(Anti-)deuteron production in pp collisions at $\sqrt{s}=13 \ \text {TeV}$

The ALICE collaboration Acharya, S. ; Adamova, Dagmar ; Adler, Alexander ; et al.
Eur.Phys.J.C 80 (2020) 889, 2020.
Inspire Record 1784203 DOI 10.17182/hepdata.97183

The study of (anti-)deuteron production in pp collisions has proven to be a powerful tool to investigate the formation mechanism of loosely bound states in high energy hadronic collisions. In this paper the production of $\text{(anti-)deuterons}$ is studied as a function of the charged particle multiplicity in inelastic pp collisions at $\sqrt{s}=13$ TeV using the ALICE experiment. Thanks to the large accumulated integrated luminosity, it has been possible to measure (anti-)deuteron production in pp collisions up to the same charged particle multiplicity ($\rm{d} N_{ch}/\rm{d}\eta\sim26$) as measured in p-Pb collisions at similar centre-of-mass energies. Within the uncertainties, the deuteron yield in pp collisions resembles the one in p-Pb interactions, suggesting a common formation mechanism behind the production of light nuclei in hadronic interactions. In this context the measurements are compared with the expectations of coalescence and Statistical Hadronisation Models (SHM).

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Transverse momentum distributions of deuterons in the INEL>0 pp collisions

Transverse momentum distributions of deuterons in the INEL pp collisions

Transverse momentum distributions of anti-deuterons in the INEL>0 pp collisions

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Anisotropic flow in Xe-Xe collisions at $\mathbf{\sqrt{s_{\rm{NN}}} = 5.44}$ TeV

The ALICE collaboration Acharya, S. ; Torales - Acosta, Fernando ; Adamova, Dagmar ; et al.
Phys.Lett.B 784 (2018) 82-95, 2018.
Inspire Record 1671792 DOI 10.17182/hepdata.84283

The first measurements of anisotropic flow coefficients $v_{\rm{n}}$ for mid-rapidity charged particles in Xe-Xe collisions at $\sqrt{s_{\rm{NN}}} = 5.44$ TeV are presented. Comparing these measurements to those from Pb-Pb collisions at $\sqrt{s_{\rm{NN}}} = 5.02$ TeV, $v_{2}$ is found to be suppressed for mid-central collisions at the same centrality, and enhanced for central collisions. The values of $v_{3}$ are generally larger in Xe-Xe than in Pb-Pb at a given centrality. These observations are consistent with expectations from hydrodynamic predictions. When both $v_{2}$ and $v_{3}$ are divided by their corresponding eccentricities for a variety of initial state models, they generally scale with transverse density when comparing Xe-Xe and Pb-Pb, with some deviations observed in central Xe-Xe and Pb-Pb collisions. These results assist in placing strong constraints on both the initial state geometry and medium response for relativistic heavy-ion collisions.

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First measurement of jet mass in Pb–Pb and p–Pb collisions at the LHC

The ALICE collaboration Acharya, S. ; Adamova, Dagmar ; Aggarwal, Madan Mohan ; et al.
Phys.Lett.B 776 (2018) 249-264, 2018.
Inspire Record 1512107 DOI 10.17182/hepdata.80519

This letter presents the first measurement of jet mass in Pb-Pb and p-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV and 5.02 TeV, respectively. Both the jet energy and the jet mass are expected to be sensitive to jet quenching in the hot Quantum Chromodynamics (QCD) matter created in nuclear collisions at collider energies. Jets are reconstructed from charged particles using the anti-$k_{\rm T}$ jet algorithm and resolution parameter $R = 0.4$. The jets are measured in the pseudorapidity range $|\eta_{\rm{jet}}|<0.5$ and in three intervals of transverse momentum between 60 GeV/$c$ and 120 GeV/$c$. The measurement of the jet mass in central Pb-Pb collisions is compared to the jet mass as measured in p-Pb reference collisions, to vacuum event generators, and to models including jet quenching. It is observed that the jet mass in central Pb-Pb collisions is consistent within uncertainties with p-Pb reference measurements. Furthermore, the measured jet mass in Pb-Pb collisions is not reproduced by the quenching models considered in this letter and is found to be consistent with PYTHIA expectations within systematic uncertainties.

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Anisotropic flow of identified particles in Pb-Pb collisions at $ {\sqrt{s}}_{\mathrm{NN}}=5.02 $ TeV

The ALICE collaboration Acharya, S. ; Torales - Acosta, Fernando ; Adamova, Dagmar ; et al.
JHEP 09 (2018) 006, 2018.
Inspire Record 1672822 DOI 10.17182/hepdata.84717

