Rivet analyses

Differential Decay Rate for Bs0 → Ds*−μ+νμ

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 Bs0 → Ds*−μ+νμ decays.

Source code:LHCB_2020_I1787090.cc

// -*- 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);

}