Search

Majorana neutrinos may have transitional dipole moments, which violate lepton number as well as lepton flavour. We estimate the sensitivity of future colliders to the electron-muon neutrino dipole moment, $\lambda_{e\mu}$, by considering same-sign dilepton final states. We find that hadron colliders, even the proposed FCC-hh upgrade, are sensitive only to $|\lambda_{e\mu}|\gtrsim 10^{-9}\mu_B$ (with $\mu_B$ the Bohr magneton), a value two-three orders of magnitude larger than current bounds from astrophysics and low-energy neutrino-scattering experiments. In the case of a future muon collider, we show that the sensitivity varies from $|\lambda_{e\mu}|\sim 5\cdot 10^{-9}\mu_B$ for energy $\sqrt{s}\simeq 3$ TeV, to $\sim 10^{-12}\mu_B$ for $\sqrt{s}\simeq 50$ TeV, matching the current laboratory bounds for $\sqrt{s}\simeq 30$ TeV. The singular advantage of the muon collider signal would be a direct, clean identification of lepton number and flavour violation. We also show that a muon collider would improve by orders of magnitude the direct bounds on $m_{e\mu}$ and $m_{\mu\mu}$, two of the entries of the Majorana neutrino mass matrix. These bounds could be as strong as $\sim 50$ keV, still far above the neutrino mass scale., Comment: 22 pages, 12 figures, 5 tables

We re-consider recent measures of $R_{K}$ and $R_{K^*}$, now compatible with the Standard Model expectations, as well as the results for the process $\text{BR}(B_s \rightarrow \mu^+ \mu^-)$ alongside earlier determinations of $R_{D^{(\ast)}}$ and $\text{BR}(B_c \rightarrow \tau \nu)$. We provide analytic constraints on the associated Wilson coefficients in both the $b \to s$ and the $b \to c$ sectors. These allow us to estimate the scale of potential New Physics for generic extensions of the Standard Model. We then use the results to constrain the leptoquark landscape., Comment: 39 pages, 5 figures

Despite being remarkable predictive, the Standard Model leaves unanswered several important issues, which motivate an ongoing search for its extensions. One fashionable possibility are the so-called 331 models, where the electroweak gauge group is extended to $SU_L(3)\times U(1)$. We focus on a minimal extension which includes vector-like quarks (VLQs) and new gauge bosons, performing a consistent analysis of the production at LHC of a pair of doubly-charged bileptons. We include for the first time all the relevant processes where VLQs contribute, and in particular the associate production VLQ-bilepton. Finally, we extract the bound on the bilepton mass, $m_Y>$ 1300 GeV, from a reinterpretation of a recent ATLAS search for doubly-charged Higgs bosons in multi-lepton final states., Comment: v2: several improvements, results unchanged

The $\tau$ lepton anomalous magnetic moment: $a_\tau = \frac{g_{\tau}-2}{2}$ was measured, so far, with a precision of only several percents despite its highly sensitivity to physics beyond the Standard Model such as compositeness or Supersymmetry. A new study is presented to improve the sensitivity of the $a_\tau $ measurement with photon-photon interactions from ultra-peripheral lead-lead collisions at LHC. The theoretical approach used in this work is based on an effective Lagrangian and on a photon flux implemented in the MadGraph5 Monte Carlo simulation. Using a multivariate analysis to discriminate the signal from the background processes, a sensitivity to the anomalous magnetic moment $\rm{a_{\tau}}$ = 0 $_{+0.011} ^{-0.019}$ is obtained at 95\% CL with a dataset corresponding to an integrated luminosity of 2 nb$^{-1}$ of lead-lead collisions and assuming a conservative 10\% systematic uncertainty. The present results are compared with previous calculations and available measurements., Comment: 35 pages, 17 Figures Added minor changes on text and some references

