[Rivet] Born and dressed level in Rivet

[Ulla Blumenschein]

Dear Andy,

I  would be very happy if that works out.
I cc to Oleg  and Tim, who did a comparison of various dressing
definitions recently.
Maybe Oleg would be interested to reproduce his plots with the
proposed new Rivet implementation, to check what the residual effect
is of the missing " from W/Z" requirement.
I have a technical question: Would only photons dircetly from
quarkonia decays be excluded?  Where would photons from leptons from
semileptonic HF decays end up?

Many thanks,
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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>
>
> --
> 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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