S. De Curtis - INFN, Firenze, Italy

S. De Curtis
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Name
S. De Curtis
Affiliation
INFN, Firenze, Italy
City
Firenze
Country
Italy

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High Energy Physics - Phenomenology (50)
 
High Energy Physics - Experiment (6)
 
High Energy Physics - Theory (3)

Publications Authored By S. De Curtis

The model proposed by Georgi and Machacek enables the Higgs sector to involve isospin triplet scalar fields while retaining a custodial $SU(2)_V$ symmetry in the potential and thus ensuring the electroweak $\rho$ parameter to be one at tree level. This custodial symmetry, however, is explicitly broken by loop effects of the $U(1)_Y$ hypercharge gauge interaction. In order to make the model consistent at high energies, we construct the most general form of the Higgs potential without the custodial symmetry, and then we derive the one-loop $\beta$-functions for all the model parameters. Read More

We investigate single- and double-$h$, the discovered Standard Model (SM)-like Higgs boson, production at future $e^+e^-$ colliders in Composite 2-Higgs Doublet Models (C2HDMs) and Elementary 2-Higgs Doublet Models (E2HDMs) with a softly-broken $Z_2$ symmetry. We first survey their parameter spaces allowed by theoretical bounds from perturbative unitarity and vacuum stability as well as by future data at the Large Hadron Collider (LHC) with an integrated luminosity up to 3000 fb$^{-1}$ under the assumption that no new Higgs boson is detected. We then discuss how different the cross sections can be between the two scenarios when $\kappa_V^{}$, the $hVV$ ($V=W^\pm,Z$) coupling normalised to the SM value, is taken to be the same value in the both scenario We find that if $\kappa_V^2$ is found to be, e. Read More

In this talk, we report unitarity constraints and phenomenological studies at the Large Hadron Collider for the extra Higgs bosons of a Composite 2-Higgs Doublet Model. Read More

We investigate the phenomenology of Composite 2-Higgs Doublet Models (C2HDMs) of various Yukawa types based on the global symmetry breaking $SO(6)\to SO(4)\times SO(2)$. The kinetic term and the Yukawa Lagrangian are constructed in terms of the pseudo Nambu-Goldstone Boson (pNGB) matrix and a 6-plet of fermions under $SO(6)$. The scalar potential is assumed to be the same as that of the Elementary 2-Higgs Doublet Model (E2HDM) with a softly-broken discrete $Z_2$ symmetry. Read More

We study confining gauge theories with fermions vectorial under the SM that produce a Higgs doublet as a Nambu-Goldstone boson. The vacuum misalignment required to break the electro-weak symmetry is induced by an elementary Higgs doublet with Yukawa couplings to the new fermions. The physical Higgs is a linear combination of elementary and composite Higgses while the SM fermions remain elementary. Read More

A summary is presented of the workshop "top physics at linear colliders" that was held at IFIC Valencia from the 30th of June to the 3rd July 2015. We present an up-to-date status report of studies into the potential for top quark physics of lepton colliders with an energy reach that exceeds the top quark pair production threshold, with a focus on the linear collider projects ILC and CLIC. This summary shows that such projects can offer very competitive determinations of top quark properties (mass, width) and its interactions with other Standard Model particles, in particular electroweak gauge bosons and the Higgs boson. Read More

We study bounds from perturbative unitarity in a Composite 2-Higgs Doublet Model (C2HDM) based on the spontaneous breakdown of a global symmetry $SO(6)\to SO(4)\times SO(2)$ at the compositeness scale $f$. The eight pseudo Nambu-Goldstone Bosons (pNGBs) emerging from such a dynamics are identified as two isospin doublet Higgs fields. We calculate the $S$-wave amplitude for all possible 2-to-2-body elastic (pseudo)scalar boson scatterings at energy scales $\sqrt{s}$ reachable at the Large Hadron Collider (LHC) and beyond it, including the longitudinal components of weak gauge boson states as the corresponding pNGB states. Read More

The Drell-Yan di-lepton production at hadron colliders is by far the preferred channel to search for new heavy spin-1 particles. Traditionally, such searches have exploited the Narrow Width Approximation (NWA) for the signal, thereby neglecting the effect of the interference between the additional Z'-bosons and the Standard Model Z and {\gamma}. Recently, it has been established that both finite width and interference effects can be dealt with in experimental searches while still retaining the model independent approach ensured by the NWA. Read More