A multi-TeV muon collider proves to be very efficient not only for the search for new heavy neutral particles, but also for the discovery of charged bosons of the $W^\prime$ type. We find that, by analyzing the associated production with a Standard Model W, charged resonances can be probed directly up to multi-TeV mass values close to the collision energy, and for very small couplings with the SM fermions, of the order of $10^{-3}-10^{-4}$ times the SM weak coupling. Additionally, charged bound states of WIMP Minimal Dark Matter, specifically a Majorana fermionic 5-plet, can be discovered with low statistics by running above the kinematic threshold, at a center-of-mass energy just slightly above the mass of the MDM bound state. This opens up a very interesting possibility for the discovery of WIMPs, complementary to the search for the resonant production of the neutral MDM bound state component, which relies on an on-peak search. For 5-plet MDM, indeed, the proposed search strategy is more efficient than the WIMP searches based on mono-X, missing-mass and disappearing tracks signatures., Comment: v3: minor improvements, matches version to appear in JHEP

We discuss as accurately as possible the cross section of quasi-elastic scattering of electron (anti-)neutrinos on nucleons, also known as inverse beta decay in the case of antineutrinos. We focus on the moderate energy range from a few MeV up to hundreds of MeV, which includes neutrinos from reactors and supernovae. We assess the uncertainty on the cross section, which is relevant to experimental advances and increasingly large statistical samples. We estimate the effects of second-class currents, showing that they are small and negligible for current applications., Comment: v2: minor improvements (numerical values of the cross section added), version accepted for publication in JHEP

We review the present status and the future prospects for the measurements of the Higgs Yukawa couplings to light quarks and charm. A special focus is given to novel proposed off-shell probes, which offer promising and complementary opportunities to test light quark Yukawas in triboson final states. Additionally, a new off-shell strategy to test the charm Yukawa coupling in the final state with two bosons plus a charm and a jet is considered. First estimates for the HL-LHC and the FCC-hh sensitivities on the channel are presented, showing encouraging results., Comment: v2: minor changes; references added; matches version published in Symmetry-mdpi

We critically analyze the body of results that hints to the existence of New Physics from possible violations of lepton universality observed by the LHCb experiment in the $\mu/e$ ratios $R_{K}$ and $R_{K^*}$ to the $g-2$ lepton anomalies. The analysis begins with a theoretical, in depth, study of the $\mu/e$ ratios $R_{K}$ and $R_{K^*}$ as well as the process $B_s \rightarrow \mu^+ \mu^-$. Here we consider the impact of complex Wilson coefficients and derive constraints on their imaginary and real parts. We then move to a comprehensive comparison with experimental results. We show that, by fitting a single Wilson coefficient, the deviations from the Standard Model are at the $4.7\sigma$ level when including only the hadronic insensitive observables while it increases to $6.1\sigma$ when including also the hadronic sensitive ones. When switching on all relevant Wilson coefficients and combining both hadronic sensitive and insensitive data into the fit, the deviation from the Standard Model peaks at $7.2\sigma$ and decreases at the $4.9\sigma$ level if we assume that the central values of $R_K$ and $R_{K^{\ast}}$ are taken to be unity. We further estimate other unaccounted for SM contributions and show that their inclusion still requires New Physics to fit the data. We then introduce the $g-2$ lepton anomalies as well as the most recent $W$-mass results. Different theoretical models are considered that can explain the discrepancies from the Standard Model. In the final part of our work we estimate the impact of the forthcoming data from LHCb (coming from LHC Run3) and Belle II, when it will have accumulated about $5~ab^{-1}$., Comment: Final version to match the published one. References added, improved world average of the W-mass, long distance effects discussion improved for the hadronic sensitive observables

We explore a new mechanism for reproducing the Dark Matter (DM) abundance: scatterings of one DM particle on light Standard Model particles. Strong bounds on its decays can be satisfied if DM undergoes freeze-in and has a mass around or below the pion mass. This happens, for example, in theories with a right-handed neutrino interacting with charged fermions through a leptoquark exchange. These leptoquarks can be linked to the ones motivated by the B-physics anomalies if assumptions about the flavour structure are made. DM signals are unusual, with interesting possibilities for direct and indirect detection. Achieving thermal freeze-out instead requires models with more than one DM flavour, and couplings parametrically smaller than what needed by the usual pair annihilations., Comment: 27 pages + appendices, 8 figures, 1 table; Some clarifications and references added, conclusion unchanged. Matching published version on JHEP

