Rivet analyses

title: LHCB_2017_I1621811

Differential Decay rates for $\Lambda_b^0\to \Lambda_c^+ \mu^-\bar{\nu}_\mu$

Experiment: LHCB (LHC)

Inspire ID: 1621811

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 96 (2017) 11, 112005

Beams: * *

Beam energies: ANY

Run details: - Any process producing Lambda_b0 baryons, originally pp

Differential decay rates for semileptonic $\Lambda_b^0\to \Lambda_c^+ \mu^-\bar{\nu}_\mu$ decays

Source code:LHCB_2017_I1621811.cc

```c++ // -- C++ --

include "Rivet/Analysis.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief Lambda_b0 -> Lambda_c+ semi-leptonic class LHCB_2017_I1621811 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(LHCB_2017_I1621811);


/// @name Analysis methods
/// @{

/// Book histograms and initialise projections before the run
void init() {

  // Initialise and register projections
  declare(UnstableParticles(), "UFS");

  // Book histograms
  book(_h_q2, 1, 1, 1);
}

// Calculate the Q2 using mother and daugher meson
double q2(const Particle& B, int mesonID) {
  FourMomentum q = B.mom() - select(B.children(), Cuts::pid == mesonID)[0];
  return q * q;
}

// Check for explicit decay into pdgids
bool isSemileptonicDecay(const Particle& mother, vector<int> ids) {
  // Trivial check to ignore any other decays but the one in question modulo photons
  const Particles children = mother.children(Cuts::pid != PID::PHOTON);
  if (children.size() != ids.size()) return false;
  // Check for the explicit decay
  return all(ids, [&](int i) { return count(children, hasPID(i)) == 1; });
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  for (const Particle& p : apply<UnstableParticles>(event, "UFS").particles(Cuts::abspid == 5122)) {
    if (p.pid() > 0) {
      if (isSemileptonicDecay(p, {4122, PID::MUON, PID::NU_MUBAR})) {
        _h_q2->fill(q2(p, 4122));
      }
    }
    else {
      if (isSemileptonicDecay(p, {-4122, PID::ANTIMUON, PID::NU_MU})) {
        _h_q2->fill(q2(p, -4122));
      }
    }
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  // normalize to unity
  normalize(_h_q2);
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h_q2;
/// @}

};

RIVET_DECLARE_PLUGIN(LHCB_2017_I1621811);

} ```