681 research outputs found
CPLEAR and BaBar: La violation de CP dans tous ses etats
No full textThis report of French 'Habilitation a diriger les recherches' summarizes my scientific activity from 1993 to 2003. During this decade, my research work was related to two particle physics experiments: CPLEAR and BABAR. The first one, CPLEAR, has recorded data from 1988 to 1995 on the low energy anti-proton ring (LEAR) at CERN. This experiment was devoted to the study of T, CPT et CP discrete symmetries. The second experiment, BABAR, has been running since 1999, on the PEP-II B factory at SLAC. This experiment searches for CP violation and tests the Standard Model through the measurements of the angles and the sides of the Unitarity Triangle. My research work is divided in five main topics: Study of CP and CPT violation in K0 → π+ π- decays; Performance optimization of the particle identification detector (DIRC) of the BABAR experiment; B meson tagging in BABAR experiment; Δmd measurement and Search for CP and T violation in mixing with dilepton events; Search for CP violation in B0 → ρ± π± and B0 → π± K± decays. (author
Observation of B**0 ---> omega K0, B+ ---> eta pi+, and B+ ---> eta K+ and study of related decays
No full textWe present measurements of branching fractions and charge asymmetries for seven B-meson decays with an eta, eta('), or omega meson in the final state. The data sample corresponds to 89x10(6) B (B) over bar pairs produced from e(+)e(-) annihilation at the Y(4S) resonance. We measure the following branching fractions in units of 10(-6): B(B+-->etapi(+))=5.3+/-1.0+/-0.3, B(B+-->etaK(+))=3.4+/-0.8+/-0.2, B(B-0-->etaK(0))=2.9+/-1.0+/-0.2 (eta(')pi(+))=2.7+/-1.2+/-0.3 (omegapi(+))=5.5+/-0.9+/-0.5, B(B+-->omegaK(+))=4.8+/-0.8+/-0.4, and B(B-0-->omegaK(0))=5.9(-1.3)(+1.6)+/-0.5. The charge asymmetries are A(ch)(B+-->etapi(+))=-0.44+/-0.18+/-0.01, A(ch)(B+-->etaK(+))=-0.52+/-0.24+/-0.01, A(ch)(B+-->omegapi(+))=0.03+/-0.16+/-0.01, and A(ch)(B+-->omegaK(+))=-0.09+/-0.17+/-0.01
Measurement of Collins asymmetries in inclusive production of charged pion pairs in e+e− annihilation at BABAR
No full textWe present measurements of Collins asymmetries in the inclusive process e+e−→ππX, where π stands for charged pions, at a center-of-mass energy of 10.6 GeV. We use a data sample of 468 fb−1 collected by the BABAR experiment at the PEP-II B factory at SLAC, and consider pairs of charged pions produced in opposite hemispheres of hadronic events. We observe clear asymmetries in the distributions of the azimuthal angles in two distinct reference frames. We study the dependence of the asymmetry on several kinematic variables, finding that it increases with increasing pion momentum and momentum transverse to the analysis axis, and with increasing angle between the thrust and beam axis
Measurements of CP violating asymmetries and branching fractions in B meson decays to eta-prime K
No full textWe present measurements of the branching fractions of the decays B+-->eta(')K(+) and B-0-->eta(')K(0). For B-0-->eta(')K(S)(0) we also measure the time-dependent CP-violation parameters (SetaKS0)-K-' and (CetaKS0)-K-', and for B+-->eta(')K(+) the time-integrated charge asymmetry A(ch). The data sample corresponds to 88.9x10(6) B (B) over bar pairs produced by e(+)e(-) annihilation at the Y(4S). The results are B(B+-->eta(')K(+))=(76.9+/-3.5+/-4.4)x10(-6), B(B-0-->eta(')K(0))=(60.6+/-5.6+/-4.6)x10(-6), (SetaKS0)-K-'=0.02+/-0.34+/-0.03, (CetaKS0)-K-'=0.10+/-0.22+/-0.04, and A(ch)=0.037+/-0.045+/-0.011
Observation of B meson decays to b(1)pi and b(1)K
No full textWe present the results of searches for decays of B mesons to final states with a b(1) meson and a charged pion or kaon. The data, collected with the BABAR detector at the Stanford Linear Accelerator Center, represent 382x10(6) B(B)over bar pairs produced in e(+)e(-) annihilation. The results for the branching fractions are, in units of 10(-6), B(B+ -> b(1)(0)pi(+)) = 6.7 +/- 1.7 +/- 1.0, B(B+ -> b(1)(0)K(+)) = 9.1 +/- 1.7 +/- 1.0, B(B-0 -> b(1)(-/+)pi +/- ) = 10.9 +/- 1.2 +/- 0.9, and B(B-0 -> b(1)(-)K(+)) = 7.4 +/- 1.0 +/- 1.0, with the assumption that B(b(1) -> omega pi) = 1. We also measure charge and flavor asymmetries A(ch)(B+ -> b(1)(0)pi(+)) = 0.05 +/- 0.16 +/- 0.02, A(ch)(B+ -> b(1)(0)K(+)) = -0.46 +/- 0.20 +/- 0.02, A(ch)(B-0 -> b(1)(-/+)pi +/- ) = -0.05 +/- 0.10 +/- 0.02, C(B-0 -> b(1)(-/+)pi +/- ) = -0.22 +/- 0.23 +/- 0.05, Delta C(B-0 -> b(1)(-/+)pi +/- ) = -1.04 +/- 0.23 +/- 0.08, and A(ch)(B-0 -> b(1)(-)K(+)) = -0.07 +/- 0.12 +/- 0.02. The first error quoted is statistical, and the second systematic
