Constraining local UV field geometry at reionization using Milky Way satellites

We present a new semi-analytical model of the population of satellite galaxies of the Milky Way, aimed at estimating the effect of the geometry of reionization at galaxy scale on the properties of the satellites. In this model reionization can be either: (A) externally-driven and uniform, or (B) internally-driven, by the most massive progenitor of the Milky Way. In the latter scenario the propagation of the ionisation front and photon dilution introduce a delay in the photo-evaporation of the outer satellites' gas with respect to the inner satellites. As a consequence, outer satellites experience a longer period of star formation than those in the inner halo. We use simple models to account for star formation, the propagation of the ionisation front, photo-evaporation and observational biases. Both scenarios yield a model satellite population that matches the observed luminosity function and mass-to-light ratios. However, the predicted population for scenario (B) is significantly more extended spatially than for scenario (A), by about 0.3 dex in distance, resulting in a much better match to the observations. The survival of the signature left by the local UV field during reionization on the radial distribution of satellites makes it a promising tool for studying the reionization epoch at galaxy scale in the Milky Way and nearby galaxies resolved in stars with forthcoming large surveys.Comment: Proceedings of the conference "Assembling the puzzle of the Milky Way" held at Le Grand Bornand, 201

Tau Physics from B Factories

Some recent $\tau$-physics results are presented from the BaBar and Belle experiments at the SLAC and KEK B factories, which produce copious numbers of $\tau$-lepton pairs. Measurements of the tau mass and lifetime allow to test lepton universality and CPT invariance, while searches for lepton-flavour violation in tau decays are powerful ways to look for physics beyond the Standard Model. In semihadronic, non-strange tau decays, the vector hadronic final state is particularly important in helping determine the hadronic corrections to the anomalous magnetic moment of the muon, while studies of strange final states are the best available ways to measure the CKM matrix element $V_{\rm us}$ and the mass of the strange quark.Comment: Presented at Charm 2006, International Workshop on Tau-Charm Physics, June 05-07 2006, Beijing, Chin

Radiative Penguin Decays of B Mesons: Measurements of B -> K* gamma, B -> K2*(1430) gamma, and Search for B0 -> phi gamma

Electromagnetic radiative penguin decays of the B meson were studied with the BaBar detector at SLAC's PEP-II asymmetric-energy B Factory. Branching fractions and isospin asymmetry of the decay B -> K* gamma, branching fractions of B -> K2*(1430) gamma, and a search for B0 -> phi gamma are presented. The decay rates may be enhanced by contributions from non-standard model processes.Comment: 5 pages, 3 figures, presented at the 2004 Meeting of the Division of Particles and Fields of the American Physical Society, Riverside, CA, USA, August 26-31, 2004, submitted to International Journal of Modern Physics

The labour market after age 50: some elements of a Franco-American comparison

This paper examines various supply and demand side aspects of the French labour market for older workers and puts them in perspective by comparing them to the US case. We first consider the supply side incentives (or disincentives) of basic pension schemes for the two countries : for France, we discuss how these incentives have been changed by the 1993 and 2003 pension reforms and we present some projections of the impact of these reforms on labour force participation rates, based on the DESTINIE dynamic microsimulation model. We then discuss, on the demand side, the hypothesis of a wage-productivity gap for older workers which could explain their lower employment rates. Evidence in favor of this hypothesis is not overwhelming. Nevertheless, workers who lose their jobs at older ages probably suffer a large loss of firm-specific and sector-specific human capital. In the US, this does not preclude re-employment, but at the cost of significant drops of wage levels. In France, the collective choice has been made since the 1970s to allow older workers who lose their jobs to completely withdraw from the labour market : these workers have access to preretirement schemes or specific dispositions of unemployment insurance (including an exemption from seeking employment). This system proved difficult to regulate. Due to these difficulties, France has not been able to do more than stabilize the employment rate in the 55-64 age bracket during the 1990s, after 20 years of continuous decline. The key unanswered question is whether it will be possible to increase the employment rate of this age group in the next two decades.Pensions, preretirement, senior workers

Beyond CP violation: hadronic physics at BaBar

I report on recent studies of hadronic physics performed by the BaBar Collaboration. Emphasis is given to the measurement of the properties of newly discovered charmed hadrons and to the searches for light and heavy pentaquarks.Comment: 14 pages, 20 postscript figues, contributed to the Proceedings of the First APS Topical Group Meeting on Hadron Physics, Fermilab, Batavia, IL (October 24-26, 2004

