Evidence of a new particle that could break the standard model of physics is mounting

Evidence of a new particle that could break the standard model of physics is mounting

The results of a new investigation into strange flashes of light picked by the Large Hadron Collider (LHC) back in December have just been announced at a conference in Italy, and physicists are getting cautiously excited that they could be the signs of new particle that could break the standard model of physics. 

While further experiments are still needed to confirm if this apparent excess of photons really is evidence of a new particle, the fact that no one's been able to disprove what physicists have seen hints that we could be close to discovering something extraordinary. "If this thing turns out to be real, it’s a 10 on the Richter scale of particle physics," physicist John Ellis from King’s College London, and the former head of theory at CERN, told The Guardian. "One’s excitometer gets totally broken."

"I would love for it to persist, but I’ve seen so many effects come and go that I have to say in my heart of hearts I’m not very optimistic," says Ellis. "It would be such a fantastic discovery if it were true, precisely because it’s unexpected, and because it would be the tip of an iceberg of new forms of matter."

Back in December, physicists were abuzz with news that the LHC’s two main detectors, Atlas and CMS, had both seen the same small 'blips' in their data that could not be explained by our current understanding of the laws of physics. 

When protons were smashed together inside these massive detectors, the reaction had produced slightly more high-energy photons (light particles) than our best theories of physics predict, Ian Sample explains at The Guardian. 

Specifically, both the CMS and ATLAS detectors recorded a spike in activity at a particular energy level, corresponding to around 750 giga electronvolts (GeV) - or roughly 750 billion electron volts. 

Found hidden in the debris of these proton-proton collisions, this unexplained signal could be the sign of a new particle that resembles the Higgs boson, only it’d be around 12 times heavier, with a mass of 1,500 GeV, teams of physicists analysing the data announced last year. 

At the time of the discovery, some physicists were referring to the hypothetical new particle as Higgs boson’s heavier cousin. Others think the light blips could signify that the Higgs boson itself is made up of a bunch of smaller particles.

Or perhaps these were signs of the existence of a graviton - an hypothesised force-carrying particle for gravity. "That would be truly remarkable: so far, gravity has proved impossible to reconcile with theories of other particles and forces," says Sample.

They were exciting results, and since December, more than 200 papers have been published discussing what they could possibly mean, but it’s going to take a whole lot more than similar blips in two detectors for us to determine if this is 'real' evidence of a new particle, or simply a statistical error. 

Put simply, the physicists behind the experiments probably wouldn’t have even mentioned it if it hadn’t turned up in both detectors.

"When all the statistical effects are taken into consideration ... the bump in the Atlas data had about a 1-in-93 chance of being a fluke - far stronger than the 1-in-3.5-million odds of mere chance, known as 5-sigma, considered theGOLDstandard for a discovery," Dennis Overbye wrote for The New York Times back in December. "That might not be enough to bother presenting in a talk, except for the fact that the competing CERN team, named CMS, found a bump in the same place."

Now, three months later, the CMS and ATLAS teams have gone over their data with a fine-toothed comb, and presented the results of their latest analyses at a particle physics conference in Italy last week. 

After collecting additional data, and recalibrating the December results over and over, both teams cannot discount the anomaly as a statistical error, which is good news for everyone hoping that this is the start of something big. The bad news is that they still can’t explain it, and they still need a whole lot more proof before we can call this a "discovery".

Interestingly, while the excess of photons picked up by the CMS experiment has now become slightly more significant, thanks to the results of the new analysis, the significance seen by ATLAS actually declined, leaving many to ponder what that actually means. 

As Davide Castelvecchi and Elizabeth Gibney report for Nature, the new analysis of the the statistical significance of the CMS bump has now gone up from 1.2 to 1.6 sigma, while ATLAS’s statistical significance now sits at 1.9 sigma after corrections. 

Sample says the chance of a 1.9 sigma effect being a fluke is the same as flipping a five heads in a row - hard, but not impossible. According to the rules of science, you can’t say something’s a discovery until you hit that 5-sigma mark - the same as tossing 21 heads in a row.

We’re now left playing the waiting game once again, but not for long. The LHC will be woken up from its winter hibernation over the next week, and will be up and running again by the end of April, which means more proton-proton collisions, and a whole lot more data for the ATLAS and CMS teams to prove or disprove their results.

As Castelvecchi and Gibney write for Nature, "by June, or August at the latest, CMS and ATLAS should have enough data to either make a statistical fluctuation go away - if that’s what the excess is - or confirm a discovery", and we can’t wait. Watch this space.

neutrinos nobel prize

Neutrinos and the Nobel Prize

Neutrino experiments are difficult and often ground-breaking. In (sometimes long-delayed) recognition of this, a number of pioneers of neutrino physics have been awarded the Nobel Prize for Physics.

