W$^\pm$-boson production in p$-$Pb collisions at $\sqrt{s_{NN}} = 8.16$ TeV and PbPb collisions at $\sqrt{s_{NN}} = 5.02$ TeV

The ALICE collaboration
CERN-EP-2022-076, 2022.
Inspire Record 2071184 DOI 10.17182/hepdata.133034

The production of the W$^\pm$ bosons measured in p$-$Pb collisions at a centre-of-mass energy per nucleon$-$nucleon collision $\sqrt{s_{NN}} = 8.16$ TeV and Pb$-$Pb collisions at $\sqrt{s_{NN}} = 5.02$ TeV with ALICE at the LHC is presented. The W$^\pm$ bosons are measured via their muonic decay channel, with the muon reconstructed in the pseudorapidity region $-4 < \eta^\mu_{\rm lab} < -2.5$ with transverse momentum $p_{\rm T}^\mu > 10$ GeV/$c$. While in Pb$-$Pb collisions the measurements are performed in the forward ($2.5 < y^\mu_{\rm cms} < 4$) rapidity region, in p$-$Pb collisions, where the centre-of-mass frame is boosted with respect to the laboratory frame, the measurements are performed in the backward ($-4.46 < y^\mu_{\rm cms} < -2.96$) and forward ($2.03 < y^\mu_{\rm cms} < 3.53$) rapidity regions. The W$^{-}$ and W$^{+}$ production cross sections, lepton-charge asymmetry, and nuclear modification factors are evaluated as a function of the muon rapidity. In order to study the production as a function of the p$-$Pb collision centrality, the production cross sections of the W$^{-}$ and W$^{+}$ bosons are combined and normalised to the average number of binary nucleon$-$nucleon collision $\langle N_\mathrm{coll} \rangle$. In Pb$-$Pb collisions, the same measurements are presented as a function of the collision centrality. Study of the binary scaling of the W$^\pm$-boson cross sections in p$-$Pb and Pb$-$Pb collisions is also reported. The results are compared with perturbative QCD (pQCD) calculations, with and without nuclear modifications of the Parton Distribution Functions (PDFs), as well as with available data at the LHC. Significant deviations from the theory expectations are found in the two collision systems, indicating that the measurements can provide additional constraints for the determination of nuclear PDF (nPDFs) and in particular of the light-quark distributions.

12 data tables

d$\sigma$ / d$y$ of muons from W decays in p-Pb, in full fiducial region

d$\sigma$ / d$y$ of muons from W decays in p-Pb, in rapidity bins

Lepton-charge asymmetry $A_{ch} = \frac{N_{\mu^+} - N_{\mu^-}}{N_{\mu^+} + N_{\mu^-}}$ in p-Pb

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Photoproduction of low-$p_{\rm T}$ J/$\psi$ from peripheral to central Pb$-$Pb collisions at 5.02 TeV

The ALICE collaboration
CERN-EP-2022-071, 2022.
Inspire Record 2071183 DOI 10.17182/hepdata.134024

An excess of J/$\psi$ yield at very low transverse momentum ($p_{\rm T} < 0.3$ GeV/$c$), originating from coherent photoproduction, is observed in peripheral and semicentral hadronic Pb$-$Pb collisions at a center-of-mass energy per nucleon pair of $\sqrt{s_{\rm NN}} = 5.02$ TeV. The measurement is performed with the ALICE detector via the dimuon decay channel at forward rapidity ($2.5<y<4$). The nuclear modification factor at very low $p_{\rm T}$ and the coherent photoproduction cross section are measured as a function of centrality down to the 10% most central collisions. These results extend the previous study at $\sqrt{s_{\rm NN}} = 2.76$ TeV, confirming the clear excess over hadronic production in the $p_{\rm T}$ range 0$-$0.3 GeV/$c$ and the centrality range 70$-$90%, and establishing an excess with a significance greater than 5$\sigma$ also in the 50$-$70% and 30$-$50% centrality ranges. The results are compared with earlier measurements at $\sqrt{s_{\rm NN}} = 2.76$ TeV and with different theoretical predictions aiming at describing how coherent photoproduction occurs in hadronic interactions with nuclear overlap.

