Six years after the discovery of the Higgs boson, physicists have observed it decaying to fundamental particles known as bottom quarks. The discovery is a huge contribution to scientists’ understanding of the Standard Model of particle physics and the universe at large. The finding was presented on Tuesday at CERN1 by the ATLAS and CMS collaborations at the Large Hadron Collider (LHC). In 2012, physicists discovered the Higgs boson - an elementary particle predicted by the Standard Model which relates to how objects have mass.

The Standard Model of particle physics predicts that about 60 percent of the time a Higgs boson will decay to a pair of bottom quarks - the second-heaviest of the six flavours of quarks. The finding provides major support for the Standard Model, which has many implications for how we understand the world and the universe. Jessie Shelton, a high-energy particle physicist at the University of Illinois said: “The Higgs boson is the least well-known and in many ways the most baffling particle in the standard model. “Observing its decay to bottom quarts is a major milestone in our understanding of its properties.”

The discovery of the decay has been a long time coming, as there are many other ways of producing bottom quarks in proton-proton collisions. This makes it hard to isolate the Higgs boson decay from the background “noise” associated with such processes. The finding is another big step to better understand the Higgs boson and the universe. Each new discovery or observation, has the potential to give way to new questions and experiments.

James Beacham, an experimental high-energy particle physicist said: “First [you] discover the thing. Then you want to measure everything about it.” Karl Jakobs, spokesperson of the ATLAS collaboration, said the observation is a “major milestone in the exploration of the Higgs boson.” He said: “It shows that the ATLAS and CMS experiments have achieved deep understanding of their data and a control of backgrounds that surpasses expectations. “ATLAS how now observed all couplings of the Higgs boson to the heavy quarks and leptons of the third generation as well as all major production modes.” </s> Aug. 28 (UPI) -- Particle physicists have finally witnessed the decay of a Higgs boson particle into two bottom quarks.

Models predict Higgs boson particles decay into two bottom quarks 60 percent of the time. Bottom quarks, or b quarks, are the second heaviest of the six types of quarks.

Scientists have struggled to directly observe the predicted decay. Several types of proton-proton collisions can produce bottom quarks, making it difficult to link quarks produced by particle collisions with decaying Higgs boson particles.

Pairs of photons produced by decaying Higgs boson particles is much easier spot among the "noise" produced by high-energy particle collisions.

During experiments, scientists regularly witnessed the Higgs boson decaying into photons, tau-leptons, and W and Z bosons, but b quarks proved hard to see.

To isolate the link between decaying Higgs boson particles and pairs of bottom quarks, scientists combined the observations of the two particle detectors at CERN's Large Hadron Collider, ATLAS and CMS.

Physicists applied complex statistical analysis to the combined dataset. According to CERN, the analysis methods revealed "the decay of the Higgs boson to a pair of bottom quarks with a significance that exceeds 5 standard deviations."

"This observation is a milestone in the exploration of the Higgs boson," Karl Jakobs, spokesperson of the ATLAS collaboration, said in a news release. "It shows that the ATLAS and CMS experiments have achieved deep understanding of their data and a control of backgrounds that surpasses expectations."

Scientists working on the ATLAS experiment have now witnessed Higgs bosons decay into all of the heavy quarks and leptons predicted by particle physics models, including the Standard Model.

"Since the first single-experiment observation of the Higgs boson decay to tau-leptons one year ago, CMS, along with our colleagues in ATLAS, has observed the coupling of the Higgs boson to the heaviest fermions: the tau, the top quark, and now the bottom quark," said Joel Butler, spokesperson of the CMS collaboration. "The superb LHC performance and modern machine-learning techniques allowed us to achieve this result earlier than expected."

Researchers detailed their breakthrough in a scientific paper, published online this week. Scientists previously presented their findings at the 2018 International Conference on High Energy Physics in Seoul, South Korea.

Scientists hope their latest feat will pave the way for the detection of even more elusive decays, as well as the exploration of physics beyond the Standard Model.

