What is the Higgs Boson?

a message from David R. Hamilton PhD
Thursday, 12 July, 2012  (posted 27 July, 2012)

Quite a few people have asked me about the Higgs Boson – or ‘God’ particle, as it’s been named – that was discovered at CERN recently. They have asked what it is and what it means for us.

The Higgs boson is a particle that gives most other particles mass.  OK, that might not mean much so let me explain it a little differently.

You can actually think of it as a field of energy and that’s an ideal analogy for how I need to explain what it is.

It’s a bit like a swimming pool that objects have to pass through. Say you had a steel ball and a dustbin lid and you had to drag both through the swimming pool. Which do you think would be easiest? The steel ball, of course! The dustbin lid would have a much greater drag factor.

The drag factor is the ‘Mass’ (or weight if that is easier to think about). The swimming pool is the Higgs field and it exerts a drag on all other particles, which mostly accounts for the differences in their masses. The Higgs boson might be thought of as a droplet of water in the swimming pool.

There’s another way you could think about it. Let’s say you have Usain Bolt, the world record holder for the 100 metres sprint (9.58 seconds) and a much less famous sprinter. Usain is much more famous so if the two sprinters walked side by side through Trafalgar Square in London, Usain would get mobbed by people, slowing down his walk. The less famous sprinter would walk right through, virtually unimpeded. You would say that Usain had greater ‘mass’. The people are the Higgs bosons and they weigh Usain down as they interact with him.

So what does that mean for you and me?

If it wasn’t for the Higgs boson most elementary particles (like quarks – that we are made of) wouldn’t have any mass and we would just be a mish-mash of particles floating in the universe, devoid of form. You wouldn’t exist, and neither would the planet Earth or the Sun. It’s kind of why some people call it the ‘God’ particle (although most physicists don’t really like the term).

So for the ordinary person it doesn’t really change anything. You exist now, partly because of the Higgs boson just as you did a few days before it was discovered. Life goes on and you’ll enjoy your morning coffee just as you did before Peter Higgs even thought up the concept of that particular boson.

It’s absolutely not the end of physics. There are still many mysteries to be probed. The Higgs boson could turn out to be not exactly as it was thought and could actually be made of smaller bits. No one knows yet. It might even by a scientific gateway that leads physicists into the search for weird new physics and even different dimensions of space and time. I think it’s all really exciting. It’s the beginning of something new!

So if you want to explain to people what the Higgs Boson is, either you can use the simple descriptions above, or you can cut it down to this simple joke:

A Higgs boson walks into a church. The priest says, ‘What are you doing in here?’ The Higgs boson replies, ‘You can’t have mass without me!’

from:    http://spiritlibrary.com/david-r-hamilton-phd/what-is-the-higgs-boson

Physicists Ecstatic Over Possible Higgs Particle Discovery

Jeanna Bryner, LiveScience Managing Editor
Date: 04 July 2012
 This track is an example of simulated data modelled for the ATLAS detector on the Large Hadron Collider (LHC) at CERN. The Higgs boson is produced in the collision of two protons at 14 TeV and quickly decays into four muons, a type of heavy electron that is not absorbed by the detector. The tracks of the muons are shown in yellow. CREDIT: CERN/ATLAS

Physicists are thrilled at today’s (July 4) announcement of the discovery of a new elementary particle that is likely the Higgs boson, an elusive particle thought to give all other matter its mass.

“To me it’s really an incredible thing that it’s happened in my lifetime,” Peter Higgs, the leader of the group that first theorized the particle in 1964 and after whom the particle is named, said during a press conference Wednesday (July 4).

Evidence for the new particle was reported today by scientists from the world’s largest atom smasher, the Large Hadron Collider in Switzerland. Researchers reported they’d seen a particle weighing roughly 125 times the mass of the proton, with a level of certainty that all but seals the deal it’s the Higgs boson. The Higgs represents the last undiscovered particle predicted by the Standard Model, the reigning theory of particle physics

Physicists involved in two experiments called CMS and ATLAS taking place at the world’s largest particle accelerator, the Large Hadron Collider (LHC), reported evidence of the particle at a seminar and press briefing today.

