Publications

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• A differential-geometry approach to operator mixing in massless QCD-like theories and Poincaré-Dulac theorem

  Matteo Becchetti

  SciPost Phys. Proc. 7, 032 (2022) · published 21 June 2022 | Toggle abstract · pdf

  We review recent progress on operator mixing in the light of the theory of canonical forms for linear systems of differential equations and, in particular, of the Poincar\'e-Dulac theorem. We show that the matrix $A(g) = -\frac{\gamma(g)}{\beta(g)} =\frac{\gamma_0}{\beta_0}\frac{1}{g} + \cdots $ determines which different cases of operator mixing can occur, and we review their classification. We derive a sufficient condition for $A(g)$ to be set in the one-loop exact form $A(g) = \frac{\gamma_0}{\beta_0}\frac{1}{g}$. Finally, we discuss the consequences of the unitarity requirement in massless QCD-like theories, and we demonstrate that $\gamma_0$ is always diagonalizable if the theory is conformal invariant and unitary in its free limit at $g =0$.

• 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.

• Backward-Angle (u-Channel) Meson Production from JLab 12~GeV Hall C to EIC

  Wenliang B. Li

  SciPost Phys. Proc. 8, 036 (2022) · published 12 July 2022 | Toggle abstract · pdf

  The recent exclusive backward-angle electroproduction of omega from Jefferson Lab Hall C electron-proton fixed-target scattering experiments above the resonance region hints at a new domain of applicability of QCD factorization in a unique u-channel kinematics regime. Thanks to this effort, the interest in studying nucleon structure through u-channel meson production observables has grown significantly. In the fixed target configuration, theu-channel meson electroproduction observables feature a unique interaction picture: the target proton absorbs nearly all momentum induced by virtual photons and recoils forward, while the produced mesons (such as omega or pions) are left behind almost at rest near the target station. In this presentation, We provide a summary of the key observations of the existing u-channel meson production results, update-to-date theory insights, and a path to further exploration from JLab 12 GeV Hall C program to the future Electron-Ion Colliders

• Dynamical spin-orbit-based spin transistor

  Fahriye N. Gürsoy, P. Reck, C. Gorini, K. Richter, I. Adagideli

  SciPost Phys. 14, 060 (2023) · published 4 April 2023 | Toggle abstract · pdf

  Spin-orbit interaction (SOI) has been a key tool to steer and manipulate spin-dependent transport properties in two-dimensional electron gases. Here we demonstrate how spin currents can be created and efficiently read out in nano- or mesoscale conductors with time-dependent and spatially inhomogeneous Rashba SOI. Invoking an underlying non-Abelian SU(2) gauge structure we show how time-periodic spin-orbit fields give rise to spin electric forces and enable the generation of pure spin currents of the order of several hundred nano-Amperes. In a complementary way, by combining gauge transformations with "hidden" Onsager relations, we exploit spatially inhomogeneous Rashba SOI to convert spin currents (back) into charge currents. In combining both concepts, we devise a spin transistor that integrates efficient spin current generation, by employing dynamical SOI, with its experimentally feasible detection via conversion into charge signals. We derive general expressions for the respective spin- and charge conductance, covering large parameter regimes of SOI strength and driving frequencies, far beyond usual adiabatic approaches such as the frozen scattering matrix approximation. We check our analytical expressions and approximations with full numerical spin-dependent transport simulations and demonstrate that the predictions hold true in a wide range from low to high driving frequencies.

• Tchavdar Dimitrov Palev - In memoriam

  N. I. Stoilova

  SciPost Phys. Proc. 14, 011 (2023) · published 23 November 2023 | Toggle abstract · pdf

  Tchavdar Dimitrov Palev – In memoriam

• Searches for new physics that couple with third generation fermions

  Valeria D'Amante, on behalf of the CMS collaboration

  SciPost Phys. Proc. 17, 015 (2025) · published 23 July 2025 | Toggle abstract · pdf

  The $\tau$ lepton, with a mass of $1776.86 ± 0.12$ MeV, is unique in its ability to decay into hadrons and a neutrino. Approximately one-third of $\tau$ decays produce an electron or a muon and two neutrinos, denoted as $\tau_e$ and $\tau_\mu$. The remaining decays, mainly involving hadrons and a tau neutrino, are denoted as $\tau_h$. At the CERN LHC, searches involving $\tau$ leptons are crucial for studying the decay of Higgs bosons to $\tau$ pairs, probing Yukawa couplings, and CP properties of the Higgs. These measurements support Standard Model (SM) tests and searches for Beyond Standard Model (BSM) physics, including new or heavy Higgs bosons, leptoquarks, supersymmetric particles, or gauge bosons. The $\tau$ lepton polarization in Z boson decays is also significant for probing the SM. Despite its potential as a portal to new physics, the $\tau$ lepton's decay products, especially neutrinos and hadrons, make its reconstruction and identification challenging at the LHC. At the CMS experiment, neutrinos contribute to Missing Transverse Energy (MET), and hadronically decaying $\tau$ leptons are often misidentified as jets, complicating the separation of $\tau$-involved processes from background processes.

• Higher-order corrections to the kinetic mass definition for the bottom and the charm quarks

  Matteo Fael

  SciPost Phys. Proc. 7, 026 (2022) · published 21 June 2022 | Toggle abstract · pdf

  In these proceedings we discuss the relation between the kinetic and the on-shell schemes for the bottom and the charm quarks and present the methods for the calculation of the mass relation to higher orders in perturbative QCD. The bottom mass in the kinetic scheme is a pivotal input parameter in the inclusive determination of $|V_{cb}|$ from $B\to X_c \ell \nu_\ell$ decays. By combining the relation between the kinetic and the on-shell mass with well-know results for the $\overline{\mathrm{MS}}$-on-shell conversion, we obtain a prediction for $m_b^\mathrm{kin}$ based on precise determinations of $\overline{m}_b(\overline{m}_b)$.

• 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 $\Delta \Gamma_s$.

• Generalized lattices, conformal manifolds, and symmetries

  Shlomo S. Razamat, Michal Shemesh, Aelly Zeltzer

  SciPost Phys. 19, 069 (2025) · published 24 September 2025 | Toggle abstract · pdf

  We consider supersymmetric conformal quantum field theories (SCFTs) with degrees of freedom labeled by lattice data. We will assume that in terms of the corresponding lattice the interactions are nearest neighbor and exactly marginal. For example, one can construct such theories by coupling many copies of a single SCFT with exactly marginal deformations. In particular, we discuss the interplay between conformal manifolds of such theories and their global, on-site and lattice, symmetries. We show that one can interpret certain current non-conservation equations for symmetries broken by the interactions as conservation equations including the lattice directions. Moreover, we discuss a class of exactly marginal deformations which are labeled by lattice holonomies that are topological on the lattice. We discuss concrete examples of such constructions and comment on their relevance to compactifications of SCFTs.

• A novel formulation of the unintegrated gluon distribution for DIS

  Yacine Mehtar-Tani

  SciPost Phys. Proc. 8, 037 (2022) · published 12 July 2022 | Toggle abstract · pdf

  In this talk, we revisit inclusive DIS in the small $x$ limit and derive a new factorization formula that accounts for leading powers in both Bjorken and Regge limits. In this semi-classical description, we obtain a new unintegrated gluon distribution which encompasses both the dipole operator and the gluon Parton Distribution Function with an explicit dependence on the longitudinal momentum fraction $x$.