Publications

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• Latest ALICE results on J/$ψ$ photoproduction in ultra-peripheral collisions at the LHC

  Tomas Herman

  SciPost Phys. Proc. 8, 106 (2022) · published 13 July 2022 | Toggle abstract · pdf

  Ultra-peripheral collisions (UPCs), studied using the ALICE detector, allow us to investigate the low-$x$ behavior of the gluon distribution of the colliding particles. Two new measurements of coherent J/$\psi$ photoproduction cross section from Pb-Pb UPCs at $\sqrt{s_{\rm NN}}=5.02$ TeV are presented: the first measurement of the $|t|$-dependence of the cross section providing a new tool to investigate the transverse gluonic structure at low Bjorken-$x$ and a rapidity-differential measurement at midrapidity allowing us to provide stringent constraints on nuclear gluon shadowing and saturation models. In addition, prospects for heavy vector meson photoproduction measurements in LHC Run 3 and 4 are presented.

• Influence of Geant4 physics list on simulation accuracy and performance

  Róbert Breier, Alexander Fuss, Holger Kluck, Valentyna Mokina, Veronika Palušová, Pavel Povinec

  SciPost Phys. Proc. 12, 063 (2023) · published 5 July 2023 | Toggle abstract · pdf

  A main goal of current low background physics is the search for rare and novel phenomena beyond the Standard Model of particle physics, e.g. the scattering off of a potential Dark Matter particle inside a CaWO$_4$ crystal or the neutrinoless double beta decay of Ge nucleus. The success of such searches depends on a reliable background prediction via Monte Carlo simulations. A widely used toolkit to construct these simulations is GEANT4, which offers a wide choice of physics models, so-called physics lists. To facilitate the selection of physics lists for simulations of CaWO$_4$ and Ge targets, we quantify their impact on the total energy deposition for several test cases.

• On correlation functions for the open XXZ chain with non-longitudinal boundary fields: The case with a constraint

  Giuliano Niccoli, Véronique Terras

  SciPost Phys. 16, 099 (2024) · published 9 April 2024 | Toggle abstract · pdf

  This paper is a continuation of [J. Phys. A: Math. Theor. 55, 405203 (2022)], in which a set of matrix elements of local operators was computed for the XXZ spin-1/2 open chain with a particular case of unparallel boundary fields. Here, we extend these results to the more general case in which both fields are non-longitudinal and related by one constraint, allowing for a partial description of the spectrum by usual Bethe equations. More precisely, the complete spectrum and eigenstates can be characterized within the Separation of Variables (SoV) framework. One uses here the fact that, under the constraint, a part of this SoV spectrum can be described via solutions of a usual, homogeneous, TQ-equation, with corresponding transfer matrix eigenstates coinciding with generalized Bethe states. We explain how to generically compute the action of a basis of local operators on such kind of states, and this under the most general boundary condition on the last site of the chain. As a result, we can compute the matrix elements of some of these basis elements in any eigenstate described by the homogenous TQ-equation. Assuming, following a conjecture of Nepomechie and Ravanini, that the ground state itself can be described in this framework, we obtain multiple integral representations for these matrix elements in the half-infinite chain limit, generalizing those previously obtained in the case of longitudinal boundary fields and in the case of the special boundary conditions considered in [J. Phys. A: Math. Theor. 55, 405203 (2022)].

• Andreev bound states at boundaries of polarized 2D Fermi superfluids with s-wave pairing and spin-orbit coupling

