The results of searches for new physics in events with two same-sign isolated leptons, hadronic j... more The results of searches for new physics in events with two same-sign isolated leptons, hadronic jets, and missing transverse energy in the final state are presented. The searches use an integrated luminosity of 35 pb −1 of pp collision data at a centre-of-mass energy of 7 TeV collected by the CMS experiment at the LHC. The observed numbers of events agree with the standard model predictions, and no evidence for new physics is found. To facilitate the interpretation of our data in a broader range of new physics scenarios, information on our event selection, detector response, and efficiencies is provided.
Ensuring the radiation hardness of PbWO 4 crystals was one of the main priorities during the cons... more Ensuring the radiation hardness of PbWO 4 crystals was one of the main priorities during the construction of the electromagnetic calorimeter of the CMS experiment at CERN. The production on an industrial scale of radiation hard crystals and their certification over a period of several years represented a difficult challenge both for CMS and for the crystal suppliers. The present article reviews the related scientific and technological problems encountered.
Azimuthal dihadron correlations of charged particles have been measured in PbPb collisions at √ s... more Azimuthal dihadron correlations of charged particles have been measured in PbPb collisions at √ s NN = 2.76 TeV by the CMS collaboration, using data from the 2011 LHC heavy-ion run. The data set includes a sample of ultra-central (0-0.2% centrality) PbPb events collected using a trigger based on total transverse energy in the hadron forward calorimeters and the total multiplicity of pixel clusters in the silicon pixel tracker. A total of about 1.8 million ultra-central events were recorded, corresponding to an integrated luminosity of 120 µb −1 . The observed correlations in ultra-central PbPb events are expected to be particularly sensitive to initial-state fluctuations. The single-particle anisotropy Fourier harmonics, from v 2 to v 6 , are extracted as a function of particle transverse momentum. At higher transverse momentum, the v 2 harmonic becomes significantly smaller than the higher-order v n (n ≥ 3). The p T -averaged v 2 and v 3 are found to be equal within 2%, while higher-order v n decrease as n increases. The breakdown of factorization of dihadron correlations into single-particle azimuthal anisotropies is observed. This effect is found to be most prominent in the ultra-central PbPb collisions, where the initial-state fluctuations play a dominant role. A comparison of the factorization data to hydrodynamic predictions with event-byevent fluctuating initial conditions is also presented. Submitted to the Journal of High Energy Physics c 2013 CERN for the benefit of the CMS Collaboration. CC-BY-3.0 license arXiv:1312.1845v1 [nucl-ex]
The results of searches for new physics in events with two same-sign isolated leptons, hadronic j... more The results of searches for new physics in events with two same-sign isolated leptons, hadronic jets, and missing transverse energy in the final state are presented. The searches use an integrated luminosity of 35 pb −1 of pp collision data at a centre-of-mass energy of 7 TeV collected by the CMS experiment at the LHC. The observed numbers of events agree with the standard model predictions, and no evidence for new physics is found. To facilitate the interpretation of our data in a broader range of new physics scenarios, information on our event selection, detector response, and efficiencies is provided.
Ensuring the radiation hardness of PbWO 4 crystals was one of the main priorities during the cons... more Ensuring the radiation hardness of PbWO 4 crystals was one of the main priorities during the construction of the electromagnetic calorimeter of the CMS experiment at CERN. The production on an industrial scale of radiation hard crystals and their certification over a period of several years represented a difficult challenge both for CMS and for the crystal suppliers. The present article reviews the related scientific and technological problems encountered.
Azimuthal dihadron correlations of charged particles have been measured in PbPb collisions at √ s... more Azimuthal dihadron correlations of charged particles have been measured in PbPb collisions at √ s NN = 2.76 TeV by the CMS collaboration, using data from the 2011 LHC heavy-ion run. The data set includes a sample of ultra-central (0-0.2% centrality) PbPb events collected using a trigger based on total transverse energy in the hadron forward calorimeters and the total multiplicity of pixel clusters in the silicon pixel tracker. A total of about 1.8 million ultra-central events were recorded, corresponding to an integrated luminosity of 120 µb −1 . The observed correlations in ultra-central PbPb events are expected to be particularly sensitive to initial-state fluctuations. The single-particle anisotropy Fourier harmonics, from v 2 to v 6 , are extracted as a function of particle transverse momentum. At higher transverse momentum, the v 2 harmonic becomes significantly smaller than the higher-order v n (n ≥ 3). The p T -averaged v 2 and v 3 are found to be equal within 2%, while higher-order v n decrease as n increases. The breakdown of factorization of dihadron correlations into single-particle azimuthal anisotropies is observed. This effect is found to be most prominent in the ultra-central PbPb collisions, where the initial-state fluctuations play a dominant role. A comparison of the factorization data to hydrodynamic predictions with event-byevent fluctuating initial conditions is also presented. Submitted to the Journal of High Energy Physics c 2013 CERN for the benefit of the CMS Collaboration. CC-BY-3.0 license arXiv:1312.1845v1 [nucl-ex]
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Papers by L. Dobrzynski