Abstract: The recent observation of stationary zonal-flow-like structures on JET with Doppler back-scattering [1] has motivated the search for similar structures in the radial electric field Er well on COMPASS [5]. The diagnostic used on COMPASS is a complex probe head mounted on a horizontal reciprocating manipulator on the outer midplane which enables a direct measurement of Er as well as the perpendicular component of the Reynolds stress tensor <vrvp>. The Reynolds stress has been identified in ... [full abstract]
Posters
Posters presented by our students and researchers at conferences.
Search for zonal structures on the radial electric field and Reynolds stress profile on COMPASS
Authors: Ondřej Grover (student - FTTF)
Date and location: 2. 7. - 6. 7. 2018, Prague, Czech Republic
18. 6. - 21. 6. 2018, Prague, Czech Republic
Award: Highly commended, Itoh Project Prize 2018
Best poster at SPPT 2018 award
The recent observation of stationary zonal-flow-like structures on JET with Doppler back-
scattering [1] has motivated the search for similar structures in the radial electric field Er well
on COMPASS [5]. The diagnostic used on COMPASS is a complex probe head mounted on a
horizontal reciprocating manipulator on the outer midplane which enables a direct measurement
of Er as well as the perpendicular component of the Reynolds stress tensor hv ̃rv ̃pi. The Reynolds
stress has been identified in recent models and experiments [2] as a likely driver of poloidal
zonal flows which are expected to play a key role in the L-H transition and the associated limit
cycle oscillations (LCO) [3]. The probe head features both Langmuir and ball-pen probes [4]
which enables a correction for the effect of the electron temperature on measurements of Er
.
It was demonstrated that the probe diagnostic can measure radial profiles of Er which cover
the full extent of the Er well and remain stationary during both the inward and outward recip-
rocations. The search for stationary structures on the Er profile was complicated by saw-teeth
crashes which modulate Er
. For this reason, dedicated scenarios were developed. A statistical
method based on the bootstrapped Kernel regression was used to asses the statistical signifi-
cance of any spatial features on the profiles.
While no statistically significant, stationary zonal-flow-like structures have been observed on
the Er profile inside the Er well, near-stationary zonal-like structures were observed on the pro-
file of the Reynolds stress. The structures do not appear to be correlated with saw-teeth crashes.
The structures show a strong correlation between the local poloidal shear ∂rvp ≈ ∂rEr/Bφ and
the Reynolds stress force −∂rhv ̃rv ̃pi.
D meson production in Au+Au collisions at 200 GeV measured by the STAR experiment
Author: Jakub Kvapil (student - EJČF)
Conference: Quark Matter 2017
53rd Karpacz Winter School of Theoretical Physics
Date and location: 5. 2. - 11. 2. 2017, Chicago, USA
26. 2. - 4. 3. 2017, Karpacz, Poland
Award: Best experimental poster at 53rd Karpacz Winter School of Theoretical Physics
Abstract: Charm quarks are mainly created in hard processes at the beginning of heavy-ion collisions and can be used as a tool to study properties of the Quark-Gluon Plasma (QGP). The modification to D-meson production in heavy-ion collisions is sensitive to the energy loss of charm quarks in the QGP. The Heavy Flavor Tracker was installed at the STAR experiment in 2014 and enables the topological reconstruction of the decay vertices for open charm mesons. It significantly improves precision on charm meson measurements. Besides the measurement of D0, D± provides an additional handle and cross-check to study the interaction between charm quarks and the medium. In this poster, we present measurements of D± production in Au+Au collisions at 200 GeV. D± mesons are reconstructed topologically via the hadronic decay channel D± → K∓ π± π± from the data collected in 2014 with the Heavy Flavor Tracker. The invariant yield of D± mesons in the transverse momentum range of 2 - 10 GeV/c is extracted for 0 - 10% most central Au+Au collisions, and is found to be consistent with the D0 yield.
ALICE Measurements on ρ Photoproduction in Pb-Pb Ultra-peripheral Collisions
Author: David Horák (student - EJČF)
Conference: Quark Matter 2017
53rd Karpacz Winter School of Theoretical Physics
Date and location: 5. 2. - 11. 2. 2017, Chicago, USA
26. 2. - 4. 3. 2017, Karpacz, Poland
Abstract: The powerful photon fluxes of relativistic nuclei provide a possibility to study photonuclear and two-photon interactions in ultra-peripheral collisions where the nuclei do not overlap and no strong nuclear interactions occur. ALICE reports measurements on ρ^0 photoproduction cross sections in Pb-Pb UPC with data taken at √sNN = 2.76 TeV and new measurements with data taken at √sNN = 5.02 TeV. The mid-rapidity cross section of coherent ρ0 photoproduction is measured, and it is compared to theoretical models.
How to select events which evolved similarly?
Author: Boris Tomášik (EJČF), Renata Kopečná (student - EJČF)
Conference: Quark Matter 2017
Date and location: 5. 2. - 11. 2. 2017, Chicago, USA
Abstract: Events that started with very similar initial conditions should also evolve similarly and produce similar single-particle distributions of hadrons. This is natural consequence of hydrodynamic description of a collision. We present a novel method for data analysis. It compares the histograms of azimuthal hadron distributions from each event and organizes the events in such a way that those with similar histograms end-up placed close to each other. Those are the ones which underwent similar evolution. Such events can more easily be compared to theoretical simulations where all conditions can be controlled. We illustrate the method on data simulated by the AMPT model. Finally, we speculate about other possible applications of the method.