“As a layman I would say ‘We have it,’ but as a scientist I would have to say ‘What do we have?’ We have discovered a boson and now we have to discover what kind of boson it is,” CERN Director General Rolf Heuer said during the press briefing. [Top 5 Implications of Finding the Higgs Boson]

Even so, elation abounded with loud applause after the seminar talks.

Physicists at the CERN lab in Switzerland applaud news of the discovery of a new particle, likely the Higgs boson, July 4, 2012.
CREDIT: CERN

“It is a momentous event and I am proud to be living in these historic times. Our 40-year quest for solving a puzzle is almost ending,” Brown University professor of physics Meenakshi Narain told LiveScience. “Now we have to find out if this new particle really is the Higgs of the Standard Model or has properties which deviate from standard expectations and if there are other new particles to be discovered.”

Narain added in an email, “Our work is just beginning! It is a great leap for human kind and basic science.”

“We have been propelled to the future of particle physics towards the understanding of the fundamental properties of our universe in its entirety,” Caltech physicist Maria Spiropulu, who was in the audience at the LHC announcement, told LiveScience in an email.

Even Twitter was abuzz with terms such as #Higgs, #ICHEP2012, #CERN, Fabiola Gianotti and Joe Incandela (the names of the two scientists who presented the ATLAS and CMS findings, respectively) trending.

“5 sigma from CMS! Incredible!” tweeted @lirarandall, Harvard University theoretical physicist Lisa Randall, referring to results from two decay modes.

(To be certain they’ve made a true discovery and weren’t just seeing a fluke, physicists need to reach a level of significance of 5 sigma, which means there is only a one in 3.5 million chance the signal isn’t real. The ATLAS and CMS results reached sigma levels of 5 and 4.9, respectively.)

“The world might not change but my world (and that of a few others) certainly has,” Randall tweeted.

“This is a crucial first step in understanding mass and gravity. We have a long, long way to go. But wow, what a step. #Higgs,” tweeted @BadAstronomer Phil Plait, astronomer and author.

“We find it. WE FIND IT. Now I can cry #Higgs #Discovery,” tweeted @marcodelmastro, Marco Delmastro, LHC physicist and ATLAS researcher.

from:    http://www.livescience.com/21382-higgs-boson-discovery-physicists-reactions.html

Tevatron experiments report latest results in search for Higgs boson

March 7, 2012

EnlargeObserved and expected exclusion limits for a Standard Model Higgs boson at the 95-percent confidence level for the combined CDF and DZero analyses. The limits are expressed as multiples of the SM prediction for test masses chosen every 5 GeV/c2 in the range of 100 to 200 GeV/c2. The points are joined by straight lines for better readability. The yellow and green bands indicate the 68- and 95-percent probability regions, in the absence of a signal.The difference between the observed and expected limits around 124 GeV could be explained by the presense of a Higgs boson whose mass would lie between 115 to 135 GeV. The CDF and DZero data exclude a Higgs boson between 147 and 179 GeV/c2 at the 95-percent confidence level.

(PhysOrg.com) — New measurements announced today by scientists from the CDF and DZero collaborations at the Department of Energy’s Fermi National Accelerator Laboratory indicate that the elusive Higgs boson may nearly be cornered. After analyzing the full data set from the Tevatron accelerator, which completed its last run in September 2011, the two independent experiments see hints of a Higgs boson.

Physicists from the CDF and DZero collaborations found excesses in their data that might be interpreted as coming from a  with a mass in the region of 115 to 135 GeV. In this range, the new result has a probability of being due to a statistical fluctuation at level of significance known among scientists as 2.2 sigma. This new result also excludes the possibility of the Higgs having a mass in the range from 147 to 179 GeV.

Physicists claim evidence of a new particle only if the probability that the data could be due to a statistical fluctuation is less than 1 in 740, or three sigmas. A discovery is claimed only if that probability is less than 1 in 3.5 million, or five sigmas.

This result sits well within the stringent constraints established by earlier direct and indirect measurements made by CERN’s , the Tevatron, and other accelerators, which place the mass of the Higgs boson within the range of 115 to 127 GeV. These findings are also consistent with the December 2011 announcement of excesses seen in that range by LHC experiments, which searched for the Higgs in different decay patterns. None of the hints announced so far from the Tevatron or LHC experiments, however, are strong enough to claim evidence for the Higgs boson.

