Efficient, reliable and fast high-level triggering using a bonsai boosted decision tree

High-level triggering is a vital component in many modern particle physics experiments. This paper describes a modification to the standard boosted decision tree (BDT) classifier, the so-called "bonsai" BDT, that has the following important properties: it is more efficient than traditional cut-based approaches; it is robust against detector instabilities, and it is very fast. Thus, it is fit-for-purpose for the online running conditions faced by any large-scale data acquisition system.Comment: 10 pages, 2 figure

Improved Method of Determining Metabolic Function

The present invention provides a novel lactate difference imaging (LDI) technique, allowing assessment of the metabolic response to tissue over a period of time. This approach utiliizes lactate change over a time period as an indiactor of viable tissue, and offers benefits in the management and treatment of the effects of many common diseases, in particular stroke

Branching fraction and CP asymmetry of the decays B+→K0Sπ+ and B+→K0SK+

An analysis of B+ → K0 Sπ+ and B+ → K0 S K+ decays is performed with the LHCb experiment. The pp collision data used correspond to integrated luminosities of 1 fb−1 and 2 fb−1 collected at centre-ofmass energies of √ s = 7 TeV and √ s = 8 TeV, respectively. The ratio of branching fractions and the direct CP asymmetries are measured to be B(B+ → K0 S K+ )/B(B+ → K0 Sπ+ ) = 0.064 ± 0.009 (stat.) ± 0.004 (syst.), ACP(B+ → K0 Sπ+ ) = −0.022 ± 0.025 (stat.) ± 0.010 (syst.) and ACP(B+ → K0 S K+ ) = −0.21 ± 0.14 (stat.) ± 0.01 (syst.). The data sample taken at √ s = 7 TeV is used to search for B+ c → K0 S K+ decays and results in the upper limit ( fc · B(B+ c → K0 S K+ ))/( fu · B(B+ → K0 Sπ+ )) < 5.8 × 10−2 at 90% confidence level, where fc and fu denote the hadronisation fractions of a ¯b quark into a B+ c or a B+ meson, respectively

Search for the rare decay D0→μ+μ−

A search for the rare decay D0→μ+μ− is performed using a data sample, corresponding to an integrated luminosity of 0.9 fb−1, of pp collisions collected at a centre-of-mass energy of 7 TeV by the LHCb experiment. The observed number of events is consistent with the background expectations and corresponds to an upper limit of View the MathML source at 90% (95%) confidence level. This result represents an improvement of more than a factor twenty with respect to previous measurements

Search for long-lived scalar particles in B+→K+χ(μ+μ−)B^+ \to K^+\chi(\mu^+\mu^-) decays

A search for a long-lived scalar particle χ is performed, looking for the decay $B^+ \to K^+\chi$ with $\chi \to \mu^+\mu^-$ in $pp$ collision data corresponding to an integrated luminosity of 3  fb$^{−1}$, collected by the LHCb experiment at center-of-mass energies of $\sqrt{s}$ = 7 and 8 TeV. This new scalar particle, predicted by hidden sector models, is assumed to have a narrow width. The signal would manifest itself as an excess in the dimuon invariant mass distribution over the Standard Model background. No significant excess is observed in the accessible ranges of mass $250 < m(\chi) < 4700  MeV/c^2$ and lifetime $0.1 < \tau(\chi) < 1000  ps$. Upper limits on the branching fraction $\mathscr{B}(B^+ \to K^+\chi(\mu^+\mu^-))$ at 95% confidence level are set as a function of $m(\chi)$ and $\tau(\chi)$, varying between $2 \times 10^{−10}$ and $10^{−7}$. These are the most stringent limits to date. The limits are interpreted in the context of a model with a light inflaton particle

Search for long-lived scalar particles in B + → K + χ ( μ + μ − ) decays

A search for a long-lived scalar particle χ is performed, looking for the decay B[superscript +]→K[superscript +]χ with χ→μ[superscript +]μ[superscript -] in pp collision data corresponding to an integrated luminosity of 3  fb[superscript -1], collected by the LHCb experiment at center-of-mass energies of √s =7 and 8 TeV. This new scalar particle, predicted by hidden sector models, is assumed to have a narrow width. The signal would manifest itself as an excess in the dimuon invariant mass distribution over the Standard Model background. No significant excess is observed in the accessible ranges of mass 250<m(χ)<4700  MeV/c[superscript 2] and lifetime 0.1<τ(χ)<1000  ps. Upper limits on the branching fraction B(B[superscript +]→K[superscript +]χ(μ[superscript +]μ[superscript -])) at 95% confidence level are set as a function of m(χ) and τ(χ), varying between 2×10[superscript -10] and 10[superscript -7]. These are the most stringent limits to date. The limits are interpreted in the context of a model with a light inflaton particle.National Science Foundation (U.S.