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E. Focardi

Università degli Studi di Firenze (University of Florence), Dipartimento di Fisica e Astronomia, Faculty Member

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Aix-Marseille University

Alexandra Vásquez

Universidad Catolica Santo Toribio de Mogrovejo

cecilia gomez hernandez

Alberto Ruiz-Jimeno

Centre National de la Recherche Scientifique / French National Centre for Scientific Research

jasmine jackson

University of Illinois at Chicago

Technische Universität München

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Papers by E. Focardi

Tau leptonic branching ratios

by F. Palla, T. Wang, and E. Focardi

Z. Phys. C, 1996

A sample of 62249 -pair events is selected from data taken with the ALEPH detector in 1991, 1992 ... more A sample of 62249 -pair events is selected from data taken with the ALEPH detector in 1991, 1992 and 1993. The measurement of the branching fractions for decays into electrons and muons is presented with emphasis on the study of systematic eects from selection, particle identication and decay classication. The results obtained are: B e = 1 7 : 790:12(stat)0:06(syst)(%) and B = 1 7 : 310:11(stat)0:05(syst)(%). Combined with the most recent ALEPH determination of the lifetime, these results provide a relative measurement of the leptonic couplings in the weak charged current for transverse W bosons: g =g e = 1 : 00020:0051 and g =g = 0 : 99430:0065.

Studies of azimuthal dihadron correlations in ultra-central PbPb collisions at=2.76 TeV

by E. Focardi and J. Gomez

Journal of High Energy Physics, 2014

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]

Studies of azimuthal dihadron correlations in ultra-central PbPb collisions at=2.76 TeV

Journal of High Energy Physics, 2014

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]

Searches for the neutral Higgs bosons of the MSSM in e+e− collisions at centre-of-mass energies of 181–184 GeV

Physics Letters B, 1998

The data collected by ALEPH at LEP at centre-of-mass energies ranging from 181 to 184 GeV, corres... more

Measurement of the W mass in e+e− collisions at 183 GeV

Physics Letters B, 1999

ICHEP98 Abstract 899 Parallel session 1 Plenary session 1 P R E L I M I N A R Y Measurement of th... more ICHEP98 Abstract 899 Parallel session 1 Plenary session 1 P R E L I M I N A R Y Measurement of the W Mass in e + e Collisions at 183 GeV The ALEPH Collaboration Abstract The mass of the W boson is obtained from reconstructed invariant mass distributions in W-pair events. The sample of W pairs is selected from 56.812 pb 1 collected with the ALEPH detector at a mean centre-of-mass energy of 182.655 GeV. The invariant mass distribution of reweighted Monte Carlo events are tted to the experimental distributions and the following W masses are obtained: WW ! q qq q m W = 80:410 0:178(stat:) 0:045(syst:) 0:056(BE=CR) GeV=c 2 ; WW ! eq q m W = 80:477 0:276(stat:) 0:037(syst:) GeV=c 2 ; WW ! q q m W = 80:307 0:300(stat:) 0:036(syst:) GeV=c 2 ; WW ! q q m W = 79:926 0:525(stat:) 0:085(syst:) GeV=c 2 : The statistical errors are derived from the single ts to the data in each of these channels. The combination of these four measurements gives: m W = 8 0 : 3740:130(stat:)0:041(syst:)0:028(BE=CR)0:022(LEP) GeV=c

The CMS silicon strip tracker

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1999

The CMS strip tracker is the first large scale tracker entirely based on silicon detectors techno... more The CMS strip tracker is the first large scale tracker entirely based on silicon detectors technology. It consists of 198 m 2 of detector sensitive area instrumenting the inner region of the experiment with a pseudo-rapidity coverage of |η| < 2.5. This instrument, together with a silicon pixel system, is expected to perform robust tracking and detailed vertex reconstruction while embedded in the LHC high radiation and high luminosity environment. The project is in a well advanced construction phase: the detector module production is completed, the integration of the single components into large subdetector units is underway and the full tracker commissioning is about to start. In this paper, after a description of the tracker layout, a detector modules production overview and a summary of the integration procedures for the inner barrel part of the tracker will be reported. a) Representing the CMS Tracker Collaboration

The CMS silicon tracker

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2000

This paper describes the Silicon microstrip Tracker of the CMS experiment at LHC. It consists of ... more This paper describes the Silicon microstrip Tracker of the CMS experiment at LHC. It consists of a barrel part with 5 layers and two endcaps with 10 disks each. About 10 000 single-sided equivalent modules have to be built, each one carrying two daisy-chained silicon detectors and their front-end electronics. Back-to-back modules are used to read-out the radial coordinate. The tracker will be operated in an environment kept at a temperature of ¹"!103C to minimize the Si sensors radiation damage. Heavily irradiated detectors will be safely operated due to the high-voltage capability of the sensors. Full-size mechanical prototypes have been built to check the system aspects before starting the construction.

