mercredi 14 décembre 2016

ATLAS releases first measurement of W mass using LHC data

CERN - European Organization for Nuclear Research logo.

14 Dec 2016

Image above: ATLAS is one of the four major experiments at the LHC. It is a general-purpose particle physics experiment run by an international collaboration (Image: Claudia Marcelloni/ CERN).

The ATLAS collaboration today reports the first measurement of the W boson mass using Large Hadron Collider (LHC) proton–proton collision data at a centre-of-mass energy of 7 TeV.

Graphic above: The ATLAS measurement of the W boson mass (in red) is compared to the Standard Model prediction (in purple), and to the combined values measured at the LEP and Tevatron collider (in blue) (Image: ATLAS Collaboration/CERN).

The W boson was discovered in 1983 at the CERN SPS collider and led to a Nobel prize in physics in 1984. Although the properties of the W boson have been studied for more than 30 years, measuring its mass remains a major challenge. A precise measurement of the W boson mass is vital, as a deviation from the Standard Model’s predictions could hint at new physics.

The latest results from ATLAS show a measured value of 80370±19 MeV, which is consistent with the Standard Model prediction. It is also consistent with the combined values measured at the LEP and Tevatron colliders, and with the world average (see graph above).

Measuring the W mass is particularly challenging at the LHC, compared to previous colliders, due to the large number of interactions per beam crossing. Despite this, the ATLAS result matches the best single-experiment measurement of the W mass (performed by the CDF collaboration

Read more on the ATLAS experiment’s website:


CERN, the European Organization for Nuclear Research, is one of the world’s largest and most respected centres for scientific research. Its business is fundamental physics, finding out what the Universe is made of and how it works. At CERN, the world’s largest and most complex scientific instruments are used to study the basic constituents of matter — the fundamental particles. By studying what happens when these particles collide, physicists learn about the laws of Nature.

The instruments used at CERN are particle accelerators and detectors. Accelerators boost beams of particles to high energies before they are made to collide with each other or with stationary targets. Detectors observe and record the results of these collisions.

Founded in 1954, the CERN Laboratory sits astride the Franco–Swiss border near Geneva. It was one of Europe’s first joint ventures and now has 22 Member States.

Related links:

Large Hadron Collider (LHC):

SPS collider:

LEP collider: http://about/accelerators/large-electron-positron-collider

Tevatron collider:

W boson:

Standard Model:

For more information about European Organization for Nuclear Research (CERN), Visit:

Image (mentioned), Graphic (mentioned), Text, Credits: CERN/Harriet Kim Jarlett.

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