Next-to-leading order calculations matched to parton showers for supersymmetry and dark matter

• Benjamin Fuks

Room: Aula B1 The ATLAS and CMS collaborations are extensively investigating many different channels in order to get hints for new physics. Many of these searches are currently based on Monte Carlo simulations of the signals where leading-order matrix elements of different partonic multiplicities are matched to parton showers and merged. More sophisticated differential theoretical predictions are however always helpful for setting more accurate exclusion limits, possibly refining the search strategies, and measuring the model free parameters in case of a discovery. In this talk, I will discuss how the MadGraph5_aMC@NLO framework can provide a general platform for computing (differential) observables matching next-to-leading order accurate predictions to parton showers. This will be illustrated through specific examples in the context of dark matter simplified models and supersymmetry.

Top Physics with soft muons in ATLAS

• Umberto De Sanctis

Room: Aula B1 Top Physics in ATLAS is one of the crucial sector of the physics programme of the ATLAS experiment at the LHC.  Data collected, are usually analysed to explore top properties or search for heavy resonances, in final states characterised by the presence of jets, lepton(s) and missing transverse momentum. Nevertheless, the abundance of top quarks produced at LHC gives the possibility to focus also on other specific decay channels, such as the ones involving the presence of muons (called "soft-muons") coming from the semileptonic decays of the b-quarks that in turn come from top/antitop decays. In this seminar I will explore the possibility to use these "soft-muons" to measure quantities such as the top mass and the amount of CP violation in the semileptonic b-decays in Run2 data.

Small-x resummation in PDF fits

• Marco Bonvini

Room: Aula B1 I present a new determination of parton distribution functions (PDFs) which includes the resummation of large logarithms at small momentum fraction x, relevant at high energies. The description of the HERA data at small x, small Q improves considerably. The new PDFs, obtained from a global fit, exhibit smaller uncertainty at small x, and differ significantly to their fixed-order counterparts in this region. These results demonstrate how the exploration of novel dynamical regimes of QCD, in this case the BFKL regime, represents a fundamental ingredient of the physics program of future high-luminosity and high-energy colliders.