The production cross sections of $\mathrm {D^0}$, $\mathrm {D^+}$, and $\mathrm {\Lambda_{c}^{+}}$ hadrons originating from beauty-hadron decays (i.e. non-prompt) were measured for the first time at midrapidity in proton$-$lead (p$-$Pb) collisions at the center-of-mass energy per nucleon pair of $\sqrt{s_{\mathrm{NN}}} = 5.02$ TeV. Nuclear modification factors ($R_{\mathrm {pPb}}$) of non-prompt $\mathrm {D^0}$, $\mathrm {D^+}$, and $\mathrm {\Lambda_{c}^{+}}$ are calculated as a function of the transverse momentum ($p_{\mathrm T}$) to investigate the modification of the momentum spectra measured in p$-$Pb collisions with respect to those measured in proton$-$proton (pp) collisions at the same energy. The $R_{\mathrm {pPb}}$ measurements are compatible with unity and with the measurements in the prompt charm sector, and do not show a significant $p_{\mathrm T}$ dependence. The $p_{\mathrm T}$-integrated cross sections and $p_{\mathrm T}$-integrated $R_{\mathrm {pPb}}$ of non-prompt $\mathrm {D^0}$ and $\mathrm {D^+}$ mesons are also computed by extrapolating the visible cross sections down to $p_{\mathrm T}$ = 0. The non-prompt D-meson $R_{\mathrm {pPb}}$ integrated over $p_{\mathrm T}$ is compatible with unity and with model calculations implementing modification of the parton distribution functions of nucleons bound in nuclei with respect to free nucleons. The non-prompt $\mathrm {\Lambda_{c}^{+}/D^{0}}$ and $\mathrm{D^+/D^0}$ production ratios are computed to investigate hadronisation mechanisms of beauty quarks into mesons and baryons. The measured ratios as a function of $p_{\mathrm T}$ display a similar trend to that measured for charm hadrons in the same collision system.
Non-prompt $\mathrm{D}^0$ $p_\mathrm{{T}}$-differential production cross section $\mathrm{d}^2\sigma/\mathrm{d}p_\mathrm{T}\mathrm{d}y$ in p--Pb collisions at $\sqrt{{s_\mathrm{NN}}}=5.02~\mathrm{{TeV}}$ in the rapidity interval $-0.96 < y_{\mathrm{cms}} < 0.04$.
Non-prompt $\mathrm{D}^+$ $p_\mathrm{{T}}$-differential production cross section $\mathrm{d}^2\sigma/\mathrm{d}p_\mathrm{T}\mathrm{d}y$ in p--Pb collisions at $\sqrt{{s_\mathrm{NN}}}=5.02~\mathrm{{TeV}}$ in the rapidity interval $-0.96 < y_{\mathrm{cms}} < 0.04$.
Non-prompt $\Lambda_{c}^{+}$ $p_\mathrm{{T}}$-differential production cross section $\mathrm{d}^2\sigma/\mathrm{d}p_\mathrm{T}\mathrm{d}y$ in p--Pb collisions at $\sqrt{{s_\mathrm{NN}}}=5.02~\mathrm{{TeV}}$ in the rapidity interval $-0.96 < y_{\mathrm{cms}} < 0.04$.
The transverse momentum ($p_{\rm T}$) differential production cross section of the promptly produced charm-strange baryon $\Xi_{\rm c}^{0}$ (and its charge conjugate $\overline{\Xi_{\rm c}^{0}}$) is measured at midrapidity via its hadronic decay into ${\rm \pi^{+}}\Xi^{-}$ in p$-$Pb collisions at a centre-of-mass energy per nucleon$-$nucleon collision $\sqrt{s_{\mathrm{NN}}}~=~5.02$ TeV with the ALICE detector at the LHC. The $\Xi_{\rm c}^{0}$ nuclear modification factor ($R_{\rm pPb}$), calculated from the cross sections in pp and p$-$Pb collisions, is presented and compared with the $R_{\rm pPb}$ of $\Lambda_{\rm c}^{+}$ baryons. The ratios between the $p_{\rm T}$-differential production cross section of $\Xi_{\rm c}^{0}$ baryons and those of $\mathrm {D^0}$ mesons and $\Lambda_{\rm c}^{+}$ baryons are also reported and compared with results at forward and backward rapidity from the LHCb Collaboration. The measurements of the production cross section of prompt $\Xi^0_{\rm c}$ baryons are compared with a model based on perturbative QCD calculations of charm-quark production cross sections, which includes only cold nuclear matter effects in p$-$Pb collisions, and underestimates the measurement by a factor of about 50. This discrepancy is reduced when the data is compared with a model that includes string formation beyond leading-colour approximation or in which hadronisation is implemented via quark coalescence. The $p_{\rm T}$-integrated cross section of prompt $\Xi^0_{\rm c}$-baryon production at midrapidity extrapolated down to $p_{\rm T}$ = 0 is also reported. These measurements offer insights and constraints for theoretical calculations of the hadronisation process. Additionally, they provide inputs for the calculation of the charm production cross section in p$-$Pb collisions at midrapidity.
