Rubin-LSST

Abstract:

The radio/X-ray correlation for hard and quiescent state black hole X-ray binaries is critically investigated in this paper. New observations of known sources, along with newly discovered ones (since 2003), have resulted in an increasingly large number of outliers lying well outside the scatter about the quoted best-fitting relation. Most of these outliers tend to cluster below the best-fitting line, possibly indicative of two distinct tracks which might reflect different accretion regimes within the hard state. Here, we employ and compare state of the art data clustering techniques in order to identify and characterize different data groupings within the radio/X-ray luminosity plane for 18 hard and quiescent state black hole X-ray binaries with nearly simultaneous multiwavelength coverage. Linear regression is then carried out on the clustered data to infer the parameters of a relationship of the form ℓr=α+βℓx through a Bayesian approach (where ℓ denotes logarithmic luminosities). We conclude that the two-cluster model, with independent linear fits, is a significant improvement over fitting all points as a single cluster. While the upper track slope (0.63 ± 0.03) is consistent, within the errors, with the fitted slope for the 2003 relation (0.7 ± 0.1), the lower track slope (0.98 ± 0.08) is not consistent with the upper track or with the widely adopted value of ≃1.4 for the neutron stars. The two luminosity tracks do not reflect systematic differences in black hole spins as estimated either from reflection- or continuum-fitting method. Additionally, there is evidence for at least two sources (H1743-322 and GRO J1655-500) jumping from the lower to the upper track as they fade towards quiescence, further indicating that black hole spin does not play any major role in defining the radio loudness of compact jets from hard black hole X-ray binaries. The results of the clustering and regression analysis are fairly insensitive to the selection of subsamples, accuracy in the distances and the treatment of upper limits. Besides introducing a further level of complexity in understanding the interplay between synchrotron and Comptonized emission from black hole X-ray binaries, the existence of two tracks in the radio/X-ray domain underscores that a high level of caution must be exercised when employing black hole luminosity-luminosity relations for the purpose of estimating a third parameter, such as distance or mass. © 2012 The Authors Monthly Notices of the Royal Astronomical Society © 2012 RAS.

Abstract:

Measurements from the CMS experiment at the LHC of dihadron correlations for charged particles produced in PbPb collisions at a nucleon-nucleon centre-of-mass energy of 2. 76 TeV are presented. The results are reported as a function of the particle transverse momenta (pT) and collision centrality over a broad range in relative pseudorapidity (Δη) and the full range of relative azimuthal angle (Δφ). The observed two-dimensional correlation structure in Δη and Δφ is characterised by a narrow peak at (Δη,Δφ)≈(0,0) from jet-like correlations and a long-range structure that persists up to at least {pipe}Δη{pipe}=4. An enhancement of the magnitude of the short-range jet peak is observed with increasing centrality, especially for particles of pT around 1-2 GeV/c. The long-range azimuthal dihadron correlations are extensively studied using a Fourier decomposition analysis. The extracted Fourier coefficients are found to factorise into a product of single-particle azimuthal anisotropies up to pT≈3-3. 5 GeV/c for at least one particle from each pair, except for the second-order harmonics in the most central PbPb events. Various orders of the single-particle azimuthal anisotropy harmonics are extracted for associated particle pT of 1-3 GeV/c, as a function of the trigger particle pT up to 20 GeV/c and over the full centrality range. © 2012 CERN for the benefit of the CMS collaboration.

Abstract:

In the ATLAS experiment, a system called COMA (Conditions/Configuration Metadata for ATLAS), has been developed to make globally important run-level metadata more readily accessible. It is based on a relational database storing directly extracted, refined, reduced, and derived information from system-specific database sources as well as information from non-database sources. This information facilitates a variety of unique dynamic interfaces and provides information to enhance the functionality of other systems. This presentation will give an overview of the components of the COMA system, enumerate its diverse data sources, and give examples of some of the interfaces it facilitates. We list important principles behind COMA schema and interface design, and how features of these principles create coherence and eliminate redundancy among the components of the overall system. In addition, we elucidate how interface logging data has been used to refine COMA content and improve the value and performance of end-user reports and browsers..

Abstract:

A measurement of the exclusive two-photon production of muon pairs in proton-proton collisions at √s = 7TeV, pp → pμ+μ -p, is reported using data corresponding to an integrated luminosity of 40 pb-1. For muon pairs with invariant mass greater than 11:5 GeV, transverse momentum p (μ) > 4 GeV and pseudorapidity σ(μ) < 2:1, a t to the dimuon pT(μ+μ-) distribution results in a measured cross section of η(p → pμ+μ -p) = 3:38+0:580:55 (stat:)±0:16 (syst:)±0:14 (lumi:) pb, consistent with the theoretical prediction evaluated with the event generator Lpair. The ratio to the predicted cross section is 0:83+0:14 -0:13 (stat:) ± 0:04 (syst:) ± 0:03 (lumi:). The characteristic distributions of the muon pairs produced via fusion, such as the muon acoplanarity, the muon pair invariant mass and transverse momentum agree with those from the theory. Copyright © CERN.

Abstract:

A study of forward energy flow and central charged-particle multiplicity in events with W and Z bosons decaying into leptons is presented. The analysis uses a sample of 7 TeV pp collisions, corresponding to an integrated luminosity of 36 pb-1, recorded by the CMS experiment at the LHC. The observed forward energy depositions, their correlations, and the central charged-particle multiplicities are not well described by the available non-diffractive soft-hadron production models. A study of about 300 events with no significant energy deposited in one of the forward calorimeters, corresponding to a pseudorapidity gap of at least 1. 9 units, is also presented. An indication for a diffractive component in these events comes from the observation that the majority of the charged leptons from the W(Z) decays are found in the hemisphere opposite to the gap. When fitting the signed lepton pseudorapidity distribution of these events with predicted distributions from an admixture of diffractive (pompyt) and non-diffractive (pythia) Monte Carlo simulations, the diffractive component is determined to be (50. 0 ± 9. 3 (stat.) ± 5. 2 (syst.))%. © 2012 CERN for the benefit of the CMS collaboration.