LHC search narrows hiding places for quantum black holes

Overview

Updated Sep 23

The Large Hadron Collider's most thorough search for microscopic black holes came up empty. That absence is a result: it rules out quantum black holes up to about 12 TeV (tera-electron volts) and, with them, most theories of extra spatial dimensions.

Quantum black holes would form if extra dimensions made gravity strong at tiny scales, offering a testable path to a quantum theory of gravity. Each empty search shrinks the map of where such physics can hide. The process is the same one that eventually cornered the Higgs boson.

Why it matters

The LHC made no tiny black holes, so whole families of extra-dimension and quantum gravity theories now have nowhere to hide.

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Key Indicators

8.4–11.4 TeV

Semiclassical black hole mass excluded (CMS)

95% confidence limit depending on the model and the number of extra dimensions.

9.0–10.7 TeV

String ball mass excluded (CMS)

Hypothetical string theory states excluded at 95% confidence level.

9.4 TeV

ATLAS quantum black hole limit

World-best exclusion reached in the lepton+jet channel using 13.6 TeV Run 3 data.

138 fb⁻¹

CMS dataset analyzed

Proton collision data collected at 13 TeV from 2016 to 2018, roughly 10 quadrillion events.

Voices

Curated perspectives — historical figures and your fellow readers.

People Involved

Danyi Zhang

Doctoral researcher, UC Santa Barbara

Part of the CMS search team that built the machine-learning analysis

Tamas Almos Vami

Researcher, UC Santa Barbara

Co-implemented the machine-learning framework with Zhang

Celia Lo

Doctoral student, UCLA

Led the model-independent search strategy for the CMS study

Steven Giddings

Theoretical physicist, UC Santa Barbara

His quantum black hole models helped frame the experimental search

Organizations Involved

CMS Collaboration

International particle physics experiment

Performed the primary search that excluded quantum black holes below 8.4–11.4 TeV

Operates the Compact Muon Solenoid detector at CERN's Large Hadron Collider.

ATLAS Collaboration

International particle physics experiment

Set world-best quantum black hole limit of 9.4 TeV in Run 3 data

Operates a general-purpose detector at the LHC's interaction point, a counterpart to CMS.

CERN (European Organization for Nuclear Research)

International research laboratory

Operates the Large Hadron Collider where the searches took place

European Organization for Nuclear Research, home to the world's most powerful particle accelerator.

Timeline

December 2018 September 2026

6 events Latest: September 23rd, 2026 · 2 months ago

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September 2026
Teams publicize tightened limits on quantum black holes
Latest Announcement

UC Santa Barbara and CERN release summaries highlighting that quantum black holes are unlikely up to about 12 TeV.
September 23rd, 2026
August 2026
CMS results published in JHEP
Publication

The black hole, string ball, and sphaleron search appears in the Journal of High Energy Physics.
August 12th, 2026
April 2026
ATLAS posts its own quantum black hole search
Research

Using 13.6 TeV Run 3 data, ATLAS sets a world-best exclusion of 9.4 TeV in the lepton+jet channel.
April 30th, 2026
CMS paper excludes quantum black holes below 8.4–11.4 TeV
Research

Analysis of 13 TeV data finds no black holes or string balls; more than two extra dimensions ruled out in many tested models at 95% confidence.
April 12th, 2026
July 2022
LHC restarts at 13.6 TeV
Milestone

Run 3 starts. The 0.6 TeV energy increase can boost quantum black hole production rates by up to an order of magnitude at high mass.
July 5th, 2022
December 2018
LHC Run 2 ends with key dataset collected
Milestone

CMS holds 138 fb⁻¹ of 13 TeV proton collisions that later anchor the quantum black hole search.
December 10th, 2018

Scenarios

Run 3 final data extends quantum black hole limits past 12 TeV

Likely Resolves by End of 2027

Discussed by: CMS and ATLAS collaborations

Both experiments collected more 13.6 TeV data than the samples analyzed so far. Final Run 3 analyses with full luminosity and refined methods could push exclusions above the current 9–12 TeV range, following the pattern of each search extending the reach of the last.

Quantum black hole signal appears in further LHC data

Unlikely Resolves by End of 2030

Discussed by: Noted in experiment papers; cross-sections rise steeply with collision energy

The jump from 13 to 13.6 TeV raised quantum black hole production cross-sections by up to an order of magnitude at the highest masses. Additional Run 3 collisions could reveal an excess just above the current exclusion edge, a possibility the current limits cannot fully close.

CERN approves Future Circular Collider, extending the quantum gravity search

Uncertain Resolves by End of 2028

Discussed by: CERN's Future Circular Collider feasibility study

A proposed 100 TeV machine would probe quantum gravity scales far beyond the LHC's reach. The null results strengthen the physics case for higher collision energy. CERN's decision on the project is expected after the feasibility study concludes.

Historical Context

3 moments from history that rhyme with this story — and how they unfolded.

July 2012

Higgs boson discovery (2012)

Theorized in 1964, the Higgs boson took four decades to find. Experiments at CERN's LEP accelerator and Fermilab's Tevatron gradually narrowed its possible mass range before LHC collisions revealed it at 125 GeV.

Then

The discovery completed the Standard Model's particle roster and won the 2013 Nobel Prize in Physics.

Now

It cemented exclusion-driven searching as the established method for finding new physics.

Why this matters now

Zhang and colleagues cite the Higgs as the model: decades of ruling out mass ranges eventually located the particle. Today's quantum black hole exclusions work the same way.

December 2015 – August 2016

750 GeV diphoton excess (2015–2016)

Early LHC Run 2 data showed a possible new particle decaying into two photons at 750 GeV. Physicists published hundreds of theory papers within months.

Then

More data in 2016 showed the bump was a statistical fluctuation that evaporated.

Now

A reminder that single hints can fade with statistics, and that null searches carry real constraints.

Why this matters now

It shows why the CMS search relies on large datasets and machine learning to distinguish genuine signals from background fluctuations.

2011–present

Supersymmetry searches at the LHC (2011–present)

Supersymmetry predicted a partner particle for every known particle, long expected to appear at LHC energies. A decade of collisions has found no trace.

Then

Mass limits for gluinos and squarks climbed above 1–2 TeV, ruling out the simplest models.

Now

The theory community adapted, moving toward more complex or non-minimal variants.

Why this matters now

The quantum black hole search follows the same arc: a motivated theory facing progressively tighter exclusions and refining its parameter space in response.