Prompt $\Xi_\mathrm{c}^0$ productions cross-section as a function of $p_\mathrm{T}$ in p–Pb collisions at $\sqrt{s_\mathrm{NN}} = 5.02$ TeV.
$\Xi_\mathrm{c}^0~R_\mathrm{pPb}$ as a function of $p_\mathrm{T}$ in p–Pb collisions at $\sqrt{s_\mathrm{NN}} = 5.02$ TeV.
$\Xi_\mathrm{c}^0/\mathrm{D}^0$ ratio as a function of $p_\mathrm{T}$ in p–Pb collisions at $\sqrt{s_\mathrm{NN}} = 5.02$ TeV.
This paper reports the observation of top-quark pair production in proton-lead collisions in the ATLAS experiment at the Large Hadron Collider. The measurement is performed using 165 nb$^{-1}$ of $p$+Pb data collected at $\sqrt{s_\mathrm{NN}}=8.16$ TeV in 2016. Events are categorised in two analysis channels, consisting of either events with exactly one lepton (electron or muon) and at least four jets, or events with two opposite-charge leptons and at least two jets. In both channels at least one $b$-tagged jet is also required. Top-quark pair production is observed with a significance over five standard deviations in each channel. The top-quark pair production cross-section is measured to be $\sigma_{t\bar{t}}= 58.1\pm 2.0\;\mathrm{(stat.)\;^{+4.8}_{-4.4} \;\mathrm{(syst.)}}\;\mathrm{nb}$, with a total uncertainty of 9%. In addition, the nuclear modification factor is measured to be $R_{p\mathrm{A}} = 1.090\pm0.039\;(\mathrm{stat.})\;^{+0.094}_{-0.087}\;(\mathrm{syst.})$. The measurements are found to be in good agreement with theory predictions involving nuclear parton distribution functions.
The figure shows the pre-fit distribution of events as a function of $H_{\mathrm{T}}^{\ell,j} = \sum_{\ell,j} p_{T}^{\ell,j}$, scalar sum of $p_T$ for all jets and leptons in the $\ell+$jets channel, in proton-lead (p+Pb) collisions at a center-of-mass energy of $\sqrt{s_{\mathrm{NN}}} = 8.16$ TeV, with an integrated luminosity of 165 nb$^{-1}$. The data correspond to the $1\ell 1b$ $e$+jets channel in a pre-fit configuration. The stacked histograms represent different processes contributing to the event yield, including top quark pair production ($t\bar{t}$), single top, $W$ boson production with $b$, $c$, and light quarks, $Z$ boson production with $b$, $c$, and light quarks, diboson, and fake lepton backgrounds.
The figure shows the post-fit distribution of events as a function of $H_{\mathrm{T}}^{\ell,j} = \sum_{\ell,j} p_{T}^{\ell,j}$, scalar sum of $p_T$ for all jets and leptons in the $\ell+$jets channel, in proton-lead (p+Pb) collisions at a center-of-mass energy of $\sqrt{s_{\mathrm{NN}}} = 8.16$ TeV, with an integrated luminosity of 165 nb$^{-1}$. The data correspond to the $1\ell 1b$ $e$+jets channel in a pre-fit configuration. The stacked histograms represent different processes contributing to the event yield, including top quark pair production ($t\bar{t}$), single top, $W$ boson production with $b$, $c$, and light quarks, $Z$ boson production with $b$, $c$, and light quarks, diboson, and fake lepton backgrounds.