"The analysis methods have now been shown to reach the precision required for exploration of the full physics landscape, including hopefully new physics that so far hides so subtly," said Eckhard Elsen, director of research and computing at CERN. </s> A candidate event display for the production of a Higgs boson decaying to two b-quarks (blue cones), in association with a W boson decaying to a muon (red) and a neutrino. The neutrino leaves the detector unseen, and is reconstructed through the missing transverse energy (dashed line). Credit: ATLAS Collaboration/CERN

Six years after its discovery, the Higgs boson has at last been observed decaying to fundamental particles known as bottom quarks. The finding, presented today at CERN by the ATLAS and CMS collaborations at the Large Hadron Collider (LHC), is consistent with the hypothesis that the all-pervading quantum field behind the Higgs boson also gives mass to the bottom quark. Both teams have submitted their results for publication today.

The Standard Model of particle physics predicts that about 60% of the time a Higgs boson will decay to a pair of bottom quarks, the second-heaviest of the six flavours of quarks. Testing this prediction is crucial because the result would either lend support to the Standard Model – which is built upon the idea that the Higgs field endows quarks and other fundamental particles with mass – or rock its foundations and point to new physics.

Spotting this common Higgs-boson decay channel is anything but easy, as the six-year period since the discovery of the boson has shown. The reason for the difficulty is that there are many other ways of producing bottom quarks in proton–proton collisions. This makes it hard to isolate the Higgs-boson decay signal from the background "noise" associated with such processes. By contrast, the less-common Higgs-boson decay channels that were observed at the time of discovery of the particle, such as the decay to a pair of photons, are much easier to extract from the background.

To extract the signal, the ATLAS and CMS collaborations each combined data from the first and second runs of the LHC, which involved collisions at energies of 7, 8 and 13 TeV. They then applied complex analysis methods to the data. The upshot, for both ATLAS and CMS, was the detection of the decay of the Higgs boson to a pair of bottom quarks with a significance that exceeds 5 standard deviations. Furthermore, both teams measured a rate for the decay that is consistent with the Standard Model prediction, within the current precision of the measurement.

Candidate event display for the production of a Higgs boson decaying to two b-quarks. A 2 b-tag, 2-jet, 2-electron event within the signal-like portion of the high pTV and high BDTVH output distribution is shown (Run 337215, Event 1906922941). Electrons are shown as blue tracks with a large energy deposit in the electromagnetic calorimeter, corresponding to light green bars. Two of them form an invariant mass of 93.6 GeV, compatible with a Z boson. The two central high-pT b-tagged jets are represented by light blue cones. They contain the green and yellow bars corresponding to the energy deposition in the electromagnetic and hadronic calorimeters respectively, and they have an invariant mass of 128.1 GeV. The value of pTV is 246.7 GeV, and BDTVH output value is 0.47. Credit: ATLAS Collaboration/CERN

"This observation is a milestone in the exploration of the Higgs boson. It shows that the ATLAS and CMS experiments have achieved deep understanding of their data and a control of backgrounds that surpasses expectations. ATLAS has now observed all couplings of the Higgs boson to the heavy quarks and leptons of the third generation as well as all major production modes," said Karl Jakobs, spokesperson of the ATLAS collaboration.

"Since the first single-experiment observation of the Higgs boson decay to tau-leptons one year ago, CMS, along with our colleagues in ATLAS, has observed the coupling of the Higgs boson to the heaviest fermions: the tau, the top quark, and now the bottom quark. The superb LHC performance and modern machine-learning techniques allowed us to achieve this result earlier than expected," said Joel Butler, spokesperson of the CMS collaboration.

With more data, the collaborations will improve the precision of these and other measurements and probe the decay of the Higgs boson into a pair of much-less-massive fermions called muons, always watching for deviations in the data that could point to physics beyond the Standard Model.

