Experiment could help explain why we, and all things, exist

<body leftmargin="0" bgcolor="#000060" text="#FFFFFF" link="#FFFF00" vlink="#FF9900"> <p class="MsoNormal"><b><font face="Arial" size="5">Experiment could help explain why we, and all things, exist</font></b></p> <p class="MsoNormal"><font size="1" face="Arial">Posted March 23</font><font face="Arial"><font size="1">, 2005<br> Special to World Science<br> </font> <br> </font> <b><font face="Arial" size="2">Scientists are shooting a beam of minute particles through solid earth for a distance equivalent to eight hours’ driving, in an experiment that might help explain why we and all things around us exist.</font></b> </p> <p class="MsoNormal"><b><font face="Arial" size="2">The experiment, launched this month, involves shooting the ephemeral, nearly undetectable particles, called neutrinos, underground between two sites 735 km (450 miles) apart. They’ll go from beneath Fermilab, near Chicago, to the Soudan iron mine in northeastern Minnesota.<br> <br> The neutrinos zip through Earth virtually unhindered because they’re immune to most of nature’s forces, including forces that make other particles bounce off each other rather than go through each other. In fact, trillions of naturally produced neutrinos pass harmlessly through you each second.<br> <br> At the mine location, a detector catches some of the neutrinos, though only about one in a billion, thanks to this same tendency of theirs to soar through things. The detector is built to analyze how the neutrinos have changed during their trip. The project is called MINOS, for Main Injector Neutrino Oscillation Search. <br> <br> The experiment takes place underground because neutrinos are so hard to detect—“like listening for a gnat’s whisper in a hurricane,” one physicist famously put it—that detectors must be well shielded from the noise of background radiation.<br> <br> All this effort is supposed to help edge science toward an understanding of why material things in the universe, such as ourselves and all the stuff around us, exist. <br> <br> Neutrinos “may well explain the origin of the neutrons, protons and electrons that are the building blocks of all the atoms in the universe,” said Michael Turner, the National Science Foundation’s Assistant Director for Mathematics and the Physical Sciences, upon inaugurating the experiment earlier this month.<br> <br> Why? The reason is related to the fact that they’re the only material particles that respond significantly to just one of the four known forces that make anything happen in the universe. This force—called the weak force because it’s the feebler of two that act at ranges smaller than an atomic nucleus—is thought to possibly explain the existence of material things, or matter. This is because the force might solve a problem in accounting for matter’s existence.<br> <br> The difficulty is that the universe contains both matter and a sort of mirror-image matter called antimatter. The two tend to merge and annihilate each other, so if the universe in its infancy contained equal amounts of each, they would have long since disappeared. Thus physicists believe some process created a slight excess of matter over antimatter during the early universe, so that enough matter was left over after the annihilation to make all the objects we see.<br> <br> But current theories can’t easily explain what created this excess of matter.<br> <br> The weak force might help. Physicists believe this force can change certain types of particles into other types. And it’s the only force that can change the balance between matter and antimatter in the process.<br> <br> The reason it might create matter preferentially over antimatter is that some interactions involving the weak force violate a principle, called CP symmetry, obeyed by other forces. <br> <br> CP symmetry holds that interactions among subatomic particles play out identically if each particle is replaced with its antiparticle, and also if we flip the particles’ spatial arrangement, switching up and down, left and right, front and back.<br> <br> According to CP symmetry, any process that creates matter creates an equal amount of antimatter. But CP symmetry-violating processes can create different amounts. Such processes are known to occur among particles known as quarks, which make up atoms, but their violation of CP symmetry is far too small to account for the matter in the universe, scientists say.<br> <br> If neutrinos also violate CP symmetry, though, physicists think their interactions could generate the necessary amount of enough extra matter.<br> <br> The MINOS experiment, along with others, could help explain whether neutrinos violate CP symmetry sufficiently for this purpose. It would do this by analyzing how neutrinos change their type, or “flavor,” during their trip in the beam. <br> <br> This flavor-changing ability of neutrinos is a quirk of theirs that scientists learned of six years ago. <br> <br> Scientists can construct equations to describe the probability that a given particle will change its type after a certain amount of time. It turns out that these equations, in order to match experimental results, must sometimes contain imaginary numbers—that is, square roots of negative numbers, which don’t exist in “normal” math.<br> <br> If these equations contain imaginary numbers, according to physicists, it indicates that the particles are violating CP symmetry. And if those particles are neutrinos, it means we might have them to thank for our existence.<br> <br> “MINOS by itelf does not have sensitivity to detect CP violation,” wrote Stanley G. Wojcicki of Stanford University in Stanford, Calif., a spokesman for the experiment, in an email to World Science. But it’s “the first experiment in what will have to be a world wide program, lasting a decade or more, where successive experiments will build on what we learned previously.”<br> <br> Scientists believe the findings might provide clues to not only CP symmetry-breaking, but also other fundamental laws of the universe. They might do this by shedding light on theories that try to explain nature’s four forces—gravity, electromagnetism, the weak force and the strong force—which holds atomic nuclei together—as manifestations of a single primordial force.</font></b> </p> </body>