Past Seminars


In this talk, I will discuss how the collective dynamics around second-order phase transitions in the QCD phase diagram can be understood through universality. Since the critical dynamics in the vicinity of such transitions is universal, one may study a simpler system from the same "dynamic universality class" instead. I will focus on two particular second-order transitions: the critical point at finite baryon chemical potential and quark masses, and the chiral phase transition in the two-flavor chiral limit. In this order, I will review the argument by Son and Stephanov, and the one by Rajagopal and Wilczek, respectively, for the associated dynamic universality classes. In the Halperin-Hohenberg classification these are Model H (the one of the liquid-gas critical point in a pure fluid) and Model G (the one of a Heisenberg antiferromagnet), respectively. In both cases, I will present results for dynamic critical exponents in various spatial dimensions obtained from a novel real-time formulation of the functional renormalization group for systems with reversible mode couplings. In Model G, I will present a dynamic scaling function that describes the universal momentum and temperature dependence of the diffusion coefficient of iso-(axial-)vector charge densities in the symmetric phase.

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The internal structure of hadrons like proton and neutron is possible thanks to the so-called factorization theorems, which allow to disentangle the process specific information from the intrinsic details about the particles structure. The knowledge about the three-dimensional motion of quarks and gluons inside a hadron is captured by the transverse momentum distributions or TMDs. Extracting these distribution is an extremely hard task which involves the interplay of perturbative QCD, modeling and fitting. We present a novel approach to TMD phenomenology that heavily relies on known theoretical constraints to aid in the modeling of a parametrization that smoothly interpolates between the perturbative and nonperturbative regions and that is consistent with renormalization group evolution. Using this so-called Hadron Structure Oriented (HSO) approach, we present a practical implementation focusing on low-to-moderate energy data in the Drell-Yan process to extract reliable TMDs, achieving successful postdictions at higher energies.

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Precision laser spectroscopy of simple atomic systems offers a robust test of the Standard Model and serves as a sensitive tool for exploring its potential extensions. Muonic atoms, systems composed of a muon bound to a nucleus, have recently taken center stage in precision physics. The significantly greater mass of the muon, approximately 200 times that of the electron, enables muonic atoms to probe nuclear structure effects with higher precision compared to ordinary atoms. Over the past decade, this capability has led to a remarkable improvement in determining the charge radii of the proton, deuteron, and helium nuclei.

The difference between the charge radii of the helion (he-3 nucleus) and the alpha-particle (he-4 nucleus) has been characterized by long standing questions, recently spotlighted in the 3.6 sigma discrepancy between extractions from ordinary atoms and those from muonic atoms.

In this seminar, I will present a calculation of the nuclear structure effects on the Lamb-shift of muonic helium ions based on the chiral effective field theory. With the incorporation of the new nuclear structure inputs, the helium isotope-shift puzzle is not explained. We conclude that the observed discrepancy does not originate from the theoretical description of nuclear matrix elements.

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The rapid neutron capture process (r-process) is the most important mechanism for the synthesis of about half of the elements heavier than iron. It occurs in an environment with relatively high temperatures and high neutron densities. The abundances of the elements created by the r-process strongly depend on several nuclear inputs like masses, neutron capture rates, β-decay rates, and β-delayed neutron emission probabilities at the waiting point nuclei. Among them, the β-decay process plays a crucial role in the r-process. We have investigated various nuclear β-decay properties of N = 126,125 isotones with proton numbers Z = 52 − 79 within the framework of the nuclear shell model. This comprehensive analysis considered both Gamow-Teller (GT) and first-forbidden (FF) transitions to evaluate β-decay rates. We have found that including FF transitions in addition to GT transitions is essential, as they significantly impact the total β-decay half-lives near Z = 82. Additionally, we systematically analyzed the GT strength distributions as a function of proton number. We have observed that the GT strengths at low excitation energies are rather strong on the proton deficient side due to the increasing number of proton holes in the proton 0h_{11/2} orbit, which accelerates GT decay. This investigation aims to provide detailed information on β-decay proper- ties around A ≈ 195 to understand the distribution of the third r-process abundance peak.

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A Hamiltonian lattice formulation of lattice gauge theories opens the possibility for quantum simulations of the non-perturbative dynamics of QCD. By parametrizing the gauge invariant Hilbert space in terms of plaquette degrees of freedom, we show how the Hilbert space and interactions can be expanded in inverse powers of Nc. At leading order in this expansion, the Hamiltonian simplifies dramatically, both in the required size of the Hilbert space as well as the type of interactions involved. Adding a truncation of the resulting Hilbert space in terms of local energy states we give explicit constructions that allow simple representations of SU(3) gauge fields on qubits and qutrits to leading order in large N. This enabled a simulation of the real time dynamics of a SU(3) lattice gauge theory on a 8x8 lattice with a superconducting quantum processor.

