Charmed Hadron Production Research Articles

Probing Open Charm Hadron Production with the ALICE-3 Detector at the High-Luminosity Large Hadron Collider

Probing Open Charm Hadron Production with the ALICE-3 Detector at the High-Luminosity Large Hadron Collider

Open charm production cross section from combined LHC experiments in pp collisions at s=5.02\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\sqrt{s} = 5.02$$\\end{document} TeV

Open charm production in proton–proton collisions represents an important tool to investigate some of the most fundamental aspects of quantum chromodynamics, from the partonic mechanisms of heavy-quark production to the process of heavy-quark hadronisation. Over the last decade, the measurement of the production cross sections of charm mesons and baryons in proton–proton (pp) collisions was at the centre of a wide experimental effort at the Large Hadron Collider. Thanks to the complementarity of the different experiments, the production of charm hadrons was measured over a wide transverse momentum region and in different rapidity ranges. In this paper, the measurements of the charm hadrons D0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$D^{0}$$\\end{document}, D∗+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$D^{*+}$$\\end{document}, D+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$D^{+}$$\\end{document}, Ds+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$D^{+}_{s}$$\\end{document}, Λc+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Lambda _{c}^{+}$$\\end{document} and Ξc0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Xi _{c}^{0}$$\\end{document} performed by the ALICE, CMS and LHCb collaborations in pp collisions at the centre-of-mass energy s=5.02\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\sqrt{s}=5.02$$\\end{document} TeV are combined to determine the total charm quark production cross section σcc¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\sigma _{c\\bar{c}}$$\\end{document} in a novel data-driven approach. The resulting total cc¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$c\\overline{c}$$\\end{document} cross section is σcc¯(pp,5.02TeV)=8.34±0.22(stat.)-0.37+0.37(syst.)-0.46+0.36(extr.)-0+0.68(Ωc)mb.\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\begin{aligned} \\begin{aligned} \\sigma _{c\\overline{c}} ({\ extrm{pp}},5.02\\,{\ extrm{TeV}}) ={}&8.34 \\pm 0.22\\mathrm { (stat.) } {}^{+0.37}_{-0.37} \\mathrm { (syst.) } {}^{+0.36}_{-0.46} \\mathrm { (extr.) } {}^{+0.68}_{-0} (\\Omega _c) \\,{\ ext {mb}}. \\end{aligned} \\end{aligned}$$\\end{document}The measured charm hadron distributions and corresponding cross sections are compared with the most recent theoretical calculations.

Production of Strange and Charm Hadrons in Pb+Pb Collisions at sNN = 5.02 TeV

Using a quark combination model with the equal-velocity combination approximation, we study the production of hadrons with strangeness and charm flavor quantum numbers in Pb+Pb collisions at sNN= 5.02 TeV. We present analytical expressions and numerical results for these hadrons’ transverse momentum spectra and yield ratios. Our numerical results agree well with the experimental data available. The features of strange and charm hadron production in the quark–gluon plasma at the early stage of heavy ion collisions are also discussed.

Coalescence plus fragmentation approach for the hadronization mechanism of heavy hadrons from AA to pp collisions

One of the present challenge for the theoretical understanding of heavy-quark hadronization is represented by the description of the measurements of heavy hadron production in pp, pA and AA collisions from RHIC to top LHC energies. The Λc/D0 ratio observed in AA collisions has a value of the order of the unity, and experimental measurements in pp collisions at both √S = 5.02 TeV and √S = 13 TeV have shown ratios for charm baryons Λc,Ξc0 and Ωc0 respect to D0 meson larger than that measured and expected in e+e−, ep collisions. We present an hadronization mechanism based on the coalescence and fragmentation processes, and the results obtained in AA collisions for D0 and Λc. related baryon to meson ratios at RHIC and LHC. We present moreover results obtained for the charmed hadron production in pp collisions at LHC energies assuming the formation of an hot QCD matter at finite temperature.We calculate the heavy baryon/meson ratio and the pT spectra of charmed hadrons D0. Λc0 and the recently measured Ξc baryon, finding an enhancement in comparison with the ratio observed for e+e−, ep collisions; with this approach we also predict a significant production of Qc.

Measurements of charm production in pp collisions with ALICE

The production of charm-hadrons at midrapidity in pp collisions at \sqrt{s}s = 5.02 and 13 TeV was recently measured by the ALICE Collaboration. The results show that the baryon-to-meson yield ratios differ from predictions where the hadronization has been tuned to measurements obtained in e^{+}e^{-}e+e− and ep collisions for different charm-baryon species. These observations suggest that the charm fragmentation fractions are not universal and that the baryon-to-meson ratio depends on the collision systems. The results are compared to the predictions from Monte Carlo event generators and theoretical calculations.