The hypothesis that Dark Matter is one electroweak multiplet leads to predictive candidates with multi-TeV masses that can form electroweak bound states. Bound states with the same quantum numbers as electroweak vectors are found to be especially interesting, as they can be produced resonantly with large cross sections at lepton colliders. Such bound states exist e.g. if DM is an automatically stable fermionic weak 5-plet with mass $M \approx$ 14 TeV such that the DM abundance is reproduced thermally. In this model, a muon collider could resolve three such bound states. Production rates are so large that details of DM spectroscopy can be probed with larger statistics: we compute the characteristic pattern of single and multiple $\gamma$ lines., Comment: v2, to appear on JHEP

Triple heavy vector boson production, $p p \to VVV$ $(V = W, Z)$, has recently been observed for the first time. We propose that precision measurements of this process provide an excellent probe of the first generation light quark Yukawa couplings. Modified quark interactions with the off-shell Higgs in this process lead to a rapid growth of the partonic cross sections with energy, which manifests in an enhanced $p_T$ distribution of the final state leptons and quarks. We quantify this effect and estimate the present and future 2$\sigma$ sensitivity to the up, down, and strange Yukawas. In particular, we find that HL-LHC can reach $\mathcal{O}(400)$ sensitivity to the down Yukawa relative to the Standard Model value, improving the current sensitivity in this process by a factor of $10$, and which can be further improved to $\mathcal{O}(30)$ at FCC-hh. This is competitive with and complementary to constraints from global fits and other on-shell probes of the first generation Yukawas. The triboson sensitivity at HL-LHC corresponds to probing dimension-6 SMEFT operators suppressed by an $\mathcal{O}(1)$ TeV scale, similarly to other LHC Higgs probes., Comment: 22 pages, 6 figures

We report on the status of efforts to improve the reinterpretation of searches and measurements at the LHC in terms of models for new physics, in the context of the LHC Reinterpretation Forum. We detail current experimental offerings in direct searches for new particles, measurements, technical implementations and Open Data, and provide a set of recommendations for further improving the presentation of LHC results in order to better enable reinterpretation in the future. We also provide a brief description of existing software reinterpretation frameworks and recent global analyses of new physics that make use of the current data., Comment: 58 pages, minor revision following comments from SciPost referees

I will review simplified models with leptoquarks, which can explain recent anomalies in $B$-meson physics, and I will indicate the High-Luminosity LHC prospects for testing these theories, with a special focus to the efficient channel of pair leptoquark production in the $t\bar t$ plus missing energy final state., Comment: Presented at IFAE 2019, 8-10 April, Naples, Italy

The $t\bar t$ plus missing energy channel is one of the most efficient to detect third-generation leptoquarks (LQs). It offers an important test to models which explain flavor anomalies in $B$ meson decays. We outline a search strategy in the channel, relying on tagging the tops and on observables constructed out of the tops, and we assess the reach on LQs of the future high-luminosity LHC program. We find that with 3 ab$^{-1}$ a vector (scalar) LQ decaying 50% (100%) to top and neutrino can be excluded up to masses of 1.96 TeV (1.54 TeV). We also indicate several observables that, in case of a future discovery in the channel, can be used to distinguish a scalar LQ from a vector LQ. The implications of our findings to models addressing the recent flavor anomalies are finally discussed., Comment: 19 pages, 8 figures. Matches version to appear in Physical Review D

In composite Higgs models, new composite pseudoscalars can interact with the Higgs and with electroweak gauge bosons via anomalous interactions, which stem from the topological structure of the underlying theory. A future 100 TeV pp collider (FCC-pp) will be able to test these anomalous interactions and thus shed light on the strong dynamics which generates the Higgs and other composite resonances. We will discuss the topological interactions of a minimal composite Higgs model with fermionic ultraviolet completion, based on the coset SU(4)/Sp(4). We will indicate the strategy to test these interactions at the FCC-pp and the expected reach., Comment: 5 pages, 3 figures, to appear in the Proceedings of the EPS Conference on High Energy Physics (EPS-HEP), Venice, July 2017

