Measurements Of Open Charm Production Research Articles

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.

Measurements of open charm production in Au+Au collisions at [formula omitted] with the STAR experiment at RHIC

We report in these proceedings on the measurements of collision centrality and transverse momentum (pT) dependences of the Λc± production in Au+Au collisions at sNN=200GeV, using the STAR Heavy Flavor Tracker (HFT). The Λc± signal significance is greatly improved with the addition of the high-statistics data set collected in 2016 and the use of a supervised machine learning method for topological reconstruction of the decay vertices. The measured Λc±/D0 ratio shows a significant enhancement compared to the PYTHIA prediction for p+p collisions, across the measured pT range. We also report on the updated measurements of D0 nuclear modification factors RAA and RCP using the 2014 data with the HFT. The measured D0RAA in central collisions is lower than unity across the pT interval of the measurement. The D0 yields show strong suppression at high pT (> 6 GeV/c) in central collisions, consistent with that of light flavor hadrons. The cc‾ production cross section per binary nucleon collision at midrapidity in Au+Au collisions at 200 GeV is extracted based on the various charm hadron measurements by STAR. It is observed that while the charm hadrochemistry is significantly modified in Au+Au collisions compared to p+p collisions, the cc‾ production cross section at midrapidity remains consistent between Au+Au and p+p collisions.

Latest results on diffraction at HERA

Recent results on diffraction from the H1 and ZEUS experiments at HERA are presented. Measurement of open charm production in diffractive DIS has been performed by the H1 experiment using the event topology, given by ep → eXY, where the system X, containing at least one D*(2010) meson, is separated from a leading low-mass proton dissociative system Y by a large rapidity gap. The photoproduction of isolated photons is measured using diffractive events recorded by the ZEUS experiment. Cross sections are evaluated in the photon transverse-energy and pseudorapidity ranges 5 < EγT < 15 GeV and -0:7 < ηγ < 0:9, inclusively and with a jet with transverse-energy and pseudorapidity in the ranges 4 < EjetT < 35 GeV and -1:5 < ηjet < 1:8. The exclusive deep inelastic electroproduction and photoproduction of Ψ(2S ) and J=Ψ(1S) mesons has been also studied by ZEUS. The cross-section ratio σ(Ψ(2S))=σ(J=Ψ(1S)) has been measured as a function of Q2, W and t. The results are compared to several predictions of QCD-inspired models, providing tests of the models in a region of soft to hard diffraction.

Measurements of open charm production and flow in √sNN = 200GeV Au+Au collisions with the STAR experiment at RHIC

We present an improved, higher statistics, measurement with respect to the previously published results of the D0 meson elliptic flow (v2) as a function of transverse momentum (pT) in Au+Au collisions at √sNN = 200 GeV with the STAR Heavy Flavor Tracker (HFT). The D0 v2 results are compared to those of light-flavor hadrons to test the number-of-constituent-quark (NCQ) scaling. They are also compared to recent hydrodynamic and transport model calculations. We also report on the updated measurements of D0 nuclear modification factors RAA and RCP using the 2014 data. The measured D0 RAAin central collisions is less than 1 across the entire pT region. The D0 yields show strong suppression at high pT (> 6 GeV/c) in central collisions, consistent with those of light flavor hadrons. We also report the measurements of collision centrality and pT dependences of the Λ±c production in Au+Au collisions at √sNN = 200 GeV, using the HFT. The Λ±c signal significance is greatly improved with the addition of the highstatistics data set collected in 2016 and the use of a supervised machine learning method for a more effcient topological reconstruction of the decay vertices. The measured Λ±c/D0 ratio in 10-80% Au+Au collisions shows a significant enhancement compared to the PYTHIA prediction for p + p collisions, across the measured pT range.

Charm physics

Charm physics is an active and productive field at hadron colliders. In these proceedings an overview of recent results in charm physics from the Tevatron and LHC experiments is given. Highlighted are the measurements of open charm production and production asymmetries, the recent precision measurements of the D masses, the confirmation of mixing in the D0 system, the searches for CP violation in the charm system and the searches for rare charm decays.

Measurement of open charm production in d+Au collisions at

We present the first comprehensive measurement of D0, D+, D*+ and their charge conjugate states at mid-rapidity in d+Au collisions at using the STAR TPC. The directly measured open charm multiplicity distribution covers a broad transverse momentum region of 0 < pT < 11 GeV/c. The measured dN/dy at mid-rapidity for D0 is 0.0265 ± 0.0036 (stat.), ± 0.0071 (syst.), and the measured D*+/D0 and D+/D0 ratios are approximately equal with a magnitude of 0.40 ± 0.09 (stat.) ± 0.13 (syst.). The total cross section per nucleon–nucleon collision extracted from this study is 1.18 ± 0.21 (stat.) ± 0.39 (syst.) mb. The direct measurement of open charm production is consistent with STAR single electron data. This cross section is higher than expectations from PYTHIA and other pQCD calculations. The measured pT distribution is harder than the pQCD prediction using the Peterson fragmentation function.

Highlights from STAR

Selected results from the STAR collaboration are presented. We focus on recent results on jet-like correlations, nuclear modification factors of identified hadrons, elliptic flow of multi-strange baryons Ξ and Ω, and resonance yields. First measurements of open charm production at RHIC are presented.

Charm production at HERA

Measurements of open charm production at HERA are reviewed. The paper covers both photoproduction and Deep Inelastic Scattering measurements from the ZEUS and H1 collaborations.

Measurement of charm production in two-photon processes using inclusive lepton events at TRISTAN

Measurements of open charm production in photon-photon collisions made with the AMY detector at TRISTAN are reported. Charmed hadrons were identified by detecting the high momentum muons or electrons from their semileptonic decays. The data sample corresponds to an integrated luminosity of 275 pb −1 at an average center of mass energy of 58 GeV. Results are presented in the form of cross sections of inclusive leptons from charm for both muons and electrons. The measured cross section is 1.8 standard deviations higher than theoretical predictions based on the direct and photon-gluon fusion process, where the mass of charm quark is assumed to be 1.6 GeV.

Measurement of open charm production in two-photon processes with detection of electron-inclusive events

Experimental studies of open charm production in two-photon processes have been performed. In the measurement, charmed hadrons were identified by electrons from their semi-leptonic decays. The result was compared with calculations based on the direct process and photon-gluon fusion process by resolved photons. We found that the effect of the gluon component in a photon is substantial in the observed events.