Paul H. Frampton
We discuss a minimal and simple extension of the standard electroweak model and discuss its uniqueness properties. Its most readily testable prediction is the existence of $|Q|= |L|= 2$ gauge bosons, bileptons, which decay into like-sign lepton pairs. We discuss how a discovery could be made at the LHC.
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Upper limits on doubly charged bilepton couplings and masses are extracted from LEP data for Bhabha scattering at energy range $\sqrt{s}=183-202$ GeV using standard model program ZFITTER which calculates radiative corrections. We find that $g_{L}^{2}/M_{L}^{2}<O(10^{-5})GeV^{-2}$ at 95% C.L. for scalar and vector bileptons.
We search for lepton flavour violating couplings via doubly charged bilepton (or doubly charged Higgs) exchange in electron-positron annihilation process $ \text{e}^{+}\text{e}^{-}\to μ^{+}μ^{-}, τ^{+}τ^{-}$ using CERN LEP data at the center of mass energies between 189-207 GeV. Standard model program ZFITTER has been used to calculate radiative corrections. We find that $g_{L}^{2}/M_{L}^{2}<O(10^{-6})GeV^{-2}$ at 95% C.L. for flavour violating scalar and vector bilepton couplings.
In this paper we investigate the LHC potential for discovering doubly-charged vector bileptons considering the measurable process $p,p$ $\rightarrow$ $e^{\mp}e^{\mp}μ^{\pm}μ^{\pm} X$. We perform the study using four different bilepton masses and three different exotics quark masses. Minimal LHC integrated luminosities needed for discovering and for setting limits on bilepton masses are obtained for both 7 TeV and 14 TeV center-of-mass energies. We find that these spectacular signatures can be observed at the LHC in the next years up to a bilepton mass of order of 1 TeV.
We search for doubly charged scalar bileptons via $ \text{e}^{-}\text{e}^{-}\to μ^{-}μ^{-}$ and $ \text{e}^{-}\text{e}^{-}\to \text{e}^{-}\text{e}^{-}$ processes at linear collider energies by considering initial and final state electromagnetic radiative corrections (ISR, FSR). Moreover, smeared cross section is used for finite energy resolution. We show that ISR+FSR and smearing reduce cross sections remarkably depending on the smearing parameter due to narrow decay width of bileptons. We obtain realistic discovery contours of couplings and masses for the lepton flavour conserving and violati…
We show that the accumulated LEP-II data taken at $\sqrt{s} =$ 130 to 206 GeV can establish more restrictive bounds on doubly charged bileptons couplings and masses than any other experiment so far. We also analyze the discovery potential of a prospective linear collider operating in both $e^+ e^-$ and $e γ$ modes.
Mass bounds for doubly-charged bilepton gauge bosons are derived from constraints on fermion pair production at LEP and lepton-flavour violating charged lepton decays. The limit obtained of 700 GeV for the doubly-charged bilepton does not depend on the bilepton coupling being flavour-diagonal, unlike other bounds which have been given in the literature.
The production of pairs of doubly charged vector bileptons is studied at future $γγ$ colliders. The unpolarized cross--section for the $γγ\to Y^{--}Y^{++}$ subprocess is analytically calculated and convoluted to predict the number of events in the complete $e^+e^-\to γγ\to Y^{--}Y^{++}$ process. The gauge or non--gauge character of the vector bilepton $Y^{\pm \pm}$ is discussed. It is found that as a consequence of its spectacular signature, as it decays dominantly into two identical charged leptons, and also due to its charge contents, which significantly enhance the cross--section, the detec…
The LHC potential for discovering doubly-charged vector bileptons is investigated considering the measurable process $p p$ $\rightarrow$ $μ^{\mp}μ^{\mp}μ^{\pm}μ^{\pm} X$. The study is performed assuming different bilepton and leptoquark masses. The process cross-section is calculated at leading-order using the \textsc{Calchep} package. Combining the calculation with the latest ATLAS experiment results at a center-of-mass energy of 7 TeV, bounds on bilepton masses based on LHC data are derived for the first time. The results exclude bileptons masses in the range of 200 GeV to 500 GeV at 95\% C.…
Some extensions of the standard model predict the existence of particles having two units of leptonic charge, known as bileptons. One of such models is based on the $SU(3)_c\times SU(3)_L\times U(1)_X$ symmetry group (3-3-1 model, for short). Our search uses the minimal version of the 3-3-1 model, having exotic charges for the quarks and new gauge bosons. This model predicts the existence of bileptons as vector particles having one ($V^{\pm}$) and two ($Y^{\pm\pm}$) units of electric charge. We study the signatures for the production of four leptons by considering the contribution of a pair of…
We analyze the prospects for discovering and unraveling the nature of doubly-charged bileptons at a linear collider of the next generation running in its electron-electron colliding mode. We stress the importance of initial state radiation, beam spread and polarization, and compute the discovery bounds. The gauge nature of vector bileptons can be determined by studying hard photon emission.
