Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2006
We have developed a high-efficiency pulsed slow positron beam for experiments with orthopositroni... more We have developed a high-efficiency pulsed slow positron beam for experiments with orthopositronium in vacuum. The new pulsing scheme is based on a double-gap coaxial buncher powered by an RF pulse of appropriate shape. The modulation of the positron velocity in the two gaps is used to adjust their time-of-flight to a target. This pulsing scheme allows to minimize non-linear aberrations in the bunching process and to efficiently compress positron pulses with an initial pulse duration ranging from ∼ 300 to 50 ns into bunches of 2.3 to 0.4 ns width, respectively, with a repetition period of 1 µs. The compression ratio achieved is ≃ 100, which is a factor 5 better than has been previously obtained with slow positron beams based on a single buncher. Requirements on the degree, to which the moderated positrons should be mono-energetic and on the precision of the waveform generation are presented. Possible applications of the new pulsed positron beam for measurements of thin films are discussed.
Journal of Polymer Science Part B: Polymer Physics, 2010
Copolymers of propylene and 1-octadecene synthesized by a metallocene catalyst were characterized... more Copolymers of propylene and 1-octadecene synthesized by a metallocene catalyst were characterized by PALS, WAXD, DSC, and density measurements. The change in the sizes and the number density of free-volume holes as a function of the 1-octadecene content were compared to the master laws published for copolymers of propylene with a-olefins of shorter lengths. It was found that the samples were separated into two groups. The first set of samples obeyed the master laws while the second group deviated. This behavior was explained by the difference in the copolymer structure. The WAXD analysis confirmed the separation as well. The deviation was explained as due to the mesomorphic crystalline structure of the second group of samples, in contrast to the monoclinic one for the first group, which was a result of the relatively fast cooling from the molten state and from the high comonomer molar content. V C 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48:
The results of a new search for positronium decays into invisible final states are reported. Conv... more The results of a new search for positronium decays into invisible final states are reported. Convincing detection of this decay mode would be a strong evidence for new physics beyond the standard model (SM): for example, the existence of extra-dimensions, of milli-charged particles, of new light gauge bosons or of mirror particles. Mirror matter could be a relevant dark matter candidate. In this paper the setup and the results of a new experiment are presented. In a collected sample of about (6.31{+-}0.28)x10 orthopositronium decays, no evidence for invisible decays in an energy [0,80] keV was found and an upper limit on the branching ratio of orthopositronium o-Psinvisible could be set: Br(o-Psinvisible)<4.2x10(90%C.L.) Our results provide a limit on the photon mirror-photon mixing strength {<=}1.55x10(90%C.L.) and rule out particles lighter than the electron mass with a fraction Q{<=}3.4x10 of the electron charge. Furthermore, upper limits on the branching ratios for the ...
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2007
A symmetric positron annihilation lifetime (PAL) spectrometer using a charge-to-digital converter... more A symmetric positron annihilation lifetime (PAL) spectrometer using a charge-to-digital converters was designed. It is based on a coincidence circuit for the trigger and recording of the timing and the charge of the pulses of two scintillation detectors. The off-line data processing allows a detailed study of the spectrometer performance in function of the width of the digital charge discriminator windows for acceptance of the pulses as starts and stops. Some technical problems when working with BaF 2 scintillators were solved. The parasitic effect of the pileup and backscattered c-rays on the PAL spectrum is discussed.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2006
We have developed a high-efficiency pulsed slow positron beam for experiments with orthopositroni... more We have developed a high-efficiency pulsed slow positron beam for experiments with orthopositronium in vacuum. The new pulsing scheme is based on a double-gap coaxial buncher powered by an RF pulse of appropriate shape. The modulation of the positron velocity in the two gaps is used to adjust their time-of-flight to a target. This pulsing scheme allows to minimize non-linear aberrations in the bunching process and to efficiently compress positron pulses with an initial pulse duration ranging from ∼ 300 to 50 ns into bunches of 2.3 to 0.4 ns width, respectively, with a repetition period of 1 µs. The compression ratio achieved is ≃ 100, which is a factor 5 better than has been previously obtained with slow positron beams based on a single buncher. Requirements on the degree, to which the moderated positrons should be mono-energetic and on the precision of the waveform generation are presented. Possible applications of the new pulsed positron beam for measurements of thin films are discussed.
