Publications

Order by: publication date number of citations

• Photon-ALP oscillations at CTA energies

  M. Kachelriess, J. Tjemsland

  SciPost Phys. Proc. 12, 043 (2023) · published 4 July 2023 | Toggle abstract · pdf

  Axions and axion-like-particles (ALPs) are well motivated beyond the standard model particles that can explain a variety of unsolved problems in physics, such as the strong CP problem and the nature of dark matter. These particles are characterised by their two-photon coupling, which leads to so-called photon-ALP oscillation as photons propagate through an external magnetic field. Such oscillations lead to characteristic signatures in the energy spectrum of high-energy photons from astrophysical sources, allowing us to probe the existence of ALPs and possibly dark matter. We review the signatures from ALPs in photon spectra and discuss a new method that can be used to directly search for the energy dependence of the oscillations. The focus is on photons at TeV-energies relevant for the upcoming Cherenkov Telescope Array (CTA).

• A pitfall in applying non-anticommuting $γ_5$ in $q\overline{q} \rightarrow ZH$ amplitudes

  Taushif Ahmed

  SciPost Phys. Proc. 7, 008 (2022) · published 20 June 2022 | Toggle abstract · pdf

  In computing the two-loop QCD corrections to a class of Feynman diagrams for the process $q\overline{q} \rightarrow ZH$ in Higgs effective field theory, we discover a striking phenomenon. We find the need for an additional local composite operator in the renormalised Lagrangian while employing a non-anticommuting $\gamma_5$ in dimensional regularisation. The computation using anticommuting $\gamma_5$, however, does not require any such amendment.

• Current stage of studies of the star configurations at intermediate energies with the use of the BINA detector

  A. Wilczek, A. Szadzinski, K. Bodek, I. Ciepal, M. Eslami-Kalantari, N. Kalantar-Nayestanaki, G. Khatri, St. Kistryn, B. Klos, A. Kozela, J. Kubos, P. Kulessa, A. Lobejko, A. Magiera, H. Mardanpour, J. Messchendorp, I. Mazumdar, W. Parol, A. Ramazani-Moghaddam-Aran, R. Ramazani-Sharifabadi, D. Rozpedzik, I. Skwira-Chalot, E. Stephan, B. Wloch, A. Wronska, J. Zejma

  SciPost Phys. Proc. 3, 005 (2020) · published 24 February 2020 | Toggle abstract · pdf

  The Space Star Anomaly in proton-deuteron breakup cross-section occurs at energies of about 10 MeV. Data for higher energies are sparse. Therefore, a systematic scan over star configurations in the range of intermediate energies between 50 and 100 MeV/nucleon is carried out on the basis of data collected with the large acceptance BINA detector. The preliminary cross section results for forward star configurations at 80 MeV/nucleon slightly surpass the theoretical calculations, but the systematic uncertainties are still under study. Also, a new variable describing rotation of star configurations is proposed.

• Determination of phase space region for cross-check validation of the neutron detection in the BINA experiments

  B. Włoch, K. Bodek, I. Ciepał, M. Eslami-Kalantari, J. Golak, N. Kalantar-Nayestanaki, G. Khatri, St. Kistryn, B. Kłos, A. Kozela, J. Kuboś, P. Kulessa, A. Łobejko, A. Magiera, H. Mardanpour, J. Messchendorp, I. Mazumdar, W. Parol, A. Ramazani-Moghaddam-Arani, D. Rozpędzik, R. Skibiński, I. Skwira-Chalot, E. Stephan, A. Wilczek, H. Witała, A Wrońska, J. Zejma

  SciPost Phys. Proc. 3, 006 (2020) · published 24 February 2020 | Toggle abstract · pdf

  Deuteron breakup reactions are basic laboratories for testing nuclear force models. Recent improvements in the data analysis allow for direct identification of neutrons in the BINA detection setup. This opens up the opportunity to study new aspects of few-nucleon system dynamics like charge dependence of nuclear force or Coulomb interaction. In this paper we determine regions along the kinematical curves where differential cross section of deuteron-proton breakup reactions can be measured by the proton-neutron and proton-proton coincidences simultaneously. This is particularly useful for validation of the neutron detection technique.

• Global fits of Dirac dark matter effective field theories

  Ankit Beniwal (On behalf of the GAMBIT Collaboration)

  SciPost Phys. Proc. 12, 044 (2023) · published 4 July 2023 | Toggle abstract · pdf

  In this proceeding, we present results from a global fit of Dirac fermion dark matter (DM) effective field theory (EFT) based on arXiv:2106.02056 using the GAMBIT framework. Here we show results only for the dimension-6 operators that describe the interactions between a gauge-singlet Dirac fermion and Standard Model quarks. Our global fit combines the latest constraints from Planck, direct and indirect DM detection, and the LHC. For DM mass below 100 GeV, it is impossible to simultaneously satisfy all constraints while maintaining the EFT validity at high energies. For higher masses, however, large regions of parameter space remain viable where the EFT is valid and saturates the observed DM abundance.

