[Rivet] pT cut on B hadrons

[Christian Gutschow]

Hi Andy, all,

yes, please!
+1 for being able to use Cuts as an argument to bTags().
That's a much neater way of doing it..

Cheers,
Chris

On 29 July 2015 at 12:54, Andy Buckley <andy.buckley at cern.ch> wrote:

> Hi Kevin,
>
> Thanks for the ping -- this had gone off my radar / I thought I had
> answered. I've copied this to the Rivet developer list, which is a more
> reliable place to ask questions due to more people & more expertise on the
> receiving end.
>
> I'm not quite sure why you are asking: have you noticed a change in
> behaviour without the cut across Rivet versions? In general I think making
> cuts explicit is the right thing to do.
>
> But I guess when you say that you are doing it manually that you really
> mean you are explicitly making a list of "b" particles with some kinematic
> cuts, then deltaR-matching those to the jets? We could/should allow the
> user to specify tag-particle cuts when configuring the FastJets projection,
> but right now you can do something like:
>
> const Jets& myjets = applyProjection<FastJets>(evt, "Jets").jets();
> foreach (const Jet& j, jets) {
>     foreach (const Particle& t, j.bTags()) {
>         if (t.pT() > 5*GeV) // accept this jet
>     }
> }
>
> We can make this nicer to use, e.g. I imagine something like this would be
> helpful:
>
> foreach (const Jet& j, jets) {
>     if (j.bTags(Cuts::pT > 5*GeV).size() > 0) // accept this jet
> }
>
> What do you think? It's an easy feature to add.
>
> Andy
>
>
> On 29/07/15 02:20, Kevin Finelli wrote:
>
>> Hi Andy,
>>
>> Just pinging again to see if you have had the chance to read this.
>>
>> Thanks,
>> Kevin
>>
>> On Fri, Jul 24, 2015 at 5:06 PM, Alexander Grohsjean
>> <Alexander.Grohsjean at desy.de <mailto:Alexander.Grohsjean at desy.de>> wrote:
>>
>>     Hi Andy,
>>
>>     maybe to clarify. In the original code I provided, there was a cut
>>     of 5 GeV.
>>     When testing my implementation against the Rivet one using 50 k
>> events,
>>     as Kevin wrote, we got exactly the same yoda files out.
>>     That's why it is not clear if this cut was dropped between versions
>>     or if the 50k was not enough statistics to see any difference.
>>
>>     Cheers, Alexander.
>>
>>
>>
>>
>>     Am 24.07.2015 um 04:31 schrieb Kevin Finelli:
>>
>>         Hi Andy,
>>
>>         We were hoping you could clarify the situation with pT cuts on B
>>         hadrons used in truth jet b-tagging within Rivet.  In my own
>>         tests, using 2.2, I have been "manually" applying the standard 5
>>         GeV pT requirement on B hadrons needed for a jet to be
>>         considered b-tagged.  This is now in the 7 TeV pseudotop
>>         analysis (ATLAS_2015_I1345452), Chris G. submitted a patch about
>>         a week ago.
>>
>>         Looking back, I noticed the tt+jets analysis
>>         (ATLAS_2014_I1304688) doesn't make this cut explicitly.
>>         Alexander mentioned that this cut was not needed when the
>>         analysis was tested, as two implementations of the ghost
>>         association gave identical results in 50k events.
>>
>>         Is it possible there was a cut in FastJets that changed in Rivet
>>         2.2?  In any case it seems that we might want to go back now and
>>         make this cut explicit in the tt+jets routine.
>>
>>         Regards,
>>         Kevin
>>
>>
>>
>>
>
> --
> Dr Andy Buckley, Lecturer / Royal Society University Research Fellow
> Particle Physics Expt Group, University of Glasgow
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