Announcement

Collapse
No announcement yet.

Strange turn for protons

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Strange turn for protons

    Physics Web, UK
    June 20 2005

    Strange turn for protons
    20 June 2005

    Nuclear physicists have found further evidence that strange quarks
    can contribute to the structure of the proton. The latest data from
    the G-Zero experiment at the Thomas Jefferson National Accelerator
    Facility (JLAB) in the US lend further support to recent results from
    the HAPPEx experiment, also at JLAB, and other experiments in the US
    and Germany. The results could shed more light on the strong
    interaction that holds quarks together in protons, neutrons and other
    particles (Phys. Rev. Lett. to be published).

    Quarks come in six different flavours -- up, down, strange, charm,
    bottom and top. A proton contains two up quarks and one down quark
    that are held together by gluons, but occasionally these gluons can
    fluctuate into quark-antiquark pairs. Although these virtual quarks
    only exist for very short times, they can affect the properties of
    the proton, such as its magnetic moment. Since the strange quark is
    the next-lightest quark after the up and down quarks, it is the most
    likely to have a measurable effect.

    One way to observe the influence of strange quarks on the proton is
    to compare measurements that probe the weak interaction with those
    that probe the electromagnetic force. In the G-Zero experiment, a
    high-energy beam of electrons was fired at a hydrogen target. The
    beam was polarised so that the spins of the electrons either pointed
    in the same direction as the beam or in the opposite direction. The
    team then measured the rate at which these electrons scattered off
    protons in the target.

    The difference for the two beam polarizations was about 10 parts per
    million. This asymmetry occurs because the electromagnetic force
    conserves "parity" (that is, it does not change when all three
    directions in space are reversed), while the weak force does not.

    According to the G-zero team -- which includes physicists from
    Armenia, Canada, France and the US -- this difference implies that
    strange quarks must be contributing to magnetic moment and charge
    distribution of the proton. The results agree with those recently
    reported by the HAPPEx experiment, the SAMPLE experiment at the
    MIT-Bates Lab in the US and the A4 experiment at Mainz in Germany.

    http://physicsweb.org/articles/news/9/6/13/1

    From: Emil Lazarian | Ararat NewsPress
Working...
X