Johannes Roth
Justus Liebig University Giessen
Dec. 10th, 2024
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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Tommaso Rainaldi
Old Dominion University
Dec. 3rd, 2024
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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Simone Li Muli
Chalmers University of Technology
Nov. 19th, 2024
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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Anil Kumar
University of Tsukuba
Nov. 12th, 2024
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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Anthony Ciavarella
Lawrence Berkeley National Lab
Oct. 29th, 2024
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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Bryce Fore
Argonne National Lab
Oct. 15th, 2024
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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Matthias Heinz
Technische Universität Darmstadt
June 18th, 2024
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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Preparation on a quantum computer
Chung-Chun Hsieh
University of Maryland
June 4th, 2024
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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Pooja Siwach
Lawrence Livermore National Laboratory
May 21st, 2024
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Paul Hotzy
University of Technology Vienna
May 7th, 2024
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Savvas Pitsinigkos
University of Southampton
April 23nd, 2024
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Markus Amano
Yamagata University
April 2nd, 2024
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Feng-Lei Liu
Central China Normal University
March. 19th, 2024
References:
Eur.Phys.J.C 82 (2022) 4, 350
Phys.Lett.B 848 (2024) 138355
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Julien Froustey
N3AS at North Carolina State University
March. 5th, 2024
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Abe Flores
Washington University in St. Louis
Feb. 20th, 2024
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Damiano Fiorillo
Niels Bohr Institute
Feb. 6th, 2024
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Joshua Lin
Massachusetts Institute of Technology
Jan. 23rd, 2024
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Saad Nabeebaccus
Paris-Saclay University
Jan. 16th, 2024
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Cristina Benso
Karlsruhe Institute for Technology
Dec. 12th, 2023
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Bigeng Wang
University of Kentucky
Dec. 5th, 2023
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Thimo Preis
Heidelberg University
Nov. 21st, 2023
References: arXiv:2209.14883 and arXiv:2307.07545
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Andres Ruiz
IBM Quantum France
Nov. 7th, 2023
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Axel Gross
University of Minnesota
Oct. 17th, 2023
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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Xincheng Lin
Duke University
Oct. 3rd, 2023
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Francesca Bonaiti
Johannes-Gutenberg University
June 20th, 2023
[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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Wenyang Qian
University of Santiago de Compostela
June 6th, 2023
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Fernando Romero-Lopez
Massachusetts Institute of Technology
May 16th, 2023
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Eamonn Weitz
SUBATECH, Nantes Université
May 2nd, 2023
[1]: Caron-Huot, arxiv: 0811.1603
[2]: Ghiglieri, Weitz, arxiv: 2207.08842
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Brendan Reed
Indiana University
April 18th, 2023
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Sonali Patnaik
College of Basic Sciences and Humanities (CBSH), OUAT, Bhubaneswar Ind
April 4th, 2023
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Pedro Espino
Network for Neutrinos, Nuclear Astrophysics, and Symmetries
Mar. 21st, 2023
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Kyle Godbey
Facility for Rare Isotope Beams
Mar. 7th, 2023
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Theo Jacobson
University of Minnesota
Feb. 21, 2023
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Wenbin Zhao
Wayne State University
Feb. 7, 2023
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Peter Gysbers
University of British Columbia and TRIUMF
Jan. 17, 2023
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).
Evan Rule
N3AS and University of California Berkeley
Dec 13, 2022
References: https://arxiv.org/abs/2203.09547, https://arxiv.org/abs/2208.07945, https://arxiv.org/abs/2109.13503
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Shohini Bhattacharya
Brookhaven National Laboratory
Dec 6, 2022
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Quark-Gluon matter from Holographic Black Holes
Joaquin Grefa
University of Houston
Nov. 15, 2022
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Luke Johns
University of California, Berkeley
Nov. 1, 2022
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Garrett King
Washington University
Oct. 18, 2022
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Qubit models, sign problems, and anomalies
Hersh Singh
InQubator for Quantum Simulation and Institute for Nuclear Theory
Oct. 18th, 2022
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