Dielectron and heavy-quark production in inelastic and high-multiplicity proton-proton collisions at $\sqrt{s_{\rm NN}}$ = 13 TeV

The ALICE collaboration Acharya, Shreyasi ; Torales - Acosta, Fernando ; Adamova, Dagmar ; et al.
Phys.Lett.B 788 (2019) 505-518, 2019.
Inspire Record 1672788 DOI 10.17182/hepdata.85869

The measurement of dielectron production is presented as a function of invariant mass and transverse momentum ($p_{\rm T}$) at midrapidity ($|y_{\rm e}|<0.8$) in proton-proton (pp) collisions at a centre-of-mass energy of $\sqrt{s}=13$ TeV. The contributions from light-hadron decays are calculated from their measured cross sections in pp collisions at $\sqrt{s}=7$ TeV or 13 TeV. The remaining continuum stems from correlated semileptonic decays of heavy-flavour hadrons. Fitting the data with templates from two different MC event generators, PYTHIA and POWHEG, the charm and beauty cross sections at midrapidity are extracted for the first time at this collision energy: ${\rm d}\sigma_{\rm c\bar{c}}/{\rm d}y|_{y=0}=974\pm138(\rm{stat.})\pm140(\rm{syst.})~\mu{\rm b}$ and ${\rm d}\sigma_{\rm b\bar{b}}/{\rm d}y|_{y=0}=79\pm14(\rm{stat.})\pm11(\rm{syst.})~\mu{\rm b}$ using PYTHIA simulations and ${\rm d}\sigma_{\rm c\bar{c}}/{\rm d}y|_{y=0}=1417\pm184(\rm{stat.})\pm204(\rm{syst.})~\mu{\rm b}$ and ${\rm d}\sigma_{\rm b\bar{b}}/{\rm d}y|_{y=0}=48\pm14(\rm{stat.})\pm7(\rm{syst.})~\mu{\rm b}$ for POWHEG. These values, whose uncertainties are fully correlated between the two generators, are consistent with extrapolations from lower energies. The different results obtained with POWHEG and PYTHIA imply different kinematic correlations of the heavy-quark pairs in these two generators. Furthermore, comparisons of dielectron spectra in inelastic events and in events collected with a trigger on high charged-particle multiplicities are presented in various $p_{\rm T}$ intervals. The differences are consistent with the already measured scaling of light-hadron and open-charm production at high charged-particle multiplicity as a function of $p_{\rm T}$. Upper limits for the contribution of virtual direct photons are extracted at 90% confidence level and found to be in agreement with pQCD calculations.

16 data tables

The dielectron cross section in inelastic pp collisions at $\sqrt{s}$ = 13 TeV as a function of invariant mass for $p_{\rm T,ee}$ < 6.0 GeV/$c$.

The dielectron cross section in inelastic pp collisions at $\sqrt{s}$ = 13 TeV as a function of pair transverse momentum for $m_{\rm ee}$ < 0.14 GeV/$c^{2}$.

The dielectron cross section in inelastic pp collisions at $\sqrt{s}$ = 13 TeV as a function of pair transverse momentum for 0.14 < $m_{\rm ee}$ < 0.7 GeV/$c^{2}$.

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

The ALICE collaboration Acharya, Shreyasi ; Torales - Acosta, Fernando ; Adamova, Dagmar ; et al.
JHEP 09 (2018) 064, 2018.
Inspire Record 1672792 DOI 10.17182/hepdata.83913

The first measurement of e$^+$e$^-$ pair production at mid-rapidity ($|\eta_{{\rm e}}|$ $<$ 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 ($m_{\rm ee}$ $<$ 3.3 GeV/$c^{2}$), the pair transverse momentum ($p_{\rm T,ee}$ $<$ 8 GeV/$c$), and the pair transverse impact parameter (DCA$_{{\rm ee}}$), 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 $<$ $m_{\rm ee}$ $<$ 1.1 GeV/$c^{2}$), prompt and non-prompt e$^+$e$^-$ sources can be separated via the DCA$_{\rm ee}$. In the intermediate-mass region (1.1 $<$ $m_{\rm ee}$ $<$ 2.7 GeV/$c^{2}$), a double-differential fit to the data in $m_{\rm ee}$ and $p_{\rm T,ee}$ and a fit of the DCA$_{\rm ee}$ distribution allow the total ${\rm c\overline c}$ and ${\rm b\overline b}$ cross sections to be extracted. Two different event generators, PYTHIA and POWHEG, can reproduce the shape of the two-dimensional $m_{\rm ee}$ and $p_{\rm T,ee}$ spectra, as well as the shape of the DCA$_{\rm ee}$ distribution, reasonably well. However, differences in the ${\rm c\overline c}$ and ${\rm b\overline b}$ 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 $<$ $p_{\rm T}$ $<$ 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.

