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]
Nuclear Instruments and Methods in Physics Research A, 2014
AMS-02 is a high energy particle detector deployed in May 19, 2011 on board of the International ... more AMS-02 is a high energy particle detector deployed in May 19, 2011 on board of the International Space Station (ISS) where it is expected to be in operation for the ISS lifetime of at least a decade. The main goal of AMS-02 is the detection of cosmic rays and gammas from the GeV to the TeV energy region to search for anti-matter, dark matter and understanding the origin of the cosmic rays. The AMS-02 time of flight (TOF) detector provides the trigger to experiment and allows precise measurements of the cosmic rays velocity and charge magnitude from hydrogen to iron and above. With the data set acquired during the first two and a half years of operation in space, a precise time-dependent calibration for time, velocity and charge measured by the TOF had been developed. The TOF calibration methods are described and the AMS-02 TOF performance in space is presented.
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]
Nuclear Instruments and Methods in Physics Research A, 2014
AMS-02 is a high energy particle detector deployed in May 19, 2011 on board of the International ... more AMS-02 is a high energy particle detector deployed in May 19, 2011 on board of the International Space Station (ISS) where it is expected to be in operation for the ISS lifetime of at least a decade. The main goal of AMS-02 is the detection of cosmic rays and gammas from the GeV to the TeV energy region to search for anti-matter, dark matter and understanding the origin of the cosmic rays. The AMS-02 time of flight (TOF) detector provides the trigger to experiment and allows precise measurements of the cosmic rays velocity and charge magnitude from hydrogen to iron and above. With the data set acquired during the first two and a half years of operation in space, a precise time-dependent calibration for time, velocity and charge measured by the TOF had been developed. The TOF calibration methods are described and the AMS-02 TOF performance in space is presented.
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