Measurements of branching fractions and time-dependent CP-violating asymmetries in B -> eta ' K decays
No full textWe present measurements of the B ->eta(')K branching fractions; for B+->eta(')K(+) we measure also the time-integrated charge asymmetry A(ch), and for B-0->eta(')K(S)(0) the time-dependent CP-violation parameters S and C. The data sample corresponds to 232x10(6) B (B) over bar pairs produced by e(+)e(-) annihilation at the Upsilon(4S). The results are B(B ->eta(')K(+))=(68.9 +/- 2.0 +/- 3.2)x10(-6), B(B-0->eta(')K(0))=(67.4 +/- 3.3 +/- 3.2)x10(-6), A(ch)=0.033 +/- 0.028 +/- 0.005, S=0.30 +/- 0.14 +/- 0.02, and C=-0.21 +/- 0.10 +/- 0.02, where the first error quoted is statistical and the second is systematic
Branching fractions and CP-violating asymmetries in radiative B decays to eta K gamma
No full textWe present measurements of the CP-violation parameters S and C for the radiative decay B-0 --> eta K-S(0)gamma; for B --> eta K gamma we also measure the branching fractions and for B+ --> K+gamma the time-integrated charge asymmetry A(ch). The data, collected with the BABAR detector at the Stanford Linear Accelerator Center, represent 465 x 10(6) B (B) over bar pairs produced in e(+)e(-) annihilation. The results are S = -0.18(-0.46)(+0.49) +/- 0.12, C = -0.32(-0.39)(+0.40) +/- 0.07, B(B-0 --> eta K-0 gamma) = (7.1(-2.0)(+2.1) +/- 0.4) x 10(-6), B(B+ --> eta K+gamma) = (7.7 +/- 1.0 +/- 0.4) x 10(-6), and A(ch) = (-9.0(-9.8)(+10.4)) x 10(-2). The first error quoted is statistical and the second systematic
Observation of B+→ρ+K0 and measurement of its branching fraction and charge asymmetry
No full textWe present the first observation of the decay B+->rho K-+(0), using a data sample of 348 fb(-1) collected at the Upsilon(4S) resonance with the BABAR detector. The branching fraction and charge asymmetry are measured to be (8.0(-1.3)(+1.4)+/- 0.6)x10(-6) and (-12.2 +/- 16.6 +/- 2.0)%, respectively, where the first uncertainty is statistical and the second is systematic. The charge asymmetry is defined by A(ch)=(Gamma(-)(B)-Gamma(+)(B))/(Gamma(-)(B)+Gamma(+)(B)) with Gamma(+/-)(B) the B-+/- decay rate. The significance of the observed branching fraction, including systematic uncertainties, is 7.9 standard deviations
Prospects for Dark Energy Evolution: a Frequentist Multi-Probe Approach
No full textSubmitted to Astronomy & Astrophysics 14 pages, 8 figuresInternational audienceA major quest in cosmology is the understanding of the nature of dark energy. It is now well known that a combination of cosmological probes is required to break the underlying degeneracies on cosmological parameters. In this paper, we present a method, based on a frequentist approach, to combine probes without any prior constraints, taking full account of the correlations in the parameters. As an application, a combination of current SNIa and CMB data with an evolving dark energy component is first compared to other analyses. We emphasise the consequences of the implementation of the dark energy perturbations on the result for a time varying equation of state. The impact of future weak lensing surveys on the measurement of dark energy evolution is then studied in combination with future measurements of the cosmic microwave background and type Ia supernovae. We present the combined results for future mid-term and long-term surveys and confirm that the combination with weak lensing is very powerful in breaking parameter degeneracies. A second generation of experiment is however required to achieve a 0.1 error on the parameters describing the evolution of dark energy
Measurements of B meson decays to omega K-* and omega rho
No full textWe describe searches for B meson decays to the charmless vector-vector final states omegaK(*) and omegarho in 89x10(6) B (B) over bar pairs produced in e(+)e(-) annihilation at roots=10.58 GeV. We measure the following branching fractions in units of 10(-6): B(B-0-->omegaK(*0))=3.4(-1.6)(+1.8)+/-0.4(omegaK(*+))=3.5(-2.0)(+2.5)+/-0.7(omegarho(0))=0.6(-1.1)(+1.3)+/-0.4(omegarho(+))=12.6(-3.3)(+3.7)+/-1.6. The first error quoted is statistical, the second systematic, and the upper limits are defined at 90% confidence level. For B+-->omegarho(+) we also measure the longitudinal spin alignment fraction f(L)=0.88(-0.15)(+0.12)+/-0.03 and charge asymmetry A(ch)=(5+/-26+/-2)%
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