Measurement of azimuthal correlations between D mesons and charged hadrons with ALICE at the LHC

The comparison of angular correlations between charmed mesons and charged hadrons produced in pp, p-Pb and Pb-Pb collisions can give insight into the mechanisms through which charm quarks lose energy in a QGP medium, produced in ultra-relativistic heavy-ion collisions, and can help to recognize possible modifications of their hadronization induced by the presence of the QGP. The analysis of pp and p-Pb data and the comparison with predictions from pQCD calculations, besides constituting the necessary reference for interpreting Pb-Pb data, can provide relevant information on charm production and fragmentation processes. In addition, possible differences between the results from pp and p-Pb collisions can give information on the presence of cold nuclear matter effects, affecting the charm production and hadronization in the latter collision system. A study of azimuthal correlations between D$^0$, D$^+$, and D$^{*+}$ mesons and charged hadrons in pp collisions at $\sqrt{s}$ = 7 TeV and p-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV are presented. D mesons were reconstructed from their hadronic decays at central rapidity in the transverse-momentum range $3 \leq p_{\rm T}^{\rm D} \leq 16$ GeV/$c$ and were correlated to charged particles reconstructed in the pseudorapidity range $|\eta| < 0.8$. Perspectives for the measurement in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV will also be presented.Comment: 5 pages, 4 figures, Proceedings of the QCD@Work 2014 conference, 16-19 June 2014, Giovinazzo (Italy

Heavy-flavour production in pp collisions and correlations in pp and p-Pb collisions measured with ALICE at the LHC

Thanks to its excellent tracking and particle identification performance, the ALICE detector is capable of measuring D mesons at central rapidity via their hadronic decay channels down to very low transverse momentum. We show an extension of the prompt ${\rm D}^0$ $p_{\rm T}$-differential cross section measurement down to zero transverse momentum, which allows us to determine the $p_{\rm T}$-integrated charm production cross section at central rapidity in pp collisions at $\sqrt{s}$ = 7 TeV. We also present measurements of azimuthal correlations of prompt ${\rm D}^0$, ${\rm D}^+$ and ${\rm D}^{*+}$ mesons with charged hadrons in pp collisions at $\sqrt{s}$ = 7 TeV and p-Pb collisions at $\sqrt{s_{\scriptscriptstyle \rm NN}}$ = 5.02 TeV and compare the results with expectations from models.Comment: Proceedings for Strangeness in Quark Matter 2016 conference - 4 pages, 3 figure

Open heavy-flavour measurements with ALICE at the LHC

Heavy quarks are produced in the early stages of ultra-relativistic heavy-ion collisions, and their number is preserved throughout the subsequent evolution of the system. Therefore, they constitute ideal probes for characterising the Quark--Gluon Plasma (QGP) medium and for the study of its transport properties. In particular, heavy quarks interact with the partonic constituents of the plasma, losing energy, and are expected to be sensitive to the medium collective motion induced by its hydrodynamical evolution. In pp collisions, the measurement of heavy-flavour hadron production provides a reference for heavy-ion studies, and allows also testing perturbative QCD calculations in a wide range of collision energies. Similar studies in p--Pb collisions help in disentangling cold nuclear matter effects from modifications induced by the presence of a QGP medium, and are also useful to investigate the possible existence of collective phenomena also in this system. The ALICE detector provides excellent performances in terms of particle identification and vertexing capabilities. Hence, it is fully suited for the reconstruction of charmed mesons and baryons and of electrons from heavy-flavour hadron decays at central rapidity. Furthermore, the ALICE muon spectrometer allows reconstructing heavy-flavour decay muons at forward rapidity. A review of the main ALICE results on open heavy flavour production in pp, p--Pb and Pb--Pb collisions is presented. Recent, more differential measurements are also shown, including azimuthal correlations of heavy-flavour particles with charged hadrons in p--Pb collisions, and D-meson tagged-jet production in p--Pb and Pb--Pb collisions.Comment: 7 pages, 5 figures; QCD@work 2018 conference proceeding

D meson-hadron angular correlations in pp and p-Pb collisions with ALICE at the LHC

