Showing papers by "D. P. C. Sankey published in 2018"
TL;DR: The performance of the missing transverse momentum reconstruction with the ATLAS detector is evaluated using data collected in proton–proton collisions at the LHC at a centre-of-mass energy of 13 TeV in 2015.
Abstract: The performance of the missing transverse momentum ( ETmiss ) reconstruction with the ATLAS detector is evaluated using data collected in proton-proton collisions at the LHC at a centre-of-mass energy of 13 TeV in 2015. To reconstruct ETmiss , fully calibrated electrons, muons, photons, hadronically decaying τ-leptons , and jets reconstructed from calorimeter energy deposits and charged-particle tracks are used. These are combined with the soft hadronic activity measured by reconstructed charged-particle tracks not associated with the hard objects. Possible double counting of contributions from reconstructed charged-particle tracks from the inner detector, energy deposits in the calorimeter, and reconstructed muons from the muon spectrometer is avoided by applying a signal ambiguity resolution procedure which rejects already used signals when combining the various ETmiss contributions. The individual terms as well as the overall reconstructed ETmiss are evaluated with various performance metrics for scale (linearity), resolution, and sensitivity to the data-taking conditions. The method developed to determine the systematic uncertainties of the ETmiss scale and resolution is discussed. Results are shown based on the full 2015 data sample corresponding to an integrated luminosity of 3.2fb-1 .
208 citations
TL;DR: In this article, a search was performed for resonant and non-resonant Higgs boson pair production in the $ \upgamma \ upgamma b\overline{b} $ final state.
Abstract: A search is performed for resonant and non-resonant Higgs boson pair production in the $ \upgamma \upgamma b\overline{b} $ final state. The data set used corresponds to an integrated luminosity of 36.1 fb$^{−1}$ of proton-proton collisions at a centre-of-mass energy of 13 TeV recorded by the ATLAS detector at the CERN Large Hadron Collider. No significant excess relative to the Standard Model expectation is observed. The observed limit on the non-resonant Higgs boson pair cross-section is 0.73 pb at 95% confidence level. This observed limit is equivalent to 22 times the predicted Standard Model cross-section. The Higgs boson self-coupling (κ$_{λ}$ = λ$_{HHH}$/λ$_{HHH}^{SM}$ ) is constrained at 95% confidence level to −8.2 < κ$_{λ}$ < 13.2. For resonant Higgs boson pair production through $ X\to HH\to \upgamma \upgamma b\overline{b} $ , the limit is presented, using the narrow-width approximation, as a function of m$_{X}$ in the range 260 GeV < m$_{X}$ < 1000 GeV. The observed limits range from 1.1 pb to 0.12 pb over this mass range.
202 citations
TL;DR: In this paper, the mass of the $W$ boson was measured based on proton-proton collision data recorded in 2011 at a centre-of-mass energy of 7 TeV with the ATLAS detector at the LHC.
Abstract: A measurement of the mass of the $W$ boson is presented based on proton-proton collision data recorded in 2011 at a centre-of-mass energy of 7 TeV with the ATLAS detector at the LHC, and corresponding to 4.6 fb$^{-1}$ of integrated luminosity. The selected data sample consists of $7.8 \times 10^6$ candidates in the $W\rightarrow \mu
u$ channel and $5.9 \times 10^6$ candidates in the $W\rightarrow e
u$ channel. The $W$-boson mass is obtained from template fits to the reconstructed distributions of the charged lepton transverse momentum and of the $W$ boson transverse mass in the electron and muon decay channels, yielding \begin{eqnarray} m_W &=& 80370 \pm 7 \, (\textrm{stat.}) \pm 11 \, (\textrm{exp. syst.}) \pm 14 \, (\textrm{mod. syst.}) \, \textrm{MeV} &=& 80370 \pm 19 \, \textrm{MeV}, \end{eqnarray} where the first uncertainty is statistical, the second corresponds to the experimental systematic uncertainty, and the third to the physics-modelling systematic uncertainty. A measurement of the mass difference between the $W^+$ and $W^-$ bosons yields $m_{W^+}-m_{W^-} = -29 \pm 28$ MeV.
195 citations
TL;DR: Combined 95% confidence-level upper limits are set on the production cross section for a range of vectorlike quark scenarios, significantly improving upon the reach of the individual searches.
