Publications

Order by: publication date number of citations

• Unfrustrating the t-J Model: d-wave BCS Superconductivity in the t'-J_z-V Model

  Kevin Slagle

  SciPost Phys. 7, 046 (2019) · published 9 October 2019 | Toggle abstract · pdf

  The t-J model is believed to be a minimal model that may be capable of describing the low-energy physics of the cuprate superconductors. However, although the t-J model is simple in appearance, obtaining a detailed understanding of its phase diagram has proved to be challenging. We are therefore motivated to study modifications to the t-J model such that its phase diagram and mechanism for d-wave superconductivity can be understood analytically without making uncontrolled approximations. The modified model we consider is a t'-J_z-V model on a square lattice, which has a second-nearest-neighbor hopping t' (instead of a nearest-neighbor hopping t), an Ising (instead of Heisenberg) antiferromagnetic coupling J_z, and a nearest-neighbor repulsion V. In a certain strongly interacting limit, the ground state is an antiferromagnetic superconductor that can be described exactly by a Hamiltonian where the only interaction is a nearest-neighbor attraction. BCS theory can then be applied with arbitrary analytical control, from which nodeless d-wave or s-wave superconductivity can result.

• First measurement of the forward rapidity gap distribution in pPb collisions at 8 TeV

  Dmitry E. Sosnov

  SciPost Phys. Proc. 8, 065 (2022) · published 12 July 2022 | Toggle abstract · pdf

  We present the forward rapidity gap spectra from proton-lead collisions for both I\!P-Pb and I\!P-p topologies measured at the CMS at a center-of-mass energy of 8.16 TeV. For the I\!P-Pb topology, the cross-section predicted by EPOS-LHC is a factor of two lower than the data while has reasonable description of the spectrum shape. For the I\!P-p topology, the EPOS-LHC, QGSJET~II and HIJING predictions are significantly lower than the data, what can be explained by a contribution of ultra-peripheral photoproduction events. The obtained data may be of significant input for understanding the high energy limit of QCD and modeling cosmic ray air showers.

• $\mathcal{O}(α_s^3)$ corrections to semileptonic $b \to c$ decays in the heavy daughter approximation

  Kay Schoenwald

  SciPost Phys. Proc. 7, 027 (2022) · published 21 June 2022 | Toggle abstract · pdf

  We present our recent calculation of the third order corrections to the semileptonic $b \to c$ and the muon decays. The calculation has been performed in an expansion around the limit $m_c \sim m_b$, but shows decent convergence even for $m_c=0$ from which the contribution to the muon decay can be extracted. For the semileptonic $b \to c$ decay we find large perturbative corrections in the on-shell scheme which can be significantly reduced by changing to the kinetic scheme for the bottom quark mass. These results are important input for the inclusive determination of $|V_{cb}|$ and the Fermi coupling constant $G_F$.

• Josephson effects between the Kitaev ladder superconductors

  Osamu Kanehira, Hiroki Tsuchiura

  SciPost Phys. Proc. 11, 014 (2023) · published 6 June 2023 | Toggle abstract · pdf

  The two-leg ladder system consisting of the Kitaev chains is known to exhibit a richer phase diagram than that of the single chain. We theoretically investigate the variety of the Josephson effects between the ladder systems. We consider the Josephson phase difference $\theta$ between these two ladder systems as well as the phase difference $\phi$ between the parallel chains in each ladder system. The total energy of the junction at $T = 0$ is calculated by a numerical diagonalization method as functions of $\theta$, $\phi$, and also a transverse hopping $t_{\perp}$ in the ladders. We find that, by controlling $t_{\perp}$ and $\phi$, the junction exhibits not only the fractional Josephson effect for the phase difference $\theta$, but also the usual 0-junction and even $\pi$-junction properties.

