Publications

Order by: publication date number of citations

• Experimental input from $e^+e^-$ for $a_{\mu}$ light-by-light

  Yuping Guo on behalf of BESIII Collaboration

  SciPost Phys. Proc. 1, 054 (2019) · published 9 May 2019 | Toggle abstract · pdf

  The anomalous magnetic momentum of the muon, $a_{\mu}$, has been measured and calculated with a precision up to $~0.5$ ppm, but there is a 3 to 4 standard deviations between these two values. The uncertainty in the calculation is dominated by the hadronic part, including the hadronic vacuum polarization and the hadronic light-by-light. The meson transition form factors and the helicity amplitudes can be used as input or constraint to the calculation of the hadronic light-by-light contribution. Latest experimental studies of the transition form factors of $\pi^0$, $\eta$, and $\eta^{*}$ and the cross-section of $\gamma\gamma^*\to\pi^+\pi-$from $e^+e^-$ collider are presented.

• Quasiparticle disintegration in fermionic superfluids

  Senne Van Loon, Jacques Tempere, Hadrien Kurkjian

  SciPost Phys. 12, 108 (2022) · published 28 March 2022 | Toggle abstract · pdf

  We study the fermionic quasiparticle spectrum in a zero-temperature superfluid Fermi gas, and in particular how it is modified by different disintegration processes. On top of the disintegration by emission of a collective boson ($1\to2$, subject of a previous study, PRL 124, 073404), we consider here disintegration events where three quasiparticles are emitted ($1\to3$). We show that both disintegration processes are described by a $t$-matrix self-energy (as well as some highly off-resonant vacuum processes), and we characterize the associated disintegration continua. At strong coupling, we show that the quasiparticle spectrum is heavily distorted near the $1\to3$ disintegration threshold. Near the dispersion minimum, where the quasiparticles remain well-defined, the main effect of the off-shell disintegration processes is to shift the location of the minimum by a value that corresponds to the Hartree shift in the BCS limit. With our approximation of the self-energy, the correction to the energy gap with respect to the mean-field result however remains small, in contrast with experimental measurements.

• Measurements of charm production in pp collisions with ALICE

  Tiantian Cheng

  SciPost Phys. Proc. 10, 030 (2022) · published 11 August 2022 | Toggle abstract · pdf

  The production of charm-hadrons at midrapidity in pp collisions at $\sqrt{s}$ = 5.02 and 13 TeV was recently measured by the ALICE Collaboration. The results show that the baryon-to-meson yield ratios differ from predictions where the hadronisation has been tuned to measurements obtained in $\rm e^{+}e^{-}$ and ep collisions for different charm-baryon species. These observations suggest that the charm fragmentation fractions are not universal and that the baryon-to-meson ratio depends on the collision systems. The results are compared to the predictions from Monte Carlo event generators and theoretical calculations.

• Political or environmental refugees? Re-examining the flight of the Vietnamese boat people, 1975-1995

  Saphia Fleury

  Mig. Pol. 4, 001 (2025) · published 15 May 2025 | Toggle abstract · pdf

  This paper examines ecocide in South Vietnam during the Vietnam War (1954 to 1975) and the extent to which it drove the ‘boat people’ mass migration from Vietnam from 1975 to the mid-1990s. The exodus has become an archetype of a ‘political’ refugee flow, based on a Western Cold War narrative of people fleeing en masse from the persecution of an autocratic Communist regime. This paper challenges this assumption, showing how the interplay of environmental factors with political and military decisions contributed to the post-war exodus. These findings are reached through the analysis of historical primary sources as well as 229 oral history interviews, some 40 per cent of which were conducted with former child refugees. The implications have contemporary relevance because modern migration flows are frequently mixed, and climate change is further complicating the reasons that people leave their homes and their ability to access asylum. The conclusion argues that ecocide can, in some contexts, be considered a form of persecution for the purpose of refugee determination.

• Recent results on top quark mass and properties and rare/anomalous top quarks interactions in CMS

  Sebastian Wuchterl

  SciPost Phys. Proc. 8, 120 (2022) · published 13 July 2022 | Toggle abstract · pdf

  The amount of data collected by the CMS experiment at the CERN LHC in the second data taking period provides the possibility to study absolute and differential cross sections of top quark interaction processes with high precision. Utilizing these results, fundamental standard model parameters such as the top quark mass are extracted. Moreover, given standard model measurements are interpreted in the context of Beyond the standard model theories. Recent results on top quark properties and rare or anomalous top quark interactions by CMS are presented in these proceedings. Furthermore, the implications of experimental results to effective field theory are discussed.

