A new precise measurement of |V cb | and of the branching ratio BR(B 0 → D * + ℓ −ν ℓ) has been p... more A new precise measurement of |V cb | and of the branching ratio BR(B 0 → D * + ℓ −ν ℓ) has been performed using a sample of about 5000 semileptonic decaysB 0 → D * + ℓ −ν ℓ , selected by the DELPHI detector at LEP I by tagging the soft pion from D * + → D 0 π +. The results are: V cb = (39.0 ± 1.5 (stat.) +2.5 −2.6 (syst. exp.) ± 1.3 (syst. th.)) × 10 −3 BR(B 0 → D * + ℓ −ν ℓ) = (4.70 ± 0.13 (stat.) +0.36 −0.31 (syst. exp.))% The analytic dependences of the differential cross-section and of the Isgur Wise form factor as functions of the variable w = v B 0 • v D * have also been obtained by unfolding the experimental resolution.
A search for charginos nearly mass degenerate with the lightest neutralino is performed with the ... more A search for charginos nearly mass degenerate with the lightest neutralino is performed with the data collected by the ALEPH detector at LEP, at centre-ofmass energies between 189 and 209 GeV, corresponding to an integrated luminosity of 628 pb −1. The analysis is based on the detection of isolated and energetic initial state radiation photons, produced in association with chargino pairs whose decay products have little visible energy. The number of candidate events observed is in agreement with that expected from Standard Model background sources. These
A wide field space-based imaging telescope is necessary to fully exploit the technique of observi... more A wide field space-based imaging telescope is necessary to fully exploit the technique of observing dark matter via weak gravitational lensing. This first paper in a three part series outlines the survey strategies and relevant instrumental parameters for such a mission. As a concrete example of hardware design, we consider the proposed Supernova/Acceleration Probe (SNAP). Using SNAP engineering models, we quantify the major contributions to this telescope's Point Spread Function (PSF). These PSF contributions are relevant to any similar wide field space telescope. We further show that the PSF of SNAP or a similar telescope will be smaller than current ground-based PSFs, and more isotropic and stable over time than the PSF of the Hubble Space Telescope. We outline survey strategies for two different regimesa "wide" 300 square degree survey and a "deep" 15 square degree survey that will accomplish various weak lensing goals including statistical studies and dark matter mapping.
Space Telescopes and Instrumentation 2008: Optical, Infrared, and Millimeter, 2008
An integral field spectrograph concept has been developed for the SNAP/JDEM(SuperNova/Acceleratio... more An integral field spectrograph concept has been developed for the SNAP/JDEM(SuperNova/Acceleration Probe) experiment. This spectrograph will be optimized for faint supernovae and galaxies in a 3×6 arsec2 at low spectral resolution (R~100) through the wavelength range (0.35-1.7 mum). The integral field method is based on glass image slicer. A prototype of this instrument has been build to validate the concept
The recent proposal by Hawking and Turok for obtaining an open inflationary universe from singula... more The recent proposal by Hawking and Turok for obtaining an open inflationary universe from singular instantons makes use of low-energy effective Lagrangians describing gravity coupled to scalars and non-propagating antisymmetric tensors. In this paper we derive some exact results for Lagrangians of this type, obtained from spherical compactifications of M-theory and string theory. In the case of the S 7 compactification of M-theory, we give a detailed discussion of the cosmological solutions. We also show that the lower-dimensional Lagrangians admit domain-wall solutions, which preserve one half of the supersymmetry, and which approach AdS spacetimes near their horizons.
The lifetime of the B ° has been measured in a data sample of 889 000 hadronic events recorded wi... more The lifetime of the B ° has been measured in a data sample of 889 000 hadronic events recorded with the ALEPH detector at LEP. After background subtraction 30.8-4-6.9 events are attributed to the semileptonic decay of the Bs ° to a Ds and an opposite-sign lepton. A maximum-likelihood fit to the distribution of the proper times of these events 1 09+0"45 "4-0.04 ps. yields a Bs ° lifetime of zBs ....-0.35
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1996
DELPHI (DEtector with Lepton, Photon and Hadron Identification) is a detector for e+e-physics, de... more DELPHI (DEtector with Lepton, Photon and Hadron Identification) is a detector for e+e-physics, designed to provide high granularity over a 47r solid angle, allowing an effective particle identification. It has been operating at the LEP (Large Electron-Positron) collider at CERN since 1989. This article reviews its performance.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1997
We present a simulation of the signal delivered by minimum ionising particles crossing an MSGC. T... more We present a simulation of the signal delivered by minimum ionising particles crossing an MSGC. The parameters, adjusted to the experimental data, are reported for different gas mixtures. The simulation is then applied to the study of the bunch crossing identification at LHC. We present the performance of different pulse shapings and processing algorithms in the LHC environment.
