[Paper Review] Black Holes at the LHC can Determine the Spin of Higgs Bosons

Yosuke Uehara|ArXiv.org|May 13, 2002

Black Holes and Theoretical Physics19 references3 citations

TL;DR

This paper proposes a novel method to determine the spin of the Higgs boson at the LHC by analyzing the decay products of black holes produced in high-energy collisions. The method exploits the fact that spin-0 Higgs bosons have one degree of freedom, while spin-1 Higgs bosons have three, leading to a threefold increase in decay probability; with just 2.4 fb⁻¹ of luminosity, a 5σ significance can distinguish spin-0 from spin-1 Higgs bosons, enabling a one-month discovery.

ABSTRACT

We propose a new method to determine the spin of Higgs bosons at the LHC by using the decay products of black holes. Black holes may be produced if TeV-scale gravity theories are correct, and black holes decay into several particles. This decay results in the emission of high energy particles, including Higgs bosons. The difference of the degree of freedom between spin 0 and spin 1 Higgs bosons leads to a difference of the number of reconstructed Higgs bosons. From this fact, we can determine the spin of Higgs bosons with $5 σ$ significance by using the integrated luminosity L = 2.4 fb^-1, which can be accumulated in only one month operation.

Motivation & Objective

• To address the challenge of determining the spin of the Higgs boson at the LHC, where traditional angular distribution methods face high backgrounds and low statistics.
• To propose a new, background-free method for spin determination that does not rely on angular correlations.
• To leverage the decay of trans-Planckian black holes at the LHC to probe the spin quantum number of the Higgs boson.
• To demonstrate that the difference in degrees of freedom between spin-0 and spin-1 Higgs bosons leads to a measurable difference in event rates.

Proposed method

• The method relies on the production of non-rotating Schwarzschild black holes at the LHC via TeV-scale gravity models with 6 or 7 extra dimensions.
• Black holes decay via Hawking radiation, and the decay rate into a given particle depends on its degrees of freedom: 1 for spin-0 Higgs bosons, 3 for spin-1 Higgs bosons.
• A high-energy trigger is applied to detect events with one reconstructed Higgs boson and three high-energy particles (jets, leptons, photons), excluding top quarks, W/Z, tau, neutrinos, and gravitons.
• The probability of detecting such events is calculated as P ≈ 5.1×10⁻⁴, yielding ~51,000 candidate events from 10⁸ produced black holes.
• Reconstruction efficiency is estimated at 92% for Higgs boson decays into b-quarks, WW, gg, and ττ, assuming prior discovery of the Higgs boson.
• The method compares expected Higgs boson counts under spin-0 vs. spin-1 hypotheses, using the difference in decay probabilities to test the spin hypothesis.

Experimental results

Research questions

• RQ1 Can the spin of the Higgs boson be determined independently of angular distribution measurements at the LHC?
• RQ2 Does the decay of black holes into Higgs bosons exhibit a measurable difference in event yield between spin-0 and spin-1 Higgs bosons?
• RQ3 Can a 5σ significance for the spin-0 hypothesis be achieved with a low integrated luminosity using black hole decay events?
• RQ4 Is the method robust against background contamination due to the stringent trigger and reconstruction conditions?
• RQ5 What luminosity is required to distinguish spin-0 from spin-1 Higgs bosons with high statistical significance?

Key findings

• With an integrated luminosity of 2.4 fb⁻¹, the hypothesis that Higgs bosons have spin-1 can be rejected with a significance of 210σ if they are actually spin-0.
• The method requires only one month of operation at the LHC's low-luminosity design rate (10³³ cm⁻²s⁻¹), corresponding to 10⁻⁶ fb⁻¹s⁻¹.
• The number of reconstructed Higgs bosons is expected to be 47,000 under the spin-0 hypothesis and 92,000 under the spin-1 hypothesis, due to the threefold increase in degrees of freedom.
• The trigger conditions are highly selective, reducing background to nearly zero by excluding particles that decay before detection or escape undetected.
• The method is background-free for the specified decay channels, as the trigger selects only high-energy, stable, detectable particles.
• The result is robust under the assumption of a 120 GeV Higgs boson mass and a fundamental scale of 1 TeV in 6 or 7 extra dimensions.