A New Algorithm for Inclusive Search of SUSY Signal

A new algorithm designed to reduce the model dependence in future SUSY searches at the LHC is described. This algorithm can dynamically adapt itself to a wide range of possible SUSY final states thus reducing the need for detailed model-driven analysis. Preliminary study of its performance on simulated MSSM, GMSB and AMSB final states is described, and a comparison with traditional search procedures, whenever available, is performed.Comment: 18 pages, 9 figures, 1 Appendi

Testing sTGC with small angle wire edges for the ATLAS New Small Wheel Muon Detector Upgrade

The LHC upgrade scheduled for 2018 is expected to significantly increase the accelerator's luminosity, and as a result the radiation background rates in the ATLAS Muon Spectrometer will increase too. Some of its components will have to be replaced in order to cope with these high rates. Newly designed small-strip Thin Gap chambers (sTGC) will replace them at the small wheel region. One of the differences between the sTGC and the currently used TGC is the alignment of the wires along the azimuthal direction. As a result, the outermost wires approach the detector's edge with a small angle. Such a configuration may be a cause for various problems. Two small dedicated chambers were built and tested in order to study possible edge effects that may arise from the new configuration. The sTGC appears to be stable and no spark have been observed, yet some differences in the detector response near the edge is seen and further studies should be carried out.Comment: ANIMMA 2015 Conference proceedings, 20-24 April 2015, Lisbon, Portuga

On the Modelling of Energetic Multi-jet QCD Events

Physics beyond the Standard Model (BSM) may be unveiled by studying events with a high number of outgoing jets, produced at the LHC with energies above the TeV scale (energetic multi-jet events). Such events are dominated by QCD processes, where the calculations rely on some sort of approximation. Therefore, it is important to develop a robust approach for modeling such events that could probe the existence of BSM signals. In this note, jet spatial distributions in energetic multi-jet processes were compared using several state-of-the-art MC event generators. Slight differences were found, indicating modelling limitations. Therefore, a data-driven technique for the estimation of processes with a final state that contains a large number of jets is proposed. This procedure can predict jet multiplicities up to a precision of ~25\% in energetic multi-jet events.Comment: 12 pages, 7 figures. To appear in EPJ

Position resolution and efficiency measurements with large scale Thin Gap Chambers for the super LHC

New developments in Thin Gap Chambers (TGC) detectors to provide fast trigger and high precision muon tracking under sLHC conditions are presented. The modified detectors are shown to stand a high total irradiation dose equivalent to 6 Coulomb/cm of wire, without showing any deterioration in their performance. Two large (1.2 x 0.8 m^2) prototypes containing four gaps, each gap providing pad, strips and wires readout, with a total thickness of 50 mm, have been constructed. Their local spatial resolution has been measured in a 100 GeV/c muon test beam at CERN. At perpendicular incidence angle, single gap position resolution better than 60 microns has been obtained. For incidence angle of 20 degrees resolution of less than 100 micron was achieved. TGC prototypes were also tested under a flux of 10^5 Hz/cm^2 of 5.5-6.5 MeV neutrons, showing a high efficiency for cosmic muons detection.Comment: Presented at the 12 Vienna conference on Instrumentation, February 201

A data-driven method of pile-up correction for the substructure of massive jets

We describe a method to measure and subtract the incoherent component of energy flow arising from multiple interactions from jet shape/substructure observables of ultra-massive jets. The amount subtracted is a function of the jet shape variable of interest and not a universal property. Such a correction is expected to significantly reduce any bias in the corresponding distributions generated by the presence of multiple interactions, and to improve measurement resolution. Since in our method the correction is obtained from the data, it is not subject to uncertainties coming from the use of theoretical calculations and/or Monte Carlo event generators. We derive our correction method for the jet mass, angularity and planar flow. We find these corrections to be in good agreement with data on massive jets observed by the CDF collaboration. Finally, we comment on the linkage with the concept of jet area and jet mass area.Comment: 7 pages and 3 figures, minor correction

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements