arXiv subjects

Luca Fedeli

Publications and source records attributed to Luca Fedeli.

26 records · Page 2Linked to original sources

arXiv2014

Laser-Driven Rayleigh-Taylor Instability: Plasmonics Effects and Three-Dimensional Structures

The acceleration of dense targets driven by the radiation pressure of high-intensity lasers leads to a Rayleigh-Taylor instability (RTI) with rippling of the interaction surface. Using a simple model it is shown that the self-consistent modulation of the radiation pressure caused by a sinusoidal rippling affects substantially the wavevector spectrum of the RTI depending on the laser polarization. The plasmonic enhancement of the local field when the rippling period is close to a laser wavelength sets the dominant RTI scale. The nonlinear evolution is investigated by three dimensional simulations, which show the formation of stable structures with "wallpaper" symmetry.

physics.plasm-ph↗

arXiv2013

Discovery and Mass Spectroscopy via Mixed Di-Boson Production at the LHC in a 4-Site Model with a Composite Higgs Boson

We investigate the scope of the Large Hadron Collider (LHC) in probing the parameter space of a 4-Site (4S) model supplemented by one composite Higgs state. We concentrate on the yield of `mixed' di-boson production giving three leptons and missing (transverse) energy in the final state, i.e., events induced via the sub-process $q\bar q' -> l^+ν_l l^{'+}l^{'-}$ + ${\rm{c.c.}}$, where $q,q'$ are quarks and $l,l'=e,μ$ in all possible combinations, signature which enables the production in the intermediate steps of all additional -- with respect to the Standard Model (SM) -- neutral and charged gauge bosons belonging to the spectrum of this scenario, all of which in resonant topologies. We not only find this channel to be accessible over the background but also show that, after a dedicated cut-based analysis, kinematical reconstruction of all such resonances is always possible. We finally compare the yield of the mixed di-boson mode to that of the `charged' di-boson one and find that the former is of lesser scope than the latter at smaller gauge boson masses but it overcomes it at higher values, thereby revealing itself a viable search mode covering new regions of parameter space.

hep-ph↗

arXiv2012

Leptonic final states from di-boson production at the LHC in the 4-Dimensional Composite Higgs Model

We study di-boson production via both neutral and charged current at the Large Hadron Collider, i.e. subprocesses $q\bar q\to e^+ν_e μ^-\barν_μ$ + ${\rm{c.c.}}$ and $q\bar q'\to l^+ν_l l^{'+}l^{'-}$ + ${\rm{c.c.}}$, respectively, where $q,q'$ are quarks and $l,l'=e,μ$, in all possible combinations, in the context of the 4-Dimensional Composite Higgs Model. These modes enable the production in the intermediate steps of several additional -- with respect to the Standard Model -- neutral and charged gauge bosons belonging to the spectrum of this scenario, all of which in resonant topologies. We not only find these channels to be accessible over the background but also show that, after a dedicated cut-based analysis, kinematic reconstruction of most such resonances is always possible. However, since the Electro-Weak precision data generally disfavor neutral and charged gauge boson masses below the TeV range and also their large couplings to light-fermions, these modes turn out to be relevant only for the 14 TeV option with high integrated luminosity.

hep-ph↗

arXiv2012

Interference effects in heavy W'-boson searches at the LHC

Interference effects are widely neglected in searches for new physics. This is the case in recent publications on searches for W'-bosons using leptonic final states. We examine the effects of interference on distributions frequently used to determine mass limits for possible W'-bosons and show that there are important qualitative effects on the behaviour of the new physics signal. There are two main consequences. Firstly, exclusion limits where interferences effects have not been considered are likely to have been overestimated. Secondly, presenting experimental results as a function of a transverse mass cut rather than in terms of the contribution of new physics to the total cross-section would be more informative.

