Publications

Order by: publication date number of citations

• Exact physical quantities of a competing spin chain in the thermodynamic limit

  Pengcheng Lu, Yi Qiao, Junpeng Cao, Wen-Li Yang

  SciPost Phys. 15, 060 (2023) · published 10 August 2023 | Toggle abstract · pdf

  We study the exact physical quantities of a competing spin chain which contains many interesting and meaningful couplings including the nearest neighbor, next nearest neighbor, chiral three spins, Dzyloshinsky-Moriya interactions and unparallel boundary magnetic fields in the thermodynamic limit. We obtain the density of zero roots, surface energies and elementary excitations in different regimes of model parameters. Due to the competition of various interactions, the surface energy and excited spectrum show many different pictures from those of the Heisenberg spin chain.

• The strong coupling from $e^+e^-\to$~hadrons

  Diogo Boito, Maarten Golterman, Alex Keshavarzi, Kim Maltman, Daiskuke Nomura, Santiago Peris, Thomas Teubner

  SciPost Phys. Proc. 1, 035 (2019) · published 21 February 2019 | Toggle abstract · pdf

  We use a new compilation of the hadronic $R$-ratio from available data for the process $e^+e^-\to$ hadrons below the charm mass to determine the strong coupling $\alpha_s$, using finite-energy sum rules. Quoting our results at the $\tau$ mass to facilitate comparison to the results obtained from similar analyses of hadronic $\tau$-decay data, we find $\alpha_s(m_\tau^2)=0.298\pm 0.016\pm 0.006$ in fixed-order perturbation theory, and $\alpha_s(m_\tau^2)=0.304\pm 0.018\pm 0.006$ in contour-improved perturbation theory, where the first error is statistical, and the second error combines various systematic effects. These values are in good agreement with a recent determination from the OPAL and ALEPH data for hadronic $\tau$ decays. We briefly compare the $R(s)$-based analysis with the $\tau$-based analysis.

• VERITAS highlights of observations and results

  Sonal R. Patel for the VERITAS collaboration

  SciPost Phys. Proc. 13, 035 (2023) · published 29 September 2023 | Toggle abstract · pdf

  Located in southern Arizona, VERITAS is amongst the most sensitive detectors for astrophysical very high energy (VHE; E>100 GeV) gamma rays and has been operational since April 2007. We highlight some recent results from VERITAS observations. These include the long-term observations of the gamma-ray binaries HESS J0632+057 and LS I +61° 303, the observations of the Galactic Center region, and of the supernova remnant Cas A. We discuss the results from a decade of multi-wavelength observations of the blazar 1ES 1215+303, the EHT 2017 campaign on the M87 galaxy, the discovery of 3C 264 in VHE, and the observation of three flaring quasars. Brief highlights of the indirect dark matter searches and targets-of-opportunity (ToO) observations are also discussed. The ToO observations allow for rapid follow-up of multi-messenger alerts and astrophysical transients.

• Collective dynamics of densely confined active polar disks with self- and mutual alignment

  Weizhen Tang, Yating Zheng, Amir Shee, Guozheng Lin, Zhangang Han, Pawel Romanczuk, Cristián Huepe

  SciPost Phys. 19, 012 (2025) · published 8 July 2025 | Toggle abstract · pdf

  We study the emerging collective states in a simple mechanical model of a dense group of self-propelled polar disks with off-centered rotation, confined within a circular arena. Each disk presents self-alignment towards the sum of contact forces acting on it, resulting from disk-substrate interactions, while also displaying mutual alignment with neighbors due to having its center of rotation located a distance $R$ behind its centroid, so that central contact forces can also introduce torques. The effect of both alignment mechanisms produces a variety of collective states that combine high-frequency localized circular oscillations with low-frequency milling around the center of the arena, in fluid or solid regimes. We consider cases with small/large $R$ values, isotropic/anisotropic disk-substrate damping, smooth/rough arena boundaries, different densities, and multiple systems sizes, showing that the emergent collective states that we identify are robust, generic, and potentially observable in real-world natural or artificial systems.

• Workshop on Tau Lepton Physics: $\mathbf{30^{th}}$ Anniversary

  Antonio Pich

  SciPost Phys. Proc. 16, 001 (2025) · published 14 July 2025 | Toggle abstract · pdf

  The first Workshop on Tau Lepton Physics took place at Orsay in 1990. The evolution of the field and some physics highlights are briefly described, following the presentations discussed at the fifteen $\tau$ workshops that have been held since then.

