# A Using Fastjet in Pythia to plot distribution of particles

1. Feb 28, 2017

### Sandeep Hundal

I am using fastjet in pythia8.I am studying jet formation in pp collisions.I need to plot distribution of transverse momentum of fastest particle in fastest jet formed in 1000 events simulated.But i dont know how to access particle properties after jet formation.Like if I want to know the fastest particle out of the particles which have formed that jet ,I am not able to access it.Can anybdy explain ?
Thanks

2. Mar 1, 2017

### Staff: Mentor

The fastest particle? That is an unusual quantity.

The quickstart has an example how to access the jet constituents.

3. Mar 1, 2017

### ChrisVer

by fastest you mean the one with the highest pt? (would make more sense at least from my experience)

4. Mar 2, 2017

### Sandeep Hundal

yes ,here fastest means with highest pt

5. Mar 2, 2017

### Sandeep Hundal

It worked
Thanks

6. Mar 15, 2017

### Sandeep Hundal

How can we access lowest pt particle(constituent) of sub leading jet ?

7. Mar 15, 2017

Staff Emeritus
Does Section 3.5 of the manual not cover that?

8. Mar 15, 2017

### Staff: Mentor

The functions shown in the quickstart example are sufficient for this as well.

9. Mar 15, 2017

### Sandeep Hundal

yes,It worked now.Actually in some of the events,only less than 2 jets were formed.so It gave an error.Now I have imposed the condition to select only those events that have more than 1 jet.Now the question is -is that possible that in some events no jet formed even after clustering in pythia using fastjet?
Thanks .Your guidance is helping me a lot :)

10. Mar 16, 2017

### Staff: Mentor

It depends on the events simulated, but in general: sure. Not every pp collision produces particles high-energetic enough to be included in jets. Some don't produce particles in the detector at all.

11. Mar 16, 2017

### ChrisVer

Hmmm, I would like to know what you define as a jet? Would a muon give you a jet?
As jets I was imagining objects of grouped clusters (which are grouped cells), that satisfy certain quality criteria (some energy thresholds and so on). Those are formed only for signals recorded in the calorimeter (so objects that are recoed from the calorimeter won't be called jets?).
Then are you refering to the jets that come from the hard scattering process?

12. Mar 22, 2017

### Sandeep Hundal

yes,I am refering to the jets that come from hard scattering processes after fragmentation and hadronization.

13. Mar 22, 2017

### ChrisVer

So ignoring the pileup jets, the process: $qq\to W \to \mu \nu$ wouldn't necessarily give you a "jet" in your event.