The study of the top quark properties will be an integral part of any particle physics activity at future leptonic colliders. In this proceeding we discuss the possibility of testing composite Higgs scenarios at $e^+e^-$ prototypes through deviations from the Standard Model predictions in $t\bar t$ production observables for various centre of mass energies, ranging from 370 GeV up to 1 TeV. This proceedings draws from Ref. Read More

Searches for Z' bosons are most sensitive in the dilepton channels at hadron colliders. Whilst finite width and interference effects do affect the modifications the presence of BSM physics makes to Standard Model (SM) contributions, generic searches are often designed to minimize these. The experimental approach adopted works well in the case of popular models that predict a single and narrow Z' boson allowing these effects to effectively be neglected. Read More

We test the sensitivity of a future e+e- collider to composite Higgs scenarios encompassing partial compositeness. Besides the detailed study of the Higgs properties, such a machine will have a rich top-quark physics programme mainly in two domains: top property accurate determination at the $t \bar t$ production threshold and search for New Physics with top quarks above it. In both domains, a composite Higgs scenario can manifest itself via sizable deviations in both cross-section and asymmetry observables. Read More

The top quark plays a central role in many New Physics scenarios and in understanding the details of Electro-Weak Symmetry Breaking. In the short- and mid-term future, top-quark studies will mainly be driven by the experiments at the Large Hadron Collider. Exploration of top quarks will, however, be an integral part of particle physics studies at any future facility and an $e^+ e^-$ collider will have a very comprehensive top-quark physics program. Read More

We examine a simple Composite Higgs Model (CHM) with vector resonances in addition to the Standard Model (SM) fields in perturbation theory by using the $K$-matrix method to implement unitarity constraints. We find that the $W_LW_L$ scattering amplitude has an additional scalar pole (analogous to the $\sigma$ meson of QCD) as in generic strongly interacting extensions of the SM. The mass and width of this dynamically generated scalar resonance are large and the mass behaves contrary to the vector one, so that when the vector resonance is lighter, the scalar one is heavier, and vice versa. Read More

General Composite Higgs models provide an elegant solution to the hierarchy problem present in the Standard Model and give an alternative pattern leading to the mechanism of electroweak (EW) symmetry breaking. We present an analysis of a realistic realization of this general idea, namely the 4DCHM, analysing the Higgs production and decay modes, fitting them to the latest LHC showing the compatibility with the results of the CERN machine. We then present the prospects of a future electron positron collider of testing this model against the expected experimental accuracies in the various Higgs decay channels accessible herein. Read More

We compute the correction to the muon magnetic moment in theories where the Higgs is a pseudo-Goldstone boson and leptons are partially composite. Using a general effective lagrangian we show that in some regions of parameters a sizable new physics contribution to the magnetic moment can be obtained from composite fermions that could explain the 3.5$\sigma$ experimental discrepancy from the Standard Model prediction. Read More

In this paper we present an analysis strategy and a dedicated tool to determine the exclusion confidence level for any scenario involving multiple heavy extra quarks with generic decay channels, as predicted in several extensions of the Standard Model. We have created, validated and used a software package, called XQCAT (eXtra Quark Combined Analysis Tool), which is based on publicly available experimental data from direct searches for top partners and from Supersymmetry inspired searches. By means of this code, we recast the limits from CMS on new heavy extra quarks considering a complete set of decay channels. Read More

We introduce a general parametrisation for theories where the Higgs is a Goldstone boson that encompasses all existing models. Our construction deviates from extra-dimensional or deconstructed theories through the inclusion of "non-local" interactions in theory space. These terms are necessary to reproduce the most general 4D effective lagrangian compatible with the symmetries. Read More

In this proceeding, we extend a previous analysis concerning the prospects of a future electron-positron collider in testing the 4-Dimensional Composite Higgs Model. In particular, we introduce two motivated benchmarks and study them in Higgs-Strahlung, for three possible energy stages and different luminosity options of such a machine and confront our results to the expected experimental accuracies in the various accessible Higgs decay channels. Read More

In this note we analyse the prospects of a future electron-positron collider in testing a particular realisation of a composite Higgs model encompassing partial compositeness, namely, the 4-Dimensional Composite Higgs Model. We study the main Higgs production channels for three possible energy stages and different luminosity options of such a machine and confront our results to the expected experimental accuracies in the various Higgs decay channels accessible herein and, for comparison, also at the Large Hadron Collider. Read More

This discovery of the Higgs boson last year has created new possibilities for testing candidate theories for explaining physics beyond the Standard Model. Here we explain the ways in which new physics can leave its marks in the experimental Higgs data, and how we can use the data to constrain and compare different models. In this proceedings paper we use two models, Minimal Universal Extra Dimensions and the 4D Composite Higgs model, as examples to demonstrate the technique. Read More

Composite Higgs models provide an elegant solution to the hierarchy problem present in the Standard Model (SM) and give an alternative pattern leading to the mechanism of Electro-Weak Symmetry Breaking (EWSB). We present an analysis of the Higgs boson production and decay within a recently proposed realistic realization of this general idea: the 4D Composite Higgs Model (4DCHM). Comparing our results with the latest Large Hadron Collider (LHC) data we show that the 4DCHM could provide an alternative explanation with respect to the SM of the LHC results pointing to the discovery of a Higgs-like particle at 125 GeV. Read More

We study the phenomenology of both the Neutral Current (NC) and Charged Current (CC) Drell-Yan (DY) processes at the Large Hadron Collider (LHC) within a 4 Dimensional realization of a Composite Higgs model with partial compositness by estimating the integrated and differential event rates and taking into account the possible impact of the extra fermions present in the spectrum. We show that, in certain regions of the parameters space, the multiple neutral resonances present in the model can be distinguishable and experimentally accessible in the invariant or transverse mass distributions. Read More

In this proceeding, we present the current status of a $\chi^2$ fit extracted from the profiling of the Higgs couplings performed at the LHC in the context of the 4-Dimensional Composite Higgs Model. Especially, we consider the data presented by the ATLAS and CMS collaborations during the XLVIII Rencontres de Moriond. Read More

We present an analysis of both the Neutral Current (NC) and Charged Current (CC) Drell-Yan processes at the LHC within a 4 Dimensional realization of a Composite Higgs model studying the cross sections and taking into account the possible impact of the extra fermions present in the spectrum. Read More

We explain the current Large Hadron Collider (LHC) data pointing to the discovery of a neutral Higgs boson in the context of a 4-Dimensional Composite Higgs Model (4DCHM). The full particle spectrum of this scenario is derived without any approximation and implemented in automated computational tools to enable fast phenomenological investigation. Several parameter configurations compliant with experimental constraints are presented and discussed. Read More

We show that the 4-Dimensional Composite Higgs Model (4DCHM) could provide an even better explanation than the Standard Model (SM) of the current Large Hadron Collider (LHC) data pointing to the discovery of a neutral Higgs boson. The full particle spectrum of this scenario is derived without any approximation and implemented in automated computational tools to enable fast phenomenological investigation. Several benchmark sets compliant with the aforementioned data are presented and discussed. Read More

We study the production of top-antitop pairs at the Large Hadron Collider as a testbed for discovering heavy Z' bosons belonging to a composite Higgs model, as, in this scenario, such new gauge interaction states are sizeably coupled to the third generation quarks of the Standard Model. We study their possible appearance in cross section as well as (charge and spin) asymmetry distributions. Our calculations are performed in the minimal four-dimensional formulation of such a scenario, namely the 4-Dimensional Composite Higgs Model (4DCHM), which embeds five new $Z'$s. Read More

We study di-boson production via both neutral and charged current at the Large Hadron Collider, i.e. subprocesses $q\bar q\to e^+\nu_e \mu^-\bar\nu_\mu$ + ${\rm{c. Read More

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. Read More

We study the phenomenology of Drell-Yan processes at the Large Hadron Collider for the case of both the neutral and charged current channels within a recently proposed 4-Dimensional formulation of the Minimal Composite Higgs Model. We estimate the integrated and differential event rates at the CERN machine, assuming 14 TeV and data samples of ${\cal O}(100 {\rm{fb}}^{-1})$, as at lower energy and/or luminosity event rates are prohibitively small. We pay particular attention to the presence of multiple resonances in either channel, by showing that in certain region of parameter space some of these can be distinguishable and experimentally accessible in the invariant and/or transverse mass distribution, sampled in either the cross section, the forward-backward asymmetry or both. Read More

We investigate the scope of the LHC in probing the parameter space of a 4-site model supplemented by one composite Higgs state, assuming all past, current and future energy and luminosity stages of the CERN machine. We concentrate on the yield of charged di-boson production giving two opposite-charge different-flavour leptons and missing (transverse) energy, i.e. Read More

We compare the phenomenology of two models, the so-called minimal Z' and an effective model for a SM-like Higgs realised as a composite state of a new strong interaction, at a multi-TeV linear collider in the hypothesis that the new physics is at a scale beyond the direct reach of the machine. Read More

