Physics News of the Week: Results from PandaX-I and Smartphones that Detect Cosmic Rays

| October 5, 2014 | 0 Comments

This week we take a look at some amazing papers from the PandaX experiment, the astrophysicists from the universities of Padova and Cambridge and a physicist, who turned a smartphone into a cosmic ray detector. As always, for more cool stuff, register for our email newsletter.

1. A Higgs-Gravity Connection Might Leave Traces in White Dwarfs (Sep 29)

The discovery of the Higgs boson at the Large Hadron Collider (LHC) in 2012 marked an important step toward understanding the origin of the mass of fundamental particles. Since mass plays a major role in gravity, the Higgs could also reveal insights into the nature of gravity. One possibility is that the Higgs field could couple to a specific spacetime curvature, a scenario that is invoked in various extensions of the standard model.

Now, scientists have shown that dying stars called white dwarfs can be used to investigate and place limits on the coupling between the Higgs field and spacetime curvature. “Conceptually, I think that our work is trying to create a ‘common’ language between microphysics and macrophysics in the following sense,” said Roberto Onofrio, a co-author of the study. “So far, people have looked for the consequences of the Higgs field in the microworld, at the so-called Fermi scale, i.e., the attometer scale (1 am = 10-18 m), and for the consequences of gravity at the macroscopic scale, from an apple upward in terms of size and masses. Yet, both have in common the central role that mass plays in the standard model of elementary particle physics and in gravitation. So by starting to talk of masses involving both the Higgs field (which is supposed to give inertial mass to all fundamental particles) and gravitation (where the gravitational mass of a body is a key concept), one can check for their consistency or for the presence of possible contradictions.”

Now you can hunt for cosmic rays with your smartphone

2. First Dark Matter Search Results from the PandaX-I Experiment (Sep 30)

Scientists across China and the United States have been collaborating on the PandaX search for dark matter from an underground lab in southwestern China. A new report recently published at the Beijing-based journal Science China Physics, Mechanics & Astronomy discusses the results from the first stage of the experiment. PandaX is the first dark matter experiment in China that deploys more than one hundred kilograms of xenon as a detector; the project is designed to monitor potential collisions between xenon nucleons and weakly interactive massive particles, hypothesized candidates for dark matter.

“In recent years, new techniques using noble liquids (xenon, argon) have shown exceptional potential due to the capability of background suppression and discrimination, and scalability to large target masses,” state the PandaX collaborators. “The XENON10/100 and LUX experiments using the dual-phase technique have improved WIMP detection sensitivity by more than two orders of magnitude in a wide mass range.”

No dark matter signal was observed in the first PandaX-I run, however, recent results place strong constraints on all previously reported dark matter-like signals from other similar types of experiments.

3. Physicist Turns Smartphones into Pocket Cosmic Ray Detectors (Oct 2)

Even these days, when there are thousands of apps capable of doing nearly anything you could imagine doing with your phone, turning it into a cosmic ray detector sounds like something from a sci-fi movie. But it is actually true — you can now hunt cosmic rays with your phone. A new smartphone app can essentially turn Android phones into pocket cosmic ray detectors. The app, DECO, uses the phone’s camera to capture energetic subatomic light particles and log data. “The app basically transforms the phone into a high-energy particle detector,” explains Justin Vandenbroucke, a University of Wisconsin-Madison assistant professor of physics and a researcher at the Wisconsin IceCube Particle Astrophysics Center (WIPAC). “It uses the same principles as these very large experiments.”

Smartphone cameras use silicon chips that work through what is called the photoelectric effect, in which particles of light, or photons, hit a silicon surface and release an electric charge. The same is true for muons. When a muon strikes the semiconductor that underpins a smartphone camera, it liberates an electric charge and creates a signature in pixels that can be logged, stored and analyzed. A similar process is used in the new educational app called DECO.

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