Search for single production of a vector-like $T$ quark decaying into a Higgs boson and top quark with fully hadronic final states using the ATLAS detector

The ATLAS collaboration Aad, Georges ; Abbott, Braden Keim ; Abbott, Dale ; et al.
Phys.Rev.D 105 (2022) 092012, 2022.
Inspire Record 2013051 DOI 10.17182/hepdata.131522

A search is made for a vector-like $T$ quark decaying into a Higgs boson and a top quark in 13 TeV proton-proton collisions using the ATLAS detector at the Large Hadron Collider with a data sample corresponding to an integrated luminosity of 139 fb$^{-1}$. The Higgs-boson and top-quark candidates are identified in the all-hadronic decay mode, where $H\to b\bar{b}$ and $t\to b W \to b q \bar{q}^\prime$ are reconstructed as large-radius jets. The candidate Higgs boson, top quark, and associated B-hadrons are identified using tagging algorithms. No significant excess is observed above the background, so limits are set on the production cross-section of a singlet $T$ quark at 95% confidence level, depending on the mass, $m_T$, and coupling, $\kappa_T$, of the vector-like $T$ quark to Standard Model particles. In the considered mass range between 1.0 and 2.3 TeV, the upper limit on the allowed coupling values increases with $m_T$ from a minimum value of 0.35 for 1.07 < $m_T$ < 1.4 TeV to 1.6 for $m_T$ = 2.3 TeV.

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Dijet invariant mass distribution for the $SR$ showing the results of the model when fitted to the data. A $T$-quark hypothesis with $m_{T} = 1.6$ TeV and $\kappa_{T} = 0.5$ is used in the fit.

Dijet invariant mass distribution for the $ttNR$ showing the results of the model when fitted to the data. A $T$-quark hypothesis with $m_{T} = 1.6$ TeV and $\kappa_{T} = 0.5$ is used in the fit.

Observed and expected 95% CL upper limits on the single $T$-quark coupling $\kappa_{T}$ as a function of $m_{T}$ are shown.

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Studies of new Higgs boson interactions through nonresonant $HH$ production in the $b\bar{b}\gamma\gamma$ final state in $pp$ collisions at $\sqrt{s}=13$ TeV with the ATLAS detector

The ATLAS collaboration Aad, Georges ; Abbott, Braden Keim ; Abeling, Kira ; et al.
JHEP 01 (2024) 066, 2024.
Inspire Record 2712676 DOI 10.17182/hepdata.144918

A search for nonresonant Higgs boson pair production in the $b\bar{b}\gamma\gamma$ final state is performed using 140 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. This analysis supersedes and expands upon the previous nonresonant ATLAS results in this final state based on the same data sample. The analysis strategy is optimised to probe anomalous values not only of the Higgs ($H$) boson self-coupling modifier $\kappa_\lambda$ but also of the quartic $HHVV$ ($V=W,Z$) coupling modifier $\kappa_{2V}$. No significant excess above the expected background from Standard Model processes is observed. An observed upper limit $\mu_{HH}<4.0$ is set at 95% confidence level on the Higgs boson pair production cross-section normalised to its Standard Model prediction. The 95% confidence intervals for the coupling modifiers are $-1.4<\kappa_\lambda<6.9$ and $-0.5<\kappa_{2V}<2.7$, assuming all other Higgs boson couplings except the one under study are fixed to the Standard Model predictions. The results are interpreted in the Standard Model effective field theory and Higgs effective field theory frameworks in terms of constraints on the couplings of anomalous Higgs boson (self-)interactions.

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Observed (solid line) value of $-2\ln\Lambda$ as a function of $\kappa_{\lambda}$, when all other coupling modifiers are fixed to their SM predictions.

Expected (dashed line) value of $-2\ln\Lambda$ as a function of $\kappa_{\lambda}$, when all other coupling modifiers are fixed to their SM predictions.

Observed (solid line) value of $-2\ln\Lambda$ as a function of $\kappa_{2V}$, when all other coupling modifiers are fixed to their SM predictions.

