A Comprehensive Spectroscopic Analysis of DB White Dwarfs

We present a detailed analysis of 108 helium-line (DB) white dwarfs based on model atmosphere fits to high signal-to-noise optical spectroscopy. We derive a mean mass of 0.67 Mo for our sample, with a dispersion of only 0.09 Mo. White dwarfs also showing hydrogen lines, the DBA stars, comprise 44% of our sample, and their mass distribution appears similar to that of DB stars. As in our previous investigation, we find no evidence for the existence of low-mass (M < 0.5 Mo) DB white dwarfs. We derive a luminosity function based on a subset of DB white dwarfs identified in the Palomar-Green survey. We show that 20% of all white dwarfs in the temperature range of interest are DB stars, although the fraction drops to half this value above Teff ~ 20,000 K. We also show that the persistence of DB stars with no hydrogen features at low temperatures is difficult to reconcile with a scenario involving accretion from the interstellar medium, often invoked to account for the observed hydrogen abundances in DBA stars. We present evidence for the existence of two different evolutionary channels that produce DB white dwarfs: the standard model where DA stars are transformed into DB stars through the convective dilution of a thin hydrogen layer, and a second channel where DB stars retain a helium-atmosphere throughout their evolution. We finally demonstrate that the instability strip of pulsating V777 Her white dwarfs contains no nonvariables, if the hydrogen content of these stars is properly accounted for.Comment: 74 pages including 30 figures, accepted for publication in the Astrophysical Journa

Quantum sensitivity limit of a Sagnac hybrid interferometer based on slow-light propagation in ultra-cold gases

The light--matter-wave Sagnac interferometer based on ultra-slow light proposed recently in (Phys. Rev. Lett. 92, 253201 (2004)) is analyzed in detail. In particular the effect of confining potentials is examined and it is shown that the ultra-slow light attains a rotational phase shift equivalent to that of a matter wave, if and only if the coherence transfer from light to atoms associated with slow light is associated with a momentum transfer and if an ultra-cold gas in a ring trap is used. The quantum sensitivity limit of the Sagnac interferometer is determined and the minimum detectable rotation rate calculated. It is shown that the slow-light interferometer allows for a significantly higher signal-to-noise ratio as possible in current matter-wave gyroscopes.Comment: 12 pages, 6 figure

Erratum: Measurements of prompt charm production cross-sections in pp collisions at root s = 13 TeV (vol 03, 159, 2016)

C. Baesso, M. Cruz Torres, C. Göbel, J. Molina Rodriguez are associated to Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil Y. Xie, J. Yu are associated to Center for High Energy Physics, Tsinghua University, Beijing, China D. A. Milanes, I. A. Monroy, J. A. Rodriguez Lopez are associated to LPNHE, Université Pierre et Marie Curie, Université Paris Diderot, CNRS/IN2P3, Paris, France O. Grünberg, M. Heß, C. Voß, R. Waldi are associated to Physikalisches Institut, Ruprecht-Karls-Universität Heidelberg, Heidelberg, Germany T. Likhomanenko, A. Malinin, V. Shevchenko, A. Ustyuzhanin are associated to Institute of Theoretical and Experimental Physics (ITEP), Moscow, Russia D. Derkach, E. Khairullin, T. Likhomanenko, A. Ustyuzhanin are associated to Institute of Theoretical and Experimental Physics (ITEP), Moscow, Russia F. Martinez Vidal, A. Oyanguren, P. Ruiz Valls, C. Sanchez Mayordomo are associated to Universitat de Barcelona, Barcelona, Spain C. J. G. Onderwater is associated to Nikhef National Institute for Subatomic Physics, Amsterdam, The Netherlands Deceased (T. M. Karbach

Erratum to: Measurements of the S-wave fraction in B0 → K+π−μ+μ− decays and the B0 → K∗(892)0μ+μ− differential branching fraction

