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← Particles, nuclei and gravitation this week · 9 November 2026 · 4 min read

Particles, nuclei and gravitation this week: rare decays and the shape of the unseen

From elusive particle decays to tractable models of quantum gravity, this week’s selection shows how precision measurements and carefully constrained calculations make hidden physics accessible.

How to check the findings and keep reading? Illustrated guide

How these papers were chosen among the week's 568 papers

All 568 papers of the week whose main category is in this field were read, title and start of the abstract, and 26 were kept. They were then ordered by what can be counted: how many research profiles of our readers they come close to, whether a rising topic of the field includes them, and how many categories they were posted in. The abstracts of the first 26 were read in full to choose these, no more than two from one category and one per team.

The 1 number of the text was checked against the abstracts. 24 statements on what the papers found were looked for word for word in their abstracts.

Sources: arXiv.

A rare decay comes into view #

LHCb reports the first evidence from a single experiment for a neutral B meson decaying into a muon and its antiparticle. The same analysis delivers the most precise measurements yet of the corresponding strange B meson’s decay probability and effective lifetime. It uses proton collisions recorded with the upgraded detector; combining these results with earlier LHCb measurements sharpens the precision further.

Such rare processes are useful places to look for particles that cannot be produced directly but could alter decay rates through quantum effects. Here, all the measurements agree with Standard Model expectations. The advance is therefore not a discrepancy but a more sensitive test of where new physics might hide.

Who works on it? Literature review Follow this subject

A charm quark keeps its quiet cone #

A massive quark is expected to suppress radiation close to its direction of motion, leaving a relatively quiet angular region called the dead cone. CMS now reports the first experimental study of this effect for charm quarks in heavy-ion collisions. The researchers selected hard, nearly collinear emissions inside jets and compared jets containing prompt neutral D mesons with an inclusive jet sample.

In lead–lead collisions, the selected emissions occur at larger angles in the D-meson jets, consistent with the suppression expected from the dead cone and with a similar finding in proton–proton collisions. The result disfavors models in which radiation generated by the surrounding medium fills that cone. It helps distinguish which features of a quark’s radiation pattern survive passage through hot nuclear matter.

Who works on it? Literature review Follow this subject

Revisiting a key ingredient of the muon’s magnetism #

A new BaBar analysis measures how often electron–positron collisions produce charged pion pairs, a process needed to calculate the influence of hadronic vacuum polarization on the muon’s magnetic anomaly. Rather than determining the collision rate in isolation, the team uses the ratio of pion-pair to muon-pair production, reducing uncertainties shared by the measurements. Unlike the earlier BaBar analysis, it separates pion and muon contributions statistically through their angular distributions.

The preprint compares the new result with the earlier BaBar measurement while accounting for their correlated uncertainties, and also compares it with other pion-pair measurements. This matters beyond the details of collider analysis: interpreting precision tests of the muon requires a reliable accounting of ordinary strong-interaction effects before any residual can be attributed to unfamiliar physics.

Who works on it? Literature review Follow this subject

Mapping spin in swirling nuclear matter #

Measurements from the RHIC Beam Energy Scan show how the global spin alignment of hyperons changes with collision energy, particle species and rapidity, a measure related to motion along the beam. The analysis finds evidence that Lambda polarization grows with the magnitude of rapidity, and observes global polarization of Xi hyperons at these energies for the first time.

No significant polarization difference appears between Lambda particles and their antiparticles, tightening constraints on contributions from magnetic fields. Omega measurements are compatible with a similar energy dependence, though their interpretation favors a particular decay parameter only under the assumed global-polarization picture. Together, these results give researchers a more detailed way to connect particle spin with the collective motion of strongly interacting matter.

Who works on it? Literature review Follow this subject

Making a chiral gauge theory computable #

Chiral gauge theories, in which opposite-handed particles interact differently, underpin the Standard Model but are notoriously difficult to simulate nonperturbatively. A new preprint constructs a gauge-invariant lattice formulation for abelian chiral theories in a reduced-dimensional setting, using finite-state quantum units called qudits. The construction preserves the relevant chiral symmetry and its anomaly in a discrete form, while anomaly cancellation allows the gauge constraints to be solved exactly.

The authors then use infinite matrix product states to simulate a canonical example, finding excellent agreement with analytic predictions for its low-energy behavior. The attraction extends to quantum computing: a finite local state space and explicitly solved constraints offer a practical route to calculations on both classical and quantum machines. This is not yet a simulation of the Standard Model, but it tackles a structural obstacle shared by much more ambitious theories.

Who works on it? Literature review Follow this subject

A tightly bounded foothold in matrix quantum gravity #

The BFSS matrix model offers a setting for studying connections between quantum mechanics and gravity. A new calculation constructs an extraordinarily accurate approximation to its ground state for the SU(2) case. The key is an auxiliary operator that matches the Hamiltonian on ground states but has a spectral gap, together with representation theory that drastically reduces the calculation’s size.

The authors compute the variational basis’s inner products exactly and establish rigorous bounds on both energy and overlap with the ground-state subspace. Their state also reproduces the predicted large-distance behavior of the radial probability distribution, including its coefficient, from a three-graviton amplitude. That agreement makes this more than a numerical approximation: it connects a controlled quantum-mechanical calculation with a specific gravitational prediction.

Who works on it? Literature review Follow this subject

These preprints share a concern with making indirect evidence trustworthy. Rare decays and pion production refine tests of unseen quantum effects; jet radiation and hyperon spins expose properties of nuclear matter through its debris; lattice constructions and matrix calculations make difficult theories answerable to controlled computation. The common progress lies in narrowing the distance between an underlying mechanism and something that can actually be measured or bounded.

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Written by AI from the 705 papers of the week in this field. Most are preprints, not yet peer reviewed: the text says what their authors report.

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