Candidate event display for the production of a Higgs boson decaying to two b-quarks. A 2-tag, 2-jet, 0-lepton event within the signal-like portion of the high pTV and high BDTVH output (Run 339500, Event 694513952) is shown. The ETMiss, shown as a white dashed line, has a magnitude of 479.1 GeV. The two central high-pT b-tagged jets are represented by light blue cones. They contain the green and yellow bars corresponding to the energy deposition in the electromagnetic and hadronic calorimeters respectively. The dijet invariant mass of 128.1 GeV. The BDTVH output value is 0.74. Credit: ATLAS Collaboration/CERN

"The experiments continue to home in on the Higgs particle, which is often considered a portal to new physics. These beautiful and early achievements also underscore our plans for upgrading the LHC to substantially increase the statistics. The analysis methods have now been shown to reach the precision required for exploration of the full physics landscape, including hopefully new physics that so far hides so subtly," said CERN Director for Research and Computing Eckhard Elsen.

Explore further New level of precision achieved in combined measurements of Higgs boson couplings

More information: Observation of Higgs boson decay to bottom quarks. arXiv:1808.08242 [hep-ex] Observation of Higgs boson decay to bottom quarks. arXiv:1808.08242 [hep-ex] arxiv.org/abs/1808.08242 </s> Six years after the strange, elusive Higgs boson particle was discovered, scientists working with the world's largest particle accelerator have finally observed its mysterious, yet most common, decaying process.

Using data from the Large Hadron Collider, physicists caught the boson decaying into two smaller particles - a bottom quark and its antimatter equivalent, an antibottom quark.

The Standard Model of particle physics predicts that a Higgs boson will decay into bottom quarks - the second-heaviest of the quark flavours - about 60 percent of the time.

Physicists have been trying to observe this process, because it will either support the Standard Model, or show that it's insufficient - requiring a search for new physics to explain the discrepancy.

The problem is that the process is extraordinarily hard to catch in action. The Higgs boson is produced by a collision between two protons. If two gluons inside the protons fuse and produce two top quarks, these top quarks can recombine into a Higgs boson.

This particle exists for about one-septillionth of a second before it decays into less massive particles. It's the detection of these particles from which particle physicists infer the existence of the Higgs boson.

There are several ways these particles decay, including into a fermion-antifermion pair, a pair of photons, or a pair of gauge bosons, which are relatively easy to observe.

But with bottom quarks, it gets a little trickier, because every proton-proton collision produces a shower of subatomic particles, including bottom quarks. These then rapidly decay into other particles.

Since the Higgs boson's existence is so brief, it's been impossible to determine whether the bottom quarks detected were the result of a decaying Higgs boson, or of proton collision background processes.

To find the decay, two collaborations - ATLAS and CMS - combined data from the first and second runs of the Large Hadron Collider, and analysed it to try and find bottom quarks from the particle showers they produced. Then they had to trace those bottom quarks back to a Higgs boson.

"Finding just one event that looks like two bottom quarks originating from a Higgs boson is not enough," said Chris Palmer, a physicist at Princeton University who worked on the CMS analysis.

"We needed to analyse hundred of thousands of events before we could illuminate this process, which is happening on top of a mountain of similar-looking background events."

However, there are a few particles that are identifiable by-products of the Higgs boson production mechanism.

"We used these particles to tag potential Higgs events and separate them out from everything else," Palmer explained. "So we really got a two-for-one deal with this analysis because not only did we find the Higgs decaying to bottom quarks, but we also learned a lot about its production mechanisms."

And they confirmed - again - the Standard Model of particle physics, with which the measured rate of decay matched.

It's a result that opens a new possibility for scientists to study the behaviour of the Higgs boson in closer detail, and how it interacts with other matter, plus whether it could interact with particles that haven't been discovered yet (such as dark matter).

The next step in the research is to refine the measurements to study the decay mode in much higher resolution.

Both collaborations have submitted their papers for publication in science journals, and in the meantime can be found on arXiv: the CMS research is available here, and the ATLAS research is available here. </s> Today at CERN, the Large Hadron Collider collaborations ATLAS and CMS jointly announced the discovery of the Higgs boson transforming into bottom quarks as it decays. This is predicted to be the most common way for Higgs bosons to decay, yet was a difficult signal to isolate because background processes closely mimic the subtle signal. This new discovery is a big step forward in the quest to understand how the Higgs enables fundamental particles to acquire mass.

