void standaloneBoxGen(double pabs, int nevents, double fThetaMin, double fThetaMax, TString output_filename, double seed = 123456.) {
  double mp = 0.938272;
  double fPhiMin = 0.0;
  double fPhiMax = 360.0;

  TClonesArray ca("TParticle", 1);
  TClonesArray *pars = &ca;

  TFile *f = new TFile(output_filename, "RECREATE");

  TTree *t = new TTree("data", "data");
  t->Branch("Particles", &pars);

  gRandom->SetSeed(seed);

  //boost::progress_display show_progress(nevents);

  for (unsigned int i = 0; i < nevents; i++) {
    //double theta = tmp->GetRandom(gen_range_low, gen_range_high) / 1000.0;
    //double phi = gRandom->Uniform(-C_PI, C_PI);

    double theta = gRandom->Uniform(fThetaMin,fThetaMax) * TMath::DegToRad();
    double phi = gRandom->Uniform(fPhiMin,fPhiMax) * TMath::DegToRad();

    double pz = pabs*TMath::Cos(theta);
    double pt = pabs*TMath::Sin(theta);

    double px = pt*TMath::Cos(phi);
    double py = pt*TMath::Sin(phi);

    TLorentzVector vertex(0, 0, 0, 0);
    TLorentzVector mom(px,
        py, pz,
        sqrt(mp * mp + pabs * pabs));

    TParticle p(-2212, 1, 0, 0, 0, 0, mom, vertex);
    new (ca[0]) TParticle(-2212, 1, 0, 0, 0, 0, mom, vertex);

    t->Fill();
    ca.Delete();

   // ++show_progress;
  }

  t->Write();
  f->Close();
}