Dielectron production in proton-proton collisions at $\sqrt{s}$ = 7 TeV

Abstract

The first measurement of e${}^{+}$e${}^{-}$ pair production at mid-rapidity ($|{\eta }_{\mathrm{e}}|$ $<$ 0.8) in pp collisions at $\sqrt{s}=7$ TeV with ALICE at the LHC is presented. The dielectron production is studied as a function of the invariant mass ($m_{\mathrm{ee}}$ $<$ 3.3 GeV/$c^2$), the pair transverse momentum ($p_{\mathrm{T},\mathrm{ee}}$ $<$ 8 GeV/$c$), and the pair transverse impact parameter (DCA${}_{\mathrm{ee}}$), i.e., the average distance of closest approach of the reconstructed electron and positron tracks to the collision vertex, normalised to its resolution. The results are compared with the expectations from a cocktail of known hadronic sources and are well described when PYTHIA is used to generate the heavy-flavour contributions. In the low-mass region (0.14 $<$ $m_{\mathrm{ee}}$ $<$ 1.1 GeV/$c^2$), prompt and non-prompt e${}^{+}$e${}^{-}$ sources can be separated via the DCA${}_{\mathrm{ee}}$. In the intermediate-mass region (1.1 $<$ $m_{\mathrm{ee}}$ $<$ 2.7 GeV/$c^2$), a double-differential fit to the data in $m_{\mathrm{ee}}$ and $p_{\mathrm{T},\mathrm{ee}}$ and a fit of the DCA${}_{\mathrm{ee}}$ distribution allow the total $\mathrm{c}\overline{\mathrm{c}}$ and $\mathrm{b}\overline{\mathrm{b}}$ cross sections to be extracted. Two different event generators, PYTHIA and POWHEG, can reproduce the shape of the two-dimensional $m_{\mathrm{ee}}$ and $p_{\mathrm{T},\mathrm{ee}}$ spectra, as well as the shape of the DCA${}_{\mathrm{ee}}$ distribution, reasonably well. However, differences in the $\mathrm{c}\overline{\mathrm{c}}$ and $\mathrm{b}\overline{\mathrm{b}}$ cross sections are observed when using the generators to extrapolate to full phase space. Finally, the ratio of inclusive to decay photons is studied via the measurement of virtual direct photons in the transverse-momentum range 1 $<$ $p_{\mathrm{T}}$ $<$ 8 GeV/$c$. This is found to be unity within the statistical and systematic uncertainties and consistent with expectations from next-to-leading order perturbative quantum chromodynamic calculations.

arXiv comment40 pages, 18 captioned figures, 6 tables, authors from page 35, published, figures at http://aliceinfo.cern.ch/ArtSubmission/node/4288

References in corpus (86)

