The ALICE trigger system installed in the experimental cavern processes information from triggering detectors at 3 hardware levels, and is used in p-p and Pb-Pb collisions. Many automatic functions ...have been developed to facilitate work in the control room. The hardware is permanently monitored, and around 1200 counters, with considerable built-in redundancy, are read at regular intervals (at least once per minute). This provides relevant physics information and also verifies the consistency of the hardware operation. In order to compensate for seasonal drift, the CORDE module has been installed, which allows the LHC clock to be delayed in steps of 10 ps. This paper describes the current status of the ALICE trigger system after experience with p-p and Pb-Pb runs, the new firmware developments and the appropriate software for this electronics.
The charged particle multiplicity is measured for inelastic and non-single-diffractive proton-proton collisions at collision energies of 900 GeV, 2760 GeV and 7000 GeV. The data analysed corresponds ...to an integrated luminosity of 0.152 \(\pm\) 0.003 pb\(^{-1}\), 1.29 \(\pm\) 0.07 pb\(^{-1}\) and 2.02 \(\pm\) 0.12 pb\(^{-1}\) for each respective collision energy. The average transverse momentum per event as a function of charged multiplicity, for tracks with transverse momentum above 150 MeV/c and 500 MeV/c, is measured for inelastic proton-proton collisions. Two methods of deconvolution were studied, and an iterative method was used to correct the multiplicity distributions. The effect of pileup on multiplicity measurements was modelled using a toy Monte Carlo. The results presented extend the previous measurements made by ALICE to more than ten times the average charged multiplicity, and are compared to results from other experiments at similar energies, and to the Monte Carlo generators Phojet and the Perugia-0 tune of Pythia. The pseudorapidity density is estimated from the multiplicity distributions, and found to agree with other experimental results. The Phojet generator reproduces well the 900 GeV multiplicity distribution, but otherwise it and Pythia both underestimate the probability of higher multiplicities. The Pythia generator reproduces well the average transverse momentum distribution for tracks above 500 MeV/c, and overestimates the lower momentum distribution, while Phojet tends to underestimate the distribution for both momentum thresholds. Evidence of the violation of KNO scaling is shown for non-single-diffractive events in a pseudorapidity interval of \(\pm\)1, but not in \(\pm\)0.5.
The charged particle multiplicity is measured for inelastic and non-single-diffractive proton-proton collisions at collision energies of 900 GeV, 2760 GeV and 7000 GeV. The data analysed corresponds ...to an integrated luminosity of 0.152 \(\pm\) 0.003 pb\({-1}\), 1.29 \(\pm\) 0.07 pb\({-1}\) and 2.02 \(\pm\) 0.12 pb\({-1}\) for each respective collision energy. The average transverse momentum per event as a function of charged multiplicity, for tracks with transverse momentum above 150 MeV/c and 500 MeV/c, is measured for inelastic proton-proton collisions. Two methods of deconvolution were studied, and an iterative method was used to correct the multiplicity distributions. The effect of pileup on multiplicity measurements was modelled using a toy Monte Carlo. The results presented extend the previous measurements made by ALICE to more than ten times the average charged multiplicity, and are compared to results from other experiments at similar energies, and to the Monte Carlo generators Phojet and the Perugia-0 tune of Pythia. The pseudorapidity density is estimated from the multiplicity distributions, and found to agree with other experimental results. The Phojet generator reproduces well the 900 GeV multiplicity distribution, but otherwise it and Pythia both underestimate the probability of higher multiplicities. The Pythia generator reproduces well the average transverse momentum distribution for tracks above 500 MeV/c, and overestimates the lower momentum distribution, while Phojet tends to underestimate the distribution for both momentum thresholds. Evidence of the violation of KNO scaling is shown for non-single-diffractive events in a pseudorapidity interval of \(\pm\)1, but not in \(\pm\)0.5.
The charged particle multiplicity is measured for inelastic and non-single-diffractive proton-proton collisions at collision energies of 900 GeV, 2760 GeV and 7000 GeV. The data analysed corresponds ...to an integrated luminosity of 0.152 \(\pm\) 0.003 pb\(^{-1}\), 1.29 \(\pm\) 0.07 pb\(^{-1}\) and 2.02 \(\pm\) 0.12 pb\(^{-1}\) for each respective collision energy. The average transverse momentum per event as a function of charged multiplicity, for tracks with transverse momentum above 150 MeV/c and 500 MeV/c, is measured for inelastic proton-proton collisions. Two methods of deconvolution were studied, and an iterative method was used to correct the multiplicity distributions. The effect of pileup on multiplicity measurements was modelled using a toy Monte Carlo. The results presented extend the previous measurements made by ALICE to more than ten times the average charged multiplicity, and are compared to results from other experiments at similar energies, and to the Monte Carlo generators Phojet and the Perugia-0 tune of Pythia. The pseudorapidity density is estimated from the multiplicity distributions, and found to agree with other experimental results. The Phojet generator reproduces well the 900 GeV multiplicity distribution, but otherwise it and Pythia both underestimate the probability of higher multiplicities. The Pythia generator reproduces well the average transverse momentum distribution for tracks above 500 MeV/c, and overestimates the lower momentum distribution, while Phojet tends to underestimate the distribution for both momentum thresholds. Evidence of the violation of KNO scaling is shown for non-single-diffractive events in a pseudorapidity interval of \(\pm\)1, but not in \(\pm\)0.5.
