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tunable ratio of ccbar and bbbar for embedding #2435

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wuctlby merged 3 commits into from
Aug 24, 2026
Merged

tunable ratio of ccbar and bbbar for embedding #2435

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5f0a79c
tunable ccbar and bbbar
wuctlby Aug 20, 2026
f9f9e7f
Update MC/config/PWGHF/external/generator/generator_pythia8_embed_hf.C
wuctlby Aug 21, 2026
1e3f8b2
Add test macro
wuctlby Aug 23, 2026
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60 changes: 60 additions & 0 deletions MC/config/PWGHF/external/generator/generator_pythia8_embed_hf.C
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Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,7 @@ namespace hf_generators
GapTriggeredBeauty, // --> GeneratorPythia8GapTriggeredBeauty: beauty enriched
GapTriggeredCharmAndBeauty, // --> GeneratorPythia8GapTriggeredCharmAndBeauty: charm and beauty enriched (with same ratio)
GapHF, // --> GeneratorPythia8GapHF
GapHFRatio, // --> GeneratorPythia8GapHF, quark list built from b/c ratio
NGenType
};
}
Expand Down Expand Up @@ -83,6 +84,12 @@ public:
LOG(info) << "********** Default number of HF signal events to be merged (updated by notifyEmbedding): " << mNumSigEvs;
mGeneratorEvHF = dynamic_cast<GeneratorPythia8GapTriggeredHF*>(GeneratorPythia8GapTriggeredBeauty(/*no gap trigger*/1, yQuarkMin, yQuarkMax, yHadronMin, yHadronMax, hadronPdgList, partPdgToReplaceList, freqReplaceList));
break;

case hf_generators::GapHFRatio:
LOG(info) << "********** [GeneratorPythia8EmbedHF] configuring GapHFRatio (custom b/c ratio) **********";
LOG(info) << "********** Default number of HF signal events to be merged (updated by notifyEmbedding): " << mNumSigEvs;
mGeneratorEvHF = dynamic_cast<GeneratorPythia8GapTriggeredHF*>(GeneratorPythia8GapHF(/*no gap trigger*/1, yQuarkMin, yQuarkMax, yHadronMin, yHadronMax, quarkPdgList, hadronPdgList, partPdgToReplaceList, freqReplaceList));
break;
default:
LOG(fatal) << "********** [GeneratorPythia8EmbedHF] bad configuration, fix it! **********";
break;
Expand Down Expand Up @@ -387,6 +394,44 @@ private:

};

// Helper: build quarkPdgList from bOverCRatio (= N(beauty)/N(charm), default 1 = 1:1)
// Integer b/c: taken directly; fractional b/c: reduced to nearest nB:nC with nC+nB <= 20
static std::vector<int> BuildQuarkListFromBOverC(float bOverCRatio)
{
if (bOverCRatio <= 0.f) {
LOG(fatal) << "bOverCRatio (b/c) must be > 0";
}
if (bOverCRatio > 19.f) {
bOverCRatio = 19.f;
LOG(warn) << "bOverCRatio (b/c) too large, using 19:1";
}else if (bOverCRatio < 1.f/19.f) {
bOverCRatio = 1.f/19.f;
LOG(warn) << "bOverCRatio (b/c) too small, using 1:19";
}

int nC = 1, nB = 1;
float bestErr = 1e9f;
for (int c = 1; c <= 19; ++c) {
int b = (int)std::lround(bOverCRatio * c);
if (b < 1 || c + b > 20) {
continue;
}
float err = std::fabs((float)b / c - bOverCRatio);
if (err < bestErr) {
bestErr = err;
nC = c;
nB = b;
}
}
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std::vector<int> list;
// Bresenham interleaving
int len = nC + nB;
for (int k = 0; k < len; ++k)
list.push_back((((k + 1) * nC) / len > (k * nC) / len) ? 4 : 5);
return list;
}

// Charm enriched
FairGenerator * GeneratorPythia8EmbedHFCharm(bool usePtHardBins = false, float yQuarkMin = -1.5, float yQuarkMax = 1.5, float yHadronMin = -1.5, float yHadronMax = 1.5, std::vector<int> quarkPdgList = {}, std::vector<int> hadronPdgList = {}, std::vector<std::array<int,2>> partPdgToReplaceList = {}, std::vector<float> freqReplaceList = {})
{
Expand Down Expand Up @@ -420,3 +465,18 @@ FairGenerator * GeneratorPythia8EmbedHFCharmAndBeauty(bool usePtHardBins = false
return myGen;
}