5 data tables

J/$\psi$ nuclear modification factor as a function of $\langle N_{\rm part}\rangle$ measured in the rapidity range 2.5 < y < 4 for $p_{\rm T}$ < 0.3 GeV/c. The centrality-correlated uncertainty of 7.2% is not included.

J/$\psi$ nuclear modification factor as a function of $\langle N_{\rm part} \rangle$ measured in the rapidity range 2.5 < y < 4 for 0.3 < $p_{\rm T}$ < 1 GeV/c. The centrality-correlated uncertainty of 6.6% is not included.

J/$\psi$ nuclear modification factor as a function of $\langle N_{\rm part} \rangle$ measured in the rapidity range 2.5 < y < 4 for 1 < $p_{\rm T}$ < 2 GeV/c. The centrality-correlated uncertainty of 6.2% is not included.

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General balance functions of identified charged hadron pairs of (π,K,p) in Pb–Pb collisions at <math altimg="si1.svg"><msub><mrow><msqrt><mrow><mi>s</mi></mrow></msqrt></mrow><mrow><msub><mrow/><mrow><mi mathvariant="normal">NN</mi></mrow></msub></mrow></msub><mo linebreak="goodbreak" linebreakstyle="after">=</mo></math> 2.76 TeV

The ALICE collaboration Acharya, Shreyasi ; Adamova, Dagmar ; Adler, Alexander ; et al.
Phys.Lett.B 833 (2022) 137338, 2022.
Inspire Record 1943964 DOI 10.17182/hepdata.132486

First measurements of balance functions (BFs) of all combinations of identified charged hadron $(\pi,\rm K,\rm p)$ pairs in Pb$-$Pb collisions at $\sqrt{s_{\rm NN}} = 2.76$ TeV recorded by the ALICE detector are presented. The BF measurements are carried out as two-dimensional differential correlators versus the relative rapidity ($\Delta y$) and azimuthal angle ($\Delta\varphi$) of hadron pairs, and studied as a function of collision centrality. The $\Delta\varphi$ dependence of BFs is expected to be sensitive to the light quark diffusivity in the quark$-$gluon plasma. While the BF azimuthal widths of all pairs substantially decrease from peripheral to central collisions, the longitudinal widths exhibit mixed behaviors: BFs of $\pi\pi$ and cross-species pairs narrow significantly in more central collisions, whereas those of $\rm KK$ and $\rm pp$ are found to be independent of collision centrality. This dichotomy is qualitatively consistent with the presence of strong radial flow effects and the existence of two stages of quark production in relativistic heavy-ion collisions. Finally, the first measurements of the collision centrality evolution of BF integrals are presented, with the observation that charge balancing fractions are nearly independent of collision centrality in Pb$-$Pb collisions. Overall, the results presented provide new and challenging constraints for theoretical models of hadron production and transport in relativistic heavy-ion collisions.

24 data tables

Balance function $B^{\pi\pi}$ measured in semicentral Pb--Pb collisions at $\sqrt{s_{\rm NN}}=2.76\;\text{TeV}$ ($\pi,{\rm K}: 0.2 \leq p_{\rm T} \leq 2.0\;{\rm GeV}/c$; ${\rm p}: 0.5 \leq p_{\rm T} \leq 2.5\;{\rm GeV}/c$).

Balance function $B^{{\rm KK}}$ measured in semicentral Pb--Pb collisions at $\sqrt{s_{\rm NN}}=2.76\;\text{TeV}$ ($\pi,{\rm K}: 0.2 \leq p_{\rm T} \leq 2.0\;{\rm GeV}/c$; ${\rm p}: 0.5 \leq p_{\rm T} \leq 2.5\;{\rm GeV}/c$).

Balance function $B^{{\rm p\bar{p}}}$ measured in semicentral Pb--Pb collisions at $\sqrt{s_{\rm NN}}=2.76\;\text{TeV}$ ($\pi,{\rm K}: 0.2 \leq p_{\rm T} \leq 2.0\;{\rm GeV}/c$; ${\rm p}: 0.5 \leq p_{\rm T} \leq 2.5\;{\rm GeV}/c$).