The elliptic ($v_2$), triangular ($v_3$), and quadrangular ($v_4$) flow coefficients of $\pi^{\pm}$, ${\rm K}^{\pm}$, ${\rm p+\overline{p}}$, ${\Lambda+\overline{\Lambda}}$, ${\rm K}^{\rm 0}_{\rm S}$, and the $\phi$-meson are measured in Pb-Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV. Results obtained with the scalar product method are reported for the rapidity range $\vert y \vert <$ 0.5 as a function of transverse momentum, $p_\text{T}$, at different collision centrality intervals between 0-70%, including ultra-central (0-1%) collisions for $\pi^{\pm}$, ${\rm K}^{\pm}$, and ${\rm p+\overline{p}}$. For $p_\text{T} < 3$ GeV$\kern-0.05em/\kern-0.02em c$, the flow coefficients exhibit a particle mass dependence. At intermediate transverse momenta ($3<p_\text{T}<$~8-10 GeV$\kern-0.05em/\kern-0.02em c$), particles show an approximate grouping according to their type (i.e., mesons and baryons). The $\phi$-meson $v_2$, which tests both particle mass dependence and type scaling, follows ${\rm p+\overline{p}}$ $v_2$ at low $p_\text{T}$ and $\pi^{\pm}$ $v_2$ at intermediate $p_\text{T}$. The evolution of the shape of $v_{\rm n}(p_{\mathrm{T}})$ as a function of centrality and harmonic number $n$ is studied for the various particle species. Flow coefficients of $\pi^{\pm}$, ${\rm K}^{\pm}$, and ${\rm p+\overline{p}}$ for $p_\text{T}<3$ GeV$\kern-0.05em/\kern-0.02em c$ are compared to iEBE-VISHNU and MUSIC hydrodynamical calculations coupled to a hadronic cascade model (UrQMD). The iEBE-VISHNU calculations describe the results fairly well for $p_\text{T} < 2.5$ GeV$\kern-0.05em/\kern-0.02em c$, while MUSIC calculations reproduce the measurements for $p_\text{T} < 1$ GeV$\kern-0.05em/\kern-0.02em c$. A comparison to $v_{\rm n}$ coefficients measured in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV is also provided.

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$\phi$ meson production at forward rapidity in Pb-Pb collisions at $\sqrt{s_\mathrm{NN}}=2.76$ TeV

The ALICE collaboration Acharya, S. ; Torales - Acosta, Fernando ; Adamova, Dagmar ; et al.
Eur.Phys.J.C 78 (2018) 559, 2018.
Inspire Record 1669805 DOI 10.17182/hepdata.83778

$\phi$ meson measurements provide insight into strangeness production, which is one of the key observables for the hot medium formed in high-energy heavy-ion collisions. ALICE measured $\phi$ production through its decay in muon pairs in Pb-Pb collisions at $\sqrt{s_\mathrm{NN}}$ = 2.76 TeV in the intermediate transverse momentum range $2 < p_{\rm T} < 5$ GeV/$c$ and in the rapidity interval $2.5<y<4$. The $\phi$ yield was measured as a function of the transverse momentum and collision centrality. The nuclear modification factor was obtained as a function of the average number of participating nucleons. Results were compared with the ones obtained via the kaon decay channel in the same $p_{\rm T}$ range at midrapidity. The values of the nuclear modification factor in the two rapidity regions are in agreement within uncertainties.

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First measurement of $\Xi_{\rm c}^0$ production in pp collisions at $\mathbf{\sqrt{s}}$ = 7 TeV

The ALICE collaboration Acharya, S. ; Adamova, Dagmar ; Adolfsson, Jonatan ; et al.
Phys.Lett.B 781 (2018) 8-19, 2018.
Inspire Record 1642729 DOI 10.17182/hepdata.83354

The production of the charm-strange baryon $\Xi_{\rm c}^0$ is measured for the first time at the LHC via its semileptonic decay into e$^+\Xi^-\nu_{\rm e}$ in pp collisions at $\sqrt{s}=7$ TeV with the ALICE detector. The transverse momentum ($p_{\rm T}$) differential cross section multiplied by the branching ratio is presented in the interval 1 $<$ $p_{\rm T}$ $<$ 8 GeV/$c$ at mid-rapidity, $|y|$ $<$ 0.5. The transverse momentum dependence of the $\Xi_{\rm c}^0$ baryon production relative to the D$^0$ meson production is compared to predictions of event generators with various tunes of the hadronisation mechanism, which are found to underestimate the measured cross-section ratio.

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Measurement of the inclusive J/ $\psi $ polarization at forward rapidity in pp collisions at $\mathbf {\sqrt{s} = 8}$ TeV

The ALICE collaboration Acharya, S. ; Torales - Acosta, Fernando ; Adamova, Dagmar ; et al.
Eur.Phys.J.C 78 (2018) 562, 2018.
Inspire Record 1672801 DOI 10.17182/hepdata.83784

We report on the measurement of the inclusive J/$\psi$ polarization parameters in pp collisions at a center of mass energy $\sqrt{s} = 8$ TeV with the ALICE detector at the LHC. The analysis is based on a data sample corresponding to an integrated luminosity of 1.23 pb$^{-1}$. J/$\psi$ resonances are reconstructed in their di-muon decay channel in the rapidity interval $2.5 < y < 4.0$ and over the transverse-momentum interval $2 < p_{\rm T} < 15$ GeV/$c$. The three polarization parameters ($\lambda_\theta$, $\lambda_\varphi$, $\lambda_{\theta\varphi}$) are measured as a function of $p_{\rm T}$ both in the helicity and Collins-Soper reference frames. The measured J/$\psi$ polarization parameters are found to be compatible with zero within uncertainties, contrary to expectations from all available predictions. The results are compared with the measurement in pp collisions at $\sqrt{s} = 7$ TeV.