ABSTRACT The alignment system for the muon spectrometer of the CMS detector comprises three indep... more ABSTRACT The alignment system for the muon spectrometer of the CMS detector comprises three independent subsystems of optical and analog position sensors. It aligns muon chambers with respect to each other and to the central silicon tracker. System commissioning at full magnetic field began in 2008 during an extended cosmic ray run. The system succeeded in tracking muon detector movements of up to 18 mm and rotations of several milliradians under magnetic forces. Depending on coordinate and subsystem, the system achieved chamber alignment precisions of 140-350 microns and 30-200 microradians, close to the precision requirements of the experiment. Systematic errors on absolute positions are estimated to be 340-590 microns based on comparisons with independent photogrammetry measurements.
Please be patient while the object screen loads. Changez de vue : Choisir un site… UCL FUNDP FUSL... more Please be patient while the object screen loads. Changez de vue : Choisir un site… UCL FUNDP FUSL FUCaM. ...
Chatrchyan, S and Khachatryan, V and Sirunyan, AM and Adam, W and Arnold, B and Bergauer, H and B... more Chatrchyan, S and Khachatryan, V and Sirunyan, AM and Adam, W and Arnold, B and Bergauer, H and Bergauer, T and Dragicevic, M and Eichberger, M and Ero, J and Friedl, M and Fruhwirth, R and Ghete, VM and Hammer, J and Hansel, S and Hoch, M and ...
ABSTRACT The CMS Collaboration conducted a month-long data taking exercise, the Cosmic Run At Fou... more ABSTRACT The CMS Collaboration conducted a month-long data taking exercise, the Cosmic Run At Four Tesla, during October-November 2008, with the goal of commissioning the experiment for extended operation. With all installed detector systems participating, CMS recorded 270 million cosmic ray events with the solenoid at a magnetic field strength of 3.8 T. This paper describes the data flow from the detector through the various online and offline computing systems, as well as the workflows used for recording the data, for aligning and calibrating the detector, and for analysis of the data.
95 , T. Signal 95 , J.C. Williams 95 , M. Ahmad 96 , I. Ahmed 96 , M.I. Asghar 96 , H.R. Hoorani ... more 95 , T. Signal 95 , J.C. Williams 95 , M. Ahmad 96 , I. Ahmed 96 , M.I. Asghar 96 , H.R. Hoorani 96 , W.A. Khan 96 , T. Khurshid 96 , S. Qazi 96 , M. Cwiok 97 , W. Dominik 97 , K. Doroba 97 , M. Konecki 97 , J. Krolikowski 97 , T. Frueboes 98 , R. Gokieli 98 , M. Górski 98 , M. Kazana 98 , K. Nawrocki 98 , M. Szleper 98 , G. Wrochna 98 , P. Zalewski 98 , N. Almeida 99 , A. David 99 , P. Faccioli 99 , P.G. Ferreira Parracho 99 , M. Gallinaro 99 , P. Martins 99 , G. Mini 99 , P. Musella 99 , A. Nayak 99 , L. Raposo 99 , P.Q. Ribeiro 99 , J. Seixas 99 , P. Silva 99 ,
... means are consistent with the muon minimum ionizing signals measured for segments of the calo... more ... means are consistent with the muon minimum ionizing signals measured for segments of the calorimeters in test beams [4, 6], without magnetic field, for a wide momen-tum range after taking into account magnetic field effects, correcting the signal for the muon path length and ...
The top-antitop quark (tt) production cross section is measured in proton-proton collisions at √ ... more The top-antitop quark (tt) production cross section is measured in proton-proton collisions at √ s = 8 TeV with the CMS experiment at the LHC, using a data sample corresponding to an integrated luminosity of 5.3 fb −1 . The measurement is performed by analysing events with a pair of electrons or muons, or one electron and one muon, and at least two jets, one of which is identified as originating from hadronisation of a bottom quark. The measured cross section is 239 ± 2 (stat.) ± 11 (syst.) ± 6 (lum.) pb, for an assumed top-quark mass of 172.5 GeV, in agreement with the prediction of the standard model.
A new measurement of the inclusive production cross section for pp → tt is performed at a center-... more A new measurement of the inclusive production cross section for pp → tt is performed at a center-of-mass energy of 7 TeV using data collected by the CMS experiment at the LHC. The analysis uses a data sample corresponding to an integrated luminosity of 36 pb −1 , and is based on the final state with one isolated, high transverse momentum muon or electron, missing transverse energy, and hadronic jets. The tt content of the selected events is enhanced by requiring the presence of at least one jet consistent with b-quark hadronization. The measured cross section is 150 ± 9 (stat.) ± 17 (syst.) ± 6 (lumi.) pb and is in agreement with higher-order QCD calculations. The combination of this measurement with a previous CMS result based on dileptons gives 154 ± 17 (stat. + syst.) ± 6 (lumi.) pb.
