Date

Investigations of anisotropic flow using multi-particle azimuthal correlations in pp, p-Pb, Xe-Xe, and Pb-Pb collisions at the LHC

The ALICE collaboration Acharya, Shreyasi ; Adamova, Dagmar ; Adhya, Souvik Priyam ; et al.
Phys.Rev.Lett. 123 (2019) 142301, 2019.
Inspire Record 1723697 DOI 10.17182/hepdata.90955

Measurements of anisotropic flow coefficients ($v_n$) and their cross-correlations using two- and multi-particle cumulant methods are reported in collisions of pp at $\sqrt{s} = 13$ TeV, p-Pb at $\sqrt{s_{_{\rm NN}}} = 5.02$ TeV, Xe-Xe at $\sqrt{s_{_{\rm NN}}} = 5.44$ TeV, and Pb-Pb at $\sqrt{s_{_{\rm NN}}} = 5.02$ TeV recorded with the ALICE detector. The multiplicity dependence of $v_n$ is studied in a very wide range from 20 to 3000 particles produced in the mid-rapidity region $|\eta|<0.8$ for the transverse momentum range $0.2 < p_{\rm T} < 3.0$ GeV/$c$. An ordering of the coefficients $v_2 > v_3 > v_4$ is found in pp and p-Pb collisions, similar to that seen in large collision systems, while a weak $v_2$ multiplicity dependence is observed relative to nucleus-nucleus collisions in the same multiplicity range. Using a novel subevent method, $v_{2}$ measured with four-particle cumulants is found to be compatible with that from six-particle cumulants in pp and p-Pb collisions. The magnitude of the correlation between $v_n^2$ and $v_m^2$, evaluated with the symmetric cumulants SC$(m,n)$ is observed to be positive at all multiplicities for $v_2$ and $v_4$, while for $v_2$ and $v_3$ it is negative and changes sign for multiplicities below 100, which may indicate a different $v_n$ fluctuation pattern in this multiplicity range. The observed long-range multi-particle azimuthal correlations in high multiplicity pp and p-Pb collisions can neither be described by PYTHIA 8 nor by IP-Glasma+MUSIC+UrQMD model calculations, and hence provide new insights into the understanding of collective effects in small collision systems.

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Inclusive J/$\psi$ production at mid-rapidity in pp collisions at $\sqrt{s}$ = 5.02 TeV

The ALICE collaboration Acharya, Shreyasi ; Adamova, Dagmar ; Adhya, Souvik Priyam ; et al.
JHEP 10 (2019) 084, 2019.
Inspire Record 1735351 DOI 10.17182/hepdata.91186

Inclusive J/$\psi$ production is studied in minimum-bias proton-proton collisions at a centre-of-mass energy of $\sqrt{s}$ = 5.02 TeV by ALICE at the CERN LHC. The measurement is performed at mid-rapidity ($|y| < 0.9$) in the dielectron decay channel down to zero transverse momentum $p_{\rm T}$, using a data sample corresponding to an integrated luminosity of $L_{\rm int} = 19.4 \pm$ 0.4 nb$^{-1}$. The measured $p_{\rm T}$-integrated inclusive J/$\psi$ production cross section is d$\sigma$/d$y$ = 5.64 $\pm$ 0.22 (stat.) $\pm 0.33$ (syst.) $\pm 0.12$ (lumi.) $\mu$b. The $p_{\rm T}$-differential cross section d$^{2} \sigma$/d$p_{\rm T}$d$y$ is measured in the $p_{\rm T}$ range 0$-$10 GeV/$c$ and compared with state-of-the-art perturbative QCD calculations. The J/$\psi$ $\langle p_{\rm T} \rangle$ and $\langle p_{\rm T}^{2} \rangle$ are extracted and compared with results obtained at other collision energies.

