Vector-like top partner plays a central role in many new physics models which attempt to address the hierarchy problem. The top partner is conventionally assumed to decay to a quark and a SM boson. However, it is also possible that the top partner decays to a non-SM scalar and a top quark. Such an exotic decay channel can be the main decay channel of top partner, and thus provides new windows to search for top partner at the LHC. In this paper, with classical machine learning method Boosted Decision Tree (BDT), we perform a model independent study of the discovery potential of this new signature at the LHC. In order to suppress the main QCD background, we consider subdominant but clean decay channel $a\to γγ$. For completeness, the single production process and pair production process of top partner are all taken into account. We find that, for both single and pair production, the future High-Luminosity LHC can exclude the top partner mass up to TeV scale through channel $T\to t a$ ($a\to γγ$), even if $BR(a\to γγ)$ is as small as $\mathcal{O}$(0.1\%). Besides, our result shows that single production can overmatch pair production at 14 TeV LHC, provided that top partner is heavier than $800\sim 900$ GeV.
We study the Littlest Higgs model with T-parity at the LHC through pair productions of the T-odd top quark partner (T_-) which decays into the top quark and the lightest T-odd particle. We identify the region of parameters favored by the electroweak and cosmological considerations. The signal and background events are simulated with fast detector simulation to study the discovery potential at the LHC. We find that the hemisphere analysis recently proposed by the CMS collaboration is very useful to separate the signal from the t\bar{t} background. We discuss the observability of the top tagged …
This article is a pedagogical review to searches for long-lived particles at the LHC, primarily aimed at experimentalists and theorists seeking to initiate and/or deepen their research in this field. We cover general theory priors and example models, the main experimental techniques for long-lived particles and some of the subtleties involved with both estimating signal efficiencies and background rates.
The discovery of a charged strange hidden-charm state $Z_{cs}$(3985) implies another higher $Z^*_{cs}$ state coupling to $\bar{D}_s^{*-}D^{*0} + c.c$ under the heavy quark spin symmetry. In this paper we discuss a possible hunt for it with data taken at existing facilities. We point out a hint for $Z^*_{cs}$ in the data of $\bar{B}_s^0 \to J/ψK^- K^+$ at LHCb, though weak, in line with the production mechanism of pentaquark $P_c$. We also study the triangular singularity which would possibly enhance the production of $Z^*_{cs}$ in electron-positron collision. Surprisingly, the production rate …
The assumption that strongly interacting sparticles will decay directly to the LSP plus jets breaks down in situations where those decays are Yukawa suppressed. That occurs when producing the first two generations of squarks and when, at the same time, there are several electroweakinos lighter than those squarks. In this paper we analyze the signal of pair production of squarks that subsequently decay to an intermediate neutralino ($\tildeχ_3^0$) plus jets. The neutralino will then decay to the LSP (mainly higgsino) and a Higgs. We have simulated the events and designed a discovery strategy ba…
We show the reinterpretation of existing searches for exotic decays of the Standard Model (SM)-like Higgs, $H \to aa (hh)$, in various final states, in the framework of the 2-Higgs Doublet Model (2HDM) Type-I. We then explore a new search for such light Higgses, $a$ and $h$, at the Large Hadron Collider (LHC) Run 3 for an integrated luminosity of 300 $\text{fb}^{-1}$. After performing a scan over the model parameters, we found that the inverted scenario of Type-I offers a new promising signal in the form of the following cascade decays: $H \to Z^{*}a \to Z^{*}Z^{*}h \to b\overline{b} μ^- μ^+ j…
New physics close to the electroweak scale is well motivated by a number of theoretical arguments. However, colliders, most notably the Large Hadron Collider (LHC), have failed to deliver evidence for physics beyond the Standard Model. One possibility for how new electroweak-scale particles could have evaded detection so far is if they carry only electroweak charge, i.e. are color neutral. Future $e^+e^-$ colliders are prime tools to study such new physics. Here, we investigate the sensitivity of $e^+e^-$ colliders to scalar partners of the charged leptons, known as sleptons in supersymmetric …
Partial wave analysis is performed, with effective potentials as dynamical inputs, to scrutinize the recent LHCb data on the di-$J/ψ$ invariant mass spectrum. Coupled-channel effects are incorporated in the production amplitude via final state interactions. The LHCb data can be well described. A dynamical generated pole structure, which can be identified as the $X(6900)$ state, is found. Our analysis also provides hints for the existence of three other possible states: a bound state $X(6200)$, a broad resonant state $X(6680)$ and a narrow resonant state $X(7200)$. The $J^{PC}$ quantum numbers …
We discuss whether the behaviour of some hadronic quantities, such as the total cross-section, the ratio of the elastic to the total cross-section, are presently exhibiting the asymptotic behaviour expected at very large energies. We find phenomenological evidence that at LHC7 there is still space for further evolution.
