Unidentified falling objects in the LHC as dark matter signals

This paper proposes that a small fraction of the Large Hadron Collider's unidentified falling objects (UFOs) may be caused by antimatter axion quark nuggets (a macroscopic dark matter candidate) generating acoustic waves, suggesting the LHC could function as a broadband detector to confirm this signal through correlated event analysis.

The Gist

Imagine the Large Hadron Collider (LHC) as the world's most sensitive, high-speed race track for protons. It's a 27-kilometer loop buried deep underground, where particles zoom around at nearly the speed of light.

For years, physicists have been puzzled by a glitch in this race track called "Unidentified Falling Objects" (UFOs).

The Mystery: The "Dust Bunny" Problem

Usually, when these UFOs happen, it looks like a tiny speck of dust (a "dust bunny") falls off the wall of the tunnel, gets sucked into the proton beam, and causes a massive crash. The beam loses energy, and the machine has to stop.

Physicists know the dust exists, but they don't know how it gets released. It's like seeing a chandelier suddenly fall in a room with no wind and no one touching it. What triggered the fall?

The New Theory: Dark Matter as a "Ghost Hammer"

This paper proposes a wild new idea: Maybe the dust isn't falling because of a glitch in the machine, but because of a Dark Matter hammer hitting the wall from miles away.

The authors suggest that a specific type of dark matter, called an Axion Quark Nugget (AQN), might be the culprit.

Here is the analogy to make it simple:

• The AQN: Imagine a tiny, incredibly dense marble made of "anti-matter" (the opposite of normal matter). It's heavy (like a small rock) but tiny (the size of a grain of sand). It travels through the Earth like a ghost, mostly ignoring everything.
• The Interaction: When this "ghost marble" passes through the Earth (within about 100 km of the LHC), it smashes into the rock and air. Because it's made of anti-matter, it annihilates with the normal matter it hits, releasing a massive burst of energy.
• The Shockwave: This explosion creates a powerful acoustic shockwave (a sound wave), similar to a sonic boom from a jet, but traveling through the ground.

The Domino Effect

Here is how the paper connects the dots:

1. The Hammer Strike: An AQN passes underground near the LHC.
2. The Vibration: The resulting shockwave travels through the ground and hits the LHC tunnel. It's like a giant, invisible hammer tapping the side of the tunnel.
3. The Dust Falls: This vibration is strong enough to shake loose those mysterious dust particles sitting on the beam screen.
4. The Crash: The dust falls into the beam, causing the "UFO" event that the detectors see.

Why This is a Big Deal

If this is true, the LHC isn't just a particle accelerator; it's accidentally acting as a giant, underground microphone for Dark Matter.

• The "Fingerprint": Normal dust falls randomly. But if a Dark Matter hammer hits the ground, it creates a ripple effect. It would shake the tunnel in multiple places at once.
• The Signal: If the detectors see three or four UFOs happen within a split second (milliseconds to a few seconds) at different spots around the 27km ring, that's the "smoking gun." It means a single shockwave traveled through the whole ring, knocking dust loose everywhere.

The Bottom Line

The authors are saying: "We think about 1% to 10% of these annoying UFO glitches are actually us detecting Dark Matter."

They propose that by looking for these synchronized bursts of UFOs and checking if they match up with seismic sensors (earthquake detectors) and infrasound microphones, we can prove that Dark Matter exists and that it's made of these heavy, macroscopic nuggets.

In short: The LHC might be the world's first "Dark Matter seismograph," listening for the footsteps of invisible rocks passing through the Earth, causing the dust to dance and fall.

Technical Summary

1. Problem Statement

Since 2010, the Large Hadron Collider (LHC) has experienced sporadic beam loss events known as Unidentified Falling Objects (UFOs). These events manifest as sharp spikes in beam loss (up to $10^8$ protons) occurring within milliseconds.

• Current Understanding: The prevailing hypothesis attributes UFOs to micrometer-sized dust particles released from the beam screen, which interact inelastically with the proton beam.
• The Gap: While the formation and charging of dust are understood, the release mechanism remains an open question. Known triggers (e.g., vibrations from injection kicker magnets or gravity for top-mounted particles) cannot explain all observed events, particularly the rare "burst sequences" where multiple independent UFOs occur simultaneously at widely separated locations around the 27-km ring.
• Objective: The authors propose that a small subset of these UFOs (specifically correlated bursts) may be triggered not by local mechanical failures, but by macroscopic Dark Matter (DM) candidates known as Axion Quark Nuggets (AQNs) passing underground near the LHC.

2. Methodology and Theoretical Framework

A. The Axion Quark Nugget (AQN) Model

The paper utilizes the AQN model, a macroscopic DM candidate formed during the QCD phase transition in the early Universe.

• Composition: AQNs are nuclear-density composite objects containing both matter and antimatter.
• Cosmological Significance: The model naturally explains the similarity in abundance between dark matter and visible matter ($\Omega_{DM} \sim \Omega_{visible}$) and the baryon asymmetry of the Universe via asymmetric charge separation.
• Interaction: While AQNs are "dark" in the dilute cosmological environment, they interact strongly with ordinary matter upon entering the Earth. An antimatter AQN annihilates with surrounding matter, releasing significant energy.
• Benchmark Mass: The authors adopt a benchmark average mass of $\langle M_{AQN} \rangle \approx 100$ g, consistent with astrophysical observations (e.g., solar corona heating, galactic UV background).

