Highlights from the American Physical Society April Meeting, Atlanta
String theory’s take on the Higgs, newborn pulsars may have iron by-products, and coupled neutrons in beryllium nuclei revealed
String theory weighs in on Higgs
ATLANTA – Physicists working on big experiments at particle colliders aren’t the only ones who have something to say about the mass of the elusive Higgs boson. A theorist has now thrown his hat into the ring. Theoretical physicist Gordon Kane of the University of Michigan in Ann Arbor reported April 1 that he and colleagues have calculated the mass of the Higgs from the principles of string theory, with no additional inputs. In the standard model of particle physics, the Higgs boson is required for other particles to have mass. Kane’s team, which also reported the calculation online last December at arXiv.org, put the mass at between 105 billion and 129 billion electron volts. The proposed mass is consistent with hints of a Higgs at around 125 billion electron volts, reported later that same month by both the Atlas and CMS teams at the Large Hadron Collider near Geneva. “This is the first string theory prediction for the mass of the Higgs — ever,” Kane said.
Newborn pulsars may explain iron-rich rays
ATLANTA — Newly born pulsars might explain a weighty cosmic ray puzzle. Iron nuclei emitted from these dense spinning stellar cores left behind by supernova explosions could account for the unexpected composition of the highest-energy cosmic rays, Ke Fang of the University of Chicago reported April 2. Scientists had thought these speedy cosmic particles were primarily protons. But observations in recent years at the Pierre Auger Observatory in Argentina have revealed a surprising abundance of much heavier iron nuclei among the rays (SN: 7/18/09, p. 8). Simulations by Fang and her team suggest that young pulsars could emit iron nuclei capable of escaping through the supernova’s expanding envelope of matter that would block protons. Fewer than 0.01 percent of young pulsars outside the galaxy could emit enough iron nuclei to explain the Auger observations, Fang reported. The results are also described in a paper online at arXiv.org.
Mysterious neutron couplings
ATLANTA – A beryllium nucleus packed with 12 neutrons instead of the usual four has been spotted emitting two coupled neutrons, the first time such a neutron pair has been seen leaving a nucleus. The finding, by researchers from the MoNA collaboration, was presented March 31 by physicist Artemis Spyrou of Michigan State University in East Lansing. The result offers a new look into the forces that hold protons and neutrons together in atomic nuclei and may help scientists better understand astrophysical phenomena, such as the processes occurring in neutron stars. A paper describing the work also appeared in the March 9 Physical Review Letters.