Publications

Order by: publication date number of citations

• The role of the underlying event in the charm-baryon enhancement observed in pp collisions at LHC energies

  Zoltán Varga, Anett Misák, Róbert Vértesi

  SciPost Phys. Proc. 15, 014 (2024) · published 2 April 2024 | Toggle abstract · pdf

  We study the enhanced production of $\Lambda_c$ charmed baryons relative to that of charmed $D^0$ mesons in proton–proton collisions at LHC energies. We simulated collision events with the enhanced color-reconnection model in PYTHIA 8 MC generator and propose measurements based on the comparative use of different event-activity classifiers to identify the source of the charmed-baryon enhancement. We demonstrate that in this enhanced color-reconnection scenario the excess production is primarily linked to the underlying event and not to the production of high-momentum jets.

• Revisiting the flavor violating decays of the Tau and Mu leptons in the Standard Model with massive neutrinos

  Gerardo Hernández Tomé

  SciPost Phys. Proc. 1, 017 (2019) · published 19 February 2019 | Toggle abstract · pdf

  The flavor violating leptonic decays of the $\tau$ and $\mu$ leptons into three lighter charged leptons are revisited in the framework the Standard Model with massive neutrinos. In contrast to the previous prediction, we have found strongly suppressed rates for the $\tau^-\to \mu^- \ell^+ \ell^-$ ($\ell=\mu, e$) decays. Our results are in good agreement with the approximation of neglecting masses and momenta of the external particles in the loop integrals made in the first computation for the $\mu^- \to e^-e^+ e^-$ decay.

• Extensions of realisations for low-dimensional Lie algebras

  Iryna Yehorchenko

  SciPost Phys. Proc. 14, 048 (2023) · published 24 November 2023 | Toggle abstract · pdf

  We find extensions of realisations of some low-dimensional Lie algebras, in particular, for the Poincaré algebra for one space dimension. Using inequivalent extensions, we performed comprehensive classification of relative differential invariants for these Lie algebras. We show difference between classification of extensions of realisations, and classification of nonlinear realisations of Lie algebras.

• Flux-tunable Kitaev chain in a quantum dot array

  Juan Daniel Torres Luna, A. Mert Bozkurt, Michael Wimmer, Chun-Xiao Liu

  SciPost Phys. Core 7, 065 (2024) · published 18 September 2024 | Toggle abstract · pdf

  Connecting quantum dots through Andreev bound states in a semiconductor-superconductor hybrid provides a platform to create a Kitaev chain. Interestingly, in a double quantum dot, a pair of poor man's Majorana zero modes can emerge when the system is fine-tuned to a sweet spot, where superconducting and normal couplings are equal in magnitude. Control of the Andreev bound states is crucial for achieving this, usually implemented by varying its chemical potential. In this work, we propose using Andreev bound states in a short Josephson junction to mediate both types of couplings, with the ratio tunable by the phase difference across the junction. Now a minimal Kitaev chain can be easily tuned into the strong coupling regime by varying the phase and junction asymmetry, even without changing the dot-hybrid coupling strength. Furthermore, we identify an optimal sweet spot at $\pi$ phase, enhancing the excitation gap and robustness against phase fluctuations. Our proposal introduces a new device platform and a new tuning method for realizing quantum-dot-based Kitaev chains.

• Electric-dipole transitions in 6Li with a fully microscopic six-body calculation

  Wataru Horiuchi, Shuji Satsuka

  SciPost Phys. Proc. 3, 022 (2020) · published 25 February 2020 | Toggle abstract · pdf

  Exploring new excitation modes and the role of the nuclear clustering has been of great interest. An interesting speculation was made in the recent photoabsorption measurement of 6Li that implied the importance of the nuclear clustering. To understand the excitation mechanism of 6Li, we perform a fully microscopic six-body calculation on the electric-dipole (E1) transitions and discuss how 6Li is excited by the E1 field as a function of the excitation energy. We show the various cluster components in the six-body wave functions and discuss the role of the nuclear clustering in the E1 excitations of 6Li.

