Development of a server monitoring tool and defining performance thresholds

Today we depend on data based services, for example in logistics, at warehouses, and accounting services. When a data based service is delayed it can depend on its servers being overloaded, leading to economic losses. To prevent this, it is necessary to have appropriate monitoring tools that can make the system administrators aware of when performance thresholds have been breached and servers are reaching a critical state. The focus of this thesis was twofold: to define performance thresholds and to simplify monitoring of critical servers with presentation on a dashboard. As a result of this, two thresholds were produced. A threshold for high CPU utilization which further improved the existing performance thresholds by making the required time for triggering dependent on the current CPU utilization. This proved to give us a better result in 75% of the tested cases compared to the previous model. The second produced threshold was for low CPU utilization. Through studying servers with more allocated resources than they require it was possible to inform the system administrator to disable or reallocate those resources to another server with higher demand for resources. This reduces server costs and improves performance in some cases. The primary intention behind implementing a dashboard was to have a way of presenting when the defined thresholds had been breached. After evaluation of the dashboard through a usability test we came to the conclusion that all end-users were satisfied with the prototype and four out of five considered the dashboard to be a tool which they would use in the near future

Search for heavy neutrinos in K+→μ+νμK^+ \rightarrow \mu^+ \nu_{\mu} decays

International audienceThe NA62 experiment recorded a large sample of K+→μ+νμ decays in 2007. A peak search has been performed in the reconstructed missing mass spectrum. In the absence of a signal, limits in the range 2×10−6 to 10−5 have been set on the squared mixing matrix element |Uμ4|2 between muon and heavy neutrino states, for heavy neutrino masses in the range 300–375 MeV/ c2 . The result extends the range of masses for which upper limits have been set on the value of |Uμ4|2 in previous production search experiments

New high statistics measurement of K-e4 decay form factors and pi pi scattering phase shifts

We report results from a new measurement of the K-e4 decay K-+/- -> pi(+)pi(-)e(+/-)nu by the NA48/2 collaboration at the CERN SPS, based on a partial sample of more than 670 000 K-e4 decays in both charged modes collected in 2003. The form factors of the hadronic current (F,G,H) and pi pi phase difference (delta=delta(s)-delta(p)) have been measured in ten independent bins of the pi pi mass spectrum to investigate their variation. A sizeable acceptance at large pi pi mass, a low background and a very good resolution contribute to an improved experimental accuracy, a factor two better than in the previous measurement, when extracting the pi pi scattering lengths a(0) (0) and a(0) (2). Under the assumption of isospin symmetry and using numerical solutions of the Roy equations, the following values are obtained in the plane (a(0) (0),a(0) (2)): a(0) (0)=0.233 +/- 0.016(stat)+/- 0.007(syst),a(0) (2)=-0.0471 +/- 0.011(stat)+/- 0.004syst. The presence of potentially large isospin effects is also considered and will allow comparison with precise predictions from Chiral Perturbation Theory

Measurement of the form factors of charged kaon semileptonic decays

International audienceA measurement of the form factors of charged kaon semileptonic decays is presented, based on 4.4 × 10$^{6}$K$^{±}$ → π$^{0}$e$^{±}$ν$_{e}$ (K$_{e3}^{±}$ ) and 2.3 × 10$^{6}$K$^{±}$ → π$^{0}$μ±ν$_{μ}$ (K$_{μ3}^{±}$ ) decays collected in 2004 by the NA48/2 experiment. The results are obtained with improved precision as compared to earlier measurements. The combination of measurements in the K$_{e3}^{±}$ and K$_{μ3}^{±}$ modes is also presented

A new measurement of the K-+/- -> pi(+/-)gamma gamma decay at the NA48/2 experiment

The NA48/2 experiment at CERN collected two data samples with minimum bias trigger conditions in 2003 and 2004. A measurement of the rate and dynamic properties of the rare decay K-+/- -> pi(+/-)gamma gamma from these data sets based on 149 decay candidates with an estimated background of 15.5 +/- 0.7 events is reported. The model-independent branching ratio in the kinematic range z = (m(gamma gamma)/m(K))(2) > 0.2 is measured to be B-MI(z > 0.2) = (0.877 +/- 0.089) x 10(-6), and the branching ratio in the full kinematic range assuming a particular Chiral Perturbation Theory description to be B(K-pi gamma gamma) = (0.910 +/- 0.075) x 10(-6). (C) 2014 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/3.0/)

Search for the dark photon in pi(0) decays

A sample of 1.69 x 10(7) fully reconstructed pi(0) -> gamma e(+)e(-) decay candidates collected by the NA48/2 experiment at CERN in 2003-2004 is analyzed to search for the dark photon (A') production in the pi(0) -> gamma A' decay followed by the prompt A' -> e(+)e(-) decay. No signal is observed, and an exclusion region in the plane of the dark photon mass m(A') and mixing parameter epsilon(2) is established. The obtained upper limits on epsilon(2) are more stringent than the previous limits in the mass range 9 MeV/c(2) pi(+/-)A' decay is also evaluated. (C) 2015 The Authors. Published by Elsevier B.V