Charm-baryon enhancement and charm fragmentation fractions in small systems measured with ALICE

Recent measurements of charm-baryon production at midrapidity by the ALICE collaboration show baryon-to-meson yield ratios significantly higher than those measured in e+e− collisions, suggesting that the charm fragmentations are not universal across different collisions systems. Thus, measurements of charm-baryon production are crucial to study the charm quark hadronisation in proton–proton (pp) collisions. In proton–lead (p–Pb) collisions, the measurements of charm baryons provide important information about cold nuclear matter effects and help to understand how the possible presence of collective effects could modify the production of heavy-flavour hadrons. In this contribution, the most recent results on open charm-hadron production in pp and p–Pb collisions measured by ALICE are discussed.

Charm-baryon enhancement and charm fragmentation fractions in small systems measured with ALICE

Recent measurements of charm-baryon production at midrapidity by the ALICE collaboration show baryon-to-meson yield ratios significantly higher than those measured in e+e− collisions, suggesting that the charm fragmentations are not universal across different collisions systems. Thus, measurements of charm-baryon production are crucial to study the charm quark hadronisation in proton–proton (pp) collisions. In proton–lead (p–Pb) collisions, the measurements of charm baryons provide important information about cold nuclear matter effects and help to understand how the possible presence of collective effects could modify the production of heavy-flavour hadrons. In this contribution, the most recent results on open charm-hadron production in pp and p–Pb collisions measured by ALICE are discussed.

Constraints on gluon distribution functions in the nucleon and nucleus from open charm hadron production at the Electron-Ion Collider

The Electron-Ion Collider (EIC) at Brookhaven National Laboratory will be a precision Quantum Chromodynamics machine that will enable a vast physics program with electron+proton/ion collisions across a broad center-of-mass range. Measurements of hard probes such as heavy flavor in deep inelastic scatterings will be an essential component to the EIC physics program and are one of the detector R\&D driving aspects. In this paper we study the projected statistical precision of open charm hadron production through exclusive hadronic channel reconstruction with a silicon detector concept currently being developed using a PYTHIA-based simulation. We further study the impact of possible intrinsic charm in the proton on projected data, and estimate the constraint on the nuclear gluon parton distribution function (PDF) from the charm structure functions $F_{2}^{c\overline{c}}$ in $e$+Au collisions using a Bayesian PDF re-weighting technique. Our studies show the EIC will be capable delivering an unprecedented measurement of charm hadron production across a broad kinematic region and will provide strong constraints to both intrinsic charm and nuclear gluon PDFs.

Heavy-quark opportunities and challenges at FCC-ee

The abundant production of beauty and charm hadrons in the 5 times 10^{12}Z^0 decays expected at FCC-ee offers outstanding opportunities in flavour physics that in general exceed those available at Belle II and are complementary to the heavy-flavour programme of the LHC. A wide range of measurements will be possible in heavy-flavour spectroscopy, rare decays of heavy-flavoured particles and C!P-violation studies, which will benefit from the low-background experimental environment, the high Lorentz boost and the availability of the full spectrum of hadron species. This essay first surveys the important questions in heavy-flavour physics and assesses the likely theoretical and experimental landscape at the turn-on of FCC-ee. From this certain, measurements are identified where the impact of FCC-ee will be particularly important. A full exploitation of the heavy-flavour potential of FCC-ee places specific constraints and challenges on detector design, which in some cases are in tension with those imposed by the other physics goals of the facility. These requirements and conflicts are discussed.

Study on open charm hadron production and angular correlation in high-energy nuclear collisions

We study the production and angular correlation of charm hadrons in hot and dense matter produced in high-energy nuclear–nuclear collisions within a multiphase transport model (AMPT). By triggering additional charm–anticharm quark pair production in the AMPT, the model describes the $$D^0$$ nuclear modification factor in the low and intermediate $$p_{{\rm T}}$$ regions in Au + Au collisions at $$ \sqrt{s_{{\rm NN}}}=200$$ GeV reasonably well. Further exploration of the $$D^0$$ pair azimuthal angular correlation for different centralities shows clear evolution from low-multiplicity to high-multiplicity events, which is associated with the number of charm quark interactions with medium partons during AMPT transport.