Abstract: A combination of the searches for pair-produced vectorlike partners of the top and bottom quarks in various decay channels (T -> Zt/Wb/Ht, B -> Zb/Wt/Hb) is performed using 36.1 fb(-1) of pp ...
174 citations
TL;DR: In this paper, an upper bound of 0.0025% and 0.031% for the cross-section of the charged Higgs boson times the branching fraction in the range 4.2-4.5 pb was established for the mass range 90-160 GeV.
Abstract: Charged Higgs bosons produced either in top-quark decays or in association with a top-quark, subsequently decaying via H$^{±}$ → τ$^{±}$ν$_{τ}$, are searched for in 36.1 fb$^{−1}$ of proton-proton collision data at $ \sqrt{s}=13 $ TeV recorded with the ATLAS detector. Depending on whether the top-quark produced together with H$^{±}$ decays hadronically or leptonically, the search targets τ+jets and τ+lepton final states, in both cases with a hadronically decaying τ-lepton. No evidence of a charged Higgs boson is found. For the mass range of $ {m}_{H^{\pm }} $ = 90–2000 GeV, upper limits at the 95% confidence level are set on the production cross-section of the charged Higgs boson times the branching fraction $ \mathrm{\mathcal{B}}\left({H}^{\pm}\to {\tau}^{\pm }{
u}_{\tau}\right) $ in the range 4.2–0.0025 pb. In the mass range 90–160 GeV, assuming the Standard Model cross-section for $ t\overline{t} $ production, this corresponds to upper limits between 0.25% and 0.031% for the branching fraction $ \mathrm{\mathcal{B}}\left(t\to b{H}^{\pm}\right)\times \mathrm{\mathcal{B}}\left({H}^{\pm}\to {\tau}^{\pm }{
u}_{\tau}\right) $ .
154 citations
TL;DR: A search for supersymmetric partners of quarks and gluons in final states containing hadronic jets and missing transverse momentum, but no electrons or muons, is presented in this article.
Abstract: A search for the supersymmetric partners of quarks and gluons (squarks and gluinos) in final states containing hadronic jets and missing transverse momentum, but no electrons or muons, is presented ...
149 citations
TL;DR: In this paper, a search for heavy resonances decaying into a pair of bosons leading to the final states, where $$\ell $$¯¯ stands for either an electron or a muon, is presented.
Abstract: A search for heavy resonances decaying into a pair of $$Z$$
bosons leading to $$\ell ^+\ell ^-\ell ^+\ell ^-$$
and $$\ell ^+\ell ^-
u \bar{
u }$$
final states, where $$\ell $$
stands for either an electron or a muon, is presented. The search uses proton–proton collision data at a centre-of-mass energy of 13
$$\text {TeV}$$
corresponding to an integrated luminosity of 36.1
$$\hbox {fb}^{-1}$$
collected with the ATLAS detector during 2015 and 2016 at the Large Hadron Collider. Different mass ranges for the hypothetical resonances are considered, depending on the final state and model. The different ranges span between 200 and 2000
$$\text {GeV}$$
. The results are interpreted as upper limits on the production cross section of a spin-0 or spin-2 resonance. The upper limits for the spin-0 resonance are translated to exclusion contours in the context of Type-I and Type-II two-Higgs-doublet models, while those for the spin-2 resonance are used to constrain the Randall–Sundrum model with an extra dimension giving rise to spin-2 graviton excitations.
103 citations
TL;DR: In this article, a search for neutral heavy resonances was performed in the WW -> e nu mu nu decay channel using collision data corresponding to an integrated luminosity of 36.1 fb(-1).
Abstract: A search for neutral heavy resonances is performed in the WW -> e nu mu nu decay channel using pp collision data corresponding to an integrated luminosity of 36.1 fb(-1), collected at a centre-o ...
100 citations
TL;DR: Searches for new heavy resonances decaying into different pairings of W, Z, or Higgs bosons, as well as dirffiffiffiffiectly into leptons, are presented using a data sample corresponding to 36.1 fb(-1...
Abstract: Searches for new heavy resonances decaying into different pairings of W, Z, or Higgs bosons, as well as dirffiffiffiectly into leptons, are presented using a data sample corresponding to 36.1 fb(-1 ...
