118072730
Construction and test of the prototype chamber for region 1 of the LHCb muon station 2
A four gapMWPC prototypefor region 1 of the muonstation2, with non-staggered wires,wasbuilt andtested.Theconstructiondetailsandthetestresultsarepresented. 1 Intr oduction TheLHCb muonsystem[1] will useMulti-Wire ProportionalChambers(MWPC) for thefour regionsof stations2 and3, for regions3 and4 of station1 andfor regions1 and2 of stations4 and5. Thechambersvary in sizefor thedifferentstationsandregionsandthey have different readoutpadsizesin thoseregions(see[2] for moredetails). In this note,theconstructionof a MWPC prototypefor region 1 of station2 is described.The prototypeis an exact realization of a chamberfor this region. It hasfour symmetricgasgapsandthe characteristicslisted in table1. Table1: Somechamberparametersandoperationconditions. GasGapsize(mm) 5 Anode-Cathodespacing(mm) 2.5 Wire Diameter( m) 30 Sensiti vearea(mm ) 300 250 Wire pitch (mm) 1.5 Wire padsize(mm ) 6.3 250 Wire length(mm) 257 Cathodepadsize(mm ) 37.5 31.3 Wire Tension(gf) 60 10 NominalGasmixture (40%50%10%) Wire nominalpotential(V) 3150 The chamberhasa combinedreadoutof wire andcathodepadsasa consequenceof the requiredgranularity. 2 Chamber Construction The prototypewasbuilt in Rio (CEFET-RJ andLAPE/IF-UFRJ)with PCB-honeycomb-PCB panelsas describedin the Muon SystemTDR [1]. The panels’flatnesswas measured(INMETRO1 andBargoa2) to be within m, which is betterthanthe requiredspecifications (see[3]). Thewire fixation barswerealsomeasuredandgluedto thecathodepanels.Theanodeto cathodedistancewasinsuredbymeansof aprecisesteelspacerfixedto thosebars,during thegluing of thewires. For thepresentprototypethewire fixation barswerenot machinedto have a noseon theedgeswhich wasdonefor thepreviousprototypesto avoid dischar ges[3]. The resultsfor the dark currentandthe sparklimit show that this noseis not necessary . The darkcurrentmeasuredwasof theorderof thenA andthesparklimit wasof about3.45kV. The wiring wasdonein a latheasshown in thepictureof figure1. The wire tensionwas guaranteedusinga calibrateddevice asshown in figure 2. This device hasa DC motor that keepsthewire undertensionby applyinga torqueon thereel. TheDC voltageappliedto the motorwascalibratedwith a60gf weight. 1InstitutoNacionaldeMetrologia,Normalizaç̃aoe QualidadeIndustrial,Rio deJaneiro 2BargoaConectores, Rio deJaneiro
347666
Novel considerations about the non-equilibrium regime of the tricritical point in a metamagnetic model: Localization and tricritical exponents
a b s t r a c t We have investigated the time-dependent regime of a two-dimensional metamagnetic model at its tri- critical point via Monte Carlo simulations. First, we obtained the temperature and magnetic field corre- sponding to the tricritical point of the model by using a refinement process based on optimization of the coefficient of determination in the log-log fit of magnetization decay as a function of time. With these es- timates in hand, we obtained the dynamic tricritical exponents θ and z and the static tricritical exponents ν and β by using the universal power-law scaling relations for the staggered magnetization and its mo- ments at an early stage of the dynamic evolution. Our results at the tricritical point confirm that this model belongs to the two-dimensional Blume-Capel model universality class for both static and dynamic behav- iors, and they also corroborate the conjecture of Janssen and Oerding for the dynamics of tricritical points.
33202267
Generalized field theoretical approach to general relativity and conserved quantities in anti–de Sitter spacetimes
A new prescription to calculate the total energies and angular momenta of asymptotically $(d+1)$-dimensional anti\char21{}de Sitter spacetimes is proposed. The method is based on an extension of the field theoretical approach to general relativity to the case where there is an effective cosmological constant. A $(d\ensuremath{-}1)$ form $\ensuremath{\Omega}$ is exhibited which, when integrated on asymptotic $(d\ensuremath{-}1)$-dimensional boundary surfaces, yields the values of those conserved quantities. The calculations are gauge independent once asymptotic conditions are not violated. Total energies and angular momenta of some known solutions in four and five dimensions are calculated agreeing with standard results.
118403419
A method to identify and characterise binary candidates - a study of CoRoT data
The analysis of the CoRoT space mission data was performed aiming to test a method that selects, among the several light curves observed, the transiting systems that likely host a low-mass star orbiting the main target. The method identifies stellar companions by fitting a model to the observed transits. Applying this model, that uses equations like Kepler's third law and an empirical mass-radius relation, it is possible to estimate the mass and radius of the primary and secondary objects as well as the semimajor axis and inclination angle of the orbit. We focus on how the method can be used in the characterisation of transiting systems having a low-mass stellar companion with no need to be monitored with radial-velocity measurements or ground-based photometric observations. The model, which provides a good estimate of the system parameters, is also useful as a complementary approach to select possible planetary candidates. A list of confirmed binaries together with our estimate of their parameters are presented. The characterisation of the first twelve detected CoRoT exoplanetary systems was also performed and agrees very well with the results of their respective announcement papers. The comparison with confirmed systems validates our method, specially when the radius of the secondary companion is smaller than 1.5 Rjup, in the case of planets, or larger than 2 Rjup, in the case of low-mass stars. Intermediate situations are not conclusive.