We review the current status of searches for new physics beyond the Standard Model in the diphoton channel at the LHC and estimate the reach with future collected data. We perform a model independent analysis based on an effective field theory approach and different production mechanisms. As an illustrative example, we apply our results to a scenario of minimal composite dynamics., Comment: 13 pages, 3 figures; invited review for MPLA; journal version

In models of composite Higgs dynamics new composite pseudoscalars can interact with the Higgs and electroweak gauge bosons via anomalous interactions, stemming from the topological sector of the underlying theory. We show that a future 100 TeV proton-proton collider (FCC-pp) will be able to test this important sector and thus shed light on the strong dynamics which generates the Higgs and other composite states. To elucidate our results we focus on the topological interactions of a minimal composite Higgs model with a fermionic ultraviolet completion, based on the coset $\text{SU}(4)/\text{Sp}(4)$. We suggest the strategy to test these interactions at the FCC-pp and analyse the expected reach., Comment: 24 pages, 5 figures. Matches published version

Many compelling theories to address the Higgs hierarchy problem predict strong interactions between the top and a sector of New Physics. In minimal composite Higgs models (CHM), the top interactions with a BSM strongly-interacting sector give the leading contribution to trigger the EWSB and generate a light mass for the pseudo-NG Higgs. This implies that new composite states (vector-like top-partners, composite vector resonances, new composite scalars) dominantly interact with third-generation quarks and, when produced at colliders, generate top quarks in the final state. I will indicate interesting signatures involving top quarks for CHM discovery/test at the LHC and future colliders., Comment: Presented at TOP 2016

We analyze the Large Hadron Collider sensitivity to new pseudoscalar resonances decaying into diphoton with masses up to scales of few TeVs. We focus on minimal scenarios where the production mechanisms involve either photon or top-mediated gluon fusion, partially motivated by the tantalizing excess around 750 GeV reported by ATLAS and CMS. The two scenarios lead respectively to a narrow and a wide resonance. We first provide a model-independent analysis via effective operators and then introduce minimal models of composite dynamics where the diphoton channel is characterized by their topological sector. The relevant state here is the pseudoscalar associated with the axial anomaly of the new composite dynamics. If the Standard Model top mass is generated via four-fermion operators the coupling of this state to the top remarkably explains the wide-width resonance reported by ATLAS. Beyond the excess, our analysis paves the way to test dynamical electroweak symmetry breaking via topological sectors., Comment: 17 pages, 5 figures

ATLAS and CMS observe deviations from the expected background in the diphoton invariant mass searches of new resonances around 750 GeV. We show that a simple realization in terms of a new pseudoscalar state can accommodate the observations. The model leads to further footprints that can be soon observed. The new state can be interpreted both as an axion or as a {highly natural} composite state arising from minimal models of dynamical electroweak symmetry breaking. We further show how to disentangle the two scenarios. Beyond the possible explanation of the diphoton excess the results show that it is possible to directly test and constrain composite dynamics via processes stemming from its distinctive topological sector., Comment: 6 pages, Latex. Improved version with new figures and further details

A new heavy di-jet resonance could be discovered at the 14 TeV LHC. In this talk we present a strategy to reveal the nature of such a particle; in particular to discern whether it is a quark-antiquark (q qbar), quark-gluon (qg), or gluon-gluon (gg) resonance. The strategy is based on the study of the energy profiles of the two leading jets in the di-jet channel. Including statistical uncertainties in the signal and the QCD backgrounds, we show that one can distinguish between gg, qg, and q bar resonances; an evaluation of systematic uncertainties in the measurement of the jet energy profile will require a detailed detector study once sufficient 14 TeV di-jet data is in hand., Comment: 15 pages, contribution to Sakata Memorial KMI Workshop on "Origin of Mass and Strong Coupling Gauge Theories (SCGT15)", 3-6 March 2015, Nagoya University