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Prompt D$^{0}$, D$^{+}$, and D$^{*+}$ production in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV

The ALICE collaboration Acharya, Shreyasi ; Adamova, Dagmar ; Adler, Alexander ; et al.
JHEP 01 (2022) 174, 2022.
Inspire Record 1946131 DOI 10.17182/hepdata.127979

The production of prompt D$^{0}$, D$^{+}$, and D$^{*+}$ mesons was measured at midrapidity (|y|< 0.5) in Pb-Pb collisions at the centre-of-mass energy per nucleon-nucleon pair $\sqrt{s_{\rm NN}}$ = 5.02 TeV with the ALICE detector at the LHC. The D mesons were reconstructed via their hadronic decay channels and their production yields were measured in central (0-10%) and semicentral (30-50%) collisions. The measurement was performed up to a transverse momentum ($p_{\rm T}$) of 36 or 50 GeV/$c$ depending on the D meson species and the centrality interval. For the first time in Pb-Pb collisions at the LHC, the yield of D$^0$ mesons was measured down to $p_{\rm T}$ = 0, which allowed a model-independent determination of the $p_{\rm T}$-integrated yield per unit of rapidity (d$N$/d$y$). A maximum suppression by a factor 5 and 2.5 was observed with the nuclear modification factor ($R_{\rm AA}$) of prompt D mesons at $p_{\rm T}$ = 6-8 GeV/$c$ for the 0-10% and 30-50% centrality classes, respectively. The D-meson $R_{\rm AA}$ is compared with that of charged pions, charged hadrons, and J/$\psi$ mesons as well as with theoretical predictions. The analysis of the agreement between the measured $R_{\rm AA}$, elliptic ($v_2$) and triangular ($v_3$) flow, and the model predictions allowed us to constrain the charm spatial diffusion coefficient $D_s$. Furthermore the comparison of $R_{\rm AA}$ and $v_2$ with different implementations of the same models provides an important insight into the role of radiative energy loss as well as charm quark recombination in the hadronisation mechanisms.

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Measurement of prompt D$^{0}$, $\Lambda_{c}^{+}$, and $\Sigma_{c}^{0,++}$(2455) production in pp collisions at $\sqrt{s} = 13$ TeV

The ALICE collaboration Acharya, Shreyasi ; Adamova, Dagmar ; Adler, Alexander ; et al.
Phys.Rev.Lett. 128 (2022) 012001, 2022.
Inspire Record 1868463 DOI 10.17182/hepdata.127976

The $p_{\rm T}$-differential production cross sections of prompt D$^{0}$, $\Lambda_{\rm c}^{+}$, and $\Sigma_{\rm c}^{0,++}(2455)$ charmed hadrons are measured at midrapidity ($|y| < 0.5$) in pp collisions at $\sqrt{s} = 13$ TeV. This is the first measurement of $\Sigma_{\rm c}^{0,++}$ production in hadronic collisions. Assuming the same production yield for the three $\Sigma_{\rm c}^{0,+,++}$ isospin states, the baryon-to-meson cross section ratios $\Sigma_{\rm c}^{0,+,++}/{\rm D}^{0}$ and $\Lambda_{\rm c}^{+}/{\rm D}^{0}$ are calculated in the transverse momentum ($p_{\rm T}$) intervals $2 < p_{\rm T} < 12$ GeV/$c$ and $1 < p_{\rm T} < 24$ GeV/$c$. Values significantly larger than in e$^{+}$e$^{-}$ collisions are observed, indicating for the first time that baryon enhancement in hadronic collisions also extends to the $\Sigma_{\rm c}$. The feed-down contribution to $\Lambda_{\rm c}^{+}$ production from $\Sigma_{\rm c}^{0,+,++}$ is also reported and is found to be larger than in e$^{+}$e$^{-}$ collisions. The data are compared with predictions from event generators and other phenomenological models, providing a sensitive test of the different charm-hadronisation mechanisms implemented in the models.