• Resummation for $tqH$ production

  Matthew Forslund, Nikolaos Kidonakis

  SciPost Phys. Proc. 8, 021 (2022) · published 11 July 2022 | Toggle abstract · pdf

  We present results with soft-gluon resummation for the associated production of a single top quark and a Higgs boson. We present analytical results for the higher-order soft-gluon corrections and numerical results for the total cross section and top-quark transverse momentum and rapidity distributions at LHC energies.

• Self-similar solutions for fuzzy dark matter

  Raquel Galazo-Garcia, Philippe Brax, Patrick Valageas

  SciPost Phys. Proc. 12, 060 (2023) · published 5 July 2023 | Toggle abstract · pdf

  Self-similar solutions for fuzzy dark matter are very different from their counterparts in the standard cold dark matter model. In contrast to the familiar hierarchical collapse of the current model for structure formation, they correspond to an inverse hierarchical blow-up. This fact highlights the gravitational cooling process, which in the absence of dissipation, allows the system to eject excess energy through the intermittent expulsion of clumps of matter. These surprising behaviours are due to the wave properties of the Schrödinger equation and to the quantum pressure. These features are printed in the Eulerian density-velocity representation of the nonrelativistic scalar field, or in the Lagrangian representation in the mass-shell trajectories.

• Dissipative preparation of a Floquet topological insulator in an optical lattice via bath engineering

  Alexander Schnell, Christof Weitenberg, André Eckardt

  SciPost Phys. 17, 052 (2024) · published 14 August 2024 | Toggle abstract · pdf

  Floquet engineering is an important tool for realizing topologically nontrivial band structures for charge-neutral atoms in optical lattices. However, the preparation of a topological-band-insulator-type state of fermions, with one nontrivial quasi-energy band filled completely and the others empty, is challenging as a result of both driving induced heating as well as imperfect adiabatic state preparation (with the latter induced by the unavoidable gap closing when passing the topological transition). An alternative procedure that has been proposed is to prepare such states dissipatively, i.e. as a steady state that emerges when coupling the system to reservoirs. Here we discuss a concrete scheme that couples the system to a weakly interacting Bose condensate given by second atomic species acting as a heat bath. Our strategy relies on the engineering of the potential for the bath particles, so that they occupy weakly coupled tubes perpendicular to the two-dimensional system. Using Floquet-Born-Markov theory, we show that the resulting nonequilibrium steady state of the driven-dissipative system approximates a topological insulator. We even find indications for the approximate stabilization of an anomalous Floquet topological insulator, a state that is impossible to realize in equilibrium.

• Properties of non-relativistic string theory

  E.A. Bergshoeff, J. Lahnsteiner, L. Romano, C. Simsek

  SciPost Phys. Proc. 4, 001 (2021) · published 13 August 2021 | Toggle abstract · pdf

  We show how Newton-Cartan geometry can be generalized to String Newton-Cartan geometry which is the geometry underlying non-relativistic string theory. Several salient properties of non-relativistic string theory in this geometric background are presented and a discussion of possible research for the future is outlined.

• Transport of orbital currents in systems with strong intervalley coupling: The case of Kekulé distorted graphene

  Tarik P. Cysne, R. B. Muniz, Tatiana G. Rappoport

  SciPost Phys. Core 7, 046 (2024) · published 30 July 2024 | Toggle abstract · pdf

  We show that orbital currents can describe the transport of orbital magnetic moments of Bloch states in models where the formalism based on valley current is not applicable. As a case study, we consider Kekulé-$O$ distorted graphene. We begin by analyzing the band structure in detail and obtain the intrinsic orbital magnetic moment operator of Bloch states for this model. Despite the simultaneous presence of time-reversal and spatial-inversion symmetries, such operator may be defined, although its expectation value at a given energy is zero. Nevertheless, its presence can be exposed by the application of an external magnetic field. We then proceed to study the transport of these quantities. In the Kekulé-$O$ distorted graphene model, the strong coupling between different valleys prevents the definition of a bulk valley current. However, the formalism of the orbital Hall effect together with the non-Abelian description of the magnetic moment operator can be directly applied to describe its transport in these types of models. We show that the Kekulé-$O$ distorted graphene model exhibits an orbital Hall insulating plateau whose height is inversely proportional to the energy band gap produced by intervalley coupling. Our results strengthen the perspective of using the orbital Hall effect formalism as a preferable alternative to the valley Hall effect approach.