Color-singlet and color-octet vector bosons predicted in theories beyond the Standard Model have the potential to be discovered as dijet resonances at the LHC. A color-singlet resonance that has leptophobic couplings needs further investigation to be distinguished from a color-octet one. In previous work, we introduced a method for discriminating between the two kinds of resonances when their couplings are flavor-universal, using measurements of the dijet resonance mass, total decay width and production cross-section. Here, we describe two extensions of that work. First, we broaden the method to the case where the vector resonances have flavor non-universal couplings, by incorporating measurements of the heavy-flavor decays of the resonance. Second, we apply the method to separating vector bosons from color-octet scalars and excited quarks., Comment: 15 pages, 5 figures, contribution to Sakata Memorial KMI Workshop on "Origin of Mass and Strong Coupling Gauge Theories (SCGT15)", 3-6 March 2015, Nagoya University

We present a first estimate of the reach of future pp colliders, the 14 TeV LHC and a futuristic 100 TeV pp collider, on a vector resonance, specifically a $W^{'}$, produced via weak-boson-fusion, and decaying dominantly into $tb$. The analysis is motivated by Composite Higgs, Randall-Sundrum and Little Higgs scenarios, which predict the existence of vector resonances with a large coupling to $W$ and $Z$ longitudinal bosons. In particular, in composite Higgs models with partial compositeness, the standard Drell-Yan production channel is suppressed at large coupling while the weak-boson-fusion is enhanced and could thus provide a unique opportunity to directly test the large coupling regime of the theory. We outline a search strategy for the $W^{'}$ in the weak-boson-fusion channel and present the reach of future colliders on the $W^{'}$ mass-coupling parameter space., Comment: v2: References added. v3: matches version published in JHEP

A 3 sigma excess has been recently announced by ATLAS in events with Z-peaked dilepton pairs, jets, and large transverse missing energy. We interpret this finding in the context of composite Higgs / RS theories. We find that composite Higgs theories with custodial symmetry protection to the $Zb\bar{b}$ coupling predict a significant contribution to $ZZbb$ (and to $hhbb$) final states coming from heavy gluon decays to pairs of bottom-partner vector-like quarks. The heavy gluon to vector-like quarks signal is largely accepted by the ATLAS selection if one of the $Z$ boson in the $ZZbb$ final state decays leptonically and the other to neutrinos. For a bottom partner of $\sim$900 GeV, we find that the ATLAS excess can be reproduced by composite Higgs models, in an experimentally allowed parameter space, for heavy gluon masses roughly in a range 1.87 - 2.15 TeV and for heavy gluon couplings to light quarks within $\sim(0.3-0.65) g_S$. We briefly discuss the implication of this result for future experimental tests., Comment: 23 pp. v2: minor changes, references added

Anticipating that a di-jet resonance could be discovered at the 14 TeV LHC, we present two different strategies to reveal the nature of such a particle; in particular to discern whether it is a quark-antiquark (qqbar), quark-gluon (qg), or gluon-gluon (gg) resonance. The first method relies on the color discriminant variable, which can be calculated at the LHC from the measurements of the di-jet signal cross section, the resonance mass and the resonance width. Including estimated statistical uncertainties and experimental resolution, we show that a qg excited quark resonance can be efficiently distinguished from either a qqbar coloron or a gg color-octet scalar using the color discriminant variable at LHC-14. The second strategy is based on the study of the energy profiles of the two leading jets in the di-jet channel. Including statistical uncertainties in the signal and the QCD backgrounds, we show that one can distinguish, in a model-independent way, between gg, qg, and qqbar resonances; an evaluation of systematic uncertainties in the measurement of the jet energy profile will require a detailed detector study once sufficient 14 TeV di-jet data is in hand., Comment: 25 pages, 17 figures; references added. Minor clarifications and footnote(s) added, based on referee suggestions

The single top quark final state provides sensitivity to new heavy resonances produced in proton-proton collisions at the Large Hadron Collider. Particularly, the single top plus quark final state appears in models with heavy charged bosons or scalars, or in models with flavor-changing neutral currents involving the top quark. The cross sections and final state kinematics distinguish such models from each other and from standard model backgrounds. Several models of resonances decaying to a single top quark final state are presented and their phenomenology is discussed., Comment: submitted to Phys. Rev. D