A search for pair-produced heavy vector-like charge-2/3 quarks, T, in pp collisions at a center-o... more A search for pair-produced heavy vector-like charge-2/3 quarks, T, in pp collisions at a center-of-mass energy of 7 TeV, is performed with the CMS detector at the LHC. Events consistent with the flavor-changing-neutral-current decay of a T quark to a top quark and a Z boson are selected by requiring two leptons from the Z-boson decay, as well as an additional isolated charged lepton. In a data sample corresponding to an integrated luminosity of 1.14 fb −1 , the number of observed events is found to be consistent with the standard model background prediction. Assuming a branching fraction of 100% for the decay T → tZ, a T quark with a mass less than 475 GeV/c 2 is excluded at the 95% confidence level.
Page 1. EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH (CERN) CERN-PH-EP/2011-066 2011/06/16 CMS-TOP-... more Page 1. EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH (CERN) CERN-PH-EP/2011-066 2011/06/16 CMS-TOP-10-008 Measurement of the t-channel single top quark production cross section in pp collisions at √ s = 7 TeV The CMS Collaboration ∗ Abstract ...
Measurements of the jet energy calibration and transverse momentum resolution in CMS are presente... more Measurements of the jet energy calibration and transverse momentum resolution in CMS are presented, performed with a data sample collected in proton-proton collisions at a centre-of-mass energy of 7 TeV, corresponding to an integrated luminosity of 36 pb −1 . The transverse momentum balance in dijet and γ/Z+jets events is used to measure the jet energy response in the CMS detector, as well as the transverse momentum resolution. The results are presented for three different methods to reconstruct jets: a calorimeter-based approach, the "Jet-Plus-Track" approach, which improves the measurement of calorimeter jets by exploiting the associated tracks, and the "Particle Flow" approach, which attempts to reconstruct individually each particle in the event, prior to the jet clustering, based on information from all relevant subdetectors.
... the endcaps. A similar formula is used for the τeτµ final state but with the isolation quanti... more ... the endcaps. A similar formula is used for the τeτµ final state but with the isolation quantities based directly on tracker and calorimeter information, calculated in a cone of AR = 0.3. In this case, it is required that Irel < 0.15 for muons and Irel < 0.1 for electrons. ...
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2006
We have developed a high-efficiency pulsed slow positron beam for experiments with orthopositroni... more We have developed a high-efficiency pulsed slow positron beam for experiments with orthopositronium in vacuum. The new pulsing scheme is based on a double-gap coaxial buncher powered by an RF pulse of appropriate shape. The modulation of the positron velocity in the two gaps is used to adjust their time-of-flight to a target. This pulsing scheme allows to minimize non-linear aberrations in the bunching process and to efficiently compress positron pulses with an initial pulse duration ranging from ∼ 300 to 50 ns into bunches of 2.3 to 0.4 ns width, respectively, with a repetition period of 1 µs. The compression ratio achieved is ≃ 100, which is a factor 5 better than has been previously obtained with slow positron beams based on a single buncher. Requirements on the degree, to which the moderated positrons should be mono-energetic and on the precision of the waveform generation are presented. Possible applications of the new pulsed positron beam for measurements of thin films are discussed.
Journal of Polymer Science Part B: Polymer Physics, 2010
Copolymers of propylene and 1-octadecene synthesized by a metallocene catalyst were characterized... more Copolymers of propylene and 1-octadecene synthesized by a metallocene catalyst were characterized by PALS, WAXD, DSC, and density measurements. The change in the sizes and the number density of free-volume holes as a function of the 1-octadecene content were compared to the master laws published for copolymers of propylene with a-olefins of shorter lengths. It was found that the samples were separated into two groups. The first set of samples obeyed the master laws while the second group deviated. This behavior was explained by the difference in the copolymer structure. The WAXD analysis confirmed the separation as well. The deviation was explained as due to the mesomorphic crystalline structure of the second group of samples, in contrast to the monoclinic one for the first group, which was a result of the relatively fast cooling from the molten state and from the high comonomer molar content. V C 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48:
The results of a new search for positronium decays into invisible final states are reported. Conv... more The results of a new search for positronium decays into invisible final states are reported. Convincing detection of this decay mode would be a strong evidence for new physics beyond the standard model (SM): for example, the existence of extra-dimensions, of milli-charged particles, of new light gauge bosons or of mirror particles. Mirror matter could be a relevant dark matter candidate. In this paper the setup and the results of a new experiment are presented. In a collected sample of about (6.31{+-}0.28)x10 orthopositronium decays, no evidence for invisible decays in an energy [0,80] keV was found and an upper limit on the branching ratio of orthopositronium o-Psinvisible could be set: Br(o-Psinvisible)<4.2x10(90%C.L.) Our results provide a limit on the photon mirror-photon mixing strength {<=}1.55x10(90%C.L.) and rule out particles lighter than the electron mass with a fraction Q{<=}3.4x10 of the electron charge. Furthermore, upper limits on the branching ratios for the ...