// Charm and beauty enriched with tunable b/c ratio
FairGenerator * GeneratorPythia8EmbedHFRatio(float bOverCRatio = 1.f, bool usePtHardBins = false, float yQuarkMin = -1.5, float yQuarkMax = 1.5, float yHadronMin = -1.5, float yHadronMax = 1.5, std::vector<int> hadronPdgList = {}, std::vector<std::array<int,2>> partPdgToReplaceList = {}, std::vector<float> freqReplaceList = {})
{
auto myGen = new GeneratorPythia8EmbedHF();

/// build the quark list from the b/c ratio
auto quarkPdgList = BuildQuarkListFromBOverC(bOverCRatio);

/// setup the internal generator for HF events
myGen->setupGeneratorEvHF(hf_generators::GapHFRatio,
usePtHardBins, yQuarkMin, yQuarkMax, yHadronMin, yHadronMax,
quarkPdgList, hadronPdgList, partPdgToReplaceList, freqReplaceList);

return myGen;
}
9 changes: 9 additions & 0 deletions MC/config/PWGHF/ini/GeneratorHF_D2H_ccbar_and_bbbar3_PbPb.ini
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Original file line number Diff line number Diff line change
@@ -0,0 +1,9 @@
#NEV_TEST> 10
### The external generator derives from GeneratorPythia8.
[GeneratorExternal]
fileName=${O2DPG_MC_CONFIG_ROOT}/MC/config/PWGHF/external/generator/generator_pythia8_embed_hf.C
funcName=GeneratorPythia8EmbedHFRatio(3.0)

[GeneratorPythia8]
config=${O2DPG_MC_CONFIG_ROOT}/MC/config/PWGHF/pythia8/generator/pythia8_charmhadronic_with_decays_Mode2_hardQCD_5TeV.cfg
includePartonEvent=true
4 changes: 2 additions & 2 deletions MC/config/PWGHF/pythia8/generator/pythia8_charmhadronic_with_decays_Mode2_hardQCD_5TeV.cfg
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Expand Up @@ -107,7 +107,7 @@ BeamRemnants:saturation 5
4122:addChannel = 1 0.04500 100 2224 -321 ### Λc+ -> Delta++ K- 1.08%
4122:addChannel = 1 0.09000 100 102134 211 ### Λc+ -> Lambda(1520) K- 2.20e-3
### Λc+ -> p K0S (36%)
4122:addChannel = 1 0.36000 0 2212 311 ### Λc+ -> p K0S 1.59%
4122:addChannel = 1 0.36000 0 2212 310 ### Λc+ -> p K0S 1.59%

@mfaggin mfaggin Aug 20, 2026

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In principle this should work in pythia, but did you check that this works?
The physics wants that only 4122:addChannel = 1 0.36000 0 2212 311 is correct, since K0, K0bar are the only states with a well-defined strangeness content, that materialize as K0s or K0L only in decay.
Did you check that the correct and expected decays are present, i.e. the fact that we have Lc decaying into p and K0s with K0s decaying in 2 pions?

@wuctlby wuctlby Aug 21, 2026 •
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Yes, I did a private test, and it works.
I checked the decay channels produced in one of the kinematic files, and they look good.
ScreenShot_2026-08-21_184841_592
Then I further checked the decay of produced K0s, as follows:
Found K(S)0 daughters for Lambdac+ decay: 111 (#pi^{0}) 111 (#pi^{0})
Found K(S)0 daughters for Lambdac+ decay: 211 (#pi^{+}) -211 (#pi^{-})

### Λc+ -> p K- π+ π0 (small, 3%)
4122:addChannel = 1 0.03000 0 2212 -321 211 111 ### Λc+ -> p K- π+ π0 (non-resonant) 4.6%
### Λc+ -> p π- π+ (12.50%)
Expand Down Expand Up @@ -256,7 +256,7 @@ BeamRemnants:saturation 5
431:onIfMatch = 221 211

### Λc -> pK0s
4122:onIfMatch = 2212 311
4122:onIfMatch = 2212 310
### Λc -> p K- π+ π0
4122:onIfMatch = 2212 321 211
### Λc -> p K*
Expand Down
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