Deceased (T.M. Karbach). C. Baesso, M. Cruz Torres, C. Göbel, J. Molina Rodriguez are associated to Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil J. He, X. Lyu, Y. Zhang, Y. Zheng are associated to Center for High Energy Physics, Tsinghua University, Beijing, China Y. Xie, H. Yin, J. Yu are associated to Center for High Energy Physics, Tsinghua University, Beijing, China D. A. Milanes, I. A. Monroy, J. A. Rodriguez Lopez are associated to LPNHE, Université Pierre et Marie Curie, Université Paris Diderot, CNRS/IN2P3, Paris, France O. Grünberg, M. Heß, C. Voß, R. Waldi are associated to Physikalisches Institut, Ruprecht-Karls-Universität Heidelberg, Heidelberg, Germany T. Likhomanenko, A. Malinin, A. Petrov, V. Shevchenko, A. Ustyuzhanin are associated to Institute of Theoretical and Experimental Physics (ITEP), Moscow, Russia M. Borisyak, D. Derkach, M. Hushchyn, E. Khairullin, T. Likhomanenko, A. Rogozhnikov, A. Ustyuzhanin are associated to Institute of Theoretical and Experimental Physics (ITEP), Moscow, Russia F. Martinez Vidal, A. Oyanguren, C. Remon Alepuz, P. Ruiz Valls, C. Sanchez Mayordomo are associated to Universitat de Barcelona, Barcelona, Spain C. J. G. Onderwater is associated to Nikhef National Institute for Subatomic Physics, Amsterdam, The Netherland

Erratum: Measurement of forward J/psi production cross-sections in pp collisions at root s = 13 TeV (vol 10, pg 172, 2015)

An issue has been identified in the simulated samples used to calculate the track reconstruction efficiencies, which affects the published J/ψ production cross-section in pp collisions at √s = 13 TeV [1]. A brief description of the nature of the problem is provided and then the corrected results are given

Measurement of CP asymmetry in D-0 -&gt; K- K+ decays

A measurement of the time-integrated CP asymmetry in the Cabibbo-suppressed decay D-0 -> K- K+ is performed using pp collision data, corresponding to an integrated luminosity of 3 fb(-1), collected with the LHCb detector at centre-of-mass energies of 7 and 8 TeV. The flavour of the charm meson at production is determined from the charge of the pion in D*(+) -> D-0 pi(+) and D*(-) -> (D) over bar (0)pi(-) decays. The time-integrated CP asymmetry A(CP)(K- K+) is obtained assuming negligible CP violation in charm mixing and in Cabibbo-favoured D-0 -> K- pi(+), D+ -> K- pi(+) pi(+) and D+ -> (K) over bar (0)pi(+) decays used as calibration channels. It is found to be A(CP)(K- K+) = (0.14 +/- 0.15 (stat) +/- 0.10 (syst))%. A combination of this result with previous LHCb measurements yields A(CP)(K- K+) = (0.04 +/- 0.12 (stat) +/- 0.10 (syst))%, A(CP)(pi(-) pi(+)) = (0.07 +/- 0.14 (stat) +/- 0.11 (syst))%. These are the most precise measurements from a single experiment. The result for ACP(K- K+) is the most precise determination of a time-integrated CP asymmetry in the charm sector to date, and neither measurement shows evidence of CP asymmetry

Study of 5 and 10 mm thick CZT strip detectors

We report progress in the study of 5 and 10 mm thick CZT strip detectors featuring orthogonal coplanar anode contacts. This novel anode geometry combines the advantages of pixel detectors with those of double-sided strip detectors. Like pixel detectors, these are electron-only devices that perform well as hard x-ray and y-ray spectrometers and imagers even in the thicker configurations required for reasonable detection efficiency at 1 MeV. Like double-sided strip detectors in an N x N configuration, these detectors require only 2N readout channels to form N2 “pixels”. Unlike doublesided strip detectors, all signal contacts for spectroscopy and 3- d imaging are formed on one detector surface. Polymer flip chip bonding to a ceramic substrate is employed resulting in a rugged and compact detector assembly. Prototype detector modules 5 mm thick have been fabricated and tested. Prototype modules, 10 mm thick, are currently in procurement. Measurements confirm these devices are efficient detectors throughout their volume. Sub-millimeter position resolution and energy resolution (FWHM) better than 3% at 662 keV and 15% at 60 keV throughout the detector volume are demonstrated. Options for processing the signals from the non-collecting anode strip contacts are discussed. Results from tests of one prototype circuit are presented. We also report on detector simulation studies aimed at defining an optimum geometry for the anode contacts and at determining optimum operating conditions and the requirements of the signal processing electronics