• Nucleon and pion PDFs: large-x asymptotics meets functional mimicry

  Aurore Courtoy, Pavel M. Nadolsky

  SciPost Phys. Proc. 8, 063 (2022) · published 12 July 2022 | Toggle abstract · pdf

  We review strategies to unveil the primordial large-$x$ structure of the nucleons as well as the pion from hard-scattering experiments. Ideas are presented for learning about the $x\to 1$ limit of nonperturbative QCD dynamics at energy scales of order 1 GeV from collider experiments at much higher scales. The behavior of parton distributions at $x\to 1$ predicted by the quark counting rules and other low-energy theoretical approaches is contrasted with phenomenological PDFs. Polynomial mimicry of PDF parametrizations is one of many factors that influence the apparent power of the $(1-x)$ falloff. We discuss implications of the mimicry for the large-$x$ falloff of the pion PDFs.

• Collective dynamics of densely confined active polar disks with self- and mutual alignment

  Weizhen Tang, Yating Zheng, Amir Shee, Guozheng Lin, Zhangang Han, Pawel Romanczuk, Cristián Huepe

  SciPost Phys. 19, 012 (2025) · published 8 July 2025 | Toggle abstract · pdf

  We study the emerging collective states in a simple mechanical model of a dense group of self-propelled polar disks with off-centered rotation, confined within a circular arena. Each disk presents self-alignment towards the sum of contact forces acting on it, resulting from disk-substrate interactions, while also displaying mutual alignment with neighbors due to having its center of rotation located a distance $R$ behind its centroid, so that central contact forces can also introduce torques. The effect of both alignment mechanisms produces a variety of collective states that combine high-frequency localized circular oscillations with low-frequency milling around the center of the arena, in fluid or solid regimes. We consider cases with small/large $R$ values, isotropic/anisotropic disk-substrate damping, smooth/rough arena boundaries, different densities, and multiple systems sizes, showing that the emergent collective states that we identify are robust, generic, and potentially observable in real-world natural or artificial systems.

• Workshop on Tau Lepton Physics: $\mathbf{30^{th}}$ Anniversary

  Antonio Pich

  SciPost Phys. Proc. 16, 001 (2025) · published 14 July 2025 | Toggle abstract · pdf

  The first Workshop on Tau Lepton Physics took place at Orsay in 1990. The evolution of the field and some physics highlights are briefly described, following the presentations discussed at the fifteen $\tau$ workshops that have been held since then.

• Applying Quantum Tomography to Hadronic Interactions

  J. C. Martens, J. P. Ralston, D. Tapia Takaki

  SciPost Phys. Proc. 8, 154 (2022) · published 14 July 2022 | Toggle abstract · pdf

  A proper description of inclusive reactions is expressed with density matrices. Quantum tomography reconstructs density matrices from experimental observables. We review recent work that applies quantum tomography to practical experimental data analysis. Almost all field-theoretic formalism and modeling used in a traditional approach is circumvented with great efficiency. Tomographically-determined density matrices can express information about quantum systems which cannot in principle be expressed with distributions defined by classical probability. Topics such as entanglement and von Neumann entropy can be accessed using the same natural language where they are defined. A deep relation exists between {\it separability}, as defined in quantum information science, and {\it factorization}, as defined in high energyphysics. Factorization acquires a non-perturbative definition when expressed in terms of a conditional form of separability. An example illustrates how to go from data for momentum 4-vectors to a density matrix while bypassing almost all the formalism of the Standard Model.

• Updated determinations of |V$_{us}$| with tau decays using new recent estimates of radiative corrections for light-meson leptonic decay rates

  Alberto Lusiani

  SciPost Phys. Proc. 16, 002 (2025) · published 14 July 2025 | Toggle abstract · pdf

  We update the |V$_{us}$| determinations using the HFLAV 2018 report tau branching fraction results with recent new estimates of the $\pi\ell2$ and $K\ell2$ radiative corrections. There are minor changes of the central values and uncertainties.

• Prospects of a future multi-TeV muon collider

  M. Casarsa

  SciPost Phys. Proc. 8, 061 (2022) · published 12 July 2022 | Toggle abstract · pdf

  A multi-TeV muon collider is a discovery machine and an invaluable tool for many new standard model precision measurements such as the shape of the Higgs boson potential. The update of the European Strategy for Particle Physics recognized the unique opportunity of a muon collider to reach the energy frontier, despite the challenges to produce intense collimated muon beams. The options of a collider at 3 TeV and a collider at 10 TeV or above are the main focus of the forming International Muon Collider Collaboration as well as of the discussion panels at the ongoing US Snowmass process.