We study the $W^{'}$ phenomenology in composite Higgs/ warped extra dimensional models focusing on the effect of fermionic resonances at $\sim$1 TeV. After deriving the existing bounds from the current LHC-8 analyses, we highlight the most promising signatures for $W^{'}$ discovery at the 14 TeV LHC. We find in particular very promising the study of $W^{'}$ decay modes into vector-like top partners, specifically the decay into a doublet of custodian heavy fermions, $T_{5/3} T_{2/3}$, and the decay into a heavy fermion plus a Standard Model quark. We perform a detailed parton level analysis of the channel $W^{'}\to T_{5/3} T_{2/3}$ in the same-sign dilepton final state, finding that it is a very promising signature to test the region at high $W^{'}$ mass, $m_{W^{'}}\gtrsim 2$ TeV, and of the $W^{'}\to Tb$ mode, that is one of the best channels to test the intermediate $W^{'}$ mass region and that, already with the LHC-8 data, could extend the present exclusion bounds., Comment: 25 pp. v2: minor changes, references added, version to appear in Phys. Rev. D

In this note we consider the sensitivity of the Large Hadron Collider (LHC) to the single production of new heavy vector-like quarks. We consider a model with large mixing with the standard model top quark with electroweak production of single heavy top quarks. We consider center of mass energies of 14, 33, and 100 TeV with various pileup scenarios and present the expected sensitivity and exclusion limits.

In this paper we study the phenomenology of color-octet and color-singlet scalars in the flavorful Top-Coloron model. We discuss the relevant production mechanisms at hadron colliders and the dominant decay modes, highlighting the most promising signatures for discovery, and derive bounds on the masses of the new scalars from LHC and Tevatron data. Of particular interest is the case in which color-octet scalars are pair produced and each decay to t cbar or tbar c, leading to a same-sign-dilepton final state. LHC data places a lower limit of 440 GeV on the octet mass in this scenario. The case of an octet lighter than the top, where the octet only decays into jets, has been tested by the Tevatron, which excludes the mass region from 50 to 125 GeV. The 8 TeV LHC is not yet sensitive to the observation of the color-singlet states, which are produced at rates much smaller than the octets. Nevertheless, the color-singlet pseudoscalar can be discovered at the 14 TeV LHC by analyzing the channel where it is produced from the decay of a color-octet vector boson., Comment: 21 pages. Included scalar decay to off-shell t and c, and added results from ATLAS four-jet resonance search

We present a new tool for precision measurements of the Higgs boson production mechanisms at the LHC. We study events with a Higgs boson produced with two forward jets. Even with fairly stringent cuts, one expects a significant contamination of gluon fusion (GF) in addition to vector-boson fusion (VBF) in the event sample. By measuring the jet energy profile of the most central jet, we find that SM production can be distinguished from either pure VBF or pure GF at the $5\sigma$ level with 100 fb$^{-1}$ of luminosity at the 14 TeV LHC. Moreover, this discrimination technique can be used to validate or rule out new physics models that predict similar observable branching fractions as the 125 GeV SM Higgs but have different production mechanisms., Comment: 12 pages, 8 figures

This talk discusses the possibility of new physics within the strong gauge interactions, specifically the idea of an extended color gauge group that is spontaneously broken to QCD. After a brief review of the literature, three of our recent pieces of work on coloron phenomenology are summarized. First, some key results on coloron production to NLO at hadron colliders are described. Next, a method of using associated production of colorons and weak vector bosons to better determine coloron couplings is discussed. Finally, a new model that naturally realizes flavor physics is reviewed., Comment: 15 pages; 5 figures; contribution to SCGT12 "KMI-GCOE Workshop on Strong Coupling Gauge Theories in the LHC Perspective", 4-7 Dec. 2012, Nagoya University; new version fixes several minor text typos (including in one reference)

