Hi Rooters, I guess this could be an intresting issue for public discussion: Yves Schutz writes: > > Does a class "Lorentz vector" also exist ? > >To the moment ROOT doesn't include classes for physics-oriented >(2D-, 3D- and Lorentz) vectors. I'd consider it as an important piece >which is still missing. One could think about several possibilities of >how to fill this "hole": >- recently Stefan Kluth reported on his success in generating rootcint >dictionaries for CLHEP classes. (Great job, Stefan!) >In principle, one could take CLHEP classes as a starting point. The major >problem with CLHEP as I see it is that currently it doesn't seem to be >supported. Hm, that not quite true, CLHEP is a component of Geant4 and it is also used by BaBar. It is supported by a member of the Geant4 team who is also a member of the BaBar collaboration. >Moreover, physics vectors seem to be the least developed part of CLHEP, >the classes are missing quite a few very useful methods and it is not For BaBar applications it seems to be reasonably complete. I suspect that for proton collider physics a few things are missing? >clear what to do if we need these methods to be added: >- to ask somebody (whom?) to add missing methods (like pseudorapidity of >a 3-vector or delta(phi) between 2 2(3)-vectors) to CLHEP? >- to branch ROOT flavor of CLHEP ? >And definitely one'd like physics vectors to "know" about ROOT's TMatrix >class, whereas CLHEP vectors do not deal with ROOT TMatrices. So it seems >that even if we start from CLHEP, ROOT "flavor" of CLHEP will immediately >evolve into an independent package and it is necessary to understand all >the consequences of this step. Effectively, CLHEP-root is already separate from the original CLHEP, because I dropped some less than useful classes, reorganised the directory structure and added some extra pieces, like a root-streamable version of HepAList<T>. Also, for some reason I started of a somewhat older version of CLHEP which is already one or two steps behind BaBars version CLHEP. >Anyway, as we already have a community of people actively using ROOT, I >believe that >a) it is clear that we need physics vectors classes to be added to ROOT >and Yes I agree >b) that it makes a lot of sense to discuss what exactly we want from >these >classes before going into implementation - here we facing a situation >where >it is more difficult to decide on what is the right thing to do than to >implement it. Hm yes, and not yes. Implementing a general purpose physics vectors package with transformations etc. useful in e+e- and hadron physics (and whatever else physics) is not an easy task. Personally, I am quite glad that the theorists who implemented the 3- and Lorentzvectors in CLHEP did already do most of that thinking for us. I think we should try to make all serious candidate packages available to root, probably as root-linkable shared libs, so that users can try them out. cheers, Stefan ---Stefan Kluth---------------Lynen Fellow----------------|\--|\------- - LBNL, MS 50A 2160 - phone: +1 510 495 2376 - |/ |/ - - 1 Cyclotron Rd. - fax: +1 510 495 2957 - |\/\|\/\|' - ---Berkeley, CA94720, USA-----e-mail: SKluth@lbl.gov------|/\/|/\/|----
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