Open Charm Measurements Research Articles

A high-resolution pixel silicon Vertex Detector for open charm measurements with the NA61/SHINE spectrometer at the CERN SPS

The study of open charm meson production provides an efficient tool for the investigation of the properties of hot and dense matter formed in nucleus–nucleus collisions. The interpretation of the existing di-muon data from the CERN SPS suffers from a lack of knowledge on the mechanism and properties of the open charm particle production. Due to this, the heavy-ion programme of the NA61/SHINE experiment at the CERN SPS has been extended by precise measurements of charm hadrons with short lifetimes. A new Vertex Detector for measurements of the rare processes of open charm production in nucleus–nucleus collisions was designed to meet the challenges of track registration and high resolution in primary and secondary vertex reconstruction. A small-acceptance version of the vertex detector was installed in 2016 and tested with Pb + Pb collisions at 150A,text{ GeV }!/!c. It was also operating during the physics data taking on Xe + La and Pb + Pb collisions at 150A,text{ GeV }!/!c conducted in 2017 and 2018. This paper presents the detector design and construction, data calibration, event reconstruction, and analysis procedure.

Feasibility Studies for the Measurement of Open-Charm Mesons at ALICE-3 Using Decay Channels with Neutral Mesons and Photons in the Final State

ALICE-3 is being designed as a next-generation heavy-ion experiment to be operated at the high-luminosity Large Hadron Collider. With luminosities higher by a factor of fifty, ALICE-3 will be able to study5 properties of quark–gluon matter with probes and precision which were previously unavailable due to small cross sections, high background levels, and insufficient detector sensitivity. In particular, the properties of hot and dense QCD matter will be studied by measuring production cross sections, flow coefficients, azimuthal angular correlations and nuclear modification factors for open-charm hadrons. In this contribution, we present the results of feasibility studies for the measurement of ground and excited states of open-charm mesons in decay channels D0 → K− + π+ + π0, D*(2007)0 → D0 + γ and D*(2010)± → D0 + π± in pp, p-Pb and Pb-Pb collisions at LHC energies using the ALICE-3 experimental setup. We formulate the main requirements for the selection of particles and their combinations to ensure reliable signal extraction in a wide transverse momentum range and estimate the minimum size of the required data samples. The results obtained are also compared to previous findings for the open-charm measurements in different decay channels.

Open charm and beauty measurements from small to large systems

Heavy-flavor quarks (i.e. charm and beauty) are essential probes to investigate the properties of the quark-gluon plasma (QGP) created in ultrarelativistic heavy-ion collisions. The measurement of the nuclear modification factor (RAA) gives insight into the in-medium parton energy loss in heavy-ion collisions. Furthermore, the measurements of heavy-flavor elliptic flow (v2) provide crucial information about the degree of thermalization of heavy quarks in the QGP, the path-length dependence of heavy-quark in-medium energy loss, and possible recombination effects. The higher flow harmonics, such as the triangular flow (v3), provide further constraints on the effect of fluctuations in the initial state of the system. The measurements in proton-proton (pp) collisions allow for testing perturbative quantum chromodynamics (pQCD) calculations and are needed as a baseline for investigating the medium effects in heavy-ion collisions. In this contribution, recent results of open charm and beauty production measured with the ALICE detector are discussed.

Constraints of the Low-x Structure of Protons and Nuclei

I review recent developments in the study of the low-x partonic content of pro- tons and nuclei, with a focus on the latter, as one expects possible deviations from linear QCD evolution to be most pronounced in that case. I give examples of recent theoretical descriptions of HERA measurements with a focus on the role of BFKL evolution. I then concentrate on the status and assumptions of nuclear PDFs and the possibility to use for- ward particle production at the LHC as further constraint, in particular measurements of open charm and the potential of electromagnetic probes.

Open-Charm Hadron Measurements in Au+Au Collisions at √sNN = 200 GeV by the STAR Experiment

Study of the open-charm hadron production in heavy-ion collisions is crucial for understanding the properties of the Quark-Gluon Plasma. In these papers, we report on a selection of recent STAR measurements of open-charm hadrons in Au+Au collisions at s NN = 200 GeV , using the Heavy-Flavor Tracker. In particular, the nuclear modification factors of D 0 and D ± mesons, elliptic and directed flow of D 0 mesons, D s /D 0 and Λ c / D 0 yield ratios are discussed. The observed suppression of D 0 and D ± mesons suggests strong interactions of the charm quarks with the QGP. The measured elliptic flow of D 0 mesons is large and follows the NCQ scaling, suggesting that charm quarks may be close to thermal equilibrium with the QGP medium. Both D s /D 0 and Λ c / D 0 yield ratios are found to be enhanced in Au+Au collisions. The enhancement can be explained by models incorporating coalescence hadronization of charm quarks. In addition, the directed flow of the D 0 mesons is measured to be negative and larger than that of light-flavor mesons which is in a qualitative agreement with hydrodynamic model predictions with a tilted QGP bulk.