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Production of light-flavor hadrons in pp collisions at $\sqrt{s}$ = 7 and $\sqrt{s}$ = 13 TeV

The ALICE collaboration Acharya, Shreyasi ; Adamova, Dagmar ; Adler, Alexander ; et al.
Eur.Phys.J.C 81 (2021) 256, 2021.
Inspire Record 1797443 DOI 10.17182/hepdata.100303

The production of $\pi^{\pm}$, $\rm{K}^{\pm}$, $\rm{K}^{0}_{S}$, $\rm{K}^{*}(892)^{0}$, $\rm{p}$, $\phi(1020)$, $\Lambda$, $\Xi^{-}$, $\Omega^{-}$, and their antiparticles was measured in inelastic proton-proton (pp) collisions at a center-of-mass energy of $\sqrt{s}$ = 13 TeV at midrapidity ($|y|<0.5$) as a function of transverse momentum ($p_{\rm{T}}$) using the ALICE detector at the CERN LHC. Furthermore, the single-particle $p_{\rm{T}}$ distributions of $\rm{K}^{0}_{S}$, $\Lambda$, and $\overline{\Lambda}$ in inelastic pp collisions at $\sqrt{s}$ = 7 TeV are reported here for the first time. The $p_{\rm{T}}$ distributions are studied at midrapidity within the transverse momentum range $0\leq p_{\rm{T}}\leq20$ GeV/$c$, depending on the particle species. The $p_{\rm{T}}$ spectra, integrated yields, and particle yield ratios are discussed as a function of collision energy and compared with measurements at lower $\sqrt{s}$ and with results from various general-purpose QCD-inspired Monte Carlo models. A hardening of the spectra at high $p_{\rm{T}}$ with increasing collision energy is observed, which is similar for all particle species under study. The transverse mass and $x_{\rm{T}}\equiv2p_{\rm{T}}/\sqrt{s}$ scaling properties of hadron production are also studied. As the collision energy increases from $\sqrt{s}$ = 7 to 13 TeV, the yields of non- and single-strange hadrons normalized to the pion yields remain approximately constant as a function of $\sqrt{s}$, while ratios for multi-strange hadrons indicate enhancements. The $p_{\rm{T}}$-differential cross sections of $\pi^{\pm}$, $\rm{K}^{\pm}$ and $\rm{p}$ ($\overline{\rm{p}}$) are compared with next-to-leading order perturbative QCD calculations, which are found to overestimate the cross sections for $\pi^{\pm}$ and $\rm{p}$ ($\overline{\rm{p}}$) at high $p_{\rm{T}}$.

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Measurement of ${\rm D^0}$, ${\rm D^+}$, ${\rm D^{*+}}$ and ${{\rm D^+_s}}$ production in pp collisions at $\mathbf{\sqrt{{\textit s}}~=~5.02~TeV}$ with ALICE

The ALICE collaboration Acharya, Shreyasi ; Adamova, Dagmar ; Adhya, Souvik Priyam ; et al.
Eur.Phys.J.C 79 (2019) 388, 2019.
Inspire Record 1716440 DOI 10.17182/hepdata.89326

The measurements of the production of prompt ${\rm D^0}$, ${\rm D^+}$, ${\rm D^{*+}}$, and ${{\rm D^+_s}}$ mesons in proton--proton (pp) collisions at $\sqrt{s}=5.02$ TeV with the ALICE detector at the Large Hadron Collider (LHC) are reported. D mesons were reconstructed at mid-rapidity ($|y|<0.5$) via their hadronic decay channels ${\rm D}^0 \to {\rm K}^-\pi^+$, ${\rm D}^+\to {\rm K}^-\pi^+\pi^+$, ${\rm D}^{*+} \to {\rm D}^0 \pi^+ \to {\rm K}^- \pi^+ \pi^+$, ${\rm D^{+}_{s}\to \phi\pi^+\to K^{+} K^{-} \pi^{+}}$, and their charge conjugates. The production cross sections were measured in the transverse momentum interval $0<p_{\rm T}<36~\mathrm{GeV}/c$ for ${\rm D^0}$, $1<p_{\rm T}<36~\mathrm{GeV}/c$ for ${\rm D^+}$ and ${\rm D^{*+}}$, and in $2<p_{\rm T}<24~\mathrm{GeV}/c$ for ${{\rm D^+_s}}$ mesons. Thanks to the higher integrated luminosity, an analysis in finer $p_{\rm T}$ bins with respect to the previous measurements at $\sqrt{s}=7$ TeV was performed, allowing for a more detailed description of the cross-section $p_{\rm T}$ shape. The measured $p_{\rm T}$-differential production cross sections are compared to the results at $\sqrt{s}=7$ TeV and to four different perturbative QCD calculations. Its rapidity dependence is also tested combining the ALICE and LHCb measurements in pp collisions at $\sqrt{s}=5.02$ TeV. This measurement will allow for a more accurate determination of the nuclear modification factor in p-Pb and Pb-Pb collisions performed at the same nucleon-nucleon centre-of-mass energy.

