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Analysis of Tevatron Data Favors Low-Mass Higgs Boson; Confirms LHC Observations

A full analysis of the Tevatron data collected over ten years – a mind boggling 500 trillion proton-antiproton collision events – yields a narrower range for the Higgs mass. A new statistical fluctuation, seen with a confidence level of 2.2 sigma, narrows the range of the particle causing the fluctuation to between 115 GeV to 135 GeV. A GeV is a Giga electron Volts or a billion electron volts. These are pretty strong bounds on the mass. Furthermore, the entire regions between 147 to 179 GeV can be safely eliminated. This analysis confirms what the LHC data says – the Higgs is a low mass Higgs with a mass of about 125-126 GeV and the mass range above 141 GeV is eliminated with 95% confidence.

The local significances of the Higgs signature, both from the LHC and the Tevatron. Notice the continuous black line rising way above the dotted black line within the 115 to 127 GeV range. The horizontal light across the graph is the Standard Model prediction probability. The actual observed probability has to be greater than this line.

Excluded ranges and the range to look out for

The data, collected from CDF and DZero detectors of the now-deceased Tevatron, combines well with the LHC data, specifically with that supplied by the ATLAS detector, to restrict the Higgs mass between 115 GeV and 129 GeV. This also provides more confidence to the 3.6 sigma peak announced during the 13th December 2011 CERN broadcast. Kindly check the link here for very specific details of the seminar: http://techie-buzz.com/science/higgs-boson-cern-seminar-results.html

However, this result shows that the LHC and the Tevatron results match and that’s great, but it doesn’t get us any closer to actually finding the Higgs. Of course, if the Tevatron had disagreed, then we would’ve been in serious trouble.

Bottom line

Two things come out of this confirmation: The Higgs is most probably a low mass Higgs, having a mass of about 125-126 GeV. This is pretty interesting in itself, since this is not just the boring Standard Model Higgs, but gives an inkling of the success of supersymmetric theories. Secondly, the “look elsewhere” effect may not be as significant as was previously thought, now that the bounds are tighter. The “look elsewhere effect” takes into account the probability of finding the Higgs at every point within a certain range and not just at a very small interval. This considerably reduces the significance of the observed bump in general. Since the “look elsewhere effect” may decrease its contribution, concentrating on local significances may be quite the right thing to do!

Of course, the game will only be decided by the LHC. We expect to have enough data to pinpoint the Higgs by the end of this year, before the LHC goes into hibernation for 15 months. The game is heating up and getting interesting. Stay tuned…

What Sank The Titanic? The Moon, Say Two Scientists

The Titanic was sunk by the moon, say two scientists, but others are not so convinced. Their claim is that a truly cosmic conspiracy was afoot on the night of January 4, 1912, which sent many icebergs hurtling towards an area, lying bang in the path of the Titanic. Although the giant ship’s crew were ultimately to blame for not responding to warnings about icebergs in the area, the duo say that this might explain why there were so many icebergs in the area to begin with.

An Astonishing night

The night of Jan 4, 1912 was an astonishing night indeed. The moon was very bright as it was a full moon night. On this night, it was extremely close to the Earth, closer than it had been in 1400 years. This is what is called a ‘supermoon’ event, when the perigee (coming closest to the Earth) and full moon coincide. On top of that, by some coincidence, the Sun, the Moon and the Earth were aligned in nearly a straight line, causing the gravitational forces of the moon and the Sun to be added and generate very high tides. If that were not enough, the Earth was also close to the Sun, with the perihelion of the Earth (position where the Earth is closest to the Sun) happening the day before. The researchers, David Olsen and Russell Doescher, both of Texas State University, argue that this astonishing series of coincidences conspired against the doomed vessel.

The supposed path of the iceberg

The pair argues that icebergs drifting southwards from the Arctic region were refloated by the increased tides. Generally, icebergs float south and then get stuck in the shallow waters near the Labrador Peninsula or Newfoundland (refer map above). This prevents them from drifting south any further. If the iceberg was set afloat once more by the high tides, then they could have indeed caught the Labrador current  and, after drifting south-east a bit, intercepted the Titanic.

Voices of skepticism

Many are not quite convinced, however! The critical question of how high the tides were has been left unanswered. Furthermore, as John Vidale, a seismologist at the University of Washington points out, to compress the normal drift time of three-and-a-half months to just a few hours or even a day or two, is to overestimate the power of the tides. In other words, the icebergs would’ve taken three-and-half months to drift that far to the south. How high must the tides be to reduce that time to just a few hours?

Also many people question the alignment of the Sun, Moon and Earth. Even slight misalignment will not work, as the force needs to be as strong as we can have.