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Energy dependence and fluctuations of anisotropic flow in Pb-Pb collisions at $ \sqrt{s_{\mathrm{NN}}}=5.02 $ and 2.76 TeV

The ALICE collaboration Acharya, S. ; Torales - Acosta, Fernando ; Adamova, Dagmar ; et al.
JHEP 07 (2018) 103, 2018.
Inspire Record 1666817 DOI 10.17182/hepdata.83737

Measurements of anisotropic flow coefficients with two- and multi-particle cumulants for inclusive charged particles in Pb-Pb collisions at $\sqrt{{\textit s}_\text{NN}} = 5.02$ and 2.76 TeV are reported in the pseudorapidity range $|\eta| < 0.8$ and transverse momentum $0.2 < p_\text{T} < 50$ GeV/$c$. The full data sample collected by the ALICE detector in 2015 (2010), corresponding to an integrated luminosity of 12.7 (2.0) $\mu$b$^{-1}$ in the centrality range 0-80%, is analysed. Flow coefficients up to the sixth flow harmonic ($v_6$) are reported and a detailed comparison among results at the two energies is carried out. The $p_\text{T}$ dependence of anisotropic flow coefficients and its evolution with respect to centrality and harmonic number $n$ are investigated. An approximate power-law scaling of the form $v_n(p_\text{T}) \sim p_\text{T}^{n/3}$ is observed for all flow harmonics at low $p_\text{T}$ ($0.2 < p_\text{T} < 3$ GeV/$c$). At the same time, the ratios $v_n/v_m^{n/m}$ are observed to be essentially independent of $p_\text{T}$ for most centralities up to about $p_\text{T} = 10$ GeV/$c$. Analysing the differences among higher-order cumulants of elliptic flow ($v_2$), which have different sensitivities to flow fluctuations, a measurement of the standardised skewness of the event-by-event $v_2$ distribution $P(v_2)$ is reported and constraints on its higher moments are provided. The Elliptic Power distribution is used to parametrise $P(v_2)$, extracting its parameters from fits to cumulants. The measurements are compared to different model predictions in order to discriminate among initial-state models and to constrain the temperature dependence of the shear viscosity to entropy-density ratio.

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Measurement of Z$^0$-boson production at large rapidities in Pb-Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV

The ALICE collaboration Acharya, S. ; Adamova, Dagmar ; Adolfsson, Jonatan ; et al.
Phys.Lett.B 780 (2018) 372-383, 2018.
Inspire Record 1639439 DOI 10.17182/hepdata.82813

The production of Z$^0$ bosons at large rapidities in Pb-Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV is reported. Z$^0$ candidates are reconstructed in the dimuon decay channel (${\rm Z}^0 \rightarrow \mu^+\mu^-$), based on muons selected with pseudo-rapidity $-4.0<\eta<-2.5$ and $p_{\rm T}>20$ GeV/$c$. The invariant yield and the nuclear modification factor, $R_{\rm AA}$, are presented as a function of rapidity and collision centrality. The value of $R_{\rm AA}$ for the 0-20% central Pb-Pb collisions is $0.67 \pm 0.11 \, \mbox{(stat.)} \, \pm 0.03 \, \mbox{(syst.)} \, \pm 0.06 \, \mbox{(corr. syst.)}$, exhibiting a deviation of $2.6 \sigma$ from unity. The results are well-described by calculations that include nuclear modifications of the parton distribution functions, while the predictions using vacuum PDFs deviate from data by $2.3\sigma$ in the 0-90% centrality class and by $3\sigma$ in the 0-20% central collisions.

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Transverse momentum spectra and nuclear modification factors of charged particles in pp, p-Pb and Pb-Pb collisions at the LHC

The ALICE collaboration Acharya, S. ; Torales - Acosta, Fernando ; Adamova, Dagmar ; et al.
JHEP 11 (2018) 013, 2018.
Inspire Record 1657384 DOI 10.17182/hepdata.86210

We report the measured transverse momentum ($p_{\rm T}$) spectra of primary charged particles from pp, p-Pb and Pb-Pb collisions at a center-of-mass energy $\sqrt{s_{\rm NN}} = 5.02$ TeV in the kinematic range of $0.15<p_{\rm T}<50$ GeV/$c$ and $|\eta|< 0.8$. A significant improvement of systematic uncertainties motivated the reanalysis of data in pp and Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 2.76$ TeV, as well as in p-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV, which is also presented. Spectra from Pb-Pb collisions are presented in nine centrality intervals and are compared to a reference spectrum from pp collisions scaled by the number of binary nucleon-nucleon collisions. For central collisions, the $p_{\rm T}$ spectra are suppressed by more than a factor of 7 around 6-7 GeV/$c$ with a significant reduction in suppression towards higher momenta up to 30 GeV/$c$. The nuclear modification factor $R_{\rm pPb}$, constructed from the pp and p-Pb spectra measured at the same collision energy, is consistent with unity above 8 GeV/$c$. While the spectra in both pp and Pb-Pb collisions are substantially harder at $\sqrt{s_{\rm NN}} = 5.02$ TeV compared to 2.76 TeV, the nuclear modification factors show no significant collision energy dependence. The obtained results should provide further constraints on the parton energy loss calculations to determine the transport properties of the hot and dense QCD matter.