We compare the phenomenology of two models, the so-called "minimal Z'" and an effective model an SM-like Higgs is realised as a composite state of a new strong interaction, at a multi-TeV linear collider in the hypothesis that the new physics is at a scale beyond the direct reach of the machine. Read More

We propose a four dimensional description of Composite Higgs Models which represents a complete framework for the physics of the Higgs as a pseudo-Nambu-Goldstone boson. Our setup captures all the relevant features of 5D models and more in general of composite Higgs models with partial compositeness. We focus on the minimal scenario where we include a single multiplet of resonances of the composite sector, as these will be the only degrees of freedom which might be accessible at the LHC. Read More

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. Read More

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. Read More

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. Read More

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. Read More

We study the phenomenological consequences of a four site Higgsless model based on the SU(2)_L x SU(2)_1 x SU(2)_2 x U(1)_Y gauge symmetry, which predicts two neutral and four charged extra gauge bosons, Z_{1,2} and W_{1,2}. The model represents an extension of the minimal three site version (or BESS model), largely investigated in the literature, which includes three heavy vector bosons. We compute the properties of the new particles, and derive indirect and direct limits on their masses and couplings from LEP and Tevatron data and from the perturbative unitarity requirements. Read More

We consider the continuum limit of a moose model corresponding to a generalization to N sites of the Degenerate BESS model. The five dimensional formulation emerging in this limit is a realization of a RS1 type model with SU(2)_L x SU(2)_R in the bulk, broken by boundary conditions and a vacuum expectation value on the infrared brane. A low energy effective Lagrangian is derived by means of the holographic technique and corresponding bounds on the model parameters are obtained. Read More

Discoveries at the LHC will soon set the physics agenda for future colliders. This report of a CERN Theory Institute includes the summaries of Working Groups that reviewed the physics goals and prospects of LHC running with 10 to 300/fb of integrated luminosity, of the proposed sLHC luminosity upgrade, of the ILC, of CLIC, of the LHeC and of a muon collider. The four Working Groups considered possible scenarios for the first 10/fb of data at the LHC in which (i) a state with properties that are compatible with a Higgs boson is discovered, (ii) no such state is discovered either because the Higgs properties are such that it is difficult to detect or because no Higgs boson exists, (iii) a missing-energy signal beyond the Standard Model is discovered as in some supersymmetric models, and (iv) some other exotic signature of new physics is discovered. Read More

We consider a description of propagators for particle resonances which takes into account the quantum mechanical interference due to the width of two or more nearby states that have common decay channels, by incorporating the effects arising from the imaginary parts of the one-loop self-energies. Depending on the couplings to the common decay channels, the interference effect, not taken into account in the usual Breit-Wigner approximation, can significantly modify the cross section or make the more long-lived resonance narrower. We give few examples of New Physics models for which the effect is sizable, namely a generic two and multiple Higgs model and neutral vector resonances in Higgsless models. Read More

2008Jul
Affiliations: 1INFN, Florence, 2INFN, Florence, 3Florence U., 4Florence U.

We consider a four site Higgsless model based on the $SU(2)_L\times SU(2)_1\times SU(2)_2\times U(1)_Y$ gauge symmetry, which predicts two neutral and four charged extra gauge bosons, $Z_{1,2}$ and $W^\pm_{1,2}$. We compute the properties of the new particles, and derive indirect and direct limits on their masses and couplings from LEP and Tevatron data. In contrast to other Higgsless models, characterized by fermiophobic extra gauge bosons, here sizeable fermion-boson couplings are allowed by the electroweak precision data. Read More

2008Jul
Affiliations: 1Florence U. & INFN, Florence, 2Florence U. & INFN, Florence, 3Florence U. & INFN, Florence, 4Florence U. & INFN, Florence

We consider the four-site Higgsless model, which predicts the existence of four charged and two neutral extra gauge bosons, $W_{1,2}^\pm$ and $Z_{1,2}$. In contrast to other Higgsless models, characterized by fermiophobic extra gauge bosons, here sizeable fermion-boson couplings are allowed by the electroweak precision data. We thus analyse the prospects of detecting the new predicted particles in the mostly favored Drell-Yan channel at the LHC. Read More

We show how translational invariance can be broken by the vacuum that drives the spontaneous symmetry breaking of extra-dimensional extensions of the Standard Model, when delta-like interactions between brane and bulk scalar fields are present. We explicitly build some examples of vacuum configurations, which induce the spontaneous symmetry breaking, and have non trivial profile in the extra coordinate. Read More