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2007
A symmetric positron annihilation lifetime (PAL) spectrometer using a charge-to-digital converter... more A symmetric positron annihilation lifetime (PAL) spectrometer using a charge-to-digital converters was designed. It is based on a coincidence circuit for the trigger and recording of the timing and the charge of the pulses of two scintillation detectors. The off-line data processing allows a detailed study of the spectrometer performance in function of the width of the digital charge discriminator windows for acceptance of the pulses as starts and stops. Some technical problems when working with BaF 2 scintillators were solved. The parasitic effect of the pileup and backscattered c-rays on the PAL spectrum is discussed.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2006
We have developed a high-efficiency pulsed slow positron beam for experiments with orthopositroni... more We have developed a high-efficiency pulsed slow positron beam for experiments with orthopositronium in vacuum. The new pulsing scheme is based on a double-gap coaxial buncher powered by an RF pulse of appropriate shape. The modulation of the positron velocity in the two gaps is used to adjust their time-of-flight to a target. This pulsing scheme allows to minimize non-linear aberrations in the bunching process and to efficiently compress positron pulses with an initial pulse duration ranging from ∼ 300 to 50 ns into bunches of 2.3 to 0.4 ns width, respectively, with a repetition period of 1 µs. The compression ratio achieved is ≃ 100, which is a factor 5 better than has been previously obtained with slow positron beams based on a single buncher. Requirements on the degree, to which the moderated positrons should be mono-energetic and on the precision of the waveform generation are presented. Possible applications of the new pulsed positron beam for measurements of thin films are discussed.
ABSTRACT The alignment system for the muon spectrometer of the CMS detector comprises three indep... more ABSTRACT The alignment system for the muon spectrometer of the CMS detector comprises three independent subsystems of optical and analog position sensors. It aligns muon chambers with respect to each other and to the central silicon tracker. System commissioning at full magnetic field began in 2008 during an extended cosmic ray run. The system succeeded in tracking muon detector movements of up to 18 mm and rotations of several milliradians under magnetic forces. Depending on coordinate and subsystem, the system achieved chamber alignment precisions of 140-350 microns and 30-200 microradians, close to the precision requirements of the experiment. Systematic errors on absolute positions are estimated to be 340-590 microns based on comparisons with independent photogrammetry measurements.
Please be patient while the object screen loads. Changez de vue : Choisir un site… UCL FUNDP FUSL... more Please be patient while the object screen loads. Changez de vue : Choisir un site… UCL FUNDP FUSL FUCaM. ...
Chatrchyan, S and Khachatryan, V and Sirunyan, AM and Adam, W and Arnold, B and Bergauer, H and B... more Chatrchyan, S and Khachatryan, V and Sirunyan, AM and Adam, W and Arnold, B and Bergauer, H and Bergauer, T and Dragicevic, M and Eichberger, M and Ero, J and Friedl, M and Fruhwirth, R and Ghete, VM and Hammer, J and Hansel, S and Hoch, M and ...
ABSTRACT The CMS Collaboration conducted a month-long data taking exercise, the Cosmic Run At Fou... more ABSTRACT The CMS Collaboration conducted a month-long data taking exercise, the Cosmic Run At Four Tesla, during October-November 2008, with the goal of commissioning the experiment for extended operation. With all installed detector systems participating, CMS recorded 270 million cosmic ray events with the solenoid at a magnetic field strength of 3.8 T. This paper describes the data flow from the detector through the various online and offline computing systems, as well as the workflows used for recording the data, for aligning and calibrating the detector, and for analysis of the data.