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Measurement of D$^{0}$, D$^{+}$, D$^{*+}$ and D$_{s}^{+}$ production in Pb-Pb collisions at $ \sqrt{{\mathrm{s}}_{\mathrm{NN}}}=5.02 $ TeV

The ALICE collaboration Acharya, S. ; Torales - Acosta, Fernando ; Adamova, Dagmar ; et al.
JHEP 10 (2018) 174, 2018.
Inspire Record 1669819 DOI 10.17182/hepdata.88168

We report measurements of the production of prompt D$^0$, D$^+$, D$^{*+}$ and D$^+_{\rm s}$ mesons in Pb-Pb collisions at the centre-of-mass energy per nucleon-nucleon pair $\sqrt{s_{\rm NN}}=5.02$ TeV, in the centrality classes 0-10%, 30-50% and 60-80%. The D-meson production yields are measured at mid-rapidity ($|y|<0.5$) as a function of transverse momentum ($p_{\rm T}$). The $p_{\rm T}$ intervals covered in central collisions are: $1<p_{\rm T}<50$ Gev/$c$ for D$^0$, $2<p_{\rm T}<50$ GeV/$c$ for D$^+$, $3<p_{\rm T}<50$ GeV/$c$ for D$^{*+}$, and $4<p_{\rm T}<16$ GeV/$c$ for D$^+_{\rm s}$ mesons. The nuclear modification factors ($R_{\rm AA}$) for non-strange D mesons (D$^0$, D$^+$, D$^{*+}$) show minimum values of about 0.2 for $p_{\rm T}$ = 6-10 GeV/$c$ in the most central collisions and are compatible within uncertainties with those measured at $\sqrt{s_{\rm NN}}=2.76$ TeV. For D$^+_{\rm s}$ mesons, the values of $R_{\rm AA}$ are larger than those of non-strange D mesons, but compatible within uncertainties. In central collisions the average $R_{\rm AA}$ of non-strange D mesons is compatible with that of charged particles for $p_{\rm T} > 8$ GeV/$c$, while it is larger at lower $p_{\rm T}$. The nuclear modification factors for strange and non-strange D mesons are also compared to theoretical models with different implementations of in-medium energy loss.

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Search for collectivity with azimuthal J/$\psi$-hadron correlations in high multiplicity p-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 and 8.16 TeV

The ALICE collaboration Acharya, S. ; Adamova, Dagmar ; Adolfsson, Jonatan ; et al.
Phys.Lett.B 780 (2018) 7-20, 2018.
Inspire Record 1624550 DOI 10.17182/hepdata.79406

We present a measurement of azimuthal correlations between inclusive J/$\psi$ and charged hadrons in p-Pb collisions recorded with the ALICE detector at the CERN LHC. The J/$\psi$ are reconstructed at forward (p-going, 2.03 $<$ y $<$ 3.53) and backward (Pb-going, $-$4.46 $<$ y $<$ $-$2.96) rapidity via their $\mu^+\mu^-$ decay channel, while the charged hadrons are reconstructed at mid-rapidity ($|\eta|$ $<$ 1.8). The correlations are expressed in terms of associated charged-hadron yields per J/$\psi$ trigger. A rapidity gap of at least 1.5 units is required between the trigger J/$\psi$ and the associated charged hadrons. Possible correlations due to collective effects are assessed by subtracting the associated per-trigger yields in the low-multiplicity collisions from those in the high-multiplicity collisions. After the subtraction, we observe a strong indication of remaining symmetric structures at $\Delta\varphi$ $\approx$ 0 and $\Delta\varphi$ $\approx$ $\pi$, similar to those previously found in two-particle correlations at middle and forward rapidity. The corresponding second-order Fourier coefficient ($v_2$) in the transverse momentum interval between 3 and 6 GeV/$c$ is found to be positive with a significance of about 5$\sigma$. The obtained results are similar to the J/$\psi$ $v_2$ coefficients measured in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV, suggesting a common mechanism at the origin of the J/$\psi$ $v_2$.

