First proton–proton collisions at the LHC as observed with the ALICE detector: measurement of the charged-particle pseudorapidity density at GeV

European Physical Journal C (Impact Factor: 5.44). 01/2010; 65(1):111-125.

ABSTRACT On 23rd November 2009, during the early commissioning of the CERN Large Hadron Collider (LHC), two counter-rotating proton
bunches were circulated for the 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 pilot bunch per beam, and no systematic attempt was made to optimize the
collision optics, all LHC experiments reported a number of collision candidates. In the ALICE experiment, the collision region
was centred very well in both the longitudinal and transverse directions and 284 events were recorded in coincidence with
the two passing proton bunches. The events were immediately reconstructed and analyzed both online and offline. We have used
these events to measure the pseudorapidity density of charged primary particles in the central region. In the range |η|<0.5, we obtain dN
ch/dη=3.10±0.13(stat.)±0.22(syst.) for all inelastic interactions, and dN
ch/dη=3.51±0.15(stat.)±0.25(syst.) for non-single diffractive interactions. These results are consistent with previous measurements
in proton–antiproton interactions at the same centre-of-mass energy at the CERN Sp
S collider. They also illustrate 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.

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    ABSTRACT: A Large Ion Collider Experiment (ALICE) is an experiment de- signed to probe the inner depths of matter. Specically it aims to un- derstand the hot and dense matter created during collisions of heavy lead ions in the CERN Large Hadron Collider. It is believed that just after the collision the matter will be in a state called the quark- gluon plasma(QGP) where quarks become deconned. Aside from an overview of the ALICE detector, this paper will discuss the physics of the QGP, detection methods, previous discoveries about the QGP along with the current status of ALICE.
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    ABSTRACT: The results from first series of measurements performed by the ALICE experiment at the LHC are presented. These measurements include the charged-particle pseudorapidity densities, multiplicity distributions and transverse momentum spectra obtained by analyzing the data collected in 2009 and 2010 in proton-proton collisions at three different center-of-mass energies of 0.9, 2.36, and 7 TeV. The results are compared to previous proton-antiproton data and to model predictions.
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    ABSTRACT: Renormdynamic equations of motion and their solutions are given. New equation for negative binomial distribution and Riemann zeta function invented.
    Physics of Atomic Nuclei 07/2012; 75(7). DOI:10.1134/S1063778812070071 · 0.60 Impact Factor

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