English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

On 23rd November 2009, during the early commissioning of the CERN LargeHadron Collider (LHC), two counter-rotating proton bunches were circulated forthe first time concurrently in the machine, at the LHC injection energy of 450GeV per beam. Although the proton intensity was very low, with only one pilotbunch per beam, and no systematic attempt was made to optimize the collisionoptics, all LHC experiments reported a number of collision candidates. In theALICE experiment, the collision region was centred very well in both thelongitudinal and transverse directions and 284 events were recorded incoincidence with the two passing proton bunches. The events were immediatelyreconstructed and analyzed both online and offline. We have used these eventsto measure the pseudorapidity density of charged primary particles in thecentral region. In the range |$\eta$| < 0.5, we obtain dNch/deta = 3.10 $\pm$0.13 (stat.) $\pm$ 0.22 (syst.) for all inelastic interactions, and dNch/deta =3.51 $\pm$ 0.15 (stat.) $\pm$ 0.25 (syst.) for non-single diffractiveinteractions. These results are consistent with previous measurements inproton-antiproton interactions at the same centre-of-mass energy at the CERNSppS collider. They also illustrate the excellent functioning and rapidprogress of the LHC accelerator, and of both the hardware and software of theALICE experiment, in this early start-up phase.

european physical journal. c, particles and fields

First proton-proton collisions at the LHC as observed with the ALICE  detector: measurement of the charged particle pseudorapidity density at  $\sqrt{s}$ = 900 GeV