Why the Titanic sank may not be as clear cut at these scientists are trying to make it sound. Their work appears in the April edition of the Sky and Telescope magazine and it might be an interesting read.

Mysterious Eruptions on Venus A Result Of Massive Solar Activity

Strange things are afoot on Venus and we’ve got just a hint as to what they are. Gigantic explosions have been seen on the surface of Venus, possibly triggered by the intense Solar winds, which peaked yesterday. The spectacular explosions occur just above the surface of the planet, since Venus lacks a proper magnetosphere.

How the magnetosphere of a planet shields it from a solar wind. Venus doesn't have a strong enough magnetic field.

Scientists call these Hot Flow Anomalies (HFA’s) and these are common on Saturn. They have also been seen on Mars, but this is the first time such gigantic explosions are afoot on Venus.

An Explanation

Here’s a quick explanation as to why these HFA’s actually happen. The Sun sends out millions of charged particles travelling at very high speeds towards the planet. There are often discontinuities in the solar wind, and this is recorded as a sharp change in the magnetic field of the solar winds.

HFA's on Venus. The charged particles get swept up by this moving front of weak magnetic field. (Image Courtesy: GSFC/Collinson paper)

If these areas lie parallel to the direction of wind flow, the wind can remain in contact with the contour along which the solar wind slows down and changes direction, called the bow shock (marked). If the propagation of the discontinuity is slow enough, it sweeps up enough charged particles. These charged particles form plasma, which sends shockwaves resulting in these gigantic eruptions.

Huge Energy reservoirs

This process happens on Earth too, but the strong magnetic field of the Earth prevents the process from occurring too close to the surface. These processes release a lot of energy. About the HFAs on Venus, David Sibeck, a planetary climate scientist at NASA’s Goddard Space Flight Center says:

Hot flow anomalies release so much energy that the solar wind is deflected, and can even move back toward the sun. That’s a lot of energy when you consider that the solar wind is supersonic — traveling faster than the speed of sound — and the HFA is strong enough to make it turn around.

The study regarding this phenomenon made by Glyn Collinson and David Sibeck, both from GSFC, appeared in Journal of Geophysica; Research.

Huge Solar Flare Headed Directly For Earth; To Strike In A Few Hours

A huge Solar Flare is heading towards Earth and is expected to collide in a few hours. On the 4th of March, night time in the Eastern Hemisphere, the Sun released a huge amount of charged particles travelling at large speeds in what was a X1.1 class Solar Flare. These particles are going to collide with the Earth’s atmosphere and generate spectacular auroral shows near the poles, and may even cause problems in communication in certain places.

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Direct Aim

The bad news is that this solar flare, or Coronal Mass Ejection (CME’s), ejected from the active sunspot AR1429, is aimed directly at Earth. This falls in a series of very big solar flares from the Sun over the last year or so, leading up to the maximum of the 11-year Solar Cycle in 2013. The only difference between this present one and the previous ones is that the earlier ones were not directly straight at us.

You may expect significant disturbances in satellite communications, may be even partial blackouts for a few hours. Power grids are also expected to be hit. NASA is also tracking the exact trajectory of the CME, fearing for the astronauts on the International Space Station.

The expected arrival time is about 2300 EST on 6th March, but it could be early morning on 7th March.

What To Expect

The bottomline is this: Watch out for Auroras if you are in the higher latitudes, whether in the Northern or Southern Hemisphere. In addition to that, do not be surprised if you are rendered without mobile network or even power for a few hours, especially if you reside in the higher latitudes. Do make light preparations for that.

Fireball Spotted Across Britain, Reactions Range From Excitement To Paranoia

A fireball has been spotted across the length of the British Isles, starting as north as Scotland and ending as south as Devon. At about 21:40 GMT yesterday, eyewitnesses reported seeing a “bright light” with and “orange glow” and there were fears of an aircraft crashing through the atmosphere. However, these fears were calmed by what the Met Office tweeted, slightly incorrectly:

Hi All, for anyone seeing something in the night sky, we believe it was a meteorite.

A meteor that was spotted in Australia in 2009. This is NOT what was spotted in Britain yesterday

Meteorites are large pieces of rock, which are usually the end-products of some planet forming event that didn’t quite succeed. They are the leftovers. When such a leftover piece enters the Earth’s atmosphere, it is burnt up due to friction with the atmospheric molecules. If it is big enough, it survives until impact on the Earth’s surface, earning the label ‘meteorite’ in the process. This is where the Met Office tweet goofed up; there is no evidence to show that the fireball actually landed somewhere on Earth.

