arXiv subjects

Jakob Müller

Publications and source records attributed to Jakob Müller.

4 recordsLinked to original sources

arXiv2026

Three-loop QCD corrections to heavy-to-light form factors and applications to inclusive $B$ decays

We report on the calculation of heavy-to-light form factors at $\mathcal{O}(α_s^3)$ and on selected phenomenological applications in inclusive $B$-decays. After outlining the loop calculation, we extract the hard function in $\bar B \to X_s γ$, and discuss our recent progress and preliminary results for the N$^3$LO corrections to partial decay rates in $\bar B \to X_u l \bar ν_l$, important for the inclusive determination of $|V_{ub}|$. In particular, we establish relations for heavy-quark parameters in the shape-function scheme to four loops and improve a particular model of the $B$ meson shape-function.

hep-ph↗

arXiv2025

Subatomic Heroes

Sharing the amazing achievements of the (particle) physics world with the general public is at the heart of the mission of the Subatomic Heroes, based at the University of Siegen, Germany. Originally this started out as an endeavor of theoretical particle physics, now we are steadily spreading out to cover and include more branches of physics and science. Our activities range from merging art with public physics lectures via marvelous artistic performances at the local theater, over dedicated events for high-school students, to our Subatomic Heroes channel on Instagram and TikTok where you may also find out when and where our famous "hadronic ice-cream" will be served next! So follow us on https://www.instagram.com/subatomic_heroes and https://www.tiktok.com/@subatomic_heroes.

physics.ed-ph↗

arXiv2024

Heavy-to-light form factors to three loops

We compute three-loop corrections of $\mathcal{O}(α_{s}^3)$ to form factors with one massive and one massless quark coupling to an external vector, axialvector, scalar, pseudoscalar, or tensor current. We obtain analytic results for the color-planar contributions, for the contributions of light-quark loops, and the contributions with two heavy-quark loops. For the computation of the remaining master integrals we use the "expand and match" approach which leads to semi-analytic results for the form factors. We implement our results in a {\tt Mathematica} and a {\tt Fortran} code which allows for fast and precise numerical evaluations in the physically relevant phase space. The form factors are used to compute the hard matching coefficients in Soft-Collinear Effective Theory for all currents. The tensor coefficients at light-like momentum transfer are used to extract the hard function in $\bar B \to X_s γ$ to three loops.

hep-ph↗

arXiv2022

Taming New Physics in $b \to c \bar u d (s) $ with $τ(B^+)/τ(B_d)$ and $a_{sl}^d$

Inspired by the recently observed tensions between the experimental data and the theoretical predictions, based on QCD factorisation, for several colour-allowed non-leptonic $B$-meson decays, we study the potential size of new physics (NP) effects in the decay channels $b \to c \bar{u} d(s)$. Starting from the most general effective Hamiltonian describing the $b \to c \bar{u} d(s)$ transitions, we compute NP contributions to the theoretical predictions of $B$-meson lifetime and of $B$-mixing observables. The well-known lifetime ratio $τ(B^+)/τ(B_d)$ and the experimental bound on the semi-leptonic CP asymmetry $a_{sl}^d$, provide strong, complementary constraints on some of the NP Wilson coefficients.

hep-ph↗