1,721,122 research outputs found
Salvioni e la Corsica
No full textGli studi linguistici sui dialetti corsi portano Salvioni anche a posizioni significative sul ruolo dell'italiano in Corsica
Some and models facing current LHC searches
No full textWe present the implications of data collected by ATLAS and CMS in 2011 on some classes of Z′ and W′ models. We remark how the strongest bounds, coming for example from searches in final states containing leptons, do not apply to some theoretically well-motivated resonances, and discuss where signals from such states would appear
Relevance of the decay W' → Wγ at the early LHC
Full text linkWe study, employing an effective approach, the early LHC phenomenology of an isospin-singlet W', focusing on the process pp → W' → Wγ. We discuss how observation of this decay would be a hint of the compositeness of the
resonance, and present an estimate of the experimental reach in the 7TeV LHC run
Very boosted Higgs in gluon fusion
Full text linkThe Higgs production and decay rates offer a new way to probe new physics beyond the Standard Model. While dynamics aiming at alleviating the hierarchy problem generically predict deviations in the Higgs rates, the current experimental analyses cannot resolve the long- and short-distance contributions to the gluon fusion process and thus cannot access directly the coupling between the Higgs and the top quark. We investigate the production of a boosted Higgs in association with a high-transverse momentum jet as an alternative to the tt̄h channel to pin down this crucial coupling. Presented first in the context of an effective field theory, our analysis is then applied to models of partial compositeness at the TeV scale and of natural supersymmetry. © 2014 The Author(s)
(Dys)Zphilia or a custodial breaking Higgs at the LHC
Full text linkElectroweak precision measurements established that custodial symmetry is preserved to a good accuracy in the gauge sector after electroweak symmetry breaking. However, recent LHC results might be interpreted as pointing towards Higgs couplings that do not respect such symmetry. Motivated by this possibility, we reconsider the presence of an explicitly custodial breaking coupling in a generic Higgs parameterization. After briefly commenting on the large UV sensitivity of the T parameter to such a coupling, we perform a fit to results of Higgs searches at LHC and Tevatron, and find that the apparent enhancement of the ZZ channel with respect to WW can be accommodated. Two degenerate best-fit points are present, which we label 'Zphilic' and 'dysZphilic' depending on the sign of the hZZ coupling. Finally we highlight some measurements at future linear colliders that may remove such degeneracy
The dark penguin shines light at colliders
Full text linkAbstract: Collider experiments are one of the most promising ways to constrain Dark Matter (DM) interactions. For several types of DM-Standard Model couplings, a meaningful interpretation of the results requires to go beyond effective field theory, considering simplified models with light mediators. This is especially important in the case of loop-mediated interactions. In this paper we perform the first simplified model study of the magnetic dipole interacting DM, by including the one-loop momentum-dependent form factors that mediate the coupling — given by the Dark Penguin — in collider processes. We compute bounds from the monojet, monophoton, and diphoton searches at the 8 and 14 TeV LHC, and compare the results to those of direct and indirect detection experiments. Future searches at the 100 TeV hadron collider and at the ILC are also addressed. We find that the optimal search strategy requires loose cuts on the missing transverse energy, to capture the enhancement of the form factors near the threshold for on-shell production of the mediators. We consider both minimal models and models where an additional state beyond the DM is accessible. In the latter case, under the assumption of anarchic flavor structure in the dark sector, the LHC monophoton and diphoton searches will be able to set much stronger bounds than in the minimal scenario. A determination of the mass of the heavier dark fermion might be feasible using the MT2 variable. In addition, if the Dark Penguin flavor structure is almost aligned with that of the DM mass, a displaced signal from the decay of the heavier dark fermion into the DM and photon can be observed. This allows us to set constraints on the mixings and couplings of the model from an existing search for non-pointing photons
Exotic electroweak signals in the twin Higgs model
No full textThe twin Higgs model is the preeminent example of a theory of neutral naturalness, where the new particles that alleviate the little hierarchy problem are Standard Model (SM) singlets. The most promising collider search strategy, based on rare Higgs decays, is nevertheless not effective in significant regions of the parameter space of the low-energy theory. This underlines the importance of phenomenological studies on ultraviolet completions of the twin Higgs model, which must lie at a scale lower than 5-10 TeV. We pursue this course in the context of nonsupersymmetric completions, focusing on exotic fermions that carry SM electroweak and twin color charges, as well as on exotic vectors that transform as the bifundamental of the electroweak or color groups. Both Z2-preserving and Z2-breaking mass spectra are considered for the exotic fermions. In the former case they must be heavier than ∼1 TeV, but can still be sizably produced in the decays of the color bifundamental vector. In the Z2-breaking scenario, the exotic fermions can have masses in the few hundred GeV range without significantly increasing the fine-tuning. Once pair-produced through the electroweak interactions, they naturally form bound states held together by the twin color force, which subsequently annihilate back to SM particles. The associated resonance signals are discussed in detail. We also outline the phenomenology of the electroweak bifundamental vectors, some of which mix with the SM W and Z and can therefore be singly produced in hadron collisions
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