Observation of B+ ---> a(1)+(1260) K0 and B0 ---> a(1)-(1260) K+

We present branching fraction measurements of the decays B^{+} -> a1(1260)^{+} K^{0} and B^{0} to a1(1260)^{-} K^{+} with a1(1260)^{+} -> pi^{-} pi^{+} pi^{+}. The data sample corresponds to 383 million B B-bar pairs produced in e^{+}e^{-} annihilation through the Y(4S) resonance. We measure the products of the branching fractions: B(B^{+}-> a1(1260)^{+} K^{0})B(a1(1260)^{+} -> pi^{-} pi^{+} pi^{+}) = (17.4 +/- 2.5 +/- 2.2) 10^{-6} B(B^{0}-> a1(1260)^{-} K^{+})B(a1(1260)^{-} -> pi^{+} pi^{-} pi^{-}) = (8.2 +/- 1.5 +/- 1.2) 10^{-6}. We also measure the charge asymmetries A_{ch}(B^{+} -> a1(1260)^{+} K^{0})= 0.12 +/- 0.11 +/- 0.02 and A_{ch}(B^{0} -> a1(1260)^{-} K^{+})= -0.16 +/- 0.12 +/- 0.01. The first uncertainty quoted is statistical and the second is systematic

Search for CP violation in the decays D0 ---> K- K+ and D0 ---> pi- pi+

We measure CP-violating asymmetries of neutral charmed mesons in the modes D0 --> K- K+ and D0 --> pi- pi+ with the highest precision to date by using D0 --> K- pi+ decays to correct detector asymmetries. An analysis of 385.8 fb-1 of data collected with the BaBar detector yields values of aCP(KK) = (0.00 +/- 0.34 (stat.) +/- 0.13 (syst.))% and aCP(pipi) = (-0.24 +/- 0.52 (stat.) +/- 0.22 (syst.))%, which agree with Standard Model prediction

Observation of the semileptonic decays B ---> D* tau- anti-nu(tau) and evidence for B ---> D tau- anti-nu(tau

We present measurements of the semileptonic decays B- --> D0 tau- nubar, B- --> D*0 tau- nubar, B0bar --> D+ tau- nubar, and B0bar --> D*+ tau- nubar, which are potentially sensitive to non--Standard Model amplitudes. The data sample comprises 232x10^6 Upsilon(4S) --> BBbar decays collected with the BaBar detector. From a combined fit to B- and B0bar channels, we obtain the branching fractions B(B --> D tau- nubar) = (0.86 +/- 0.24 +/- 0.11 +/- 0.06)% and B(B --> D* tau- nubar) = (1.62 +/- 0.31 +/- 0.10 +/- 0.05)% (normalized for the B0bar), where the uncertainties are statistical, systematic, and normalization-mode-related

Study of e+ e- ---> Lambda anti-Lambda, Lambda anti-Sigma0, Sigma0 anti-Sigma0 using initial state radiation with BABAR

We study the e+e- --> Lambda anti-Lambda gamma, Lambda anti-Sigma0 gamma, Sigma0 anti-Sigma0 gamma processes using 230 fb-1 of integrated luminosity collected by the BABAR detector at e+e- center-of-mass energy of 10.58 GeV. From the analysis of the baryon-antibaryon mass spectra the cross sections for e+e- --> Lambda anti-Lambda, Lambda anti-Sigma0, Sigma0 anti-Sigma0 are measured in the dibaryon mass range from threshold up to 3 GeV/c^2. The ratio of electric and magnetic form factors, |G_E/G_M|, is measured for e+e- --> Lambda anti-Lambda, and limits on the relative phase between Lambda form factors are obtained. We also measure the J/psi --> Lambda anti-Lambda, Sigma0 anti-Sigma0 and psi(2S) --> Lambda anti-Lambda branching fractions

Measurements of Partial Branching Fractions for anti-B ---> X(u) l anti-nu and Determination of |V(ub)|

We present partial branching fractions for inclusive charmless semileptonic B decays Bbar --> X_u ell nubar, and the determination of the CKM matrix element |V_{ub}|. The analysis is based on a sample of 383 million Y(4S) decays into B Bbar pairs collected with the BaBar detector at the PEP-II e+ e- storage rings. We select events using either the invariant mass M_X of the hadronic system, the invariant mass squared, q^2, of the lepton and neutrino pair, the kinematic variable P_+ or one of their combinations. We then determine partial branching fractions in limited regions of phase space: Delta B = (1.18 +- 0.09_{stat.} +- 0.07_{sys.} +- 0.01_{theo.}) x 10^{-3} (M_X 8 GeV^2/c^4). Corresponding values of |V_{ub}| are extracted using several theoretical calculations