• Spin of fractional quantum Hall neutral modes and “missing states” on a sphere

  Dung Xuan Nguyen, Dam Thanh Son

  SciPost Phys. 19, 131 (2025) · published 18 November 2025 | Toggle abstract · pdf

  A low-energy neutral quasiparticle in a fractional quantum Hall system appears in the latter's energy spectrum on a sphere as a series of many-body excited states labeled by the angular momentum $L$ and whose energy is a smooth function of $L$ in the limit of large sphere radius. We argue that the signature of a nonvanishing spin (intrinsic angular momentum) $s$ of the quasiparticle is the absence, in this series, of states with total angular momentum less than $s$. We reinterpret the missing of certain states, observed in an exact-diagonalization calculation of the spectrum of the $\nu=7/3$ FQH state in a wide quantum well as well as in many proposed wave functions for the excited states as a consequence of the spin-2 nature of the zero-momentum magnetoroton.

• Deriving experimental constraints on the scalar form factor in the second-class $\tau \to\eta \pi \nu$ mode

  Bachir Moussallam

  SciPost Phys. Proc. 16, 009 (2025) · published 14 July 2025 | Toggle abstract · pdf

  The rare second-class decay mode of the $\tau$ into $\eta\pi\nu$ could be observed for the first time at Belle II. It is important to try to derive a reliable evaluation of the branching fraction and of the energy distribution of this mode within the standard-model. Many predictions exist already in the literature which can differ by one to two orders of magnitude. Here, an approach based on a systematic use of the property of analyticity of form factors and scattering amplitudes in QCD is discussed. In particular, we will show that the scalar form factor in the $\tau$ decay can be related to photon-photon scattering and radiative $\phi$ decay amplitudes for which precise experimental measurements have been performed by the Belle and KLOE collaborations.

• Identifying the quantum properties of hadronic resonances using machine learning

  Jakub Filipek, Shih-Chieh Hsu, John Kruper, Kirtimaan Mohan, Benjamin Nachman

  SciPost Phys. Core 8, 039 (2025) · published 28 April 2025 | Toggle abstract · pdf

  With the great promise of deep learning, discoveries of new particles at the Large Hadron Collider (LHC) may be imminent. Following the discovery of a new Beyond the Standard model particle in an all-hadronic channel, deep learning can also be used to identify its quantum numbers. Convolutional neural networks (CNNs) using jet-images can significantly improve upon existing techniques to identify the quantum chromodynamic (QCD) ('color') as well as the spin of a two-prong resonance using its substructure. Additionally, jet-images are useful in determining what information in the jet radiation pattern is useful for classification, which could inspire future taggers. These techniques improve the categorization of new particles and are an important addition to the growing jet substructure toolkit, for searches and measurements at the LHC now and in the future.

• Towards two- and three-loop QCD corrections to the width difference in $B_s-\bar{B}_s$ mixing

  Vladyslav Shtabovenko

  SciPost Phys. Proc. 7, 025 (2022) · published 21 June 2022 | Toggle abstract · pdf

  In this work we address the issue of large perturbative uncertainties in the theory prediction for $\Delta \Gamma_s$, the width difference in the $B^0_s - \bar{B}^0_s$ mixing process. To this aim we complete important steps towards the full analytic result for the previously unknown Wilson coefficients from the matching between $|\Delta B|=1$ and $|\Delta B|=2$ effective Hamiltonians at next-to-next-leading order (NNLO) in the strong coupling constant. We provide a thorough discussion of technical and conceptual difficulties behind this computation and give an outlook regarding the availability of the new NNLO theory prediction for $\Delta \Gamma_s$.

• Measurements of sub-jet fragmentation with ALICE

  James Mulligan

  SciPost Phys. Proc. 10, 020 (2022) · published 10 August 2022 | Toggle abstract · pdf

  High-energy jets offer rich opportunities to study quantum chromodynamics, from investigating the limits of perturbative calculability to constraining the emergent properties of the quark-gluon plasma (QGP). In these proceedings, we present new measurements of the fragmentation properties of jets. We report distributions of the sub-jet momentum fraction $z_r$ measured in pp and Pb-Pb collisions with ALICE at the Large Hadron Collider. These measurements serve as input to test the universality of jet fragmentation in the QGP, and offer a path to elucidate jet quenching effects in the large-$z$ region.