Dear friends,
Maybe we are talking different things, but what you
describe I understand as the dotproduct of a 3-vector D
with the 3-vector part of a 4-vector.
So, one takes actually the dotproduct op two 3-vectors, not
of 4-vectors. Let me state it otherwise : try to define the
cross product of two 4-vectors (or a 3-vector with a 4-vector).
I would say, the cross product is only defined in 3-D space, so
one could only take the crossproduct of a 3-vector with the 3-vector
part of a 4-vector.
Cheers,
Nick.
Victor Perevoztchikov wrote:
>
> "M. Sievers" wrote:
> >
> > On Wed, 3 Nov 1999, Nick van Eijndhoven wrote:
> >
> > > Hi Victor,
> > > Maybe I am missing a point here, but the dotproduct you mention
> > > below has to my opinion no physical meaning and as such I would
> > > say should not be supported or at least the user should receive a
> > > warning message that he/she is doing nonsense.
> > > However, as I said I may be missing a point here and then I am
> > > saying nonsense.
> >
> > I'd say a dot product with a three-Vector makes sense much in the same way
> > as an angle to a three-vector does! You could make a four-vector for
> > example by taking tracking information for the momentum and calorimeter
> > information for the energy (should be possible...). And you should still
> > be able to compare it to other tracks!
> >
> > Bye,
> > Mike
> Completely agree. A simple example. You have some direction (3 vector D)
> and momentum of a track 4 vector P. Scalar production of them provide you
> cosine of angle between them. Then this angle is used to estimate effectivity
> etc.
>
> Victor
>
> >
> > --------------------------------------------------------------------------
> > Michael Sievers
> > Michael.Sievers@desy.de
> > --------------------------------------------------------------------------
> > esa$ gcc -Wall -o ariane5 ariane4.c
> > ariane4.c: 666: warning: long float implicitly truncated to unsigned type
> > esa$ ariane5
>
> --
> Victor M. Perevoztchikov perev@bnl.gov perev@vxcern.cern.ch
> Brookhaven National Laboratory MS 510A PO Box 5000 Upton NY 11973-5000
> tel office : 631-344-7894; fax 631-344-4206; home 631-345-2690
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