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| 3. |
- Andrews, Harry Arthur, et al.
(författare)
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Novel tools and observables for jet physics in heavy-ion collisions
- 2020
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Ingår i: Journal of Physics G: Nuclear and Particle Physics. - : IOP Publishing. - 0954-3899 .- 1361-6471. ; 47:6
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Tidskriftsartikel (refereegranskat)abstract
- Studies of fully-reconstructed jets in heavy-ion collisions aim at extracting thermodynamical and transport properties of hot and dense QCD matter. Recently, a plethora of new jet substructure observables have been theoretically and experimentally developed that provide novel precise insights on the modifications of the parton radiation pattern induced by a QCD medium. This report, summarizing the main lines of discussion at the 5th Heavy Ion Jet Workshop and CERN TH institute 'Novel tools and observables for jet physics in heavy-ion collisions' in 2017, presents a first attempt at outlining a strategy for isolating and identifying the relevant physical processes that are responsible for the observed medium-induced jet modifications. These studies combine theory insights, based on the Lund parton splitting map, with sophisticated jet reconstruction techniques, including grooming and background subtraction algorithms.
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| 4. |
- Apolinário, Liliana, et al.
(författare)
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Time reclustering for jet quenching studies
- 2021
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Ingår i: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 81:6
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Tidskriftsartikel (refereegranskat)abstract
- The physics program of ultra-relativistic heavy-ion collisions at the Large Hadron Collider (LHC) and Relativistic Heavy-Ion Collider (RHIC) has brought a unique insight into the hot and dense QCD matter created in such collisions, the Quark-Gluon Plasma (QGP). Jet quenching, a collection of medium-induced modifications of the jets’ internal structure that occur through their development in dense QCD matter, has a unique potential to assess the time structure of the produced medium. In this work, we perform an exploratory study to identify jet reclustering tools that can potentiate future QGP tomographic measurements with jets at current energies. Our results show that by using the inverse of formation time to obtain the jet clustering history, one can identify more accurately the time structure of QCD emissions inside jets, even in the presence of jet quenching.
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| 6. |
- Guerrero-Rodríguez, Pablo, et al.
(författare)
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Exploring the time axis within medium-modified jets
- 2024
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Ingår i: Proceedings of Science. ; 438
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Konferensbidrag (refereegranskat)abstract
- The fast evolution of the QGP makes its interaction with jets an inherently time-dependent process. However, this crucial dimension is missing from traditional jet quenching measurements, which hence provide a mere average quantification of the medium properties. Jet substructure observables provide an effective strategy to access the QGP time structure. By identifying the recursive steps of a novel jet clustering algorithm (the τ algorithm) with the sequence of branchings of the parton shower, it is possible to obtain an adequate proxy for a time axis within the medium. In this work we apply this technique to label jets according to their formation time and opening angle, defining populations with enhanced sensitivity to quenching effects. In doing so, we show how the formation time-based sampling of jets minimizes the bias of their initial transverse momentum spectrum.
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| 8. |
- Kurkela, Aleksi, et al.
(författare)
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AMY Lorentz invariant parton cascade : the thermal equilibrium case
- 2024
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Ingår i: European Physical Journal C. - 1434-6044. ; 84:1
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Tidskriftsartikel (refereegranskat)abstract
- We introduce the parton cascade Alpaca, which evolves parton ensembles corresponding to single events according to the effective kinetic theory of QCD at high temperature formulated by Arnold, Moore and Yaffe by explicitly simulating elastic scattering, splitting and merging. By taking the ensemble average over many events the phase space density (as evolved by the Boltzmann equation) is recovered, but the parton cascade can go beyond the evolution of the mean because it can be turned into a complete event generator that produces fully exclusive final states including fluctuations and correlations. The parton cascade does not require the phase space density as input (except for the initial condition at the starting time). Rather, effective masses and temperature, which are functions of time and are defined as integrals over expressions involving the distribution function, are estimated in each event from just the parton ensemble of that event. We validate the framework by showing that ensembles sampled from a thermal distribution stay in thermal equilibrium even after running the simulation for a long time. This is a non-trivial result, because it requires all parts of the simulation to intertwine correctly.
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| 9. |
- Milhano, José Guilherme, et al.
(författare)
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Improved background subtraction and a fresh look at jet sub-structure in JEWEL
- 2022
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Ingår i: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 82:11
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Tidskriftsartikel (refereegranskat)abstract
- Interactions of hard partons in the Quark Gluon Plasma (QGP) created with relativistic heavy ion collisions lead to characteristic modifications of the internal structure of reconstructed jets. A large part of the observed jet sub-structure modifications stem from the QGP’s response to energy and momentum deposited by hard partons. Good control over medium response in theoretical calculations is thus instrumental to a quantitative understanding of medium modified (quenched) jets in heavy ion collisions. We present an improved way of handling the medium response in the jet quenching model Jewel and present results for a variety of jet sub-structure observables. The new recoil handling is more versatile and robust than the old scheme, giving a better control over many observables and, in particular, greatly improves the description of the jet mass.