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Search for new phenomena in $pp$ collisions in final states with tau leptons, $b$-jets, and missing transverse momentum with the ATLAS detector

The ATLAS collaboration Aad, Georges ; Abbott, Braden Keim ; Abbott, Dale ; et al.
Phys.Rev.D 104 (2021) 112005, 2021.
Inspire Record 1907601 DOI 10.17182/hepdata.105998

A search for new phenomena in final states with hadronically decaying tau leptons, $b$-jets, and missing transverse momentum is presented. The analyzed dataset comprises $pp$~collision data at a center-of-mass energy of $\sqrt s = 13$ TeV with an integrated luminosity of 139/fb, delivered by the Large Hadron Collider and recorded with the ATLAS detector from 2015 to 2018. The observed data are compatible with the expected Standard Model background. The results are interpreted in simplified models for two different scenarios. The first model is based on supersymmetry and considers pair production of top squarks, each of which decays into a $b$-quark, a neutrino and a tau slepton. Each tau slepton in turn decays into a tau lepton and a nearly massless gravitino. Within this model, top-squark masses up to 1.4 TeV can be excluded at the 95% confidence level over a wide range of tau-slepton masses. The second model considers pair production of leptoquarks with decays into third-generation leptons and quarks. Depending on the branching fraction into charged leptons, leptoquarks with masses up to around 1.25 TeV can be excluded at the 95% confidence level for the case of scalar leptoquarks and up to 1.8 TeV (1.5 TeV) for vector leptoquarks in a Yang--Mills (minimal-coupling) scenario. In addition, model-independent upper limits are set on the cross section of processes beyond the Standard Model.

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Relative systematic uncertainties in the estimated number of background events in the signal regions. In the lower part of the table, a breakdown of the total uncertainty into different categories is given. For the multi-bin SR, the breakdown refers to the integral over all three $p_{\text{T}}(\tau)$ bins. As the individual uncertainties are correlated, they do not add in quadrature to equal the total background uncertainty.

Distributions of $m_{\text{T}2}(\tau_{1},\tau_{2})$ in the di-tau SR. The stacked histograms show the various SM background contributions. The hatched band indicates the total statistical and systematic uncertainty of the SM background. The $t\bar{t}$ (2 real $\tau$) and $t\bar{t}$ (1 real $\tau$) as well as the single-top background contributions are scaled with the normalization factors obtained from the background-only fit. Minor backgrounds are grouped together and denoted as 'Other'. This includes $t\bar{t}$-fake, single top, and other top (di-tau channel) or $t\bar{t}$-fake, $t\bar{t}+H$, multiboson, and other top (single-tau channel). The overlaid dotted lines show the additional contributions for signal scenarios close to the expected exclusion contour with the particle type and the mass and $\beta$ parameters for the simplified models indicated in the legend. For the leptoquark signal model the shapes of the distributions for $\text{LQ}_{3}^{\text{d}}$ and $\text{LQ}_{3}^{\text{v}}$ (not shown) are similar to that of $\text{LQ}_{3}^{\text{u}}$. The rightmost bin includes the overflow.

Distributions of $E_{\text{T}}^{\text{miss}}$ in the di-tau SR. The stacked histograms show the various SM background contributions. The hatched band indicates the total statistical and systematic uncertainty of the SM background. The $t\bar{t}$ (2 real $\tau$) and $t\bar{t}$ (1 real $\tau$) as well as the single-top background contributions are scaled with the normalization factors obtained from the background-only fit. Minor backgrounds are grouped together and denoted as 'Other'. This includes $t\bar{t}$-fake, single top, and other top (di-tau channel) or $t\bar{t}$-fake, $t\bar{t}+H$, multiboson, and other top (single-tau channel). The overlaid dotted lines show the additional contributions for signal scenarios close to the expected exclusion contour with the particle type and the mass and $\beta$ parameters for the simplified models indicated in the legend. For the leptoquark signal model the shapes of the distributions for $\text{LQ}_{3}^{\text{d}}$ and $\text{LQ}_{3}^{\text{v}}$ (not shown) are similar to that of $\text{LQ}_{3}^{\text{u}}$. The rightmost bin includes the overflow.

