DiJet Kinematic Studies

This purpose of this study is to explore different ways of treating neutral only dijet data. Learning how to handle neutral data will be important for analyzing data from the trigger data block where no tracking information is available as well as for extending a dijet analysis to high (>1.3) pseudorapidity where tracking from the TPC dies out. The main issue that needs to be explored is how well one can reconstruct the jet pT using only energy deposited in the calorimeters. The leading order expressions for the partonic momentum fractions depend on the pseudorapidity of the two jets, the beam energy and the transvers momentum of the jets, so finding an accurate way of getting pT is essential. This is a rough analysis designed to give an idea of what may be feasible and what may not and so is missing many factors which would go into a full investigation. One would need to do a more rigourous version of this investigation using the full STAR simulation environment for any true dijet analysis.

This study has been carried out using the C++ version of pythia (8.1). I have used the simple jet finder included to carry out the jet studies. I have also created a modified version of the jet finder that only includes final state gamma particles in the jet to simulate the neutral data.

Simulations:

As mentioned above, finding an accurate substitute for pT is essential for doing a neutral dijet study so I have explored four different substitutes: Sqrt[ET(Jet 1) x ET(Jet 2)], (1/2)x[ET(Jet 1) + ET(Jet 2)], Max[ET(Jet 1), ET(Jet 2)], and Min[ET(Jet 1), ET(Jet 2)]. So far I have made 4 sets of simulations, each with different threshold conditions. All sets contain a minimum pT cut. When graphing quantities such as partonic momentum fraction, I require that the highest jet ET be greater than the minimum pT needed to ensure that one of the partons had a momentum fraction greater than 0.2.  Set 0 contains no thresholds beyond the settings of the jet finder, set 1 requires the geometric mean of the two jet ETs be greater than 6GeV, set 2 requires ET(Jet 1) > 8GeV and ET(Jet 2) > 6GeV, and set 3 requires [ET(Jet 1) - ET(Jet 2)] > 2GeV.

Each set is divided into 2 pdfs, one for the full jet finder and one for the neutral jet finder.

Set 0:

• Full Jet plots are here
• Neutral Jet plots are here

Set 1:

• Full Jet plots are here
• Neutral Jet plots are here

Set 2:

• Full Jet plots are here
• Neutral Jet plots are here

Set 3:

• Full Jet plots are here
• Neutral Jet plots are here