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Charm-quark fragmentation fractions and production cross section at midrapidity in pp collisions at the LHC

The ALICE collaboration Acharya, Shreyasi ; Adamova, Dagmar ; Adler, Alexander ; et al.
Phys.Rev.D 105 (2022) L011103, 2022.
Inspire Record 1863128 DOI 10.17182/hepdata.127975

Recent $p_{\rm T}$-integrated cross section measurements of the ground-state charm mesons and baryons, D$^{\rm 0}$, D$^+$, D$_{\rm s}^{+}$, $\Lambda_{\rm c}^{+}$, and $\Xi_{\rm c}^0$, are used to evaluate the charm fragmentation fractions and production cross section per unit of rapidity at midrapidity ($|y|<0.5$), in pp collisions at $\sqrt{s} = 5.02$ TeV at the LHC. The latter is ${\rm d} \sigma^{\rm c \overline{c}}/{\rm d} y|_{|y| < 0.5}$ =1165 $\pm 44(\rm{stat})^{+134}_{-101}(\rm{syst})$$\mu b$. These measurements were obtained for the first time in hadronic collisions at the LHC including the charm baryon states, recently measured by ALICE at midrapidity. The charm fragmentation fractions differ significantly from the values measured in e$^+$e$^-$ and ep collisions, providing evidence of the dependence of the parton-to-hadron fragmentation fractions on the collision system, indicating that the assumption of their universality is not supported by the measured cross sections. An increase of a factor of about 3.3 for the fragmentation fraction for the $\Lambda_{\rm c}^{+}$ with a significance of $5\,\sigma$ between the values obtained in pp collisions and those obtained in e$^+$e$^-$ (ep) collisions is reported. The fragmentation fraction for the $\Xi_{\rm c}^0$ was obtained for the first time in any collision system. The measured fragmentation fractions were used to update the $\rm c \overline{c}$ cross sections per unit of rapidity at $|y|<0.5$ at $\sqrt{s} = 2.76$ and 7 TeV, which are about 40% higher than the previously published results. The data were compared with perturbative-QCD calculations and lie at the upper edge of the theoretical bands.

3 data tables

Ratio of prompt open-charm hadrons H$_\mathrm{c}$ and inclusive $\mathrm{J}/\psi$ mesons over D$^0$-meson production cross section in pp collisions at $\sqrt{s} = 5.02$ TeV.

Fragmentation fractions of charm quark to open-charm hadrons $f(\mathrm{c \rightarrow H_c})$ in pp collisions at $\sqrt{s} = 5.02$ TeV.

Production cross section of charm-anticharm quark pairs per unity of rapidity at midrapidity $\mathrm{d}\sigma^{\mathrm{c\overline{c}}}/\mathrm{d}y|_{|y| < 0.5}$ in pp collisions at $\sqrt{s} = 2.76$, $5.02$, and $7$ TeV.


Kaon–proton strong interaction at low relative momentum via femtoscopy in Pb–Pb collisions at the LHC

The ALICE collaboration Acharya, Shreyasi ; Adamova, Dagmar ; Adler, Alexander ; et al.
Phys.Lett.B 822 (2021) 136708, 2021.
Inspire Record 1863041 DOI 10.17182/hepdata.114016