“The end game is approaching in the hunt for the Higgs boson,” said Jim Siegrist, DOE Associate Director of Science for High Energy Physics. “This is an important milestone for the Tevatron experiments, and demonstrates the continuing importance of independent  in the quest to understand the building blocks of nature.”

Physicists from the CDF and DZero experiments made the announcement at the annual conference on Electroweak Interactions and Unified Theories known as Rencontres de Moriond in Italy. This is the latest result in a decade-long search by teams of physicists at the Tevatron.

“I am thrilled with the pace of progress in the hunt for the Higgs boson. CDF and DZero scientists from around the world have pulled out all the stops to reach this very nice and important contribution to the Higgs boson search,” said Fermilab Director Pier Oddone. “The two collaborations independently combed through hundreds of trillions of proton-antiproton collisions recorded by their experiments to arrive at this exciting result.”

Higgs bosons, if they exist, are short-lived and can decay in many different ways. Just as a vending machine might return the same amount of change using different combinations of coins, the Higgs can decay into different combinations of particles. Discovering the Higgs boson relies on observing a statistically significant excess of the particles into which the Higgs decays and those particles must have corresponding kinematic properties that allow for the mass of the Higgs to be reconstructed.

“There is still much work ahead before the scientific community can say for sure whether the Higgs boson exists,” said Dmitri Denisov, DZero co-spokesperson and physicist at Fermilab. “Based on these exciting hints, we are working as quickly as possible to further improve our analysis methods and squeeze the last ounce out of Tevatron data.”

Only high-energy particle colliders such as the Tevatron and LHC can recreate the energy conditions found in the universe shortly after the Big Bang. According to the , the theory that explains and predicts how nature’s building blocks behave and interact with each other, the Higgs boson gives mass to other particles.

“Without something like the Higgs boson giving fundamental particles mass, the whole world around us would be very different from what we see today,” said Giovanni Punzi, CDF co-spokesperson and physicist at the National Institute of Nuclear Physics, or INFN, in Pisa, Italy. “Physicists have known for a long time that the Higgs or something like it must exist, and we are eager to finally pin this phenomenon down and start learning more about it.”

If a Higgs boson is created in a high-energy particle collision, it immediately decays into lighter more stable particles before even the world’s best detectors and fastest computers can snap a picture of it. To find the Higgs boson, physicists retraced the path of these secondary particles and ruled out processes that mimic its signal.

The experiments at the Tevatron and the LHC offer a complementary search strategy for the Higgs boson. The Tevatron was a proton/anti-proton collider, with a maximum center of mass energy of 2 TeV, whereas the LHC is a proton/proton collider that will ultimately reach 14 TeV. Because the two accelerators collide different pairs of particles at different energies and produce different types of backgrounds, the search strategies are different. At the Tevatron, for example, the most powerful method is to search the CDF and DZero datasets to look for a Higgs boson that decays into a pair of bottom quarks if the Higgs boson mass is approximately 115-130 GeV. It is crucial to observe the Higgs boson in several types of decay modes because the Standard Model predicts different branching ratios for different decay modes. If these ratios are observed, then this is experimental confirmation of both the Standard Model and the Higgs.

“The search for the Higgs boson by the Tevatron and LHC experiments is like two people taking a picture of a park from different vantage points,” said Gregorio Bernardi, DZero co-spokesperson at the Nuclear Physics Laboratory of the High Energies, or LPNHE, in Paris . “One picture may show a child that is blocked from the other’s view by a tree. Both pictures may show the child but only one can resolve the child’s features. You need to combine both viewpoints to get a true picture of who is in the park. At this point both pictures are fuzzy and we think maybe they show someone in the park. Eventually the LHC with future data samples will be able to give us a sharp picture of what is there. The Tevatron by further improving its analyses will also sharpen the picture which is emerging today.”

This new updated analysis uses 10 inverse femtobarns of data from both CDF and DZero, the full data set collected from 10 years of the Tevatron’s collider program. Ten inverse femtobarns of data represents about 500 trillion proton-antiproton collisions. Data analysis will continue at both experiments.

“This result represents years of work from hundreds of scientists around the world,” said Rob Roser,  co-spokesperson and physicist at Fermilab. “But we are not done yet – together with our LHC colleagues, we expect 2012 to be the year we know whether the Higgs exists or not, and assuming it is discovered, we will have first indications that it behaves as predicted by the Standard Model.”