11 data tables

Inclusive $e^+e^-$ cross section in pp collisions at $\sqrt{s}$ = 7 TeV in the ALICE acceptance as a function of $m_{\rm ee}$.

Inclusive $e^+e^-$ cross section in pp collisions at $\sqrt{s}$ = 7 TeV in the ALICE acceptance as a function of $p_{\rm T,ee}$ for $m_{\rm ee}$ < 0.14 GeV/$c^{2}$.

Inclusive $e^+e^-$ cross section in pp collisions at $\sqrt{s}$ = 7 TeV in the ALICE acceptance as a function of $\rm DCA_{ee}$ for 0.08 < $m_{\rm ee}$ < 0.14 GeV/$c^{2}$.

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Measurement of the double-differential high-mass Drell-Yan cross section in pp collisions at $\sqrt{s}$ = 8 TeV with the ATLAS detector

The ATLAS collaboration Aad, Georges ; Abbott, Brad ; Abdallah, Jalal ; et al.
JHEP 08 (2016) 009, 2016.
Inspire Record 1467454 DOI 10.17182/hepdata.75023

This paper presents a measurement of the double-differential cross section for the Drell-Yan $Z/\gamma^{*} \rightarrow \ell^{+} \ell^{-}$ and photon-induced $\gamma\gamma \rightarrow \ell^{+} \ell^{-}$ processes where $\ell$ is an electron or muon. The measurement is performed for invariant masses of the lepton pairs, $m_{\ell\ell}$, between 116 GeV and 1500 GeV, using a sample of 20.3 fb$^{-1}$ of pp collisions data at centre-of-mass energy of $\sqrt{s}$ = 8 TeV collected by the ATLAS detector at the LHC in 2012. The data are presented double differentially in invariant mass and absolute dilepton rapidity as well as in invariant mass and absolute pseudorapidity separation of the lepton pair. The single-differential cross section as a function of $m_{\ell\ell}$ is also reported. The electron and muon channel measurements are combined and a total experimental precision of better than 1% is achieved at low $m_{\ell\ell}$. A comparison to next-to-next-to-leading order perturbative QCD predictions using several recent parton distribution functions and including next-to-leading order electroweak effects indicates the potential of the data to constrain parton distribution functions. In particular, a large impact of the data on the photon PDF is demonstrated.

39 data tables

The combined Born-level single-differential cross section as a function of invariant mass. The measurements are listed together with the statistical and systematic uncertainties. The systematic uncertainties are separated into one uncorrelated, 35 correlated sources and the luminosity uncertainty. The sign of the uncertainty corresponds to a one standard deviation upward shift of the uncertainty source, where +/- means "+" and -/+ means "-".

The combined Born-level double-differential cross section as a function of invariant mass and absolute rapidity. The measurements are listed together with the statistical and systematic uncertainties. The systematic uncertainties are separated into one uncorrelated, 35 correlated sources and the luminosity uncertainty. The sign of the uncertainty corresponds to a one standard deviation upward shift of the uncertainty source, where +/- means "+" and -/+ means "-".

The combined Born-level double-differential cross section as a function of invariant mass and absolute pseudorapidity separation of the leptons. The measurements are listed together with the statistical and systematic uncertainties. The systematic uncertainties are separated into one uncorrelated, 35 correlated sources and the luminosity uncertainty. The sign of the uncertainty corresponds to a one standard deviation upward shift of the uncertainty source, where +/- means "+" and -/+ means "-".

