Conservation laws play a crucial role in the modeling of heavy-ion collisions, including the those for charges such as baryon number (B), strangeness (S), and electric charge (Q). In this study, we present a new 2+1 relativistic viscous hydrodynamic code called CCAKE which uses the Smoothed Particle Hydrodynamics (SPH) formalism to locally conserve BSQ charges, together with an extended description of the multi-dimensional equation of state (EoS) obtained from lattice Quantum Chromodynamics. Initial conditions for CCAKE are supplied by the ICCING model, which samples gluon splittings into quark anti-quark pairs to generate the initial BSQ charge distributions. We study correlations between the BSQ charges and find that local BSQ fluctuations remain finite during the evolution, with corresponding chemical potentials of (∼100–200 MeV) at freeze-out. We find that our framework produces reasonable multiplicities of identified particles and that ICCING has no significant effect on the collective flow of all charged particles nor of identified particles when only one particle of interest is considered. However, we show specifically for Pb+Pb collisions at the LHC √(s_NN)=5.02 TeV that ICCING does have an effect on collective flow of identified particles if two particles of interest are considered.

At the Large Hadron Collider it is possible to generate BSQ (baryon, strangeness, and electric) charge density fluctuations from gluon splittings into quark/anti-quark pairs, generated within the ICCING model. In this work, we implement BSQ charge dynamics in a fully integrated framework. We propagate these conserved charges within an upgraded version of the v-USPhydro hydrodynamic model, which conserves the BSQ densities exactly. Our hydrodynamic simulation uses the full 4D equation of state {T,μ_B,μ_S,μ_Q} from lattice Quantum Chromodynamics and includes decays from the Particle Data Group 2016+. We study the dynamical trajectories of fluid cells passing through the QCD phase diagram. We discuss future applications for this new framework.

At top collider energies where baryon stopping is negligible, the initial state of heavy ion collisions is overall charge neutral and predominantly composed of gluons. Nevertheless, there can also be significant local fluctuations of the baryon number, strangeness, and electric charge densities about zero, perturbatively corresponding to the production of quark/antiquark pairs. These previously ignored local charge fluctuations can permit the study of charge diffusion in the quark-gluon plasma (QGP), even at top collider energies. In this paper we present a new model denoted \code{iccing} (Initial Conserved Charges in Nuclear Geometry) which can reconstruct the initial conditions of conserved charges in the QGP by sampling a ($g \rightarrow q\bar{q}$) splitting probability over the initial energy density. We find that the new charge distributions generally differ from the bulk energy density; in particular, the strangeness distribution is significantly more eccentric than standard bulk observables and appears to be associated with the geometry of hot spots in the initial state. The new information provided by these conserved charges opens the door to studying a wealth of new charge- and flavor-dependent correlations in the initial state and ultimately the charge transport parameters of the QGP.

Heavy-ion collisions can be well described through relativistic viscous hydrodynamics, but questions still remain when hydrodynamics is applicable because the initial state may begin very far-from-equilibrium. Thus, a pre-equilibrium evolution phase is used to bridge the gap between the initial state and hydrodynamics. K$\phi$MP$\phi$ST is one such pre-equilibrium model that propagates the energy-momentum tensor by decomposing it into the background and fluctuations around that background, whose evolution is captured by Green's functions. We extend this formalism to include conserved charges and calculate the corresponding non-equilibrium Green's functions in the relaxation time approximation. The ICCING algorithm initializes conserved charges in the initial state by sampling $g \rightarrow q\bar{q}$ splitting probabilities and is, thus, perfectly positioned to implement Green's functions for charge propagation. We show that this method alters the initial state charge geometries and is applicable in central to mid-central collisions.

While it is well known that there is a significant amount of conserved charges in the initial state of nuclear collisions, the production of these due to gluon splitting has yet to be thoroughly investigated. The ICCING (Initial Conserved Charges in Nuclear Geometry) algorithm reconstructs these quark distributions, providing conserved strange, baryon, and electric charges, by sampling a given model for the g → qq¯ splitting function over the initial energy density, which is valid at top collider energies, even when µB = 0. The ICCING algorithm includes fluctuations in the gluon longitudinal momenta, a structure that supports the implementation of dynamical processes, and the c++ version is now open-source. A full analysis of parameter choices on the model has been done to quantify the effect these have on the underlying physics. We find there is a sustained difference across the different charges that indicates sensitivity to hot spot geometry.

