The Higgs Boson: Inside the Decades-Long Hunt for the “God Particle”

The hunt for the Higgs boson has been one of the most intense and exciting journeys in modern physics. This elusive particle has captivated scientists for over half a century. Its eventual discovery in 2012 at the Large Hadron Collider (LHC) quickly came up as one of the greatest scientific achievements of our time.

The Higgs provided the final piece of the puzzle for the Standard Model of particle physics, revolutionizing our understanding of how particles acquire mass. The monumental effort to find this tiny particle involved an international collaboration of over 10,000 scientists and engineers, along with billions of dollars worth of cutting-edge particle detectors and accelerators. Let’s dive into the rollercoaster ride that led to unraveling the secrets of the Higgs.

The Origins of the Higgs Boson Theory

In 1964, physicists Peter Higgs, François Englert, and others published three papers that first proposed the theory of how particles acquire mass. They predicted the existence of an invisible energy field, now known as the Higgs field, which permeates the entire universe. Higgs also predicted a new particle linked with this field, which later became known as the Higgs boson. Interacting with the Higgs field is what allows fundamental particles to have mass. This was a revolutionary idea that filled in a major gap in the Standard Model, which describes the zoo of fundamental particles and forces.

But detecting the Higgs would require technology far beyond what was available in the 1960s. In 1989, scientists built the enormous 17-mile wide Large Electron-Positron (LEP) collider at CERN in Switzerland to hunt for the Higgs. Eventually, they ruled out its existence below 114 GeV. As scientists realized they would need a much more powerful collider, planning began for the LHC in 1984.

The $10 Billion LHC: A Higgs-Hunting Machine

The Large Hadron Collider took over 10,000 scientists and engineers decades to complete, making it one of the most complex scientific instruments ever constructed. Built in a 17-mile ring 100 meters underground on the border of France and Switzerland, it accelerates beams of protons to 99.9999% the speed of light and crashes them together 600 million times per second. The tremendous energies involved recreate conditions moments after the Big Bang.

When operational in 2008, the LHC took over the mantle from LEP to lead the search for the Higgs. It collided protons at record-high energies of 7 teraelectronvolts (TeV) from 2010 and 8 TeV in 2012 (the machine was designed for 14 TeV), more than 30 times the 209 GeV that LEP reached with electrons and positrons. Trillions of collisions between the speeding protons created showers of particles, generating tens of petabytes of data per year that get analyzed by a global computing grid. Within this particle spray, scientists hoped to see clues to the Higgs Boson decaying into other byproducts.

Two major LHC particle detector experiments played a key role – ATLAS (A Toroidal LHC ApparatuS) and CMS (Compact Muon Solenoid). Each housed over 3000 scientists and weighed 7000 tons (ATLAS) and 14,000 tons (CMS), making them some of the largest and heaviest scientific instruments ever built. They both independently hunted for Higgs signatures in the messy particle collision data.

Hints Emerge – The Drama Builds

By 2011, both ATLAS and CMS were seeing intriguing hints of a particle at around 125 GeV, but the evidence wasn’t yet statistically convincing enough to claim a discovery. The next year, the teams finally gathered enough collision data to confirm the existence of a new particle. After a 48-year-long search, scientists at CERN finally found the Higgs boson and made the historic announcement on July 4, 2012. ATLAS and CMS presented comprehensive evidence of a new particle consistent with a Higgs boson, and in March 2013, with more data, CERN announced that it is indeed a Higgs boson. The 5-sigma results exceeded the stringent threshold physicists require to claim a discovery. Additional studies since then have further validated the particle as matching Standard Model predictions.

The monumental finding confirmed that the Higgs mechanism for generating mass was correct, finally completing the Standard Model. Peter Higgs and François Englert were awarded the 2013 Nobel Prize in physics for their pioneering theoretical work. The discovery also provided fresh clues for exploring mysteries like dark matter and quantum gravity. The Higgs boson has been a fundamental change for particle physics, catapulting our understanding of the subatomic world to a new level. Scientists now eagerly study its properties in fine detail, as this particle’s role in our cosmic origins is profound.

How the Higgs Boson Was Detected

But how was the Higgs actually observed inside the complex LHC particle debris? The Higgs boson itself decays almost instantly after proton collisions produce it. Scientists looked for signatures of the particles it decays into for proof of its existence.

The most common and useful Higgs decay channels include:

• Bottom quarks (58% of decays)
• W bosons (21% of decays)
• Z bosons (3% of decays)
• Tau leptons (6% of decays)
• Photon pairs (0.2% of decays)

Detecting these daughter particles required ingenious use of the capabilities of the ATLAS and CMS detectors. For example, CMS was able to precisely measure photons and electrons to observe Higgs decaying to photon pairs.

Both experiments also saw the Higgs decaying through a pair of Z bosons into four leptons. The decay into bottom quarks, the most common of all, is buried in background and was only observed by ATLAS and CMS in 2018. The combination of both detectors’ data provided unambiguous evidence that these decays originated from a new particle matching the predicted Higgs boson.

The Higgs discovery involved scrutinizing an unfathomable amount of data. In the year of detection alone, ATLAS and CMS analyzed a whopping 600 trillion proton collisions, and the LHC as a whole recorded about 27 petabytes of data that year. This required filtering using high-performance computing grids spanning 170 computing centers in 42 countries.

Out of quadrillions of collision events, only several hundred Higgs boson events needed to be pinpointed. Finding these rare gems demonstrated that these detectors could find the proverbial needle in a haystack.

Ongoing Studies of Higgs Properties

While the Higgs discovery will go down in history as a momentous scientific feat, the work is far from over. With the Higgs mechanism now confirmed, particle physicists are hard at work measuring its properties with extreme precision to see if there are clues beyond the Standard Model. So far, no oddity has held up. Ten years after the discovery, ATLAS and CMS reported that the measured Higgs couplings agree with the Standard Model predictions within current precision, so any new physics must hide in smaller deviations.

To pursue these mysteries, CERN recently upgraded the LHC to reach unprecedented collision energies. Almost twice its original power, the souped-up LHC is now poised to study the Higgs and crack other puzzles like dark matter. Hundreds of research papers continue to be published annually about the 125 GeV Higgs. Its interactions, quantum spin, parity, and more exotic decays are being intensely probed to shed light on how this boson fits into nature’s tapestry.

Over 50 years since it was first dreamed up on paper, the Higgs boson has transitioned from theory to reality, but this particle’s full secrets are still yet to be unlocked. Gaining knowledge about its place in the cosmos could uncover groundbreaking findings beyond our imagination. The Higgs discovery was just the beginning. Ongoing studies of its properties at the energy frontier promise to reveal more about the deepest laws of particle physics and our universe’s origins.

I forgot to say. No worries. The Higgs Boson is not going to destroy our world and universe !!

@online{scienceshot-higgs-boson-discovery-how-2024,
  author       = {Meroli, Stefano},
  title        = {{The Higgs Boson: Inside the Decades-Long Hunt for the "God Particle"}},
  organization = {ScienceShot},
  date         = {2024-04-09},
  year         = {2024},
  url          = {https://scienceshot.com/post/higgs-boson-discovery-how-the-god-particle-is-changing-our-world}
}