Ricerc@Sapienza

Using a data sample corresponding to an integrated luminosity of 2.0 fb−1, collected by the LHCb experiment, the production of the (1) state in proton–proton collisions at a centre-of-mass energy of √=13 TeV is studied in the rapidity range 2.0<<4.5 and in the transverse momentum range 6.5<T<14.0GeV. The cross-section for prompt production of (1) mesons relative to that of the / meson is measured using the ⎯⎯⎯ decay mode and is found to be (1)//=1.69±0.15±0.10±0.18.

A measurement of event-shape variables in proton-proton collisions at large momentum transfer is presented using data collected at s = 13 TeV with the ATLAS detector at the Large Hadron Collider. Six event-shape variables calculated using hadronic jets are studied in inclusive multijet events using data corresponding to an integrated luminosity of 139 fb−1. Measurements are performed in bins of jet multiplicity and in different ranges of the scalar sum of the transverse momenta of the two leading jets, reaching scales beyond 2 TeV.

Differential cross-sections are measured for top-quark pair production in the all-hadronic decay mode, using proton-proton collision events collected by the ATLAS experiment in which all six decay jets are separately resolved. Absolute and normalised single- and double-differential cross-sections are measured at particle and parton level as a function of various kinematic variables.

A measurement of event-shape variables in proton-proton collisions at large momentum transfer is presented using data collected at s = 13 TeV with the ATLAS detector at the Large Hadron Collider. Six event-shape variables calculated using hadronic jets are studied in inclusive multijet events using data corresponding to an integrated luminosity of 139 fb−1. Measurements are performed in bins of jet multiplicity and in different ranges of the scalar sum of the transverse momenta of the two leading jets, reaching scales beyond 2 TeV.

Differential cross-sections are measured for top-quark pair production in the all-hadronic decay mode, using proton-proton collision events collected by the ATLAS experiment in which all six decay jets are separately resolved. Absolute and normalised single- and double-differential cross-sections are measured at particle and parton level as a function of various kinematic variables.

A search for CP and P violation using triple-product asymmetries is performed with Λb0 → pK−π+π−, Λb0 → pK−K+K− and Ξb0 → pK−K−π+ decays. The data sample corresponds to integrated luminosities of 1.0 fb−1 and 2.0 fb−1, recorded with the LHCb detector at centre-of-mass energies of 7 TeV and 8 TeV, respectively. The CP - and P - violating asymmetries are measured both integrating over all phase space and in specific phase-space regions. No significant deviation from CP or P symmetry is found. The first observation of Λb0 → pK−χc0(1P)(→π+π−, K+K−) decay is also reported.

An analysis of the angular distribution of the decay Λb0 → Λμ+μ− is presented, using data collected with the LHCb detector between 2011 and 2016 and corresponding to an integrated luminosity of approximately 5 fb−1. Angular observables are determined using a moment analysis of the angular distribution at low hadronic recoil, corresponding to the dimuon invariant mass squared range 15 < q2 < 20 GeV2/c4. The full basis of observables is measured for the first time.

A search is performed for a spin-0 boson, ϕ, produced in proton-proton collisions at centre-of-mass energies of 7 and 8 TeV, using prompt ϕ → μ+μ− decays and a data sample corresponding to an integrated luminosity of approximately 3.0 fb−1 collected with the LHCb detector. No evidence is found for a signal in the mass range from 5.5 to 15 GeV. Upper limits are placed on the product of the production cross-section and the branching fraction into the dimuon final state.

A measurement of Z → τ+τ− production cross-section is presented using data, corresponding to an integrated luminosity of 2 fb−1, from pp collisions at s=8 TeV collected by the LHCb experiment. The τ+τ− candidates are reconstructed in final states with the first tau lepton decaying leptonically, and the second decaying either leptonically or to one or three charged hadrons. The production cross-section is measured for Z bosons with invariant mass between 60 and 120 GeV/c2, which decay to tau leptons with transverse momenta greater than 20 GeV/c and pseudorapidities between 2.0 and 4.5.

The ϒ(1S)μ+μ− invariant-mass distribution is investigated for a possible exotic meson state composed of two b quarks and two b¯ quarks, Xbb¯bb¯. The analysis is based on a data sample of pp collisions recorded with the LHCb detector at centre-of-mass energies s=7, 8 and 13 TeV, corresponding to an integrated luminosity of 6.3 fb−1. No significant excess is found, and upper limits are set on the product of the production cross-section and the branching fraction as functions of the mass of the Xbb¯bb¯ state.