Publications

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Quasi-free limit in the deuteron-deuteron three-body break-up process

R. Ramazani-Sharifabadi, H. R. Amir-Ahmadi, M. T. Bayat, I. Ciepał, M. Eslami-Kalantari, N. Kalantar-Nayestanaki, St. Kistryn, A. Kozela, M. Mahjour-Shafiei, H. Mardanpour, J. G. Messchendorp, M. Mohammadi-Dadkan, A. Ramazani-Moghaddam-Arani, E. Stephan, and H. Tavakoli-Zaniani

SciPost Phys. Proc. 3, 057 (2020) · published 1 April 2020 | · pdf

Detailed measurements of vector and tensor analyzing powers of the 2H(d, dp)n breakup process are presented. The data were obtained using a polarized deuteron-beam with an energy of 65 MeV/nucleon impinging on a liquid-deuterium target. The experiment was conducted at the AGOR facility at KVI using the BINA 4Pi-detection system. The focus of this contribution is to analyze data of the dd scattering process in the regime at which the neutron acts as a spectator, which we refer to as the quasi-free (QF) limit. To achieve this, events for which the final-state deuteron and proton are coplanar have been analyzed and the data have been sorted for various reconstructed momenta of the missing neutron. In the limit of vanishing neutron momentum and at small deuteron-proton momentum transfer, the data match very well with measured and predicted spin observables of the elastic deuteron-proton scattering process. The agreement deteriorates rapidly with increasing neutron momentum and deuteron-proton momentum transfer. The results of coplanar configurations in four-body phase space are compared with the results of recent available theoretical calculations based on the Single-Scattering Approximation.
Light thermal relics enabled by a second Higgs

Johannes Herms, Sudip Jana, Vishnu P. K., Shaikh Saad

SciPost Phys. Proc. 12, 046 (2023) · published 4 July 2023 | · pdf

Sub-GeV thermal relic dark matter typically requires the existence of a light mediator particle. We introduce the light two-Higgs-doublet portal, illustrated by a minimal UV-complete model for sub-GeV dark matter with kinematically forbidden annihilations into leptons. All new physics states in this scenario lie at or below the electroweak scale, affecting Higgs physics, the muon anomalous magnetic moment and potentially neutrino masses. Observation of radiative dark matter annihilation by future MeV gamma-ray telescopes would be key to unambiguously identify the scenario.
Hyperons - a strange key to the strong interaction

Karin Schoenning

SciPost Phys. Proc. 3, 027 (2020) · published 25 February 2020 | · pdf

Hyperons provide new angles on two of the most challenging problems in contempo- rary physics: a coherent and quantitative description of the strong interaction, and the matter-antimatter asymmetry of the Universe. In these proceedings, I will demonstrate the merits of hyperons as a diagnostic tool using two recent measurements by the BE- SIII experiment as an illustrative example. Furthermore, I will highlight the prospect of future hyperon studies with the next-generation experiment PAND
Response functions and cross sections for inclusive neutrino scattering off $^2$H, $^3$H and $^3$He

Alessandro Grassi, Jacek Golak, Roman Skibiński, Kacper Topolnicki, Henryk Witała, Hiroyuki Kamada, Laura Elisa Marcucci

SciPost Phys. Proc. 3, 031 (2020) · published 26 February 2020 | · pdf

For several decades there has been an interest in studying neutrino scattering on light nuclei, with the hope of increasing knowledge about the theory of weak interactions and electroweak unification. A study of several neutrino induced reactions on light nuclei ($^2$H, $^3$H and $^3$He) is presented here. The cross section for these reactions is evaluated using the nuclear response functions, which holds the information about the nuclear interactions and structure. This approach has been tested for break-up reactions on the deuteron before and is now extended to three-nucleon break-up reactions.
Azimuthal single- and double-spin asymmetries in semi-inclusive deep-inelastic lepton scattering by transversely polarized protons

Luciano L. Pappalardo, Gunar Schnell

SciPost Phys. Proc. 8, 024 (2022) · published 11 July 2022 | · pdf

A comprehensive set of azimuthal single-spin and double-spin asymmetries in semi- inclusive leptoproduction of pions, charged kaons, protons, and antiprotons from transversely polarized protons is presented. These asymmetries include the previously published HERMES results on Collins and Sivers asymmetries, the analysis of which has been extended to include protons and antiprotons and also to an extraction in a three-dimensional kinematic binning and enlarged phase space. They are complemented by corresponding results for the remaining single-spin and double-spin asymmetries for transverse target-polarization orientation.
Density-matrix mean-field theory

