[Rivet] MC_HJETS and MC_HINC using ZFinder

[Andy Buckley]

On 26/03/15 11:38, Frank Siegert wrote:
> Hi Chris, Julia,
> 
> I think Julia has a point, namely that additionally to the mass range
> we can specify a mass target, which means that only the pair closest
> to the target is being kept. At least in the Higgs analyses this
> should be changed:
> - to 0 such that all possible pairs are kept for the user to decide, or
> - to 125 such that the correct pair is kept
> 
> Maybe we want to change this to 0 in general? I just don't know
> whether there are any analyses that rely on it being 91 at the moment,
> but we could simply set it explicitly to 91 in all existing analyses
> using the ZFinder such as to remain backward compatible.

This would be a possibility, but it *is* a ZFinder. If we think that
selecting the Z candidate closest to the known Z mass is reasonable in
all the existing analyses using ZFinder then I think we should keep it
there.

Seems to me that the main point is to change the range to one centred on
125*GeV in these MC_H* analyses, and to also explicitly set the mass
target either to 125 or to 0 in them. This use of ZFinder is the
exception, rather than a reason to change the default, IMHO.

Andy

PS. Thanks for the report, Julia: very helpful!


> On 26 March 2015 at 12:33, Chris Pollard <cpollard at cern.ch> wrote:
>> Hi Julia,
>>
>> It seems to me that the ZFinder is being set up to look between 115 and 125
>> GeV. Maybe it's time to center this range on 125 GeV.
>>
>> Chris
>>
>>
>> On Thu, Mar 26, 2015 at 9:12 AM, Hunt, Julia <julia.hunt at student.kit.edu>
>> wrote:
>>>
>>> Dear Rivet experts,
>>>
>>> I stumbled upon two lines concerning the use of the ZFinder in the two
>>> analyses MC_HJETS and MC_HINC. In these analyses, ZFinder is abused to get a
>>> Higgs boson.
>>>
>>> ZFinder.hh gives the following constructor:
>>>
>>> Rivet-2.2.0:
>>> 00036     ZFinder(const FinalState& inputfs,
>>> 00037             const Cut & cuts,
>>> 00038             PdgId pid,
>>> 00039             double minmass, double maxmass,
>>> 00040             double dRmax=0.1,
>>> 00041             ClusterPhotons clusterPhotons=CLUSTERNODECAY,
>>> 00042             PhotonTracking trackPhotons=NOTRACK,
>>> 00043             double masstarget=91.2*GeV);
>>>
>>> Rivet-1.9.0:
>>> 00037    ZFinder(const FinalState& inputfs,
>>> 00038            double etaMin, double etaMax,
>>> 00039            double pTmin,
>>> 00040            PdgId pid,
>>> 00041            double minmass, double maxmass,
>>> 00042            double dRmax, bool clusterPhotons, bool trackPhotons,
>>> 00043            double masstarget=91.2*GeV, bool useDecayPhotons=false);
>>>
>>>
>>> And the analyses don't seem to change the default masstarget:
>>> Rivet-2.2.0:
>>> MC_HINC.cc:
>>> 00025       ZFinder hfinder(FinalState(), cut, PID::TAU, 115*GeV, 125*GeV,
>>> 0.0, ZFinder::NOCLUSTER);
>>> MC_HJETS.cc:
>>> 00028       ZFinder hfinder(FinalState(), cut, PID::TAU, 115*GeV, 125*GeV,
>>> 0.0, ZFinder::NOCLUSTER);
>>>
>>> Rivet-1.9.0:
>>> MC_HINC.cc:
>>> 00026      ZFinder hfinder(fs, -3.5, 3.5, 25.0*GeV, TAU, 115.0*GeV,
>>> 125.0*GeV, 0.0, false, false);
>>> MC_HJETS.cc:
>>> 00027      ZFinder hfinder(fs, -3.5, 3.5, 25.0*GeV, TAU, 115.0*GeV,
>>> 125.0*GeV, 0.0, false, false);
>>>
>>> So it seems like the two analyses use the Z mass as a target when looking
>>> for a Higgs boson.
>>> Could there be any arguments against changing this masstarget parameter in
>>> the MC_HJETS and MC_HINC analyses?
>>>
>>> Best regards,
>>> Julia Hunt
>>> _______________________________________________
>>> Rivet mailing list
>>> Rivet at projects.hepforge.org
>>> https://www.hepforge.org/lists/listinfo/rivet
>>
>>
>>
>> _______________________________________________
>> Rivet mailing list
>> Rivet at projects.hepforge.org
>> https://www.hepforge.org/lists/listinfo/rivet
> _______________________________________________
> Rivet mailing list
> Rivet at projects.hepforge.org
> https://www.hepforge.org/lists/listinfo/rivet
> 


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