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Search for contact interactions and large extra dimensions in the dilepton channel using proton-proton collisions at $\sqrt{s}$ = 8 TeV with the ATLAS detector

The ATLAS collaboration Aad, Georges ; Abbott, Brad ; Abdallah, Jalal ; et al.
Eur.Phys.J.C 74 (2014) 3134, 2014.
Inspire Record 1305430 DOI 10.17182/hepdata.65760

A search is conducted for non-resonant new phenomena in dielectron and dimuon final states, originating from either contact interactions or large extra spatial dimensions. The LHC 2012 proton-proton collision dataset recorded by the ATLAS detector is used, corresponding to 20 fb$^{-1}$ at $\sqrt{s}$ = 8 TeV. The dilepton invariant mass spectrum is a discriminating variable in both searches, with the contact interaction search additionally utilizing the dilepton forward-backward asymmetry. No significant deviations from the Standard Model expectation are observed. Lower limits are set on the $\ell\ell q q$ contact interaction scale $\Lambda$ between 15.4 TeV and 26.3 TeV, at the 95% credibility level. For large extra spatial dimensions, lower limits are set on the string scale $M_{S}$ between 3.2 TeV to 5.0 TeV.

10 data tables

Reconstructed dielectron mass distributions for data and the SM background estimate.

Reconstructed dimuon mass distributions for data and the SM background estimate.

Reconstructed $\cos\theta^*$ distributions for data and the SM background estimate in the dielectron channel.

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Measurement of the low-mass Drell-Yan differential cross section at sqrt(s)=7 TeV using the ATLAS detector

The ATLAS collaboration Aad, Georges ; Abajyan, Tatevik ; Abbott, Brad ; et al.
JHEP 06 (2014) 112, 2014.
Inspire Record 1288706 DOI 10.17182/hepdata.64183

The differential cross section for the process $Z/\gamma^*\rightarrow ll$ ($l=e,\mu$) as a function of dilepton invariant mass is measured in pp collisions at $\sqrt{s}=$ 7 TeV at the LHC using the ATLAS detector. The measurement is performed in the $e$ and $\mu$ channels for invariant masses between 26 GeV and 66 GeV using an integrated luminosity of 1.6 fb$^{-1}$ collected in 2011 and these measurements are combined. The analysis is extended to invariant masses as low as 12 GeV in the muon channel using 35 pb$^{-1}$ of data collected in 2010. The cross sections are determined within fiducial acceptance regions and corrections to extrapolate the measurements to the full kinematic range are provided. Next-to-next-to-leading-order QCD predictions provide a significantly better description of the results than next-to-leading-order QCD calculations, unless the latter are matched to a parton shower calculation.

13 data tables

The nominal electron-channel differential Born-level fiducial cross section. The statistical and systematic uncertainties are given for each invariant mass bin. The luminosity uncertainty 1.8% is not included.

The systematic uncertainties of the nominal electron-channel cross-section measurement. Some sources of uncertainty have both correlated and uncorrelated components. Correlated uncertainties arise from the uncertainty in the electroweak background contributions delta(e.w.)_cor, from corrections to the Monte Carlo modelling of the Z/gamma* pT spectra, delta(pTrw)_cor, the electron identification efficiency, delta(id)_cor1 and delta(id)_cor2, the reconstruction efficiency, delta(rec)_cor, and from the Geant4 simulation, delta(geant4)_cor. Uncorrelated uncertainties arise from the isolation and trigger efficiency corrections, delta(trig) and delta(iso) respectively, unfolding uncertainties, delta(res)_unf, and the statistical precision of the signal Monte Carlo, delta(MC). The electron identification efficiency uncertainties have several components other than the two largest correlated parts above. These additional components are all combined into a single uncorrelated error source delta(id)_unc. The uncertainty on the normalisation of the multijet background is given by delta(multijet). The luminosity uncertainty 1.8% is not included.

The nominal muon-channel differential Born-level fiducial cross section. The statistical, systematic, and total uncertainties are given for each invariant mass bin. The luminosity uncertainty 1.8% is not included.