The figure shows the pre-fit distribution of events as a function of $H_{\mathrm{T}}^{\ell,j} = \sum_{\ell,j} p_{T}^{\ell,j}$, scalar sum of $p_T$ for all jets and leptons in the $\ell+$jets channel, in proton-lead (p+Pb) collisions at a center-of-mass energy of $\sqrt{s_{\mathrm{NN}}} = 8.16$ TeV, with an integrated luminosity of 165 nb$^{-1}$. The data correspond to the $1\ell 1b$ $\mu$+jets channel in a pre-fit configuration. The stacked histograms represent different processes contributing to the event yield, including top quark pair production ($t\bar{t}$), single top, $W$ boson production with $b$, $c$, and light quarks, $Z$ boson production with $b$, $c$, and light quarks, diboson, and fake lepton backgrounds.
The production cross-sections of $J/\psi$ mesons in proton-proton collisions at a centre-of-mass energy of $\sqrt{s}=5$ TeV are measured using a data sample corresponding to an integrated luminosity of $9.13\pm0.18~\text{pb}^{-1}$, collected by the LHCb experiment. The cross-sections are measured differentially as a function of transverse momentum, $p_{\text{T}}$, and rapidity, $y$, and separately for $J/\psi$ mesons produced promptly and from beauty hadron decays (nonprompt). With the assumption of unpolarised $J/\psi$ mesons, the production cross-sections integrated over the kinematic range $0<p_{\text{T}}<20~\text{GeV}/c$ and $2.0<y<4.5$ are $8.154\pm0.010\pm0.283~\mu\text{b}$ for prompt $J/\psi$ mesons and $0.820\pm0.003\pm0.034~\mu\text{b}$ for nonprompt $J/\psi$ mesons, where the first uncertainties are statistical and the second systematic. These cross-sections are compared with those at $\sqrt{s}=8$ TeV and $13$ TeV, and are used to update the measurement of the nuclear modification factor in proton-lead collisions for $J/\psi$ mesons at a centre-of-mass energy per nucleon pair of $\sqrt{s_{\text{NN}}}=5$ TeV. The results are compared with theoretical predictions.
Double-differential production cross-sections for prompt $J/\psi$ mesons in ($p_\text{T},y$) intervals. The first uncertainties are statistical, the second are correlated systematic uncertainties shared between intervals, the third are uncorrelated systematic uncertainties, and the last are correlated between $p_\text{T}$ intervals and uncorrelated between $y$ intervals.
Double-differential production cross-sections for nonprompt $J/\psi$ mesons in ($p_\text{T},y$) intervals. The first uncertainties are statistical, the second are correlated systematic uncertainties shared between intervals, the third are uncorrelated systematic uncertainties, and the last are correlated between $p_\text{T}$ intervals and uncorrelated between $y$ intervals.
Single-differential production cross-sections for prompt $J/\psi$ mesons as a function of $p_\text{T}$. The first uncertainties are statistical, the second are correlated systematic uncertainties shared between intervals, and the last are uncorrelated systematic uncertainties.
The production of prompt charged particles in proton-lead collisions and in proton-proton collisions at the nucleon-nucleon centre-of-mass energy ${\sqrt{s_{\scriptscriptstyle\mathrm{NN}}}=5\,\mathrm{TeV}}$ is studied at LHCb as a function of pseudorapidity ($\eta$) and transverse momentum ($p_{\mathrm{T}}$) with respect to the proton beam direction. The nuclear modification factor for charged particles is determined as a function of $\eta$ between ${-4.8<\eta<-2.5}$ (backward region) and ${2.0<\eta<4.8}$ (forward region), and $p_{\mathrm{T}}$ between ${0.2<p_{\mathrm{T}}<8.0\,\mathrm{GeV}/c}$. The results show a suppression of charged particle production in proton-lead collisions relative to proton-proton collisions in the forward region and an enhancement in the backward region for $p_{\mathrm{T}}$ larger than $1.5\,\mathrm{GeV}/c$. This measurement constrains nuclear PDFs and saturation models at previously unexplored values of the parton momentum fraction down to $10^{-6}$.