B. The Proposed Mechanism: Acoustic Shock Waves

The core hypothesis is that an antimatter AQN passing within $\sim 100$ km of the LHC generates a powerful acoustic shock wave as it travels underground.

1. Energy Release: As the AQN moves through rock ($n_{rock} \sim 10^{24} \text{ cm}^{-3}$), it heats up to $\sim 100$ keV, annihilating surrounding matter.
2. Shock Wave Generation: This annihilation creates a supersonic shock wave propagating through the Earth's crust.
3. Dust Release: When this acoustic wave reaches the LHC tunnel, it exerts an instantaneous mechanical impulse (overpressure) on dust particles settled at the bottom of the beam screen.
4. Triggering UFOs: If the impulse exceeds the critical adhesive force ($F_{rel, crit} \sim 10^{-8}$ N for $10 \mu$m dust), the particle is dislodged, attracted to the beam, and triggers a UFO event.

C. Detection Strategy

Unlike conventional UFOs which are localized, an AQN-induced event would trigger a "UFO Burst":

• Correlation: Multiple UFOs occurring within a short time window (milliseconds to seconds) but at different locations along the LHC ring.
• Timing: The time delay ($\Delta t$) between events depends on the acoustic wave velocity ($c_s \approx 4$ km/s) and the distance between detectors.
• Multi-messenger Approach: The signal should correlate with seismic data (CERN Seismic Network) and infrasound detectors, distinguishing it from local mechanical noise.

3. Key Contributions and Calculations

A. Force and Energy Estimates

The authors derived the overpressure $P(r)$ and frequency $\nu(r)$ of the shock wave at distance $r$ from the AQN:

• Overpressure: $P(r) \sim 3.6 \times 10^2 \text{ Pa} \left(\frac{100 \text{ km}}{r}\right)^{3/4} \left(\frac{\langle M_{AQN} \rangle}{100 \text{ g}}\right)^{2/3}$.
• Frequency: $\nu(r) \sim 3.5 \text{ kHz}$.
• Result: At $r \sim 100$ km, the acoustic wave imparts a vibration velocity of $\Delta v \approx 0.85$ m/s to a $10 \mu$m dust particle. This exceeds the critical release velocity ($v_{crit} \approx 0.5$ m/s) required to overcome adhesion forces, validating the mechanism.

B. Event Rate Estimation

Using the AQN flux formula and the effective detection radius ($r_{max} \approx 67$ km for a burst trigger):

• Predicted Rate: The estimated rate of AQN-induced UFO bursts is approximately 0.045 events per hour.
• Fraction of Total UFOs: Given the total UFO rate is $<10$ events/hour, AQN-induced events would constitute roughly 1–10% of all observed UFOs.

C. Signal-to-Noise Ratio (SNR) Analysis

The authors calculated the SNR for detecting correlated bursts against the background of random, uncorrelated UFOs (Poisson distribution).

• Criteria: Detection of $n$ correlated UFOs within a 2-second window.
• Results (for 360 hours of observation):
  • 2 correlated events: SNR $> 10$ for AQN masses $\ge 50$ g.
  • 3 correlated events: SNR $> 5$ across the entire allowed mass range ($5$ g to $1000$ g).
• Conclusion: A 3-event correlation provides a statistically robust signal distinguishable from background noise.

4. Results

• Feasibility: The LHC acts as a massive, broadband acoustic detector. The proposed mechanism successfully explains how a distant DM object can trigger localized beam losses.
• Distinctive Signatures: AQN-induced UFOs are unique because they appear as spatially separated, time-correlated bursts (6 ms to 2 s intervals) rather than isolated, random events.
• Validation Potential: By cross-referencing BLM (Beam Loss Monitor) data with the CERN Seismic Network and infrasound detectors, these events can be unambiguously identified.

5. Significance

• New DM Detection Paradigm: This work proposes a novel, indirect method for detecting macroscopic Dark Matter using existing particle accelerator infrastructure, bypassing the need for new, dedicated detectors.
• Solving the "UFO Mystery": It offers a physical explanation for the release mechanism of dust particles and the rare "burst" phenomena that current dust-release models cannot fully account for.
• Broader Implications: If validated, this would confirm the existence of macroscopic DM (AQNs) and provide a unified explanation for various unexplained terrestrial phenomena, including "skyquakes," Telescope Array bursts, and ANITA anomalous events, all attributed to AQN interactions.
• Cost-Effectiveness: It leverages the LHC's existing 4,000 Beam Loss Monitors, making it a highly efficient search strategy compared to traditional acoustic detector networks which suffer from higher atmospheric noise.

In summary, the paper argues that the LHC is uniquely positioned to detect macroscopic Dark Matter by observing correlated "UFO storms" triggered by the acoustic shock waves of passing antimatter quark nuggets, offering a potential breakthrough in both accelerator physics and cosmology.