After several years of refining their techniques and gradually incorporating more data, both experiments finally saw evidence of the Higgs decaying to bottom quarks that exceeds the 5-sigma threshold of statistical significance typically required to claim a discovery. Both teams found their results were consistent with predictions based on the Standard Model.

“The Higgs boson is an integral component of our universe and theorized to give all fundamental particles their mass,” said Patty McBride, distinguished scientist at Fermi National Accelerator Laboratory and recently elected deputy spokesperson of the CMS experiment. “But we haven’t yet confirmed exactly how this field interacts—or even if it interacts—with all the particles we know about, or if it interacts with dark matter particles, which remain to be detected.”

Higgs bosons are only produced in roughly one out of a billion LHC collisions and live only a tiny fraction of a second before their energy is converted into a cascade of other particles. Because it’s impossible to see Higgs bosons directly, scientists use these secondary particle decay products to study the Higgs’ properties. Since its discovery in 2012, scientists have been able to identify only about thirty percent of all the predicted Higgs boson decays.

“We expected the Higgs would decay into bottom quarks most often, but it is crucial to see and measure it,” said Young-Kee Kim, the Louis Block Distinguished Service Professor in Physics and chair of the Department of Physics at the University of Chicago, who worked on the bottom quark decay of the Higgs with the ATLAS experiment in the past. “We now have seen all of the primary decay modes of the Higgs predicted by the current theory of particle physics, the Standard Model. This marks a very important moment in particle physics!”

According to Viviana Cavaliere, a physicist at DOE’s Brookhaven National Laboratory who works on the ATLAS experiment, finding the Higgs boson decaying into bottom quarks has been priority number one for the last several years because of its large decay rate.

“Theory predicts that sixty percent of Higgs bosons decay into bottom quarks,” said Cavaliere, who is also using this process to search for new physics. “Finding and understanding this channel is critical because it opens up the possibility for us to examine the behavior of the Higgs, such as whether it could interact with new, undiscovered particles.”

The Higgs field is theorized to interact with all massive particles in the Standard Model, the best theory scientists have to explain the behavior of subatomic particles.

“However, questions remain which cannot be answered by the Standard Model,” said Kim. “For example, is the Higgs responsible for giving mass to dark matter particles, the dominant form of matter in the universe?”

Kim's group is currently studying whether or not some fraction of Higgs bosons created in the LHC decay into dark matter particles.

Even though this decay is the most popular path, spotting it in the experimental data was no walk in the park. Every proton-proton collision at the LHC produces a splattering of subatomic byproducts, one of the most common being bottom quarks. These bottom quarks then quickly decay into other kinds of particles, leaving behind vast showers of particles in the detectors. Tracing these particle showers back to two bottom quarks (and then figuring out which ones came from a Higgs boson) is extremely delicate and labyrinthine work.

“Being able to identify and isolate bottom quarks in the experimental data is a huge challenge and required precise detector calibration and sophisticated tagging capabilities to identify b-quarks,” said Giacinto Piacquadio, a physicist at Stony Brook University who co-leads the Higgs-to-bottom-quarks analysis group. “We were only able to do these analyses thanks to years of work that came before.” </s> PARIS-Six years after tracking down the Higgs boson, the subatomic particle that confers mass on matter, physicists said Tuesday they have “at long last” witnessed it decaying into tiny bits called “bottom quarks”.

The predicted decay was observed at the Large Hadron Collider (LHC) famous for the Nobel-capped discovery of the Higgs particle in 2012, Europe’s CERN physics lab announced.

“During the early preparations of the LHC, there were doubts on whether this observation could be achieved,” the ATLAS scientific collaboration said of the “elusive interaction” now documented at the massive particle accelerator.

Because Higgs bosons themselves are hard to find, and other particles also break up into bottom quarks, it has been difficult to track down those attributed specifically to Higgs decay.

Researchers say the long-awaited observation serves as further verification of the Standard Model of physics - the mainstream theory of the fundamental particles that make up the Universe and the forces that govern them.