• Extracting quantum-critical properties from directly evaluated enhanced perturbative continuous unitary transformations

  L. Schamriß, M. R. Walther, K. P. Schmidt

  SciPost Phys. 17, 094 (2024) · published 26 September 2024 | Toggle abstract · pdf

  Directly evaluated enhanced perturbative continuous unitary transformations (deepCUTs) are used to calculate non-perturbatively extrapolated numerical data for the ground-state energy and the energy gap. The data coincide with numerical evaluations of the truncated perturbative series and provide robust extrapolations beyond the perturbative regime. We develop a general scheme to extract quantum-critical properties from the deepCUT data based on critical scaling and a strict correspondence between the truncation used for deepCUT and the length scale of correlations at the critical point. We apply our approach to transverse-field Ising models (TFIMs) as paradigmatic systems for quantum phase transitions of various universality classes depending on the lattice geometry and the choice of antiferromagnetic or ferromagnetic coupling. In particular, we focus on the quantum phase diagram of the bilayer antiferromagnetic TFIM on the triangular lattice with an Ising-type interlayer coupling. Without a field, the model is known to host a classically disordered ground state, and in the limit of decoupled layers it exhibits the 3d-XY 'order by disorder' transition of the corresponding single-layer model. Our starting point for the unknown parts of the phase diagram is a high-order perturbative calculation about the limit of isolated dimers where the model is in a gapped phase.

• 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.

• Energy-Momentum Tensor Form Factors in QED

  Simone Rodini, Andreas Metz, Barbara Pasquini

  SciPost Phys. Proc. 8, 122 (2022) · published 13 July 2022 | Toggle abstract · pdf

  We present the results for the Energy-Momentum Tensor (EMT) form factor D(t) at oneloop accuracy in quantum electrodynamics for an electron state. We report the the results in the case of both zero and nonzero photon mass. Moreover, individual electron and photon contributions to the EMT are investigated.

• Non-linear photoconductivity of strongly driven graphene

  Lukas Broers, Ludwig Mathey

  SciPost Phys. 18, 199 (2025) · published 20 June 2025 | Toggle abstract · pdf

  We present the non-linear DC photoconductivity of graphene under strong infra-red (IR) radiation. The photoconductivity is obtained as the response to a strong DC electric field, with field strengths outside of the linear-response regime, while the IR radiation is described by a strong AC electric field. The conductivity displays two distinct regimes in which either the DC or the AC field dominates. We explore these regimes and associate them with the dynamics of driven Landau-Zener quenches in the case of a large DC field. In the limit of a large AC field, we describe the conductivity in a Floquet picture and compare the results to the closely related Tien-Gordon effect. We present analytical calculations for the non-linear differential photoconductivity, for both regimes based on the corresponding mechanisms. As part of this discussion of the non-equilibrium state of graphene, we present analytical estimates of the conductivity of undriven graphene as a function of temperature and DC bias field strength that show very good agreement with our simulations.

• The fermionic double smeared null energy condition

  Duarte Fragoso, Lihan Guo

  SciPost Phys. Core 8, 045 (2025) · published 26 June 2025 | Toggle abstract · pdf

  Energy conditions are crucial for understanding why exotic phenomena such as traversable wormholes and closed timelike curves remain elusive. In this paper, we prove the Double Smeared Null Energy Condition (DSNEC) for the fermionic free theory in 4-dimensional flat Minkowski spacetime, extending previous work on the same energy condition for the bosonic case [J. R. Fliss and B. Freivogel, SciPost Phys. 12, 084 (2022); J. R. Fliss et al., SciPost Phys. 14, 024 (2023)] by adapting Fewster and Mistry's method [C. J. Fewster and B. Mistry, Phys. Rev. D 68, 105010 (2003)] to the energy-momentum tensor $T_{++}$. A notable difference from previous works lies in the presence of the $\gamma_0 \gamma_+$ matrix in $T_{++}$, causing a loss of symmetry. This challenge is addressed by making use of its square-root matrix. We provide explicit analytic results for the massless case as well as numerical insights for the mass-dependence of the bound in the case of Gaussian smearing.