In this paper we introduce a simple renormalizable model of an extended color gauge sector in which the third-generation quarks couple differently than the lighter quarks. In addition to a set of heavy color-octet vector bosons (colorons), the model also contains a set of heavy weak vector quarks. Mixing between the third-generation of quarks and the first two is naturally small, and occurs only through the (suppressed) mixing of all three generations with the heavy vector quarks. We discuss the constraints on this model arising from limits on flavor-changing neutral currents and from collider searches for the colorons and vector quarks, and discuss the prospects for discovery at the LHC., Comment: 18 pages, 13 pdf included figures. Typos fixed, corresponds to published version

Top partners from a new strong sector can be discovered soon, at the 8 TeV LHC, by analyzing their single production, which exhibits a large enhancement in the cross section compared to the analogous productions of bottom partners and exotic quarks. We analyze the subsequent decay of the top partners into a 125 GeV Higgs. This channel proves to be very promising for both the discovery of top partners and a test of the Higgs sector. For a reference value $\lambda_{\tilde{T}}=3$ of the Higgs coupling to the top partner, we could have a discovery (observation) at the 8 TeV LHC, with 30 fb$^{-1}$, for top partner masses up to 760 (890) GeV. If the LHC and Tevatron excesses near 125 GeV are really due to a composite Higgs, naturalness arguments demand top partners below $\sim 1$ TeV. Our results highlight thus that the 8 TeV LHC already has a large sensitivity on probing the composite Higgs hypothesis. The LHC reach is even wider at $\sqrt{s}=14$ TeV. With $\lambda_{\tilde{T}}=3$ the LHC with 100 fb$^{-1}$ can observe (at 5$\sigma$) a Higgs from a top partner decay for masses of this latter up to $\simeq 1450$ GeV. In the case the top partner was as light as $\simeq 500$ GeV, the 14 TeV LHC would be sensitive to the measure of the $\lambda_{\tilde{T}}$ coupling in basically the full range $\lambda_{\tilde{T}}>1$ predicted by the theory., Comment: 9 pp. Minor changes. Version to appear in PRD. arXiv admin note: substantial text overlap with arXiv:1204.0468

A possible composite nature of the Higgs could be revealed at the early stage of the LHC, by analyzing the channels where the Higgs is produced from the decay of a heavy fermion. The Higgs production from a singly-produced heavy bottom, in particular, proves to be a promising channel. For a value \lambda=3 of the Higgs coupling to a heavy bottom, for example, we find that, considering a 125 GeV Higgs which decays into a pair of b-quarks, a discovery is possible at the 8 TeV LHC with 30 fb^{-1} if the heavy bottom is lighter than roughly 530 GeV (while an observation is possible for heavy bottom masses up to 650 GeV). Such a relatively light heavy bottom is realistic in composite Higgs models of the type considered and, up to now, experimentally allowed. At \sqrt{s}=14 TeV the LHC sensitivity on the channel increases significantly. With \lambda=3 a discovery can occur, with 100 fb^{-1}, for heavy bottom masses up to 1040 GeV. In the case the heavy bottom was as light as 500 GeV, the 14 TeV LHC would be sensitive to the measure of the \lambda\ coupling in basically the full range \lambda>1 predicted by the theory., Comment: 25 pp. v2: Minor changes. v3: Version accepted for publication in JHEP. v4: typos fixed

We analyze the bounds on the spectrum of composite Higgs models (CHM) that come from flavor observables, by means of simple two-site effective Lagrangians, which incorporate a custodial symmetry and a Left-Right parity and which could also be adopted in further phenomenological studies on CHM. We derive, in particular, an important constraint on the masses of the $(t_L, b_L)$ partners, which does not depend on the flavor structure of the sector beyond the SM. This bound is obtained from the "infrared" contribution to $b \to s\gamma$ induced by the flavor-conserving effective vertex $Wt_Rb_R$. We find that the presence of a custodial symmetry can play a role in protecting this effective coupling and, as a consequence, in attenuating the constraint, which, however, remains of the order of 1 TeV. In addition to this bound, we calculate the constraints from the "ultraviolet" contribution to $b \to s \gamma$, induced by loops of heavy fermions, and to $\epsilon^{'}/\epsilon_K$., Comment: 35 pp. Version to appear in PRD

