Rivet analyses

title: LHCB_2016_I1504058

Measurement of the $b$-quark production cross-section in 7 and 13 TeV $pp$ collisions

Experiment: LHCB (LHC)

Inspire ID: 1504058

Status: VALIDATED

Authors: - Gino Daniels - Lars Kolk - Julian Boelhauve

References: - Phys.Rev.Lett. 118 (2017) 5, 052002 - Phys.Rev.Lett. 119 (2017) 16, 169901 (erratum) - DOI:10.1103/PhysRevLett.118.052002 - DOI:10.1103/PhysRevLett.119.169901 (erratum) - arXiv: 1612.05140

Beams: p+ p+

Beam energies: (3500.0, 3500.0); (6500.0, 6500.0)GeV

Run details: - Minimum-bias proton-proton interactions at 7 or 13 TeV centre-of-mass energy.

Measurements of the cross section for producing $b$ quarks in the reaction $pp \to b\overline{b}X$ are reported in 7 and 13 TeV collisions at the LHC as a function of the pseudorapidity $\eta$ in the range $2 < \eta < 5$ covered by the acceptance of the LHCb experiment. The measurements are done using semileptonic decays of $b$-flavored hadrons decaying into a ground-state charmed hadron in association with a muon. The cross sections in the covered $\eta$ range are $72.0 \pm 0.3 \pm 6.8$ and $154.3 \pm 1.5 \pm 14.3\,\mathrm{\mu b}$ for 7 and 13 TeV. The ratio is $2.14 \pm 0.02 \pm 0.13$, where the quoted uncertainties are statistical and systematic, respectively. The agreement with theoretical expectation is good at 7 TeV, but differs somewhat at 13 TeV. The measured ratio of cross sections is larger at lower $\eta$ than the model prediction.

Source code:LHCB_2016_I1504058.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief b-quark production in 7 and 13 TeV pp collisions class LHCB_2016_I1504058 : public Analysis {

public:

RIVET_DEFAULT_ANALYSIS_CTOR(LHCB_2016_I1504058);

void init() {
  // Check energy of input file and book corresponding histogram
  if (isCompatibleWithSqrtS(7000 * GeV))
    _sqs = 0;
  else if (isCompatibleWithSqrtS(13000 * GeV))
    _sqs = 1;
  if (_sqs < 0 && !merging()) {
    throw BeamError("Invalid beam energy for " + name() + "\n");
  }
  book(_b_quark_hist[0], 1, 1, 1);
  book(_b_quark_hist[1], 2, 1, 1);
  // Select pseudorapidity range
  declare(UnstableParticles(Cuts::absetaIn(2.0, 5.0)), "UPs");
}

void analyze(const Event& ev) {
  // Apply UnstableParticles projection to get entire decay chain of every particle
  const UnstableParticles& unst_parts = apply<UnstableParticles>(ev, "UPs");
  for (const Particle& part : unst_parts.particles()) {
    // Select beauty hadrons
    if (!(PID::isBottomHadron(part.pid()))) continue;

    // Skip bottomonia (excluded from definition) and Bc+ meson (ignored in
    // measurement)
    if ((PID::isQuarkonium(part.pid())) || (part.abspid() == PID::BCPLUS)) continue;

    // Veto beauty hadrons w/ beauty hadron child (pick only children)
    if (part.isLastWith(hasBottom)) continue;

    // Double sample size by taking absolute value and then scale by 0.5 due to LHCb
    // being one-sided
    double eta = part.abseta();

    // Scale again by 0.5 to get mean of beauty quarks and antiquarks
    _b_quark_hist[_sqs]->fill(eta, 0.25);
  }
}

void finalize() {
  // Compute scale factor with inelastic cross-section from input file and sum of
  // weights (corresponds to number of events in input file) and do not modify it
  // for using symmetric LHCb phase space as taken into account by histogram count
  scale(_b_quark_hist, crossSection() / microbarn / sumOfWeights());

  // compute ratio of b quark productions at 13 and 7 TeV (during merge)
  if (_b_quark_hist[0]->effNumEntries() != 0. && _b_quark_hist[1]->effNumEntries() != 0.) {
    Estimate1DPtr tmp;
    book(tmp, 3, 1, 1);
    divide(_b_quark_hist[1], _b_quark_hist[0], tmp);
  }
}

Histo1DPtr _b_quark_hist[2];
int _sqs = -1;

};

RIVET_DECLARE_PLUGIN(LHCB_2016_I1504058); } ```