Plots for the Top Decay in 1000 TTbar events generated by Pythia

I have generated using the following pythia parameters:

'MSEL=0                  ! User defined processes',
'MSUB(81) = 1            ! qqbar to QQbar',
'MSUB(82) = 1            ! gg to QQbar',
'MSTP(7) = 6             ! flavour = top',
'PMAS(6,1) = 175.        ! top quark mass',

  • Signal Process I.D. for the TTbar generation.:
    TTbar_signal_process_id.png

How many t's did we get?

I ran on 1000 TTbar events and I got 2000 t (or t_bar) quarks:
  • The number of t's per event.:
    TTbar_numTs_1k.png
Each with 1000 t+ and 1000 t- (pdgId = 6 and -6, respectively):
  • The I.D. of t's per event.:
    TTbar_byType_1k.png

What do the t's decay to?

The daughters of the TTbar events:
1 = d quark,  2 = u quark,  3 = s quark,  4 = c quark,  5 = b quark,  6 = t quark
21 = gluon,  22 = photon,  23 = Z,  and 24 = W+
  • The daughters of the t's:
    DaughtersId_TTbar_1k.png
  • the daughters of the t+'s (absolute value):
    Tplus_DaughtersId_TTbar_1k.png
  • the daughters of the t-'s (absolute value):
    Tminus_DaughtersId_TTbar_1k.png

We expected t → Wb to lowest order. When I require only two daughters, I get 915 out of 1000 events with 1830 W's, 1825 b's, and 5 s's.

  • t's with only two daughters:
    DaughtersId_numD2cut_TTbar_1k.png

How many W's do we get?
In all cases, the t → W+X.
  • The number of times a t has a W as a daughter. (absolute value):
    DaughterIsW_TTbar_1k.png * PT of leptons from W boson decays:
    pt_EsWithMotherW_TTbar_1k.png

How many b's do we get?
I expected
  • The number of daughters that are b's.:
    DaughterIsBquark_TTbar_1k.png

If I require only one b quark in the final state I get 1994 of the 2000 t decays:

  • t's with 1 b's in the final state:
    OneBEvents_TTbar_1k.png
If I require zero b's in the final state I get 5 of the 2000 t decays:
  • t's with no b's in the final state:
    NoBEvents_TTbar_1k.png
If I require ≥ three b's in the final state I get 1 of the 2000 t decays:
  • t's with 3 b's in the final state:
    ThreeBEvents_TTbar_1k.png

Other quarks in the final state.
In a few TTbar events, we get qq(bar) pairs in the final state. Luckily they always come in pairs (even numbers). 6 events with u's in the final state.
  • t's with u's in the final state:
    DaughtersId_withDype_TTbar_1k.png
8 events with d's in the final state.
  • t's with d's in the final state:
    DaughtersId_withUtype_TTbar_1k.png
3 events with s's in the final state.
  • t's with s's in the final state:
    DaughtersId_withStype_TTbar_1k.png
3 events with c's in the final state.
  • t's with c's in the final state:
    DaughtersId_withCtype_TTbar_1k.png

What do the b's decay to?

The b quarks quickly hadronize into B mesons or Λ, Σ, or Ξ baryons. Here are the total number of b-type meson/baryons in the event (no attempt to associate them in a decay chain):
  • The b-type meson/baryons.:
    numB_mesons_baryons_TTbar_1k.png
The B mesons only:
pdgId Meson Type quark content J Γi / Γ to decay to lνl + anything (%)
511 B0 db(bar) 0 10.4
521 B+ ub(bar) 0 10.9
531 Bs sb(bar) 0 7.9
513 B0* db(bar) 1
523 B+* ub(bar) 1
533 Bs* sb(bar) 1

  • The b-type meson.:
    numB_mesons_TTbar_1k.png
The Λ, Σ, or Ξ baryons only:
pdgId Baryon Type quark content J
5112 Σb- ddb 1/2
5114 Σb-* ddb 3/2
5122 Λb0 bdu 1/2
5132 Ξb- bds 1/2
5232 Ξb0 bsu 1/2
5212 Σb0 bud 1/2
5214 Σb0* bud 3/2
5222 Σb+ buu 1/2
5224 Σb+* buu 3/2
5232 Ξb0 bsu 1/2
5312 Ξb- bsd 1/2
5314 Ξb-* bsd 3/2
5322 Ξb0 bsu 1/2
5324 Ξb0* bsu 3/2
  • The b-type baryons.:
    numB_baryons_TTbar_1k.png

The number of lowest energy b-type mesons/baryons
I have a total of 2079 B meson/baryons in the lowest lying energy state. This number seems high. I would have expected 1997 based on the number of generated b-quarks.