The neutrinophilic two-Higgs-doublet model ($ν$2HDM) provides a natural way to generate tiny neutrino mass from interactions with the new doublet scalar $Φ_ν$ ($H^\pm,~H,~A$) and singlet neutrinos $N_R$ of TeV scale. In this paper, we perform detailed simulations for the lepton number violating (LNV) signatures at LHC arising from cascade decays of the new scalars and neutrinos with the mass order $m_{N_R}<m_{Φ_ν}$. Under constraints from lepton flavor violating processes and direct collider searches, their decay properties are explored and lead to three types of LNV signatures: $2\ell^\pm 4j+…
We introduce a simplified low-energy effective Lagrangian description of the phenomenology of heavy vector resonances in the minimal composite Higgs model, based on the coset SO(5)/SO(4), analysing in detail their interaction with lighter top partners. Our construction is based on robust assumptions on the symmetry structure of the theory and on plausible natural assumptions on its dynamics. We apply our simplified approach to triplets in the representations (3, 1) and (1, 3) and to singlets in the representation (1, 1) of SO(4). Our model captures the basic features of their phenomenology in …
By making use of the hybrid collinear and high-energy factorization, where the BFKL resummation of leading and next-to-leading energy logarithms is combined with the standard description in terms of collinear parton densities, we compare predictions for Mueller-Navelet jet rapidity and angular differential rates with data collected by CMS at $\sqrt{s} = 7$ TeV. We provide an evidence that the study of azimuthal distributions, calculated as a Fourier sum of correlation moments and embodying the high-energy signal coming from all conformal-spin modes, permits us to overcome the well-known issues…
We study the central diffractive production of the (three neutral) Higgs bosons, with a rapidity gap on either side, in an MSSM scenario with CP-violation. We consider the bb-bar and tautau-bar decay for the light H_1 boson and the four b-jet final state for the heavy H_2 and H_3 bosons, and discuss the corresponding backgrounds. A direct indication of the existence of CP-violation can come from the observation of either an azimuthal asymmetry in the angular distribution of the tagged forward protons (for the exclusive pp -> p+H+p process) or of a sin(2phi) contribution in the azimuthal correl…
We investigate the search for heavy Majorana neutrinos stemming from a composite model scenario at the upcoming LHC Run II at a center of mass energy of 13 TeV. While previous studies of the composite Majorana neutrino were focussed on gauge interactions via magnetic type transition coupling between ordinary and heavy fermions (with mass $m^*$) here we complement the composite model with contact interactions at the energy scale $Λ$ and we find that the production cross sections are dominated by such contact interactions by roughly two/three orders of magnitude. This mechanism provides therefor…
We perform a comprehensive global analysis in the Minimal Supersymmetric Standard Model (MSSM) as well as in the 2-Higgs Doublet Model (2HDM) of the production and decay mechanisms of charged Higgs bosons $(H^\pm)$ at the Large Hadron Collider (LHC). Starting from the most recent experimental results (SM-like Higgs boson signal strengths and search limits for new Higgs boson states obtained at Run-1 and -2 of the LHC and previous colliders), from (both direct and indirect) searches for Supersymmetric particles as well as from flavor observables (from both $e^+e^-$ factories and hadron collider…
The MoEDAL experiment at the LHC is optimised to detect highly-ionising particles such as magnetic monopoles, dyons and (multiply) electrically-charged stable massive particles predicted in a number of theoretical scenarios. MoEDAL, deployed in the LHCb cavern, combines passive nuclear track detectors with magnetic monopole trapping volumes, while backgrounds are being monitored with an array of MediPix detectors. The detector concept and its physics reach is presented with emphasis given to recent results on monopoles.