99 citations
TL;DR: In this paper, the authors search for heavy resonances decaying into ZZ or ZW using data from proton-proton collisions at a center-of-mass energy of root s - 13 TeV.
Abstract: This paper reports searches for heavy resonances decaying into ZZ or ZW using data from proton-proton collisions at a centre-of-mass energy of root s - 13 TeV. The data, corresponding to an integra ...
98 citations
TL;DR: A search for weakly interacting massive dark-matter particles produced in association with bottom or top quarks is presented and limits on the production cross-section of 300 times the predicted rate for mediators with masses between 10 and 50GeV are set.
Abstract: A search for weakly interacting massive dark matter particles produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and missing transverse ...
TL;DR: In this article, a search for charged Higgs bosons heavier than the top quark and decaying via H± → tb is presented, which corresponds to 36.1 fb−1 of pp collisions at s=13 TeV.
Abstract: A search for charged Higgs bosons heavier than the top quark and decaying via H± → tb is presented. The data analysed corresponds to 36.1 fb−1 of pp collisions at s=13 TeV and was recorded with the ATLAS detector at the LHC in 2015 and 2016. The production of a charged Higgs boson in association with a top quark and a bottom quark, pp → tbH±, is explored in the mass range from mH± = 200 to 2000 GeV using multi-jet final states with one or two electrons or muons. Events are categorised according to the multiplicity of jets and how likely these are to have originated from hadronisation of a bottom quark. Multivariate techniques are used to discriminate between signal and background events. No significant excess above the background-only hypothesis is observed and exclusion limits are derived for the production cross-section times branching ratio of a charged Higgs boson as a function of its mass, which range from 2.9 pb at mH± = 200 GeV to 0.070 pb at mH± = 2000 GeV. The results are interpreted in two benchmark scenarios of the Minimal Supersymmetric Standard Model.[Figure not available: see fulltext.].
TL;DR: In this article, differential cross-sections of highly boosted pair-produced top quarks as a function of top-quark and t (t) over bar system kinematic observables using proton-proton collis...
Abstract: Measurements are made of differential cross-sections of highly boosted pair-produced top quarks as a function of top-quark and t (t) over bar system kinematic observables using proton-proton collis ...
TL;DR: In this paper, measurements of ZZ production in the l(+)l(-)l'l'(+) l'(-) channel in proton-proton collisions at 13 TeV center-of-mass energy at the Large Hadron Collider are presented.
Abstract: Measurements of ZZ production in the l(+)l(-)l'(+)l'(-) channel in proton-proton collisions at 13 TeV center-of-mass energy at the Large Hadron Collider are presented. The data correspond to 36.1 f ...
TL;DR: In this article, a combination method was proposed to account for the correlations of the statistical and systematic uncertainties among the different datasets, and a next-to-leading order QCD analysis was performed using these data together with the combined inclusive deep inelastic scattering cross sections from HERA.
Abstract: Measurements of open charm and beauty production cross sections in deep inelastic ep scattering at HERA from the H1 and ZEUS Collaborations are combined. Reduced cross sections are obtained in the kinematic range of negative four-momentum transfer squared of the photon $2.5~\hbox {GeV}^2\le Q^2 \le 2000\, \hbox {GeV}^2$ and Bjorken scaling variable $3 \cdot 10^{-5} \le x_\mathrm{Bj} \le 5 \cdot 10^{-2}$ . The combination method accounts for the correlations of the statistical and systematic uncertainties among the different datasets. Perturbative QCD calculations are compared to the combined data. A next-to-leading order QCD analysis is performed using these data together with the combined inclusive deep inelastic scattering cross sections from HERA. The running charm- and beauty-quark masses are determined as $m_c(m_c) = 1.290^{+0.046-0.041} \mathrm{(exp/fit)}$ ${}^{+0.062-0.014} \mathrm{(model)}$ ${}^{+0.003-0.031} \mathrm{(parameterisation)}$ GeV and $m_b(m_b) = 4.049^{+0.104-0.109} \mathrm{(exp/fit)}$ ${}^{+0.090-0.032} \mathrm{(model)}$ ${}^{+0.001-0.031} \mathrm{(parameterisation)}~\mathrm{GeV}$ .
