Continue reading page |1 |2The physics world is buzzing with news of an unexpected sighting at Fermilab’s Tevatron collider in Illinois – a glimpse of an unidentified particle that, should it prove to be real, will radically alter physicists’ prevailing ideas about how nature works and how particles get their mass.
The candidate particle may not belong to the standard model of particle physics, physicists’ best theory for how particles and forces interact. Instead, some say it might be the first hint of a new force of nature, called technicolour, which would resolve some problems with the standard model but would leave others unanswered.
The observation was made by Fermilab’s CDF experiment, which smashes together protons and antiprotons 2 million times every second. The data, collected over a span of eight years, looks at collisions that produce a W boson, the carrier of the weak nuclear force, and a pair of jets of subatomic particles called quarks.
Physicists predicted that the number of these events – producing a W boson and a pair of jets – would fall off as the mass of the jet pair increased. But the CDF data showed something strange (see graph): a bump in the number of events when the mass of the jet pair was about 145 GeV.
Posts Tagged ‘particles’
Mystery signal at Fermilab hints at ‘technicolour’ force – physics-math – 07 April 2011 – New Scientist
April 8, 2011Trapping antihydrogen
December 20, 2010
Trapping antihydrogen
Are there any unexpected differences between matter and antimatter? The international ALPHA collaboration has taken an important step toward answering that question by constructing an apparatus at CERN that can confine freshly made atoms of antihydrogen, the bound state of an antiproton and a positron, for nearly 0.2 seconds—long enough for the antimatter to be examined spectroscopically. A hot plasma of roughly 104 antiprotons—produced by slamming 26-GeV protons into a metal target—is cooled and introduced into one end of the apparatus, while about 106 low-energy positrons from the decay of radioactive sodium are introduced into the other. Electric fields gently nudge the charged species together in the heart of the device, pictured here, where they mix at cryogenic temperatures and form antihydrogen. If their kinetic energies are low enough—in temperature units, less than 0.5 K—the antihydrogen atoms are held in the grip of a superconducting octupole magnet and solenoidal “mirror” coils that together interact with the atoms’ magnetic moments. When the magnetic fields are abruptly turned off, the atoms are released and their spatial distribution captured by a three-layer silicon detector, which locates the atoms’ annihilations and distinguishes them from events triggered by lone antiprotons and stray cosmic rays. In 335 trial runs, the researchers confirmed that 38 antihydrogen atoms had survived in the trap for at least 172 ms. Although the trapping rate per atom produced is low—about 10−5—the achievement sets the stage for precision spectroscopy and antihydrogen tests of fundamental symmetries and gravitation. (G. B. Andresen et al., Nature 468, 673, 2010.)—R. Mark Wilson
Incredible shrinking proton raises eyebrows – physics-math – 07 July 2010 – New Scientist
July 9, 2010
How big is a proton? The most accurate measurement yet suggests it’s smaller than we thought. This could be due to an error – or it might just hint at totally new particle physics.
“The new experiment presents a puzzle with no obvious candidate for an explanation,” says Peter Mohr of the international Committee on Data for Science and Technology (CODATA), which calculates values for fundamental constants in physics, who was not involved in the new work.
Like most quantum objects, a proton is fuzzy around the edges. Its size is defined by the extent of its positive charge rather than a crisp physical boundary. This charge radius cannot be measured directly but can be inferred from the hydrogen atom, which consists of a proton and an electron.
The electron can sit in a variety of energy “shells”, each with a different distribution in space. One shell’s distribution requires the electron to dive in and out of the proton, and another sits entirely outside the proton. The energies of both of these shells can be combined to deduce the proton’s radius, using a theory known as quantum electrodynamics (QED). (in newscientist.com) (more…)
Proton smallest that we thought
July 7, 2010“The proton seems to be 0.00000000000003 millimetres smaller than researchers previously thought, according to work published in today’s issue of Nature.” in Nature.com (more…)
LHC – Nascimento
September 10, 2008LHC
LHC First Beam on
10 September 2008
Primeira experiência do LHC
Geneva, 10 de Setembro de 2008. O primeiro teste com um feixe de milhões de protões no acelerador LHC (Large Hadron Collider) do Laboratório Europeu de Física de Partículas (CERN) foi bem sucedido, percorrendo os 27 quilómetros às 10h28min desta manhã. Este evento histórico marca um momento chave na transição, com mais de duas décadas de preparação, para uma nova era de descobertas científicas.
First beam in the LHC – accelerating science
Geneva, 10 September 2008. The first beam test, with millions of protons, in the Large Hadron Collider (LHC) at CERN was successfully. The beam covered a distance around the full 27 kilometres at 10h28 this morning. This historic event marks a key moment in the transition to a new era of scientific discovery.
(in CERN)