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Measurement of beauty and charm production in pp collisions at $\sqrt{s}=5.02$ TeV via non-prompt and prompt D mesons

The ALICE collaboration Acharya, Shreyasi ; Adamova, Dagmar ; Adler, Alexander ; et al.
JHEP 05 (2021) 220, 2021.
Inspire Record 1848990 DOI 10.17182/hepdata.105047

The $p_\mathrm{T}$-differential production cross sections of prompt and non-prompt (produced in beauty-hadron decays) D mesons were measured by the ALICE experiment at midrapidity ($|y|<0.5$) in proton--proton collisions at $\sqrt{s}=5.02~\mathrm{TeV}$. The data sample used in the analysis corresponds to an integrated luminosity of $(19.3\pm0.4)~\mathrm{nb^{-1}}$. D mesons were reconstructed from their decays $\mathrm{D^0 \to K^-\pi^+}$, $\mathrm{D^+\to K^-\pi^+\pi^+}$, and $\mathrm{D_s^+\to \phi\pi^+\to K^-K^+\pi^+}$ and their charge conjugates. Compared to previous measurements in the same rapidity region, the cross sections of prompt $\mathrm{D^+}$ and $\mathrm{D_s^+}$ mesons have an extended $p_\mathrm{T}$ coverage and total uncertainties reduced by a factor ranging from 1.05 to 1.6, depending on $p_\mathrm{T}$, allowing for a more precise determination of their $p_\mathrm{T}$-integrated cross sections. The results are well described by perturbative QCD calculations. The fragmentation fraction of heavy quarks to strange mesons divided by the one to non-strange mesons, $f_\mathrm{s}/(f_\mathrm{u}+f_\mathrm{d})$, is compatible for charm and beauty quarks and with previous measurements at different centre-of-mass energies and collision systems. The $\mathrm{b\overline{b}}$ production cross section per rapidity unit at midrapidity, estimated from non-prompt D-meson measurements, is $\mathrm{d}\sigma_\mathrm{b\overline{b}}/\mathrm{d} y|_\mathrm{|y|<0.5} = 34.5 \pm 2.4 (\mathrm{stat.}) ^{+4.7}_{-2.9} (\mathrm{tot. syst.})~\mu\mathrm{b}$. It is compatible with previous measurements at the same centre-of-mass energy and with the cross section predicted by perturbative QCD calculations.

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Measurement of the production cross section of prompt $\Xi^0_{\rm c}$ baryons at midrapidity in pp collisions at $\sqrt{s}$ = 5.02 TeV

The ALICE collaboration Acharya, Shreyasi ; Adamova, Dagmar ; Adler, Alexander ; et al.
JHEP 10 (2021) 159, 2021.
Inspire Record 1863039 DOI 10.17182/hepdata.114189

The transverse momentum ($p_{\rm T}$) differential cross section of the charm-strange baryon $\Xi^0_{\rm c}$ is measured at midrapidity ($|y|<$ 0.5) via its semileptonic decay into ${\rm e^{+}}\Xi^{-}\nu_{\rm e}$ in pp collisions at $\sqrt{s}$ = 5.02 TeV with the ALICE detector at the LHC. The ratio of the $p_{\rm T}$-differential $\Xi^0_{\rm c}$-baryon and ${\rm D^0}$-meson production cross sections is also reported. The measurements are compared with simulations with different tunes of the PYTHIA 8 event generator, with predictions from a statistical hadronisation model (SHM) with a largely augmented set of charm-baryon states beyond the current lists of the Particle Data Group, and with models including hadronisation via quark coalescence. The $p_{\rm T}$-integrated cross section of prompt $\Xi^0_{\rm c}$-baryon production at midrapidity is also reported, which is used to calculate the baryon-to-meson ratio $\Xi^0_{\rm c}/{\rm D^0} = 0.20 \pm 0.04~{\rm (stat.)} ^{+0.08}_{-0.07}~{\rm (syst.)}$. These results provide an additional indication of a modification of the charm fragmentation from $\rm e^+e^-$ and $\rm e^{-}p$ collisions to pp collisions.

