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1. Two-loop electron factor contribution to lamb shift in muonium and positronium

   https://doi.org/10.1016/j.physletb.2023.138087  

   Eides, Michael I; Shelyuto, Valery A (September 2023, Physics Letters B)

   Grinstein, B (Ed.)

   We calculate hard spin-independent contributions to energy levels in muonium and positronium which are due to radiatively corrected electron factor insertion in two-photon exchange diagrams. Calculation of these corrections is motivated by the new round of precise measurements of spin-independent transition frequencies in muonium and positronium. 

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2. Top-induced contributions to H → $$ b\overline{b} $$ and H → $$ c\overline{c} $$ at $$ \mathcal{O}\left({\alpha}_s^3\right) $$

   https://doi.org/10.1007/JHEP12(2020)058  

   Mondini, Roberto; Schubert, Ulrich; Williams, Ciaran (December 2020, Journal of High Energy Physics)

   null (Ed.)

   A bstract In this paper we present a fully-differential calculation for the contributions to the partial widths H → $$ b\overline{b} $$ b b ¯ and H → $$ c\overline{c} $$ c c ¯ that are sensitive to the top quark Yukawa coupling y t to order $$ {\alpha}_s^3 $$ α s 3 . These contributions first enter at order $$ {\alpha}_s^2 $$ α s 2 through terms proportional to y t y q ( q = b, c ). At order $$ {\alpha}_s^3 $$ α s 3 corrections to the mixed terms are present as well as a new contribution proportional to $$ {y}_t^2 $$ y t 2 . Our results retain the mass of the final-state quarks throughout, while the top quark is integrated out resulting in an effective field theory (EFT). Our results are implemented into a Monte Carlo code allowing for the application of arbitrary final-state selection cuts. As an example we present differential distributions for observables in the Higgs boson rest frame using the Durham jet clustering algorithm. We find that the total impact of the top-induced (i.e. EFT) pieces is sensitive to the nature of the final-state cuts, particularly b -tagging and c -tagging requirements. For bottom quarks, the EFT pieces contribute to the total width (and differential distributions) at around the percent level. The impact is much bigger for the H → $$ c\overline{c} $$ c c ¯ channel, with effects as large as 15%. We show however that their impact can be significantly reduced by the application of jet-tagging selection cuts. 

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3. High energy resummed predictions for the production of a Higgs boson with at least one jet

   https://doi.org/10.1007/JHEP03(2023)001  

   Andersen, Jeppe R.; Hassan, Hitham; Maier, Andreas; Paltrinieri, Jérémy; Papaefstathiou, Andreas; Smillie, Jennifer M. (March 2023, Journal of High Energy Physics)

   A bstract We present all-order predictions for Higgs boson production plus at least one jet which are accurate to leading logarithm in $$ \hat{s}/{\left|{p}_{\perp}\right|}^2 $$ s ̂ / p ⊥ 2 . Our calculation includes full top and bottom quark mass dependence at all orders in the logarithmic part, and to highest available order in the tree-level matching. The calculation is implemented in the framework of High Energy Jets (HEJ). This is the first cross section calculated with log( $$ \hat{s} $$ s ̂ ) resummation and matched to fixed order for a process requiring just one jet, and our results also extend the region of resummation for processes with two jets or more. This is possible because the resummation is performed explicitly in phase space. We compare the results of our new calculation to LHC data and to next-to-leading order predictions and find a numerically significant impact of the logarithmic corrections in the shape of key distributions, which remains after normalisation of the cross section. 

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4. Heavy quark jet production near threshold

   https://doi.org/10.1007/JHEP09(2021)148  

   Dai, Lin; Kim, Chul; Leibovich, Adam K (January 2021, JHEP reports)

   In this paper, we study the fragmentation of a heavy quark into a jet near threshold, meaning that final state jet carries most of the energy of the fragmenting heavy quark. Using the heavy quark fragmentation function, we simultaneously resum large logarithms of the jet radius R and 1 − z, where z is the ratio of the jet energy to the initiating heavy quark energy. There are numerically significant corrections to the leading order rate due to this resummation. We also investigate the heavy quark fragmentation to a groomed jet, using the soft drop grooming algorithm as an example. In order to do so, we introduce a collinear-ultrasoft mode sensitive to the grooming region determined by the algorithm’s zcut parameter. This allows us to resum large logarithms of zcut/(1−z), again leading to large numerical corrections near the endpoint. A nice feature of the analysis of the heavy quark fragmenting to a groomed jet is the heavy quark mass m renders the algorithm infrared finite, allowing a perturbative calculation. We analyze this for EJ R ∼ m and EJ R ≫ m, where EJ is the jet energy. To do the latter case, we introduce an ultracollinear-soft mode, allowing us to resum large logarithms of EJ R/m. Finally, as an application we calculate the rate for e+e− collisions to produce a heavy quark jet in the endpoint region, where we show that grooming effects have a sizable contribution near the endpoint. 

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5. N3LO soft-gluon corrections in single-particle-inclusive kinematics and H+H− production

   https://doi.org/10.1007/JHEP06(2024)138  

   Kidonakis, Nikolaos; Tonero, Alberto (June 2024, Journal of High Energy Physics)

   A<sc>bstract</sc> We calculate the complete soft-gluon corrections for the production of colorless final states through N³LO in single-particle-inclusive kinematics. We present explicit analytical results and use them to study higher-order QCD corrections for the production of a heavy charged Higgs pair (H⁺H⁻) via quark-antiquark annihilation in the Two-Higgs-Doublet Model at LHC energies. We calculate the NNLO soft-gluon and virtual QCD corrections as well as the N³LO soft-gluon corrections to the total cross section and the charged-Higgs rapidity distribution. This is the first calculation of complete N³LO soft-gluon corrections for a process in single-particle-inclusive kinematics, and the results can be applied to other processes with colorless final states. 

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