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Search for flavour-changing neutral current interactions of the top quark and the Higgs boson in events with a pair of $\tau$-leptons in pp collisions at $\sqrt{s}=13$ TeV with the ATLAS detector

The ATLAS collaboration Aad, Georges ; Abbott, Braden Keim ; Abbott, D.C. ; et al.
JHEP 2306 (2023) 155, 2023.
Inspire Record 2141572 DOI 10.17182/hepdata.130958

A search for flavour-changing neutral current (FCNC) $tqH$ interactions involving a top quark, another up-type quark ($q=u$, $c$), and a Standard Model (SM) Higgs boson decaying into a $\tau$-lepton pair ($H\rightarrow \tau^+\tau^-$) is presented. The search is based on a dataset of $pp$ collisions at $\sqrt{s}=13$ TeV that corresponds to an integrated luminosity of 139 fb$^{-1}$ recorded with the ATLAS detector at the Large Hadron Collider. Two processes are considered: single top quark FCNC production in association with a Higgs boson ($pp\rightarrow tH$), and top quark pair production in which one of the top quarks decays into $Wb$ and the other decays into $qH$ through the FCNC interactions. The search selects events with two hadronically decaying $\tau$-lepton candidates ($\tau_{\text{had}}$) or at least one $\tau_{\text{had}}$ with an additional lepton ($e$, $\mu$), as well as multiple jets. Event kinematics is used to separate signal from the background through a multivariate discriminant. A slight excess of data is observed with a significance of 2.3$\sigma$ above the expected SM background, and 95% CL upper limits on the $t\to qH$ branching ratios are derived. The observed (expected) 95% CL upper limits set on the $t\to cH$ and $t\to uH$ branching ratios are $9.4 \times 10^{-4}$ $(4.8^{+2.2}_{-1.4}\times 10^{-4})$ and $6.9\times 10^{-4}$ $(3.5^{+1.5}_{-1.0}\times 10^{-4})$, respectively. The corresponding combined observed (expected) upper limits on the dimension-6 operator Wilson coefficients in the effective $tqH$ couplings are $C_{c\phi} <1.35$ $(0.97)$ and $C_{u\phi} <1.16$ $(0.82)$.

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Leading tau Pt distributions obtained before the fit to data (Pre-Fit) showing the expected background and tuH signals after applying fake factors in the $t_{\ell}\tau_{had}\tau_{had}$ region. Other MC includes single top, V+jets, and other small backgrounds. The tuH signals with nominal branching ratio of 0.1% are scaled using normalization factors of 2 to 50. Statistical and systematic uncertainties are included in the "Total background".

Leading tau Pt distributions obtained before the fit to data (Pre-Fit) showing the expected background and tuH signals after applying fake factors in the $t_{\ell}\tau_{had}$-1j region. Other MC includes single top, V+jets, and other small backgrounds. The tuH signals with nominal branching ratio of 0.1% are scaled using normalization factors of 2 to 50. Statistical and systematic uncertainties are included in the "Total background".

Leading tau Pt distributions obtained before the fit to data (Pre-Fit) showing the expected background and tuH signals after applying fake factors in the $t_{\ell}\tau_{had}$-2j region. Other MC includes single top, V+jets, and other small backgrounds. The tuH signals with nominal branching ratio of 0.1% are scaled using normalization factors of 2 to 50. Statistical and systematic uncertainties are included in the "Total background".

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Study of $B_c^+\to J/\psi D_s^+$ and $B_c^+\to J/\psi D_s^{*+}$ decays in $pp$ collisions at $\sqrt{s} = 13$ TeV with the ATLAS detector

The ATLAS collaboration Aad, Georges ; Abbott, Braden Keim ; Abbott, Dale ; et al.
JHEP 08 (2022) 087, 2022.
Inspire Record 2044968 DOI 10.17182/hepdata.126990

