Measurement Of D-meson Production Research Articles

Measurement of D-meson production and flow in Pb–Pb collisions with ALICE at the LHC

Open-charmed mesons are unique tools to study the properties of the Quark–Gluon Plasma (QGP) formed in ultra-relativistic nucleus–nucleus collisions. The nuclear modification factor ([Formula: see text]) and elliptic flow ([Formula: see text]) of [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text] mesons were measured by the ALICE Collaboration in Pb–Pb collisions at [Formula: see text][Formula: see text]TeV. The D-meson [Formula: see text] provides information on the charm-quark interactions with the medium and the charm-quark energy loss. The D-meson elliptic flow at low transverse momentum ([Formula: see text]) gives insight into the participation of charm quarks in the collective expansion of the system and their possible in-medium thermalization. At high [Formula: see text], the [Formula: see text] is sensitive to the path-length dependence of parton energy loss. The role of the recombination mechanism is investigated measuring the [Formula: see text]-differential yield ratios between D-meson species with and without strange-quark content. Finally, the coupling of charm quarks to light quarks of the underlying medium is examined applying the Event-Shape Engineering (ESE) technique to the nonstrange D-meson elliptic flow.

Measurement of D-meson production at mid-rapidity in pp collisions at {sqrt{s}=7}\xa0TeV

The production cross sections for prompt charmed mesons mathrm{D^0}, mathrm{D^+}, mathrm{D^{*+}} and mathrm{D_s^+} were measured at mid-rapidity in proton–proton collisions at a centre-of-mass energy sqrt{s}=7~{mathrm {TeV}} with the ALICE detector at the Large Hadron Collider (LHC). D mesons were reconstructed from their decays mathrm{D}^0 rightarrow mathrm{K}^-pi ^+, mathrm{D}^+rightarrow mathrm{K}^-pi ^+pi ^+, mathrm{D}^{*+} rightarrow mathrm{D}^0 pi ^+, mathrm{D_s^{+}rightarrow phi pi ^+rightarrow K^-K^+pi ^+}, and their charge conjugates.With respect to previous measurements in the same rapidity region, the coverage in transverse momentum (p_mathrm{T}) is extended and the uncertainties are reduced by a factor of about two. The accuracy on the estimated total mathrm{c}{overline{mathrm{c}}} production cross section is likewise improved. The measured p_mathrm{T}-differential cross sections are compared with the results of three perturbative QCD calculations.

Measurement of D-meson production in Pb—Pb collisions at the LHC with ALICE

The measurement of D-meson production in heavy-ion collisions at LHC energy provides insights into the mechanisms of interaction of charm quarks in the hot and dense medium formed in these collisions. ALICE results on the D-meson nuclear modification factor and azimuthal anisotropy in Pb-Pb collisions at √sNN = 2.76 TeV are presented.

Measurement of D-meson production in pp, p–Pb and Pb–Pb collisions with ALICE at the LHC

Heavy quarks, i.e. charm and beauty, are considered calibrated probes for the strongly interacting deconfined medium (Quark Gluon Plasma, QGP) formed in heavy-ion collisions. Produced in hard scattering processes in the initial stages of the collision, they interact with the medium, lose energy and, depending on the coupling strength to the medium, take part in the collective motion of the QCD matter. ALICE measured the production of ${\rm D^{0}}$, ${\rm D^{*+}}$, ${\rm D^{+}}$ and ${\rm D_{s}}$ mesons at central rapidity in pp, p-Pb and Pb-Pb collisions at the LHC. The study of the modification of the transverse momentum differential yields of charm particles in Pb-Pb collisions with respect to pp collisions, quantified by the nuclear modification factor ($R_{\rm AA}$), can unravel details of the energy loss mechanism, such as its dependence on the quark mass and on the path length the parton travels through the medium. A similar comparison between pp and p-Pb collision data ($R_{\rm pPb}$) is fundamental to disentangle effects related to the presence of the hot medium from cold nuclear matter effects. The degree of thermalization and coupling to the medium is investigated in semi-peripheral Pb-Pb collisions by measuring the elliptic flow coefficient ($v_{2}$) at low pt. At high pt, $v_{2}$ is sensitive to the path-length dependence of the energy loss. Results on the transverse momentum and centrality dependence of the D-meson elliptic flow and $R_{AA}$ will be presented. The comparison with the $R_{\rm AA}$ of non-prompt ${\rm J/}\psi$ from B-meson decays measured with CMS will be discussed. The preliminary results on D-meson $R_{\rm pPb}$ and the dependence of D-meson yields on rapidity in p-Pb collisions will be shown. As an outlook, the analysis and the preliminary results on the azimuthal correlations of D mesons and charged hadrons in pp collisions will be described.

