[Rivet] DISLepton Class fails to find outgoing lepton

[Leif Lönnblad]

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.

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.

However, looking at the old HZtool routines, they always use the 
generator definition. 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.

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.

/Leif


-- 
Leif Lönnblad
Department of Astronomy and Theoretical Physics
Sölvegatan 14A, S-223 62 Lund, Sweden
phone: +46-46 2227780,  fax: +46-46 2229686
e-mail: <Leif.Lonnblad at thep.lu.se>