The possibility of the existence of a strongly interacting electroweak symmetry breaking sector, as opposed to the weakly interacting light Higgs of the Standard Model, is not yet ruled out by experiments. In this paper we make an extensive study of a deconstructed model (or ``moose'' model) providing a possible effective description of such a strong symmetry breaking sector, and show its compatibility with experimental data for a wide portion of the model parameters space. The model is a direct generalization of the previously proposed D-BESS model. Read More

In this work, following an holographic approach, we carry out a low energy effective study of a minimal Higgsless model based on SU(2) bulk symmetry broken by boundary conditions, both in flat and warped metric. The holographic procedure turns out to be an useful computation technique to achieve an effective four dimensional formulation of the model taking into account the corrections coming from the extra dimensional sector. This technique is used to compute both oblique and direct contributions to the electroweak parameters in presence of fermions delocalized along the fifth dimension. Read More

2006Aug
Authors: S. Kraml, E. Accomando, A. G. Akeroyd, E. Akhmetzyanova, J. Albert, A. Alves, N. Amapane, M. Aoki, G. Azuelos, S. Baffioni, A. Ballestrero, V. Barger, A. Bartl, P. Bechtle, G. Belanger, A. Belhouari, R. Bellan, A. Belyaev, P. Benes, K. Benslama, W. Bernreuther, M. Besancon, G. Bevilacqua, M. Beyer, M. Bluj, S. Bolognesi, M. Boonekamp, F. Borzumati, F. Boudjema, A. Brandenburg, T. Brauner, C. P. Buszello, J. M. Butterworth, M. Carena, D. Cavalli, G. Cerminara, S. Y. Choi, B. Clerbaux, C. Collard, J. A. Conley, A. Deandrea, S. De Curtis, R. Dermisek, A. De Roeck, G. Dewhirst, M. A. Diaz, J. L. Diaz-Cruz, D. D. Dietrich, M. Dolgopolov, D. Dominici, M. Dubinin, O. Eboli, J. Ellis, N. Evans, L. Fano, J. Ferland, S. Ferrag, S. P. Fitzgerald, H. Fraas, F. Franke, S. Gennai, I. F. Ginzburg, R. M. Godbole, T. Gregoire, G. Grenier, C. Grojean, S. B. Gudnason, J. F. Gunion, H. E. Haber, T. Hahn, T. Han, V. Hankele, C. Hays, S. Heinemeyer, S. Hesselbach, J. L. Hewett, K. Hidaka, M. Hirsch, W. Hollik, D. Hooper, J. Hosek, J. Hubisz, C. Hugonie, J. Kalinowski, S. Kanemura, V. Kashkan, T. Kernreiter, W. Khater, V. A. Khoze, W. Kilian, S. F. King, O. Kittel, G. Klamke, J. L. Kneur, C. Kouvaris, M. Krawczyk, P. Krstonosic, A. Kyriakis, P. Langacker, M. P. Le, H. -S. Lee, J. S. Lee, M. C. Lemaire, Y. Liao, B. Lillie, V. Litvin, H. E. Logan, B. McElrath, T. Mahmoud, E. Maina, C. Mariotti, P. Marquard, A. D. Martin, K. Mazumdar, D. J. Miller, P. Mine, K. Moenig, G. Moortgat-Pick, S. Moretti, M. M. Muhlleitner, S. Munir, R. Nevzorov, H. Newman, P. Niezurawski, A. Nikitenko, R. Noriega-Papaqui, Y. Okada, P. Osland, A. Pilaftsis, W. Porod, H. Przysiezniak, A. Pukhov, D. Rainwater, A. Raspereza, J. Reuter, S. Riemann, S. Rindani, T. G. Rizzo, E. Ros, A. Rosado, D. Rousseau, D. P. Roy, M. G. Ryskin, H. Rzehak, F. Sannino, E. Schmidt, H. Schroder, M. Schumacher, A. Semenov, E. Senaha, G. Shaughnessy, R. K. Singh, J. Terning, L. Vacavant, M. Velasco, A. Villanova del Moral, F. von der Pahlen, G. Weiglein, J. Williams, K. Williams, A. F. Zarnecki, D. Zeppenfeld, D. Zerwas, P. M. Zerwas, A. R. Zerwekh, J. Ziethe

There are many possibilities for new physics beyond the Standard Model that feature non-standard Higgs sectors. These may introduce new sources of CP violation, and there may be mixing between multiple Higgs bosons or other new scalar bosons. Alternatively, the Higgs may be a composite state, or there may even be no Higgs at all. Read More