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Rivet analyses reference
ATLAS_2019_I1762584
Differential single diffractive cross sections at 8 TeV
Experiment: ATLAS, ALFA (LHC)
Inspire ID: 1762584
Status: VALIDATED
Authors:
References:
Beams: p+ p+
Beam energies: (4000.0, 4000.0) GeV
Run details:
- Single diffractive minimum bias events
A dedicated sample of Large Hadron Collider proton-proton collision data at centre-of-mass energy $\sqrt{s} = 8$ TeV is used to study inclusive single diffractive dissociation, $pp \to X p$. The intact final-state proton is reconstructed in the ATLAS ALFA forward spectrometer, while charged particles from the dissociated system X are measured in the central detector components. The fiducial range of the measurement is $-4.0 < \log_{10} \xi < -1.6$ and $0.016 < |t| < 0.43$ GeV$^{2}$, where $\xi$ is the proton fractional energy loss and $t$ is the squared four-momentum transfer. The total cross section integrated across the fiducial range is $1.59 \pm 0.13$ mb. Cross sections are also measured differentially as functions of $\xi$, $t$, and $\Delta \eta$, a variable that characterises the rapidity gap separating the proton and the system X. The data are consistent with an exponential $t$ dependence, d$\sigma$/d$t \approx e^{Bt}$ with slope parameter $B = 7.65 \pm 0.34$ GeV$^{-2}$. Interpreted in the framework of triple Regge phenomenology, the $\xi$ dependence leads to a pomeron intercept of $\alpha(0) = 1.07 \pm 0.09$.
Source code:
ATLAS_2019_I1762584.cc
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90 | // -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/ChargedFinalState.hh"
#include "Rivet/Projections/FinalState.hh"
namespace Rivet {
/// @brief single-diffractive cross-sections at 8 TeV
class ATLAS_2019_I1762584 : public Analysis {
public:
/// Constructor
DEFAULT_RIVET_ANALYSIS_CTOR(ATLAS_2019_I1762584);
void init() {
// Inner Detector (ID) charged final states
// charged tracks with pT>200MeV, |eta|<2.5
Cut track_cuts = Cuts::abseta < 2.5 && Cuts::pT > 0.2*GeV;
const ChargedFinalState tracks(track_cuts);
declare(tracks, "tracks");
// Forward Detector (FD) protons
// protons with 0.016<|t|/GeV^2<0.43: 0.126<pT/GeV<0.655
Cut proton_t_cuts = Cuts::pT>0.126/GeV && Cuts::pT<0.655/GeV ;
// protons with -4<log10(Xi)<-1.6: 0.016<|t|/GeV^2<0.43: 3899.52<E<3999.6
Cut proton_xi_cuts = Cuts::E>3899.52/GeV && Cuts::E<3999.6/GeV ;
const ChargedFinalState protons(Cuts::pid==PID::PROTON && proton_t_cuts && proton_xi_cuts ) ;
declare(protons, "protons");
// Book histograms
book(_h_dSigma_dDeltaEta, 1, 1, 1);
book(_h_dSigma_dAbsT, 2, 1, 1);
book(_h_dSigma_dLog10Xi, 3, 1, 1);
}
void analyze(const Event& event) {
// Retrieve charged tracks in Inner Detector
const ChargedFinalState& tracks = apply<ChargedFinalState>(event, "tracks");
// Retrieve protons in ALFA detector
const ChargedFinalState protons = apply<ChargedFinalState>(event, "protons");
// Veto Events with more than one tagged proton
if (protons.size()!=1) vetoEvent;
const Particle tagProton = protons.particles()[0];
// Calculate |t|
const double AbsT = (tagProton.pT()/GeV)*(tagProton.pT()/GeV);
// Calculate Log10(Xi)
const double Log10Xi = log10(1.-(tagProton.E()/GeV)/4000.);
//Calculate DeltaEta
const double EtaEdge = 2.5*tagProton.pz()/abs(tagProton.pz());
double DeltaEta = 5;
for (const Particle& p : tracks.particles()) {
double DeltaEta_track = abs(p.eta() - EtaEdge);
if (DeltaEta_track<DeltaEta) DeltaEta=DeltaEta_track;
}
// Fill histograms
_h_dSigma_dDeltaEta->fill(DeltaEta);
_h_dSigma_dAbsT->fill(AbsT);
_h_dSigma_dLog10Xi->fill(Log10Xi);
}
/// Normalise histograms to units of millibarn
void finalize() {
// norm to generated cross-section in mb (after cuts)
scale(_h_dSigma_dAbsT, crossSection()/millibarn/sumOfWeights());
scale(_h_dSigma_dLog10Xi, crossSection()/millibarn/sumOfWeights());
scale(_h_dSigma_dDeltaEta, crossSection()/millibarn/sumOfWeights());
}
private:
Histo1DPtr _h_dSigma_dAbsT, _h_dSigma_dLog10Xi, _h_dSigma_dDeltaEta;
};
DECLARE_RIVET_PLUGIN(ATLAS_2019_I1762584);
}
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