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Evidence for top quark production in nucleus-nucleus collisions

The CMS collaboration Sirunyan, Albert M ; Tumasyan, Armen ; Adam, Wolfgang ; et al.
Nature Physics and tables can be found at http://cms-results.web.cern.ch/cms-results/public-results/publications/HIN-19-001 (CMS Public Pages), 2020.
Inspire Record 1802092 DOI 10.17182/hepdata.93878

Ultrarelativistic heavy ion collisions recreate in the laboratory the thermodynamical conditions prevailing in the early universe up to 10$^{-6}$ seconds, thereby allowing the study of the quark-gluon plasma (QGP), a state of quantum chromodynamics (QCD) matter with deconfined partons. The top quark, the heaviest elementary particle known, is accessible in nucleus-nucleus collisions at the CERN LHC, and constitutes a novel probe of the QGP. Here, we report the first-ever evidence for the production of top quarks in nucleus-nucleus collisions, using lead-lead collision data at a nucleon-nucleon centre-of-mass energy of 5.02 TeV recorded by the CMS experiment. Two methods are used to measure the cross section for top quark pair production ($\sigma_\mathrm{t\bar{t}}$) via the decay into charged leptons (electrons or muons) and bottom quarks. One method relies on the leptonic information alone, and the second one exploits, in addition, the presence of bottom quarks. The measured cross sections, $\sigma_\mathrm{t\bar{t}} = $ 2.54$^{+0.84}_{-0.74}$ and 2.03$^{+0.71}_{-0.64}$ $\mu$b, respectively, are compatible with expectations from scaled proton-proton data and QCD predictions.

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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.

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Underlying Event properties in pp collisions at $\sqrt{s}$ = 13 TeV

The ALICE collaboration Acharya, Shreyasi ; Adamova, Dagmar ; Adler, Alexander ; et al.
JHEP 04 (2020) 192, 2020.
Inspire Record 1762350 DOI 10.17182/hepdata.94414

This article reports measurements characterizing the Underlying Event (UE) associated with hard scatterings at midrapidity in pp collisions at $\sqrt{s}=13$ TeV. The hard scatterings are identified by the leading particle, the charged particle with the highest transverse momentum ($p_{\rm T}^{\rm leading}$) in the event. Charged-particle number and summed transverse-momentum densities are measured in different azimuthal regions defined with respect to the leading particle direction: Toward, Transverse, and Away. The Toward and Away regions contain the fragmentation products of the hard scatterings in addition to the UE contribution, whereas particles in the Transverse region are expected to originate predominantly from the UE. The study is performed as a function of $p_{\rm T}^{\rm leading}$ with three different $p_{\rm T}$ thresholds for the associated particles, $p_{\rm T}^{\rm min} >$ 0.15, 0.5, and 1.0 GeV/$c$. The charged-particle density in the Transverse region rises steeply for low values of $p_{\rm T}^{\rm leading}$ and reaches a plateau. The results confirm the trend that the charged-particle density in the Transverse region shows a stronger increase with $\sqrt{s}$ than the inclusive charged-particle density at midrapidity. The UE activity is increased by approximately 20% when going from 7 to 13 TeV. The plateau in the Transverse region ($5 < p_{\rm T}^{\rm leading} < ~ 40$ GeV/$c$ ) is further characterized by the probability distribution of its charged-particle multiplicity normalized to its average value (relative transverse activity, $R_{T}$) and the mean transverse momentum as a function of $R_{T}$. Experimental results are compared to model calculations using PYTHIA 8 and EPOS LHC. The overall agreement between models and data is within 30%. These measurements provide new insights on the interplay between hard scatterings and the associated UE in pp collisions.

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$\Lambda_{\rm c}^+$ production in pp collisions at $\sqrt{s} = 7$ TeV and in p-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV

The ALICE collaboration Acharya, Shreyasi ; Torales - Acosta, Fernando ; Adamova, Dagmar ; et al.
JHEP 04 (2018) 108, 2018.
Inspire Record 1645239 DOI 10.17182/hepdata.81727

The $p_{\rm T}$-differential production cross section of prompt $\Lambda_{\rm c}^+$ charmed baryons was measured with the ALICE detector at the Large Hadron Collider (LHC) in pp collisions at $\sqrt{s} = 7$ TeV and in p-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV at midrapidity. The $\Lambda_{\rm c}^+$ and ${\overline{\Lambda}}_{\rm c}^-$ were reconstructed in the hadronic decay modes $\Lambda_{\rm c}^+\rightarrow {\rm p}{\rm K^-}\pi^+$, $\Lambda_{\rm c}^+\rightarrow {\rm p}{\rm K_{\rm S}^0}$ and in the semileptonic channel $\Lambda_{\rm c}^+\rightarrow {\rm e^+}\nu_{\rm e}\Lambda$ (and charge conjugates). The measured values of the $\Lambda_{\rm c}^+/{\rm D_0}$ ratio, which is sensitive to the c-quark hadronisation mechanism, and in particular to the production of baryons, are presented and are larger than those measured previously in different colliding systems, centre-of-mass energies, rapidity and $p_{\rm T}$ intervals, where the $\Lambda_{\rm c}^+$ production process may differ. The results are compared with the expectations obtained from perturbative Quantum Chromodynamics calculations and Monte Carlo event generators. Neither perturbative QCD calculations nor Monte Carlo models reproduce the data, indicating that the fragmentation of heavy-flavour baryons is not well understood. The first measurement at the LHC of the $\Lambda_{\rm c}^+$ nuclear modification factor, $R_{\rm pPb}$, is also presented. The $R_{\rm pPb}$ is found to be consistent with unity and with that of D mesons within the uncertainties, and consistent with a theoretical calculation that includes cold nuclear matter effects and a calculation that includes charm quark interactions with a deconfined medium.

