Sub-jet structure as a discriminating quenching probe

In this work, we propose a new class of jet substructure observables which, unlike fragmentation functions, are largely insensitive to the poorly known physics of hadronization. We show that sub-jet structures provide us with a large discriminating power between different jet quenching Monte Carlo implementations.Comment: 4 pages, 3 figures, Quarks Matter conference 201

Inclusive cross section and correlations of fully reconstructed jets in 200 GEV Au+Au and p+p collisions

We present an experimental study of full jet reconstruction in the high multiplicity environment of heavy ion collisions, utilizing 200 GeV p+p and central Au+Au data measured by STAR. Inclusive differential jet production cross sections and ratios are reported, as well as high-pT hadron-jet coincidences.Comment: 4 pages, 5 figures - To appear in the conference proceedings for Quark Matter 2009, March 30 - April 4, Knoxville, Tennesse

Explainable machine learning of the underlying physics of high-energy particle collisions

We present an implementation of an explainable and physics-aware machine learning model capable of inferring the underlying physics of high-energy particle collisions using the information encoded in the energy-momentum four-vectors of the final state particles. We demonstrate the proof-of-concept of our White Box AI approach using a Generative Adversarial Network (GAN) which learns from a DGLAP-based parton shower Monte Carlo event generator. We show, for the first time, that our approach leads to a network that is able to learn not only the final distribution of particles, but also the underlying parton branching mechanism, i.e. the Altarelli-Parisi splitting function, the ordering variable of the shower, and the scaling behavior. While the current work is focused on perturbative physics of the parton shower, we foresee a broad range of applications of our framework to areas that are currently difficult to address from first principles in QCD. Examples include nonperturbative and collective effects, factorization breaking and the modification of the parton shower in heavy-ion, and electron-nucleus collisions.Comment: 11 pages, 4 figure

Quantum simulation of non-equilibrium dynamics and thermalization in the Schwinger model

We present simulations of non-equilibrium dynamics of quantum field theories on digital quantum computers. As a representative example, we consider the Schwinger model, a 1+1 dimensional U(1) gauge theory, coupled through a Yukawa-type interaction to a thermal environment described by a scalar field theory. We use the Hamiltonian formulation of the Schwinger model discretized on a spatial lattice. With the thermal scalar fields traced out, the Schwinger model can be treated as an open quantum system and its real-time dynamics are governed by a Lindblad equation in the Markovian limit. The interaction with the environment ultimately drives the system to thermal equilibrium. In the quantum Brownian motion limit, the Lindblad equation is related to a field theoretical Caldeira-Leggett equation. By using the Stinespring dilation theorem with ancillary qubits, we perform studies of both the non-equilibrium dynamics and the preparation of a thermal state in the Schwinger model using IBM's simulator and quantum devices. The real-time dynamics of field theories as open quantum systems and the thermal state preparation studied here are relevant for a variety of applications in nuclear and particle physics, quantum information and cosmology.Comment: 18 pages, 8 figure

Quantum simulation of open quantum systems in heavy-ion collisions

We present a framework to simulate the dynamics of hard probes such as heavy quarks or jets in a hot, strongly-coupled quark-gluon plasma (QGP) on a quantum computer. Hard probes in the QGP can be treated as open quantum systems governed in the Markovian limit by the Lindblad equation. However, due to large computational costs, most current phenomenological calculations of hard probes evolving in the QGP use semiclassical approximations of the quantum evolution. Quantum computation can mitigate these costs, and offers the potential for a fully quantum treatment with exponential speedup over classical techniques. We report a simplified demonstration of our framework on IBM Q quantum devices, and apply the Random Identity Insertion Method (RIIM) to account for CNOT depolarization noise, in addition to measurement error mitigation. Our work demonstrates the feasibility of simulating open quantum systems on current and near-term quantum devices, which is of broad relevance to applications in nuclear physics, quantum information, and other fields

Centrality evolution of the charged-particle pseudorapidity density over a broad pseudorapidity range in Pb-Pb collisions at root s(NN)=2.76TeV

Peer reviewe

Overview of results from ALICE

ALICE is a dedicated experiment for measurements of heavy-ion collisions at the Large Hadron Collider (LHC). A wealth of experimental data recorded in 2010, 2011 and 2012 suggests that a strongly interacting de-confined medium is created in collisions of lead ions at a centre-of-mass energy = 2.76 TeV. In order to quantify the properties of this hot and dense matter, measurements were performed in smaller systems, such as proton-proton and proton-lead, where effects related to the medium are expected to be negligible. We present an overview of recent measurements of particle production and particle correlations in protonproton, Pb-Pb and p-Pb collisions at the LHC by ALICE Collaboration

ALICE Highlights at Hard Probes 2015

A review of selected measurements by the ALICE Collaboration discussed at the Hard Probes 2015 conference is given. The production of J/ ψ as well as long-range two particle correlations in proton-lead collisions at s=5.02 TeV are discussed. The parton energy loss in a quark-gluon plasma created in Pb–Pb collisions at s=2.76 TeV is discussed based on the measurements of semi-inclusive charged particle jets correlated with a high- pT hadron, the nuclear modification factor ( R AA ) for identified hadrons and D-mesons. Moreover, D-meson R AA is compared with the R AA of non-prompt J/ ψ measured by the CMS Collaboration showing that the parton energy loss depends on the mass of the parton. In addition, further studies of J/ ψ production in peripheral nuclear collisions show an excess of low momenta mesons beyond the expectation for purely hadronic production