[Rivet] DISLepton Class fails to find outgoing lepton

[Andrii Verbytskyi]

Dear Marian,

thanks a lot for participating in this discussion!
As I've said the solution for you could strongly depend on what you want
to do, but in case you have some questions you can contact me in any
time.


Best regards,
Andrii

On Fri, 2017-11-17 at 12:47 +0000, Marian Heil wrote:
> Dear Andrii,
> 
> First of all I really appreciate all effort you put into my report, and 
> I hoped that I expressed it before, but if not: I am sorry, because I 
> definitely do! I never even thought I would get so many productive 
> responses.
> Especially offering me help via Skype was really nice. I only rejected 
> it to not waste you time on my specific problem, while I already got an 
> solution that works for me.
> Some of this may come from me not realizing how deep the problem of a 
> general definition of DIS lepton is. I always only thought about my case 
> with one electron, where finding the "right" electron is trivial ;-). As 
> I said, I am not an expert in DIS and do not know the reasoning for the 
> current definition.
> Again thanks for investing you time in this, the discussion was 
> definitive interesting for me to follow.




> Cheers,
> Marian
> 
> 
> On 17/11/17 10:44, Andrii Verbytskyi wrote:
> > Dear Leif,
> >
> > On Fri, 2017-11-17 at 11:10 +0100, Leif Lönnblad wrote:
> >> On 2017-11-16 12:26, David Grellscheid wrote:
> >>> please accept my apologies on behalf of the Rivet authors for this
> >>> email. This is not an appropriate response to your question
> >> I certainly agree with this! The tone in that letter was completely out
> >> of line.
> > It is sad you think so. I've offered help to Marion to solve the problem
> > but it was *explicitly* rejected. It does not look productive to me to
> > invest my time in collaboration in this case. I will get more work and
> > nobody will even say thanks.
> >
> >
> >
> >> On 2017-11-16 16:23, Andy Buckley wrote:
> >>> My reading of the Rivet 2.5.3 code (copied below) is that it selects
> >>> the highest-|pz| final-state lepton. Looking back through my emails I
> >>> see that Andrii's concern about a final-state definition was actually
> >>> about using highest-pT, i.e. not the same thing. DIS experts, is
> >>> max-|pz| a reasonable heuristic?
> >> Reading old H1 papers it seems their definition of the DIS kinematics is
> >> based on their BEMC detector, which covers polar angles between 151 and
> >> 177 degrees (wrt. the proton direction), and the scattered electron is
> >> taken "as the most energetic BEMC cluster" with energy larger than 14
> >> GeV. A rather simple experimental definition.
> > That is measurement technique and works well for low Q2. Not the case
> > for high Q2 or charged current. Or even simpler  -- what about
> > central/back region?
> >
> >
> >> However, looking at the old HZtool routines, they always use the
> >> generator definition.
> > Exactly. And data was unfolded to it.
> >
> >>   It's not clear to me if they generally correct for
> >> this in any way. I saw one statement where they have studied QED
> >> corrections and get effects of order 5% which they then include in the
> >> systematic uncertainties, but do not correct for.
> > QED corrections is completely other thing. These are not included in
> > Rivet anyway. This means generators should be used w/o FSR.
> >
> >> My guess is that any reasonable definition would do, and that the
> >> original maximum-pz was reasonable, as is the generator definition. I
> >> would, of course, prefer the the experimental definition, but it should
> >> be easy to see what the differences are.
> > "Experimental definition" was quite complicated, i.e. in ZEUS it
> > involved probabilities derived with neural network, isolation of
> > electron, tracking and calorimeter information.
> >
> >
> > Also, the whole discussion is going in circles (already 5 or more
> > years). It is up to developers to decide and understand what they want,
> > not up to me.
> >
> >
> > Best regards,
> > Andrii
> >
> >> /Leif
> >>
> >>
> >
>