Charm-hadron production in pp and AA collisions

Recent measurements of various charm-hadron ratios in pp, p-Pb and Pb-Pb collisions at the LHC have posed challenges to the theoretical understanding of heavy-quark hadronization. The Λc/D0 ratio in pp and p-Pb collisions shows larger values than those found in e+e− and ep collisions and predicted by Monte-Carlo event generators based on string fragmentation, at both low and intermediate transverse momenta (pT). In AA collisions, the Ds/D ratio is significantly enhanced over its values in pp, while the Λc/D0 data indicates a further enhancement at intermediate pT. Here, we report on our recent developments for a comprehensive description of the charm hadrochemistry and transport in pp and AA collisions. For pp collisions we find that the discrepancy between the Λc/D0 data and model predictions is much reduced by using a statistical hadronization model augmented by a large set of “missing” states in the charm-baryon spectrum, contributing to the Λc via decay feeddown. For AA collisions, we develop a 4-momentum conserving resonance recombination model for charm-baryon formation implemented via event-by-event simulations that account for space-momentum correlations (SMCs) in transported charm- and thermal light-quark distributions. The SMCs, together with the augmented charm-baryon states, are found to play an important role in describing the baryon-to-meson enhancement at intermediate momenta. We emphasize the importance of satisfying the correct (relative) chemical equilibrium limit when computing the charm hadrochemistry and its momentum dependence with coalescence models.

Sequential hadronization in heavy ion collisions

Heavy flavor supplies a chance to constrain and improve the hadronization mechanism. We have established a sequential coalescence model with charm conservation and applied it to the charmed hadron production in heavy ion collisions. The charm conservation enhances the earlier hadron production and suppresses the later production. This relative enhancement (suppression) changes significantly the ratios between charmed hadrons in heavy ion collisions.

Latest results on [formula omitted] and D production in pp and Pb-Pb collisions at [formula omitted] with ALICE at the LHC

The measurement of heavy-flavour production is a powerful tool to study the medium formed in high-energy heavy-ion collisions. Produced in hard scattering processes on a timescale shorter than the formation time of the Quark Gluon Plasma (QGP), they experience the whole evolution of the medium interacting with its constituents. The measurement of charm-hadron production allows testing the mechanisms of in-medium parton energy loss. Moreover, the study of charm-baryon production in heavy-ion collisions, and in particular the baryon-to-meson ratio, provides unique information on hadronisation mechanisms, constraining the role of coalescence. In this contribution, the ALICE results on open charmed meson and baryon production in large and small systems will be presented with a focus on the recent measurements of Λc+/D0 and Ds+/D0 ratios in central and peripheral Pb–Pb collisions and on the new results obtained for the same ratios in proton-proton collisions as a function of the charged particle multiplicity. The prospects for the Ξc0 analysis will also be discussed.

Charmed hadron chemistry in relativistic heavy-ion collisions

We develop for charmed hadron production in relativistic heavy-ion collisions a comprehensive coalescence model that includes an extensive set of s and p-wave hadronic states as well as the strict energy-momentum conservation, which ensures the boost invariance of the coalescence probability and the thermal limit of the produced hadron spectrum. By combining our hadronization scheme with an advanced Langevin-hydrodynamics model that incorporates both elastic and inelastic energy loss of heavy quarks inside the dynamical quark-gluon plasma, we obtain a successful description of the pT-integrated and differential Λc/D0 and Ds/D0 ratios measured at RHIC and the LHC. We find that including the effect of radial flow of the medium is essential for describing the enhanced Λc/D0 ratio observed in relativistic heavy-ion collisions. We also find that the puzzling larger Λc/D0 ratio observed in Au+Au collisions at RHIC than in Pb+Pb collisions at the LHC is due to the interplay between the effects of the QGP radial flow and the charm quark transverse momentum spectrum at hadronization. Our study further suggests that charmed hadrons have larger sizes in medium than in vacuum.

Charmed hadron production in an improved quark coalescence model

We study the production of charmed hadrons $D^{0}$ and $\Lambda_c^+$ in relativistic heavy-ion collisions using an improved quark coalescence model. In particular, we extend the usual coalescence model by letting a produced hadron to have the same velocity as the center-of-mass velocity of coalesced constituent quarks during hadronization to take into account the effect of collective flow in produced quark-gluon plasma. This results in a shift of charmed resonances of higher masses to larger transverse momenta ($p_T^{}$). Requiring all charm quarks of very low $p_T^{}$ to be converted to hadrons via coalescence and letting charm quarks not undergoing coalescence to hadronize by independent fragmentation, we obtain a good description of the measured yield ratio $\Lambda_c^+/D^0$ as a function of $p_T^{}$ in $\text{Au} + \text{Au}$ collisions at $\sqrt{s_{NN}}^{}=200$~GeV by the STAR Collaboration at the Relativistic Heavy Ion Collider.

NA61/SHINE experiment at CERN SPS: Recent results, current status and perspectives

The NA61/SHINE experiment at the CERN SPS studies hadron production properties in hadron-nucleus and nucleus-nucleus collisions. Recent results from p+p, Be+Be and Ar+Sc interactions provide new data on the system size and energy dependence of hadron multiplicities, spectra and fluctuations. In particular, they indicate a threshold for formation of large clusters interpreted as the onset of fireball. A scaled-factorial-moment analysis of the proton density fluctuations in Ar+Sc collisions at 150A GeV/c shows an intermittency signal, which may be a first trace of critical behavior. The main objective of the future NA61/SHINE program is to obtain high-precision data on charm hadron production. This new program is planed to start in 2021, after the Long Shutdown 2 of the CERN accelerators. It requires significant upgrades of the NA61/SHINE detectors in order to increase the data readout rate tenfold.