The European Physical Journal C - Particles and Fields, 2003
Searches for resonantν production in e + e − collisions under the assumption that R-parity is not... more Searches for resonantν production in e + e − collisions under the assumption that R-parity is not conserved and that the dominant R-parity violating coupling is λ 121 or λ 131 used data recorded by DELPHI in 1997 to 2000 at centre-of-mass energies of 183 to 208 GeV. No deviation from the Standard Model was observed. Upper limits are given for the λ 121 and λ 131 couplings as a function of the sneutrino mass and total width. The limits are especially stringent for sneutrino masses equal to the centre-of-mass energies with the highest integrated luminosities recorded.
The data collected with the DELPHI detector at centre-of-mass energies between 130 and 172 GeV, d... more The data collected with the DELPHI detector at centre-of-mass energies between 130 and 172 GeV, during LEP operation in 1995 and 1996, have been used to determine the hadronic and leptonic cross-sections and leptonic forward{ backward asymmetries. In addition, the cross-section ratios and forward{ backward asymmetries for avour-tagged samples of light (uds), c and b quarks have been measured. The results are interpreted by performing S-matrix ts to these data and to the data collected previously at the energies near the Z 0 resonance peak (88-93 GeV). The results are also interpreted in terms of contact interactions, which parameterise physics beyond the Standard Model. Further interpretation of the data is made in terms of possible R-parity violating SUSY particles and of possible Z 0 bosons. No signicant deviations from the Standard Model expectations are found and limits are given for the various interpretations which are made of physics beyond the Standard Model.
The DELPHI experiment at LEP has measured the inclusive c harmless B hadron decay branching ratio... more The DELPHI experiment at LEP has measured the inclusive c harmless B hadron decay branching ratio, the B branching ratio into two c harmed particles, and the total number of charmed particles per B decay, using the hadronic Z data taken between 1992 and 1995. The results are extracted from a t to the b-tagging probability distribution based on the precise impact parameter measurements made using the microvertex detector. The inclusive c harmless B branching ratio, including B decays into hidden charm (c c), is measured to be 0:033 0:021. The B branching ratio into two o p e n c harmed particles is 0:136 0:042. The mean number of charmed particles per B decay (including hidden charm) is 1:147 0:041. After subtracting the B decay branching ratio into hidden charm, the charmless B branching ratio is found to be 0:007 0:021, compatible with the Standard Model expectation. Models that predict an additional contribution to the charmless B branching ratio of 0.037 or higher are excluded with at least 95% condence.
The Nearby Supernova Factory reports that spectra (range 320-1000 nm) of supernovae 2005gn and 20... more The Nearby Supernova Factory reports that spectra (range 320-1000 nm) of supernovae 2005gn and 2005hb (IAUC #8616), obtained October 18.6 UT with the Supernova Integral Field Spectrograph on the University of Hawaii 2.2-meter telescope, indicate that both supernovae are of Type II. SN2005gn is a Type IIn supernova at a redshift of z = 0.0397, with prominent H- alpha (FWHM 4000 km/s) and Ca II IR triplet emission.
From the data recorded with the DELPHI detector at LEP in the years 1991-1992, 46 497 events were... more From the data recorded with the DELPHI detector at LEP in the years 1991-1992, 46 497 events were selected having a high-momentum muon in hadron jets. A fit to the average electric charge sum of the jets recoiling against a b-quark jet tagged by a high-PT muon results in an average mixing parameter of~ = 0.1444-0.014(stat.)_+0100~(syst.).
We estimate systematic errors due to K-corrections in standard photometric analyses of high redsh... more We estimate systematic errors due to K-corrections in standard photometric analyses of high redshift Type Ia supernovae. Errors due to K-correction occur when the spectral template model underlying the lightcurve fitter poorly represents the actual supernova spectral energy distribution, meaning that the distance modulus cannot be recovered accurately. In order to quantify this effect, synthetic photometry is performed on artificially redshifted spectrophotometric data from 119 low-redshift supernovae from the Nearby Supernova Factory, and the resulting lightcurves are fit with a conventional lightcurve fitter. We measure the variation in the standardized magnitude that would be fit for a given supernova if located at a range of redshifts and observed with various filter sets corresponding to current and future supernova surveys. We find significant variation in the measurements of the same supernovae placed at different redshifts regardless of filters used, which causes dispersion greater than ∼ 0.05 mag for measurements of photometry using the Sloan-like filters and a bias that corresponds to a 0.03 shift in w when applied to an outside data set. To test the result of a shift in supernova population or environment at higher redshifts, we repeat our calculations with the addition of a reweighting of the supernovae as a function of redshift and find that this strongly affects the results and would have repercussions for cosmology. We discuss possible methods to reduce the contribution of the K-correction bias and uncertainty.