Junyi Zhang, Zhengqian Cheng

SciPost Phys. 17, 062 (2024) · published 23 August 2024 | · pdf

Mean-field theories have proven to be efficient tools for exploring diverse phases of matter, complementing alternative methods that are more precise but also more computationally demanding. Conventional mean-field theories often fall short in capturing quantum fluctuations, which restricts their applicability to systems with significant quantum effects. In this article, we propose an improved mean-field theory, density-matrix mean-field theory (DMMFT). DMMFT constructs effective Hamiltonians, incorporating quantum environments shaped by entanglements, quantified by the reduced density matrices. Therefore, it offers a systematic and unbiased approach to account for the effects of fluctuations and entanglements in quantum ordered phases. As demonstrative examples, we show that DMMFT can not only quantitatively evaluate the renormalization of order parameters induced by quantum fluctuations, but can also detect the topological quantum phases. Additionally, we discuss the extensions of DMMFT for systems at finite temperatures and those with disorders. Our work provides an efficient approach to explore phases exhibiting unconventional quantum orders, which can be particularly beneficial for investigating frustrated spin systems in high spatial dimensions.
State-of-the-art cross sections for $t\bar t H$: NNLO predictions matched with NNLL resummation and EW corrections

Roger Balsach, Alessandro Broggio, Simone Devoto, Andrea Ferroglia, Rikkert Frederix, Massimiliano Grazzini, Stefan Kallweit, Anna Kulesza, Javier Mazzitelli, Leszek Motyka, Davide Pagani, Benjamin D. Pecjak, Chiara Savoini, Tomasz Stebel, Malgorzata Worek, Marco Zaro

SciPost Phys. Comm. Rep. 10 (2025) · published 13 August 2025 | · pdf

We present new, state-of-the-art predictions for the associated production of the SM Higgs boson with top quarks, computed in accordance with the recommendations of the LHC Higgs Working Group. The NNLO QCD predictions, derived through suitable approximations of the two-loop virtual contribution, are supplemented with soft-gluon resummation up to NNLL accuracy. Two distinct resummation frameworks are employed – one based on direct QCD and the other on soft-collinear effective theory – and their features are compared in detail. These results are further combined with the complete-NLO corrections, yielding the most precise SM predictions for this process to date. The relevant sources of theoretical uncertainties are thoroughly estimated and discussed.
On currents in the $O(n)$ loop model

Jesper Lykke Jacobsen, Rongvoram Nivesvivat, Hubert Saleur

SciPost Phys. 16, 111 (2024) · published 24 April 2024 | · pdf

Using methods from the conformal bootstrap, we study the properties of Noether currents in the critical $O(n)$ loop model. We confirm that they do not give rise to a Kac-Moody algebra (for $n≠ 2$), a result expected from the underlying lack of unitarity. By studying four-point functions in detail, we fully determine the current-current OPEs, and thus obtain several structure constants with physical meaning. We find in particular that the terms $:\!J\bar{J}\!:$ in the identity and adjoint channels vanish exactly, invalidating the argument made in \[Nucl. Phys. B 419, 411 (1994)] that adding orientation-dependent interactions to the model should lead to continuously varying exponents in self-avoiding walks. We also determine the residue of the identity channel in the $JJ$ two-point function, finding that it coincides both with the result of a transfer-matrix computation for an orientation-dependent correlation function in the lattice model, and with an earlier Coulomb gas computation of Cardy [Nucl. Phys. B 265, 409 (1986)]. This is, to our knowledge, one of the first instances where the Coulomb gas formalism and the bootstrap can be successfully compared.
Properties of heavy mesons at finite temperature

Gloria Montaña, Angels Ramos, Laura Tolós

SciPost Phys. Proc. 3, 038 (2020) · published 26 February 2020 | · pdf

We study the properties of heavy mesons using a unitarized approach in a hot pionic medium, based on an effective hadronic theory. The interaction between the heavy mesons and pseudoscalar Goldstone bosons is described by a chiral Lagrangian at next-to-leading order in the chiral expansion and leading order in the heavy-quark mass expansion so as to satisfy heavy-quark spin symmetry. The meson-meson scattering problem in coupled channels with finite-temperature corrections is solved in a self-consistent manner. Our results show that the masses of the ground-state charmed mesons $D(0^-)$ and $D_s(1^-)$ decrease in a pionic environment at $T\neq 0$ and they acquire a substantial width. As a consequence, the behaviour of excited mesonic states (i.e. $D_{s0}^*(2317)^\pm$ and $D_0^*(2300)^{0,\pm}$), generated dynamically in our heavy-light molecular model, is also modified at $T\neq 0$. The aim is to test our results against Lattice QCD calculations in the future.
Effect of isospin averaging for $ppK^-$ kaonic cluster

Branislav Vlahovic, Igor Filikhin

SciPost Phys. Proc. 3, 040 (2020) · published 27 February 2020 | · pdf

The kaonic cluster $ppK^-$ is described by isospin-dependent $N{\bar K}$ potentials with significant difference between singlet and triplet components. The quasi-bound state energy of the system is calculated based on the configuration space Faddeev equations within isospin and averaged potential models. The isospin averaging of $ N{\bar K} $ potentials is used to simplify the isospin model to isospinless one. We show that three-body bound state energy $E_{3}$ has a lower bound within the isospin formalism due to relation $\left\vert E_{3}(V_{NN}=0)\right\vert<2\left\vert E_{2}\right\vert$, where $E_{2}$ is the binding energy of isospin singlet state of the $N{\bar K}$ subsystem. The averaged potential model demonstrates opposite relation between $|E_{2}|$ and $|E_{3}(V_{NN}=0)|$.

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