Rivet analyses

title: LHCB_2020_I1787090

Differential Decay Rate for $B^0_s\to D_s^{*-} \mu^+\nu_\mu$

Experiment: LHCB (LHC)

Inspire ID: 1787090

Status: VALIDATED

Authors: - Peter Richardson

References: - JHEP 12 (2020) 144

Beams: * *

Beam energies: ANY

Run details: - Any process producing Bs0 mesons, originally pp

Differential decay rates for semileptonic $B^0_s\to D_s^{*-} \mu^+\nu_\mu$ decays.

Source code:LHCB_2020_I1787090.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief B_s0 -> D_s* semileptonic decay class LHCB_2020_I1787090 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(LHCB_2020_I1787090);


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

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

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

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

// Calculate the Q2 using mother and daugher meson
double w(const Particle& B, int mesonID) {
  Particle D = select(B.children(), Cuts::pid == mesonID)[0];
  FourMomentum q = B.mom() - D.mom();
  double q2 = q * q;
  return 0.5 * (sqr(B.mass()) + sqr(D.mass()) - q2) / B.mass() / D.mass();
}

// 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 == 531)) {
    if (p.pid() < 0) {
      if (isSemileptonicDecay(p, {433, PID::MUON, PID::NU_MUBAR})) {
        _h_w->fill(w(p, 433));
      }
    }
    else {
      if (isSemileptonicDecay(p, {-433, PID::ANTIMUON, PID::NU_MU})) {
        _h_w->fill(w(p, -433));
      }
    }
  }
}


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

/// @}


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

};

RIVET_DECLARE_PLUGIN(LHCB_2020_I1787090);

} ```