Publications

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• Flow decorrelation in heavy-ion collisions at $\sqrt{s_{_{\rm NN}}}$=27 and 200 GeV with 3D event-by-event viscous hydrodynamics

  Jakub Cimerman, Iurii Karpenko, Boris Tomasik, Barbara Antonina Trzeciak

  SciPost Phys. Proc. 10, 031 (2022) · published 11 August 2022 | Toggle abstract · pdf

  We present the first calculation of longitudinal decorrelation of anisotropic flow at RHIC Beam Energy Scan (BES) energies using event-by-event viscous hydrodynamic model (vHLLE), with two different initial states (GLISSANDO2 and UrQMD) and hadronic cascade. We investigate the origin of the observed decorrelation by checking separately flow angle and flow magnitude decorrelation and by calculating decorrelation in the initial state eccentricity.

• Top quark mass corrections to single and double Higgs boson production in gluon fusion

  Joshua Davies

  SciPost Phys. Proc. 7, 031 (2022) · published 21 June 2022 | Toggle abstract · pdf

  In this talk we discuss recent computations of the top quark mass dependence of QCD amplitudes describing Higgs boson production in gluon fusion. We compute terms in the expansion for a large top quark mass, which reduces the Feynman diagrams to products of massless integrals and massive tadpole integrals which contain the top mass dependence. In particular we discuss the real and virtual corrections to double Higgs production at NNLO, and the virtual corrections to single Higgs production at N3LO.

• A measurement of the proton plus helium spectrum of cosmic rays in the TeV region with HAWC

  Juan Carlos Arteaga-Velázquez on behalf of the HAWC collaboration

  SciPost Phys. Proc. 13, 015 (2023) · published 28 September 2023 | Toggle abstract · pdf

  HAWC is an air-shower detector designed to study TeV gamma and cosmic rays. The observatory is composed of a 22000 $m^2$ array of 300 water Cherenkov tanks (4.5 m deep x 7.3 m diameter) with 4 photomultipliers (PMT) each. The instrument registers the number of hit PMTs, the timing information and the total charge at the PMTs during the event. From these data, shower observables such as the arrival direction, the core position at ground, the lateral age and the primary energy are estimated. In this work, we study the distribution of the shower age vs the primary energy of a sample of shower data collected by HAWC from June 2015 to June 2019 and employ a shower-age cut based on predictions of QGSJET-II-04 to separate a subsample of events dominated by H and He primaries. Using these data and a dedicated analysis, we reconstruct the cosmic ray spectrum of H+He from 6 to 158 TeV, which shows the presence of a softening at around 24 TeV with a statistical significance of 4.1$\sigma$.

• Composition dependence of the specific heat of FeSi

  Carolina Burger, Andreas Bauer, Christian Pfleiderer

  SciPost Phys. Proc. 11, 020 (2023) · published 6 June 2023 | Toggle abstract · pdf

  Recently, a high-mobility surface conduction channel and in-gap states were identified in the correlated small-gap semiconductor FeSi using electrical transport measurements and high-resolution tunneling spectroscopy. The mobility of the charge carriers in the surface channel is quantitatively reminiscent of topological insulators, but displays a lack of sensitivity to the presence of ferromagnetic impurities as studied by means of a series of single crystals with slightly different starting compositions. Here, we report measurements of the specific heat of these crystals. At low temperatures, a shallow maximum is observed in the specific heat divided by temperature. This maximum is suppressed under magnetic field, characteristic of a Schottky anomaly associated with magnetic impurities. In comparison, the height of this maximum decreases with increasing initial iron content.

• Renormalization approach to the superconducting Kondo model

  Steffen Sykora, Tobias Meng

  SciPost Phys. 13, 016 (2022) · published 12 August 2022 | Toggle abstract · pdf

  An approach to bound states based on unitary transformations of Hamiltonians is presented. The method is applied to study the interaction between electrons in a BCS $s$-wave superconductor and a quantum spin. It is shown that known results from the t-matrix method and numerical studies are reproduced by this new method. As a main advantage, the method can straightforwardly be extended to study the topological properties of combined bound states in chains of many magnetic impurities. It also provides a uniform picture of the interplay between the Yu-Shiba-Rusinov (YSR) bound states and the Kondo singlet state.

• Dynamic hysteresis across a dissipative multi-mode phase transition

  Marvin Röhrle, Jens Benary, Erik Bernhart, Herwig Ott

  SciPost Phys. 16, 158 (2024) · published 28 June 2024 | Toggle abstract · pdf

  Dissipative phase transitions are characteristic features in open quantum systems. Key signatures are the dynamical switching between different states in the vicinity of the phase transition and the appearance of hysteresis. Here, we experimentally study dynamic sweeps across a first order dissipative phase transition in a multi-mode driven-dissipative system. In contrast to previous studies, we perform sweeps of the dissipation strength instead of the driving strength. We extract exponents for the scaling of the hysteresis area in dependence of the sweep time and study the $g^{(2)}(0)$ correlations, which show non-trivial behavior. By changing the temperature of the system we investigate the importance of coherently pumping the system. We compare our results to numerical calculations done for a single mode variant of the system, and find surprisingly good agreement. Furthermore, we identify and discuss the differences between a scan of the dissipation strength and a scan of the driving strength.