A study of $B_c^+\to J/\psi D_s^+$ and $B_c^+\to J/\psi D_s^{*+}$ decays using 139 fb$^{-1}$ of integrated luminosity collected with the ATLAS detector from $\sqrt{s} = 13$ TeV $pp$ collisions at the LHC is presented. The ratios of the branching fractions of the two decays to the branching fraction of the $B_c^+\to J/\psi \pi^+$ decay are measured: $\mathcal B(B_c^+\to J/\psi D_s^+)/\mathcal B(B_c^+\to J/\psi \pi^+) = 2.76\pm 0.47$ and $\mathcal B(B_c^+\to J/\psi D_s^{*+})/\mathcal B(B_c^+\to J/\psi \pi^+) = 5.33\pm 0.96$. The ratio of the branching fractions of the two decays is found to be $\mathcal B(B_c^+\to J/\psi D_s^{*+})/\mathcal B(B_c^+\to J/\psi D_s^+) = 1.93\pm0.26$. For the $B_c^+\to J/\psi D_s^{*+}$ decay, the transverse polarization fraction, $\Gamma_{\pm\pm}/\Gamma$, is measured to be $0.70\pm0.11$. The reported uncertainties include both the statistical and systematic components added in quadrature. The precision of the measurements exceeds that in all previous studies of these decays. These results supersede those obtained in the earlier ATLAS study of the same decays with $\sqrt{s} = 7$ and 8 TeV $pp$ collision data. A comparison with available theoretical predictions for the measured quantities is presented.

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Measured values of $R_{D_s^+/\pi^+}$, $R_{D_s^{*+}/\pi^+}$, $R_{D_s^{*+}/D_s^+}$ ratios of branching fractions, fraction of transverse polarization $\Gamma_{\pm\pm}/\Gamma$ with their statistical uncertainties and full breakdown of systematic uncertainties. Predictions of various theory calculations are also shown with their uncertainties where available, as well as the estimates based on similar decays of light $B$ mesons.

Parameters of the $B_c^+\to J/\psi D_s^+$ and $B_c^+\to J/\psi D_s^{*+}$ signals obtained with the unbinned extended maximum-likelihood fit to the data. Only the statistical uncertainties are included. No acceptance or efficiency corrections are applied to the signal yields.

Parameters of the $B_c^+\to J/\psi \pi^+$ signal obtained with the unbinned extended maximum-likelihood fit. Only the statistical uncertainties are included. No efficiency correction is applied to the signal yield.

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Combination of inclusive top-quark pair production cross-section measurements using ATLAS and CMS data at $\sqrt{s}= 7$ and 8 TeV

The ATLAS & CMS collaborations Aad, G. ; Abbott, B. ; Abbott, D.C. ; et al.
JHEP 07 (2023) 213, 2023.
Inspire Record 2088291 DOI 10.17182/hepdata.110250

A combination of measurements of the inclusive top-quark pair production cross-section performed by ATLAS and CMS in proton-proton collisions at centre-of-mass energies of 7 and 8 TeV at the LHC is presented. The cross-sections are obtained using top-quark pair decays with an opposite-charge electron-muon pair in the final state and with data corresponding to an integrated luminosity of about 5 fb$^{-1}$ at $\sqrt{s}=7$ TeV and about 20 fb$^{-1}$ at $\sqrt{s}=8$ TeV for each experiment. The combined cross-sections are determined to be $178.5 \pm 4.7$ pb at $\sqrt{s}=7$ TeV and $243.3^{+6.0}_{-5.9}$ pb at $\sqrt{s}=8$ TeV with a correlation of 0.41, using a reference top-quark mass value of 172.5 GeV. The ratio of the combined cross-sections is determined to be $R_{8/7}= 1.363\pm 0.032$. The combined measured cross-sections and their ratio agree well with theory calculations using several parton distribution function (PDF) sets. The values of the top-quark pole mass (with the strong coupling fixed at 0.118) and the strong coupling (with the top-quark pole mass fixed at 172.5 GeV) are extracted from the combined results by fitting a next-to-next-to-leading-order plus next-to-next-to-leading-log QCD prediction to the measurements. Using a version of the NNPDF3.1 PDF set containing no top-quark measurements, the results obtained are $m_t^\text{pole} = 173.4^{+1.8}_{-2.0}$ GeV and $\alpha_\text{s}(m_Z)= 0.1170^{+ 0.0021}_{-0.0018}$.

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Full covariance matrix including all systematic uncertainties expressed as nuisance parameters. With the exception of the cross section parameters, all parameters were normalised to 1 before the fit. Therefore, the diagonal elements represent the constraint in quadrature.