Searches at the Large Hadron Collider (LHC) for neutral, long-lived particles have historically relied on the detection of displaced particles produced by their decay $\textit{within}$ the detector volume. In this paper we study the potential of the complementary signature comprising of the missing transverse energy ($E_T^{miss}$) signal, traditionally used to look for dark matter, e.g., the lightest supersymmetric particle (LSP), to extend the LHC coverage to models with long-lived (LL) particles when they decay $\textit{outside}$ the detector. Using CMS and ATLAS analyses at the 8 TeV LHC, w…
We demonstrate that a purposefully normalised NNLO top pair invariant mass differential spectrum can have very small theoretical uncertainty and, in particular, a small sensitivity to the top quark mass. Such observable can thus be a very effective bump-hunting tool for resonances decaying to top pair events during LHC Run II and beyond. To illustrate how the approach works, we concentrate on one specific example of current interest, namely, the possible 750 GeV di-gamma excess resonance Phi. Considering only theoretical uncertainties, we demonstrate that it is possible to distinguish pp -> Ph…
Composite Higgs models with a fermionic UV completion can contain additional colored states beside the usual top-partners. We focus here on a model which contains in addition SU(3) color octet top partners as well as color singlet ones. The latter can in principle serve as a dark matter candidate. We consider a particular composite Higgs model which contains SU(3) color octet top partners besides the usually considered triplet representations. Moreover, color singlet top partners are present as well which can in principle serve as dark matter candidates. We investigate the LHC phenomenology of…
The single vector-like top partner hadroproduction in association with top quark in the five and the six-flavour schemes at the LHC is investigated. The inclusive cross section and the differential distributions are evaluated for many benchmark scenarios at leading and next-to-leading orders, both for fixed-order and fixed-order matched to parton shower. The associated Higgs production with a top quark pair, where the final state arises from the decay of the vector-like top partner into a Higgs boson and a top quark, is examined.
We explore a possibility that an inflaton, which drives the cosmological inflation in the early Universe, can be detected by the recently approved FASER at the High-Luminosity LHC (HL-LHC). We consider nonminimal quartic inflation scenario in the minimal U(1)$_X$ extension of the Standard Model (SM) with the classical conformal invariance, where the inflaton is identified with the U(1)$_X$ Higgs field ($ϕ$). By virtue of the classical conformal invariance and the radiative U(1)$_X$ symmetry breaking via the Coleman-Weinberg mechanism, the inflationary predictions (in particular, the tensor-to-…
Many scenarios of physics beyond the Standard Model that address the hierarchy problem also predict the existence of vector-like top quark partners, which are generally expected around the TeV scale. In this paper, we propose to search for a vector-like top quark partner with charge $2/3$ in a simplified model including only two free parameters, the coupling constant $g^{\ast}$ and top quark partner mass $m_T$. We investigate the observability of the top quark partner through the process $pp \to T(\to th)j\to t(\to b W^+\to b \ell^{+} ν_{\ell})h( \to WW^{\ast}\to \ell^{+}ν\ell^{-}\barν) j$, wh…
Studying semi-hard processes in the large center-of-mass energy limit gives us an opportunity to further test perturbative QCD in an unexplored kinematical configuration, contributing to a better understanding of the dynamics of strong interactions. For semi-hard reactions in kinematics at large center-of-mass energy $\sqrt{s}$, the BFKL resummation of energy logarithms comes into play, since large energy logarithms compensate the smallness of QCD coupling $α_s$ and must therefore be accounted for to all perturbative orders. Tracing the path toward performing precision calculations via BFKL re…
In the Littlest Higgs model with T-parity (LHT), top-partners (T_-) are produced in pairs at the Large Hadron Collider (LHC). Each top-partner decays into a top quark (t) and the lightest T-odd gauge partner A_H. We demonstrate reconstruction of the ttbar system decaying hadronically, and measurement of the top-partner mass from the m_{T2} distribution. A top quark from a T_{-} decay is polarized, and we discuss the effect of this polarization on the decay distributions. Because the events consist of highly collinear jets which occasionally overlap each other, we compare distributions using di…