119246221
Photospheric parameters and C abundances in solar-like stars with and without planets
We have been analyzing a large sample of solar-like stars with and without planets in order to homogeneously measure their photospheric parameters and Carbon abundances. Our sample contains around 200 stars in the solar neighborhood observed with the ELODIE spectrograph, for which the observational data are publicly available. We performed spectral synthesis of prominent bands of C 2 and CI lines, aiming to accurately obtain the C abundances. We intend to contribute homogeneous results to studies that compare elemental abundances in stars with and without known planets. New arguments will be brought forward to the discussion of possible chemical anomalies that have been suggested in the literature, leading us to a better understanding of the planetary formation process. In this work we focus on the C abundances in both stellar groups of our sample.
15537902
The Lick AGN Monitoring Project 2011: Reverberation Mapping of Markarian 50
The Lick AGN Monitoring Project 2011 observing campaign was carried out over the course of 11 weeks in spring 2011. Here we present the first results from this program, a measurement of the broad-line reverberation lag in the Seyfert 1 galaxy Mrk 50. Combining our data with supplemental observations obtained prior to the start of the main observing campaign, our data set covers a total duration of 4.5 months. During this time, Mrk 50 was highly variable, exhibiting a maximum variability amplitude of a factor of ~4 in the U-band continuum and a factor of ~2 in the Hβ line. Using standard cross-correlation techniques, we find that Hβ and Hγ lag the V-band continuum by τ_(cen) = 10.64^(+0.82)_(–0.93) and 8.43^(+1.30)_(–1.28) days, respectively, while the lag of He II λ4686 is unresolved. The Hβ line exhibits a symmetric velocity-resolved reverberation signature with shorter lags in the high-velocity wings than in the line core, consistent with an origin in a broad-line region (BLR) dominated by orbital motion rather than infall or outflow. Assuming a virial normalization factor of f = 5.25, the virial estimate of the black hole mass is (3.2 ± 0.5) × 10^7 M_☉. These observations demonstrate that Mrk 50 is among the most promising nearby active galaxies for detailed investigations of BLR structure and dynamics.
118450072
Accurate and homogeneous abundance patterns in solar-type stars of the solar neighbourhood: a chemo-chronological analysis
Aims. We report the derivation of abundances of C, Na, Mg, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, Y, Zr, Ba, Ce, Nd, and Sm in a sample of 25 solar-type stars of the solar neighbourhood, correlating the abundances with the stellar ages, kinematics, and orbital parameters. Methods. The spectroscopic analysis, based on data of high resolution and high signal-to-noise ratio, was differential to the Sun and applied to atomic line equivalent widths supplemented by the spectral synthesis of C and C2 features. We also performed a statistical study by using the method of tree clustering analysis, searching for groups of stars sharing similar elemental abundance patterns. We derived the stellar parameters from various criteria, with average errors of 30 K, 0.13 dex, and 0.05 dex, respectively, for Teff, log g ,a nd [Fe/H]. The average error of the [X/Fe] abundance ratios is 0.06 dex. Ages were derived from theoretical HR diagrams and membership of the stars in known kinematical moving groups. Results. We identified four stellar groups: one having, on average, over-solar abundances (� [X/H]� =+ 0.26 dex), another with undersolar abundances (� [X/H]� = −0.24 dex), and two with intermediate values (� [X/H]� = −0.06 and +0.06 dex) but with distinct chemical patterns. Stars sharing solar metallicity, age, and Galactic orbit possibly have non-solar abundance ratios, a possible effect either of chemical heterogeneity in their natal clouds or migration. A trend of [Cu/Fe] with [Ba/Fe] seems to exist, in agreement with previous claims in the literature, and maybe also of [Sm/Fe] with [Ba/Fe]. No such correlation involving C, Na, Mn, and Zn is observed. The [X/Fe] ratios of various elements show significant correlations with age. [Mg/Fe], [Sc/Fe], and [Ti/Fe] increase with age. [Mn/Fe] and [Cu/Fe] display a more complex behaviour, first increasing towards younger stars up to the solar age, and then decreasing, a result we interpret as possibly related to time-varying yields of SN Ia and the weak s-process in massive stars. The steepest negative age relation is due to [Ba/Fe], but only for stars younger than the Sun, and a similar though less significant behaviour is seen for Zr, Ce, and Nd. [Sr/Fe] and [Y/Fe] show a linearly increasing trend towards younger stars. The [Cu/Ba] and [Sm/Ba] therefore decrease for younger stars. We found that [Ba/Mg], [Ba/Zn], and [Sr,Y,Ba/Sm] increase but only for stars younger than the Sun, whereas the [Sr/Mg], [Y/Mg], [Sr/Zn], and [Y/Zn] ratios increase linearly towards younger stars over the whole age range.