Under the model, developed in the early 1970s, quarks and leptons are the most basic building blocks of matter.

There are six types of quarks, of which bottom quarks - also called beauty quarks - are among the heaviest.

The Standard Model predicted that Higgs decay would yield pairs of bottom quarks about 60 percent of the time.

But finding these quarks has been “among the most demanding analyses carried out by ATLAS so far,” the team said in a statement.

Scientists probing the nature and workings of the Higgs and other particles are on the lookout for anything that does not fit with Standard Model predictions.

This is because the model doesn’t explain dark matter or dark energy, and appears to be incompatible with the theory of gravity.

Some other model of “new physics” is needed to explain these.

Proposed alternatives have included the existence of extra dimensions, or “supersymmetry” which postulates the existence of a sibling of equal mass for every known Standard Model particle.

Evidence for neither has yet been found.

The latest observation was also “consistent with” the Standard Model, said the CMS team that worked with ATLAS on the project. But it “still leaves room for contributions from new physics.”

“It’s another point for the Standard Model,” physicist Pauline Gagnon told AFP.

While it was an important scientific breakthrough, the observation was also “a disappointment (for physicists) because the Standard Model has not yet been disproven.”

Physicists have sifted through mountains of experimental data these last years to piece together a profile of the elusive Higgs boson first predicted in 1964.

They have so far observed its mass, spin, and lifetime.

“In the coming years, much more data will be collected and the precision will be improved in our quest to see if the Higgs boson reveals the presence of physics beyond the Standard Model,” said the CMS collaboration. </s> The ATLAS collaboration at the Large Hadron Collider has excitingly observed the Higgs boson decaying.

In a momentous event for physics, CERN physicists collaborating through ATLAS and CMS have finally, at long last, observed the Higgs boson particle decaying into bottom quarks, a new discovery which has been six years in the making after the exciting announcement of the Higgs boson in 2012.

According to ATLAS, the transition into two bottom quarks is estimated to account for around 60 percent of Higgs boson decays. ATLAS spokesperson Karl Jakobs announced the results of the ATLAS collaboration at the Large Hadron Collider today, noting that there were certainly doubts as to whether physicists would be able to catch the Higgs boson disintegrating.

“ATLAS is proud to announce the observation of this important and challenging Higgs boson decay. While the result is certainly a confirmation of the Standard Model, it is equally a triumph for our analysis teams. During the early preparations of the LHC, there were doubts on whether this observation could be achieved. Our success is thanks to the excellent performance of the LHC and the ATLAS detector, and the application of highly sophisticated analysis techniques to our large dataset.”

Physicists were curious to see whether the decay of the Higgs boson would follow the Standard Model of particle physics which gives the prediction that 60 percent of Higgs boson decays will see the Higgs particle continuing life as bottom quarks which, out of the six different flavors of quarks, just happens to be the second heaviest out of them all.

This made the new experiment all the more important as physicists would then know with the results whether the Standard Model, which provides quarks with mass, should be used or whether physicists needed to look at a completely new kind of physics.

Part of the reason why it has taken six years to spot the Higgs boson decay is because there are actually quite a few different ways in which to use proton-proton collisions to create bottom quarks. Because of this, it is quite difficult to “isolate the Higgs-boson decay signal from the background noise associated with such processes.”

However, Higgs boson decay channels that aren’t quite as common, like the process of photons decaying, are much simpler to differentiate from background noise, and it was determined that the decay of the Higgs boson was in keeping with the Standard Model prediction.

“To extract the signal, the ATLAS and CMS collaborations each combined data from the first and second runs of the LHC, which involved collisions at energies of 7, 8 and 13 TeV. They then applied complex analysis methods to the data. The upshot, for both ATLAS and CMS, was the detection of the decay of the Higgs boson to a pair of bottom quarks with a significance that exceeds 5 standard deviations.”