In this project we study the phenomenology of models where the Higgs is a bound state of a strongly interacting dynamics at the TeV scale and we assess the LHC potential to discover new heavy colored states. In the first part of the thesis we analyze the bounds on the spectrum of Composite Higgs Models (CHM) that come from flavor observables. In the second part we propose a novel strategy to discover a heavy gluon ($G^*$) and heavy fermions at the LHC. We do so by means of simple two-site effective Lagrangians, which could also be used in further phenomenological studies on CHM. From the analysis of the bounds on the CHM spectrum, we derive an important constraint on the masses of the heavy fermions which does not depend on the flavor structure of the sector beyond the SM. This bound is obtained from the infrared contribution to $b \to s\gamma$ induced by the flavor-conserving effective vertex $Wt_Rb_R$. We find that the presence of a custodial symmetry can play a role in protecting this effective coupling. Studying the heavy colored vectors phenomenology, we find that heavy composite fermions have a great impact on the phenomenology of heavy composite gluon at the LHC. If the composite gluon is heavier than the composite fermions, as flavor observables seem to suggest, the search in the channels where $G^*$ decays into one heavy fermion plus its Standard Model partner is very promising, with the possibility for both the $G^*$ and heavy fermions to be discovered at the early stage of the LHC. These channels offer also the possibility to extract important information on model's parameters, such as the top degree of compositeness., Comment: Ph.D. Thesis (Advisor: Roberto Contino). Dec 2011. 110 pp. Graduation date added. References added

We study the collider phenomenology of the lightest Kaluza-Klein excitation of the gluon, G*, in theories with a warped extra dimension. We do so by means of a two-site effective lagrangian which includes only the lowest-lying spin-1 and spin-1/2 resonances. We point out the importance of the decays of G* to one SM plus one heavy fermion, that were overlooked in the previous literature. It turns out that, when kinematically allowed, such heavy-light decays are powerful channels for discovering the G*. In particular, we present a parton-level Montecarlo analysis of the final state Wtb that follows from the decay of G* to one SM top or bottom quark plus its heavy partner. We find that at \sqrt{s} = 7 TeV and with 10 fb^{-1} of integrated luminosity, the LHC can discover a KK gluon with mass in the range M_{G*} = (1.8 - 2.2) TeV if its coupling to a pair of light quarks is g_{G*qqbar} = (0.2-0.5) g_3. The same process is also competitive for the discovery of the top and bottom partners as well. We find, for example, that the LHC at \sqrt{s} = 7 TeV can discover a 1 TeV KK bottom quark with an integrated luminosity of (5.3 - 0.61) fb^{-1} for g_{G*qqbar} = (0.2-0.5) g_3., Comment: 36 pages, 13 figures. v2: a few typos corrected, comments added, version published in JHEP

We perform a study of the LHC discovery reach on a heavy gluon (G*) and heavy fermions (top and bottom excitations), coming from a new composite sector. We find that heavy fermion resonances have a great impact on the composite gluon phenomenology. If the composite gluon is heavier than composite fermions, as flavor observables seem to suggest, the search in the channel where G* decays into a heavy fermion plus its Standard Model partner is very promising, with the possibility for both the G* and heavy fermions to be discovered at the early stage of the LHC. The channel offers also the possibility to extract important information on model parameters, such as the top degree of compositeness., Comment: Presented at IFAE 2011, Incontri di Fisica delle Alte Energie, Perugia, Italy, 27-29 April. 4 pages, 3 figures. References added

We analyze the decays to muons of a light dilaton produced via vector boson fusion at the LHC. We investigate models in which the electroweak symmetry breaking is triggered by a spontaneously broken, approximately conformal sector. Taking into account the possibility of shifts in the dilaton Yukawa couplings to muons, we find a rather promising scenario for the conformal model search in the channel, with the possibility for a dilaton discovery at a delivered luminosity of 100 fb-1 at the LHC or, alternatively, for an extension of the exclusion zone in the model parameter space, until now fixed by the Tevatron., Comment: 6 pages, 3 figures