New vectorlike quarks are predicted in many new physics scenarios beyond the Standard Model~(SM) and could potentially be discovered at the LHC. Based on a simplified model including a singlet vectorlike top partner with charge $2/3$, we investigate the process $pp \to TT$ via a $t$-channel induced by the couplings between the top partner with the first-generation SM quarks. We calculate the production cross section and further study the observability of the heavy top partner in the channel $T\to Wq$ at the high-luminosity LHC (HL-LHC) using final states with same-sign dileptons (electrons or …
Some new physics models, such as "beautiful mirrors" scenario, predict the existence of the bottom partner $B'$. Considering the constraints from the data for the $Z\rightarrow b\bar{b}$ branching ratio $R_{b}$ and the $FB$ asymmetry $A_{FB}^{b}$ on the relevant free parameters, we calculate the contributions of $B'$ to the cross section $σ(Zb)$ and the $Z$ polarization asymmetry $A_{Z}$ for $Zb$ production at the $LHC$. We find that the bottom partner $B'$ can generate significant corrections to $σ(Zb)$ and $A_{Z}$, which might be detected in near future.
LHC searches for fermionic top partners $T$ focus on three decay topologies: $T\to bW$, $T\to tZ$, and $T\to th$. However, top partners may carry new conserved quantum numbers that forbid these decays. The simplest possibility is a conserved parity, under which the top partner is odd and all SM states are even. In this case, decays of top partners may involve new particle-odd scalars, leading to signal topologies more commonly associated with supersymmetry, either with or without R-parity conservation. We study a simplified model in which this possibility is realized, and estimate the bounds o…
We extend the coverage of resonant di-Higgs searches in the $b \bar{b} b \bar{b}$ final state to the process $p p \to H_1 \to H_2 H_2 \to b \bar{b} b \bar{b}$, where both $H_{1,2}$ are spin-$0$ states beyond the Standard Model. Such a process constitutes a joint discovery mode for the new states $H_1$ and $H_2$. We present the first sensitivity study of this channel, using public LHC data to validate our analysis. We also provide a first estimate of the sensitivity of the search for the HL-LHC and future facilities like the HE-LHC and FCC-hh. We analyze the discovery potential of this search f…
The Standard Model is a successful theory but lack of a mechanism for neutrino mass generation as well as a solution to the naturalness problem. In the models that are proposed to simultaneously solve the two problems, heavy Majorana neutrinos and top partners are usually predicted that can lead to a new decay mode of the top partner mediated by the heavy Majorana neutrinos: $T\to b\,W^{+}\to b\,\ell^{+}\ell^{+}q\bar{q'}$. In this paper, we will study the observability of such a new signature via the pair production process of top partner $pp \to T\bar{T} \to 2b+ \ell^\pm \ell^\pm+4j$ in a mod…
Most searches for top partners, $T$, are concerned with top partner pair production. However, as these bounds become increasingly stringent, the LHC energy will saturate and single top partner production will become more important. In this paper we study the novel signature of the top partner produced in association with the SM top, $pp\rightarrow T\overline{t}+t\overline{T}$, in a model where the Standard Model (SM) is extended by a vector-like $SU(2)_L$ singlet fermion top partner and a real, SM gauge singlet scalar, $S$. In this model, $pp\rightarrow T\overline{t}+t\overline{T}$ production …
In scenarios that stabilize the electroweak scale, the top quark is typically accompanied by partner particles. In this work, we demonstrate how extended stabilizing symmetries can yield scalar or fermionic top partners that transform as ordinary color triplets but carry exotic electric charges. We refer to these scenarios as "hypertwisted" since they involve modifications to hypercharge in the top sector. As proofs of principle, we construct two hypertwisted scenarios: a supersymmetric construction with spin-0 top partners, and a composite Higgs construction with spin-1/2 top partners. In bot…