In quantum scattering processes between two particles, aspects characterizing the strong and Coulomb forces can be observed in kinematic distributions of the particle pairs. The sensitivity to the interaction potential reaches a maximum at low relative momentum and vanishing distance between the two particles. Ultrarelativistic heavy-ion collisions at the LHC provide an abundant source of many hadron species and can be employed as a measurement method of scattering parameters that is complementary to scattering experiments. This study confirms that momentum correlations of particles produced in Pb-Pb collisions at the LHC provide an accurate measurement of kaon-proton scattering parameters at low relative momentum, allowing precise access to the $ {K}^{-} p\rightarrow {K}^{-} p$ process. This work also validates the femtoscopic measurement in ultrarelativistic heavy-ion collisions as an alternative to scattering experiments and a complementary tool to the study of exotic atoms with comparable precision. In this work, the first femtoscopic measurement of momentum correlations of ${K}^{-} p\ ({K}^{+}\overline{p})$ and ${K}^{+}p ({K}^{-}\overline{p})$ pairs in Pb-Pb collisions at centre-of-mass energy per nucleon pair of $\sqrt{s_{\rm NN}} = 5.02$ TeV registered by the ALICE experiment is reported. The components of the ${K}^{-} p$ complex scattering length are extracted and found to be $\Re f_0=-0.91\pm~{0.03}$(stat)$^{+0.17}_{-0.03}$(syst) and $\Im f_0 = 0.92\pm~{0.05}$(stat)$^{+0.12}_{-0.33}$(syst). The results are compared with chiral effective field theory predictions as well as with existing data from dedicated scattering and exotic kaonic atom experiments.

12 data tables

K p (opposite charge) correlation function for centrality 0-5% from Pb-Pb collisions at 5020 GeV

K p (same charge) correlation function for centrality 0-5% from Pb-Pb collisions at 5020 GeV

K p (opposite charge) correlation function for centrality 5-10% from Pb-Pb collisions at 5020 GeV

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Inclusive, prompt and non-prompt J/ψ production at midrapidity in p-Pb collisions at $ \sqrt{s_{\mathrm{NN}}} $ = 5.02 TeV

The ALICE collaboration
JHEP 06 (2022) 011, 2022.
Inspire Record 1862791 DOI 10.17182/hepdata.130237

A measurement of inclusive, prompt, and non-prompt ${\rm J}/\psi$ production in p$-$Pb collisions at a nucleon--nucleon centre-of-mass energy $\sqrt{s_{\mathrm{NN}}} = 5.02$ TeV is presented. The ${\rm J}/\psi$ mesons are reconstructed in the dielectron decay channel at midrapidity down to a transverse momentum $p_{\rm T} = 0$. The inclusive ${\rm J}/\psi$ nuclear modification factor $R_{\rm pPb}$ is calculated by comparing the results in p$-$Pb collisions to a measured proton$-$proton reference at the same centre-of-mass energy. Non-prompt ${\rm J}/\psi$ mesons, which originate from the decay of beauty hadrons, are separated from promptly produced ${\rm J}/\psi$ on a statistical basis for $p_{\rm T}$ larger than 1.0 GeV/$c$. These results are based on the data sample collected by the ALICE detector during the 2016 LHC p$-$Pb run, corresponding to an integrated luminosity ${\cal L}_{\rm int} = 292 \pm 11 \; {\rm \mu b}^{-1}$, which is six times larger than the previous publications. The total uncertainty on the $p_{\rm T}$-integrated inclusive ${\rm J}/\psi$ and non-prompt ${\rm J}/\psi$ cross section are reduced by a factor 1.7 and 2.2, respectively. The measured cross sections and $R_{\rm pPb}$ are compared with theoretical models that include various combinations of cold nuclear matter effects. From the non-prompt ${\rm J}/\psi$ production cross section, the ${\rm b\overline{b}}$ production cross section at midrapidity, $\mathrm{d}\sigma_{\rm b\overline{b}}/\mathrm{d}y$, and the total cross section extrapolated over full phase space, $\sigma_{\rm b\overline{b}}$, are derived.

12 data tables

Fraction of non-prompt $\rm{J}/\psi$ in pp collisions at $\sqrt{s}$ = 5.02 TeV for different $p_\mathrm{T}$ ranges, as determined with a procedure of interpolation from measurments at other energies. It is not a direct measurment.

Inclusive d$^2\sigma$/d$y$d$p_{\rm T}$ in bins of $p_{\mathrm{T}}^{J/\psi}$ for prompt J/$\psi$ in p--Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV.

Fraction of non-prompt J/$\psi$ in p--Pb collisions at $\sqrt{s_\mathrm{NN}}$ = 5.02 TeV for different $p_\mathrm{T}$ ranges.