TL;DR: A search for massive coloured resonances which are pair-produced and decay into two jets is presented, interpreted in a SUSY simplified model where the lightest supersymmetric particle is the top squark, which decays promptly into two quarks through R-parity-violating couplings.
Abstract: A search for massive coloured resonances which are pair-produced and decay into two jets is presented. The analysis uses 36.7 fb(-1) of root s = 13 TeV pp collision data recorded by the ATLAS exper ...
TL;DR: It is found that the correlation between the harmonic flow coefficients of charged particles in the pseudorapidity range measured in two separated η intervals does not factorise into the product of single-particle coefficients, and this breaking of factorisation, or flow decorrelation, increases linearly with the \eta $$η separation between the intervals.
Abstract: Measurements of longitudinal flow correlations are presented for charged particles in the pseudorapidity range vertical bar eta vertical bar < 2.4 using 7 mu b(-1) and 470 mu b(-1) of Pb+Pb coll ...
TL;DR: A search for new heavy W bosons decaying to an electron or muon and a neutrino using proton–proton collision data at a centre-of-mass energy of 13 TeV finds no excess of events above the Standard Model prediction.
Abstract: The results of a search for new heavy $$W^\prime $$
bosons decaying to an electron or muon and a neutrino using proton–proton collision data at a centre-of-mass energy of $$\sqrt{s}~=~13$$
TeV are presented. The dataset was collected in 2015 and 2016 by the ATLAS experiment at the Large Hadron Collider and corresponds to an integrated luminosity of 36.1
$$\text{ fb }^{-1}$$
. As no excess of events above the Standard Model prediction is observed, the results are used to set upper limits on the $$W^\prime $$
boson cross-section times branching ratio to an electron or muon and a neutrino as a function of the $$W^\prime $$
mass. Assuming a $$W^\prime $$
boson with the same couplings as the Standard Model W boson, $$W^\prime $$
masses below 5.1 TeV are excluded at the 95% confidence level.
TL;DR: In this paper, a search for the b (b) over bar decay of the Standard Model Higgs boson produced through vector-boson fusion is presented, and three mutually exclusive channels are considered: two all-hadronic channels and two allhadronic channel.
Abstract: A search for the b (b) over bar decay of the Standard Model Higgs boson produced through vector-boson fusion is presented Three mutually exclusive channels are considered: two all-hadronic channel
TL;DR: This Letter presents a measurement of γγ→μ+}μ^{-} production in Pb+Pb collisions recorded by the ATLAS detector at the Large Hadron Collider at sqrt[s_{NN}]=5.02 TeV with an integrated luminosity of 0.49nb^{-1}.
Abstract: This Letter presents a measurement of γγ→μ^{+}μ^{-} production in Pb+Pb collisions recorded by the ATLAS detector at the Large Hadron Collider at sqrt[s_{NN}]=5.02 TeV with an integrated luminosity of 0.49 nb^{-1}. The azimuthal angle and transverse momentum correlations between the muons are measured as a function of collision centrality. The muon pairs are produced from γγ through the interaction of the large electromagnetic fields of the nuclei. The contribution from background sources of muon pairs is removed using a template fit method. In peripheral collisions, the muons exhibit a strong back-to-back correlation consistent with previous measurements of muon pair production in ultraperipheral collisions. The angular correlations are observed to broaden significantly in central collisions. The modifications are qualitatively consistent with rescattering of the muons while passing through the hot matter produced in the collision.
TL;DR: In this paper, a search for new phenomena in events with two same-charge leptons or three lepton and jets identified as originating from b-quarks in a data sample of 361 fb−1 of pp collisions at s√=13 TeV recorded by the ATLAS detector at the Large Hadron Collider is reported.