The comparison of angular correlations between charmed mesons and charged hadrons produced in pp, p-Pb and Pb-Pb collisions can give insight into charm quark energy loss mechanisms in hot nuclear medium formed in heavy-ion collisions and can help to spot possible modifications of charm quark hadronization induced by the presence of the medium. The analysis of pp and p-Pb data and the comparison with predictions from pQCD calculations, besides constituting the necessary baseline for the interpretation of Pb-Pb results, can provide relevant information on charm production and fragmentation processes. We present a study of azimuthal correlations between D$^0$ and D$^{\ast +}$ mesons and charged hadrons measured by the ALICE experiment in pp collisions at $\sqrt{s} = 7$ TeV and p-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV. D mesons were reconstructed from their hadronic decays at central rapidity and in the transverse momentum range $2 < p_{_{\rm T}} < 16$ GeV/$c$, and they were correlated to charged hadrons reconstructed in the pseudorapidity range $|\eta| < 0.8$.Comment: 4 pages, 4 figures. Proceedings of the Strangeness in Quark Matter Conference (SQM 2013), 22nd - 27th July 2013, published by the Open Access Journal of Physics: Conference Series (JPCS), in the IOP conference serie

Heavy-flavor correlations and multiplicity dependence in pp and p--Pb collisions with ALICE

The production of heavy quarks in pp collisions at the LHC energies provides a reliable test of perturbative QCD calculations. Comparisons of pp and \pPb measurements of their hadronization products allow us to investigate how cold nuclear matter effects affect the heavy-quark production. We present ALICE measurements of azimuthal correlations of prompt D mesons with charged hadrons in pp collisions at \s = 7 TeV and \pPb collisions at \sNN = 5.02 TeV. We also show the per-event D-meson yields as a function of the charged-particle multiplicity in pp collisions at \s = 7 TeV.Comment: Proceedings of Quark Matter 2015 conferenc

Measurement of cross section for D0 direct production from the Kπππ decay channel in p-p collisions at √s = 7TeV with ALICE

The production of the D0 meson in pp collisions at √s = 7TeV through its hadronic decay in Kπππ, using the ALICE detector, is measured. By applying a series of topological cuts and PID selections, signal peaks in the invariant mass distribution M(Kπππ) have been found in different pT bins, ranging from 4.5 to 25 GeV/c. After performing corrections for efficiency, acceptance and feed-down from beauty contribution, differential direct production yield and cross section can be computed and compared to pQCD theoretical predictions which show a good agreement for the shape of the pT-differential cross section

Study of azimuthal correlations between D mesons and charged particles with the ALICE experiment

A study of azimuthal correlations between D$^0$, D$^+$, and D$^{*+}$ and charged particles in pp collisions at $\sqrt{s}$ = 7 TeV and p-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV is presented. D mesons were reconstructed from their hadronic decays at central rapidity ($|y| < 0.5$) in the transverse momentum range $3 \leq p_{\rm T}^{\rm D} \leq 16$ GeV/$c$ and they were correlated with charged particles reconstructed in the pseudorapidity range $|\eta| < 0.8$. Perspectives for the measurement in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.5 TeV after the ALICE upgrade are presented as well.Comment: 4 pages, 3 figures (5 panels), Proceedings for the Hot Quarks 2014 Workshop (Las Negras, Spain, 21-28/09/2014

Reduction of multiple pregnancies in the advanced maternal age population after implementation of an elective single embryo transfer policy coupled with enhanced embryo selection: Pre- and post-intervention study