At top collider energies where baryon stopping is negligible, the initial state of heavy-ion collisions is overall charge neutral and predominantly composed of gluons. Nevertheless, there can also be significant local fluctuations of the baryon number, strangeness, and electric charge densities about zero, perturbatively corresponding to the production of quark/antiquark pairs. These previously ignored local charge fluctuations can permit the study of charge diffusion in the quark-gluon plasma (QGP), even at top collider energies. In this paper we present a new model denoted ICCING (initial conserved charges in nuclear geometry) which can reconstruct the initial conditions of conserved charges in the QGP by sampling a (g -> q (q) over bar) splitting probability over the initial energy density. We find that the new charge distributions generally differ from the bulk energy density; in particular, the strangeness distribution is significantly more eccentric than standard bulk observables and appears to be associated with the geometry of hot spots in the initial state. The new information provided by these conserved charges opens the door to studying a wealth of new charge- and flavor-dependent correlations in the initial state and ultimately the charge transport parameters of the QGP.

The initial state is one of the greatest uncertainties in heavy-ion collisions. A model-agnostic approach is taken in the phenomenological Trento framework which constrains parameters using Bayesian analysis. However, the color-glass condensate (CGC) effective theory predicts initial energy densities that lie outside the recent Bayesian analyses due, in part, to the assumption in Trento of event-by-event multiplicity fluctuations following a Γ distribution. We compare the Trento-preferred √(T_AT_B) scaling to CGC-like T_AT_B scaling coupled with log-normal fluctuations in AuAu and dAu collisions and find there is a significant impact on the multiplicity distributions and on the eccentricities, which may affect the extraction of viscosity in small systems.

Recent measurements have established the sensitivity of ultracentral heavy-ion collisions to the deformation parameters of nonspherical nuclei. In the case of Xe-129 collisions, a quadrupole deformation of the nuclear profile led to an enhancement of elliptic flow in the most central collisions. In Pb-208 collisions a discrepancy exists in similar centralities, where either elliptic flow is overpredicted or triangular flow is underpredicted by hydrodynamic models; this is known as the v(2)-to-v(3) puzzle in ultracentral collisions. Motivated by low-energy nuclear structure calculations, we consider the possibility that Pb-208 nuclei could have a pear-shape deformation (octupole), which has the effect of increasing triangular flow in central PbPb collisions. Using the recent data from ALICE and ATLAS, we reexamine the v(2)-to-v(3) puzzle in ultracentral collisions, including new constraints from recent measurements of the triangular cumulant ratio v(3){4}/v(3){2} and comparing two different hydrodynamic models. We find that while an octupole deformation would slightly improve the ratio between v(2) and v(3), it is at the expense of a significantly worse triangular flow cumulant ratio. In fact, the latter observable prefers no octupole deformation, with beta(3) less than or similar to 0.0375 for Pb-208, and is therefore consistent with the expectation for a doubly-magic nucleus even at top collider energies. The v(2)-to-v(3) puzzle remains a challenge for hydrodynamic models.

At top collider energies where baryon stopping is negligible, the initial state of heavy ion collisions is overall charge neutral and predominantly composed of gluons. Nevertheless, there can also be significant local fluctuations of the baryon number, strangeness, and electric charge densities about zero, perturbatively corresponding to the production of quark/antiquark pairs. These previously ignored local charge fluctuations can permit the study of charge diffusion in the quark-gluon plasma (QGP), even at top collider energies. In this paper we present a new model denoted ICCING (Initial Conserved Charges in Nuclear Geometry) which can reconstruct the initial conditions of conserved charges in the QGP by sampling a (g → qq̅) splitting probability over the initial energy density. We find that the new charge distributions generally differ from the bulk energy density; in particular, the strangeness distribution is significantly more eccentric than standard bulk observables and appears to be associated with the geometry of hot spots in the initial state. The new information provided by these conserved charges opens the door to studying a wealth of new charge- and flavor-dependent correlations in the initial state and ultimately the charge transport parameters of the QGP.

Technical communication is essential for a career in physics, but communication skills are often not explicitly taught in physics undergraduate curricula. As a starting point for curricular integration, we investigated where and how writing is currently occurring in the core undergraduate physics courses at a large, public university. We examined course materials to identify where writing is explicitly or implicitly referenced, categorize the genres that were assigned, and characterize writing concepts that were represented in the course materials. Analyzing course materials allowed us to identify a wide range of activities and assignments related to writing. We observe that implicit references to writing are prevalent, writing activities are weighted toward upper-level classes, and the most common genres are related to laboratory activities. Writing concepts that occur frequently in upper-level laboratory courses correlate to disciplinary values of precision and clarity, while concepts of novelty and evidence are infrequent. This type of assessment can form the basis for discussing where and how writing is showing up in our courses, allowing us to be more deliberate about how our curricula develop students' communication skills.