  • The lowest engery b-type meson/baryons:
    numB_lowestE_mesons_baryons_TTbar_1k.png
  • The lowest engery b-type mesons:
    numB_lowestE_mesons_TTbar_1k.png
  • The lowest energy b-type baryons:
    numB_lowestE_baryons_TTbar_1k.png

How many of these lowest energy b-type mesons/baryons decay leptonically?
  • The b-type mesons/baryons that decay leptonically:
    numBsToEMus_TTbar_1k.png
  • The b-type mesons that decay leptonically:
    numBs_mesons_toEMus_TTbar_1k.png
  • The b-type baryons that decay leptonically:
    numBs_baryons_toEMus_TTbar_1k.png

This seems to be consistent with the PGD:
# of B's that decay leptonically / # of lowest energy B's  =  423 / 2079 = 0.2035
PDG value for B hadron to e/μ decays is ≅ 0.205

What's going on with the C's?

Another significant source of leptons is from the semi-leptonic decay of C-type hardrons. To see this, we find the number of lowest lying energy C-hadrons (hadrons that are not excited such as D*+).
  • The lowest energy C hadrons:
    numC_lowestE_TTbar_1k.png
  • The lowest energy C meson:
    numC_lowestE_mesons_TTbar_1k.png
  • The lowest energy C baryons:
    numC_lowestE_baryons_TTbar_1k.png

We compare them to the number of C hadrons that have al least one charged lepton in the final state (in this case, I only consider the e and μ case).

How many of the lowest energy b-type hadrons decay to c-type hadron?
  • The number of B hadrons the decay to C hadrons + stuff:
    numBs_toCplusStuff_TTbar_1k.png
Of these c-type hadrons, how many decay leptonically?
  • The number of C hadrons that decay semileptonically:
    numC_toEmus_TTbar_1k.png
  • The number of C mesons that decay semileptonically:
    numC_mesons_toEmus_TTbar_1k.png
  • The number of C baryons that decay semileptonically:
    numC_baryons_toEmus_TTbar_1k.png

As a cross check, how many of the e/μ's in the final state have a C hadron mother? The plot below shows that we seem to be off by 2 leptons (507 C hadrons from the above plot but 509 e/μ's from the plot below).
  • The number of leptons with a C hadron mother.:
    numLs_motherIsC_TTbar_1k.png

If we look at the lowest lying C meson plot more closely, we see one state that is a lowest lying energy C hadron. We have four leptons that decayed from a ccbar bound state with j = 1 (pdgId = 443). We can see that the ccbar states annihilated to form a j = 1 photon (so the ccbar hadron must be in the j = 1 state to do this) and then pair creates into a lepton pair. It does this twice so instead of these two ccbar pairs decaying into a lepton and lepton neutrinio, we have the fully leptonically decay leaving us with two e/μ pair. This give is an extra two leptons in the lepton collection than naively expected.
  • The number of leptons that have a c cbar pair mother.:
    numLs_motherIs443_TTbar_1k.png
This seems to be consistent with the PGD:
# of C's that decay leptonically / # of lowest energy C's  =  507 / 2668 = 0.190
PDG value for C hadron to e/μ decays is ≅ 0.175

pT distribution of the two type of leptons

Here we plot the e/μ's pt distribution from B hadron decays, C hadron decays, and B hadrons decaying to C hadrons decaying to leptons.
  • PT of leptons from B hadron decays:
    pt_BsToEMus_TTbar_1k.png
  • PT of leptons from C hadron decays:
    pt_CsToEMus_TTbar_1k.png
  • PT of leptons from B and C hadron decays:
    pt_BsCsToEMus_TTbar_1k.png