Open charm measurements in NA61/SHINE at CERN SPS

The measurements of open charm production was proposed as an important tool to investigate the properties of the hot and dense matter formed in nucleus-nucleus collisions as well as to provide the means for model independent interpretation of the existing data on J/ψ suppression. Recently, the experimental setup of the NA61/SHINE experiment was supplemented with a Vertex Detector which was motivated by the importance and the possibility of the first direct measurements of open charm meson production in heavy ion collisions at SPS energies. First test data taken in December 2016 on Pb+Pb collisions at 150A GeV/c allowed to validate the general concept of D0 meson detection via its D0 → π+ + K− decay channel and delivered a first indication of open charm production.The physics motivation of open charm measurements at SPS energies, pilot results on open charm production, and finally, the future plans of open charm measurements in the NA61/SHINE experiment after LS2 are presented.

Open Charm Measurements at CERN SPS Energies with the New Vertex Detector of the NA61/SHINE Experiment: Status and Plans

The study of open charm meson production provides an efficient tool for detailed investigations of the properties of hot and dense matter formed in nucleus-nucleus collisions. The interpretation of the existing data from the CERN Super Proton Synchrotron (SPS) suffers from a lack of knowledge about the total charm production rate. To overcome this limitation, the heavy-ion program of the NA61/SHINE experiment at the CERN SPS has been upgraded to allow for precise measurements of particles with a short lifetime. A new vertex detector (Small Acceptance version of the Vertex Detector (SAVD)) was constructed to meet the challenges of open charm measurements in nucleus-nucleus collisions. The first exploratory data taking of Pb + Pb collisions at 150A GeV/c with the SAVD was performed in 2016, and a D 0 signal was extracted in its D 0 → π + + K − decay channel. This was the first, direct observation of open charm in nucleus-nucleus collisions at the SPS energies. Furthermore, the future plans of open charm measurements in the NA61/SHINE experiment related to the upgraded version of the Vertex Detector are discussed.

Open charm measurements at CERN SPS energies with the new Vertex Detector of the NA61/SHINE experiment

The study of open charm meson production provides an efficient tool for detailed investigations of the properties of hot and dense matter formed in nucleus-nucleus collisions. The interpretation of the existing data from the CERN SPS suffers from a lack of knowledge on the total charm production rate. To overcome this limitation the heavy-ion programme of the NA61/SHINE experiment at CERN SPS has been expanded to allow for precise measurements of particles with a short lifetime. A new Small Acceptance Vertex Detector (SAVD) was designed and constructed to meet the challenges of open charm measurements in nucleus-nucleus collisions. SAVD was installed in December 2016 for data taking with Pb+Pb collisions at 150A GeV/c. An exploratory set of collected data allowed to validate the general concept of the D0 mesons detection via its D0→π++K- decay channel and delivered the first direct observation of open charm at SPS energies. In October and November of 2017 a large statistic data set has been taken for Xe+La at 150A, 75A, and 40A GeV/c, these data are currently under intense analysis. The physics motivation behind the open charm measurements at the SPS energies will be discussed. Moreover, the concept of the SAVD hardware and status of the analysis will be shown. Also, the future plans of open charm measurements in the NA61/SHINE experiment related to the upgraded Vertex Detector will be presented.

Combination and QCD Analysis of Charm and Beauty Production Cross-section Measurements in Deep Inelastic $ep$ Scattering at HERA

Measurements of open charm and beauty production cross sections in ep deep inelastic scattering (DIS) at HERA from the H1 and ZEUS collaborations are combined. Reduced cross sections are obtained in a restricted kinematic range. Perturbative QCD calculations are compared to the combined data. Next-to-leading order QCD analysis is performed using these data together with combined inclusive HERA DIS cross sections.

Open charm measurements with the NA61/SHINE experiment at the CERN SPS

The strong interactions programme of the NA61/SHINE experiment at the CERN SPS has been extended through the use of new silicon Vertex Detector, which allows for reconstructing open charm particles. The detector was designed to identify those particles by means of a precise reconstruction of their primary and secondary vertices.An initial version of the Vertex Detector, called SAVD (Small Acceptance Vertex Detector), was installed end of 2016. It was operated in a Pb+Pb calibration beam time in 2016, and with Xe+La in 2017. A further Pb+Pb beam time is scheduled for late 2018. The first indications of a D0 peak were observed in the data obtained from the 2016 Pb+Pb run.This work introduces the physics motivation behind the open charm measurements, and the status of the analysis of the collected data on open charm production. Moreover, the plans of future open charm measurements in NA61/SHINE experiment and the related to upgrades of the vertex detector will be discussed.

