The Higgs Boson particle since its inception has kept the scientists and physicists curious about the existence of particle mass and the mechanism. The Higgs mechanism that features the Higgs field and Higgs boson is assumed to provide mass to elementary particles. Over the past few years, particle physicists have been able to come up with what is called ‘Standard Model’ to put everything under a framework, which primarily focuses on fundamental particles and forces of nature.
This standard model is supposed to provide answers to questions such as how is mass provided to particles and why do particles need mass at all? A major chunk of the answer lies in a quantum field that is responsible for providing mass to particles, which is known as the Higgs field. Today, physicists and scientists believe that the Higgs field does exist due to the fact that the field itself is responsible for giving mass to the particles and that the fundamental particles do carry mass.
To better understand the Higgs Boson phenomenon, we need to go back in time and study the concept in detail.
Higgs Boson’s Origin
Physicists in the early 1960s had a strong theory of electromagnetic interactions along with a description of the weak nuclear interaction. This nuclear interaction is basically a force that makes the sunshine as well. Constant research and study allowed the physicists to discover deep similarities between the two interactions.
However, there was a slight problem that needed to be overcome. The concept needed a theory that would explain that the particles are massless, even though in reality they do carry mass.
The year 1964 gave birth to the missing piece of the puzzle. Francois Englert, Robert Brout, and Peter Higgs through their independent efforts were able to come up with a concrete theory known as the Brout-Englert-Higgs mechanism.
A unique point of this theory was that it could provide mass to the elementary particles while allowing them to retain their original interactions. At the same time, the structure, most importantly the theory could be predictive at high energy levels. As a result of the theory, particles that carry a relatively lower pass would acquire mass by interacting with the Higgs field. However, a particle such as Photon which carries the electromagnetic reaction would remain massless.
In the past, the only time the particles had interacted with the Higgs field was just 10-12 after Big Bang had occurred. Before this interaction, it is said that all the particles were traveling at the speed of light and carried no mass. After a while, as the universe expanded and the particles cooled, they interacted with the Higgs field, which gave them mass. Furthermore, the BEH mechanism states that the mass carried by elementary particles depends on how strongly the particles had interacted with the Higgs field. At the moment, these theories cannot be used to predict such values. However, if the mass of a particle is measured, its interaction with the Higgs field could be measured as well.
Although the BEH mechanism had several limitations and loose ends, it went onto become the most popular concept in particle physics. Its untied ends continue to make particle physicists work harder than ever to prove the phenomenon once and for all.
Accelerator, Higgs & Experiments
The Large Electron-Positron Collider was the very first accelerator that was able to reach the Higgs Boson’s particle mass range. Although it was unsuccessful in finding Higgs Boson, it paved the way for further research. As a result, physicists were now aware that the mass should be greater than 114 GeV.
In 1984, several CERN engineers and physicists aimed to install a proton-proton accelerator in the same tunnel that consisted of LEP.
This accelerator would possess a very high collision energy of 10-20 TeV. Considering that the luminosity is very high, this accelerator would help the engineers and physicists probe the Higgs’s possible range of mass. However, each collision due to high luminosity would give rise to thousands of other mini-collisions. Considering the detecting technology of the time, it was impossible to detect that. As a result, CERN immediately launched R&D for introducing newer detector technology, which brought in several collaborations as well.
On the theoretical side, the physicists made quite a bit of progress in the 90s by producing the Higgs Boson via the proton-proton collision. This also gave them an insight into all its different decay modes. One thing that needed to be considered was since the decay modes were strongly dependent on unknown Higgs Boson mass, the detector technology should be able to both measure all particle kinds and cover a wide mass range. Using intensive simulations, each decay mode was studied thoroughly and proved to be a significant help in bringing the benchmark detector design to life.
Meanwhile, engineers and physicists at the Fermi National Accelerator Laboratory were making progress towards discovering Higgs Boson by using the Tevatron collider with having a mass of 160 GeV. Then in 2008, after putting in countless hours of research and construction, the LHC along with its detectors were ready for the first beams. 10th September 2008 was a big day in the history of particle physics when CERN had invited authorities and press to witness the first injection of beams.
At first, the machine worked like a miracle but after ten days the LHC got damaged due to a problem that had occurred in the superconducting magnets. It took an entire year to fix the damage but physicists were able to determine the problem along the way as well. It was found that the collision energy was limited to 7 Tev, which was far less as compared to what colliders possessed.
Higgs Boson Discovery
Since Higgs Bosons are extremely rare, the physicists needed to be careful to detect and spot the important signal events from those that were existing in the background. As already mentioned, the collision would give rise to thousands of other collisions in the background. Therefore, detecting the right collision was complicated and a big task.
Once the important signals are determined, thorough and powerful statistical methods are used to study the power and significance of the signal. As soon as the information arrived, physicists got right down to studying the mass of the particles but the dataset ultimately decreased soon after it displayed a rising trend.
Decades’ worth of hard work was brought to life when the LHC’s energy was increased from 7 to 8 Tev. The results arrived quickly by the end of summer 2012 and ATLAS had collected 5 FB-1 at 8 TeV, which doubled the dataset. This was the long-sought victory that was finally achieved.
A seminar was organized on 4th July 2012 by ATLAS and CMS, which caught the attention of a huge audience. People queued all night to reserve a seat for themselves. Both ATLAS and CMS presented their research and results consecutively and the seminar was concluded by CERN’s Director-General Rolf Heuer with his remark ‘I think we have it’.
Concluding, as physicists and engineers continue to study the Higgs Boson phenomenon, one thing is for sure and that is the strength of the interaction is dependent on the mass of the particle. The heavier the particle, the stronger its interaction will be with the Higgs field. As of today, physicists and engineers are working on discovering new properties that will further pave the way for new physics. Even though researchers have not been able to come up with an unexpected discovery in a while, it does not mean that the research will stop. Until Higgs Boson is discovered in its purest form without any limitations, the quest will continue.