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Investigation of the p-$\Sigma^{0}$ interaction via femtoscopy in pp collisions

The ALICE collaboration Acharya, Shreyasi ; Adamova, Dagmar ; Adler, Alexander ; et al.
Phys.Lett.B 805 (2020) 135419, 2020.
Inspire Record 1762369 DOI 10.17182/hepdata.94238

This Letter presents the first direct investigation of the p-$\Sigma^{0}$ interaction, using the femtoscopy technique in high-multiplicity pp collisions at $\sqrt{s}$ = 13 TeV measured by the ALICE detector. The $\Sigma^{0}$ is reconstructed via the decay channel to $\Lambda \gamma$, and the subsequent decay of $\Lambda$ to p$\pi^-$. The photon is detected via the conversion in material to e$^{+}$e$^{-}$ pairs exploiting the unique capability of the ALICE detector to measure electrons at low transverse momenta. The measured p-$\Sigma^{0}$ correlation indicates a shallow strong interaction. The comparison of the data to several theoretical predictions obtained employing the $Correlation~Analysis~Tool~using~the~Schr\"odinger~Equation$ (CATS) and the Lednick\'y-Lyuboshits approach shows that the current experimental precision does not yet allow to discriminate between different models, as it is the case for the available scattering and hypernuclei data. Nevertheless, the p-$\Sigma^{0}$ correlation function is found to be sensitive to the strong interaction, and driven by the interplay of the different spin and isospin channels. This pioneering study demonstrates the feasibility of a femtoscopic measurement in the p-$\Sigma^{0}$ channel and with the expected larger data samples in LHC Run 3 and Run 4, the p-$\Sigma^{0}$ interaction will be constrained with high precision.

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$ϒ$ production in p–Pb collisions at $\sqrt{s_{NN}}$=8.16 TeV

The ALICE collaboration Acharya, Shreyasi ; Adamova, Dagmar ; Adler, Alexander ; et al.
Phys.Lett.B 806 (2020) 135486, 2020.
Inspire Record 1762360 DOI 10.17182/hepdata.95539

$\Upsilon$ production in p-Pb interactions is studied at the centre-of-mass energy per nucleon-nucleon collision $\sqrt{s_{\rm{NN}}}$ = 8.16 TeV with the ALICE detector at the CERN LHC. The measurement is performed reconstructing bottomonium resonances via their dimuon decay channel, in the centre-of-mass rapidity intervals $2.03 < y_{\rm{cms}} < 3.53$ and $-4.46 < y_{\rm{cms}} < -2.96$, down to zero transverse momentum. In this work, results on the inclusive $\Upsilon(1\rm{S})$ production cross section as a function of rapidity and transverse momentum are presented. The corresponding nuclear modification factor shows a suppression of the $\Upsilon(1\rm{S})$ yields with respect to pp collisions, both at forward and backward rapidity. This suppression is stronger in the low transverse momentum region and shows no significant dependence on the centrality of the interactions. Furthermore, the $\Upsilon(2\rm{S})$ nuclear modification factor is also evaluated, suggesting a suppression similar to that of the $\Upsilon(1\rm{S})$. A first measurement of the $\Upsilon(3\rm{S})$ has also been performed. Finally, results are compared with previous measurements performed by ALICE in p-Pb collisions at $\sqrt{s_{\rm{NN}}}$ = 5.02 TeV and with theoretical calculations.

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Kaon femtoscopy in Pb-Pb collisions at $\sqrt{s_{\rm{NN}}}$ = 2.76 TeV

The ALICE collaboration Acharya, Shreyasi ; Adam, Jaroslav ; Adamova, Dagmar ; et al.
Phys.Rev.C 96 (2017) 064613, 2017.
Inspire Record 1621809 DOI 10.17182/hepdata.79128

We present the results of three-dimensional femtoscopic analyses for charged and neutral kaons recorded by ALICE in Pb-Pb collisions at $\sqrt{s_{\rm{NN}}}$ = 2.76 TeV. Femtoscopy is used to measure the space-time characteristics of particle production from the effects of quantum statistics and final-state interactions in two-particle correlations. Kaon femtoscopy is an important supplement to that of pions because it allows one to distinguish between different model scenarios working equally well for pions. In particular, we compare the measured 3D kaon radii with a purely hydrodynamical calculation and a model where the hydrodynamic phase is followed by a hadronic rescattering stage. The former predicts an approximate transverse mass ($m_{\mathrm{T}}$) scaling of source radii obtained from pion and kaon correlations. This $m_{\mathrm{T}}$ scaling appears to be broken in our data, which indicates the importance of the hadronic rescattering phase at LHC energies. A $k_{\mathrm{T}}$ scaling of pion and kaon source radii is observed instead. The time of maximal emission of the system is estimated using the three-dimensional femtoscopic analysis for kaons. The measured emission time is larger than that of pions. Our observation is well supported by the hydrokinetic model predictions.