Combination and QCD analysis of charm and beauty production cross-section measurements in deep inelastic ep scattering at HERA

Measurements of open charm and beauty production cross sections in deep inelastic ep scattering at HERA from the H1 and ZEUS Collaborations are combined. Reduced cross sections are obtained in the kinematic range of negative four-momentum transfer squared of the photon 2.5~hbox {GeV}^2le Q^2 le 2000, hbox {GeV}^2 and Bjorken scaling variable 3 cdot 10^{-5} le x_mathrm{Bj} le 5 cdot 10^{-2}. The combination method accounts for the correlations of the statistical and systematic uncertainties among the different datasets. Perturbative QCD calculations are compared to the combined data. A next-to-leading order QCD analysis is performed using these data together with the combined inclusive deep inelastic scattering cross sections from HERA. The running charm- and beauty-quark masses are determined as m_c(m_c) = 1.290^{+0.046}_{-0.041} mathrm{(exp/fit)}{}^{+0.062}_{-0.014} mathrm{(model)}{}^{+0.003}_{-0.031} mathrm{(parameterisation)} GeV and m_b(m_b) = 4.049^{+0.104}_{-0.109} mathrm{(exp/fit)}{}^{+0.090}_{-0.032} mathrm{(model)}{}^{+0.001}_{-0.031} mathrm{(parameterisation)}~mathrm{GeV}.

Open Charm Measurements at CERN SPS Energies with the New Vertex Detector of the NA61/SHINE Experiment

The heavy-ion programme of the NA61/SHINE experiment at the CERN SPS has been expanded to allow precise measurements of exotic particles with short lifetime. The study of open charm meson production is a sensitive tool for new detailed investigations of the properties of hot and dense matter formed in nucleus-nucleus collisions. In particular, it offers new possibilities for studies of such phenomena as in- medium parton energy loss and quarkonium dissociation and possible regeneration, thus providing new information to probe deconfinement. A new high resolution Vertex Detector was designed for the NA61/SHINE experiment for measurements of the very rare processes of open charm production in nucleus- nucleus collisions at the SPS. It will meet the challenges of track registration and of very precise spatial resolution in primary and secondary vertex reconstruction required for the identification of

Open Charm measurements at the NA61 experiment at CERN SPS

The strong interactions programme of the NA61/SHINE experiment at CERN SPS has been extended through the use of new silicon Vertex Detector which provides precise measurements of exotic particles with short lifetime. The detector was designed to meet the challenges of primary and secondary vertexes reconstruction at high spatial resolution. An initial version of the Vertex Detector called SAVD (Small Acceptance Vertex Detector) was installed last end of 2016, and data was from Pb+Pb collisions was collected in 2016, for Xe+La in 2017, as well as further Pb+Pb collisions this year. First indication of a D0 peak at SPS energies has been observed. The physics motivation behind the open charm measurements will be discussed, as well as the analysis of collected data on open charm production and the future plans of open charm measurements in NA61/SHINE experiment related to the upgraded version of the vertex detector.

D meson nuclear modification factor and vn harmonics in PbPb collisions at 5.02 TeV with CMS

The measurement of heavy flavor production is a powerful tool to study the properties of the high-density QCD medium created in heavy-ion collisions as heavy quarks are sensitive to the transport properties of the medium and may interact with the QCD matter differently from light quarks. In particular, the comparison between the nuclear modification factors (RAA) of light- and heavy-flavor particles provides insights into the expected flavor dependence of in-medium parton energy loss. Furthermore, azimuthal anisotropy coefficients (vn) of heavy-flavor particles provide insights into the degree of the thermalization of the bulk medium at low pT, and unique information about the path length dependence of heavy quark energy loss at high pT. Using the large pp and PbPb samples collected at 5.02 TeV during the 2015 LHC run, high precision open charm measurements are performed with the CMS detector in a wide transverse momentum range. This allows us to set an important milestone in our understanding of the interactions between charm quarks and the medium. In this talk, the most recent results of the RAA, v2 and v3 of prompt D0 mesons in PbPb collisions at 5.02 TeV are presented and compared to the same results for charged particles (dominated by light flavor hadrons) at the same energy.

