Publications

Order by: publication date number of citations

• Prompt hadroproduction of C-even quarkonia in the light-front $k_T$ -factorization approach

  Wolfgang Schäfer, Izabela Babiarz, Roman Pasechnik, Antoni Szczurek

  SciPost Phys. Proc. 8, 032 (2022) · published 11 July 2022 | Toggle abstract · pdf

  We present a new approach for the prompt production of quarkonia which is based on the $k_T$-factorization method. The production of even C-parity quarkonia proceeds via the fusion of two (off-shell) gluons. Especially in the kinematics of the LHCb experiment these processes are thus expected to be a sensitive probe of the small-x gluon distribution. We calculate the relevant off-shell matrix elements in terms of the light-front wave functions of the quarkonium states. We present our results for scalar and pseudoscalar charmonia and discuss photon transition form factors as well as cross sections for prompt hadroproduction. We compare our results for the $\eta_c$ to recent LHCb data.

• Recent Studies of Exotic Hadrons at the LHCb Experiment

  Gary Robertson

  SciPost Phys. Proc. 8, 030 (2022) · published 11 July 2022 | Toggle abstract · pdf

  Recent results on studies of exotic hadrons at the LHCb experiment are summarised. These are the observation of new resonances decaying to J/$\psi K^{+}$ and J/$\psi\phi$, evidence of a J/$\psi\Lambda$ structure and observation of excited $\Xi^{-}$ states in the $\Xi_{b}^{-}\to J/\psi \Lambda K^{-}$ decay and the study of $B_{s}^{0}\to J/\psi\pi^{+}\pi^{-}K^{+}K^{-}$ decays.

• 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 | Toggle abstract · 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.

• Entropy-driven phase behavior of associative polymer networks

  Lorenzo Rovigatti, Francesco Sciortino

  SciPost Phys. 15, 163 (2023) · published 16 October 2023 | Toggle abstract · pdf

  Polymer chains decorated with a fraction of monomers capable of forming reversible bonds form transient polymer networks that are important in soft and biological systems. If chains are flexible and the attractive monomers are all of the same species, the network formation occurs continuously as density increases. By contrast, it has been recently shown [Phys. Rev. Lett. 129, 047801 (2022)] that, if the attractive monomers are of two different and alternating types, the entropic gain of swapping intra-molecular bonds for inter-molecular connections induces a first order phase transition in the fully-bonded (i.e. low-temperature or, equivalently, large monomer-monomer attraction strength) limit and the network forms abruptly on increasing density. Here we use simulations to show that this phenomenon is robust with respect to thermal fluctuations, disorder and change in the polymer architecture, demonstrating its generality and likely relevance for the wide class of materials that can be modelled as associative (transient) polymer networks.

• Decay channels for double extremal black holes in four dimensions

  Johannes Aspman, Jan Manschot

  SciPost Phys. 16, 021 (2024) · published 22 January 2024 | Toggle abstract · pdf

  We explore decay channels for charged black holes with vanishing temperature in $\mathcal{N}=2$ supersymmetric compactifications of string theory. If not protected by supersymmetry, such extremal black holes are expected to decay as a consequence of the weak gravity conjecture. We concentrate on double extremal, non-supersymmetric black holes for which the values of the scalar fields are constant throughout space-time, and explore decay channels for which decay into BPS and anti-BPS constituents is energetically favorable. We demonstrate the existence of decay channels at tree level for large families of double extremal black holes. For specific charges, we also find stable non-supersymmetric black holes, suggesting recombination of (anti)-supersymmetric constituents to a non-supersymmetric object.

• Exponential enhancement of dark matter freezeout abundance

  Bibhushan Shakya

  SciPost Phys. Proc. 12, 070 (2023) · published 5 July 2023 | Toggle abstract · pdf

  A novel paradigm for thermal dark matter (DM), termed "bouncing dark matter", is presented. In canonical thermal DM scenarios, the DM abundance falls exponentially as the temperature drops below the mass of DM, until thermal freezeout occurs. This note explores a broader class of thermal DM models that are exceptions to this rule, where the DM abundance can deviate from the exponentially falling curve, and even rise exponentially, while in thermal equilibrium. Such scenarios can feature present day DM annihilation cross sections much larger than the canonical thermal target, improving the prospects for indirect detection of DM annihilation signals.