1988	Leon Lederman, Melvin Schwartz, Jack Steinberger	for the neutrino beam method and the demonstration of the doublet structure of the leptons through the discovery of the muon neutrino
1995	Frederick Reines	for the detection of the neutrino
2002	Raymond Davis and Masatoshi Koshiba	for pioneering contributions to astrophysics, in particular for the detection of cosmic neutrinos

In addition, Wolfgang Pauli (1945), Enrico Fermi (1938), and Lee and Yang (1957), who made major contributions to neutrino theory, won the Nobel Prize for work not directly connected with neutrinos. Clyde Cowan did not share in the belated prize for the discovery of the neutrino because Nobel prizes are not awarded posthumously.

The Nobel Prize in Physics 2015

The Nobel Prize in Physics 2015

The Nobel Prize in Physics 2015 was awarded jointly to Takaaki Kajita and Arthur B. McDonald "for the discovery of neutrino oscillations, which shows that neutrinos have mass"

Photo © Takaaki Kajita

Takaaki Kajita

Prize share: 1/2

Photo: K. MacFarlane. Queen's University /SNOLAB

Arthur B. McDonald

Prize share: 1/2

Our own genes can block HIV

                              Our own genes can block HIV

       Two groups of researchers at the University of Massachusetts Medical School say a powerful weapon against the AIDS virus may exist in the unlikeliest of places — in our own genes.

The studies, published online yesterday in the journal Nature, found that two genes can block HIV from spreading to other cells, which researchers in the HIV/AIDS field say could open the door to promising new treatments and could even pave the way for a cure.

Two groups of UMass Medical researchers used different methods in each study, but came to the same conclusion: the SERINC5 and SERINC3 genes can shut down the virus, stopping its spread and rendering it inactive.

But a component of the virus — the protein Nef — counteracts the SERINCs inhibiting powers, which is why those genes don’t prevent people from contracting the virus.

The finding, though, could very well lead to treatments that weaken the damaging protein and allow the virus-fighting genes to fend off illness, researchers say.

“Nef is a gene that HIV evolved largely to overcome this anti-viral factor that our cells make,” said Dr. Jeremy Luban, professor of molecular medicine at UMass Medical, an investigator in one of the studies.

“The hope is that there will be 
a way to intervene, perhaps by developing a new drug that 
allows the SERINCs to escape from Nef,” Luban said.

Ideally, the discoveries will lead to the development of treatments in the next five years, though it 
is difficult to estimate, Luban said.

The research, funded primarily by the National Institutes of Health, was done in collaboration with scientists at the Univer-
sity of Trento in Italy and the University of Geneva in Switzerland.

The discovery coincides with new HIV guidelines issued yesterday by the World Health Organization, increasing the number of those infected or at risk who should seek virus-inhibiting therapy by 9 million.

“Advancing science is a critical part of what needs to happen,” said Dr. Carlos Del Rio, chairman-elect of the HIV Medicine Association.

“Gene therapy advances for HIV are very exciting. They could lead to treatments that can cure HIV,” Del Rio said.

Though there are more than 30 of these therapies available, they can cause a range of side effects, from skin rashes and nightmares to weakened bones and cardiovascular disease, according to 
Dr. Daniel Kuritzkes, chief of 
Infectious Diseases at Brigham and Women’s Hospital.

“Not everyone tolerates the currently available regimen equally well,” Kuritzkes said.

“We still need to keep looking for new and improved treatments.”

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Cell Division and Cancer

Cancer cells are cells gone wrong — in other words, they no longer respond to many of the signals that control cellular growth and death. Cancer cells originate within tissues and, as they grow and divide, they diverge ever further from normalcy. Over time, these cells become increasingly resistant to the controls that maintain normal tissue — and as a result, they divide more rapidly than their progenitors and become less dependent on signals from other cells. Cancer cells even evade programmed cell death, despite the fact that their multiple abnormalities would normally make them prime targets for apoptosis. In the late stages of cancer, cells break through normal tissue boundaries and metastasize (spread) to new sites in the body.

How Do Cancer Cells Differ from Normal Cells?

In normal cells, hundreds of genes intricately control the process of cell division. Normal growth requires a balance between the activity of those genes that promote cell proliferation and those that suppress it. It also relies on the activities of genes that signal when damaged cells should undergo apoptosis.

Cells become cancerous after mutations accumulate in the various genes that control cell proliferation. According to research findings from the Cancer Genome Project, most cancer cells possess 60 or more mutations. The challenge for medical researchers is to identify which of these mutations are responsible for particular kinds of cancer. This process is akin to searching for the proverbial needle in a haystack, because many of the mutations present in these cells have little to nothing to do with cancer growth.

