Pythia Jets in the Forward Region Part 2 

 

 

After last week's confusion regarding the very low particle multiplicities of the Pythia "jets" in the forward region, I did a bit more study and found out the follwoing.

1. The multiplicity of a "jet" depends primarily on the pT of the jet, and the z of the leading particle. It seems to have almost no dependence on the total energy of the jet, which is (I think) expected in a string fragmentation model. 

2. Therefore, most of the oddities observed last week can be blamed on the pT being too low in the forward region. 

3. I have not been able to check this against the data yet. 

 

For all following plots, Pythia 6.4 + tuneA + <kT>=0.5GeV were used. The jet cone radius is 0.7 in eta-phi for all. 

 

Fig. 1. Pseudorapidity dependence of the track multiplicity.

 

 Fig. 2. Track multiplicity vs. Jet pT for 4 pseudo-rapidity regions, for z<0.7. 

 

 

Fig. 3. Overlaying the profile plots above, where BLACK:0~1, RED:1~2, GREEN: 2~3, and BLUE:3~4 in eta. (Again, for z<0.7)

 

 

Fig. 4. Track multiplicity vs Jet energy in 5 pT bins. BLACK: pT=0~1GeV, RED: pT=1~2GeV, GREEN: pT=2~3GeV, BLUE: pT=3~4GeV, MAGENTA: pT=4~5GeV 

 

 

 

Fig. 5. Track multiplicity vs. fragmentation fraction in 10 pT bins. As above, the interval is 1GeV in pT, except in this case the final bin is for pT=9~10GeV.  

 

 

Fig. 6. Jet energy and parton energy matching vs. Jet pT in 4 eta regions.

 

Fig. 7. Overlaying the above profile plots.