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First measurement of coherent ρ0 photoproduction in ultra-peripheral Xe–Xe collisions at sNN=5.44 TeV

The ALICE collaboration Acharya, Shreyasi ; Adamova, Dagmar ; Adler, Alexander ; et al.
Phys.Lett.B 820 (2021) 136481, 2021.
Inspire Record 1839719 DOI 10.17182/hepdata.110661

The first measurement of the coherent photoproduction of $\rho^{0}$ vector mesons in ultra-peripheral Xe-Xe collisions at $\sqrt{s_{\mathrm{\rm NN}}}= 5.44$ TeV is presented. This result, together with previous HERA $\gamma$p data and $\gamma$-Pb measurements from ALICE, describes the atomic number ($A$) dependence of this process, which is particularly sensitive to nuclear shadowing effects and to the approach to the black-disc limit of QCD at a semi-hard scale. The cross section of the ${\rm Xe}+{\rm Xe} \to \rho^{0} + {\rm Xe}+{\rm Xe}$ process, measured at midrapidity through the decay channel $\rho^{0}\to\pi^+\pi^-$, is found to be ${\rm d}\sigma/{\rm d}y=131.5\pm 5.6 {\rm (stat.)} ^{+17.5}_{-16.9} {\rm (syst.)}$ mb. The ratio of the continuum to resonant contributions for the production of pion pairs is also measured. In addition, the fraction of events accompanied by electromagnetic dissociation of either one or both colliding nuclei is reported. The dependence on $A$ of cross section for the coherent $\rho^{0}$ photoproduction at a centre-of-mass energy per nucleon of the $\gamma A$ system of $W_{\gamma A,n}= 65$ GeV is found to be consistent with a power-law behaviour $\sigma (\gamma A\rightarrow \rho^{0} A) \propto A^{\alpha}$ with a slope $\alpha = 0.96 \pm 0.02 {\rm (syst.)}$. This slope signals important shadowing effects, but it is still far from the behaviour expected in the black-disc limit.

1 data table

Differential cross section as a function of rapidity for coherent RHO0 photoproduction in ultra-peripheral Xe-Xe collisions at ALICE.


J/$\psi$ elliptic and triangular flow in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV

The ALICE collaboration Acharya, Shreyasi ; Adamova, Dagmar ; Adler, Alexander ; et al.
JHEP 10 (2020) 141, 2020.
Inspire Record 1798507 DOI 10.17182/hepdata.99234

The inclusive J/$\psi$ elliptic ($v_2$) and triangular ($v_3$) flow coefficients measured at forward rapidity (2.5 $<y<$ 4) and the $v_2$ measured at midrapidity ($|y|<$ 0.9) in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV using the ALICE detector at the LHC are reported. The entire Pb-Pb data sample collected during Run 2 is employed, amounting to an integrated luminosity of 750 $\mu$b$^{-1}$ at forward rapidity and 93 $\mu$b$^{-1}$ at midrapidity. The results are obtained using the scalar product method and are reported as a function of transverse momentum $p_{\rm T}$ and collision centrality. At midrapidity, the J/$\psi$ $v_2$ is in agreement with the forward rapidity measurement. The centrality averaged results indicate a positive J/$\psi$ $v_3$ with a significance of more than 5$\sigma$ at forward rapidity in the $p_{\rm T}$ range $2<p_{\rm T}<5$ GeV/$c$. The forward rapidity $v_2$, $v_3$, and $v_3$/$v_2$ results at low and intermediate $p_{\rm T}$ ($p_{\rm T} \lesssim 8$ GeV/$c$) exhibit a mass hierarchy when compared to pions and D mesons, while converging into a species-independent curve at higher $p_{\rm T}$. At low and intermediate $p_{\rm T}$, the results could be interpreted in terms of a later thermalization of charm quarks compared to light quarks, while at high $p_{\rm T}$, path-length dependent effects seem to dominate. The J/$\psi$ $v_2$ measurements are further compared to a microscopic transport model calculation. Using a simplified extension of the quark scaling approach involving both light and charm quark flow components, it is shown that the D-meson $v_{\rm n}$ measurements can be described based on those for charged pions and J/$\psi$ flow.