Rescattering effects in antiproton-induced exclusive J/$ \psi$ and $ \psi^{{\prime}}_{}$ production on the deuteron

On the basis of the generalized eikonal approximation we study the exclusive reactions $\bar p d \to J/\psi\, n$ and $\bar p d \to \psi^\prime\, n$ in vicinity of the thresholds for charmonium production on a free proton target. It is shown that the rescattering of the incoming antiproton and outgoing charmonium on the spectator neutron leads to a depletion of the charmonium production at low- and to an enhancement at high transverse momenta. This is in qualitative agreement with previous studies of hard proton knockout in proton-deuteron collisions. We analyze different physical sources of uncertainty which may influence the extraction of the total charmonium-neutron cross section. The color transparency effect for the incoming $\bar p$ largely compensates the influence of charmonium rescattering both at low and high transverse momenta. Different choices of the deuteron wave function lead to significant uncertainties at high transverse momenta. As an outcome of the calculations of charmonium production, we also provide predictions on the production of open charm hadrons due to the dissociation of the charmonium on the neutron. It is shown that the open charm production cross section is proportional to the total charmonium-nucleon cross section and quite stable with respect to the variation of other parameters of the model. We thus suggest that open charm channels are most suited for future studies of charmonium-nucleon interactions at PANDA with a deuteron target.

Charm-baryon production in proton-proton collisions

Recent measurements of charm-hadron production in proton-proton collisions at the LHC have found a surprisingly large baryon to meson ratio. We propose that this observation can be explained by the statistical hadronization model (SHM), by employing a largely augmented set of charm-baryon states beyond the current listings of the particle data group. We estimate the additional states using guidance from the relativistic quark model and from lattice QCD. Using charm- and strange-quark fugacity factors to account for the well-known suppression of heavy flavor in elementary collisions, we compute the yields and spectra of D, Ds and Λc hadrons in proton-proton collisions at s=5 TeV. Our main finding is that the enhanced feeddown from excited charm baryons can account for the Λc/D0 ratio measured by ALICE at midrapidity, with some caveat for the forward-rapidity LHCb data. Furthermore, assuming independent fragmentation of charm quarks but with the hadronic ratios fixed by the SHM, the measured transverse-momentum (pT) spectra of D-mesons and Λc can also be described; in particular, the low-pT enhancement in the observed Λc/D0 ratio is attributed to the enhanced feeddown from “missing” charm-baryon states. We comment on the implications of these findings for measurements of Ds and Λc in heavy-ion collisions.

Measurements of charm hadron production and anisotropic flow in Au+Au collisions at 200 GeV with the STAR experiment at RHIC

Heavy flavor quarks, owing to their large masses, are predominantly produced through initial hard parton scatterings in heavy-ion collisions, and thus are excellent probes to study properties of the strongly coupled Quark Gluon Plasma (sQGP) medium produced in these collisions. Measurements of anisotropic flow harmonics of heavy flavor hadrons can provide information on the properties of the medium, including the heavy flavor transport coefficient. Charm quark hadronization mechanism in the sQGP medium can be studied through measurements of yields of different charm hadrons. In these proceedings we report on the measurements of elliptic and triangular flow harmonics of D0 mesons as well as the yield ratios of D±s/D0 and Λ±c/D0 in Au+Au collisions at [see formula in PDF] = 200 GeV at RHIC with the STAR detector. These measurements use the STAR Heavy Flavor Tracker (HFT) to reconstruct charm hadrons via their hadronic decay channels. Results are compared to model calculations and the implications on the understanding of charm quark dynamics in the medium are discussed.

Production of associated Y and open charm hadrons in pp collisions at s = 7 $$ \sqrt{s}=7 $$ and 8 TeV via double parton scattering

Associated production of bottomonia and open charm hadrons in $pp$ collisions at $\sqrt{s}=7$ and $8$TeV is observed using data corresponding to an integrated luminosity of 3$fb^{-1}$ accumulated with the LHCb detector. The observation of five combinations, $\Upsilon(1S)D^0$, $\Upsilon(2S)D^0$, $\Upsilon(1S)D^+$, $\Upsilon(2S)D^+$ and $\Upsilon(1S)D^+_{s}$, is reported. Production cross-sections are measured for $\Upsilon(1S)D^0$ and $\Upsilon(1S)D^+$ pairs in the forward region. The measured cross-sections and the differential distributions indicate the dominance of double parton scattering as the main production mechanism. This allows a precise measurement of the effective cross-section for double parton scattering.