[Rivet] Born and dressed level in Rivet

[Tim Martin]

Thanks Ulla,

I know of at least one analysis definitely using Dressed[All] - VBF Z
(and of course all our Rivet code!). I will try and get a more
extensive list however of who did what.

I agree that it would be nice to be able to show that Dressed[FSR] and
Dressed[NonDecay] are for all intensive purposes the same for the
generators we have used thus far to correct our data. But this
comparison may not be done in time.

Though we do have the results showing that Dressed[All] and
Dressed[FSR] are not the same when you push out into the more extreme
phase space, and that alone I believe we should draw peoples attention
to, considering these joint meetings happen only every few years.

Cheers, Tim.

On 10 October 2013 00:11, Ulla Blumenschein
<ublumenschein at googlemail.com> wrote:
> Hi Tim,
>
> I still think it would be useful to have a comparative study by that
> time.  I am without real internet connection this week and can not
> help with this.  I really like the new method but without input data I
> fear it won't be useful to discuss the proposal.
> I personally don't know anyone who is using the dressed-all
> definition, so it might be useful to have a list of analyses, since
> you state it is commonly used.
>
> Best,
> Ulla
>
> On Wed, Oct 9, 2013 at 3:51 PM, Tim Martin <tim.martin at cern.ch> wrote:
>> Hi all,
>>
>> I have tried to summarise this discussion for next weeks ATLAS
>> Higgs+Top+SM unfolding meeting.
>>
>> Try and make everyone aware of the little problem and how we're
>> proposing to fix it.
>>
>> For ATLAS people, the slides are on
>> https://indico.cern.ch/conferenceDisplay.py?confId=273212
>>
>> Cheers, Tim.
>>
>> On 9 October 2013 07:34, Ulla Blumenschein <ublumenschein at googlemail.com> wrote:
>>> Hi Andy,
>>>
>>>
>>> On Tuesday, October 8, 2013, Andy Buckley wrote:
>>>>
>>>> On 08/10/13 15:52, Ulla Blumenschein wrote:
>>>> > Hi David,
>>>> >
>>>> >
>>>> > On Tuesday, October 8, 2013, David Grellscheid wrote:
>>>> >
>>>> >     Hi Ulla,
>>>> >
>>>> >         We didn't identify the FSR photons experimentally but we
>>>> >         unfolded to a
>>>> >         reference where a  lepton was dressed with the respective
>>>> > technical
>>>> >         FSR implementation.
>>>> >
>>>> >
>>>> >     I'm sorry, I don't understand fully what you did there. The
>>>> >     "reference" you refer to is a certain MC run with a certain setup?
>>>> >     In that case isn't your unfolding dependent on that MC author's
>>>> >     choice of where to put photon emissions in that specific version of
>>>> >     the code?
>>>> >
>>>> >
>>>> > we depend on at least three authors of three generators' choices.
>>>> >
>>>> >
>>>> >         We checked that we get a similar correction in the
>>>> >         standard generators, (pythia, herwig, sherpa..).
>>>> >
>>>> >
>>>> >     That doesn't mean it makes physical sense to split FSR from ISR
>>>> > photons.
>>>> >
>>>> >
>>>> > No of course not. We are talking here merely in terms of dominating and
>>>> > negligible contributions to the collinear photon radiation.
>>>>
>>>> Recent QED modelling studies by Steve Muanza showed that there is a
>>>> substantial "ISR" QED structure in Z->l+l- events only in Pythia8 (with
>>>> or without Photos++ to produce the QED FSR). We didn't see the same
>>>> structure in invariant masses for Sherpa or Herwig++. Was Py8 included
>>>> in the three models used to derive the dressing correction?
>>>>
>>>
>>> No, only Pythia6 so far.
>>>
>>>>
>>>> In Steve's study there was still relatively little difference between
>>>> that and other models once observables were constructed from IR-safe
>>>> clustering (and there we/he explicitly excluded photons from hadron
>>>> decays as discussed here), so I suspect that as suggested the FSR will
>>>> turn out to be dominant.
>>>>
>>>> If there is no significant distinction between the two approaches, then
>>>> this sort of separation of photon origins is, I think, preferable to the
>>>> dependence so far on particular generators' schemes for representing QED
>>>> FSR. It's a lot more portable (unless a generator standard
>>>> representation is agreed upon -- good luck!) and I think physically less
>>>> contentious.
>>>>
>>>
>>> I personally agree.
>>>
>>> Cheers, Ulla
>>>
>>>>
>>>> Cheers,
>>>> Andy
>>>>
>>>> --
>>>> Dr Andy Buckley, Royal Society University Research Fellow
>>>> Particle Physics Expt Group, University of Glasgow / PH Dept, CERN
>>>
>>>
>>>
>>> --
>>> /_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/
>>>     Ulla Blumenschein
>>>     II Physik, Uni Goettingen
>>>     Friedrich-Hund-Platz 1, D01.110
>>>     phone: 0049-551-397645
>>> /_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/
>>
>>
>>
>> --
>> -+-+-+-+ Tim Martin +-+ ATLAS +-+-+-+-
>> Room 448A, University of Warwick, CV47AL
>> Tel: (+44) 0-24761-51769
>> Web: http://Tim-Martin.co.uk
>
>
>
> --
> /_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/
>     Ulla Blumenschein
>     II Physik, Uni Goettingen
>     Friedrich-Hund-Platz 1, D01.110
>     phone: 0049-551-397645
> /_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/



-- 
-+-+-+-+ Tim Martin +-+ ATLAS +-+-+-+-
Room 448A, University of Warwick, CV47AL
Tel: (+44) 0-24761-51769
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