19 data tables

Inclusive J/$\psi$ $v_2$ as a function of $p_{T}$ in the centrality interval 0$-$10.0 %

Inclusive J/$\psi$ $v_2$ as a function of $p_{T}$ in the centrality interval 10$-$30 %

Inclusive J/$\psi$ $v_2$ as a function of $p_{T}$ in the centrality interval 30$-$50 %

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Elliptic and triangular flow of (anti)deuterons in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV

The ALICE collaboration Acharya, Shreyasi ; Adamova, Dagmar ; Adler, Alexander ; et al.
Phys.Rev.C 102 (2020) 055203, 2020.
Inspire Record 1798556 DOI 10.17182/hepdata.99901

The measurements of the (anti)deuterons elliptic flow ($v_2$) and the first measurements of triangular flow ($v_3$) in Pb-Pb collisions at a center-of-mass energy per nucleon-nucleon collisions $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV are presented. A mass ordering at low transverse momentum ($p_{\rm T}$) is observed when comparing these measurements with those of other identified hadrons, as expected from relativistic hydrodynamics. The measured (anti)deuterons $v_2$ lies between the predictions from the simple coalescence and blast-wave models, which provide a good description of the data only for more peripheral and for more central collisions, respectively. The mass number scaling, which is violated for $v_2$, is approximately valid for the (anti)deuterons $v_3$. The measured $v_2$ and $v_3$ are also compared with the predictions from a coalescence approach with phase-space distributions of nucleons generated by iEBE-VISHNU with AMPT initial conditions coupled with UrQMD, and from a dynamical model based on relativistic hydrodynamics coupled to the hadronic afterburner SMASH. The model predictions are consistent with the data within the uncertainties in mid-central collisions, while a deviation is observed in central centrality intervals.

11 data tables

v2 as a function of pT for Pb-Pb collisions at \sqrt{s_NN} = 5.02 TeV and centrality 0-5%.

v2 as a function of pT for Pb-Pb collisions at \sqrt{s_NN} = 5.02 TeV and centrality 5-10%.

v2 as a function of pT for Pb-Pb collisions at \sqrt{s_NN} = 5.02 TeV and centrality 10-20%.

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Measurement of the low-energy antideuteron inelastic cross section

The ALICE collaboration Acharya, Shreyasi ; Adamova, Dagmar ; Adler, Alexander ; et al.
Phys.Rev.Lett. 125 (2020) 162001, 2020.
Inspire Record 1797442 DOI 10.17182/hepdata.96844

In this Letter, we report the first measurement of the inelastic cross section for antideuteron-nucleus interactions at low particle momenta, covering a range of $0.3 \leq p < 4$ GeV/$c$. The measurement is carried out using p-Pb collisions at a center-of-mass energy per nucleon-nucleon pair of $\sqrt{s_{\rm{NN}}}$ = 5.02 TeV, recorded with the ALICE detector at the CERN LHC and utilizing the detector material as an absorber for antideuterons and antiprotons. The extracted raw primary antiparticle-to-particle ratios are compared to the results from detailed ALICE simulations based on the GEANT4 toolkit for the propagation of antiparticles through the detector material. The analysis of the raw primary (anti)proton spectra serves as a benchmark for this study, since their hadronic interaction cross sections are well constrained experimentally. The first measurement of the inelastic cross section for antideuteron-nucleus interactions averaged over the ALICE detector material with atomic mass numbers $\langle A \rangle$ = 17.4 and 31.8 is obtained. The measured inelastic cross section points to a possible excess with respect to the Glauber model parameterization used in GEANT4 in the lowest momentum interval of $0.3 \leq p < 0.47$ GeV/$c$ up to a factor 2.1. This result is relevant for the understanding of antimatter propagation and the contributions to antinuclei production from cosmic ray interactions within the interstellar medium. In addition, the momentum range covered by this measurement is of particular importance to evaluate signal predictions for indirect dark-matter searches.

16 data tables

Raw primary antiproton-to-proton ratio as a function of the momentum p_primary.

Raw primary antiproton-to-proton ratio from Geant4-based MC simulations as a function of the momentum p_primary.

Raw primary antideuteron-to-deuteron ratio as a function of the momentum p_primary.

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