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The structure of low-density nuclear matter is of great importance to the physics of neutron star crusts. One of the most significant aspects of this structure is the transition from roughly spherical neutron rich nuclei to uniform matter. Models for both of these extremes exist but the transition is less easily understood. In this presentation I will show that using variational Monte Carlo to optimize neural-network quantum states, based on a Pfaffian architecture, I find ground states which are improvements on standard auxiliary field diffusion Monte Carlo ground state calculations within this density region. This is especially true for the lowest densities where the AFDMC results dramatically under-predict clustering. The results to be shown come from calculations at several densities and proton fractions using a pionless effective field theory Hamiltonian. From these results I will show predictions for clustering, symmetry energy, and proton fraction for the beta-equilibrated ground state.

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Ab initio nuclear structure theory aims to predict the structure of atomic nuclei from "first principles," employing systematically improvable approximations in the determination of inter-nucleon potentials and in the solution of the many-body Schrödinger equation. Over the past decade, the in-medium similarity renormalization group (IMSRG) has been established as a powerful and flexible method to approaching the many-body problem. The IMSRG solves for a unitary transformation that approximately diagonalizes the Hamiltonian (or produces an effective interaction within a valence space for shell model applications). This approximation can be systematically relaxed by including higher-body operators in the many-body solution. Recently, we have worked on extending the IMSRG to the next order, the IMSRG(3) with normal-ordered three-body operators. The IMSRG(3) truncation is formally more involved and also computationally substantially more expensive than the IMSRG(2), the well-established truncation used in applications so far. We have shown, however, that the most expensive terms in the IMSRG(3) can be truncated with little effect on the improved accuracy of the many-body solution, allowing the IMSRG(3) to be approximated at a reasonable computational cost comparable to other high fidelity nuclear structure methods like coupled cluster with approximate triples (CCSDT-1).

A key advantage of the IMSRG is its ability to interface with the shell model via the derivation of an effective valence space Hamiltonian (and consistent effective operators). This allows the IMSRG to describe open-shell nuclei easily, and this has been used to perform comprehensive studies of all isotopes up to iron. In calcium isotopes, the IMSRG(2) describes ground-state energies quite well, but struggles to quantitatively reproduce the spectra of calcium-48, a doubly-magic nucleus. Additionally, the trends in the charge radii of neutron-rich calcium are so far unexplained by ab initio methods. I will discuss the improved description of the structure of neutron-rich calcium isotopes made possible by the IMSRG(3) and what this means for existing discrepancies to experimental trends.


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Quantum simulation holds promise of enabling a complete description of high-energy scattering processes rooted in gauge theories of the Standard Model. A first step in such simulations is preparation of interacting hadronic wave packets. To create the wave packets, one typically resorts to adiabatic evolution to bridge between wave packets in the free theory and those in the interacting theory, rendering the simulation resource intensive. In this work, we construct a wave-packet creation operator directly in the interacting theory to circumvent adiabatic evolution, taking advantage of resource-efficient schemes for ground-state preparation, such as variational quantum eigensolvers. By means of an ansatz for bound mesonic excitations in confining gauge theories, which is subsequently optimized using classical or quantum methods, we show that interacting mesonic wave packets can be created efficiently and accurately using digital quantum algorithms that we develop. Specifically, we obtain high-fidelity mesonic wave packets in the Z2 and U(1) lattice gauge theories coupled to fermionic matter in 1+1 dimensions. Our method is applicable to both perturbative and non-perturbative regimes of couplings. The wave-packet creation circuit for the case of the Z2 lattice gauge theory is built and implemented on the Quantinuum H1-1 trapped-ion quantum computer using 13 qubits and up to 308 entangling gates. The fidelities agree well with classical benchmark calculations after employing a simple symmetry-based noise-mitigation technique. This work serves as a step toward quantum computing scattering processes in quantum chromodynamics.


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During a core-collapse supernova explosion, most of the energy released is carried away by the emitting neutrinos. To understand the dynamics of this explosion, we have to treat the neutrino transport in completion. However, the extreme conditions inside the supernova core allow neutrinos not only to frequently interact with matter but also with each other, which makes it a highly non-linear many-body problem with 10^58 neutrinos. Even with state-of-the-art computational methods such as tensor networks, this problem cannot be solved on classical computers. In fact, these simulations become even more complicated when a more realistic scenario with three active flavors is considered. Quantum simulations are a more natural way to simulate such quantum many-body systems. Simulations for collective neutrino oscillations on quantum computers have already been attempted but only few-neutrino systems could be simulated in such full-fledged quantum computations because of quantum hardware limitations. However, in the current noisy intermediate-scale quantum era, it is more efficient to employ a hybrid quantum-mechanical algorithm to solve this problem. In this talk, I will discuss my attempts to employ the hybrid quantum-classical algorithm to simulate collective neutrino oscillation dynamics and present some recent results on the measure of quantum entanglement. We have also made the first attempts to incorporate all three flavors in the neutrino many-body problem and found several interesting features about the generation of quantum entanglement in such a system. I will also talk about this more realistic three-flavor scenario and the potential utilization of qutrit-based quantum computers to simulate this case.