hep-ph↗

arXiv2011

W' production at the LHC in the 4-site Higgsless model

We study the phenomenology of the 4-site Higgsless model, based on the $SU(2)_L\times SU(2)_1\times SU(2)_2\times U(1)_Y$ gauge symmetry, at present colliders. The model predicts the existence of two neutral and four charged extra gauge bosons, Z1,Z2,W1,W2. In this paper, we focus on the charged gauge sector. We first derive limits on W1,W2-boson masses and couplings to SM fermions from direct searches at the Tevatron. We then estimate at the 7 TeV LHC the exclusion limits with the actual L=1 fb-1 and the discovery potential with the expected L=10 fb-1. In contrast to the minimal (or 3-site) Higgsless model which predicts almost fermiophobic extra gauge bosons, the next-to-minimal (or 4-site) Higgsless model recovers sizeable W1,W2-boson couplings to ordinary matter, expressing the non-fermiophobic multiresonance inner nature of extra-dimensional theories. Owing to this feature, we find that in one year from now the new heavy gauge bosons, W1 and W2, could be discovered in the final state with an electron and large missing transverse energy at the 7 TeV LHC for W1,W2-boson masses in the TeV region, depending on model parameters.

hep-ph↗

arXiv2011

Improved analysis of the bounds from the electroweak precision tests on the 4-site model

We present a new complete analysis of the electroweak precision observables within the recently proposed 4-site Higgsless model, which is based on the SU(2)_L x SU(2)_1 x SU(2)_2 x U(1)_Y gauge symmetry and predicts six extra gauge bosons, W_{1,2} and Z_{1,2}. Within the epsilon_i (i=1,2,3,b) parametrization, we compute for the first time the EWPT bounds via a complete numerical algorithm going beyond commonly used approximations. Both epsilon_{1,3} impose strong constraints. Hence, it is mandatory to consider them jointly when extracting EWPT bounds and to fully take in to account the correlations among the electroweak precison measurements. The phenomenological consequence is that the extra gauge bosons must be heavier than 250 GeV. Their couplings to SM fermions, even if bounded, might be of the same order of magnitude than the SM ones. In contrast to other Higgsless models, the 4-site model is not fermiophobic. The new gauge bosons could thus be discovered in the favoured Drell-Yan channel already during the present run of the LHC experiment.

hep-ph↗

arXiv2010

Z' physics with early LHC data

We discuss the prospects for setting limits on or discovering spin-1 $Z'$ bosons using early LHC data at 7 TeV. Our results are based on the narrow width approximation in which the leptonic Drell-Yan $Z'$ boson production cross-section only depends on the $Z'$ boson mass together with two parameters $c_u$ and $c_d$. We carefully discuss the experimental cuts that should be applied and tabulate the theoretical next-to-next-to-leading order corrections which must be included. Using these results the approach then provides a safe, convenient and unbiased way of comparing experiment to theoretical models which avoids any built-in model dependent assumptions. We apply the method to three classes of perturbative $Z'$ boson benchmark models: $E_6$ models, left-right symmetric models and sequential standard models. We generalise each class of model in terms of {mixing angles which continuously parametrize} linear combinations of pairs of generators and lead to distinctive orbits in the $c_u-c_d$ plane. We also apply this method to the strongly coupled four-site benchmark model in which two $Z'$ bosons are predicted. By comparing the experimental limits or discovery bands to the theoretical predictions on the $c_u$-$c_d$ plane, we show that the LHC at 7 TeV with integrated luminosity of 500 pb$^{-1}$ will greatly improve on current Tevatron mass limits for the benchmark models. If a $Z'$ is discovered our results show that measurement of the mass and cross-section will provide a powerful discriminator between the benchmark models using this approach.

hep-ph↗

arXiv2010

Z' production at the LHC in the four-site Higgsless model

We study the phenomenology of the neutral gauge sector of the four-site Higgsless model, based on the SU(2)_L x SU(2)_1 x SU(2)_2 x U(1)_Y gauge symmetry, at present colliders. The model predicts the existence of two neutral and four charged extra gauge bosons, Z_{1,2} and W^\pm_{1,2}. We expand and update a previous study, by concentrating on the neutral sector. We derive new limits on Z_{1,2}-boson masses and couplings from recent direct searches at the Tevatron. We moreover estimate the discovery potential at the Tevatron with a project luminosity L=10 fb^{-1}, and at the 7 TeV LHC with L=1 fb^{-1}. In contrast to other Higgsless theories characterized by almost fermiophobic extra gauge bosons, the four-site model allows sizeable Z_{1,2}-boson couplings to SM fermions. Owing to this feature, we find that in the next two years the extra Z_{1,2}-bosons could be discovered in the favoured Drell-Yan channel at the 7 TeV LHC for Z_{1,2} masses in the TeV region, depending on model parameters.

hep-ph↗