122383524
DIELECTRON SPECTROSCOPY IN COLD NUCLEAR MATTER
We report recent data on e+e- pair emission in proton nucleus collisions at energies slightly above the light vector meson production threshold. Invariant mass distributions for the p+Nb system at Ekin = 3.5 GeV/c2 show a clear ρ/ω signal and are compared to data from elementary p+p reactions. We observe a constant π0/ω yield ratio for both systems.
119194439
Correlations and fluctuations studied with ALICE
The measurement of particle correlations and event-by-event fluctuations of physical observables allows to study a large variety of properties of the matter produced in ultra relativistic heavy-ion collisions. We will present results for two-particle correlations, mean transverse momentum fluctuations, and net charge fluctuations in Pb-Pb collisions at = 2.76 TeV.
16249880
Performances of 4-gap timing RPCs for relativistic ions in the range Z=1-6
Results from 4-gap Resistive Plate Chambers (RPCs) under irradiation by fully stripped relativistic ions (normalized momentum p/M = γβ = 2.7, atomic charge Z = 1−6) are presented. A time resolution of 80 ps at high efficiency has been obtained by using standard `off the shelf' 4-gap timing RPCs from the new HADES time-of-flight wall. The resolution worsened to 100 ps for ~ 1 kHz/cm2 proton flux and for ~ 100 Hz/cm2 carbon flux. The chambers were operated at a field E = 100 kV/cm, showing a high stability during the measurements. It seems to exist ample room for improvement, in particular regarding the time resolution.
124310260
Baryon and antibaryon production in lead-lead collisions at 158 A GeV/c
Abstract We report on baryon and antibaryon as well as K + and K − production cross sections measured in lead-lead collisions at 158 GeV /c per nucleon. The presented data were taken at zero degree production angle with a minimum bias trigger. The measurements covered a wide range of rapidity 1.4 y
124388402
Strangelet search and particle production studies in Pb + Pb collisions at 158-A-GeV/c at CERN SPS
We searched for long-lived strange quark matter particles, so-calledstrangelets, and studied particle and antiparticle production in Pb+Pb collisions at 158 GeV/c per nucleon at zero degree production angle. We give upper limits for the production of strangelets covering a mass to charge ratio up to 120 GeV/c 2 and lifetimest lab>1.2 μs and plot invariant differential production cross sections as a function of rapidity for a variety of particles.
121913281
The NA52 strangelet and particle search in Pb + Pb collisions at 158-A-GeV/c
The NA52 experiment searched for long-lived charged strangelets in 158 A GeV/c Pb+Pb collisions at CERN SPS. We collected 1013 Pb+Pb interactions looking for negatively charged strangelets and 3 × 1011 Pb+Pb interactions for positively charged ones. No evidence for the production of strangelets has been observed. The upper strangelet production limits are discussed. Besides the strangelet searches NA52 was able to identify particles and anti-particles over a wide range in rapidity. Results of the invariant differential particle production cross sections including fragments up to carbon and 5 are presented.
118320839
Gluon-Induced Weak Boson Fusion
The gluon-gluon induced terms for Higgs production through weak boson fusion (WBF) are computed. Formally, these are of next-to-next-to-leading order in the strong coupling constant. This is the lowest order at which nonzero color exchange occurs between the scattering quarks, leading to a color field and thus additional hadronic activity between the outgoing jets. Using a minimal set of cuts, the numerical impact of these terms is at the percent level with respect to the next-to-leading order rate for weak boson fusion. Applying the so-called WBF cuts leads to an even stronger suppression, so that we do not expect a significant deterioration of the WBF signal by these color exchange effects.
123173797
Calibration, alignment and tracking performance of the CMS silicon strip tracker
Abstract After its installation in the CMS experiment, the CMS silicon tracker has been commissioned, calibrated and aligned based on several million reconstructed tracks, recorded during extended cosmic ray data-taking in 2008 and 2009. The collision data at 900 GeV and 2.36 TeV which were recorded by the CMS experiment in December 2009 allowed to repeat the calibration measurements and derive compatible results. Calibration results are shown for the silicon strip detector only, whereas alignment and tracking performance are given for the complete CMS tracker, including the silicon pixel system.