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Measurement of the differential and double-differential Drell-Yan cross sections in proton-proton collisions at 7 TeV

The CMS collaboration Chatrchyan, Serguei ; Khachatryan, Vardan ; Sirunyan, Albert M ; et al.
JHEP 12 (2013) 030, 2013.
Inspire Record 1262319 DOI 10.17182/hepdata.62207

Measurements of the differential and double-differential Drell-Yan cross sections are presented using an integrated luminosity of 4.5(4.8) inverse femtobarns in the dimuon (dielectron) channel of proton-proton collision data recorded with the CMS detector at the LHC at $\sqrt{s}$ = 7 TeV. The measured inclusive cross section in the Z-peak region (60-120 GeV) is $\sigma(\ell \ell)$ = 986.4 +/- 0.6 (stat.) +/- 5.9 (exp. syst.) +/- 21.7 (th. syst.) +/- 21.7 (lum.) pb for the combination of the dimuon and dielectron channels. Differential cross sections $d\sigma/dm$ for the dimuon, dielectron, and combined channels are measured in the mass range 15 to 1500 GeV and corrected to the full phase space. Results are also presented for the measurement of the double-differential cross section $d^2\sigma/dm d |y|$ in the dimuon channel over the mass range 20 to 1500 GeV and absolute dimuon rapidity from 0 to 2.4. These measurements are compared to the predictions of perturbative QCD calculations at next-to-leading and next-to-next-to-leading orders using various sets of parton distribution functions.

10 data tables

Normalization factors for the cross section measurements from the Z-peak region (60 < M < 120 GeV) with associated uncertainties. The measurements are given in the muon, electron and combined channels. The three systematic uncertainties correspond to experimental, theoretical and luminosity.

The DY cross section measurements for the muon channel normalized to the Z-peak region, pre- and post-FSR, as measured in the full acceptance and for the CMS detector acceptance. The uncertainty indicates the experimental (statistical and systematic) uncertainties summed in quadrature with the theoretical uncertainty resulting from the model-dependent kinematic distributions inside each bin.

The DY cross section measurements for the electron channel normalized to the Z-peak region, pre- and post-FSR, as measured in the full acceptance and for the CMS detector acceptance. The uncertainty indicates the experimental (statistical and systematic) uncertainties summed in quadrature with the theoretical uncertainty resulting from the model-dependent kinematic distributions inside each bin.

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Measurement of the high-mass Drell--Yan differential cross-section in pp collisions at sqrt(s)=7 TeV with the ATLAS detector

The ATLAS collaboration Aad, Georges ; Abajyan, Tatevik ; Abbott, Brad ; et al.
Phys.Lett.B 725 (2013) 223-242, 2013.
Inspire Record 1234228 DOI 10.17182/hepdata.61422

This Letter reports a measurement of the high-mass Drell-Yan differential cross-section in proton-proton collisions at a centre-of-mass energy of 7 TeV at the LHC. Based on an integrated luminosity of 4.9 /fb, the differential cross-section in the Z/gamma* to e+e- channel is measured with the ATLAS detector as a function of the invariant mass, Mee, in the range 116 < Mee < 1500 GeV, for a fiducial region in which both the electron and the positron have transverse momentum pT > 25 GeV and pseudorapidity eta < 2.5. A comparison is made to various event generators and to the predictions of perturbative QCD calculations at next-to-next-to-leading order.

1 data table

Measured differential cross sections as a function of the di-electron mass for DY production at the Born and dressed levels.


Measurement of angular correlations in Drell-Yan lepton pairs to probe Z/gamma* boson transverse momentum at sqrt(s)=7 TeV with the ATLAS detector

The ATLAS collaboration Aad, Georges ; Abajyan, Tatevik ; Abbott, Brad ; et al.
Phys.Lett.B 720 (2013) 32-51, 2013.
Inspire Record 1204784 DOI 10.17182/hepdata.61421

A measurement of angular correlations in Drell-Yan lepton pairs via the phistar observable is presented. This variable probes the same physics as the Z/gamma* boson transverse momentum with a better experimental resolution. The Z/gamma*->e+e- and Z/gamma*->mu+mu- decays produced in proton--proton collisions at a centre-of-mass energy of sqrt(s) = 7 TeV are used. The data were collected with the ATLAS detector at the LHC and correspond to an integrated luminosity of 4.6 fb-1. Normalised differential cross sections as a function of phistar are measured separately for electron and muon decay channels. These channels are then combined for improved accuracy. The cross section is also measured double differentially as a function of phistar for three independent bins of the Z boson rapidity. The results are compared to QCD calculations and to predictions from different Monte Carlo event generators. The data are reasonably well described, in all measured Z boson rapidity regions, by resummed QCD predictions combined with fixed-order perturbative QCD calculations. Some of the Monte Carlo event generators are also able to describe the data. The measurement precision is typically better by one order of magnitude than present theoretical uncertainties.