• PYTHIA 6.4 Physics and Manual
• PYTHIA 6.2 Physics and Manual
• A Brief Introduction to PYTHIA 8.1
• A Unified Approach to the Classical Statistical Analysis of Small Signals
• A general framework for implementing NLO calculations in shower Monte Carlo programs: the POWHEG BOX
• A New Method for Combining NLO QCD with Shower Monte Carlo Algorithms
• Matching NLO QCD computations with Parton Shower simulations: the POWHEG method
• New parton distributions for collider physics
• HERWIG 6.5: an event generator for Hadron Emission Reactions With Interfering Gluons (including supersymmetric processes)
• Global QCD Analysis of Parton Structure of the Nucleon: CTEQ5 Parton Distributions
• Implications of CTEQ global analysis for collider observables
• Radiative energy loss and $p_{\perp }$-broadening of high energy partons in nuclei
• The chiral and deconfinement aspects of the QCD transition
• A Positive-Weight Next-to-Leading-Order Monte Carlo for Heavy Flavour Hadroproduction
• Tuning PYTHIA 8.1: the Monash 2013 Tune
• Tuning Monte Carlo Generators: The Perugia Tunes
• The QCD equation of state with dynamical quarks
• Performance of the ALICE Experiment at the CERN LHC
• Is there still any Tc mystery in lattice QCD? Results with physical masses in the continuum limit III
• The p_T Spectrum in Heavy-Flavour Hadroproduction
• The ALICE TPC, a large 3-dimensional tracking device with fast readout for ultra-high multiplicity events
• The CT10 NNLO Global Analysis of QCD
• The p_T Spectrum in Heavy-Flavour Photoproduction
• Performance of the ALICE VZERO system
• Alignment of the ALICE Inner Tracking System with cosmic-ray tracks
• First Measurement of the rho Spectral Function in High-Energy Nuclear Collisions
• Measurement of J/psi production in pp collisions at sqrt(s)=7 TeV
• Quark Coalescence for Charmed Mesons in Ultrarelativistic Heavy-Ion Collisions
• Detailed measurement of the e+e- pair continuum in p+p and Au+Au collisions at sqrt(s_NN)=200 GeV and implications for direct photon production
• Statistical hadronization of charm in heavy-ion collisions at SPS, RHIC and LHC
• Measurement of inelastic, single- and double-diffraction cross sections in proton-proton collisions at the LHC with ALICE
• Direct photon production in Pb-Pb collisions at $\sqrt{s_\rm{NN}}$ = 2.76 TeV
• Low-mass e+e- pair production in 158 A GeV Pb-Au collisions at the CERN SPS, its dependence on multiplicity and transverse momentum
• Low-Mass Dileptons at the CERN-SpS: Evidence for Chiral Restoration?
• Dilepton Radiation at the CERN Super Proton Synchrotron
• Neutral pion and $\eta$ meson production in proton-proton collisions at $\sqrt{s}=0.9$ TeV and $\sqrt{s}=7$ TeV
• Multiplicity dependence of charged pion, kaon, and (anti)proton production at large transverse momentum in p-Pb collisions at $\sqrt{{\text{s}}_{\mathrm{NN}}}$ = 5.02 TeV
• Rapidity and transverse momentum dependence of inclusive J/$\psi$ production in pp collisions at $\sqrt{s}=7$ TeV
• Signatures of Thermal Dilepton Radiation at RHIC
• Lattice QCD at non-zero temperature
• Study of the electromagnetic transition form-factors in η-> μ^+μ^-γand ω-> μ^+μ^-π^0 decays with NA60
• Enhanced Production of Low-Mass Electron Pairs in 40 AGeV Pb-Au Collisions at the CERN SPS
• Comprehensive Interpretation of Thermal Dileptons at the SPS
• Production of K${}^{\ast }$(892)${}^0$ and $\varphi$(1020) in pp collisions at $\sqrt{s}=7$ TeV
• NA60 results on thermal dimuons
• Measurement of D-meson production at mid-rapidity in pp collisions at $\sqrt{\mathbf{s}}=7$ TeV
• Modification of the rho meson detected by low-mass electron-positron pairs in central Pb-Au collisions at 158 A GeV/c
• Does the Charm Flow at RHIC?
• Is Rho-Meson Melting Compatible with Chiral Restoration?
• The Chiral Restoration Transition of QCD and Low Mass Dileptons
• Measurements of Dielectron Production in Au$+$Au Collisions at $\sqrt{s_{\mathrm{NN}}}$ = 200 GeV from the STAR Experiment
• QGP formation time and direct photons from heavy ion collisions