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Lattice Quantum Chromodynamics (LQCD) stands out as one of the most successful methods for non-perturbative predictions in high-energy physics. Despite its achievements, traditional computational techniques face limitations due to the notorious sign problem when dealing with dynamic observables in physical time or at non-vanishing chemical potential. Our recent work focuses on the complex Langevin (CL) method, which aims to overcome these challenges by generalizing the Stochastic Quantization approach. Successfully applied to real-time SU(N) gauge theories on a 1+3 dimensional lattice, CL enables us to calculate unequal-time correlation functions directly from first principles. These developments may pave the way for future applications, including the computation of spectral functions and transport coefficients crucial for understanding the quark-gluon plasma (QGP).

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We employ a model based on nucleonic and mesonic degrees of freedom to describe cold and dense matter, in the region of the chiral phase transition, at zero net isospin. The model can describe both chirally broken and symmetric nucleons, and is in some sense complementary to the Nambu-Jona-Lasinio model which describes chirally broken/symmetric quarks. This model has been previously used to calculate the surface tension on a nuclear/quark matter interface, to build mixed (pasta-like) phases, and to describe hyperonic/strange matter in neutron stars. In this work we discuss the competition between isotropic and anisotropic phases at intermediate densities and zero temperature. Anisotropic phases have been extensively studied in quark models of dense matter, but equivalent progress is lacking in models using nucleonic degrees of freedom. When such models are employed, the nucleonic Dirac sea contribution to the pressure is neglected, while we show that including it produces a significant effect. Assuming isotropy, the model exhibits a chiral phase transition which is of second order in the chiral limit and becomes a crossover in the case of a realistic pion mass. This observation crucially depends on the presence of the nucleonic sea; if one neglects it, the transition becomes a first order. Allowing for an anisotropic phase in the form of a chiral density wave, we observe the smooth crossover being disrupted. We identify the regions in the parameter space of the model where a chiral density wave is energetically preferred. A high-density re-appearance of the chiral density wave with unphysical behavior, which is present in previous studies, is avoided by choosing a suitable renormalization scheme. A nonzero pion mass tends to disfavor the anisotropic phase compared to the chiral limit and we find that, within our model, the chiral density wave is only realized for baryon densities of at least about 6 times nuclear saturation density. Future works will focus on extending the study for neutron star conditions.

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In this ongoing five-year research, rotating Anti-de Sitter spacetimes are applied to model quark-gluon-like plasmas typical in heavy ion collisions. Employing AdS/CFT correspondence, we present a stationary, rotating, strongly coupled conformal plasma, modeled as a dual to a 5D Myers-Perry Anti-de Sitter Black Hole. We derive and calculate the plasma's long and short-wavelength spectra, distinguished as hydrodynamic and non-hydrodynamic modes, based on linear perturbations in the 5D gravitational theory. These perturbations, corresponding to 4D plasma fluctuations, yield distinct quasinormal modes, identified as eigenvalues of a non-Hermitian operator. Our investigation explores the application of hydrodynamics to these plasmas, particularly under rotational conditions including near-extremality. We computed the radius of convergence for hydrodynamic regimes, derived explicit hydrodynamic dispersion relations with boosted fluid transport coefficients, parameterized with momentum and vorticity. The study verifies the physical behavior of modeled plasmas, ensuring stability and causality across all temperatures and non-subluminal vorticities, aligning with prior findings on relativistic fluids. Additionally, we explore novel behaviors in the non-hydrodynamic spectrum under rotation, such as critical points, mode decay enhancement or suppression, and multiple level crossings between non-hydrodynamic modes. Similar to charged holographic fluids, we also observe features such as the emergence of branch cuts near extremality.

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In a quasi-particle model of QCD matter at finite temperature with thermal masses for quarks and gluons from hard thermal loops, the equation of state (EOS) can be described by an effective temperature dependence of the strong coupling $g(T)$. Assuming the same effective coupling between the exchanged gluon and thermal partons, the EOS can also be related to parton energy loss. Based on the quasi-particle linear Boltzmann transport (QLBT) model coupled to a (3+1)-dimensional viscous hydrodynamic model of the quark-gluon plasma (QGP) evolution and a hybrid fragmentation-coalescence model for heavy quark hadronization, we perform a Bayesian analysis of the experimental data on $D$ meson suppression $R_{rm AA}$ and anisotropy $v_2$ at RHIC and the LHC. We achieve a simultaneous constraint on the QGP EOS and the heavy quark transport coefficient, both consistent with the lattice QCD results.

References:
Eur.Phys.J.C 82 (2022) 4, 350
Phys.Lett.B 848 (2024) 138355

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Neutrino flavor transformation, a quantum phenomenon that allows neutrinos to change species (electron-type, muon-type or tau-type) as they propagate, is a key part of the physics needed to understand the outcome of, for instance, core-collapse supernovae or neutron star mergers. Similarly, in the early Universe, the expansion rate and the primordial abundances from Big-Bang nucleosynthesis (BBN) directly depend on neutrino evolution. When an asymmetry between neutrinos and antineutrinos is present, so-called “collective oscillations” can take place, with a rich phenomenology. We introduce different approximations, adapted to different environments, to study more efficiently (but as accurately as possible) neutrino flavor evolution in these systems. In the early Universe, the large separation of time scales involved allows to essentially “average” the individual oscillations, providing a framework to constrain primordial asymmetries from BBN and CMB measurements. In astrophysical environments, we rewrite the quantum evolution equations in terms of angular moments, which still captures flavor conversion mechanisms that attracted a lot of attention recently, namely “fast flavor instabilities” (FFI). We use linear stability analysis to assess the characteristics of FFI across a neutron star merger simulation, a new step towards the long-term goal of the community to include flavor conversions in hydrodynamics simulations.