• Measuring single-top-associated Higgs production at the HL-LHC

  Henning Bahl

  SciPost Phys. Proc. 8, 010 (2022) · published 11 July 2022 | Toggle abstract · pdf

  Precision measurements of top-associated Higgs production are an important ingredient to unravel the $\mathcal{CP}$ nature of the Higgs boson. In this work, we constraint the $\mathcal{CP}$ nature of the top-Yukawa coupling taking into account all relevant inclusive and differential Higgs boson measurements. Based upon this fit, we show that it is crucial to disentangle single- and di-top-associated Higgs production for tightening indirect constraints on a $\mathcal{CP}$-odd top-Yukawa coupling in the future. In this context, we propose an analysis strategy for measuring $tH$ production at the HL-LHC without relying on assumptions about the Higgs $\mathcal{CP}$ character.

• Reweighting the quark Sivers function with STAR jet data

  Carlo Flore, Maria Elena Boglione, Umberto D'Alesio, Josè Osvaldo Gonzalez-Hernandez, Francesco Murgia, Alexei Prokudin

  SciPost Phys. Proc. 8, 034 (2022) · published 11 July 2022 | Toggle abstract · pdf

  The Bayesian reweighting procedure is applied for the first time to a TMD distribution, the quark Sivers function extracted from SIDIS data. By exploiting the recent published single spin asymmetry data for the inclusive jet production in $p^\uparrow p$ collisions from the STAR collaboration at RHIC, we show how such a procedure allows to incorporate the information contained in the new data set, without the need of re-fitting, and to explore a much wider $x$ region compared to SIDIS measurements. The reweighting method is also extended to the case of asymmetric errors, and the results show a significant improvement on the knowledge of the quark Sivers function.

• The origin and evolution of wide Jupiter mass binary objects in young stellar clusters

  Simon Portegies Zwart, Erwan Hochart

  SciPost Astro. 3, 001 (2024) · published 2 July 2024 | Toggle abstract · pdf

  The recently observed population of 540 free-floating Jupiter-mass objects, including 40 dynamically soft pairs, and two triples, in the Trapezium cluster have raised interesting questions on their formation and evolution. We test various scenarios for the origin and survivability of these free floating Jupiter-mass objects and Jupiter-mass Binary Objects (JuMBOs) in the Trapezium cluster. The numerical calculations are performed by direct $N$-body integration of the stars and planets in the Trapezium cluster starting with a wide variety of planets in various configurations. We discuss four models: $\mathcal{SPP}$, in which selected stars have two outer orbiting Jupiter-mass planets; $\mathcal{SPM}$, where selected stars are orbited by Jupiter-mass planet-moon pairs; $\mathcal{ISF}$ in which JuMBOs form in situ with the stars, and $\mathcal{FFC}$, where we introduce a population of free-floating single Jupiter-mass objects, but no initialised binaries. Models $\mathcal{FFC}$ and $\mathcal{SPP}$ fail to produce enough JuMBOs. Models $\mathcal{SPM}$ can produce sufficient free-floaters and JuMBOs, but requires unusually wide orbits for the planet-moon system around the star. The observed JuMBOs and free-floating Jupiter-mass objects in the Trapezium cluster are best reproduced if they formed in pairs and as free-floaters together with the other stars in a smooth (Plummer) density profile with a virial radius of $\sim 0.5$pc. A fractal (with fractal dimension 1.6) stellar density distribution also works, but requires relatively recent formations ($\raise-.5ex\hbox{$\buildrel>\over\sim$} 0.2$Myr after the other stars formed) or a high ($\raise-.5ex\hbox{$\buildrel>\over\sim$} 50$%) initial binary fraction. This would make the primordial binary fraction of JuMBOs even higher than the already large observation fraction of $\sim 8$% (42/540). The fraction of JuMBOs will continue to drop with time, and the lack of JuMBOs in Upper Scorpius could then result in its higher age, causing more JuMBOs to be ionized. We then also predict that the interstellar density of Jupiter-mass objects (mostly singles with some $\sim 2$% lucky surviving binaries) is $\sim 0.05$ per pc$^{-3}$ (or around 0.24 per star).

• Linking ladder operators for the Rosen-Morse and Pöschl-Teller systems

  Simon Garneau-Desroches, Véronique Hussin

  SciPost Phys. Proc. 14, 026 (2023) · published 24 November 2023 | Toggle abstract · pdf

  An analysis of the realizations of the ladder operators for the Rosen-Morse and Pöschl-Teller quantum systems is carried out. The failure of the algebraic method of construction in the general Rosen-Morse case is exposed and explained. We present the reduction of a recently obtained set of $(2n ± 1)$-th-order Rosen-Morse ladder operators to the usual first-order realization for the Pöschl-Teller case known in the literature.