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$\rm \Lambda_{c}^{+}$ production and baryon-to-meson ratios in pp and p-Pb collisions at $\sqrt{s_\mathrm{NN}} = 5.02$ TeV at the LHC

The ALICE collaboration Acharya, Shreyasi ; Adamova, Dagmar ; Adler, Alexander ; et al.
Phys.Rev.Lett. 127 (2021) 202301, 2021.
Inspire Record 1829739 DOI 10.17182/hepdata.114213

The prompt production of the charm baryon $\rm \Lambda_{c}^{+}$ and the $\rm \Lambda_{c}^{+}/\mathrm {D^0}$ production ratios were measured at midrapidity with the ALICE detector in pp and p-Pb collisions at $\sqrt{s_\mathrm{NN}} = 5.02$TeV. These new measurements show a clear decrease of the $\rm \Lambda_{c}^{+}/\mathrm {D^0}$ ratio with increasing transverse momentum ($p_{\rm T}$) in both collision systems in the range $2<p_{\rm T}<12$ GeV/$c$, exhibiting similarities with the light-flavour baryon-to-meson ratios ${\rm p}/\pi$ and $\Lambda/\mathrm {K^0_S}$. At low $p_{\rm T}$, predictions that include additional colour-reconnection mechanisms beyond the leading-colour approximation; assume the existence of additional higher-mass charm-baryon states; or include hadronisation via coalescence can describe the data, while predictions driven by charm-quark fragmentation processes measured in $\mathrm {e^+e^-}$ and $\mathrm {e^-p}$ collisions significantly underestimate the data. The results presented in this letter provide significant evidence that the established assumption of universality (colliding-system independence) of parton-to-hadron fragmentation is not sufficient to describe charm-baryon production in hadronic collisions at LHC energies.

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Inclusive J/$\psi$ production at midrapidity in pp collisions at $\sqrt{s}~=~13$ TeV

The ALICE collaboration Acharya, Shreyasi ; Adamova, Dagmar ; Adler, Alexander ; et al.
Eur.Phys.J.C 81 (2021) 1121, 2021.
Inspire Record 1898832 DOI 10.17182/hepdata.115422

We report on the inclusive J/$\psi$ production cross section measured at the CERN Large Hadron Collider in proton-proton collisions at a centre-of-mass energy $\sqrt{s}~=~13$ TeV. The J/$\psi$ mesons are reconstructed in the $\rm e^{+} e^{-}$ decay channel and the measurements are performed at midrapidity ($|y|<0.9$) in the transverse-momentum interval $0< p_{\rm T} <40$ GeV/$c$, using a minimum bias data sample corresponding to an integrated luminosity $L_{\text{int}} = 32.2~\text{nb}^{-1}$ and an Electromagnetic Calorimeter triggered data sample with $L_{\text{int}} = 8.3~\mathrm{pb}^{-1}$. The $p_{\rm T}$-integrated J/$\psi$ production cross section at midrapidity, computed using the minimum bias data sample, is $\text{d}\sigma/\text{d}y|_{y=0} = 8.97\pm0.24~(\text{stat})\pm0.48~(\text{syst})\pm0.15~(\text{lumi})~\mu\text{b}$. An approximate logarithmic dependence with the collision energy is suggested by these results and available world data, in agreement with model predictions. The integrated and $p_{\rm T}$-differential measurements are compared with measurements in pp collisions at lower energies and with several recent phenomenological calculations based on the non-relativistic QCD and Color Evaporation models.

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