Production of charmed mesons inZ decays

Zeitschrift für Physik C Particles and Fields, 1994

The effect of highly ionising particles on the CMS silicon strip tracker

by F. Palla, V. Ciulli, and E. Focardi

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2005

Inelastic nuclear collisions of hadrons incident on silicon sensors can generate secondary highly... more Inelastic nuclear collisions of hadrons incident on silicon sensors can generate secondary highly ionising particles (HIPs) and deposit as much energy within the sensor bulk as several hundred minimum ionising particles. The large signals generated by these 'HIP events' can momentarily saturate the APV25 front-end readout chip for the silicon strip tracker (SST) sub-detector of the compact muon solenoid (CMS) experiment, resulting in deadtime in the detector readout system. This paper presents studies of this phenomenon through simulation, laboratory measurements and dedicated beam tests. A proposed change to a front-end component to reduce the APV25 sensitivity to HIP events is also examined. The results are used to infer the expected effect on the performance of the CMS SST at the future large hadron collider. The induced inefficiencies are at the percent level and will have a negligible effect on the physics performance of the SST. r

Tau leptonic branching ratios

by F. Palla, T. Wang, and E. Focardi

Z. Phys. C, 1996

A sample of 62249 -pair events is selected from data taken with the ALEPH detector in 1991, 1992 ... more A sample of 62249 -pair events is selected from data taken with the ALEPH detector in 1991, 1992 and 1993. The measurement of the branching fractions for decays into electrons and muons is presented with emphasis on the study of systematic eects from selection, particle identication and decay classication. The results obtained are: B e = 1 7 : 790:12(stat)0:06(syst)(%) and B = 1 7 : 310:11(stat)0:05(syst)(%). Combined with the most recent ALEPH determination of the lifetime, these results provide a relative measurement of the leptonic couplings in the weak charged current for transverse W bosons: g =g e = 1 : 00020:0051 and g =g = 0 : 99430:0065.

Studies of azimuthal dihadron correlations in ultra-central PbPb collisions at=2.76 TeV

by E. Focardi and J. Gomez

Journal of High Energy Physics, 2014

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]

Studies of azimuthal dihadron correlations in ultra-central PbPb collisions at=2.76 TeV

Journal of High Energy Physics, 2014

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]

Searches for the neutral Higgs bosons of the MSSM in e+e− collisions at centre-of-mass energies of 181–184 GeV

Physics Letters B, 1998

The data collected by ALEPH at LEP at centre-of-mass energies ranging from 181 to 184 GeV, corres... more

Measurement of the W mass in e+e− collisions at 183 GeV

Physics Letters B, 1999

ICHEP98 Abstract 899 Parallel session 1 Plenary session 1 P R E L I M I N A R Y Measurement of th... more ICHEP98 Abstract 899 Parallel session 1 Plenary session 1 P R E L I M I N A R Y Measurement of the W Mass in e + e Collisions at 183 GeV The ALEPH Collaboration Abstract The mass of the W boson is obtained from reconstructed invariant mass distributions in W-pair events. The sample of W pairs is selected from 56.812 pb 1 collected with the ALEPH detector at a mean centre-of-mass energy of 182.655 GeV. The invariant mass distribution of reweighted Monte Carlo events are tted to the experimental distributions and the following W masses are obtained: WW ! q qq q m W = 80:410 0:178(stat:) 0:045(syst:) 0:056(BE=CR) GeV=c 2 ; WW ! eq q m W = 80:477 0:276(stat:) 0:037(syst:) GeV=c 2 ; WW ! q q m W = 80:307 0:300(stat:) 0:036(syst:) GeV=c 2 ; WW ! q q m W = 79:926 0:525(stat:) 0:085(syst:) GeV=c 2 : The statistical errors are derived from the single ts to the data in each of these channels. The combination of these four measurements gives: m W = 8 0 : 3740:130(stat:)0:041(syst:)0:028(BE=CR)0:022(LEP) GeV=c

The CMS silicon strip tracker

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1999

The CMS strip tracker is the first large scale tracker entirely based on silicon detectors techno... more The CMS strip tracker is the first large scale tracker entirely based on silicon detectors technology. It consists of 198 m 2 of detector sensitive area instrumenting the inner region of the experiment with a pseudo-rapidity coverage of |η| < 2.5. This instrument, together with a silicon pixel system, is expected to perform robust tracking and detailed vertex reconstruction while embedded in the LHC high radiation and high luminosity environment. The project is in a well advanced construction phase: the detector module production is completed, the integration of the single components into large subdetector units is underway and the full tracker commissioning is about to start. In this paper, after a description of the tracker layout, a detector modules production overview and a summary of the integration procedures for the inner barrel part of the tracker will be reported. a) Representing the CMS Tracker Collaboration

The CMS silicon tracker

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2000

This paper describes the Silicon microstrip Tracker of the CMS experiment at LHC. It consists of ... more This paper describes the Silicon microstrip Tracker of the CMS experiment at LHC. It consists of a barrel part with 5 layers and two endcaps with 10 disks each. About 10 000 single-sided equivalent modules have to be built, each one carrying two daisy-chained silicon detectors and their front-end electronics. Back-to-back modules are used to read-out the radial coordinate. The tracker will be operated in an environment kept at a temperature of ¹"!103C to minimize the Si sensors radiation damage. Heavily irradiated detectors will be safely operated due to the high-voltage capability of the sensors. Full-size mechanical prototypes have been built to check the system aspects before starting the construction.

Production of charmed mesons inZ decays

Zeitschrift für Physik C Particles and Fields, 1994

The effect of highly ionising particles on the CMS silicon strip tracker

by F. Palla, V. Ciulli, and E. Focardi

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2005

Inelastic nuclear collisions of hadrons incident on silicon sensors can generate secondary highly... more Inelastic nuclear collisions of hadrons incident on silicon sensors can generate secondary highly ionising particles (HIPs) and deposit as much energy within the sensor bulk as several hundred minimum ionising particles. The large signals generated by these 'HIP events' can momentarily saturate the APV25 front-end readout chip for the silicon strip tracker (SST) sub-detector of the compact muon solenoid (CMS) experiment, resulting in deadtime in the detector readout system. This paper presents studies of this phenomenon through simulation, laboratory measurements and dedicated beam tests. A proposed change to a front-end component to reduce the APV25 sensitivity to HIP events is also examined. The results are used to infer the expected effect on the performance of the CMS SST at the future large hadron collider. The induced inefficiencies are at the percent level and will have a negligible effect on the physics performance of the SST. r