• Measurement of prompt J/psi and beauty hadron production cross sections at mid-rapidity in pp collisions at sqrt(s) = 7 TeV
• Evidence for radial flow of thermal dileptons in high-energy nuclear collisions
• Dielectron Mass Spectra from Au+Au Collisions at $\sqrt{s_{\mathrm{NN}}}$ = 200 GeV
• Lattice Simulations of the Thermodynamics of Strongly Interacting Elementary Particles and the Exploration of New Phases of Matter in Relativistic Heavy Ion Collisions
• Dilepton mass spectra in p+p collisions at sqrt(s)= 200 GeV and the contribution from open charm
• ${\Lambda }_{\mathrm{c}}^{+}$ production in pp collisions at $\sqrt{s}=7$ TeV and in p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV
• Fragmentation fractions of c and b quarks into charmed hadrons at LEP
• D${}_s^{+}$ meson production at central rapidity in proton-proton collisions at $\sqrt{s}$ = 7 TeV
• Low Mass Dimuons Produced in Relativistic Nuclear Collisions
• Thermal Dimuon Yields at NA60
• Measurement of electrons from beauty hadron decays in pp collisions at $\sqrt{s}=7$ TeV
• Precision study of the $\eta \to {\mu }^{+}{\mu }^{-}\gamma$ and $\omega \to {\mu }^{+}{\mu }^{-}{\pi }^0$ electromagnetic transition form-factors and of the $\rho \to {\mu }^{+}{\mu }^{-}$ line shape in NA60
• Modified Hagedorn formula including temperature fluctuation - Estimation of temperatures at RHIC experiments -
• Measurement of electrons from semileptonic heavy-flavour hadron decays in pp collisions at $\sqrt{s}$= 7 TeV
• Dilepton production in nucleus-nucleus collisions at top SPS energy within the Parton-Hadron-String Dynamics (PHSD) transport approach
• Direct photon production in d+Au collisions at sqrt(s_NN)=200 GeV
• Low mass dilepton production at ultrarelativistic energies
• Measurement of electrons from semileptonic heavy-flavor hadron decays in pp collisions at $\sqrt{s}=2.76$ TeV
• Low-Energy Thermal Photons from Meson-Meson Bremsstrahlung
• Dimuon transverse momentum spectra as a tool to characterize the emission region in heavy-ion collisions
• CT10 parton distributions and other developments in the global QCD analysis
• Production of the $\rho$(770)${}^0$ meson in pp and Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 2.76 TeV
• Production of Eta-Mesons in 200 AGeV/c S+S and S+Au Reactions
• Direct photon production at low transverse momentum in proton-proton collisions at $\sqrt{s}$ = 2.76 and 8 TeV
• Low mass dilepton radiation at RHIC
• Di-electron spectrum at mid-rapidity in $p+p$ collisions at $\sqrt{s}=200$ GeV
• Applicability of transverse mass scaling in hadronic collisions at the LHC
• Chiral symmetry restoration and deconfinement in QCD at finite temperature
• Cross section for $b\bar{b}$ production via dielectrons in d$+$Au collisions at $\sqrt{s_{{}_{NN}}}=200$ GeV
• Meson spectra and m_T scaling in p+p, d+Au and Au+Au collisions at \sqrtS_NN=200 GeV
• Electromagnetic Probes
• Measurements of $e^{+}{e}^{-}$ pairs from open heavy flavor in $p$+$p$ and $d$+$A$ collisions at $\sqrt{s_{NN}}=200$ GeV
• Transport Dynamics of Broad Resonances
• Dielectron production in Au$+$Au collisions at $\sqrt{s_{NN}}$=200 GeV

Cited by in corpus (11)

• Measurement of beauty and charm production in pp collisions at $\sqrt{s}=5.02$ TeV via non-prompt and prompt D mesons
• Intermediate mass dileptons as pre-equilibrium probes in heavy ion collisions
• Opportunities for new physics searches with heavy ions at colliders
• Dilepton Radiation from Strongly Interacting Systems
• Dielectron and heavy-quark production in inelastic and high-multiplicity proton-proton collisions at $\sqrt{s}$ = 13 TeV
• $b\bar{b}$ Kinematic Correlations in Cold Nuclear Matter
• Dielectron production in proton-proton and proton-lead collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV
• Soft-dielectron excess in proton-proton collisions at $\sqrt{s}$ = 13 TeV
• Low-mass dielectron measurements in pp, p-Pb, and Pb-Pb collisions with ALICE at the LHC
• Constraints on Kinetic Mixing of Dark Photons from Dilepton Spectra
• Shining a Light on the QGP - Electroweak Probes Experimental Summary