D meson nuclear modification factor in PbPb at 5.02 TeV with CMS

The measurement of heavy flavour production is a powerful tool to study the properties of the high-density QCD medium created in heavy-ion collisions as heavy quarks are sensitive to the transport properties of the medium and may interact with the QCD matter differently from light quarks. In particular, the comparison between the nuclear modification factors of light- and heavy-flavour particles provides insights into the expected flavour dependence of in-medium parton energy loss. Using the large statistics proton-proton and PbPb samples collected at 5.02 TeV during the 2015 LHC run, high precision open charm measurements are performed with the CMS detector in a wide transverse momentum range, from few GeV up to approximately 100 GeV. This allows us to set an important milestone in our understanding of energy loss phenomena. In this talk, the most recent results of nuclear modification factor of D0 mesons in PbPb collisions at 5.02 TeV are presented and compared to the charged hadron nuclear modification factor at the same energy.

Open-charm measurements in pp and Pb–Pb collisions at central rapidity with ALICE

An overview of recent D+, D0, D*+ and measurements performed by ALICE at central rapidity in proton-proton collisions at and 8 TeV, as well as lead-lead collisions at , is presented. An emphasis is put on the discussion of theoretical predictions with respect to the LHC Run I data.

Open-charm production measurements in pp, 1 p-Pb and Pb-Pb collisions with ALICE at the LHC

ALICE (A Large Ion Collider Experiment) is designed to study the strongly in teracting matter, the Quark-Gluon Plasma (QGP), created in heavy-ion collisions at LHC energies. Charm and beauty quarks are powerful probes to study the QGP. Produced in hard partonic scattering processes on a short time scale, they are expected to traverse the QCD medium, interacting with its constituents and losing energy through radiative and collisional processes. In ALICE, open-charm production is studied through the reconstruction of the hadronic decays of D 0 , D + , D *+ and D s + mesons at mid-rapidity. High precision tracking, good vertexing capabilities and excellent particle identification offered by ALICE allow for the measurement of particles containing heavy quarks (particularly D mesons) in a wide transverse momentum range in pp, p-Pb and Pb-Pb collisions. A review of the main results on D-meson production in pp collisions at √s = 7 TeV, p-Pb collisions at √s NN = 5.02 TeV and Pb-Pb collisions at √s NN = 2.76 TeV will be presented.

Track reconstruction in the inhomogeneous magnetic field for Vertex Detector of NA61/SHINE experiment at CERN SPS

The heavy-ion programme of the NA61/SHINE experiment at CERN SPS is expanding to allow precise measurements of exotic particles with lifetime few hundred microns. A Vertex Detector for open charm measurements at the SPS is being constructed by the NA61/SHINE Collaboration to meet the challenges of high spatial resolution of secondary vertices and efficiency of track registration. This task is solved by the application of the coordinate sensitive CMOS Monolithic Active Pixel Sensors with extremely low material budget in the new Vertex Detector.A small-acceptance version of the Vertex Detector is being tested this year, later it will be expanded to a large-acceptance version. Simulation studies will be presented. A method of track reconstruction in the inhomogeneous magnetic field for the Vertex Detector was developed and implemented. Numerical calculations show the possibility of high precision measurements in heavy ion collisions of strange and multi strange particles, as well as heavy flavours, like charmed particles.

Open-charm production measurements with ALICE at the LHC

The LHC heavy-ion physics program aims at investigating the properties of strongly-interacting matter under extreme conditions of temperature and energy den- sity where the formation of the Quark-Gluon Plasma (QGP) is expected. Heavy-flavour hadrons, containing charm and beauty quarks, are considered efficient probes to investi- gate the properties of the QGP produced in heavy-ion collisions. Heavy quarks are pro- duced in hard partonic scattering processes in the initial stage of hadronic collisions and propagate through the hot and dense medium created in the collision losing energy inter- acting with the medium via radiative and collisional processes. The high precision track- ing, good vertexing capabilities and excellent particle identification offered by the ALICE experiment allow us to measure particles containing heavy quarks in a wide transverse- momentum range in pp, p-Pb and Pb-Pb collisions. A review of the main results on prompt D-mesons production, reconstructed via their hadronic decays at mid-rapidity, in pp collisions at √ s = 7 TeV, p-Pb collisions at √ sNN = 5.02 TeV and Pb-Pb collisions at √ sNN = 2.76 TeV will be shown.

Heavy Flavour Production at HERA

Measurements of open charm and beauty production at HERA provide important input for stringent tests of quantum chromodynamics and are used to constrain the parton distribution functions of the proton. The recent results on the heavy flavour production obtained by the H1 and ZEUS experiments at HERA are reviewed in this contribution.