• The parastatistics of braided Majorana fermions

  Francesco Toppan

  SciPost Phys. Proc. 14, 046 (2023) · published 24 November 2023 | Toggle abstract · pdf

  This paper presents the parastatistics of braided Majorana fermions obtained in the framework of a graded Hopf algebra endowed with a braided tensor product. The braiding property is encoded in a t-dependent 4×4 braiding matrix $B_t$ related to the Alexander-Conway polynomial. The nonvanishing complex parameter t defines the braided parastatistics. At t=1 ordinary fermions are recovered. The values of t at roots of unity are organized into levels which specify the maximal number of braided Majorana fermions in a multiparticle sector. Generic values of t and the t=-1 root of unity mimick the behaviour of ordinary bosons.

• Forward trijet production and saturation

  Andreas van Hameren

  SciPost Phys. Proc. 8, 022 (2022) · published 11 July 2022 | Toggle abstract · pdf

  We present a multi-parton extension of the so-called small-$\boldsymbol{x}$ Improved Transverse Momentum Dependent (ITMD) factorization for hadroproduction of three or more jets in the forward rapidity region, allowing to study gluon saturation using such processes.

• Tensor network variational optimizations for real-time dynamics: Application to the time-evolution of spin liquids

  Ravi Teja Ponnaganti, Matthieu Mambrini, Didier Poilblanc

  SciPost Phys. 15, 158 (2023) · published 12 October 2023 | Toggle abstract · pdf

  Within the Projected Entangled Pair State (PEPS) tensor network formalism, a simple update (SU) method has been used to investigate the time evolution of a two-dimensional U(1) critical spin-1/2 spin liquid under Hamiltonian quench [Phys. Rev. B 106, 195132 (2022)]. Here we introduce two different variational frameworks to describe the time dynamics of SU(2)-symmetric translationally-invariant PEPS, aiming to improve the accuracy. In one approach, after using a Trotter-Suzuki decomposition of the time evolution operator in term of two-site elementary gates, one considers a single bond embedded in an environment approximated by a Corner Transfer Matrix Renormalization Group (CTMRG). A variational update of the two tensors on the bond is performed under the application of the elementary gate and then, after symmetrization of the site tensors, the environment is updated. In the second approach, a cluster optimization is performed on a finite (periodic) cluster, maximizing the overlap of the exact time-evolved state with a symmetric finite-size PEPS ansatz. Observables are then computed on the infinite lattice contracting the infinite-PEPS (iPEPS) by CTMRG. We show that the variational schemes outperform the SU method and remain accurate over a significant time interval before hitting the entanglement barrier. Studying the spectrum of the transfer matrix, we find that the asymptotic correlations are very well preserved under time evolution, including the critical nature of the singlet correlations, as expected from the Lieb-Robinson (LR) bound theorem. Consistently, the system (asymptotic) boundary is found to be described by the same Conformal Field Theory of central charge $c = 1$ during time evolution. We also compute the time-evolution of the short distance spin-spin correlations and estimate the LR velocity.

• Eikonal Dressed Gluon Exponentiation to study power corrections to Thrust, C-parameter, and Angularity

  Neelima Agarwal, Ayan Mukhopadhyay, Sourav Pal, Anurag Tripathi

  SciPost Phys. Proc. 7, 020 (2022) · published 21 June 2022 | Toggle abstract · pdf

  Dressed Gluon Exponentiation is a well known method to study power corrections. We present here its eikonalized version -- Eikonal Dressed Gluon Exponentiation (EDGE) \cite{Agarwal:2020uxi} to determine the dominant power corrections to shape variables such as Thrust, $ C $- parameter, and Angularity. Our method remarkably simplifies the calculations.