Stefan Meinel

Sunrise over the Sonoran Desert, with Cholla cacti in the foreground, glowing backlit

Sunrise over the Sonoran Desert, with a hiking trail and Saguaro cacti in the foreground

The Tucson mountains in the orange morning sunlight, with brushes and Saguaro cacti in the foreground

Hiking trail in early morning light, with a large three-armed Saguaro on the right, and a hill and blue sky in the background

Tucson Mountain Park in the Sonoran Desert this morning

12.10.2025 15:29 — 👍 1    🔁 0    💬 0    📌 0

Full moon setting over the Tucson Mountains, with desert in the foreground. The Marriott Starr Pass hotel is seen nestled in the hills.

Sunrise over the Rincon Mountains, with Saguaro cacti in the foreground. A yellow glow in the valley of Tucson.

Good morning from Tucson, Arizona!

07.10.2025 14:08 — 👍 1    🔁 0    💬 0    📌 0

The workshop poster with pictures of Fermilab and Chicago at night.

The LHC Physics Center at Fermilab is hosting a workshop on "Violation of Fundamental Symmetries with B mesons" on December 15-19 (indico.fnal.gov/event/71119/). The workshop is dedicated to the memory of Professors Sheldon Stone and Ian Shipsey, who made significant contributions to B physics.

23.09.2025 20:05 — 👍 1    🔁 0    💬 0    📌 0

A plot from https://arxiv.org/abs/1912.05811 showing the Λb→Λμ+μ− differential branching fraction at high q^2. The LHCb measurement from https://arxiv.org/abs/1503.07138 is seen above the SM prediction, while our estimated correction of the LHCb measurement is seen close to the SM prediction.

We had already pointed out in arxiv.org/abs/1912.05811 that the old estimate was incorrect, and had estimated B(Λb→J/ψΛ)=(3.7 ± 1.0) × 10−4, leading to the plot of the Λb→Λμ+μ− differential branching fraction shown below.

17.09.2025 09:20 — 👍 0    🔁 0    💬 0    📌 0

Updating the normalization to their new result substantially lowers the Λb→Λμ+μ− differential branching fraction, making the picture more consistent with the b→sl+l- anomalies in meson decays.

17.09.2025 09:20 — 👍 1    🔁 0    💬 1    📌 0

An exciting new result from LHCb! The decay Λb→J/ψΛ was used as a normalization mode for Λb→Λμ+μ− in arxiv.org/abs/1503.07138, where the estimate B(Λb→J/ψΛ)=(6.3 ± 1.3) × 10−4 was used.

17.09.2025 09:20 — 👍 0    🔁 0    💬 1    📌 0

A large discrepancy between theory and experiment for the decay rate of Xi_c^0 (down-strange-charm) baryons to Xi^- (down-strange-strange) baryons and leptons: arxiv.org/abs/2504.07302 . The problem may be with the measurement of the nonleptonic normalization decay mode.

11.04.2025 13:45 — 👍 1    🔁 0    💬 0    📌 0