Double-differential production cross-section for prompt charged particles in pp collisions at 5TeV with respect to pseudorapidity and transverse momentum. First uncertainty is statistical, the second is systematic and the third is from the luminosity. Luminosity uncertainty is fully correlated among the different kinematic ranges.
Double-differential production cross-section for prompt charged particles in pPb collisions at 5TeV with respect to pseudorapidity and transverse momentum in the forward region. The pseudorapidity is expressed in the nucleon-nucleon center-of-mass system. First uncertainty is statistical, the second is systematic and the third is from the luminosity. Luminosity uncertainty is fully correlated among the different kinematic ranges.
Double-differential production cross-section for prompt charged particles in pPb collisions at 5TeV with respect to pseudorapidity and transverse momentum in the backward region. The pseudorapidity is expressed in the nucleon-nucleon center-of-mass system. First uncertainty is statistical, the second is systematic and the third is from the luminosity. Luminosity uncertainty is fully correlated among the different kinematic ranges.
Inclusive $\psi$(2S) production is measured in p-Pb collisions at the centre-of-mass energy per nucleon-nucleon pair $\sqrt{s_{\rm{NN}}}=8.16$ TeV, using the ALICE detector at the CERN LHC. The production of $\psi$(2S) is studied at forward ($2.03 < y_{\rm cms} < 3.53$) and backward ($-4.46 < y_{\rm cms} < -2.96$) centre-of-mass rapidity and for transverse momentum $p_{\rm{T}}$ $<$ 12 GeV/$c$ via the decay to muon pairs. In this paper, we report the integrated as well as the $y_{\rm cms}$- and $p_{\rm T}$-differential inclusive production cross sections. Nuclear effects on $\psi$(2S) production are studied via the determination of the nuclear modification factor that shows a strong suppression at both forward and backward centre-of-mass rapidities. Comparisons with corresponding results for inclusive J/$\psi$ show a similar suppression for the two states at forward rapidity (p-going direction), but a stronger suppression for $\psi$(2S) at backward rapidity (Pb-going direction). As a function of $p_{\rm T}$, no clear dependence of the nuclear modification factor is found. The relative size of nuclear effects on $\psi$(2S) production compared to J/$\psi$ is also studied via the double ratio of production cross sections $[\sigma_{\psi(2S)}/\sigma_{\rm{J/}\psi}]_{\rm pPb}/[\sigma_{\psi(2S)}/\sigma_{\rm{J/}\psi}]_{\rm pp}$ between p-Pb and pp collisions. The results are compared with theoretical models that include various effects related to the initial and final state of the collision system and also with previous measurements at $\sqrt{s_{\rm{NN}}}$ = 5.02 TeV.
Inclusive $\psi(2{\rm S})$ differential cross section times branching ratio as a function of $y_{\rm cms}$, in p--Pb collisions at $\sqrt{s_{\rm NN}}$ = 8.16 TeV. The first uncertainty is statistical, the second is the uncorrelated systematic, while the third one is a correlated systematic uncertainty.
Inclusive $\psi(2{\rm S})$ differential cross section times branching ratio as a function of $p_{\rm T}$, at forward rapidity at $\sqrt{s_{\rm NN}}$ = 8.16 TeV .The first uncertainty is statistical, the second is the uncorrelated systematic, while the third one is a correlated systematic uncertainty.
Inclusive $\psi(2{\rm S})$ differential cross section times branching ratio as a function of $p_{\rm T}$, at backward rapidity at $\sqrt{s_{\rm NN}}$ = 8.16 TeV .The first uncertainty is statistical, the second is the uncorrelated systematic, while the third one is a correlated systematic uncertainty.
$\Upsilon$ 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.
$\Upsilon$(1S) differential cross section as a function of $y_{\rm cms}$, in p--Pb collisions at $\sqrt{s_{\rm NN}}$ = 8.16 TeV. The first uncertainty is statistical, while the second is the systematic.
$\Upsilon$(2S) differential cross section times as a function of $y_{\rm cms}$, in p--Pb collisions at $\sqrt{s_{\rm NN}}$ = 8.16 TeV. The first uncertainty is statistical, while the second is the systematic.