Performance of the ALICE secondary vertex b-tagging algorithm
Authors: Gyulnara Eyyubova (postdok - EJČF), Lukáš Kramárik (student - EJČF)
Conference: International Conference on New Frontiers in Physics 2015 (ICNFP 2015)
54th International Winter Meeting on Nuclear Physics
Date and location: 24. 8. - 30. 8. 2015, Kolymbari, Creee, Greece
25. 1. - 29. 1. 2016, Bormio, Italy
Award: Best poster at ICNFP 2015 award
Abstract: Jet reconstruction provides access to the kinematics of partons produced in the initial stage of heavy-ion collisions that later suffer energy loss in the medium via gluon radiation and elastic collisions. Reconstructed jets are therefore powerful tools to study the properties of the quark-gluon plasma (QGP). Theoretical models predict a dependence of the energy loss in the QGP on color charge and mass of the parton. Thus, the study of properties of beauty jets in comparison with that of light-flavour jets can reveal important information about the matter formed. b-tagging algorithms rely on the properties of B hadrons, i.e. their long lifetime, large mass and large multiplicity of decay products. In this poster the b-tagging algorithm based on secondary-vertex reconstruction is described. We present Monte Carlo based performance studies of the algorithm for charged jets reconstructed with ALICE tracking system. The tagging efficiency, rejection rate and the correction of the smearing effects of non-ideal detector response are presented. Finally, the performance expected for LHC Run 2 is briefly discussed.
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Nuclear effects in Drell-Yan production at the LHCAuthor: Michal Křelina (student - EJČF) + J. Nemchik, ... Conference: XXV international conference on ultrarelativistic heavy-ion collisions (Quark Matter 2015); XLV International Symposia on Multiparticle Dynamics (ISMD 2015); Date: 27.9.-3.10. 2015, Kobe, Japan 4.-9.10. 2015, Wildbad Kreuth, Germany Award: Franco Rimondi Association award for the best theoretical poster (at ISMD 2015) Abstract: Using the color dipole formalism we study production of Drell-Yan (DY) pairs in proton-nucleus interactions in the kinematic region corresponding to LHC experiments. Lepton pairs produced in a hard scattering are not accompanied with any final state interaction, either energy loss or absorption... |
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Systematic study of real photon and Drell-Yan pair production in p+A (d+A) interactionsAuthor: Michal Křelina (student - EJČF) + J. Nemchik, ... Conference: XXV international conference on ultrarelativistic heavy-ion collisions (Quark Matter 2015); XLV International Symposia on Multiparticle Dynamics (ISMD 2015); Date: 27.9.-3.10. 2015, Kobe, Japan 4.-9.10. 2015, Wildbad Kreuth, Germany Abstract: We investigate nuclear effects in production of Drell-Yan pairs and direct photons in p(d)-A collisions. For the first time, these effects are studied within the color dipole approach using path integral technique based on the Green function formalism which naturally incorporates the color transparency and quantum coherence effects... |
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Production of non-photonic electrons in central U+U collisionsAuthor: Katarína Gajdošová (studentka - EJČF) for the STAR collaboration Conference: XXV international conference on ultrarelativistic heavy-ion collisions (Quark Matter 2015); Date: 27.9.-3.10. 2015, Kobe, Japan Abstract: Since year 2000 the properties of Quark-Gluon Plasma (QGP) are being studied in ultrarelativistic heavy-ion collisions at the Relativistic Heavy Ion Collider (RHIC). Heavy quarks are created during early stages of a heavy-ion collision in hard processes before the system reaches thermal equilibrium and the QGP is formed. Their production is not affected by the QGP phase... |
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J/ψ production in U+U collisions at the STAR experimentAuthor: Jana Fodorová (student - EJČF) for the STAR collaboration Conference: European Physical Society Conference on High Energy Physics 2015 (EPS-HEP 2015) XXXIV Mazurian Lakes Conference on Physics (MLCP 2015) Date: 22.-29.7. 2015, Vienna, Austria 6.-13.9. 2015, Piasky, Poland Award: Elsevier Best Poster Award (at EPS-HEP 2015) Abstract: Quark-gluon plasma (QGP), a novel state of deconfined nuclear matter, has been studied in highenergy heavy-ion collisions at the Relativistic Heavy Ion Collider (RHIC). Due to the color screening of the quark-antiquark potential in the QGP the production of heavy quarkonia... |
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Dominant couplings in quantum networks with controlled interactionsAuthor: Jiří Maryška (student - MF) + J. Novotný, I. Jex Conference: 22nd Central European Workshop on Quantum Optics Date: 6.-10. 7. 2015, Warsaw, Poland Award: Best Poster Prize 2015 Abstract: We investigate the asymptotic dynamics of a finite network of qubits coupled by controlled interactions. The dynamics of the system is given by the RUO model [1]. We consider several cases of controlled interactions, namely two-qubit interactions and three-qubit interactions with one or two control qubits. The topology of the interactions (i.e. the allowed interactions between qubits) is chosen arbitrarily and it is described by... |