Abstract: A search for new phenomena in events with two same-charge leptons or three leptons and jets identified as originating from b-quarks in a data sample of 361 fb−1 of pp collisions at s√=13 TeV recorded by the ATLAS detector at the Large Hadron Collider is reported No significant excess is found and limits are set on vector-like quark, four-top-quark, and same-sign top-quark pair production The observed (expected) 95% CL mass limits for a vector-like T- and B-quark singlet are mT > 098 (099) TeV and mB > 100 (101) TeV respectively Limits on the production of the vector-like T5/3-quark are also derived considering both pair and single production; in the former case the lower limit on the mass of the T5/3-quark is (expected to be) 119 (121) TeV The Standard Model four-top-quark production cross-section upper limit is (expected to be) 69 (29) fb Constraints are also set on exotic four-top-quark production models Finally, limits are set on same-sign top-quark pair production The upper limit on uu → tt production is (expected to be) 89 (59) fb for a mediator mass of 1 TeV, and a dark-matter interpretation is also derived, excluding a mediator of 3 TeV with a dark-sector coupling of 10 and a coupling to ordinary matter above 031
TL;DR: In this paper, results from a search for supersymmetry in events with four or more charged leptons (electrons, muons, and taus) are presented using a data sample corresponding to 36.1 fb-1 of proton-proton collisions delivered by the Large Hadron Collider at s=13 TeV and recorded by the ATLAS detector.
Abstract: Results from a search for supersymmetry in events with four or more charged leptons (electrons, muons and taus) are presented. The analysis uses a data sample corresponding to 36.1 fb-1 of proton-proton collisions delivered by the Large Hadron Collider at s=13 TeV and recorded by the ATLAS detector. Four-lepton signal regions with up to two hadronically decaying taus are designed to target a range of supersymmetric scenarios that can be either enriched in or depleted of events involving the production and decay of a Z boson. Data yields are consistent with Standard Model expectations and results are used to set upper limits on the event yields from processes beyond the Standard Model. Exclusion limits are set at the 95% confidence level in simplified models of general gauge mediated supersymmetry, where Higgsino masses are excluded up to 295 GeV. In R-parity-violating simplified models with decays of the lightest supersymmetric particle to charged leptons, lower limits of 1.46, 1.06, and 2.25 TeV are placed on wino, slepton and gluino masses, respectively. © 2018 CERN.
TL;DR: A search for a narrow-width resonance X decaying to a pair of Standard Model Higgs bosons HH is performed with the same set of data, and the observed upper limits onσ(pp→X)×B(X→HH) range between 40.0 and 6.1 pb for masses of the resonance between 260 and 500 GeV, while the expected limits range between 17.6 and 4.4 pb.
Abstract: Searches for non-resonant and resonant Higgs boson pair production are performed in the $\gamma \gamma WW^*$ channel with the final state of $\gamma \gamma \ell
u jj$ using 36.1 $\hbox {fb}^{-1}$ of proton–proton collision data recorded at a centre-of-mass energy of $\sqrt{s}=$ 13 TeV by the ATLAS detector at the Large Hadron Collider. No significant deviation from the Standard Model prediction is observed. A 95% confidence-level observed upper limit of 7.7 pb is set on the cross section for non-resonant production, while the expected limit is 5.4 pb. A search for a narrow-width resonance X decaying to a pair of Standard Model Higgs bosons HH is performed with the same set of data, and the observed upper limits on $\sigma (pp\rightarrow X)\times B(X\rightarrow HH)$ range between 40.0 and 6.1 pb for masses of the resonance between 260 and 500 GeV, while the expected limits range between 17.6 and 4.4 pb. When deriving the limits above, the Standard Model branching ratios of the $H{\rightarrow }{\gamma \gamma }$ and $H{\rightarrow }WW^*$ are assumed.
TL;DR: In this article, a combined measurement of differential and inclusive total cross sections of Higgs boson production is performed using 36.1 fb −1 of 13 TeV proton-proton collision data produced by the LHC and recorded by the ATLAS detector in 2015 and 2016.
TL;DR: In this paper, it has been shown that Figure 30 shows the 68% and 99% confidence-level contours for the W boson and top quark mass measurements, instead of the 66% and 95% confidence level contours, as stated in the legend.
Abstract: It has been found that Figure 30 shows the 68% and 99% confidence-level contours for the W boson and top quark mass measurements, instead of the 68% and 95% confidence-level contours, as stated in the legend.
TL;DR: In this article, the Fourier coefficients of flow harmonics were measured using the two-particle correlation, scalar product and event plane methods, which were compared and discussed in the context of previous and recent measurements in Pb+Pb collisions at the LHC.
