ttH production at the LHC

• Laura Reina (Florida State University)

Room: Aula Seminari The associated production of a Higgs boson with top quarks is going to give direct access to the top-Higgs Yukawa coupling and will play a crucial role in constraining new physics from a combined measurement of Higgs-boson couplings. In this talk we will review the theoretical work done to provide reliable tools for present and future experimental analyses.

Improving the ttH signal at the LHC through spin-polarization effects

• Barbara Mele (INFN Roma)

Room: Aula Seminari New strategies to improve the signal-to-background ratio for Higgs production in association with a top-quark pair at the LHC, based on top-quark spin properties, will be presented.

Diphoton production at LHC: the main background for Higgs boson searches

• Leandro Cieri (INFN Roma)

Room: Aula Seminari Diphoton production is the main background in searches and studies for a low mass Higgs boson, decaying in a pair of photons. Due to current searches and studies at the LHC, it is desirable to count with the best theoretical tool to describe this background. In this talk we will present the details behind the calculation, which is based on the transverse momentum subtraction formalism, and show different results obtained using a code that calculates diphoton production at NNLO in perturbative QCD. We will talk about the comparison with the LHC data and Tevatron data and discuss why the NNLO is necessary to understand the phenomenology of this process.

The Higgs->Zll spectrum at low Q2: SM vs. light new physics

• Martin Alonso-Gonzalez (INFN LNF)

Room: Aula Seminari We analyse the H->Zll spectrum at low values of the dilepton pair invariant mass. First we present precise predictions of the spectrum within the Standard Model, taking into account the effects due to QCD resonances. Then we illustrate the sensitivity of this spectrum to New Physics models with exotic light states and the natural connection with the (g - 2) anomaly.

(Meta) stability of the electroweak vacuum

• Pier Paolo Giardino (INFN Roma 3)

Room: Aula Seminari Since the discovery of the Higgs boson at LHC, experimentalists and theorists have studied its properties in the hope of finding some hints of new physics. Unfortunately the data appear to converge toward Standard Model predictions, therefore it could be reasonable to investigate the behavior of the SM beyond its natural range of energy. We find that the measured Higgs and top masses put the SM in a near-critical situation, where the minimum of the EW vacuum is at the border between the stable and the unstable phases. In order to distinguish between these two states, we made a NNLO calculation of the corrections to the Higgs quartic coupling. I will illustrate the results of our calculations.

Overview of the latest LHCb results

• Ricardo Vazquez-Gomez (INFN LNF)

Room: Aula Seminari During the first LHC run in 2011 and 2012, the LHCb experiment has collected a total of 3/fb of proton-proton collision data at a centre-of-mass energy of 7 and 8 TeV. These data has allowed to perform a wide variety of analysis in B, D and Kaon decays as well as electroweak and QCD measurements in the unique rapidity region 2 < eta < 5 covered by the LHCb detector. An overview of the latest LHCb results will be given, covering rare meson decays, CP violation in B mesons, charm physics, spectroscopy, QCD and electroweak measurements

Status of SUSY after the 8 TeV LHC run

• Nazila Mahmoudi (CERN &amp; LPC Clermont-Ferrand)

Room: Aula Seminari I will review the implications of the direct SUSY and Higgs search results at the LHC and emphasize on the differences between constrained scenarios, such as mSUGRA, and more general MSSM scenarios. Complementary information can also be obtained using monojet searches at the LHC, as well as from Dark Matter experiments and flavour physics data, that will be described briefly. Finally, I will present projected results for the next LHC run.

SUSY searches status with the CMS detector

• Ferdinando Giordano (INFN Catania)

Room: Aula Seminari The LHC first run came to an end in February 2013 after three years of extraordinary performance. Major advances in physics have been achieved, including the discovery of a new light Higgs particle. This discovery is in agreement with many predictions from simple SuperSymmetric (SUSY) theories, which also predict light super-partners particles. The mass of some of these particles is required to be within the LHC reach by naturalness, therefore an extensive program of searches for new physics phenomena beyond the Standard Model is pursued by the major experiments. In this talk, the most recent results on SUSY searches from the CMS collaboration are presented, covering a broad number of models and scenarios.

Long Lived Particles Searches in SUSY and BSM in the ATLAS experiment

• Monica Verducci (INFN Roma)

Room: Aula Seminari Many models of physics beyond the Standard Model predict new particles with long lifetimes. Examples include Supersymmetry with R-parity violation, suppressed decays of the next-to-lightest supersymmetric particle, or models with hidden sectors. The Large Hadron Collider has extended the reach of particle-physics experiments with a potential for discovery of new physics at the TeV scale and many searches have been carried out by both ATLAS and CMS. The methodology of the searches (reconstruction techniques, background suppression, etc.) and the sensitivity of these searches in the ATLAS experiment are reviewed.

Models for proton-proton scattering at LHC: asymptotic limits, black-disk limit and geometrical scaling

• Giulia Pancheri (INFN LNF)

Room: Aula Seminari We discuss recent LHC measurements for the total, elastic and inelastic cross-sections, by TOTEM, CMS, ATLAS and ALICE collaborations in the light of present phenomenological predictions. We present result of various models, including an empirical model for elastic pp scattering at LHC, which indicates that the asymptotic black-disk limit R=(elastic cross section)/(total cross section) =1/2 is far from being reached, and discuss the implications on classical geometrical scaling behaviour. We propose a geometrical scaling law for the position of the dip in the differential elastic cross-section. The new scaling law allows to make predictions valid both for intermediate and asymptotic energies.

NLO theoretical predictions for the cross-section ratio ttbb/ttjj at the LHC

• Giuseppe Bevilacqua (INFN LNF)

Room: Aula Seminari Triggered by ongoing experimental searches at the LHC, we present updated NLO QCD predictions on the ratio of ttbb and ttjj production rates for present and future collider energies. We perform a detailed study of the kinematics and scale uncertainties of the two processes with the goal of assessing if and how much possible correlations help to reduce the theoretical uncertainty of the ratio, thus enhancing the predictive power of this observable.

Quark-hadron duality and large-x PDFs

• Aurore Courtoy (Université de Liège)

Room: Aula Seminari We present an analysis of the role of the running coupling constant at the intersection of perturbative and non-perturbative QCD. A unified description of the 2 regimes (pQCD and NP QCD) might derive through the definition of the effective coupling, as they both provide ways of analyzing its freezing in the IR region. We extract the effective coupling from all available experimental data on the unpolarized structure function of the proton at large values of Bjorken x, including the resonance region. We suggest that parton-hadron duality observed in this region can be explained if non-perturbative effects are included in the coupling constant. The outcome of our analysis is a smooth transition from perturbative to non-perturbative QCD physics, embodied in the running of the coupling constant at intermediate scales. While our approach is purely perturbative, we compare our result to various non-perturbative schemes.