The coannihilation mechanism is a well-motivated alternative to the simple thermal freeze-out mechanism, where the dark matter relic density can be obtained through the coannihilation with a partner particle of similar mass with dark matter. When the partner particle is neutral, the inelastic nature of dark matter can help it to escape the direct detection limits. In this work, we focus on the coannihilation scenario in which the annihilation cross section is dominated by the partner-partner pair annihilation. We pay special interest on the parameter space where the coannihilation partner is l…
Heavy partners of the top quark are a common prediction of many models in which a new strongly-coupled sector is responsible for the breaking of the EW symmetry. In this paper we investigate their experimental signature at the LHC, focusing on the particularly clean channel of same-sign dileptons. We show that, thank to a strong interaction with the top quark which allows them to be singly produced at a sizable rate, the top partners will be discovered at the LHC if their mass is below 1.5 TeV, higher masses being possible in particularly favorable (but plausible) situations. Being the partner…
Colored dark sectors where the dark matter particle is accompanied by colored partners have recently attracted theoretical and phenomenological interest. We explore the possibility that the dark sector consists of the dark matter particle and a color-octet partner, where the interaction with the Standard Model is governed by an effective operator involving gluons. The resulting interactions resemble the color analogues of electric and magnetic dipole moments. Although many phenomenological features of this kind of model only depend on the group representation of the partner under SU(3)$_c$, we…
Non-Standard-Model parity violation may be occurring in LHC collisions. Any such violation would go unseen, however, as searches are for it are not currently performed. One barrier to searches for parity violation is the lack of model-independent methods sensitive to all of its forms. We remove this barrier by demonstrating an effective and model-independent way to search for parity-violating physics at the LHC. The method is data-driven and makes no reference to any particular parity-violating model. Instead, it inspects data to construct sensitive parity-odd event variables (using machine le…
Naturalness demands that the quadratic divergence of the one-loop top contribution to the Higgs mass be cancelled at a scale below 1 TeV. This can be achieved by introducing a fermionic (spin-1/2) top partner, as in, for example, Little Higgs models. In this paper, we study the phenomenology of a simple model realizing this mechanism. We present the current bounds on the model from precision electroweak fits, flavor physics, and direct searches at the LHC. The lower bound on the top partner mass from precision electroweak data is approximately 500 GeV, while the LHC bound with 5/fb of data at …
In the littlest Higgs Model with T-parity, we discuss the pair production of the T-odd top partner ($T_{-}$) which decays almost 100\% into the top quark and the lightest T-odd particle ($A_{H}$). Considering the current constraints, we investigate the observability of the T-odd top partner pair production through the process $pp\rightarrow T_{-}\bar{T}_{-}\rightarrow t\bar{t}A_{H}A_{H}$ in final states with two leptons at 14 TeV LHC. We analyze the signal significance and find that the lower limit on the T-odd top partner mass are about 1.04 TeV, 1.14 TeV, 1.23 TeV at $2σ$ confidence level at…
Simplified models of the dark matter (co)annihilation mechanism predict striking new collider signatures untested by current searches. These models, which were codified in the coannihilation codex, provide the basis for a dark matter (DM) discovery program at the Large Hadron Collider (LHC) driven by the measured DM relic density. In this work, we study an exemplary model featuring $s$-channel DM coannihilation through a scalar diquark mediator as a representative case study of scenarios with strongly interacting coannihilation partners. We discuss the full phenomenology of the model, ranging …
We investigate the sensitivity of the 14 TeV LHC to pair-produced top partners ($T$) decaying into the Standard Model top quark ($t$) plus either a gluon ($g$) or a photon ($γ$). The decays $T\rightarrow tg$ and $T\rightarrow tγ$ can be dominant when the mixing between the top partner and top quark are negligible. In this case, the conventional decays $T\rightarrow bW$, $T\rightarrow tZ$, and $T\rightarrow th$ are highly suppressed and can be neglected. We take a model-independent approach using effective operators for the $T$-$t$-$g$ and $T$-$t$-$γ$ interactions, considering both spin-$\frac{…