-- RyanKelley - 21 Jan 2008

Topic attachments
I Attachment Action Size Date Who Comment
pngpng DaughterIsBquark_TTbar_1k.png manage 9.8 K 2008/01/11 - 19:28 RyanKelley The number of daughters are b's.
pngpng DaughterIsW_TTbar_1k.png manage 12.2 K 2008/01/11 - 19:24 RyanKelley The number of times a t has a W as a daughter.
pngpng DaughtersId_TTbar_1k.png manage 8.8 K 2008/01/11 - 19:30 RyanKelley The daughters of the t's
pngpng DaughtersId_numD2cut_TTbar_1k.png manage 10.0 K 2008/01/11 - 19:29 RyanKelley t's with only two daughters
pngpng DaughtersId_numDgreater2cut_TTbar_1k.png manage 9.4 K 2008/01/11 - 19:29 RyanKelley t's with > 2 daughters
pngpng DaughtersId_withCtype_TTbar_1k.png manage 9.7 K 2008/01/11 - 19:30 RyanKelley t's with c's in the final state
pngpng DaughtersId_withDype_TTbar_1k.png manage 9.8 K 2008/01/11 - 19:30 RyanKelley t's with d's in the final state
pngpng DaughtersId_withStype_TTbar_1k.png manage 9.6 K 2008/01/11 - 19:31 RyanKelley t's with s's in the final state
pngpng DaughtersId_withUtype_TTbar_1k.png manage 9.8 K 2008/01/11 - 19:31 RyanKelley t's with u's in the final state
pngpng NoBEvents_TTbar_1k.png manage 9.6 K 2008/01/11 - 19:31 RyanKelley t's with no b's in the final state
pngpng OneBEvents_TTbar_1k.png manage 9.6 K 2008/01/11 - 20:20 RyanKelley t's with 1 b's in the final state
pngpng TTbar_byType_1k.png manage 8.7 K 2008/01/11 - 19:34 RyanKelley The I.D. of t's per event.
pngpng TTbar_numTs_1k.png manage 8.8 K 2008/01/11 - 19:33 RyanKelley The number of t's per event.
pngpng TTbar_signal_process_id.png manage 11.8 K 2008/01/11 - 19:34 RyanKelley Signal Process I.D. for the TTbar generation.
pngpng ThreeBEvents_TTbar_1k.png manage 10.6 K 2008/01/11 - 19:32 RyanKelley t's with 3 b's in the final state
pngpng Tminus_DaughtersId_TTbar_1k.png manage 9.8 K 2008/01/11 - 19:32 RyanKelley the daughters of the t-'s
pngpng Tplus_DaughtersId_TTbar_1k.png manage 9.9 K 2008/01/11 - 19:33 RyanKelley the daughters of the t+'s
pngpng numB_baryons_TTbar_1k.png manage 11.6 K 2008/01/15 - 18:06 RyanKelley The b-type baryons.
pngpng numB_lowestE_baryons_TTbar_1k.png manage 11.0 K 2008/01/15 - 19:19 RyanKelley The lowest energy b-type baryons.
pngpng numB_lowestE_mesons_TTbar_1k.png manage 11.0 K 2008/01/15 - 19:18 RyanKelley The lowest engery b-type meson.
pngpng numB_lowestE_mesons_baryons_TTbar_1k.png manage 11.4 K 2008/01/15 - 19:17 RyanKelley The lowest engery b-type meson/baryons.
pngpng numB_mesons_TTbar_1k.png manage 11.2 K 2008/01/15 - 18:06 RyanKelley The b-type meson.
pngpng numB_mesons_baryons_TTbar_1k.png manage 9.9 K 2008/01/15 - 18:04 RyanKelley The b-type meson/baryons.
pngpng numBsToEMus_TTbar_1k.png manage 10.7 K 2008/01/15 - 19:33 RyanKelley The b-type mesons/baryons that decay leptonically
pngpng numBs_baryons_toEMus_TTbar_1k.png manage 10.9 K 2008/01/21 - 20:47 RyanKelley The b-type baryons that decay leptonically
pngpng numBs_mesons_toEMus_TTbar_1k.png manage 11.0 K 2008/01/21 - 20:46 RyanKelley The b-type mesons that decay leptonically
pngpng numBs_toCplusStuff_TTbar_1k.png manage 11.5 K 2008/01/21 - 22:34 RyanKelley The number of B hadrons the decay to C hadrons + stuff
pngpng numC_baryons_toEmus_TTbar_1k.png manage 10.2 K 2008/01/21 - 22:09 RyanKelley The number of C baryons that decay semileptonically
pngpng numC_lowestE_TTbar_1k.png manage 12.0 K 2008/01/21 - 21:18 RyanKelley The lowest energy C hadrons.
pngpng numC_lowestE_baryons_TTbar_1k.png manage 11.2 K 2008/01/21 - 21:19 RyanKelley The lowest energy C baryons.
pngpng numC_lowestE_mesons_TTbar_1k.png manage 10.9 K 2008/01/21 - 21:19 RyanKelley The lowest energy C meson.
pngpng numC_mesons_toEmus_TTbar_1k.png manage 12.2 K 2008/01/21 - 21:59 RyanKelley The number of C mesons that decay semileptonically
pngpng numC_toEmus_TTbar_1k.png manage 10.7 K 2008/01/21 - 21:59 RyanKelley The number of C hadrons that decay semileptonically
pngpng numLs_motherIs443_TTbar_1k.png manage 10.8 K 2008/01/21 - 22:31 RyanKelley The number of leptons that have a c cbar pair mother.
pngpng numLs_motherIsC_TTbar_1k.png manage 12.2 K 2008/01/21 - 22:31 RyanKelley The number of leptons with a C hadron mother.
pngpng pt_BsCsToEMus_TTbar_1k.png manage 16.0 K 2008/01/21 - 23:52 RyanKelley PT of leptons from B and C hadron decays
pngpng pt_BsToEMus_TTbar_1k.png manage 13.3 K 2008/01/21 - 23:39 RyanKelley PT of leptons from B hadron decays
pngpng pt_CsToEMus_TTbar_1k.png manage 13.1 K 2008/01/21 - 23:42 RyanKelley PT of leptons from B to C hadron decays
pngpng pt_EsWithMotherW_TTbar_1k.png manage 9.4 K 2008/01/21 - 23:53 RyanKelley PT of leptons from W boson decays
Topic revision: r8 - 2008/01/22 - 02:34:25 - RyanKelley
 
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