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The LHCb experiment has been taking data at the Large Hadron Collider (LHC) at CERN since the end of 2009. One of its key detector components is the Ring-Imaging Cherenkov (RICH) system. This provides charged particle identification over a wide momentum range, from 2–100 GeV/ c . The operation and control, software, and online monitoring of the RICH system are described. The particle identification performance is presented, as measured using data from the LHC. Excellent separation of hadronic particle types ( π , K, p) is achieved.

During 2011 the LHCb experiment at CERN collected 1.0 fb −1 of pp collisions. Due to the large heavy quark production cross-sections, these data provide unprecedented samples of heavy flavoured hadrons. The first results from LHCb have made a significant impact on the flavour physics landscape and have definitively proved the concept of a dedicated experiment in the forward region at a hadron collider. This document discusses the implications of these first measurements on classes of extensions to the Standard Model, bearing in mind the interplay with the results of searches for on-shell production of new particles at ATLAS and CMS. The physics potential of an upgrade to the LHCb detector, which would allow an order of magnitude more data to be collected, is emphasised.

This article recounts the initial difficulties of the US occupation of Iraq that enabled the growth and maturation of the Iraqi insurgency. The focus will be on how the US military adapted, while in combat, to a situation for which its prior training and doctrinal focus had left it ill prepared. The article will explain the challenges faced by military leaders to move from a hierarchical, cold war-designed approach to warfare, to a more adaptive, decentralised mode of operations that requires distributed authority and decision making. The story will be told from the perspective of two strategic planners who helped shape the campaign plan for the coalition forces in Iraq, including the challenges they encountered when attempting to unify all elements of US national power against the Iraqi insurgency.

A search is presented for long-lived particles with a mass between 25 and 50  GeV / c 2 and a lifetime between 1 and 200 ps in a sample of proton–proton collisions at a centre-of-mass energy of s = 7  TeV, corresponding to an integrated luminosity of 0.62  fb - 1 , collected by the LHCb detector. The particles are assumed to be pair-produced by the decay of a standard model-like Higgs boson. The experimental signature of the long-lived particle is a displaced vertex with two associated jets. No excess above the background is observed and limits are set on the production cross-section as a function of the long-lived particle mass and lifetime.

This erratum corrects measurements of the prompt and secondary (from-b).

This erratum corrects measurements of the prompt and secondary (from- b ).

The angular distribution of the dimuon system of the decays.

A bstract The first observation of the B s 0  →  D s ∗ ∓ K ± decay is reported using 3.0 fb −1 of proton-proton collision data collected by the LHCb experiment. The D s ∗ ∓ mesons are reconstructed through the decay chain D s ∗ ∓  →  γD s ∓ ( K ∓ K ± π ∓ ). The branching fraction relative to that for B s 0  →  D s ∗ − π + decays is measured to be ℬ B s 0 → D s ∗ ∓ K ± / ℬ B s 0 → D s ∗ − π + = 0.068 ± 0.00 5 − 0.002 + 0.003 , where the first uncertainty is statistical and the second is systematic. Using a recent measurement of ℬ B s 0 → D s ∗ − π + , the absolute branching fraction of B s 0  →  D s ∗ ∓ K ± is measured as ℬ B s 0 → D s ∗ ∓ K ± = 16.3 ± 1.2 stat − 0.5 + 0.7 syst ± 4.8 norm × 1 0 − 5 , where the third uncertainty is due to the uncertainty on the branching fraction of the normalisation channel.

A search for the doubly charmed baryon$ \\Xi_{cc}^{+} $in the decay mode$ \\Xi_{cc}^{+}\\to \\Lambda_c^{+}{K^{-}}{\\pi^{+}} $is performed with a data sample, corresponding to an integrated luminosity of 0.65 fb −1 , of pp collisions recorded at a centre-of-mass energy of 7 TeV. No significant signal is found in the mass range 3300-3800 MeV /c 2 . Upper limits at the 95% confidence level on the ratio of the$ \\Xi_{cc}^{+} $production cross-section times branching fraction to that of the$ \\Lambda_c^{+} $, R , are given as a function of the$ \\Xi_{cc}^{+} $mass and lifetime. The largest upper limits range from R < 1.5 × 10 − 2 for a lifetime of 100 fs to R < 3 . 9 × 10 −4 for a lifetime of 400 fs.

The decay$ B_c^{+}\\to {J \\left/ {{\\psi {K^{+}}} \\right.} $is observed for the first time using a data sample, corresponding to an integrated luminosity of 1.0 fb −1 , collected by the LHCb experiment in pp collisions at a centre-of-mass energy of 7 TeV. A yield of 46 ± 12 events is reported, with a significance of 5.0 standard deviations. The ratio of the branching fraction of$ B_c^{+}\\to {J \\left/ {{\\psi {K^{+}}} \\right.} $to that of$ B_c^{+}\\to {J \\left/ {{\\psi {\\pi^{+}}} \\right.} $is measured to be 0.069 ± 0.019 ± 0.005, where the first uncertainty is statistical and the second is systematic.