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A paramount goal in nuclear physics is to unify ab initio treatments of bound and unbound states. The position-space quantum Monte Carlo (QMC) methods have a long history of successful bound-state calculations in light systems but have seen minimal implementation in unbound systems. Here, we introduce a numerical method to improve the efficiency and accuracy of unbound-state calculations in QMC, implement it numerically in the definitive computer codes for these methods, and test it out in nuclear systems small enough for quick turnaround but large enough to have interesting dynamics. The method involves inferring long-range amplitudes in the wave function from integrals over the small region where all the particles interact. Applying the integral method in Green’s function Monte Carlo reproduces existing results in neutron-alpha scattering, clearing the way for its use in coupled-channels problems. This technique makes a path for GFMC-accurate calculations of coupled-channels scattering, including reactions, in nuclear mass ranges that may be permanently beyond the range of the other few-body methods.

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Large neutrino secret interactions are not excluded and could be a portal to hitherto unknown physics beyond the standard model. The consequence of supernova (SN) neutrinos forming a self-coupled relativistic fluid has been a long-standing unresolved mystery that has been recently revived. For the first time, we solve all steps, systematically using relativistic hydrodynamics, and a simplified source model. First, we examine how heat transport via neutrino diffusion inside the central protoneutron star (PNS) is affected by the secret interactions. We solve the equations of the relativistic fluid coupled to the nuclear matter in the presence of temperature gradients, showing that the heat flux transported by the neutrino fluid is very similar to the non-interacting case. Small energy-transfer modifications may affect the neutrino-driven explosion mechanism, but on present evidence are not ruled in or out. If secret interactions violate lepton number, the PNS would quickly deleptonize, although even in this case no definite statement on the SN fate can be drawn without dedicated simulations. Later, we discuss the emission of the neutrino fluid from the PNS surface, which we simplify as an ideal blackbody. While the standard blackbody emission of non-interacting particles is described by the Stefan-Boltzmann law, we show that the fluid nature of the emitted neutrinos changes the effective temperature outside the blackbody, with the fluid being emitted sonically from the PNS surface. The energy outflow is remarkably similar to the standard case. Finally, after the neutrino fluid leaves the PNS, we study its free expansion, showing that it evolves into a fireball, while its spectrum in the laboratory frame remains unaffected. After the density has rarefied sufficiently, secret interactions decouple, leading to the formation of the neutrino spectrum observable at Earth. Overall, the impact on SN physics and the neutrino signal is remarkably small. Signal duration is left unchanged; even for complete thermalization within the fireball, the observable spectrum barely changes. The results of this work are published in two preprints, one of which is accepted and the other of which is presently under review.

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Ab-initio simulations of multiple heavy quarks propagating in a Quark-Gluon Plasma are computationally difficult to perform due to the large dimension of the space of density matrices. Neural Network Quantum States offer a promising approach to overcoming this numerical difficulty by variationally parametrising quantum states with parameters of a Neural Network. In this talk, I present proof of principle demonstrations of these methods in a QCD-like theory, by solving the Lindblad master equation in the 1+1d lattice Schwinger Model as an Open Quantum System. Neural Network quantum states enable the study of in-medium dynamics on large lattice volumes, where multiple-string interactions and their effects on string-breaking and recombination phenomena can be studied. Thermal properties of the system at equilibrium can also be probed with these methods by variationally constructing the stable state of the Lindblad master equation. Scaling of this approach with system size is presented, and numerical demonstrations on up to 32 spatial lattice sites and with up to 3 interacting strings are presented.

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Various 2 -> 3 exclusive processes in the collinear factorisation framework have been studied in the literature. As explained by Qiu and Yu in 2305.15397, such processes give access to enhanced x-dependence of GPDs, beyond the moment-type information that is accessed in well-studied 2->2 exclusive processes such as Deeply Virtual Compton Scattering. In 2205.07846 and 2210.07995, it was proved that a wide range of 2->3 exclusive processes factorise. Moreover, through the exclusive photoproduction of photon-meson pair with large invariant mass, which falls in the latter category and which will be the focus of my talk, chiral-odd GPDs can be probed at the leading twist. I will discuss our recent results from 2212.00655 and 2302.12026 on the subject, performed at leading order and leading twist, for a charged pion and rho meson of any charge and polarisation. Our results indicate that the statistics are very promising for performing an experimental study at various experiments, such as COMPASS, future EIC, LHC in ultraperipheral collisions, and especially at JLab. I will further talk about the issues in extending the calculation to having a neutral pion in the final state, which is sensitive to gluon GPDs, unlike the calculations we have performed already. Finally, I will discuss our current progress in extending our previous calculations to next-to-leading order.