Full covariance matrix including all systematic uncertainties expressed as nuisance parameters. With the exception of the cross section parameters, all parameters were normalised to 1 before the fit. Therefore, the diagonal elements represent the constraint in quadrature.


Measurement of inclusive jet and dijet cross sections in proton-proton collisions at 7 TeV centre-of-mass energy with the ATLAS detector

The ATLAS collaboration Aad, G. ; Abbott, B. ; Abdallah, J. ; et al.
Eur.Phys.J.C 71 (2011) 1512, 2011.
Inspire Record 871366 DOI 10.17182/hepdata.56004

Jet cross sections have been measured for the first time in proton-proton collisions at a centre-of-mass energy of 7 TeV using the ATLAS detector. The measurement uses an integrated luminosity of 17 nb-1 recorded at the Large Hadron Collider. The anti-kt algorithm is used to identify jets, with two jet resolution parameters, R = 0.4 and 0.6. The dominant uncertainty comes from the jet energy scale, which is determined to within 7% for central jets above 60 GeV transverse momentum. Inclusive single-jet differential cross sections are presented as functions of jet transverse momentum and rapidity. Dijet cross sections are presented as functions of dijet mass and the angular variable $\chi$. The results are compared to expectations based on next-to-leading-order QCD, which agree with the data, providing a validation of the theory in a new kinematic regime.

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Inclusive jet double-differential cross sections in the |rapidity| range 0 to 0.3, using a jet resolution R value of 0.4. The three (sys) errors are respectively, the Absolute JES, the Unfolding and the Luminosity uncertainties.

Inclusive jet double-differential cross sections in the |rapidity| range 0.3 to 0.8, using a jet resolution R value of 0.4. The three (sys) errors are respectively, the Absolute JES, the Unfolding and the Luminosity uncertainties.

Inclusive jet double-differential cross sections in the |rapidity| range 0.8 to 1.2, using a jet resolution R value of 0.4. The three (sys) errors are respectively, the Absolute JES, the Unfolding and the Luminosity uncertainties.

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Search for a new heavy scalar particle decaying into a Higgs boson and a new scalar singlet in final states with one or two light leptons and a pair of $\tau$-leptons with the ATLAS detector

The ATLAS collaboration Aad, Georges ; Abbott, Braden Keim ; Abeling, Kira ; et al.
JHEP 10 (2023) 009, 2023.
Inspire Record 2679289 DOI 10.17182/hepdata.141076

A search for a new heavy scalar particle $X$ decaying into a Standard Model (SM) Higgs boson and a new singlet scalar particle $S$ is presented. The search uses a proton-proton ($pp$) collision data sample with an integrated luminosity of 140 fb$^{-1}$ recorded at a centre-of-mass energy of $\sqrt{s} = 13$ TeV with the ATLAS detector at the Large Hadron Collider. The most sensitive mass parameter space is explored in $X$ mass ranging from 500 to 1500 GeV, with the corresponding $S$ mass in the range 200-500 GeV. The search selects events with two hadronically decaying $\tau$-lepton candidates from $H\to \tau^+\tau^-$ decays and one or two light leptons ($\ell=e,\,\mu$) from $S\to VV$ ($V = W,\,Z$) decays while the remaining $V$ boson decays hadronically or to neutrinos. A multivariate discriminant based on event kinematics is used to separate the signal from the background. No excess is observed beyond the expected SM background and 95% confidence level upper limits between 72 fb and 542 fb are derived on the cross-section $\sigma(pp\to X\to SH)$ assuming the same SM-Higgs boson-like decay branching ratios for the $S\to VV$ decay. Upper limits on the visible cross-sections $\sigma(pp\to X\to SH \to WW\tau\tau)$ and $\sigma(pp\to X\to SH \to ZZ\tau\tau)$ are also set in the ranges 3-26 fb and 6-33 fb, respectively.

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Observed and expected 95% CL upper limits are shown for $\sigma(pp\to X\to SH)$ obtained from $WW1\ell2\tau_{\mathrm{had}}$, $WW2\ell2\tau_{\mathrm{had}}$, $ZZ2\ell2\tau_{\mathrm{had}}$, and their combination, as a function of combined $m_{S}$ and $m_{X}$ masses ($m_{S}$+$m_{X}/25$) in GeV.