7 data tables

The measured PHI* distributions for the dielectron events corrected back to the born level. The distributions are normalised to unity inidividually for each abs(yrap) bin and channel.

The measured PHI* distributions for the dielectron events corrected back to the dress level. The distributions are normalised to unity inidividually for each abs(yrap) bin and channel.

The measured PHI* distributions for the dielectron events corrected back to the bare particle level. The distributions are normalised to unity inidividually for each abs(yrap) bin and channel.

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Search for contact interactions and large extra dimensions in dilepton events from pp collisions at sqrt(s) = 7 TeV with the ATLAS detector

The ATLAS collaboration Aad, Georges ; Abajyan, Tatevik ; Abbott, Brad ; et al.
Phys.Rev.D 87 (2013) 015010, 2013.
Inspire Record 1198341 DOI 10.17182/hepdata.60277

A search for non-resonant new phenomena, originating from either contact interactions or large extra spatial dimensions, has been carried out using events with two isolated electrons or muons. These events, produced at the LHC in proton-proton collisions at sqrt(s) = 7 TeV, were recorded by the ATLAS detector. The data sample, collected throughout 2011, corresponds to an integrated luminosity of 4.9 and 5.0 fb-1 in the e+e- and mu+mu- channels, respectively. No significant deviations from the Standard Model expectation are observed. Using a Bayesian approach, 95% confidence limit lower limits ranging from 9.0 to 13.9 TeV are placed on the energy scale of llqq contact interactions in the left-left isoscalar model. Lower limits ranging from 2.4 to 3.9 TeV are also set on the string scale in large extra dimension models. After combination of these limits with results from a similar search in the diphoton channel, slightly more stringent limits are obtained.

7 data tables

Expected and observed numbers of events in the dielectron channel for the contact interactions search region. The yields are normalized to the Z peak control region and include predictions for SM backgrounds as well as for SM+CI with different CI scales for constructive (LAMBDA-) and destructive (LAMBDA+) interference. The errors quoted originate from both systematic uncertainties and limited MC statistics.

Expected and observed numbers of events in the dimuon channel for the contact interactions search region. The yields are normalized to the Z peak control region and include predictions for SM backgrounds as well as for SM+CI with different CI scales for constructive (LAMBDA-) and destructive (LAMBDA+) interference. The errors quoted originate from both systematic uncertainties and limited MC statistics.

Expected and observed 95% C.L. lower limits on the contact interaction energy scale LAMBDA for the dielectron and dimuon channels, as well as for the combination of those channels. Results are provided for constructive and destruc- tive interference as well as different choices of flat priors.

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Search for high-mass resonances decaying to dilepton final states in pp collisions at s**(1/2) = 7-TeV with the ATLAS detector

The ATLAS collaboration Aad, Georges ; Abajyan, Tatevik ; Abbott, Brad ; et al.
JHEP 11 (2012) 138, 2012.
Inspire Record 1185259 DOI 10.17182/hepdata.59903

The ATLAS detector at the Large Hadron Collider is used to search for high-mass resonances decaying to an electron-positron pair or a muon-antimuon pair. The search is sensitive to heavy neutral Z' gauge bosons, Randall-Sundrum gravitons, Z* bosons, techni-mesons, Kaluza-Klein Z/gamma bosons, and bosons predicted by Torsion models. Results are presented based on an analysis of pp collisions at a center-of-mass energy of 7 TeV corresponding to an integrated luminosity of 4.9/fb in the dielectron channel and 5.0/fb in the dimuon channel. A Z' boson with Standard Model-like couplings is excluded at 95 percent confidence level for masses below 2.22 TeV. A Randall-Sundrum graviton with coupling k/Mbar = 0.1 is excluded at 95 percent confidence level for masses below 2.16 TeV. Limits on the other models are also presented, including Technicolor and Minimal Z' Models.

14 data tables

Expected and observed number of events in the dielectron channel. The errors quoted include both statistical and systematic uncertainties.

Expected and observed number of events in the dimuon channel. The errors quoted include both statistical and systematic uncertainties.

Observed and predicted dielectron invariant mass (m_ee) distribution in the search region. The bin width is constant in log(m_ee).

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