A new precise measurement of |V cb | and of the branching ratio BR(B 0 → D * + ℓ −ν ℓ) has been p... more A new precise measurement of |V cb | and of the branching ratio BR(B 0 → D * + ℓ −ν ℓ) has been performed using a sample of about 5000 semileptonic decaysB 0 → D * + ℓ −ν ℓ , selected by the DELPHI detector at LEP I by tagging the soft pion from D * + → D 0 π +. The results are: V cb = (39.0 ± 1.5 (stat.) +2.5 −2.6 (syst. exp.) ± 1.3 (syst. th.)) × 10 −3 BR(B 0 → D * + ℓ −ν ℓ) = (4.70 ± 0.13 (stat.) +0.36 −0.31 (syst. exp.))% The analytic dependences of the differential cross-section and of the Isgur Wise form factor as functions of the variable w = v B 0 • v D * have also been obtained by unfolding the experimental resolution.
A search for charginos nearly mass degenerate with the lightest neutralino is performed with the ... more A search for charginos nearly mass degenerate with the lightest neutralino is performed with the data collected by the ALEPH detector at LEP, at centre-ofmass energies between 189 and 209 GeV, corresponding to an integrated luminosity of 628 pb −1. The analysis is based on the detection of isolated and energetic initial state radiation photons, produced in association with chargino pairs whose decay products have little visible energy. The number of candidate events observed is in agreement with that expected from Standard Model background sources. These
A wide field space-based imaging telescope is necessary to fully exploit the technique of observi... more A wide field space-based imaging telescope is necessary to fully exploit the technique of observing dark matter via weak gravitational lensing. This first paper in a three part series outlines the survey strategies and relevant instrumental parameters for such a mission. As a concrete example of hardware design, we consider the proposed Supernova/Acceleration Probe (SNAP). Using SNAP engineering models, we quantify the major contributions to this telescope's Point Spread Function (PSF). These PSF contributions are relevant to any similar wide field space telescope. We further show that the PSF of SNAP or a similar telescope will be smaller than current ground-based PSFs, and more isotropic and stable over time than the PSF of the Hubble Space Telescope. We outline survey strategies for two different regimesa "wide" 300 square degree survey and a "deep" 15 square degree survey that will accomplish various weak lensing goals including statistical studies and dark matter mapping.
Space Telescopes and Instrumentation 2008: Optical, Infrared, and Millimeter, 2008
An integral field spectrograph concept has been developed for the SNAP/JDEM(SuperNova/Acceleratio... more An integral field spectrograph concept has been developed for the SNAP/JDEM(SuperNova/Acceleration Probe) experiment. This spectrograph will be optimized for faint supernovae and galaxies in a 3×6 arsec2 at low spectral resolution (R~100) through the wavelength range (0.35-1.7 mum). The integral field method is based on glass image slicer. A prototype of this instrument has been build to validate the concept
The recent proposal by Hawking and Turok for obtaining an open inflationary universe from singula... more The recent proposal by Hawking and Turok for obtaining an open inflationary universe from singular instantons makes use of low-energy effective Lagrangians describing gravity coupled to scalars and non-propagating antisymmetric tensors. In this paper we derive some exact results for Lagrangians of this type, obtained from spherical compactifications of M-theory and string theory. In the case of the S 7 compactification of M-theory, we give a detailed discussion of the cosmological solutions. We also show that the lower-dimensional Lagrangians admit domain-wall solutions, which preserve one half of the supersymmetry, and which approach AdS spacetimes near their horizons.
The lifetime of the B ° has been measured in a data sample of 889 000 hadronic events recorded wi... more The lifetime of the B ° has been measured in a data sample of 889 000 hadronic events recorded with the ALEPH detector at LEP. After background subtraction 30.8-4-6.9 events are attributed to the semileptonic decay of the Bs ° to a Ds and an opposite-sign lepton. A maximum-likelihood fit to the distribution of the proper times of these events 1 09+0"45 "4-0.04 ps. yields a Bs ° lifetime of zBs ....-0.35
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1996
DELPHI (DEtector with Lepton, Photon and Hadron Identification) is a detector for e+e-physics, de... more DELPHI (DEtector with Lepton, Photon and Hadron Identification) is a detector for e+e-physics, designed to provide high granularity over a 47r solid angle, allowing an effective particle identification. It has been operating at the LEP (Large Electron-Positron) collider at CERN since 1989. This article reviews its performance.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1997
We present a simulation of the signal delivered by minimum ionising particles crossing an MSGC. T... more We present a simulation of the signal delivered by minimum ionising particles crossing an MSGC. The parameters, adjusted to the experimental data, are reported for different gas mixtures. The simulation is then applied to the study of the bunch crossing identification at LHC. We present the performance of different pulse shapings and processing algorithms in the LHC environment.