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Multiparticle correlation studies in pPb collisions at $\sqrt{s_\mathrm{NN}} =$ 8.16 TeV

The CMS collaboration Sirunyan, Albert M ; Tumasyan, Armen ; Adam, Wolfgang ; et al.
Phys.Rev.C 101 (2020) 014912, 2020.
Inspire Record 1731568 DOI 10.17182/hepdata.88288

The second- and third-order azimuthal anisotropy Fourier harmonics of charged particles produced in pPb collisions, at $\sqrt{s_\mathrm{NN}} =$ 8.16 TeV, are studied over a wide range of event multiplicities. Multiparticle correlations are used to isolate global properties stemming from the collision overlap geometry. The second-order "elliptic" harmonic moment is obtained with high precision through four-, six-, and eight-particle correlations and, for the first time, the third-order "triangular" harmonic moment is studied using four-particle correlations. A sample of peripheral PbPb collisions at $\sqrt{s_\mathrm{NN}} =$ 5.02 TeV that covers a similar range of event multiplicities as the pPb results is also analyzed. Model calculations of initial-state fluctuations in pPb and PbPb collisions can be directly compared to the high precision experimental results. This work provides new insight into the fluctuation-driven origin of the $v_3$ coefficients in pPb and PbPb collisions, and into the dominating overall collision geometry in PbPb collisions at the earliest stages of heavy ion interactions.

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Measurement of charged jet cross section in $pp$ collisions at ${\sqrt{s}=5.02}$ TeV

The ALICE collaboration Acharya, Shreyasi ; Adamova, Dagmar ; Adhya, Souvik Priyam ; et al.
Phys.Rev.D 100 (2019) 092004, 2019.
Inspire Record 1733689 DOI 10.17182/hepdata.91239

The cross section of jets reconstructed from charged particles is measured in the transverse momentum range of $5<p_\mathrm{T}<100\ \mathrm{GeV}/c$ in pp collisions at the center-of-mass energy of $\sqrt{s} = 5.02\ \mathrm{TeV}$ with the ALICE detector. The jets are reconstructed using the anti-$k_\mathrm{T}$ algorithm with resolution parameters $R=0.2$, $0.3$, $0.4$, and $0.6$ in the pseudorapidity range $|\eta|< 0.9-R$. The charged jet cross sections are compared with the leading order (LO) and to next-to-leading order (NLO) perturbative Quantum ChromoDynamics (pQCD) calculations. It was found that the NLO calculations agree better with the measurements. The cross section ratios for different resolution parameters were also measured. These ratios increase from low $p_\mathrm{T}$ to high $p_\mathrm{T}$ and saturate at high $p_\mathrm{T}$, indicating that jet collimation is larger at high $p_\mathrm{T}$ than at low $p_\mathrm{T}$. These results provide a precision test of pQCD predictions and serve as a baseline for the measurement in Pb$-$Pb collisions at the same energy to quantify the effects of the hot and dense medium created in heavy-ion collisions at the LHC.

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Multiplicity dependence of (anti-)deuteron production in pp collisions at $\sqrt{s}$ = 7 TeV

The ALICE collaboration Acharya, Shreyasi ; Torales - Acosta, Fernando ; Adamova, Dagmar ; et al.
Phys.Lett.B 794 (2019) 50-63, 2019.
Inspire Record 1721729 DOI 10.17182/hepdata.93741

In this letter, the production of deuterons and anti-deuterons in pp collisions at $\sqrt{s} = 7$ TeV is studied as a function of the charged-particle multiplicity density at mid-rapidity with the ALICE detector at the LHC. Production yields are measured at mid-rapidity in five multiplicity classes and as a function of the deuteron transverse momentum ($p_{\rm{T}}$). The measurements are discussed in the context of hadron-coalescence models. The coalescence parameter $B_{2}$, extracted from the measured spectra of (anti-)deuterons and primary (anti-)protons, exhibits no significant $p_{\rm{T}}$-dependence for $p_{\rm{T}} < 3$ GeV/$c$, in agreement with the expectations of a simple coalescence picture. At fixed transverse momentum per nucleon, the $B_{2}$ parameter is found to decrease smoothly from low multiplicity pp Pb-Pb collisions, in qualitative agreement with more elaborate coalescence models. The measured mean transverse momentum of (anti-)deuterons in pp is not reproduced by the Blast-Wave model calculations that simultaneously describe pion, kaon and proton spectra, in contrast to central Pb-Pb collisions. The ratio between the $p_{\rm{T}}$-integrated yield of deuterons to protons, d/p, is found to increase with the charged-particle multiplicity, as observed in inelastic pp collisions at different centre-of-mass energies. The d/p ratios are reported in a wide range, from the lowest to the highest multiplicity values measured in pp collisions at the LHC.