95 , T. Signal 95 , J.C. Williams 95 , M. Ahmad 96 , I. Ahmed 96 , M.I. Asghar 96 , H.R. Hoorani ... more 95 , T. Signal 95 , J.C. Williams 95 , M. Ahmad 96 , I. Ahmed 96 , M.I. Asghar 96 , H.R. Hoorani 96 , W.A. Khan 96 , T. Khurshid 96 , S. Qazi 96 , M. Cwiok 97 , W. Dominik 97 , K. Doroba 97 , M. Konecki 97 , J. Krolikowski 97 , T. Frueboes 98 , R. Gokieli 98 , M. Górski 98 , M. Kazana 98 , K. Nawrocki 98 , M. Szleper 98 , G. Wrochna 98 , P. Zalewski 98 , N. Almeida 99 , A. David 99 , P. Faccioli 99 , P.G. Ferreira Parracho 99 , M. Gallinaro 99 , P. Martins 99 , G. Mini 99 , P. Musella 99 , A. Nayak 99 , L. Raposo 99 , P.Q. Ribeiro 99 , J. Seixas 99 , P. Silva 99 ,
... means are consistent with the muon minimum ionizing signals measured for segments of the calo... more ... means are consistent with the muon minimum ionizing signals measured for segments of the calorimeters in test beams [4, 6], without magnetic field, for a wide momen-tum range after taking into account magnetic field effects, correcting the signal for the muon path length and ...
The top-antitop quark (tt) production cross section is measured in proton-proton collisions at √ ... more The top-antitop quark (tt) production cross section is measured in proton-proton collisions at √ s = 8 TeV with the CMS experiment at the LHC, using a data sample corresponding to an integrated luminosity of 5.3 fb −1 . The measurement is performed by analysing events with a pair of electrons or muons, or one electron and one muon, and at least two jets, one of which is identified as originating from hadronisation of a bottom quark. The measured cross section is 239 ± 2 (stat.) ± 11 (syst.) ± 6 (lum.) pb, for an assumed top-quark mass of 172.5 GeV, in agreement with the prediction of the standard model.
A new measurement of the inclusive production cross section for pp → tt is performed at a center-... more A new measurement of the inclusive production cross section for pp → tt is performed at a center-of-mass energy of 7 TeV using data collected by the CMS experiment at the LHC. The analysis uses a data sample corresponding to an integrated luminosity of 36 pb −1 , and is based on the final state with one isolated, high transverse momentum muon or electron, missing transverse energy, and hadronic jets. The tt content of the selected events is enhanced by requiring the presence of at least one jet consistent with b-quark hadronization. The measured cross section is 150 ± 9 (stat.) ± 17 (syst.) ± 6 (lumi.) pb and is in agreement with higher-order QCD calculations. The combination of this measurement with a previous CMS result based on dileptons gives 154 ± 17 (stat. + syst.) ± 6 (lumi.) pb.
A search for pair-produced heavy vector-like charge-2/3 quarks, T, in pp collisions at a center-o... more A search for pair-produced heavy vector-like charge-2/3 quarks, T, in pp collisions at a center-of-mass energy of 7 TeV, is performed with the CMS detector at the LHC. Events consistent with the flavor-changing-neutral-current decay of a T quark to a top quark and a Z boson are selected by requiring two leptons from the Z-boson decay, as well as an additional isolated charged lepton. In a data sample corresponding to an integrated luminosity of 1.14 fb −1 , the number of observed events is found to be consistent with the standard model background prediction. Assuming a branching fraction of 100% for the decay T → tZ, a T quark with a mass less than 475 GeV/c 2 is excluded at the 95% confidence level.
Page 1. EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH (CERN) CERN-PH-EP/2011-066 2011/06/16 CMS-TOP-... more Page 1. EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH (CERN) CERN-PH-EP/2011-066 2011/06/16 CMS-TOP-10-008 Measurement of the t-channel single top quark production cross section in pp collisions at √ s = 7 TeV The CMS Collaboration ∗ Abstract ...
Measurements of the jet energy calibration and transverse momentum resolution in CMS are presente... more Measurements of the jet energy calibration and transverse momentum resolution in CMS are presented, performed with a data sample collected in proton-proton collisions at a centre-of-mass energy of 7 TeV, corresponding to an integrated luminosity of 36 pb −1 . The transverse momentum balance in dijet and γ/Z+jets events is used to measure the jet energy response in the CMS detector, as well as the transverse momentum resolution. The results are presented for three different methods to reconstruct jets: a calorimeter-based approach, the "Jet-Plus-Track" approach, which improves the measurement of calorimeter jets by exploiting the associated tracks, and the "Particle Flow" approach, which attempts to reconstruct individually each particle in the event, prior to the jet clustering, based on information from all relevant subdetectors.
... the endcaps. A similar formula is used for the τeτµ final state but with the isolation quanti... more ... the endcaps. A similar formula is used for the τeτµ final state but with the isolation quantities based directly on tracker and calorimeter information, calculated in a cone of AR = 0.3. In this case, it is required that Irel < 0.15 for muons and Irel < 0.1 for electrons. ...
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Papers by Daniel Sillou