[Rivet] Born and dressed level in Rivet

[Ulla Blumenschein]

Hi Andy,

do you have a short technical outline for the new dressing
implementation (e.g. a list of  pid mothers to exclude?)
Since there seems to be no one else willing to do this, I fear I have
to  make a comparison with the old definition myself and sell it to
SM...

Many thanks in advance,
Ulla


On Thu, Oct 3, 2013 at 3:16 PM, Andy Buckley <andy.buckley at cern.ch> wrote:
> Hi Ulla, all,
>
> I've discussed this a bit with Daniel Froidevaux and think that it would
> make sense for us to at least add a flag to the ClusteredPhotons tool in
> Rivet to exclude photons which come from hadron decays. Taus are a bit
> of a borderline case, but that does not affect (current) EW measurements.
>
> This is not *exactly* the same definition, but I think that "only
> photons from W/Z" is hard to implement in a generator-unspecific way.
>
> Maybe Frank Siegert wants to comment more on this proposal to use the
> fromDecay() function in ClusteredPhotons, since he did most of the
> detailed work to put these W/ZFinders and related classes together.
>
> Re. the Born comparisons, I believe that the ATLAS W/Z analyses written
> so far *don't* compare to the Born-level results, since there *isn't* a
> generator-portable way to write them. I remember removing a
> generator-specific code along those lines in a previously submitted
> analysis for that reason: it's fine for ATLAS-internal versions of
> analyses but won't go into the public Rivet library.
>
> Hope that helps,
> Andy
>
> PS. For those who care, if we agree that that is a reasonable route, I
> propose that the exclude-decay-photons functionality would go into Rivet
> 2.0.1 or 2.0.2. The exact version depends on the extent to which we want
> to separate different types of change -- 2.0.1 might just be adding some
> "queued" analysis codes, or it could be a combination of that and some
> definition changes. The numbering does not really reflect anything about
> the timescales! But note that we'll only be making this change in the
> Rivet 2 series -- 1.x is in "maintenance mode".
>
>
> On 03/10/13 14:51, Roman Lysak wrote:
>>
>>  Hi Ulla,
>>
>> I think the Rivet authors are better to replay to your questions so I'm
>> cc-ing this to them.
>> Could anyone address Ulla's questions?
>>
>> Cheers,
>>   Roman
>>
>> On 10/03/2013 12:25 PM, Ulla Blumenschein wrote:
>>> Hi Roman,
>>>
>>> we have currently a discussion in SM about how to synchronize  the
>>> Atlas internal definition of dressed leptons with the Rivet
>>> implementation.
>>> Currently in SM, we sum all photons emitted from the W/Z decay
>>> products whereas Rivet sums all photons.
>>> With the extreme phase spaces which we access with 8TeV there are
>>> differences up to percentage level between these definitions due to
>>> pi0 decays from hadronic activity close to leptons.
>>>
>>> Is it possible to  implemet an alternate Z finder which can
>>> discriminate photon sources? I understand that this might be against
>>> the philosophy of Rivet (MC independence). Or are there other
>>> problems?
>>>
>>> Also the born level Z finder is not completely clear to me. I assumed
>>> so far that the born level is defined by different status codes in
>>> different MC generator, so how does Rivet handle this issue?
>>>
>>>
>>> Many thanks in advance,
>>> Ulla
>>>
>>>
>>>
>>>
>>>
>>> On Sun, Sep 15, 2013 at 7:46 PM, Roman Lysak <lysak at fzu.cz> wrote:
>>>>   Hi Ulla,
>>>>
>>>>
>>>>
>>>> On 09/12/2013 06:51 PM, Ulla Blumenschein wrote:
>>>>> Hi Roman,
>>>>>
>>>>> Could you explain how we define Born and dressed in a generator
>>>>> independent way in Rivet?
>>>>
>>>> it depends on the object type.
>>>> For example, for Z boson (similarly for W boson), you can specify
>>>> whether to
>>>> add photons (next to last one parameter in the constructor below) in
>>>> a given
>>>> radius (2nd next to last one parameter) around the leptons from Z
>>>> decay to
>>>> the Z boson 4-momentum.
>>>>
>>>>        //fiducial phase space + born level
>>>>        ZFinder zfinder_mu(-2.4, 2.4, 20, MUON, 66.0*GeV, 116.0*GeV, 0.1,
>>>> false, false);
>>>>        addProjection(zfinder_mu, "ZFinder_mu");
>>>>
>>>>        //for combined cross-sections (combined phase space + dressed
>>>> level)
>>>>        ZFinder zfinder_comb_mu(-2.5, 2.5, 20, MUON, 66.0*GeV,
>>>> 116.0*GeV, 0.1,
>>>> true, false);
>>>>
>>>>
>>>> Sorry for late response.
>>>>
>>>> Cheers,
>>>>    Roman
>>>>
>>>>
>>>>
>>>>> Cheers, Ulla
>>>>>
>>>>> /_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/
>>>>>       Ulla Blumenschein
>>>>>       II Physik, Uni Goettingen
>>>>>       Friedrich-Hund-Platz 1, D01.110
>>>>>       phone: 0049-551-397645
>>>>> /_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/
>>>>
>>>
>>>
>>
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>> http://www.hepforge.org/lists/listinfo/rivet
>
>
> --
> Dr Andy Buckley, Royal Society University Research Fellow
> Particle Physics Expt Group, University of Glasgow / PH Dept, CERN



-- 
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    Ulla Blumenschein
    II Physik, Uni Goettingen
    Friedrich-Hund-Platz 1, D01.110
    phone: 0049-551-397645
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