Search for the Higgs boson narrows: Does it exist at all?

CMS / CERN

This graphic records proton collision events in the Large Hadron Collider's Compact Muon Solenoid in which four high-energy electrons (shown as red towers) are observed. The event shows characteristics expected from the decay of a Higgs boson but is also consistent with background processes.

By Robert Evans

updated 11/23/2011 8:08:31 PM ET

Print
Font:
+
-

GENEVA — CERN physicists have moved the focus of their search for the Higgs boson, the particle many think gave the universe its form after the big bang 13.7 billion years ago, to a narrow band on the mass spectrum, a spokesman said Wednesday.

Science bloggers close to the research center are suggesting it might be clear by mid-December that the boson is a chimera, and some other mechanism would have to be sought to explain how matter took on mass at the birth of the cosmos.

"The higher mass region has now been virtually ruled out, but the Higgs could still be anywhere in the lower 114-141 GeV range," James Gillies of CERN, the 21-nation European Organization for Nuclear Research near Geneva, told Reuters.

More science news from msnbc.com
1. Sandro Vannini
  Time for America to say ta-ta to Tut
  Science editor Alan Boyle's blog: Two exhibits focusing on the best-known figures from ancient Egypt, King Tut and Cleopatra, are in the last stages of their U.S. tours — and their departure could signal the end of an era.
2. 40,000 years ago: Live, from the cave, flutists!
3. Does quake reveal when Jesus died?
4. Auctioned dinosaur skeleton smuggled?

Some physicists, such as Italian Tomasso Dorigo, who works with CERN, say that the Higgs should be found at around 120 GeV. Independent British researcher Philip Gibbs, meanwhile, goes for 140 GeV.

GeV, or giga electron-volts, is a term used in physics to quantify particle energy fields. Searches for the Higgs in CERN's Large Hadron Collider and the now-closed Tevatron at Fermilab in Illinois have ranged up to 476 GeV.

Results from analysis up to the end of June in the LHC, which smashes together millions of particles per second at velocities just a tiny fraction less than the speed of light, were presented at a conference in Paris last week.

These reports slipped by almost unnoticed, even by many specialists in the particle physics community. Particle physicists have been focusing their attention on an Italian research center's claim to have recorded neutrino particles moving faster than light.

The latest Higgs findings were compiled jointly by two usually competing LHC research teams, ATLAS and CMS, and Gillies said both were working hard to try to complete analysis of data from the collider gathered up to the start of November.

Timing points to December
The 21-nation CERN's ruling Council meets from Dec. 12 to 16, and any concrete sign of the Higgs — whose existence was postulated four decades ago by British scientist Peter Higgs — could be reported during that session.

But CERN physicist and blogger Pauline Gagnon said on Wednesday that the low mass range, where scientists had always thought they would find the particle, was also the one where it would be more difficult to see. The Higgs, she said,"is playing hard to catch."

"It might be that it does not even exist," she said, a possibility already raised by other researchers and by CERN chief Rolf Heuer.

This echoed comments by Columbia University mathematical physicist Peter Woit last weekend on his Not Even Wrong blog. "It seems not impossible that the results available (publicly or not...) mid-December will come within striking distance of ruling out the Higgs (at 90 pct or 95 pct level) over the relevant low mass range," Woit wrote.

The particle is part of the decades-old Standard Model of particle physics that seeks to explain how the universe works at its most basic level, but it is almost the only element of the model whose existence has not yet been determined experimentally.

If it is not found, said Gagnon, "we need to move on to explore the next set of possibilities."

One suggestion came this week from a self-proclaimed non-scientist in a comment on the Quantum Diaries blog. "It will be in essence ethereal, kind of like a spirit being, existing for the purpose of holding everything together," he wrote.

For more about the search for the Higgs boson, check out msnbc.com's special report on the "Big Bang Machine."

Interactive: Inside the big bang machine

Above: Interactive Inside the big bang machine
Interactive Nightmares and dreams at the LHC

Show more interactives

Explainer: What’s a hadron? Tour the particle zoo

Fermilab

The Standard Model of particle physics is one of science's most successful theories, enabling the development of devices ranging from light bulbs, to microwave ovens and television, to quantum computing devices. The Standard Model is also one of the oddest theories, because it lays out a dizzying menagerie of hundreds of subatomic particles. At its heart are 16 types of elementary particles ... plus at least one more mysterious particle that scientists are spending billions of dollars to detect.

