Rivet analyses

title: BABAR_2004_I656424

Helicity angle in $B\to D^+_{s1}(2460) \bar{D}$ decays

Experiment: BABAR (PEP-II)

Inspire ID: 656424

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.Lett. 97 (2006) 242001

Beams: * *

Beam energies: ANY

Run details: - Any process producing B mesons, originally Upsilon(4S) decays

Helicity angle in $B\to D^+_{s1}(2460) \bar{D}$ decays. The efficiency corrected, background subtracted data was read from Figure 3 in the paper.

Source code:BABAR_2004_I656424.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief B -> Ds1(2460) Dbar class BABAR_2004_I656424 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2004_I656424);


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

/// Book histograms and initialise projections before the run
void init() {
  // Initialise and register projections
  UnstableParticles ufs = UnstableParticles(Cuts::abspid == 511 || Cuts::abspid == 521);
  declare(ufs, "UFS");
  // histos
  book(_h, 1, 1, 1);
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  Particles BB = apply<UnstableParticles>(event, "UFS").particles();
  for (const Particle& p : BB) {
    if (p.children().size() != 2) continue;
    int sign = p.pid() / p.abspid();
    int iD = -sign * (p.abspid() - 100);
    Particle Ds1;
    if (p.children()[0].pid() == sign * 20433 && p.children()[1].pid() == iD) {
      Ds1 = p.children()[0];
    }
    else if (p.children()[1].pid() == sign * 20433 && p.children()[0].pid() == iD) {
      Ds1 = p.children()[1];
    }
    else
      continue;
    // find children of the Ds1 meson
    Particle Ds;
    if (Ds1.children().size() != 2) continue;
    if (Ds1.children()[0].abspid() == 431 && Ds1.children()[1].abspid() == 22)
      Ds = Ds1.children()[0];
    else if (Ds1.children()[1].abspid() == 431 && Ds1.children()[0].abspid() == 22)
      Ds = Ds1.children()[1];
    else
      continue;
    // boost to rest frame
    LorentzTransform boostB = LorentzTransform::mkFrameTransformFromBeta(p.momentum().betaVec());
    FourMomentum pDs1 = boostB.transform(Ds1.momentum());
    FourMomentum pDs = boostB.transform(Ds.momentum());
    LorentzTransform boostDs1 = LorentzTransform::mkFrameTransformFromBeta(pDs1.betaVec());
    pDs = boostDs1.transform(pDs);
    Vector3 axis = pDs1.p3().unit();
    double cTheta = axis.dot(pDs.p3().unit());
    _h->fill(cTheta);
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  normalize(_h, 1., false);
}

/// @}


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

};

RIVET_DECLARE_PLUGIN(BABAR_2004_I656424);

} ```