Large Hadron Collider produces first physics results

Dec 15, 2009
Large Hadron Collider (LHC)

( -- The first paper on proton collisions in the CERN Large Hadron Collider (LHC) - designed to provide the highest energy ever explored with particle accelerators - is published online this week in the European Physical Journal C.

On 23 November 2009, during the early commissioning of the CERN (European Organization for Nuclear Research) LHC - which was built in the circular tunnel of 27km circumference previously used by the Large Electron-Positron collider (LEP) - two counter-rotating bunches were circulated concurrently for the first time in the machine, at the LHC injection of 450 GeV per beam.

A total of 284 collisions were recorded by the ALICE experiment and immediately reconstructed and analyzed. The researchers determined the average number of charged particles emitted perpendicular to the beam direction, known as ‘pseudorapidity density’. Their aim was to compare their results with previous measurements of proton-antiproton collisions at the same energy, and to establish a reference for comparison with future measurements at higher LHC energies.

The paper by the ALICE collaboration, which brings together authors from 113 research institutes, describes the experimental conditions in detail, as well as the main features of the ALICE detector systems used for the analysis.

The results obtained are consistent with earlier measurements of proton-antiproton interactions at the same energy. They also compare with model calculations.

Dr. Jürgen Schukraft from CERN and ALICE spokesperson said: “This important benchmark test illustrates the excellent functioning and rapid progress of the LHC accelerator, and of both the hardware and software of the ALICE experiment, in this early start-up phase. LHC and its experiments have finally entered the phase of physics exploitation.”

Explore further: Single laser stops molecular tumbling motion instantly

More information: Alice Collaboration (2009). First proton-proton collisions at the LHC as observed with the ALICE detector: measurement of the charged particle pseudorapidity density at Ös = 900 GeV. European Physical Journal C, DOI:10.1140/epjc/s10052-009-1227-4

A Large Ion Collider Experiment. For more information on the ALICE experiment, see:

add to favorites email to friend print save as pdf

Related Stories

Large Hadron Collider sets new power world record

Nov 30, 2009

( -- CERN's Large Hadron Collider has today become the world's highest energy particle accelerator, having accelerated its twin beams of protons to an energy of 1.18 TeV in the early hours of the ...

Particles are back in the LHC

Oct 26, 2009

During the last weekend (23-25 October) particles have once again entered the LHC after the one-year break that followed the incident of September 2008.

CERN announces start-up date for Large Hadron Collider

Aug 07, 2008

CERN has today announced that the first attempt to circulate a beam in the Large Hadron Collider (LHC) will be made on 10 September. This news comes as the cool down phase of commissioning CERN's new particle ...

CMS celebrates the lowering of its final detector element

Jan 22, 2008

In the early hours of the morning the final element of the Compact Muon Solenoid (CMS) detector began the descent into its underground experimental cavern in preparation for the start-up of CERN’s Large Hadron Collider ...

Recommended for you

New method for non-invasive prostate cancer screening

11 hours ago

Cancer screening is a critical approach for preventing cancer deaths because cases caught early are often more treatable. But while there are already existing ways to screen for different types of cancer, ...

How bubble studies benefit science and engineering

12 hours ago

The image above shows a perfect bubble imploding in weightlessness. This bubble, and many like it, are produced by the researchers from the École Polytechnique Fédérale de Lausanne in Switzerland. What ...

Famous Feynman lectures put online with free access

13 hours ago

( —Back in the early sixties, physicist Richard Feynman gave a series of lectures on physics to first year students at Caltech—those lectures were subsequently put into print and made into text ...

Single laser stops molecular tumbling motion instantly

17 hours ago

In the quantum world, making the simple atom behave is one thing, but making the more complex molecule behave is another story. Now Northwestern University scientists have figured out an elegant way to stop a molecule from ...

User comments : 3

Adjust slider to filter visible comments by rank

Display comments: newest first

3.7 / 5 (6) Dec 15, 2009
translation the collator works. I know the y have to publish but as they will tell you this really a no news news report.
not rated yet Dec 15, 2009
Having said that, Joe ... it did not breakdown or produce a black hole into which Europe fell.

That's (good) news.
not rated yet Dec 15, 2009
Nothing was done at higher energies than before so... it still might.