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In our current understanding of the universe, the fundamental nature of its two most abundant constituents, dark matter (DM) and dark energy (DE), is still a mystery. A promising DM candidate is the sterile neutrino with a mass of O(keV). Its existence could be revealed in terrestrial experiments as a distortion of beta-decay spectra or as reconstructed missing energy in electron capture processes, for which very accurate predictions from nuclear physics are needed. The simplest mechanism able to produce sterile neutrinos in the early universe is named Dodelson-Widrow after its inventors, and works thanks to non-zero mixing between active and sterile neutrino species. Unfortunately, assuming that sterile neutrinos constitute the entire abundance of DM today, this vanilla solution is poorly overlapping with the region of the parameter space in which near future experiments will be sensitive to such particles. After introducing the standard scenario and the upcoming experiments involved in the hunt for sterile neutrinos, I will discuss two simple modifications that change drastically the perspectives of detection of this DM candidate in the near future. They have to do with the following questions. What if the universe evolved differently before Big Bang Nucleosynthesis from what is usually assumed? What if active neutrinos interact among each other also through non-standard interactions?

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The hadron mass can be obtained through calculating the trace of the energy momentum tensor (EMT) in the hadron. The anomaly due to the conformal symmetry breaking is believed to be an important ingredient for hadron mass generation and confinement. In this talk, I will present the calculation of the gluon trace anomaly form factors of the pion and nucleon up to Q2 ~ 4.3 GeV2. The calculations are performed on a domain wall fermion (DWF) ensemble with overlap valence quarks at 4 valence pion masses varying above and at the unitary point ~340 MeV. We estimate the radius of the gluon trace anomaly form factor. By performing a Fourier transform on the gluon trace anomaly form factors in the Breit frame, we also obtain the trace anomaly density of the pion and nucleon for several quark masses. The sign change of the density of pion is observed and is consistent with the result from a recent lattice calculation.

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The emergence of collective behavior from the underlying quantum dynamics is a central guiding principle in our understanding of how quantum many-body systems thermalize. A particular signature is universal far-from-equilibrium scaling which arises in a wide variety of systems across different energy scales, from turbulent thermalization in relativistic nuclear collisions to far-from-equilibrium Bose condensation in ultracold atomic gases. In this talk I will discuss how such self-organized universal scaling emerges from the underlying strongly-correlated quantum dynamics for QCD kinetic theory and from first principles for a relativistic vector model. The associated nonthermal attractor behavior presents an important mechanism of how quantum many-body systems lose sensitivity to their far-from-equilibrium initial conditions towards thermalization.

References: arXiv:2209.14883 and arXiv:2307.07545

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The Symmetry-Breaking/Symmetry-Restoration methodology provides a valuable tool in many-body physics, enabling an enhanced approximation of a Hamiltonian's ground state energy within a variational framework, particularly in systems undergoing a Spontaneous Symmetry Breaking quantum phase transition. In this talk, I will demonstrate the implementation of this methodology within the quantum computing framework, utilizing the Variational Quantum Eigensolver (VQE) for the variational component alongside an ansatz inspired by the Bardeen-Cooper-Schrieffer (BCS) theory. Through the application of a projective technique for symmetry restoration, I will introduce two schemes analogous to their classical counterparts: the Quantum Projection After Variation (Q-PAV) and the Quantum Variation After Projection (Q-VAP). Various projective techniques will be explored, some based on Quantum Phase Estimation algorithms, others on the quantum "Oracle" concept, and another leveraging the Classical Shadows technique. The study employs two model Hamiltonians: the pairing and Hubbard Hamiltonians. Additionally, I will present hybrid quantum-classical methods, such as the t-expansion and Krylov methods, which serve to either enhance the accuracy of the ground state energy or procure information about the low-lying Hamiltonian spectrum.

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We present a model for abundances of heavy elements in metal-poor stars. These stars form early in the history of the interstellar medium (ISM), before contributions from Type 1a supernovae and other events associated with low-mass stars become significant, and are therefore dominated by contributions from Type II supernovae and neutron star mergers associated with massive stars. We take a data-driven approach: the abundances can be explained by the contributions of a small number of unknown sources, which will be constrained by the data. We average the contributions of each source type: each source produces a characteristic amount of each element, which mixes with a characteristic region of the ISM to produce a characteristic concentration. We define a template to be the pattern of elemental concentrations produced by a particular source type. The elemental abundances observed in a metal-poor star should therefore be a linear combination of the templates of the different source types, with the mixing coefficients representative of the number of events of a given type. We constrain the possible templates using the 4th data release of the R-Process Alliance, which provides accurate abundances of Fe, Sr, Ba, and Eu for 195 stars. We find that the dataset can be well fit by the combination of two templates: one dominantly producing Fe and Sr, which we identify as Type II supernovae, and the other producing Sr, Ba, and Eu, which we identify as neutron star mergers. With these templates, the data for (140,190,192) out of 195 stars can be fit within (1,2,3) σ. We constrain the relative production of the templates, and find the Sr production of supernova is several times less than that of neutron star mergers. We discuss the implications of these results for production mechanisms in neutron star mergers. This work is the first rigorous analysis of the abundance data to derive production templates of astrophysical sources, and demonstrates for the first time that Type II supernovae are required to produce Sr in addition to neutron star mergers.

