Access constituents corresponding to pT ordered jets?

[qibin2020]

Dear experts,
I hope to ask how to read the ClusterSequence.constituents() of pT ordered jet?
I found I can use sorted_by_pt() to process the inclusive_jets(), while is there a way to handle the constituents() as well? Thank you!
(I am using the array interface)
Best,
Q.

[rkansal47]

Hi, is your question how to handle sort the constituents of a ClusterSequence by pT?

The ClusterSequence.constituents() should return the particle 4-momenta, similar to this list, but as an awkward array. Unfortunately, I see that you cannot directly use the fastjet.sorted_by_pt() function on this, but you can recreate the output array with the necessary behaviour and then use that function:

import vector
arr = ak.Array(cluster.constituents(), behavior=vector.backends.awkward.behavior, with_name="Momentum4D")
sorted = fastjet.sorted_by_pt(arr)

Let us know if that doesn't answer your question. I will also let others comment if there are easier / more efficient solutions.

[qibin2020]

Hi thank you and basically I am wondering how to sort the constituents according to the jet pT. e.g.
I can use fastjet.sorted_by_pt(inclusive_jets()) to get a list of sorted jet. Then I hope to access the constituents, in the order of this sorted jets.

[lgray]

constituents = ak.Array(cluster.constituents(), behavior=vector.backends.awkward.behavior, with_name="Momentum4D")
pt_idx = ak.argsort(constituents.pt, ascending=False) # highest pT first for each jet
pt_constituents = constituents[pt_idx]

is another solution.

[qibin2020]

Thank you all and yes that answer my question. I realized I can first get the order using argsort() and then sort in any axis. Also the directly sorted_by_pt() is compact and helpful. Thank you for your answers!