[Rivet] Born and dressed level in Rivet

[Ulla Blumenschein]

Hi Holger,

Many thanks, this sound like a good start. I hope I will soon be able
to compare this definition with the currently used definition in SM
where we request the photons to come from the W/Z/lepton, depending on
the generator..

Cheers, Ulla



On Thu, Nov 7, 2013 at 5:18 PM, Holger Schulz
<hschulz at physik.hu-berlin.de> wrote:
> On 07/11/13 09:34, Ulla Blumenschein wrote:
>
> 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...
>
> Hi Ulla,
>
> not sure if it helps much but these are PDGIds I currently use to reject
> photons
> of tau and hadron decays:
>
> int hadronsandtaus[73] = {15, 111, 113, 115, 211, 213, 215, 221, 223, 225,
> 313,
>         315, 323, 325, 331, 333, 411, 413, 421, 423, 425, 431, 433, 511,
> 513,
>         521, 523, 531, 533, 551, 1114, 2103, 2114, 2203, 2212, 2214, 2224,
> 3114,
>         3212, 3324, 4132, 4312, 4322, 5122, 5312, 5322, 10213, 10221, 10223,
>         10311, 10313, 10321, 10323, 10333, 10411, 10423, 10433, 12112,
> 12212,
>         13222, 20113, 20213, 20223, 20313, 20323, 20413, 20423, 20433,
> 23122,
>         100443, 9000111, 9000211, 9010221};
>
>
> This list is based on a study where I looked at Sherpa 1.3.1 samples, both
> ee and mumu,
> and checked what motherPDGids do photons (status=1) have that fall into the
> dressing cone of
> 0.1.
>
> I was lazy and used the absolute values of the pdgids.
>
> Not sure if this list is complete, what I found though as that the variety
> of photonic hadron
> decays is much larger in Sherpa than it is in Pythia, which, according to
> Marek Schönherr,
> is due to the hadron decay module in sherpa using full multiplets which
> Pythia8 does not.
> E.g. you won't find any photonic a_0 decays in Pythia8.
>
> Cheers,
> Holger
>
> 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
> /_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/
>
> _______________________________________________
> Rivet mailing list
> Rivet at projects.hepforge.org
> 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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