$\Upsilon$(3S) differential cross section as a function of $y_{\rm cms}$, in p--Pb collisions at $\sqrt{s_{\rm NN}}$ = 8.16 TeV. The first uncertainty is statistical, while the second is the systematic.
A measurement of beauty hadron production at mid-rapidity in proton-lead collisions at a nucleon-nucleon centre-of-mass energy $\sqrt{s_{\rm NN}}=5.02$ TeV is presented. The semi-inclusive decay channel of beauty hadrons into J/$\psi$ is considered, where the J/$\psi$ mesons are reconstructed in the dielectron decay channel at mid-rapidity down to transverse momenta of 1.3 GeV/$c$. The ${\rm {b\overline{b}}}$ production cross section at mid-rapidity, ${\rm d}\sigma_{\rm {b\overline{b}}}/{\rm d} y$, and the total cross section extrapolated over full phase space, $\sigma_{\rm {b\overline{b}}}$, are obtained. This measurement is combined with results on inclusive J/$\psi$ production to determine the prompt J/$\psi$ cross sections. The results in p-Pb collisions are then scaled to expectations from pp collisions at the same centre-of-mass energy to derive the nuclear modification factor $R_{\rm pPb}$, and compared to models to study possible nuclear modifications of the production induced by cold nuclear matter effects. $R_{\rm pPb}$ is found to be smaller than unity at low $p_{\rm T}$ for both J/$\psi$ coming from beauty hadron decays and prompt J/$\psi$.
Fraction of non-prompt J/$\psi$ in pp collisions at $\sqrt{s_{NN}}$ = 5.02 TeV for different $p_{\rm T}$ ranges, as determined with a procedure of interpolation from measurments at other energies. It is not a direct measurment.
Fraction of non-prompt J/$\psi$ in pPb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV for different $p_{\rm T}$ ranges.
Fraction of non-prompt J/$\psi$ in pPb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV for different $p_{\rm T}$ ranges.
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.
Prompt $\Lambda_{\rm {c}}^{+}$ baryon $p_{\rm {T}}$-differential cross section (average among different decay modes and analyses) in pp collisions at $\sqrt{s} = 7$ TeV in the rapidity interval $|y|<0.5$.
Prompt $\Lambda_{\rm {c}}^{+}$ baryon $p_{\rm {T}}$-differential cross section (average among different decay modes and analyses) in p-Pb collisions at $\sqrt{s_{\rm {NN}}} = 5.02$ TeV in the rapidity interval $-0.96 \lt y \lt 0.04$.
The $\Lambda_{\rm {c}}^{+}$/${\rm D}^{0}$ ratio measured in pp collisions at $\sqrt{s} = 7$ TeV in the rapidity interval $|y|<0.5$ as a function of $p_{\rm {T}}$.
The spectra of charged particles produced within the pseudorapidity window abs(eta) < 1 at sqrt(s[NN]) = 5.02 TeV are measured using 404 inverse microbarns of PbPb and 27.4 inverse picobarns of pp data collected by the CMS detector at the LHC in 2015. The spectra are presented over the transverse momentum ranges spanning 0.5 < pt < 400 GeV in pp and 0.7 < pt < 400 GeV in PbPb collisions. The corresponding nuclear modification factor, R[AA], is measured in bins of collision centrality. The R[AA] in the 5% most central collisions shows a maximal suppression by a factor of 7-8 in the pt region of 6-9 GeV. This dip is followed by an increase, which continues up to the highest pt measured, and approaches unity in the vicinity of pt = 200 GeV. The R[AA] is compared to theoretical predictions and earlier experimental results at lower collision energies. The newly measured pp spectrum is combined with the pPb spectrum previously published by the CMS Collaboration to construct the pPb nuclear modification factor, R[pA], up to 120 GeV. For pt > 20 GeV, R[pA] exhibits weak momentum dependence and shows a moderate enhancement above unity.
Charged-particle per-event yields measured in 0-5% PbPb centrality class.
Charged-particle per-event yields measured in 5-10% PbPb centrality class.
Charged-particle per-event yields measured in 10-30% PbPb centrality class.
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