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Rivet analyses reference
LHCB_2018_I1665223
Measurement of $pp$ inelastic cross-section at 13 TeV using prompt, long-lived particles in the LHCb fiducial phase-space
Experiment: LHCB (LHC)
Inspire ID: 1665223
Status: VALIDATED
Authors:
- Michael Schmelling
- Alex Grecu
References:
Beams: p+ p+
Beam energies: (6500.0, 6500.0) GeV
Run details:
- Proton-proton interactions at 13 TeV centre-of-mass energy. LHCb minimum bias, inelastic events.
LHCb measurement of the inelastic interaction cross-section in proton-proton collisions at $\sqrt{s}=13$ TeV. Events are selected if they contain at least one prompt long-lived charged particle with momentum $p > 2$ GeV$/c$ and pseudorapidity ($\eta$) in the range $2 < \eta < 5$. A particle is long-lived if its proper (mean) lifetime is larger than $0.3 \times 10^{-10}$ s, (proper $c\tau > 9$ mm) and it is prompt if it is produced directly in the $pp$ collision or if none of its ancestors is long-lived. This definition is recommended by the LHC Minimum Bias and Underlying Event working group. Prompt long-lived charged hadrons should be used themselves in vetoing events rather than their charged decay products (e.g. Sigma +/-, Xi and Omega decays are blocked).
Source code:
LHCB_2018_I1665223.cc
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86 | // -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/ChargedFinalState.hh"
namespace Rivet {
/// @brief Inelastic xsection in pp collisions at 13 TeV for charged particles in LHCb acceptance
class LHCB_2018_I1665223 : public Analysis {
public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(LHCB_2018_I1665223);
/// @name Analysis methods
//@{
/// Book histograms and initialise projections before the run
void init() {
// Register projection
declare(ChargedFinalState(Cuts::etaIn(ETAMIN, ETAMAX)), "lbCFS");
// Book histogram
book(_h_ppInel, 1, 1, 1);
}
/// Perform the per-event analysis
void analyze(const Event& event) {
// Eliminate non-inelastic events and empty events in LHCb
const ChargedFinalState& cfs = apply<ChargedFinalState>(event, "lbCFS");
if (cfs.particles().size() == 0) vetoEvent;
for (const Particle& myp : cfs.particles()) {
if (hasLongLivedParent(myp)) continue;
if (!isLongLivedParticle(myp)) continue;
// Only particles with p > 2 GeV measured
if (myp.momentum().p() < PMIN) continue;
// Histo gets filled only for inelastic events (at least one prompt charged particle)
_h_ppInel->fill(sqrtS());
break;
}
}
/// Normalise histograms etc., after the run
void finalize() {
scale(_h_ppInel, crossSection()/millibarn/sumOfWeights()); // norm to cross section (one-sided LHCb)
}
//@}
bool isLongLivedParticle(const Particle& p) {
// Stable long-lived final-state charged particles in LHCb
static const int stablePids[9] = {11,13,211,321,2212,3112,3222,3312,3334};
for (int stablePid : stablePids) {
if (p.abspid() == stablePid) return true;
}
return false;
}
bool hasLongLivedParent(const Particle& p) {
// List of PDG IDs for particle with lifetimes higher than 0.03 ns (3.E-11 s) - long lived particles according to LHC MB&UE WG
static const int longLivedPids[20] = {3334,3322,3312,3222,3122,3112,2212,2112,321,310,130,211,20022,480000000,11,12,13,14,16,22};
for (int longLivedPid : longLivedPids) {
if (p.hasParentWith(Cuts::abspid == longLivedPid)) return true;
}
return false;
}
/// @name Histogram
Histo1DPtr _h_ppInel;
/// Cut constants
const double ETAMIN = 2.0, ETAMAX = 5.0, PMIN = 2.0*GeV;
};
RIVET_DECLARE_PLUGIN(LHCB_2018_I1665223);
}
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