• Rainbow chains and numerical renormalisation group for accurate chiral conformal spectra

  Attila Szabó

  SciPost Phys. 19, 075 (2025) · published 26 September 2025 | Toggle abstract · pdf

  Based on the relationship between reduced and thermal density matrices in conformal field theory (CFT), we show that the entanglement spectrum of a conformal critical chain with exponentially decaying terms consists of conformal towers of the associated chiral CFT, with only weak finite-size effects. Through free-fermion and interacting examples, we show that these entanglement spectra present a reliable method to extract detailed CFT spectra from single wave functions without access to the parent Hamiltonian. We complement our method with a Wilsonian numerical renormalisation group algorithm for solving interacting, exponentially decaying chain Hamiltonians.

• Status and prospects of the JUNO experiment

  Matthias Raphael Stock, on behalf of the JUNO collaboration

  SciPost Phys. Proc. 17, 020 (2025) · published 23 July 2025 | Toggle abstract · pdf

  The Jiangmen Underground Neutrino Observatory (JUNO) is a multi-purpose neutrino experiment currently under construction in China. It is located 52.5 km away from two nuclear power plants in a newly constructed 700-m-deep underground laboratory. JUNO will be the largest liquid scintillator (LS) detector in the world comprising 20 kt of ultra-pure LS filled in an acrylic sphere. Its main goal is to determine the neutrino mass ordering by measuring the energy spectrum of reactor neutrinos with highest accuracy. In addition, JUNO will cover precision measurements of oscillation parameters and several aspects in the field of astroparticle physics. Data taking will start in late 2024.

• Study of charmonium(-like) spectroscopy and decay at BESIII

  Weimin Song, Honghong Zhang

  SciPost Phys. Proc. 15, 017 (2024) · published 3 April 2024 | Toggle abstract · pdf

  The recent results on Charmonium and Charmonium-like states at BESIII are reviewed, including the observation of $\rm Z_{cs}(3985)$ state, the study of the new decay modes of $\psi_2(3823)$ state, observation of resonance structure in $\rm e^+e^- \to \pi^+\pi^-\psi_2(3823)$ process, the study of the $\rm e^+e^- \to K^+K^-J/\psi$ process, cross section measurement of $\rm e^+e^- \to \omega\pi^0$ and $\omega\eta$ process, branching fraction measurement of $\psi(3686)\to\bar{\Sigma}^0\Lambda + c.c.$ process. Decay channels for $\chi_{cJ} \to \Lambda\bar{\Lambda}$, $\chi_{cJ} \to \Lambda\bar{\Lambda}\eta$, $\psi(3686) \to \Lambda\bar{\Lambda}\omega$ and $\eta_c(2S)\to3(\pi^+\pi^-)$ are also discussed. The property of the spin singlet P wave Charmonium state, $\rm h_c$ is also reported.

• All fractional Shapiro steps in the RSJ model with two Josephson harmonics

  Pavel N. Tsarev, Yakov V. Fominov

  SciPost Phys. 19, 148 (2025) · published 8 December 2025 | Toggle abstract · pdf

  Synchronization between the internal dynamics of the superconducting phase in a Josephson junction (JJ) and an external ac signal is a fundamental physical phenomenon, manifesting as constant-voltage Shapiro steps in the current-voltage characteristic. Mathematically, this phase-locking effect is captured by the Resistively Shunted Junction (RSJ) model, an important example of a nonlinear dynamical system. The standard RSJ model considers an overdamped JJ with a sinusoidal (single-harmonic) current-phase relation (CPR) in the current-driven regime with a monochromatic ac component. While this model predicts only integer Shapiro steps, the inclusion of higher Josephson harmonics is known to generate fractional Shapiro steps. In this paper, we show that only two Josephson harmonics in the CPR are sufficient to produce all possible fractional Shapiro steps within the RSJ framework. Using perturbative methods, we analyze the amplitudes of these fractional steps. Furthermore, by introducing a phase shift between the two Josephson harmonics, we reveal an asymmetry between positive and negative fractional steps—a signature of the Josephson diode effect.

• Pseudospectral implementation of the Einstein-Maxwell system

  Jorge Expósito Patiño, Hannes Robert Rüter, David Hilditch

  SciPost Phys. 19, 112 (2025) · published 27 October 2025 | Toggle abstract · pdf

  Electromagnetism plays an important role in a variety of applications in gravity that we wish to investigate. To that end, in this work, we present an implementation of the Maxwell equations within the adaptive-mesh pseudospectral numerical relativity code BAMPS. We perform a thorough analysis of the evolution equations as a first order symmetric hyperbolic system of PDEs. This includes both the construction of the characteristic variables for use in our penalty boundary communication scheme, as well as radiation controlling, constraint preserving outer boundary conditions which, for the first time in a numerical context, are shown to be boundary-stable. After choosing a formulation of the Maxwell constraints that we may solve for initial data, we move on to show a suite of numerical tests. Our simulations, both within the Cowling approximation, and in full non-linear evolution, demonstrate rapid convergence of error with resolution, as well as consistency with known quasinormal decay rates on the Kerr background. Finally we evolve the electrovacuum equations of motion with strong data, a good representation of typical critical collapse runs.