The European Physical Journal C - Particles and Fields, 2003
Searches for resonantν production in e + e − collisions under the assumption that R-parity is not... more Searches for resonantν production in e + e − collisions under the assumption that R-parity is not conserved and that the dominant R-parity violating coupling is λ 121 or λ 131 used data recorded by DELPHI in 1997 to 2000 at centre-of-mass energies of 183 to 208 GeV. No deviation from the Standard Model was observed. Upper limits are given for the λ 121 and λ 131 couplings as a function of the sneutrino mass and total width. The limits are especially stringent for sneutrino masses equal to the centre-of-mass energies with the highest integrated luminosities recorded.
The data collected with the DELPHI detector at centre-of-mass energies between 130 and 172 GeV, d... more The data collected with the DELPHI detector at centre-of-mass energies between 130 and 172 GeV, during LEP operation in 1995 and 1996, have been used to determine the hadronic and leptonic cross-sections and leptonic forward{ backward asymmetries. In addition, the cross-section ratios and forward{ backward asymmetries for avour-tagged samples of light (uds), c and b quarks have been measured. The results are interpreted by performing S-matrix ts to these data and to the data collected previously at the energies near the Z 0 resonance peak (88-93 GeV). The results are also interpreted in terms of contact interactions, which parameterise physics beyond the Standard Model. Further interpretation of the data is made in terms of possible R-parity violating SUSY particles and of possible Z 0 bosons. No signicant deviations from the Standard Model expectations are found and limits are given for the various interpretations which are made of physics beyond the Standard Model.
The DELPHI experiment at LEP has measured the inclusive c harmless B hadron decay branching ratio... more The DELPHI experiment at LEP has measured the inclusive c harmless B hadron decay branching ratio, the B branching ratio into two c harmed particles, and the total number of charmed particles per B decay, using the hadronic Z data taken between 1992 and 1995. The results are extracted from a t to the b-tagging probability distribution based on the precise impact parameter measurements made using the microvertex detector. The inclusive c harmless B branching ratio, including B decays into hidden charm (c c), is measured to be 0:033 0:021. The B branching ratio into two o p e n c harmed particles is 0:136 0:042. The mean number of charmed particles per B decay (including hidden charm) is 1:147 0:041. After subtracting the B decay branching ratio into hidden charm, the charmless B branching ratio is found to be 0:007 0:021, compatible with the Standard Model expectation. Models that predict an additional contribution to the charmless B branching ratio of 0.037 or higher are excluded with at least 95% condence.
The Nearby Supernova Factory reports that spectra (range 320-1000 nm) of supernovae 2005gn and 20... more The Nearby Supernova Factory reports that spectra (range 320-1000 nm) of supernovae 2005gn and 2005hb (IAUC #8616), obtained October 18.6 UT with the Supernova Integral Field Spectrograph on the University of Hawaii 2.2-meter telescope, indicate that both supernovae are of Type II. SN2005gn is a Type IIn supernova at a redshift of z = 0.0397, with prominent H- alpha (FWHM 4000 km/s) and Ca II IR triplet emission.
From the data recorded with the DELPHI detector at LEP in the years 1991-1992, 46 497 events were... more From the data recorded with the DELPHI detector at LEP in the years 1991-1992, 46 497 events were selected having a high-momentum muon in hadron jets. A fit to the average electric charge sum of the jets recoiling against a b-quark jet tagged by a high-PT muon results in an average mixing parameter of~ = 0.1444-0.014(stat.)_+0100~(syst.).
We estimate systematic errors due to K-corrections in standard photometric analyses of high redsh... more We estimate systematic errors due to K-corrections in standard photometric analyses of high redshift Type Ia supernovae. Errors due to K-correction occur when the spectral template model underlying the lightcurve fitter poorly represents the actual supernova spectral energy distribution, meaning that the distance modulus cannot be recovered accurately. In order to quantify this effect, synthetic photometry is performed on artificially redshifted spectrophotometric data from 119 low-redshift supernovae from the Nearby Supernova Factory, and the resulting lightcurves are fit with a conventional lightcurve fitter. We measure the variation in the standardized magnitude that would be fit for a given supernova if located at a range of redshifts and observed with various filter sets corresponding to current and future supernova surveys. We find significant variation in the measurements of the same supernovae placed at different redshifts regardless of filters used, which causes dispersion greater than ∼ 0.05 mag for measurements of photometry using the Sloan-like filters and a bias that corresponds to a 0.03 shift in w when applied to an outside data set. To test the result of a shift in supernova population or environment at higher redshifts, we repeat our calculations with the addition of a reweighting of the supernovae as a function of redshift and find that this strongly affects the results and would have repercussions for cosmology. We discuss possible methods to reduce the contribution of the K-correction bias and uncertainty.
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Papers by G. Smadja