STUDY QUESTION Is an elective single-embryo transfer (eSET) policy an efficient approach for women aged &gt;35 years when embryo selection is enhanced via blastocyst culture and preimplantation genetic screening (PGS)? SUMMARY ANSWER Elective SET coupled with enhanced embryo selection using PGS in women older than 35 years reduced the multiple pregnancy rates while maintaining the cumulative success rate of the IVF programme. WHAT IS KNOWN ALREADY Multiple pregnancies mean an increased risk of premature birth and perinatal death and occur mainly in older patients when multiple embryos are transferred to increase the chance of pregnancy. A SET policy is usually recommended in cases of good prognosis patients, but no general consensus has been reached for SET application in the advanced maternal age (AMA) population, defined as women older than 35 years. Our objective was to evaluate the results in terms of efficacy, efficiency and safety of an eSET policy coupled with increased application of blastocyst culture and PGS for this population of patients in our IVF programme. STUDY DESIGN, SIZE, DURATION In January 2013, a multidisciplinary intervention involving optimization of embryo selection procedure and introduction of an eSET policy in an AMA population of women was implemented. This is a retrospective 4-year (January 2010-December 2013) pre- and post-intervention analysis, including 1161 and 499 patients in the pre- and post-intervention period, respectively. The primary outcome measures were the cumulative delivery rate (DR) per oocyte retrieval cycle and multiple DR. PARTICIPANTS/MATERIALS, SETTING, METHODS Surplus oocytes and/or embryos were vitrified during the entire study period. In the post-intervention period, all couples with good quality embryos and less than two previous implantation failures were offered eSET. Embryo selection was enhanced by blastocyst culture and PGS (blastocyst stage biopsy and 24-chromosomal screening). Elective SET was also applied in cryopreservation cycles. MAIN RESULTS AND THE ROLE OF CHANCE Patient and cycle characteristics were similar in the pre- and post-intervention groups [mean (SD) female age: 39.6 ± 2.1 and 39.4 ± 2.2 years; range 36-44] as assessed by logistic regression. A total of 1609 versus 574 oocyte retrievals, 937 versus 350 embryo warming and 138 versus 27 oocyte warming cycles were performed in the pre- and post-intervention periods, respectively, resulting in 1854 and 508 embryo transfers, respectively. In the post-intervention period, 289 cycles were blastocyst stage with (n = 182) or without PGS (n = 107). A mean (SD) number of 2.9 ± 1.1 (range 1-4) and 1.4 ± 0.8 (range 1-3) embryos were transferred pre- and post-intervention, respectively (P &lt; 0.01) and similar cumulative clinical pregnancy rates per transfer and per cycle were obtained: 26.8, 30.9% and 29.7, 26.3%, respectively. The total DR per oocyte retrieval cycle (21.0 and 20.4% pre- and post-intervention, respectively) defined as efficacy was not affected by the intervention [odds ratio (OR) = 0.8, 95% confidence interval (CI) = 0.7-1.1; P = 0.23]. However, a significantly increased live birth rate per transferred embryo (defined as efficiency) was observed in the post-intervention group 17.0 versus 10.6% (P &lt; 0.01). Multiple DRs decreased from 21.0 in the preintervention to 6.8% in the post-intervention group (OR = 0.3. 95% CI = 0.1-0.7; P &lt; 0.01). LIMITATIONS, REASONS FOR CAUTION In this study, the suitability of SET was assessed in individual women on the basis of both clinical and embryological prognostic factors and was not standardized. For the described eSET strategy coupled with an enhanced embryo selection policy, an optimized culture system, cryopreservation and aneuploidy screening programme is necessary. WIDER IMPLICATIONS OF THE FINDINGS Owing to the increased maternal morbidity and perinatal complications related to multiple pregnancies, it is recommended to extend the eSET policy to the AMA population. As shown in this study, enhanced embryo selection procedures might allow a reduction in the number of embryos transferred and the number of transfers to be performed without affecting the total efficacy of the treatment but increasing efficiency and safety. © The Author 2015. Published by Oxford University Press on behalf of the European Society of Human Reproduction and Embryology

Azimuthal anisotropy of charged jet production in root s(NN)=2.76 TeV Pb-Pb collisions

We present measurements of the azimuthal dependence of charged jet production in central and semi-central root s(NN) = 2.76 TeV Pb-Pb collisions with respect to the second harmonic event plane, quantified as nu(ch)(2) (jet). Jet finding is performed employing the anti-k(T) algorithm with a resolution parameter R = 0.2 using charged tracks from the ALICE tracking system. The contribution of the azimuthal anisotropy of the underlying event is taken into account event-by-event. The remaining (statistical) region-to-region fluctuations are removed on an ensemble basis by unfolding the jet spectra for different event plane orientations independently. Significant non-zero nu(ch)(2) (jet) is observed in semi-central collisions (30-50% centrality) for 20 <p(T)(ch) (jet) <90 GeV/c. The azimuthal dependence of the charged jet production is similar to the dependence observed for jets comprising both charged and neutral fragments, and compatible with measurements of the nu(2) of single charged particles at high p(T). Good agreement between the data and predictions from JEWEL, an event generator simulating parton shower evolution in the presence of a dense QCD medium, is found in semi-central collisions. (C) 2015 CERN for the benefit of the ALICE Collaboration. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).Peer reviewe