Observed and expected 95% CL upper limits are shown for $\sigma(pp\to X\to SH\to WW\tau\tau)$ obtained from the combination of $WW1\ell2\tau_{\mathrm{had}}$ and $WW2\ell2\tau_{\mathrm{had}}$ channels, as a function of combined $m_{S}$ and $m_{X}$ masses ($m_{S}$+$m_{X}/25$) in GeV. The NMSSM scans of the allowed cross-sections for $\sigma(pp\to X\to SH\to WW\tau\tau)$ are also compared.

Observed and expected 95% CL upper limits are shown for $\sigma(pp\to X\to SH\to ZZ\tau\tau)$ obtained from $ZZ2\ell2\tau_{\mathrm{had}}$ channel, as a function of combined $m_{S}$ and $m_{X}$ masses ($m_{S}$+$m_{X}/25$) in GeV. The NMSSM scans of the allowed cross-sections for $\sigma(pp\to X\to SH\to ZZ\tau\tau)$ are also compared.

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Charged-particle multiplicities in pp interactions measured with the ATLAS detector at the LHC

The ATLAS collaboration Aad, G. ; Abbott, B. ; Abdallah, J. ; et al.
New J.Phys. 13 (2011) 053033, 2011.
Inspire Record 882098 DOI 10.17182/hepdata.57077

Measurements are presented from proton-proton collisions at centre-of-mass energies of sqrt(s) = 0.9, 2.36 and 7 TeV recorded with the ATLAS detector at the LHC. Events were collected using a single-arm minimum-bias trigger. The charged-particle multiplicity, its dependence on transverse momentum and pseudorapidity and the relationship between the mean transverse momentum and charged-particle multiplicity are measured. Measurements in different regions of phase-space are shown, providing diffraction-reduced measurements as well as more inclusive ones. The observed distributions are corrected to well-defined phase-space regions, using model-independent corrections. The results are compared to each other and to various Monte Carlo models, including a new AMBT1 PYTHIA 6 tune. In all the kinematic regions considered, the particle multiplicities are higher than predicted by the Monte Carlo models. The central charged-particle multiplicity per event and unit of pseudorapidity, for tracks with pT >100 MeV, is measured to be 3.483 +- 0.009 (stat) +- 0.106 (syst) at sqrt(s) = 0.9 TeV and 5.630 +- 0.003 (stat) +- 0.169 (syst) at sqrt(s) = 7 TeV.

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The average charged-particle muliplicity per unit of rapidity for ETARAP=0 as a function of the centre-of-mass energy.

The average charged-particle muliplicity per unit of rapidity in the pseudorapidity region -2.5 to 2.5 for events with 2 or more charged particles as a function of the centre-of-mass energy.


Charged-particle multiplicities in pp interactions at sqrt(s) = 900 GeV measured with the ATLAS detector at the LHC

The ATLAS collaboration Aad, G. ; Abat, E. ; Abbott, B. ; et al.
Phys.Lett.B 688 (2010) 21-42, 2010.
Inspire Record 849050 DOI 10.17182/hepdata.54850

The first measurements from proton-proton collisions recorded with the ATLAS detector at the LHC are presented. Data were collected in December 2009 using a minimum-bias trigger during collisions at a centre-of-mass energy of 900 GeV. The charged-particle multiplicity, its dependence on transverse momentum and pseudorapidity, and the relationship between mean transverse momentum and charged-particle multiplicity are measured for events with at least one charged particle in the kinematic range |eta|<2.5 and pT>500 MeV. The measurements are compared to Monte Carlo models of proton-proton collisions and to results from other experiments at the same centre-of-mass energy. The charged-particle multiplicity per event and unit of pseudorapidity at eta = 0 is measured to be 1.333 +/- 0.003 (stat.) +/- 0.040 (syst.), which is 5-15% higher than the Monte Carlo models predict.

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Average value of charged particle multiplicity per event and unit of pseudorapidity in the pseudorapidity range from -0.2 to 0.2.

Charged particle multiplicity as a function of pseudorapidity.

Charged particle multiplicity as a function of transverse momentum.

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