Rubin-LSST

Abstract:

A measurement of splitting scales, as defined by the kT clustering algorithm, is presented for final states containing a W boson produced in proton–proton collisions at a centre-of-mass energy of 7 TeV. The measurement is based on the full 2010 data sample corresponding to an integrated luminosity of 36 pb−1 which was collected using the ATLAS detector at the CERN Large Hadron Collider. Cluster splitting scales are measured in events containing W bosons decaying to electrons or muons. The measurement comprises the four hardest splitting scales in a kT cluster sequence of the hadronic activity accompanying the W boson, and ratios of these splitting scales. Backgrounds such as multi-jet and top-quark-pair production are subtracted and the results are corrected for detector effects. Predictions from various Monte Carlo event generators at particle level are compared to the data. Overall, reasonable agreement is found with all generators, but larger deviations between the predictions and the data are evident in the soft regions of the splitting scales.

Abstract:

Galactic black hole binaries produce powerful outflows which emit over almost the entire electromagnetic spectrum. Here, we report the first detection with the Herschel observatory of a variable far-infrared source associated with the compact jets of the black hole transient GX 339-4 during the decay of its recent 2010-2011 outburst, after the transition to the hard state. We also outline the results of very sensitive radio observations conducted with the Australia Telescope Compact Array, along with a series of near-infrared, optical (OIR) and X-ray observations, allowing for the first time the re-ignition of the compact jets to be observed over a wide range of wavelengths. The compact jets first turn on at radio frequencies with an optically thin spectrum that later evolves to an optically thick synchrotron emission. An OIR reflare is observed about 10 d after the onset of radio and hard X-ray emission, likely reflecting the necessary time to build up enough density, as well as to have acceleration (e.g. through shocks) along an extended region in the jets. The Herschel measurements are consistent with an extrapolation of the radio inverted power-law spectrum, but they highlight a more complex radio to OIR spectral energy distribution for the jets. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.

Abstract:

Two-particle correlations in relative azimuthal angle (Δρ) and pseudorapidity (Δη) are measured in √sNN=5.02 TeV p+Pb collisions using the ATLAS detector at the LHC. The measurements are performed using approximately 1 μb-1 of data as a function of transverse momentum (pT) and the transverse energy (ΣETPb) summed over 3.1<η<4.9 in the direction of the Pb beam. The correlation function, constructed from charged particles, exhibits a long-range (2<|Δη|<5) "near-side" (Δρ∼0) correlation that grows rapidly with increasing ΣETPb. A long-range "away-side" (Δρ∼π) correlation, obtained by subtracting the expected contributions from recoiling dijets and other sources estimated using events with small ΣETPb, is found to match the near-side correlation in magnitude, shape (in Δη and Δρ) and ΣETPb dependence. The resultant Δρ correlation is approximately symmetric about π/2, and is consistent with a dominant cos2Δρ modulation for all ΣETPb ranges and particle pT. © 2013 CERN.

Abstract:

We revisit the paradigm of the dependence of jet power on black hole (BH) spin in accreting BH systems. In a previous paper, we showed that the luminosity of compact jets continuously launched due to accretion on to BHs in X-ray binaries (analogous to those that dominate the kinetic feedback from active galactic nuclei) does not appear to correlate with reported BH spin measurements. It is therefore unclear whether extraction of the BH spin energy is the main driver powering compact jets from accreting BHs. Occasionally, BH X-ray binaries produce discrete, transient (ballistic) jets for a brief time over accretion state changes. Here, we quantify the dependence of the power of these transient jets (adopting two methods to infer the jet power) on BH spin, making use of all the available data in the current literature, which include 12 BHs with both measured spin parameters and radio flares over the state transition. In several sources, regular, well-sampled radio monitoring has shown that the peak radio flux differs dramatically depending on the outburst (up to a factor of 1000), whereas the total power required to energize the flare may only differ by a factor of≲4 between outbursts. The peak flux is determined by the total energy in the flare and the time over which it is radiated (which can vary considerably between outbursts). Using a Bayesian fitting routine, we rule out a statistically significant positive correlation between transient jet power measured using these methods and current estimates of BH spin. Even when selecting sub-samples of the data that disregard some methods of BH spin measurement or jet power measurement, no correlation is found in all cases. © 2013 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.