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| 10. |
- Törnkvist, Robin, et al.
(författare)
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Small systems and the single-hit approximation in the AMY parton cascade ALPACA
- 2024
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Ingår i: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - 0370-2693. ; 856
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Tidskriftsartikel (refereegranskat)abstract
- Understanding how momentum anisotropies arise in small collision systems is important for a quantitative understanding of collectivity in terms of QCD dynamics in small and large collision systems. In this letter we present results for small collision systems from the newly developed parton cascade ALPACA, which faithfully encodes the AMY effective kinetic theory. ALPACA reproduces quantitatively previously known results from a calculation in the single-hit approximation for small values of the coupling. We discuss in detail how such a comparison is to be carried out. Particularly at larger coupling a generic difference between the two approaches becomes apparent, namely that in parton cascades particles interact over a finite distance while in direct integrations of the Boltzmann equation the interactions are local. This leads to quantitative differences in the extracted values for the elliptic flow coefficient. These discrepancies appear in situations where the mean free path is not large compared to the interaction time and the applicability of kinetic theory is thus questionable.
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| 11. |
- Zapp, Korinna, et al.
(författare)
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A Monte Carlo model for 'jet quenching'
- 2009
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Ingår i: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 60:4, s. 617-632
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Tidskriftsartikel (refereegranskat)abstract
- We have developed the Monte Carlo simulation program JEWEL 1.0 (Jet Evolution With Energy Loss), which interfaces a perturbative final-state parton shower with medium effects occurring in ultra-relativistic heavy-ion collisions. This is done by comparing for each jet fragment the probability of further perturbative splitting with the density-dependent probability of scattering with the medium. A simple hadronisation mechanism is included. In the absence of medium effects, we validate JEWEL against a set of benchmark jet measurements. For elastic interactions with the medium, we characterise not only the medium-induced modification of the jet, but also the jet-induced modification of the medium. Our main physical result is the observation that collisional and radiative medium modifications lead to characteristic differences in the jet fragmentation pattern, which persist above a soft background cut. We argue that this should allow one to disentangle collisional and radiative parton energy loss mechanisms by measuring the n-jet fraction or a class of jet shape observables.
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| 13. |
- Zapp, Korinna C.
(författare)
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Jet energy loss and equilibration
- 2017
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Ingår i: Proceedings, 26th International Conference on Ultra-relativistic Nucleus-Nucleus Collisions (Quark Matter 2017): Chicago, Illinois, USA, February 5-11, 2017. - : Elsevier BV. ; A967, s. 81-88
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Konferensbidrag (refereegranskat)
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| 14. |
- Zapp, Korinna, et al.
(författare)
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Heavy quark energy loss through soft QCD scattering in the QGP
- 2007
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Ingår i: International Journal of Modern Physics E. - 0218-3013. ; 16:7-8, s. 2072-2078
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Tidskriftsartikel (refereegranskat)abstract
- A strong suppression of non-photonic electrons in Au+Au collisions is observed at Rhic. This is in disagreement with the expected dominance of the energy loss via gluon radiation, which predicts a much weaker suppression of heavy flavours due to the dead cone effect. However, collisional energy loss is also important, as demonstrated recently by the Soft Colour Interaction Jet (quenching model. Based on this model we show that collisional energy loss of charm quarks gives a suppression of electrons of the observed magnitude, but the contribution from beauty decays, which dominates at intermediate and large p(perpendicular to), results in a somewhat weaker overall suppression of electrons than observed.
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| 15. |
- Zapp, Korinna, et al.
(författare)
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Jet quenching from soft QCD scattering in the quark-gluon plasma
- 2006
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Ingår i: Physics Letters B. ; 637:3, s. 179-184
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Tidskriftsartikel (refereegranskat)abstract
- We show that partons traversing a quark-gluon plasma can lose substantial amounts of energy also by scatterings, and not only through medium-induced radiation as mainly considered previously. Results from Monte Carlo simulations of soft interactions of partons, emerging from a hard scattering, through multiple elastic scatterings on gluons in an expanding relativistic plasma show a sizeable jet quenching which can account for a substantial part of the effect observed in RHIC data.
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| 16. |
- Zapp, Korinna
(författare)
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The role of initial state radiation in quenched jets
- 2022
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Ingår i: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 835
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Tidskriftsartikel (refereegranskat)abstract
- Jet quenching in heavy ion collisions and in particular the sub-structure of quenched jets are promising tools for investigating the microscopic processes underlying jet quenching and the background medium's response to energy and momentum depositions. A quantitative understanding of the data can, however, be complicated by the presence of initial state radiation in reconstructed jets. Using an extended version of JEWEL the effect of initial state radiation on different jet observables is studied in proton-proton and heavy ion collisions. It is shown that, depending on the observable and the jet radius, the initial state contributions can be sizable. Some general insights into when sizable effects can be expected also emerges.
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