The police forces were inundated with calls from frantic eyewitnesses and were busy assuring them that nothing was wrong. Here is a grainy video taken of the fireball:

From Excitement to the End of Life

Laura Yusuf of Surrey saw the fireball while driving on M6 and reported:

It was an amazing sight. Bright orange flames trailing behind it as it slowly burnt itself out,

However, many were less than rational about it. Gary Fildes, a director of a local Observatory, who also spotted the meteorite first hand, was at the receiving end of a lot of frantic calls. He recalls a particular one, which he apparently had fun answering:

They went absolutely mental. I was getting questions about what it is and is it going to end life on Earth? It was massively exciting.

The meteor was spotted as far south as Devon, meaning that it had to be a big rock that was streaking across the skies.

NASA’s Cassini Spacecraft Detects Oxygen Gas On Saturn’s Moon

It’s not quite breathable, but Saturn’s moon Dione still has a bit of molecular oxygen within its very thin atmosphere. The oxygen atoms are very sparse, only about one molecule of oxygen per 11cubic centimeters (cc) of space. The fact was reported by NASA’s Cassini Spacecraft.

An artist's impression of the Cassini spacecraft flying past Saturn.

But how did it get there?

The interesting bit about the oxygen is how it comes to be! The oxygen is not made by biological organisms, unlike here on Earth, but by physical processes like dissociation of molecules in the atmosphere due to the bombardment by highly energetic photons. They can also come from geological activity. How the tiny Dione holds on to this thin layer of gases is, however, not understood. Saturn’s biggest moon Titan, possibly the biggest in the Solar System, has a thick atmosphere, but then it’s much bigger than Dione. Dione’s atmospheric problem compounds the problem astronomers have of explaining the atmosphere around Rhea, another small satellite of Saturn.

Not that big a surprise

The detection of molecular oxygen was done using ion and neutral mass spectrometers. Earlier, Hubble had picked up the signature of ozone, so molecular oxygen was always on the cards, since ozone is just the oxygen molecule with one more oxygen atom.

It is not clear whether there are rarer gases in Dione’s atmosphere and, if present, what their composition is.

The conclusion comes from analysis of the data taken on the Cassini flyby on Dec 12, 2011.

Novel New Material Graphyne Can Be A Serious Competitor To Graphene

The carbon nanostructure revolution refuses to cease. First, it was carbon nanotubes, followed by graphene. After these two “hot” materials, it may now be the dawning of another wonder material called ‘Graphyne’. Graphyne may surpass even graphene in its electrical properties. While graphyne has been researched for the last 30 years, it has suddenly become a hot material for condensed matter physics.

An artist's impression of graphene

Graphene is known for its extremely high conductivity owing to a peculiar property of graphene electrons. In graphene, the so-called valence and conduction bands touch. Near the points where the two bands touch, called the Dirac point, the energy-momentum relation of the electrons is linear (graph, right), instead of quadratic as seen for other particles. This leads to the mass of the charge carriers (electrons or holes) inside the material being effectively zero. This allows them to travel at extremely high speeds, giving rise to very high mobilities and superior conduction properties. It was precisely this that led to the 2010 Nobel Prize being awarded to Andre Geim and his student Konstantin Novoselov.

Graphene and Graphyne

Graphyne doesn’t really exist; it has to be synthesized using special techniques. However, computer simulations show that its conduction properties can be better than graphene. Graphyne is a 2D lattice, just like graphene, but with double and triple bonds, rather than just single bonds as it is with graphene. The graphene lattice is strictly hexagonal, while graphyne lattice can take up an arbitrary shape due to the presence of the double and triple bonds. In particular, it can take up a rectangular lattice shape.

The key to good conduction is not only high mobility of the electrons, but also directionality. The electrons should be free to travel in a straight line. For graphene, the lattice has no preferred direction, but for graphyne, the lattice being rectangular, prefers conduction in one direction over the other. This means that it has gating properties depending on the direction of passage of current.

6,6,12- Graphyne

Simulations and predictions

A recent paper in Physical Review Letters, by Andreas Gorling and colleagues (link) presents simulations of electronic properties of graphyne. They discuss the so-called 6,6,12-graphyne (pic above) and simulate its properties. Density functional simulations predict the presence of Dirac cones in graphyne, which were thought to be unique to graphene. Moreover, the conduction turns out to be superior to graphene.

We should stress the fact that graphyne has not been made in the laboratory in significant quantities as yet; only trace amounts have been fabricated. Only proper experiments on real samples can verify the simulation results, but Mikhail Katsnelson, a big name in the field of graphene physics, expresses confidence in the density functional methods. The next step would be to prepare proper graphyne samples for study. Only then can all the fancy experimental tests be applied.

New material on the block and a lot of new physics to be known – it’s a mouth-watering prospect for physicists.

