1,517 research outputs found
Amorphous Carbon Coatings at Cryogenic Temperatures with LHC Type Beams: First Results with the COLDEX Experiment
No full textExtrapolations of electron cloud data from the Large Hadron Collider (LHC) Run 1 to the High Luminosity upgrade (HL-LHC) beam parameters predict an intolerable increase of heat load on the beam screens of the inner triplets. Amorphous carbon (a-C) coating of the beam screen surface is proposed to reduce electron cloud production, thereby minimising its dissipated power. To validate this solution, the COLDEX experiment has been re-commissioned. Such equipment mimics the performance of the LHC cold bore and beam screen cryogenic vacuum system in presence of LHC beams in the Super Proton Synchrotron (SPS). The main objective of the study is the performance evaluation of a-C coatings while operating the beam screen in the 10 to 60 K temperature range and cold bore below 3 K. This paper reviews the status of COLDEX and the results obtained during its first experimental runs
The SU(3)-invariant sector of new maximal supergravity
No full textWe investigate the SU(3)-invariant sector of the one-parameter family of SO(8) gauged maximal supergravities that has been recently discovered. To this end, we construct the N = 2 truncation of this theory and analyse its full vacuum structure. The number of critical point is doubled and includes new N = 0 and N = 1 branches. We numerically exhibit the parameter dependence of the location and cosmological constant of all extrema. Moreover, we provide their analytic expressions for cases of special interest. Finally, while the mass spectra are found to be parameter independent in most cases, we show that the novel non-supersymmetric branch with SU(3) invariance provides the first counterexample to this.
Measurement of NEG Coating Performance Variation in the LHC after the First Long Shutdown
No full textDuring the Long Shutdown 1 (LS1) of the Large Hadron Collider, 90% of the Non-Evaporable Getter (NEG) coated beam pipes in the Long Straight Sections (LSS) were vented to undertake the planned upgrade and consolidation programmes. After each intervention, an additional bake-out and NEG activation were performed to reach the vacuum requirements. An analysis of the coating performance variation after the additional activation cycle has been carried out by using ultimate pressure and pressure build-up measurements. In addition, laboratory measurements have been carried out to mimic the LHC coated beam pipe behaviour. The experimental data have been compared with calculation obtained by Molflow+
Measurement of the production cross section of jets in association with a Z boson in pp collisions at √s=7 TeV with the ATLAS detector
No full textMeasurements of the production of jets of particles in association with a Z boson in pp collisions at s√=7 TeV are presented, using data corresponding to an integrated luminosity of 4.6 fb−1 collected by the ATLAS experiment at the Large Hadron Collider. Inclusive and differential jet cross sections in Z events, with Z decaying into electron or muon pairs, are measured for jets with transverse momentum p T > 30 GeV and rapidity |y| < 4.4. The results are compared to next-to-leading-order perturbative QCD calculations, and to predictions from different Monte Carlo generators based on leading-order and next-to-leading-order matrix elements supplemented by parton showers
Measurement of the top quark mass with the template method in the t<span style="text-decoration: overline">t</span> →lepton+jets channel using ATLAS data
No full textContains fulltext :
103516.pdf (Publisher’s version ) (Open Access
Synchrotron radiation-induced desorption from a NEG-coated vacuum chamber [of ESRF beamline]
No full textWhen the whole inner surface of a vacuum chamber is coated with a non-evaporable getter film, very low static and dynamic pressures are expected after activation. In an accelerator environment this could result in a longer beam lifetime, in a lower risk of pressure bumps, and in a lower level of bremsstrahlung radiation due to the beam-gas interactions. To substantiate these favourable characteristics a Ti- Zr-V coated stainless-steel chamber has been tested on a dedicated beamline at the ESRF. It is shown that a large reduction of the synchrotron radiation-induced desorption occurs after activation. (10 refs)
Measurement of trilinear gauge boson couplings at LEP2
No full textThe preliminary results of charged trilinear gauge boson WWV, V identical to Z/ gamma coupling values presented in this paper were obtained by the four LEP2 experiments ALEPH, DELPHI, L3 and OPAL by analysing the data collected at LEP energies ranging from square root s=183 GeV to square root s=202 GeV. At these energies, significantly above the kinematic threshold for W/sup +/W/sup -/ boson pair production, each of the four experiments collected data equivalent to more than L~500 pb/sup -1/ of integrated luminosity. The estimation of trilinear gauge boson couplings based on this data provides an independent check of the gauge nature of the standard model. (20 refs)
ATLAS Results
No full textSlides of the talk to be given at the Miami 2012 conference, presenting an overview over all ATLAS physics results apart from Higgs boson searches
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