.
6. Pythia Generator: This generates $\pi^{0}$- or $\gamma$-triggered PYTHIA-8 events and saves them in FemtoDSTs.
7. Pythia Jet Maker: This reads in the generated PYTHIA-8 events and reconstructs jets from charged particles. Also used to apply the calculated tracking efficiency and resolution of StTrackEfficiencyCalculator to the PYTHIA-8 events. Due to historical reasons, the output jet tree is erroneously referred to as a FemtoDST in the code.
8. Jet Matcher: This reads in the output of StMcJetTreeMaker and StMuDstJetTreeMaker and matches each simulated jet to a reconstructed jet to produce a response matrix and jet-matching efficiency. Also matches the particle- and detector-level output of the Pythia Jet Maker to produce a response matrix and jet-matching efficiency.
9. Jet Folder: This unfolds the measured data (the output of the Data Jet Maker) using the response matrices and jet-matching efficiencies from the Jet Matcher. This module was also used to carry out the closure test of the analysis.
10. Systematic Uncertainty Calculator: This takes the output of the Jet Folder and calculates a systematic uncertainty to be applied to the unfolded data.
11. Particle Gun: This module uses starsim to simulate single $\pi^{0}$ and $\gamma$, pass them through a GEANT-3 simulation of STAR, and reconstruct the output using the Third Maker.
12. Trigger Energy Scale Calculator: This takes the output of the Particle Gun and matches the reconstructed $\pi^{0}$ and $\gamma$ to their simulated counterparts, providing a measure of the energy scale and resolution of our measured triggers.
13. Trigger Weight Calculator: This takes the output of the Trigger Energy Scale Calculator and computes a set of weights which emulate the effect of the trigger energy scale/resolution to be applied to the simulated jet spectra compared against the unfolded data.
14. STAR Pythia Jet Maker: This reconstructs jets from charged particles in $\pi^{0}$- and $\gamma$-triggered events simulated by PYTHIA-6 tuned to STAR data. The output of this module was compared against the unfolded data.

The various Jet Maker modules make use of the FastJet library developed by Matteo Cacciari, Gavin Salam, and Gregory Soyez; the Jet Folder modules make use of the RooUnfold library developed by Tim Adye; the Pythia modules make use of the PYTHIA event generator; and all modules make use of the ROOT framework. Naturally, several modules require the use of STAR core software.