Measurement of D-meson production in pp, p-Pb, and Pb-Pb collisions at the LHC with the ALICE detector

Heavy quarks are a powerful probe for investigating the properties of the Quark- Gluon Plasma created in heavy-ion collisions, since they are produced in initial hard scattering processes and experience all the stages of the medium evolution. ALICE has measured the production of D0 D+, D*+ and D+s mesons at central rapidity in their hadronic decay channels in various collision systems and energies. We present recent results for D-meson production measured by the ALICE Collaboration in pp collisions at = 7 and 2.76 TeV, Pb-Pb collisions at = 2.76 TeV and p-Pb collisions at = 5.02 TeV.

Measurement of D-meson production in p-Pb collisions with the ALICE detector

The ALICE Collaboration has measured the production of prompt D mesons in p-Pb collisions at = 5.02 TeV in the rapidity range −0.04 < ycms < 0.96 via the exclusive reconstruction of their hadronic decays: D0 → K−π+, D+ → K−π+π+, D*+ → D0π+ and D+s → ϕπ+. The pT-differential production cross sections and the pT-dependent nuclear modification factors with respect to a proton-proton reference, RpPb, are presented.

A measurement ofD meson production inZ 0 hadronic decays

A study of the fragmentation properties of charm and bottom quarks intoD mesons is presented. From 263 700Z0 hadronic decays collected in 1991 with the DELPHI detector at the LEP collider,D0,D+ andD*+ are reconstructed in the modesK−π+,K−π+K+ andD0π+ followed byD0→K−π+, respectively. The fractional decay widths\(\Gamma {{(Z^0 \to {D \mathord{\left/ {\vphantom {D {\bar D}}} \right. \kern-\nulldelimiterspace} {\bar D}}X)} \mathord{\left/ {\vphantom {{(Z^0 \to {D \mathord{\left/ {\vphantom {D {\bar D}}} \right. \kern-\nulldelimiterspace} {\bar D}}X)} {\Gamma _h }}} \right. \kern-\nulldelimiterspace} {\Gamma _h }}\) are determined, and first results are presented for the production ofD mesons from\(c\bar c\) and\(b\bar b\) events separately. The average energy fraction ofD*± in charm quark fragmentation is found to be 〈XE(D*)〉c=0.487±0.015 (stat)±0.005 (sys.). Assuming that the fraction ofDs and charm-baryons produced at LEP is similar to that around 10 GeV, theZ0 partial width into charm quark pairs is determined to beΓc/Γh=0.187±0.031 (stat)±0.023 (sys). The probability for ab quark to fragment into\(\bar B_s \) orb-baryons is inferred to be 0.268±0.094 (stat)±0.100 (sys) from the measured probability that it fragments into a\(\bar B^0 \) orB−.

A measurement ofD meson production inZ 0 hadronic decays

A study of the fragmentation properties of charm and bottom quarks intoD mesons is presented. From 263 700Z 0 hadronic decays collected in 1991 with the DELPHI detector at the LEP collider,D 0,D + andD *+ are reconstructed in the modesK − π +,K − π + K + andD 0 π + followed byD 0→K − π +, respectively. The fractional decay widths\(\Gamma {{(Z^0 \to {D \mathord{\left/ {\vphantom {D {\bar D}}} \right. \kern-\nulldelimiterspace} {\bar D}}X)} \mathord{\left/ {\vphantom {{(Z^0 \to {D \mathord{\left/ {\vphantom {D {\bar D}}} \right. \kern-\nulldelimiterspace} {\bar D}}X)} {\Gamma _h }}} \right. \kern-\nulldelimiterspace} {\Gamma _h }}\) are determined, and first results are presented for the production ofD mesons from\(c\bar c\) and\(b\bar b\) events separately. The average energy fraction ofD *± in charm quark fragmentation is found to be 〈X E (D *)〉 c =0.487±0.015 (stat)±0.005 (sys.). Assuming that the fraction ofD s and charm-baryons produced at LEP is similar to that around 10 GeV, theZ 0 partial width into charm quark pairs is determined to beΓ c /Γ h =0.187±0.031 (stat)±0.023 (sys). The probability for ab quark to fragment into\(\bar B_s \) orb-baryons is inferred to be 0.268±0.094 (stat)±0.100 (sys) from the measured probability that it fragments into a\(\bar B^0 \) orB −.

Measurement ofD meson production in 200 GeV π−-Be interactions

We have measured the differential and total cross sections ofD meson production in 200 GeV π−-beryllium interactions, using a sample of 48 fully reconstructed and nearly background-freeD mesons in the decay channelsK∓π±,K∓π±π± andK∓π∓π±π±. A single electron trigger has been used to select events containing a pair of charmed particles. A vertex telescope of 6 silison microstrip detectors allowed the reconstruction of tracks of charged secondaries and the reconstruction of primary and decay vertices with high precision. The ratio of branching fractions for\(\mathop {D^0 }\limits^{( - )} \to K^ \mp \pi ^ \pm \) to\(\mathop {D^0 }\limits^{( - )} \to K^ \mp \pi ^ \mp \pi ^ \pm \pi ^ \pm \), and an upper limit for\(D^0 - \bar D^0 \) mixing are presented.