  Kadin Thompson, Joachim Brand, Ulrich Zuelicke

  SciPost Phys. 14, 115 (2023) · published 16 May 2023 | Toggle abstract · pdf

  A topological superfluid phase characterized by an emergent chiral-p-wave pair potential is expected to form in a two-dimensional Fermi superfluid subject to s-wave pairing, spin-orbit coupling and a large-enough Zeeman splitting. Andreev bound states appear at phase boundaries, including Majorana zero modes whose existence is assured by the bulk-boundary correspondence principle. Here we study the physical properties of these subgap-energy bound states at step-like interfaces using the spin-resolved Bogoliubov-de$\,$Gennes mean-field formalism and assuming small spin-orbit coupling. Extending a recently developed spin-projection technique based on Feshbach partitioning [SciPost Phys. 5, 016 (2018)] combined with the Andreev approximation allows us to obtain remarkably simple analytical expressions for the bound-state energies as well as the majority and minority spin components of their wave functions. Besides the vacuum boundary, where a majority-spin Majorana excitation is encountered, we also consider the boundary between the topological and a nontopological superfluid phase that can appear in a coexistence scenario due to the first-order topological phase transition predicted for this system. At this superfluid-superfluid interface, we find a localized chiral Majorana mode hosted by the minority-spin sector. Our theory further predicts majority-spin subgap-energy bound states similar to those found at a Josephson junction between same-chirality p-wave superfluids. Their presence affects the Majorana mode due to a coupling of minority and majority spin sectors only in the small energy range where their spectra overlap. Our results may inform experimental efforts aimed at realizing and characterizing unconventional Majorana quasiparticles.

• Coulomb branch surgery: Holonomy saddles, S-folds and discrete symmetry gaugings

  Elias Furrer, Horia Magureanu

  SciPost Phys. 17, 073 (2024) · published 5 September 2024 | Toggle abstract · pdf

  Symmetries of Seiberg–Witten (SW) geometries capture intricate physical aspects of the underlying 4d $\mathcal{N} = 2$ field theories. For rank-one theories, these geometries are rational elliptic surfaces whose automorphism group is a semi-direct product between the Coulomb branch (CB) symmetries and the Mordell-Weil group. We study quotients of the SW geometry by subgroups of its automorphism group, which most naturally become gaugings of discrete 0- and 1-form symmetries. Yet, new interpretations of these surgeries become evident when considering 5d $\mathcal{N}=1$ superconformal field theories. There, certain CB symmetries are related to symmetries of the corresponding $(p,q)$-brane web and, as a result, CB surgeries can give rise to (fractional) S-folds. Another novel interpretation of these quotients is the folding across dimensions: circle compactifications of the 5d $E_{2N_f + 1}$ Seiberg theories lead in the infrared to two copies of locally indistinguishable 4d SU(2) SQCD theories with $N_f$ fundamental flavours. This extends earlier results on holonomy saddles, while also reproducing detailed computations of 5d BPS spectra and predicting new 5d and 6d BPS quivers. Finally, we argue that the semi-direct product structure of the automorphism group of the SW geometry includes mixed 't Hooft anomalies between the 0- and 1-form symmetries, and we also present some new results on non-cyclic CB symmetries.

• Vertical and lateral manipulation of single Cs atoms on the semiconductor InAs(111)A

  Rian A. M. Ligthart, Cristophe Coinon, Ludovic Desplanque, Xavier Wallart, Ingmar Swart

  SciPost Phys. 16, 096 (2024) · published 5 April 2024 | Toggle abstract · pdf

  The tip of the scanning tunneling microscope can be used to position atoms and molecules on surfaces with atomic scale precision. Here, we report the controlled vertical and lateral manipulation of single Cs atoms on the InAs(111)A surface. The Cs adatom adsorbs on the In-vacancy site of the InAs(111)A—(2x2) surface reconstruction. Lateral manipulation is possible in all directions over the surface, not just along high-symmetry directions. Both pushing and pulling modes were observed in the height profile of the tip. We assembled two artificial structures, demonstrating the reliability of the manipulation procedures. Structures remained intact to a temperature of at least 44 K.

• remoTES: A new design for the cryogenic NaI detectors of the COSINUS experiment

  L. Einfalt, G. Angloher, Mukund Raghunath Bharadwaj, I. Dafinei, N. Di Marco, F. Ferroni, S. Fichtinger, A. Filipponi, T. Frank, M. Friedl, A. Fuss, Z. Ge, M. Heikinheimo, K. Huitu, M. Kellermann, R. Maji , M. Mancuso, L. Pagnanini, F. Petricca, S. Pirro, F. Pröbst, G. Profeta, A. Puiu, F. Reindl, K. Schäffner, J. Schieck, D. Schmiedmayer, C. Schwertner, M. Stahlberg, A. Stendahl, M. Stukel , F. Wagner, S. Yue, V. Zema, Y. Zhu