Now that CERN physicists at the Large Hadron Collider have successfully observed the Higgs boson decaying into a pair of bottom quarks, they will be gathering more data and continuing with their measurements of the Higgs into other decays, including its decay into muons. </s> It’s been over half a decade since scientists working with the Large Hadron Collider (LHC) managed to capture what they believed was the elusive “God Particle” that would help tie together a few loose ends in our understanding of particle physics. It’s called the Higgs Boson and its discovery was a momentous occasion, but it also presented a few more questions that researchers desperately wanted to answer.

Now, with even more data from the Large Hadron Collider, a team of physicists has evidence to support previous theories about how the Higgs Boson behaves. That’s good news, because if the predictions didn’t pan out we might be looking for an entirely new model to explain how the most basic building blocks of our universe work.

Observing the behavior of a Higgs Boson is difficult because it decays rapidly. It turns into other particles in an instant, and figuring out what particles it turns into has been challenging ordeal for scientists. This new discovery revolves around what is called a “bottom quark.”

Existing models suggested that the Higgs Boson usually decays into the particles called bottom quarks. Bottom quarks have mass, and proving that the Higgs Boson decays turns into a pair of those particles was the focus of the research. Watching it happen would be impossible without the help of the extremely sensitive instruments in the LHC, but the researchers have now been able to isolate the feedback from that specific transition and demonstrate that the Higgs particle does indeed produce a pair of heavy bottom quarks more often than not.

“This observation is a milestone in the exploration of the Higgs boson,” Karl Jakobs, a member of the collaboration which conducted the research, explains. “It shows that the ATLAS and CMS experiments have achieved deep understanding of their data and a control of backgrounds that surpasses expectations. ATLAS has now observed all couplings of the Higgs boson to the heavy quarks and leptons of the third generation as well as all major production modes.”

In short, this is good news for physicists who work with what is known as the Standard Model of particle physics. If scientists hadn’t been able to observe the action, or if they saw something completely different in the resulting data, researchers would have to seriously consider a total revamp of one of the most basic physics models in use today. Thankfully, that’s not the case. </s> European scientists said Thursday they have discovered a new subatomic particle containing a never-before-seen combination of quarks — the most basic building blocks of matter.

The particle, a baryon dubbed Xicc++, contains two heavy "charm" quarks and one "up" quark, and has about four times the mass of a more familiar baryon — the proton.

The particle is predicted in the Standard Model of particle physics, and its discovery was "not a shock," said Matthew Charles of the LPNHE physics lab in Paris.

He is one of about 800 scientists to attach their names to the discovery by the Large Hadron Collider (LHC) of the European Organization for Nuclear Research (CERN).

The collider is most famous for discovering the Higgs boson, which confers mass on matter.

The new particle is the first seen with two such heavy quarks, said the team.

There are six types of quark, with exotic names such as "charm," "strange," and "beauty."

The "charm," "top," and "bottom" quarks are the heaviest types.

Quarks make up baryons such as protons and neutrons that comprise most of the mass in the known universe.

Baryons gather together in atoms, which form the molecules that constitute matter.

"This type of particle, these doubly-charmed baryons... they've been quite elusive," Charles told AFP.

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From their short-lived existence in the early Universe, none are left today. And to produce them in the lab requires an extreme concentration of energy, such as can be generated by the new, upgraded LHC.

The Xicc++ is an unstable baryon, said Charles. It lives for "a very small fraction of a second" before decaying into other, lighter particles.

Its discovery will allow scientists to continue testing the Standard Model of physics — the mainstream theory of the fundamental particles that make up matter, and the forces that govern them.

It does not, however, explain dark matter, or why there is more matter than anti-matter in the universe.

Critically, the model is incompatible with Einstein's theory of general relativity — the force of gravity as we know it does not seem to work at the subatomic quantum scale.

"A big part of our work as a field is trying to put our finger on the place where the Standard Model breaks down," to eventually find alternative explanations, said Charles.

"We're testing things in as many different places as we can," he said. "One of the things we... will be able to do with particles like this is to use them... for making further tests."
For the first time, scientists observe the Higgs Boson decay into bottom quarks. This supports a prediction in the Standard Model of particle physics.