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I will talk about cold radiative neutron-deuteron (nd) capture into a triton and a photon using pionless effective field theory (EFT) and Wigner-SU(4) symmetry. Cold nd capture is one of the simplest reactions involving three nucleons and an external current. The study of this process not only helps us better understand the electromagnetic properties of the three-nucleon bound states but is also crucial for studying more complicated processes, such as its isospin mirror process, the proton-deuteron capture into Helium-3 and a photon. We calculate radiative nd capture cross section fully perturbatively up to next-to-next-to-leading order (NNLO) in pionless EFT including contributions from electric and magnetic dipole (E1 and M1, respectively) transitions. The contribution from M1 transitions dominates at thermal neutron momentum, whereas that from E1 transitions dominates at higher energies. At NNLO we identify a new three-nucleon magnetic moment counterterm to renormalize both nd capture and the triton magnetic moment. In addition, I will talk about how the EFT power counting of nd capture cross section may be altered by expanding around the Wigner-SU(4) limit, where the binding momentum and effective range are the same for the deuteron and two-nucleon spin-singlet virtual state. This helps explain the sensitivity of nd capture cross section to the strength of the isovector two-nucleon magnetic current at thermal neutron momentum, as observed in both our study and previous potential-model calculations. I will also discuss some ongoing studies based on this work, such as polarization observables and parity violation in nd capture.

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Neutron stars are fascinating astrophysical objects where matter reaches extremely high density conditions. Their structure, dynamics and composition are governed by the nuclear matter equation of state, which can be investigated in laboratory experiments targeting properties of atomic nuclei. In particular, studies of the electric dipole polarizability across the nuclear chart play a significant role in understanding bulk properties of nuclei, as this quantity is strongly correlated to parameters entering the nuclear matter equation of state. This observable can be computed in an ab initio framework taking advantage of the LIT-CC method. This approach is based on merging the Lorentz Integral Transform (LIT) technique, that allows a proper treatment of the continuum problem, with the mild computational scaling characterizing Coupled-Cluster (CC) theory with increasing mass number. In this talk, I will discuss recent coupled-cluster computations of the dipole polarizability encompassing light neutron-rich [1, 2] and closed-shell medium-mass nuclei [3], and compare them to experimental data. Moreover, I will present new theoretical developments allowing to extend the reach of the LIT-CC method to open-shell nuclei.

[1] F. Bonaiti, S. Bacca, G. Hagen, Ab-initio coupled-cluster calculations of ground and dipole excited states in 8He, Phys. Rev. C 105, 034313 (2022).
[2] B. Acharya, S. Bacca, F. Bonaiti et al., Uncertainty quantification in electromagnetic observables of nuclei, Front. In Phys. 10:1066035 (2023).
[3] R. W. Fearick, P. von Neumann-Cosel, S. Bacca, J. Birkhan, F. Bonaiti et al., in preparation.

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QCD jets provide one of the best avenues to extract information about the quark-gluon plasma produced in ultra-relativistic heavy ion collisions, where quantum simulation can be a useful tool to study jet evolution directly. In this work, based on the light-front Hamiltonian formalism, we construct a digital quantum circuit that tracks the evolution of a single hard probe in the presence of a stochastic color background and obtain quenching parameters using classical simulators. The focus of this work was put on understanding the diffusion of a single parton interacting with the Color-glass condensate background field of two colors. In terms of the jet quenching parameter, the results obtained using classical simulators of ideal quantum computers agree with known analytical results. With this study, we hope to provide a baseline for future in-medium jet physics studies using quantum computers.

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The majority of known hadrons in the low-energy QCD spectrum are resonances observed in multi-particle scattering processes. First-principles determinations of the properties of these unstable hadrons are a crucial goal in lattice QCD calculations. Significant progress has been made in developing, implementing, and applying theoretical tools that connect finite-volume lattice QCD quantities to scattering amplitudes, enabling determination of masses and widths of various hadronic resonances. In this talk, I will discuss recent advances in the study of meson-baryon resonances, including the Delta(1232) and Lambda(1405) resonances, as well as three-body processes using lattice QCD.

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The observation of jet quenching in heavy-ion collisions in early the 2000's has provided great evidence in favour of the idea that a quark-gluon plasma (QGP) is created in such experiments. Moving forward however, in order to obtain a better understanding of the jet quenching process, it is desirable to be able to more precisely quantify the jet-medium interactions and moreover their impact on jet energy loss calculations. During this talk, I will firstly highlight how these energy loss calculations are controlled by two objects: the asymptotic mass of the jet particle and the transverse momentum broadening kernel, which is closely related to the transverse momentum broadening coefficient, qhat. I will then sketch how a recent insight of Caron-Huot [1] has allowed soft corrections to the aforementioned quantities to be computed in electrostatic QCD (EQCD), both perturbatively and on the lattice. I will follow by demonstrating how this is related to my own work, namely, the perturbative determination of corrections to the asymptotic mass and the transverse momentum broadening coefficient within the context of thermal field theory. Finally, I will discuss in some more detail my recent work [2] on the transverse momentum broadening coefficient and how it fits in with the goal of attempting to more rigorously and precisely quantify the quenching of a jet as it traverses the QGP.