Abstract: Measurements of the azimuthal anisotropy in lead–lead collisions at $\sqrt{s_{_\text {NN}}}$ = 502 TeV are presented using a data sample corresponding to 049 ${\mathrm {nb}}^{-1}$ integrated luminosity collected by the ATLAS experiment at the LHC in 2015 The recorded minimum-bias sample is enhanced by triggers for “ultra-central” collisions, providing an opportunity to perform detailed study of flow harmonics in the regime where the initial state is dominated by fluctuations The anisotropy of the charged-particle azimuthal angle distributions is characterized by the Fourier coefficients, $v_{2}$ – $v_{7}$ , which are measured using the two-particle correlation, scalar-product and event-plane methods The goal of the paper is to provide measurements of the differential as well as integrated flow harmonics $v_{n}$ over wide ranges of the transverse momentum, 05 $
TL;DR: Results are interpreted using simplified models, and exclude gluinos and squarks with masses as large as 1.85 and 1.3 $$\text {Te}\text {V}$$Te at 95% confidence level, respectively.
Abstract: A search for new phenomena in final states containing an e(+)e(-) or m(+)m(-) pair, jets, and large missing transverse momentum is presented. This analysis makes use of proton-proton collision data ...
TL;DR: An overview of the Tile Calorimeter’s performance during the years 2008–2012 using cosmic-ray muon events and proton–proton collision data at centre-of-mass energies of 7 and 8 TeV with a total integrated luminosity of nearly 30 fb$$^{-1}$$-1.
Abstract: The Tile Calorimeter is the hadron calorimeter covering the central region of the ATLAS experiment at the Large Hadron Collider. Approximately 10,000 photomultipliers collect light from scintillating tiles acting as the active material sandwiched between slabs of steel absorber. This paper gives an overview of the calorimeter’s performance during the years 2008–2012 using cosmic-ray muon events and proton–proton collision data at centre-of-mass energies of 7 and 8 TeV with a total integrated luminosity of nearly 30 fb$^{-1}$ . The signal reconstruction methods, calibration systems as well as the detector operation status are presented. The energy and time calibration methods performed excellently, resulting in good stability of the calorimeter response under varying conditions during the LHC Run 1. Finally, the Tile Calorimeter response to isolated muons and hadrons as well as to jets from proton–proton collisions is presented. The results demonstrate excellent performance in accord with specifications mentioned in the Technical Design Report.
TL;DR: In this article, a search for the production of new heavy resonances decaying into a Higgs boson and a photon using proton-proton collision data at the LHC is presented.
Abstract: This Letter presents a search for the production of new heavy resonances decaying into a Higgs boson and a photon using proton-proton collision data at
√
s
=
13
TeV
collected by the ATLAS detector at the LHC. The data correspond to an integrated luminosity of
139
fb
−
1
. The analysis is performed by reconstructing hadronically decaying Higgs boson
(
H
→
b
¯
b
)
candidates as single large-radius jets. A novel algorithm using information about the jet constituents in the center-of-mass frame of the jet is implemented to identify the two
b
quarks in the single jet. No significant excess of events is observed above the expected background. Upper limits are set on the production cross-section times branching fraction for narrow spin-1 resonances decaying into a Higgs boson and a photon in the resonance mass range from 0.7 to 4 TeV, cross-section times branching fractions are excluded between 11.6 fb and 0.11 fb at a 95% confidence level.
TL;DR: A search for high-mass resonances decaying to τν using proton-proton collisions at sqrt[s]=13 TeV produced by the Large Hadron Collider is presented and model-independent upper limits are set on the visible τν production cross section.
Abstract: A search for high-mass resonances decaying to τν using proton-proton collisions at sqrt[s]=13 TeV produced by the Large Hadron Collider is presented. Only τ-lepton decays with hadrons in the final state are considered. The data were recorded with the ATLAS detector and correspond to an integrated luminosity of 36.1 fb^{-1}. No statistically significant excess above the standard model expectation is observed; model-independent upper limits are set on the visible τν production cross section. Heavy W^{'} bosons with masses less than 3.7 TeV in the sequential standard model and masses less than 2.2-3.8 TeV depending on the coupling in the nonuniversal G(221) model are excluded at the 95% credibility level.