More about the mechanical properties of graphyne: http://web.mit.edu/mbuehler/www/papers/Carbon_2011.pdf

CP Violation: Tevatron Detector Data Reconfirms What The LHC Had Already Said

The Tevatron at Fermilab may not be active any longer, but the data it has collected over its lifetime is still capable of inspiring great thoughts. The data, now fully analysed, has revealed what the LHCb had already found earlier, thus giving more credence to hypothetical ideas. The data yields answers to questions as basic as “Why is there matter in the Universe?”.

The CDF detector

CP Violation

In November 2011, we had reported about a reported CP violation in the charm quark sector. We inferred that by looking at the so-called D0-D0 bar mixing. The news can be found here. A more detailed discussion and explanation of the various things is given here.

So, let me just quote the basic figure. The LHCb quotes a figure of 0.82% deviation from the expected value of zero, from the Standard Model. A non-zero value of CP violation goes towards answering the question of why matter won over anti-matter, when equal amounts of the two were produced right after the Big Bang. Now, the CDF gives the same hints.

The CDF quotes a deviation of 0.67 % from zero. The result says -0.67% +/- 0.16%. Alongwith the LHCb results, the CP Violation stands at 3.8 sigma confidence level.

The Standard Model predicts that if CP violation is detected, it might signal the existence of new particles. So far, we have no data to indicate that so far!

With Upgrades, LHC Will Be More Energetic And Be Able To Handle More Collisions

The LHC is taking a vacation right now, but it promise to return with a bang! The LHC is due to run very soon, but instead of the usual 7 TeV (1TeV = 1 Trillion electron volts) total energy, it will try and go a bit higher and reach 8 TeV. Also the luminosity (basically number of collisions per second) will increase, but the increase won’t be substantial and there are reasons for that. Physicists promise enough data to pinpoint the Higgs and to verify the tantalizing 125 GeV peak that was reported earlier(here). Furthermore, after a packed 2012 schedule, the LHC will hibernate for a longer time and will wake up in 2014. During this time, the LHC will be fitted with newer instruments.

More work: ATLAS detector

Upgrade

The hardware upgrade will have to wait till end of 2012, when the LHC will shut down for an extended period of 14 months, waking up again in 2014. The hardware upgrade will allow the LHC to run at a huge energy of 14 TeV and much higher luminosity. This is crucial, since it is not only the energy, but the number of collisions that makes a lot of difference in the experimental data. More luminosity means lower uncertainty in the measured values. The current electronics won’t be able to handle the rate of data acquisition that the LHC is planning to achieve.

Higher luminosity

The LHC currently runs at 3.5 TeV per beam, giving 7 TeV on a two-beam collision. They plan to upgrade it to 4 TeV per beam, giving a total energy of 8 TeV. Each beam of protons is made up of bunches of protons, with each bunch being separated by a certain amount of time. Each bunch has a certain number of protons. The team will also look to increase the number of protons per bunch, but keep the number of bunches constant, thereby increasing the luminosity. The current bunch spacing is 50 nanoseconds. The LHC electronics is built so as to handle bunches separated by 25 ns. The LHC team might look at this small deadtime when it resumes in 2014.

All in all, the full blown search for Higgs might end soon, but the LHC is poised for more daring adventures!

NASA Clocks Record Breaking Winds Around a Black Hole

NASA announced earlier this week that astronomers using the Chandra X-ray Observatory observed the fastest winds ever blowing off a disk around a stellar-mass black hole. These observations shed some new light on the mysterious black holes and how they behave.

Blackhole
Artists Rendering of Stellar-Mass Blackhole (Courtesy NASA.gov)

So what kind of speed does it take to break a record? How does 20 million mph strike you? Speeds like that are hard to fathom. To put in perspective that is 3% of the speed of light. Ashley King, of the University of Michigan is quoted in the NASA press release as saying, “This is like the cosmic equivalent of winds from a category five hurricane.” Ashley was the lead in the study which was published in The Astrophysical Journal Letters.

Stellar-mass black holes are created when a super massive stars collapse. These are stars are usually about 10 times the mass of the sun. An interesting point about this discovery oddly enough, was that this particular black hole was behaving like black holes with much higher mass. “It’s a surprise this small black hole is able to muster the wind speeds we typically only see in the giant black holes,” said co-author Jon M. Miller, also from the University of Michigan. “In other words, this black hole is performing well above its weight class.”

There were several unexpected findings surrounding this observation. For instance, the wind seems to be carrying more material away from the black hole than it is taking in. Unlike hurricane winds here on earth, the stellar-mass black hole winds travel in all directions.

For more information about the Chandra X-ray Observatory, visit http://www.nasa.gov/chandra.