Applying dR cut

[ico1036]

Hi all,

I try to do following selection using Coffea.

Photon = [ [ pho1 ], [ pho2, pho3 ], [ ] ]
Electron = [ [ e1, e2 ], [ e3, e4 ] , [e5] ]
Select photons with dR (photon, all Electron in the event) > 0.5

I try following method.

pho_ele_pair` = `ak.argcartesian([Photon,Electron])

[ (0, 0), (0, 1) ] , [ (1,2 ) (1,3), (2,1), (2,3) ], [ ] ]

pho,ele = ak.unzip(pho_ele_pair)

pho > [ [0,0], [1,1,2,2], [ ] ]
ele > [ [0,1], [2,3,2,3], [ ] ]

pho.delta_r(ele) > 0.5

[ [T ,F], [T,T,T,F], [ ] ]

The result should be

pho_sel_mask = [ [F], [T, F] , [ ] ]

but I can't find solution.
is there any clever method?
Thank you in advance.

[nsmith-]

The missing ingredient is the nested option to ak.cartesian, e.g.

pair = ak.cartesian({"pho": events.Photon, "ele": events.Electron}, nested=True)
pho_sel_mask = ak.all(pair.pho.delta_r(pair.ele) > 0.5, axis=-1)

Since this is such a common operation, NanoEvents has a shortcut method metric_table, which could be used as:

pho_sel_mask = ak.all(events.Photon.metric_table(events.Electron) > 0.5, axis=-1)

(the default metric is delta_r)

[ico1036]

Thank you very much!