[1]: Caron-Huot, arxiv: 0811.1603
[2]: Ghiglieri, Weitz, arxiv: 2207.08842

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The nuclear equation of state is a fundamental property of nature that governs the behavior of nuclei at different densities and asymmetries. In particular, the equation of state for neutron-rich systems is of interest because of its importance in many astrophysical systems. There exist many physical observables that help constrain our understanding of the equation of state, such as the difference in point neutron and proton radii in neutron rich nuclei or the radius of a neutron star. Recently, the PREX/CREX collaboration have published results for the neutron skin in both Pb and Ca which paint a rather peculiar picture for the behavior of neutron-rich matter. In this talk, I will discuss the PREX-2 and CREX experimental results and what they mean for our understanding of the nuclear equation of state. In addition, the connection to neutron stars and gravitational waves will also be discussed.

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In view of recent measurements of anomalies in semileptonic B meson decays at LHCb and several other collider experiments hinting at the possible violation of lepton flavour universality (LFU), we present a concise review of theoretical foundations of the tree- and loop-level b decays, b →c, l l and b →s, l+l- along with the updated experimental background. We study the q2- dependence of form factors for the semileptonic transitions and then present the world averages, RD(D*), RK(K*), RJ/ψ, and Rc in a model dependent (based on relativistic independent quark model (RIQM)) as well as model independent approach. We further provide predictions of other anomalies linked with LFU violation such as, anomalous magnetic moment of electron and muon by Fermilab (a, ae), mass of W boson by CDF collaboration, the CKM puzzle (R(Vus)) in view of future high-statistics data, are also discussed. We then look over to the combined explanation of charged-current and neutral- current anomalies (RD(D*), RK), unified together in the language of effective field theory. As flavor anomalies are the strongest hints for physics beyond standard model, it is therefore expected that if the ongoing evaluation of the data of LHC Run 2 confirms the measurements of Run 1, then the statistical significance of the effect in each decay channel separately is expected to reach 5σ. Therefore the confirmation of these measurements would soon turn out to be remarkable evidence, unraveling the New Physics in the flavour fraternity.

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We use general relativistic hydrodynamics simulations of binary neutron star mergers to show that high-density deconfinement phase transitions can be probed using multimodal gravitational wave (GW) spectroscopy. We find that hadron-quark phase transitions suppress the one-armed spiral instability, and note an anti-correlation between the energy carried in the l=2, m=1 GW mode and the gap in energy density which qualitatively separates the two phases. We highlight how the measured signal-to-noise ratio of the l=2, m=1, and l=2, m=2 GW modes may provide insight into the neutron star equation of state.

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Despite the plentiful computational resources at our fingertips in the exascale era, direct Bayesian calibration of physical models still remains a daunting task. Even with fully quantified models, systematic studies and properly exploring your posteriors can still pose significant computational hardship. In this talk I will present recent work in the development of physics-informed emulators that will enable (relatively) quick calibration and evaluation of microscopic models, discuss our future goals to extend such methods to time-dependent systems, and show some strategies for making the tools and data both available and accessible. Finally, I will sketch an optimistic framework that will allow this machinery to be agile in the face of new data coming from next-generation experimental facilities.

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We give evidence for phase boundaries between the Higgs and confining regimes of a class of confining gauge theories with fundamental matter. The defining feature of the theories we consider is the presence of a spontaneously broken U(1) global symmetry, whose order parameter can fractionalize into charged constituents in the fundamental representation of the gauge group. First we consider a 2+1 dimensional abelian gauge theory in the continuum and on the lattice, and argue that a phase boundary is detected by the behavior of a non-local order parameter. We then discuss implications for the Schafer-Wilczek conjecture of quark-hadron continuity.

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In this talk, I will present our recent work about the (3+1)D hydrodynamics simulations in Ultra-Peripheral Pb+Pb collisions (UPCs) at LHC and small system scan at RHIC. For UPC simulations, we find longitudinal flow decorrelation can explain the smaller 𝑣2 in 𝛾*+Pb collisions and compared to those in p+Pb collisions. For RHIC small system scan, we find a big fraction of 𝑣3 (𝑝𝑇) difference in STAR and PHENIX measurements can be explained by using reference flow vectors from different rapidity regions. We also study the baryon junction mechanism in UPCs. UPCs provide a clean channel to probe initial-state baryon stopping dynamics.

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The discrepancies between theoretical predictions and observations motivate improved theory techniques or may provide evidence for new physics. Predictive models of nuclei are needed as input for experimental tests and for astrophysical models.

In this talk, I will examine the nuclear reactions 7Li(p,y)8Be and 7Li(p,e+e-)8Be from an ab initio perspective.Using chiral nucleon-nucleon and three-nucleon forces as input, the no-core shell model with continuum technique allows us to obtain an accurate description of both 8Be bound states and p+7Li scattering states.

The energy freed up by capture is enough to produce electron-positron pairs. The angular distribution of these pairs will be different if the intermediate particle is not the photon, for example, the axion or new vector or axial vector boson. Computing the standard model background and comparing experimental data with new decay modes is necessary to support or rule out new physics in the ATOMKI anomaly (which posits the existence of a new boson with a mass of 17 MeV).