We outline a strategy of how to search for QCD instantons of invariant mass 20 -- 60 GeV in diffractive events in low luminosity runs at the LHC. We show that by imposing appropriate selection criteria on the final states, one can select the kinematic regime where the instanton signal exceeds the background by a factor of at least 8. In spite of the relatively strong cuts that we impose on the total transverse energy and the number of charged tracks, $\sum_i E_{T,i}>15$ GeV, $N_{\rm ch}>20$ measured within the $0<η<2$ interval and excluding events with high $p_{T}$ particles, the expected cros…
The new heavy vector-like top partner~($T$) is one of typical features of many new physics models beyond the standard model. In this paper we study the discovery potential of the LHC for the vector-like $T$-quark both in the leptonic $T\to bW$ and $T\to t_{\rm lep}Z_{\rm lep}$ (trilepton) channels at $\sqrt{s}= 14$ TeV in the single production mode. Our analysis is based on a simplified model including a $SU(2)_L$ singlet with charge $2/3$ with only two free parameters, namely the $TWb$ coupling parameter $g^{\ast}$ and the top partner mass $m_T$. The $2σ$ exclusion limits, $3σ$ evidence and t…
We first build a minimal model of vector-like quarks where the dominant Higgs boson production process at LHC -- the gluon fusion -- can be significantly suppressed, being motivated by the recent stringent constraints from the search for direct Higgs production over a wide Higgs mass range. Within this model, compatible with the present experimental constraints on direct Higgs searches, we demonstrate that the Higgs ($h$) production via a heavy vector-like top-partner ($t_2$) decay, $pp \to t_2 \bar t_2$, $t_2\to t h$, allows to discover a Higgs boson at the LHC and measure its mass, through t…
Single production of vector-like top partners is becoming a major focus of new searches, as the increasing mass limits on vector-like quarks obtained by the ATLAS and CMS collaborations are such that single production is becoming competitive with respect to pair production. Typically searches focus on decays containing leptons in the final state in order to have less background from the Standard Model processes. However the current centre of mass energies available in the latest LHC runs limit the searches to low masses. Fully hadronic final states may be an alternative option for discovery, a…
We consider the phenomenology at the Large Hadron Collider of new heavy vector-like quarks which couple mainly to the third generation quarks via Yukawa interactions, with special emphasis on non-standard doublet representations which are less constrained from present data. We also discuss in detail the flavour limits at tree level and loop level and implications of a generalised CKM mixing matrix to these cases.
Extensions of the Standard Model which address the hierarchy problem and dark matter (DM) often contain top partners and additional resonances at the TeV scale. We explore the phenomenology of a simplified effective model with a vector resonance $Z'$, a fermionic vector-like coloured partner of the top quark $T'$ as well as a scalar DM candidate $ϕ$ and provide publicly available implementations in CalcHEP and MadGraph. We study the $pp \to Z' \to T'\overline{T'} \to t\bar{t}\,ϕϕ$ process at the LHC and find that it plays an important role in addition to the $T'\overline{T'}$ production via st…
In the present work, we investigate the productions of the molecular states composed of $D^{(*)}_s \bar{D}^{(*)}$ and $D^{(*)}_s \bar{D}^{(*)}_s$ in the $B$ and $B_s$ decays by using an effective Lagrangian approach. The branching ratios in terms of the model parameter $α$ and the binding energy $ΔE$ are estimated. Our estimations indicate that the branching fractions are of the order of $10^{-4}$ and the relative ratios are very weakly dependent on the model parameter $α$ and the binding energy $ΔE$. The predicted ratios are helpful for searching the hidden-charm molecular states with strange…
Jožef Stefan Institute（约瑟夫·斯特凡研究所）；Universität Heidelberg（海德堡大学）；University of Ljubljana（卢布尔雅那大学）
