Roma Tre University

About: Roma Tre University is a education organization based out in Rome, Lazio, Italy. It is known for research contribution in the topics: Large Hadron Collider & Galaxy. The organization has 4434 authors who have published 15352 publications receiving 374888 citations. The organization is also known as: Universita degli Studi Roma Tre & RomaTre.

Search for direct top-squark pair production in final states with two leptons in pp collisions at √s = 8 TeV with the ATLAS detector

Abstract: A search is presented for direct top-squark pair production in final states with two leptons (electrons or muons) of opposite charge using 203 fb−1 of pp collision data at √s = 8 TeV, collected by the ATLAS experiment at the Large Hadron Collider in 2012 No excess over the Standard Model expectation is found The results are interpreted under the separate assumptions (i) that the top squark decays to a b-quark in addition to an on-shell chargino whose decay occurs via a real or virtual W boson, or (ii) that the top squark decays to a t-quark and the lightest neutralino A top squark with a mass between 150 GeV and 445 GeV decaying to a b-quark and an on-shell chargino is excluded at 95% confidence level for a top squark mass equal to the chargino mass plus 10 GeV, in the case of a 1 GeV lightest neutralino Top squarks with masses between 215 (90) GeV and 530 (170) GeV decaying to an on-shell (off-shell) t-quark and a neutralino are excluded at 95% confidence level for a 1 GeV neutralino

The galaxy-halo connection from a joint lensing, clustering and abundance analysis in the CFHTLenS/VIPERS field

Abstract: We present new constraints on the relationship between galaxies and their host dark matter haloes, measured from the location of the peak of the stellar-to-halo mass ratio (SHMR), up to the most massive galaxy clusters at redshift z ∼ 0.8 and over a volume of nearly 0.1 Gpc3. We use a unique combination of deep observations in the CFHTLenS/VIPERS field from the near-UV to the near-IR, supplemented by ∼60 000 secure spectroscopic redshifts, analysing galaxy clustering, galaxy–galaxy lensing and the stellar mass function. We interpret our measurements within the halo occupation distribution (HOD) framework, separating the contributions from central and satellite galaxies. We find that the SHMR for the central galaxies peaks at Mh,peak=1.9+0.2−0.1×1012M⊙ Mh,peak=1.9−0.1+0.2×1012M⊙ with an amplitude of 0.025, which decreases to ∼0.001 for massive haloes ( Mh>1014M⊙ Mh>1014M⊙ ). Compared to central galaxies only, the total SHMR (including satellites) is boosted by a factor of 10 in the high-mass regime (cluster-size haloes), a result consistent with cluster analyses from the literature based on fully independent methods. After properly accounting for differences in modelling, we have compared our results with a large number of results from the literature up to z = 1: we find good general agreement, independently of the method used, within the typical stellar-mass systematic errors at low to intermediate mass ( M⋆<1011M⊙ M⋆<1011M⊙ ) and the statistical errors above. We have also compared our SHMR results to semi-analytic simulations and found that the SHMR is tilted compared to our measurements in such a way that they over- (under-) predict star formation efficiency in central (satellite) galaxies.

On genuine cross-spectral density matrices

Abstract: For an electromagnetic stochastic beam, the choice of the mathematical structure of the cross-spectral density matrix is limited by the constraint of non-negative definiteness. We present a sufficient condition for building these matrices in such a way that this constraint is automatically satisfied. This allows us to put into evidence that electromagnetic beams can exhibit very peculiar correlation properties, some of which would not be encountered in scalar treatments. These results are illustrated by means of a number of examples.

Leading isospin breaking effects on the lattice

Abstract: We present a method to evaluate on the lattice the leading isospin breaking effects due to both the small mass difference between the up and down quarks and the QED interaction. Our proposal is applicable in principle to any $\mathrm{QCD}+\mathrm{QED}$ gauge invariant hadronic observable that can be computed on the lattice. It is based on the expansion of the path integral in powers of the small parameters $({\stackrel{^}{m}}_{d}\ensuremath{-}{\stackrel{^}{m}}_{u})/{\ensuremath{\Lambda}}_{\mathrm{QCD}}$ and ${\stackrel{^}{\ensuremath{\alpha}}}_{\mathrm{em}}$, where ${\stackrel{^}{m}}_{f}$ is the renormalized quark mass and ${\stackrel{^}{\ensuremath{\alpha}}}_{\mathrm{em}}$ the renormalized fine structure constant. In this paper we discuss in detail the general strategy of the method and the conventional, although arbitrary, separation of QCD from QED isospin breaking corrections. We obtain results for the pion mass splitting, ${M}_{{\ensuremath{\pi}}^{+}}^{2}\ensuremath{-}{M}_{{\ensuremath{\pi}}^{0}}^{2}=1.44(13)(16)\ifmmode\times\else\texttimes\fi{}{10}^{3}\text{ }\text{ }{\mathrm{MeV}}^{2}$, for the Dashen's theorem breaking parameter ${\ensuremath{\epsilon}}_{\ensuremath{\gamma}}=0.79(18)(18)$, for the light quark masses, $[{\stackrel{^}{m}}_{d}\ensuremath{-}{\stackrel{^}{m}}_{u}](\overline{\mathrm{MS}},2\text{ }\text{ }\mathrm{GeV})=2.39(8)(17)\text{ }\text{ }\mathrm{MeV}$, $[{\stackrel{^}{m}}_{u}/{\stackrel{^}{m}}_{d}](\overline{\mathrm{MS}},2\text{ }\text{ }\mathrm{GeV})=0.50(2)(3)$, and for the flavor symmetry breaking parameters $R$ and $Q$. We also update our previous results for the QCD isospin breaking corrections to the ${K}_{\ensuremath{\ell}2}$ decay rate and for the QCD contribution to the neutron-proton mass splitting. The numerical results of this paper have been obtained by using the gluon field configurations produced by the ETMC Collaboration with ${n}_{f}=2$ dynamical quarks. We treated the dynamical quarks as electrically neutral particles (electroquenched approximation) and neglected a disconnected diagram in the charged and neutral pion mass splitting. We provide all the formulas necessary to remove these approximations and discuss in detail the estimate of the associated systematic uncertainties.

The LLUNATIC data-cleaning framework

Abstract: Data-cleaning (or data-repairing) is considered a crucial problem in many database-related tasks. It consists in making a database consistent with respect to a set of given constraints. In recent years, repairing methods have been proposed for several classes of constraints. However, these methods rely on ad hoc decisions and tend to hard-code the strategy to repair conflicting values. As a consequence, there is currently no general algorithm to solve database repairing problems that involve different kinds of constraints and different strategies to select preferred values. In this paper we develop a uniform framework to solve this problem. We propose a new semantics for repairs, and a chase-based algorithm to compute minimal solutions. We implemented the framework in a DBMS-based prototype, and we report experimental results that confirm its good scalability and superior quality in computing repairs.