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Analysis of the apparent nuclear modification in peripheral Pb–Pb collisions at 5.02 TeV

The ALICE collaboration Acharya, Shreyasi ; Torales - Acosta, Fernando ; Adamova, Dagmar ; et al.
Phys.Lett.B 793 (2019) 420-432, 2019.
Inspire Record 1672944 DOI 10.17182/hepdata.89396

Charged-particle spectra at midrapidity are measured in Pb-Pb collisions at the centre-of-mass energy per nucleon-nucleon pair $\sqrt{s_{\rm NN}}$ = 5.02 TeV and presented in centrality classes ranging from most central (0-5%) to most peripheral (95-100%) collisions. Possible medium effects are quantified using the nuclear modification factor ($R_{\rm AA}$) by comparing the measured spectra with those from proton-proton collisions, scaled by the number of independent nucleon-nucleon collisions obtained from a Glauber model. At large transverse momenta ($8<p_{\rm T}<20$ GeV/$c$), the average $R_{\rm AA}$ is found to increase from about $0.15$ in 0-5% central to a maximum value of about $0.8$ in 75-85% peripheral collisions, beyond which it falls off strongly to below $0.2$ for the most peripheral collisions. Furthermore, $R_{\rm AA}$ initially exhibits a positive slope as a function of $p_{\rm T}$ in the $8$-$20$ GeV/$c$ interval, while for collisions beyond the 80% class the slope is negative. To reduce uncertainties related to event selection and normalization, we also provide the ratio of $R_{\rm AA}$ in adjacent centrality intervals. Our results in peripheral collisions are consistent with a PYTHIA-based model without nuclear modification, demonstrating that biases caused by the event selection and collision geometry can lead to the apparent suppression in peripheral collisions. This explains the unintuitive observation that $R_{\rm AA}$ is below unity in peripheral Pb-Pb, but equal to unity in minimum-bias p-Pb collisions despite similar charged-particle multiplicities.

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W$^+$W$^-$ boson pair production in proton-proton collisions at $\sqrt{s} =$ 13 TeV

The CMS collaboration Sirunyan, Albert M ; Tumasyan, Armen ; Adam, Wolfgang ; et al.
CMS-SMP-18-004, 2020.
Inspire Record 1814328 DOI 10.17182/hepdata.94259

A measurement of the W$^+$W$^-$ boson pair production cross section in proton-proton collisions at $\sqrt{s} =$ 13 TeV is presented. The data used in this study are collected with the CMS detector at the CERN LHC and correspond to an integrated luminosity of 35.9 fb$^{-1}$. The W$^+$W$^-$ candidate events are selected by requiring two oppositely charged leptons (electrons or muons). Two methods for reducing background contributions are employed. In the first one, a sequence of requirements on kinematic quantities is applied allowing a measurement of the total production cross section: 117.6 $\pm$ 6.8 pb, which agrees well with the theoretical prediction. Fiducial cross sections are also reported for events with zero or one jet, and the change in the zero-jet fiducial cross section with the jet transverse momentum threshold is measured. Normalized differential cross sections are reported within the fiducial region. A second method for suppressing background contributions employs two random forest classifiers. The analysis based on this method includes a measurement of the total production cross section and also a measurement of the normalized jet multiplicity distribution in W$^+$W$^-$ events. Finally, a dilepton invariant mass distribution is used to probe for physics beyond the standard model in the context of an effective field theory, and constraints on the presence of dimension-6 operators are derived.

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Charged jet cross section and fragmentation in proton-proton collisions at $\sqrt{s}$ = 7 TeV

The ALICE collaboration Acharya, Shreyasi ; Torales - Acosta, Fernando ; Adamova, Dagmar ; et al.
Phys.Rev.D 99 (2019) 012016, 2019.
Inspire Record 1693308 DOI 10.17182/hepdata.86229

We report the differential charged jet cross section and jet fragmentation distributions measured with the ALICE detector in proton-proton collisions at a centre-of-mass energy $\sqrt{s}=$ 7 TeV. Jets with pseudo-rapidity $\left| \eta \right| < {\rm 0.5}$ are reconstructed from charged particles using the anti-$k_{\rm T}$ jet finding algorithm with a resolution parameter $R$ = 0.4. The jet cross section is measured in the transverse momentum interval 5 $\leq p_{\rm T}^{\rm ch \; jet} <$ 100 GeV/$c$. Jet fragmentation is studied measuring the scaled transverse momentum spectra of the charged constituents of jets in four intervals of jet transverse momentum between 5 GeV/$c$ and 30 GeV/$c$. The measurements are compared to calculations from the PYTHIA model as well as next-to-leading order perturbative QCD calculations with POWHEG + PYTHIA8. The charged jet cross section is described by POWHEG for the entire measured range of $p_{\rm T}^{\rm ch \; jet}$. For $p_{\rm T}^{\rm ch \; jet}$ $>$ 40 GeV/$c$, the PYTHIA calculations also agree with the measured charged jet cross section. PYTHIA6 simulations describe the fragmentation distributions to 15%. Larger discrepancies are observed for PYTHIA8.

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