Unsupervised anomaly detection could be crucial in future analyses searching for rare phenomena in large datasets, as for example collected at the LHC. To this end, we introduce a physics inspired variational autoencoder (VAE) architecture which performs competitively and robustly on the LHC Olympics Machine Learning Challenge datasets. We demonstrate how embedding some physical observables directly into the VAE latent space, while at the same time keeping the classifier manifestly agnostic to them, can help to identify and characterise features in measured spectra as caused by the presence of…
Composite Higgs models provide a natural, non-supersymmetric solution to the hierarchy problem. In these models, one or more sets of heavy top-partners are typically introduced. Some of these new quarks can be relatively light, with a mass of a few hundred GeV, and could be observed with the early LHC collision data expected to be collected during 2010. We analyse in detail the collider signatures that these new quarks can produce. We show that final states with two (same-sign) or three leptons are the most promising discovery channels. They can yield a 5 sigma excess over the Standard Model e…
We study single production and detection at the LHC run II of exotic partners of the bottom quark. For masses larger than 1 TeV single production can dominate over pair production that is suppressed due to phase space. The presence of exotic partners of the bottom is motivated in models aiming to solve the $A_{FB}^b$ anomaly measured at LEP and SLC. Minimal models of this type with partial compositeness predict, as the lightest bottom partner, a new fermion V of electric charge -4/3, also called mirror. The relevant coupling for our study is a WVb vertex, which yields a signal that corresponds…
The agreement between calculations inspired by the resummation of energy logarithms, known as BFKL approach, and experimental data in the semi-hard sector of QCD has become manifest after a wealthy series of phenomenological analyses. However, the contingency that the same data could be concurrently portrayed at the hand of fixed-order, DGLAP-based calculations, has been pointed out recently, but not yet punctually addressed. Taking advantage of the richness of configurations gained by combining the acceptances of CMS and CASTOR detectors, we give results in the full next-to-leading logarithmi…
Vector-like quarks (VLQs) that are partners of the heavy top and bottom quarks are predicted in many extensions of the Standard Model (SM). We explore the possibility that these states could explain not only the longstanding anomaly in the forward-backward asymmetry in $b$-quark production at LEP, $A_{\rm FB}^b $, but also the more recent $\sim 2σ$ deviation of the cross section for the associated Higgs production with top quark pairs at the LHC, $σ(pp\to t\bar t H)$. Introducing three illustrative models for VLQs with different representations under the SM gauge group, we show that the two an…
We study the implications of a large degree of compositeness for the light generation quarks in composite pseudo-Nambu-Goldstone-boson Higgs models. We focus in particular on viable scenarios where the right-handed up-type quarks have a sizable mixing with the strong dynamics. For concreteness we assume the latter to be characterized by an SO(5)/SO(4) symmetry with fermionic resonances in the SO(4) singlet and fourplet representations. Singlet partners dominantly decay to a Higgs boson and jets. As no dedicated searches are currently looking for these final states, singlet partners can still b…
In this work, we use the results from Higgs searches in the $γγ$ and $ττ$ decay channels at LHC and indirect bounds as BR$(B \to X_s γ)$ to constrain the parameter space of a generic MSSM Higgs sector. In particular, we include the latest CMS results that look for additional Higgs states with masses up to 1 TeV. We show that the $ττ$ channel is the best and most accurate weapon in the hunt for new Higgs states beyond the Standard Model. We obtain that present experimental results rule out additional neutral Higgs bosons in a generic MSSM below 300 GeV for any value of $\tan β$ and, for instanc…
In perturbative QCD approach, based on the first order of isospin symmetry breaking, we study the direct $CP$ violation in the decay of $\bar{B}_s^0\toρ(ω)K^{*0}\to {π^+}{π^-}K^{*0}$. An interesting mechanism is applied to enlarge the $CP$ violating asymmetry involving the charge symmetry breaking between $ρ$ and $ω$. We find that the $CP$ violation is large by the $ρ-ω$ mixing mechanism when the invariant masses of the $π^+π^-$ pairs is in the vicinity of the $ω$ resonance. For the decay process of $\bar{B}^0_{s}\toρ(ω)K^{*0}\to{π^+}{π^-}K^{*0}$, the maximum $CP$ violation can reach $-59.12\%…
