New constraints for QCD matter from improved Bayesian parameter estimation in heavy-ion collisions at LHC

The transport properties of quark-gluon plasma created in relativistic heavy-ion collisions are quantified by an improved global Bayesian analysis using the CERN Large Hadron Collider Pb-Pb data at root s(NN) = 2.76 and 5.02 TeV. The results show that the uncertainty of the extracted transport coefficients is significantly reduced by including new sophisticated collective flow observables from two collision energies for the first time. This work reveals the stronger temperature dependence of specific shear viscosity, a lower value of specific bulk viscosity, and a higher hadronization switching temperature than in the previous studies. The sensitivity analysis confirms that the precision measurements of higher-order harmonic flow and their correlations are crucial in extracting accurate values of the transport properties. (C) 2022 The Author(s). Published by Elsevier B.V.Peer reviewe

Charge dependent azimuthal correlations in Pb--Pb collisions at sNN=2.76\sqrt{s_{NN}} = 2.76 TeV

Separation of charges along the extreme magnetic field created in non-central relativistic heavy--ion collisions is predicted to be a signature of local parity violation in strong interactions. We report on results for charge dependent two particle azimuthal correlations with respect to the reaction plane for Pb--Pb collisions at $\sqrt{s_{NN}} = 2.76$ TeV recorded in 2010 with ALICE at the LHC. The results are compared with measurements at RHIC energies and against currently available model predictions for LHC. Systematic studies of possible background effects including comparison with conventional (parity-even) correlations simulated with Monte Carlo event generators of heavy--ion collisions are also presented.Comment: Published in the proceedings of "Quark Matter 2011", Annecy-Franc

A City in Common: A Framework to Orchestrate Large-scale Citizen Engagement around Urban Issues

Citizen sensing is an approach that develops and uses lightweight technologies with local communities to collect, share and act upon data. In doing so it enables them to become more aware of how they can tackle local issues. We report here on the development and uptake of the 'City- Commons Framework for Citizen Sensing', a conceptual model that builds on Participatory Action Research with the aim of playing an integrating role: outlining the processes and mechanisms for ensuring sensing technologies are co-designed by citizens to address their concerns. At the heart of the framework is the idea of a city commons: a pool of community-managed resources. We discuss how the framework was used by communities in Bristol to measure and monitor the problem of damp housing

Fluctuation and flow probes of early-time correlations in relativistic heavy ion collisions

Fluctuation and correlation observables are often measured using multi-particle correlation methods and therefore mutually probe the origins of genuine correlations present in multi-particle distribution functions. We investigate the common influence of correlations arising from the spatially inhomogeneous initial state on multiplicity and momentum fluctuations as well as flow fluctuations. Although these observables reflect different aspects of the initial state, taken together, they can constrain a correlation scale set at the earliest moments of the collision. We calculate both the correlation scale in an initial stage Glasma flux tube picture and the modification to these correlations from later stage hydrodynamic flow and find quantitative agreement with experimental measurements over a range of collision systems and energies.Comment: Proceedings of the 28th Winter Workshop on Nuclear Dynamics, Dorado del Mar, Puerto Rico, April 7-14, 201

Ultra-relativistic nuclear collisions: event shape engineering

The evolution of the system created in a high energy nuclear collision is very sensitive to the fluctuations in the initial geometry of the system. In this letter we show how one can utilize these large fluctuations to select events corresponding to a specific initial shape. Such an "event shape engineering" opens many new possibilities in quantitative test of the theory of high energy nuclear collisions and understanding the properties of high density hot QCD matter.Comment: 6 pages, 5 figure

Anisotropic flow of charged particles at sNN=2.76\mathbf{\sqrt{s_{NN}} = 2.76} TeV measured with the ALICE detector

Measurements of anisotropic flow in heavy-ion collisions provide evidence for the creation of strongly interacting matter which appears to behave as an almost ideal fluid. Anisotropic flow signals the presence of multiple interactions and is very sensitive to the initial spatial anisotropy of the overlap region in non-central heavy-ion collisions. In this article we report measurements of elliptic $v_2$, triangular $v_3$, quadrangular $v_4$ and pentagonal $v_5$ flow. These measurements have been performed with 2- and multi-particle correlation techniques.Comment: 4 pages, 4 figures, Quark Matter 2011 proceeding

Anisotropic flow at the LHC measured with the ALICE detector

The ALICE detector at the LHC recorded first Pb-Pb collisions at 2.76 TeV in November and December of 2010. We report on the measurements of anisotropic flow for charged and identified particles. From the comparison with measurements at lower energies and with model predictions we find that the system created at these collision energies is described well by hydrodynamical model calculations and behaves like an almost perfect fluid.Comment: 8 pages, 16 figures, plenary talk at Quark Matter 2011, May 23rd-28th 2011, Annecy, Franc

Classical approximation to quantum cosmological correlations

We investigate up to which order quantum effects can be neglected in calculating cosmological correlation functions after horizon exit. As a toy model, we study $\phi^3$ theory on a de Sitter background for a massless minimally coupled scalar field $\phi$. We find that for tree level and one loop contributions in the quantum theory, a good classical approximation can be constructed, but for higher loop corrections this is in general not expected to be possible. The reason is that loop corrections get non-negligible contributions from loop momenta with magnitude up to the Hubble scale H, at which scale classical physics is not expected to be a good approximation to the quantum theory. An explicit calculation of the one loop correction to the two point function, supports the argument that contributions from loop momenta of scale $H$ are not negligible. Generalization of the arguments for the toy model to derivative interactions and the curvature perturbation leads to the conclusion that the leading orders of non-Gaussian effects generated after horizon exit, can be approximated quite well by classical methods. Furthermore we compare with a theorem by Weinberg. We find that growing loop corrections after horizon exit are not excluded, even in single field inflation.Comment: 44 pages, 1 figure; v2: corrected errors, added references, conclusions unchanged; v3: added section in which we compare with stochastic approach; this version matches published versio