Puppi candidates for b tagging of Puppi jets in MiniAOD for Phase 2 #18317
Conversation
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A new Pull Request was created by @ferencek (Dinko Ferencek) for master. It involves the following packages: PhysicsTools/PatAlgos @perrotta, @cmsbuild, @slava77, @monttj, @davidlange6 can you please review it and eventually sign? Thanks. cms-bot commands are listed here #13028 |
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@cmsbuild please test |
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The tests are being triggered in jenkins. |
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Comparison is ready Comparison Summary:
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@ferencek |
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@imarches (in case @ferencek is away) |
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@slava77, there have been some studies going in that direction:
In both cases there are no significant improvements observed and for ak4 jets things are further complicated by the fact that in some cases the performance curves for the two cases (current default and the explicit JTA) cross each other so neither of the two cases is uniformly better or worse. Only in extremely high PU scenarios encountered in Phase II does Puppi start to make a difference. This is probably because it dramatically reduces the number of tracks associated to any given jet significantly reducing the combinatorial background. The bottom line is that there is no strong reason to switch to Puppi candidates as input for b tagging for scenarios other than Phase II. |
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The first link (AK4 study) appears to use Phys14DR-PU20bx25
The second link for AK8 relies on PUSpring16.
Both had essentially a factor of two smaller pileup than the latter
half of 2016 or what's expected in 2017.
Where in PU does the turn-over for phase-2 to be clearly needing PUPPI
happening?
Is it only barely visible at 140 .. what about 70?
On 4/19/17 12:13 PM, Dinko Ferencek wrote:
The bottom line is that there is no strong reason to switch to Puppi
candidates as input for b tagging for scenarios other than Phase II.
I read your observations and conclude differently:
there is no difference in performance and phase-1/0 can use puppi in
btags of puppi jets.
My goal is to minimize unnecessary historical precedents maintained by eras
and keep the reconstruction configuration uniform.
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@slava77, I think more studies are needed before this type of change is possibly introduced for Phase 1. However, I understand you point about uniform configuration. That would definitely make life and code maintenance easier. But I'm also afraid that that is too idealistic to expect and Phase 2 stuff will likely require special treatment for quite some time. It corresponds to dramatically different running conditions and we still have very preliminary detector description in the simulation as well as very preliminary reconstruction so insisting on some changes in Phase 0 and 1 just to be uniform with some preliminary configuration for Phase 2 seems premature to me. |
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It looks like the arguments so far reduce to "we want to be safe by staying with a historical choice for phase-1/0 and haven't had time to check". References provided appear to be rather old and have much smaller PU than late 2016 or 2017 and probably work out differently with the latest PUPPI tunes. I'll sign but will make an issue to be followed up hopefully soon. |
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+1
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This PR switches the input candidate collection used in b tagging from the default Particle-flow candidates (
particleFlow) to Puppi candidates (pupi) for Phase 2. These changes only affect MiniAOD, more specifically ak4 Puppi jets, for the Phase 2 era.This is related to #18260 but does not add new b-tag discriminators since they are now added in #18315