Rivet analyses

title: LHCB_2023_I2635083

$\pi^+\pi^-$ mass distribution in $B^0_s\to\psi(2S)\pi^+\pi^-$ and $B^0_s\to\chi_{c1}\pi^+\pi^-$

Experiment: LHCB (LHC)

Inspire ID: 2635083

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - arXiv: 2302.10629

Beams: * *

Beam energies: ANY

Run details: - Any process producing Bs0, originally pp

The $\pi^+\pi^-$ mass distribution in $B^0_s\to\psi(2S)\pi^+\pi^-$ and $B^0_s\to\chi_{c1}\pi^+\pi^-$ are measured. The data was extracted from the figures in the paper. There is no consensus as to the nature of the $\chi_{c1}(3872)$ $c\bar{c}$ state and therefore we taken its PDG code to be 9030443, i.e. the first unused code for an undetermined spin one $c\bar{c}$ state. This can be changed using the PID option if a different code is used by the event generator performing the simulation.

Source code:LHCB_2023_I2635083.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/DecayedParticles.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief B_s -> psi(2S)/X(3782) pi+pi- class LHCB_2023_I2635083 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(LHCB_2023_I2635083);


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

/// Book histograms and initialise projections before the run
void init() {
  // set the PDG code
  _pid = getOption<int>("PID", 9030443);
  // projections
  UnstableParticles ufs = UnstableParticles(Cuts::abspid == 531);
  declare(ufs, "UFS");
  DecayedParticles BS0(ufs);
  BS0.addStable(100443);
  BS0.addStable(_pid);
  declare(BS0, "BS0");
  // histos
  for (unsigned int ix = 0; ix < 2; ++ix) {
    book(_h[ix], 1, 1, 1 + ix);
  }
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  static const map<PdgId, unsigned int> mode1 = {{211, 1}, {-211, 1}, {100443, 1}};
  static const map<PdgId, unsigned int> mode2 = {{211, 1}, {-211, 1}, {_pid, 1}};
  DecayedParticles BS0 = apply<DecayedParticles>(event, "BS0");
  for (unsigned int ix = 0; ix < BS0.decaying().size(); ++ix) {
    unsigned int imode = 0;
    if (BS0.modeMatches(ix, 3, mode1))
      imode = 0;
    else if (BS0.modeMatches(ix, 3, mode2))
      imode = 1;
    else
      continue;
    const Particle& pip = BS0.decayProducts()[ix].at(211)[0];
    const Particle& pim = BS0.decayProducts()[ix].at(-211)[0];
    const double mpipi = (pip.mom() + pim.mom()).mass();
    _h[imode]->fill(mpipi);
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  normalize(_h, 1.0, false);
}

/// @}


/// @name Histograms
/// @{
int _pid;
Histo1DPtr _h[2];
/// @}

};

RIVET_DECLARE_PLUGIN(LHCB_2023_I2635083);

} ```