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Limits on the charged lepton flavor violating (CLFV) process of μ→e conversion are expected to improve by four orders of magnitude due to the next generation of experiments, Mu2e at Fermilab and COMET at J-PARC. While the kinematics of the decay of a trapped muon are ideal for detecting a signal of CLFV, the intervening nuclear physics presents a significant roadblock to the interpretation of experimental results. We report on two directions of recent progress: First, we describe how a limited class of scalar-mediated quark-level interactions can be reduced to the nuclear scale, yielding predictions for CLFV branching ratios with well-understood uncertainties and allowing one to place rigorous constraints on certain candidate UV models. Second, we introduce an effective theory of μ→e conversion formulated directly at the nuclear scale, which factorizes the nuclear physics from the CLFV leptonic physics, sequestering the latter quantity into unknown low-energy constants (LECs) that are probed directly by experiments. Utilizing state-of-the-art shell-model calculations of nuclear response functions, we discuss how a program of μ→e conversion measurements on different targets—selected for their nuclear ground-state properties—could constrain the unknown LECs.

References: https://arxiv.org/abs/2203.09547, https://arxiv.org/abs/2208.07945, https://arxiv.org/abs/2109.13503

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It has been known since the 1930’s that protons are not “point-like” elementary particles, but rather have a substructure. Today, we know from Quantum Chromodynamics (QCD) that protons are made from quarks and gluons, with gluons being the elementary force carriers for strong interactions. Quarks and gluons are collectively called as partons. The substructure of the protons can be described in terms of parton correlation functions such as Form Factors, (1D) Parton Distribution Functions (PDFs) and their 3D generalizations in terms of Transverse Momentum-dependent parton Distributions and Generalized Parton Distributions. All these functions can be derived from the Wigner functions, which simultaneously encode the spatial and momentum distribution of partons inside protons. In this talk, we provide an insight into all these functions from the point of view of their accessibility in experiments as well as from their direct calculation within lattice formulations of QCD.

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By using gravity/gauge correspondence, we employ an Einstein-Maxwell-dilaton model to compute the equilibrium and out-of-equilibrium properties of a hot and baryon rich strongly coupled quark-gluon plasma. The family of 5-dimensional holographic black holes, which are constrained to mimic the lattice QCD equation of state at zero density, is used to investigate the temperature and baryon chemical potential dependence of the equation of state. We also obtained the baryon charge transport coefficients, the bulk and shear viscosities as well as the drag force and Langevin diffusion coefficients associated with heavy quark jet propagation and the jet quenching parameter of light quarks in the baryon dense plasma, with a particular focus on the behavior of these observables on top of the critical end point and the line of first order phase transition predicted by the model.

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Several decades after the first solar neutrino detections, neutrino astronomy now stands as a unique pillar of multimessenger science. But whereas neutrino oscillations in the solar context were the solution to a problem, in other astrophysical contexts they are the problem. This is especially true of core-collapse supernovae and neutron-star mergers. Even though these sites are two of the marquee targets of multimessenger astronomy, and two of the most carefully modeled systems in computational astrophysics, neutrino oscillations are yet to be reliably incorporated into the relevant predictions and simulations. This talk will give a broad overview of neutrino mixing in these settings, as well as in the proposed sources of IceCube neutrinos and in the cosmic background. Basic concepts will be emphasized throughout, because the practical challenges of neutrino transport, which may appear technical and venue-specific, are in fact firmly tied to fundamental questions concerning quantum and statistical physics.

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Nuclei play a critical role in high-precision tests of the Standard Model and in searches for Beyond Standard Model physics. In order to disentangle new physics signals from nuclear physics effects, one must have an accurate understanding of the underlying nuclear dynamics. Quantum Monte Carlo (QMC) methods in combination with chiral effective field theory interactions and electroweak currents provide a means to systematically understand these dynamics. In this talk, I will present studies of beta decay and muon capture in light nuclei using the Norfolk potential, a high-quality local chiral interaction, and its consistent many-body axial and vector current operators.

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The strong interactions of the standard model described by quantum chromodynamics (QCD) pose a challenging problem for classical computation. Emerging quantum platforms provide an exciting possibility for investigating QFTs in previously inaccessible regimes. This has motivated a search for unconventional formulations of QFTs with finite-dimensional local Hilbert spaces, or with “qubit” degrees of freedom. In this talk, I will describe recent work in constructing qubit models for asymptotically-free 1+1d nonlinear sigma models, which are well-known prototypes of QCD. In particular, conventional lattice formulations of topological θ vacua in the 2d O(3) nonlinear sigma model suffer from a severe sign problem on classical computers. Remarkably, by formulating this as model of qubits, not only do we obtain a viable path towards its quantum simulation, but we also obtain the first sign-problem-free regularization for arbitrary θ, solving a longstanding sign problem. We show that such models can reproduce both the IR physics of theta vacua and the UV physics of asymptotic freedom. In the search for new qubit models in higher dimensions and for gauge theories, symmetries and anomalies are a guide. We will discuss how the perspective of recently discovered discrete anomalies provides interesting constraints on possible lattice regularizations towards the goal of finding such qubit models for QCD-like theories.

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