  SciPost Phys. Proc. 12, 033 (2023) · published 4 July 2023 | Toggle abstract · pdf

  The increasing statistical significance of the DAMA/LIBRA annual modulation signal is a cause for tension in the field of dark matter direct detection. The COSINUS experiment aims at a model-independent cross-check of the DAMA/LIBRA signal claim, using NaI crystals operated as cryogenic scintillating calorimeters at millikelvin temperatures. Such a setup enables measurement of phonon and scintillation light signals via Transition Edge Sensors (TESs) and allows particle discrimination on an event-by-event basis. The non-standard properties of NaI cause an obstacle when attaching a TES directly onto the surface of the crystal. This can be overcome with the ``remoTES'' design, where the TES is attached to an external wafer crystal. We present the results from a first successful operation of NaI and other crystals as cryogenic calorimeters with the remoTES design.

• Timelike transition form factor for CP-odd Higgs boson production

  Ken Sasaki, Tsuneo Uematsu

  SciPost Phys. Proc. 7, 044 (2022) · published 22 June 2022 | Toggle abstract · pdf

  We investigate the production of CP-odd Higgs boson $A^0$ associated with a real $\gamma$ in $e^+e^-$ collisions. Because of the properties of $A^0$ coupling to the other fields, the main contribution comes from the top-quark triangle loop diagrams. We obtain the timelike transition form factor which describes the production amplitude of $A^0$ in the $e^+e^-$ collisions. This timelike transition form factor is related to the spacelike transition form factor relevant for the $A^0$ production in $e^-\gamma$ collisions. It turns out that the possible extra contributions from chargino-sneutrino and neutralino-selectron box diagrams do not give sizable effects.

• Black hole mergers in holographic space time models of cosmology

  Anish Suresh, Tom Banks

  SciPost Phys. Core 7, 057 (2024) · published 22 August 2024 | Toggle abstract · pdf

  Holographic space-time, a theory of quantum gravity that generalizes string theory and quantum field theory, predicts black holes in the early matter-dominated era of its models of inflation. Before these black holes can decay, there is a chance that enough of these particles merge to produce radiation visible today in the Cosmic Microwave background. To discover if this is the case, we perform a rudimentary computer simulation. We show that no problematic black holes are formed by mergers in the Holographic Space-time models of inflation. However, we conclude that tiny bound structures containing black holes remnants form in this theory unconditionally. Since black hole decay products are mostly massive standard model particles, and perhaps their superpartners, the fate of these structures is a complicated dynamical problem that requires further study. It suggests the possibility of primordial structures on the order of the horizon size at the beginning of the radiation dominated era. This is about $10^9 L_P$ in the current model.

• Radiative asymptotic symmetries of 3D Einstein-Maxwell theory

  Jorrit Bosma, Marc Geiller, Sucheta Majumdar, Blagoje Oblak

  SciPost Phys. 16, 092 (2024) · published 3 April 2024 | Toggle abstract · pdf

  We study the null asymptotic structure of Einstein-Maxwell theory in three-dimensional (3D) spacetimes. Although devoid of bulk gravitational degrees of freedom, the system admits a massless photon and can therefore accommodate electromagnetic radiation. We derive fall-off conditions for the Maxwell field that contain both Coulombic and radiative modes with non-vanishing news. The latter produces non-integrability and fluxes in the asymptotic surface charges, and gives rise to a non-trivial 3D Bondi mass loss formula. The resulting solution space is thus analogous to a dimensional reduction of 4D pure gravity, with the role of gravitational radiation played by its electromagnetic cousin. We use this simplified setup to investigate choices of charge brackets in detail, and compute in particular the recently introduced Koszul bracket. When the latter is applied to Wald-Zoupas charges, which are conserved in the absence of news, it leads to the field-dependent central extension found earlier in [Class. Quantum Gravity 32, 245001 (2015)]. We also consider (Anti-)de Sitter asymptotics to further exhibit the analogy between this model and 4D gravity with leaky boundary conditions.