Click on "Next" to get the full rundown.
Quarks

Berkeley Lab

Six "flavors" of quarks have been detected: up and down, charm and strange, top and bottom. Quarks are almost always found in different combinations, bound together by gluons (more on those later). Particles built up from quarks and gluons are called hadrons. The Large Hadron Collider is so named because it's a large collider that smashes hadrons together.

Three-quark combinations fit in the category of baryons. The best-known baryons are the proton (with two up quarks and one down quark) and the neutron (with two down quarks and one up quark).

Particles that have one quark and one antiquark fit in the category of mesons. For example, the pion, or pi meson, contains an up quark and an anti-down quark.
Advertise | AdChoices

Leptons

Brown University

Six "flavors" of leptons have been detected: The negatively charged electron is the best-known lepton — along with its antimatter counterpart, the positron. This photo shows the path of single electrons passing through liquid helium, in an experiment devised by Brown University researchers.

The muon is also negatively charged, but it's about 207 times as massive as the electron. ("Who ordered that?" physicist Isidor Rabi reportedly asked.) The negatively charged tau particle is even bigger — 3,477 times as massive as the electron — but it decays into other particles in less than a trillionth of a second.

Each of those leptons has a neutrino associated with it: the electron neutrino, the muon neutrino and the tau neutrino. Neutrinos interact only weakly with other particles, and they zip through our planet virtually without a trace. Physicists only recently determined that they have mass, but there's still a great deal of mystery surrounding the ghostly particles.
Force carriers

Fermilab

The Standard Model sets aside a category for particles that are associated with force fields. The effect of a field can be viewed as involving an exchange of such force-carrying particles.

Four elementary force-carrying particles have been detected. The best-known force carrier is the photon — which plays a part in the electromagnetic spectrum, including visible light. The gluon binds quarks together through the strong nuclear force. The weak nuclear force involves the exchange of W and Z bosons. The W boson can carry a positive or a negative charge, while the Z boson is neutral.

If gravity could be incorporated into the Standard Model, the force-carrying particle would be called the graviton (shown here in an artist's depiction). However, gravitons have not yet been detected, and at least for now, such particles are not accounted for in the Standard Model.
Bosons vs. fermions

Rice Univ. via AIP

All force-carrying particles are bosons, but not all bosons are force carriers. The difference has to do with a property known as particle spin. Particles with a fractional spin value (for example, electrons, protons and neutrons) are fermions. Two identical fermions cannot occupy the same quantum state. This is a property that keeps electrons from collapsing into a jumble, and thus makes chemical reactions possible.

All particles with a whole-integer spin value are classified as bosons, and such particles can occupy the same quantum state even if they're identical. The photon is the best-known type of boson.

Even atoms can be classified as fermions and bosons. This photo shows how atom clouds of lithium-7 (bosons) and lithium-6 (fermions) behave at low temperatures. The bosons collapse into a compact cloud, while the fermions can't squeeze that closely together.
Advertise | AdChoices

The mysterious Higgs

Ianna Osborne / CERN / CMS Collection

The Higgs boson is the only particle predicted by the Standard Model that has not yet been detected. The Higgs is the main quarry for physicists at the Large Hadron Collider. This image is a simulation of the Higgs' signature as it might appear in one of the LHC's detectors.

The Higgs boson, named after Scottish theorist Peter Higgs, is thought to be associated with a field that endows some particles (such as the weak nuclear force's W and Z bosons) with mass, while leaving the electromagnetic force's photons without mass.

This Higgs field may have played a role at the very beginnings of the universe: Physicists believe that at the highest energies, the electromagnetic and weak nuclear forces were unified, but something led to "electroweak symmetry breaking" as the infant cosmos cooled. That would be why the electromagnetic force and the weak nuclear force are distinct in the current universe. The Large Hadron Collider could shed new light on this mysterious Higgs mechanism.
Why so complicated?

Tim Jones / McDonald Observatory / HETDEX

Hadrons and leptons? Baryons and mesons? Fermions and bosons? Sometimes it seems as if particle physicists set up these classifications just to keep outsiders totally confused. But for researchers, these occasionally overlapping categories are useful for figuring out how different types of particles interact with each other.

In a sense, it's as if we've been talking about the game of chess but have gotten only to the point of naming the different pieces on the board: black pieces and white ones, pawns and knights, bishops and rooks, kings and queens. The real meaning of the game comes out when you start studying how the pieces perform and interact.

To delve into the deeper meaning of the Standard Model, you can visit The Particle Adventure at Lawrence Berkeley National Laboratory, "A Subatomic Venture" at CERN, or Particle Physics UK.