Different kinds of cancers have different mutational signatures. However, scientific comparison of multiple tumor types has revealed that certain genes are mutated in cancer cells more often than others. For instance, growth-promoting genes, such as the gene for the signaling protein Ras, are among those most commonly mutated in cancer cells, becoming super-active and producing cells that are too strongly stimulated by growth receptors. Some chemotherapy drugs work to counteract these mutations by blocking the action of growth-signaling proteins. The breast cancer drug Herceptin, for example, blocks overactive receptor tyrosine kinases (RTKs), and the drug Gleevec blocks a mutant signaling kinase associated with chronic myelogenous leukemia.

Other cancer-related mutations inactivate the genes that suppress cell proliferation or those that signal the need for apoptosis. These genes, known as tumor suppressor genes, normally function like brakes on proliferation, and both copies within a cell must be mutated in order for uncontrolled division to occur. For example, many cancer cells carry two mutant copies of the gene that codes for p53, a multifunctional protein that normally senses DNA damage and acts as a transcription factor for checkpoint control genes.

New Graphene __ Black Phosphorus

NEW GRAPHENE

Atoms-thin flakes of phosphorus have a crucial property that graphene lacks

Chemists first synthesized black phosphorus over a hundred years ago. But it was only last year when anybody really took interest in the flaky black stuff. In a series of experiments reported in the first half of 2014, researchers were able to exfoliate black phosphorus into very thin films of only about 10 to 20 atoms thick. Now black phosphorus has become the new darling of two-dimensional materials research and a new hope for a postsilicon world.

The excitement around black phosphorus, which is also called phosphorene in reference to its 2-D cousin graphene, stems mainly from the fact that it has an inherent bandgap, something that graphene lacks. A bandgap, an energy band in which no electron states can exist, is essential for creating the on/off flow of electrons that are needed in digital logic and for the generation of photons for LEDs and lasers.

Black phosphorus doesn’t just have any bandgap. Its bandgap can be fine-tuned by adjusting the number of layers of the material, explains Philip Feng, an assistant professor of electrical engineering and computer science at Case Western Reserve University.

The bandgap can be dialed up from 0.3 to 2.0 electron volts. That’s a range covering a regime otherwise unavailable to all other recently discovered 2-D materials. It bridges the bandgaps of graphene (0 eV) and of transition-metal dichalcogenides such as molybdenum disulfide, which range from 1.0 to 2.5 eV.

By combining this bandgap tuning with different choices of contact materials, scientists at Sungkyunkwan University, in South Korea, were recently able to build both n-type transistors—those conducting electrons—and ambipolar transistors, which conduct both holes and electrons. Such a mix brings the material closer to mimicking the complementary logic used in today’s silicon chips.

Scientists are also excited about black phosphorus for photonics, “since optoelectronic functions, including light absorption, emission, and modulation, of semiconductor materials depend on the size of the bandgap,” says Mo Li, a photonics expert at the University of Minnesota. Black phosphorus’s bandgap range means it can absorb and emit light with wavelengths of 0.6 to 4.0 micrometers—covering the visible to infrared. That spectrum could be key to its use in sensors and in optical.

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Graphene Keeping It Cool In Electronics

By Dexter Johnson

Cooling fans and other system-level solutions are reaching their limits as circuit densities continue to grow. It’s no wonder then that graphene’s remarkable heat conductivity has led to a lot of research into using it to forthermal management in electronics.

Now an international team of researchers, organized by a team at the University of Michigan, has found that layered graphene can be an important tool for thermal management because of its ability to release heat efficiently.

In research published in the journal Nature Communications, the scientists demonstrated that the electrostatic interactions between electrically charged particles—known as Coulomb interactions—in  different layers of multi-layered graphene offers a key mechanism for dispersing heat. This occurs despite the fact that all electronic states are strongly confined within individual 2D layers.

“We believe that this cooling mechanism is not limited to multilayer graphene samples but is likely to be important in many other new, layered nanomaterials under active development by the scientific community,” said Theodore Norris, who led the research, in a press release.

This mechanism came as a bit of surprise to the researchers. They did not expect the heat building up in the electrons of the graphene to travel well through the layers because previous observations had shown that the graphene layers interact too strongly for this to occur. This stood in contrast to 3D pieces of silicon that are capable of conducting heat in any direction.

Momchil Mihnev, a doctoral student at the University of Michigan and first author on the paper, explained in the press release that while the electrons in the different layers can’t mechanically come in contact with each other, they do manage to interact with each other through their electrical charges.

When the negative charges repel each other, the electrons take on an effective size that extends between the layers. When the electrons come in contact with each other in this way, the hotter electrons transfer heat to the colder ones. This transfer of heat eventually channels down through the graphene towards the layer that is closest to the silicon carbide substrate the researchers used in these experiments. Once it gets to the final layer of graphene, the heat transfers into the silicon carbide.

The researchers have developed a detailed theory on why and how this mechanism works, and it could provide an important tool in keeping electronics cool well into the future.