[Rivet] finalstate projection with assymetric beam

[Andy Buckley]

Hi Tanguy,

I'm finally getting time to implement these requests (for release in 
Rivet 2.5.0, which I hope will be available before long, and you would 
be welcome to beta-test).

Just to clarify this asqrtS() request: are you wanting to write an 
analysis which can be run with many different types of incoming nuclear 
beams, and automatically extract the number of nucleons from that code? 
There is actually a PID::A(pid) function which will do this (I feel I 
should give it a better name), so would that be sufficient for you? 
Adding a new Analysis::asqrtS() feels a bit too much of a cluttering of 
the interface for something that specific which can be done easily by 
hand... but I can be convinced otherwise!

Cheers,
Andy


On 22/01/16 17:46, Pierog, Tanguy (IKP) wrote:
> 	Hi Andy,
>
>> Thanks for the information -- we can certainly provide something. So the
>> centre-of-mass frame is to be the centre-of-mass of the incoming
>> particle system rather than something computed from a final state with
>> acceptance cuts. Should be straightforward for us to add.
>>
>
> 	Thanks, that will be useful.
>
>> Good to have feedback and suggestions!
>>
> 	Then some more ;-) ... it seams that running with nuclei is also not very
> common in RIVET yet :-P. For instance if a beam is properly defined as a
> nucleus (PDG code for nucleus) then SqrtS is calculated on the total energy
> of the nucleus instead of being calculated by Nucleon (ASqrtS). And since
> there is no function to extract the mass and the charge of a nucleus from
> it's Id it can not be done automatically. So it would be nice to have such
> functions available in RIVET and more important to have the SqrtS per nucleon
> and not the total one (I think nobody is using that so it can be the same
> SqrtS() function or to avoid anyconfusion you can call that ASqrtS() ).
>
> 	thanks and have a nice week-end
>
> 		Tanguy
>
>
>> Best wishes,
>> Andy
>>
>> On 18/01/16 10:37, Pierog, Tanguy (IKP) wrote:
>>> 	Hi Andy,
>>>
>>>> The only existing projection that does that is DISKinematics, I think.
>>>> We could make a projection like you mention, but everything that
>>>> projections do can also be done inside an analysis code, and since there
>>>> has not previously been a request for that functionality there was no
>>>> incentive for us to make a new feature that no-one wanted! But if you
>>>> would find this useful in *several* analyses -- so there is a chance of
>>>> some benefit from result caching as well as simplifying several analysis
>>>> codes -- then we can take this a bit further.
>>>
>>> 	The point is that many fixed target experiments plot the various
>>> observables in the center-of-mass frame (like rapidity or xf). So yes
>>> this will be used by several analysis and if you want RIVET to be used
>>> not only at LHC (there is still a lot of fixed target experiment at SPS
>>> or in other lab) this would be useful to help these collaboration to
>>> include their analysis in RIVET. Since we are involved in NA61 for
>>> instance I can push my colleagues to put their analysis on RIVET for
>>> instance.
>>>
>>>> We will probably need to iterate a bit to understand how the CoM frame
>>>> is to be defined, and whether it also needs to include some rotation
>>>> into a conventional alignment cf. our built-in HERA transformation.
>>>
>>> 	We can have a look at what is done in DISKinematics and try something
>>> ourself. It should not be complicated but it would be cleaner to have
>>> generic projection. In that case the CoM is simple (just the same
>>> projectile and target but boosted) and there is no a priori convention
>>> here (but technically the "exotic" particle is always the projectile but
>>> it is the same in the models).
>>>
>>>>> 	Actually I have the same question about the analysis we are doing.
>>>>> They are based on old data (80's and 90's) from collaboration which are
>>>>> not existing anymore. What is the policy in that case. Can it be
>>>>> distributed or should it get some approval from someone ? Do you have
>>>>> any idea ?
>>>>
>>>> We don't enforce a policy about analyses needing to be approved by
>>>> experiments, particularly not defunct ones. We just much *prefer* that
>>>> analyses being provided during an experiment's lifetime be written, or
>>>> at least be approved by that experiment, but an unofficial analysis is
>>>> far better than nothing. We'll happily take anything you provide!
>>>
>>> 	OK thanks. For the moment it is just a topic for bachelor student, but
>>> we find manpower we would like to increase our data base and why not
>>> putting it online.
>>>
>>> 	best regards
>>>
>>> 		Tanguy
>
>
>


-- 
Dr Andy Buckley, Lecturer / Royal Society University Research Fellow
Particle Physics Expt Group, University of Glasgow