We discuss the main signatures of the Bilepton Model at the Large Hadron Collider, focusing on its gauge boson sector. The model is characterised by five additional gauge bosons, four charged and one neutral, beyond those of the Standard Model, plus three exotic quarks. The latter turn into ordinary quarks with the emission of bilepton doublets $(Y^{++},Y^{+})$ and $(Y^{--},Y^{-})$ of lepton number $L=-2$ and $L=+2$ respectively, with the doubly-charged bileptons decaying into same-sign lepton pairs. We perform a phenomenological analysis investigating processes with two doubly-charged bilepto…
We present an analysis on the production of two same-sign lepton pairs at the LHC, mediated by bileptons in the $SU(3)_c\times SU(3)_L\times U(1)_X$ theory, the so-called 331 model. Compared to other 331 scenarios, in this model the embedding of the hypercharge is obtained with the addition of 3 exotic quarks and doubly-charged vector gauge bosons with lepton numbers $\pm 2$ in the spectrum ($Y^{\pm\pm}$), which can mediate the production of four-lepton final states. Furthermore, a complete description of the model requires the introduction of a Higgs scalar sector, which is a sextet of $SU(3)…
In this paper, limits are set on bileptons masses and couplings in the context of the the 331 Model, as well as generic, non-331 Models predicting bileptons. The following measurable processes are studied: $pp \rightarrow \ell^{+}\ell^{+}\ell^{-}\ell^{-}X$, $pp \rightarrow \ell^{+}\ell^{-} ννX$ and $pp \rightarrow \ell^{+}\ell^{-} X$. Experimental limits on singly-charged bileptons masses and couplings within 331 Models are also obtained for the first time. With the results, an over 20 year-old experimental limit on vector bileptons is increased by 60\%. The computed limits are now the most st…
Using the most recent experimental data on parameters of the standard electroweak theory, as well as renormalisation group equations with a boundary matching condition, we derive a refined and more accurate value for the mass of the doubly-charged bilepton ($Y^{\pm\pm}$) occurring in the spontaneous breaking of the gauge group $SU(3)_L \times U(1)_X$ to the standard electroweak gauge group $SU(2)_L \times U(1)_Y$. Our result is $M(Y^{\pm\pm}) = (1.29 \pm 0.06)$ TeV.
We study the lepton flavor violating (LFV) decays Z-> l_i l_j (l_{i,j}=e,μ,τ) in the framework of the minimal 331 model. The main contributions arise at the one-loop level via a doubly charged bilepton with general LFV couplings. We obtain an estimate for the corresponding branching ratios by using the bounds on the LFV couplings of the doubly charged bilepton from the current experimental limits on the decays l_i-> l_jγand l_i-> l_j l_k l_k. A bound on the bilepton mass is also obtained through the current limit on the anomalous magnetic moment of the muon. It is found that the bilepton contr…
Hunting for bileptons at hadron colliders
本文回顾了基于331模型预言的双轻子在强子对撞机上的轻子与非轻子衰变信号，并探讨了当前和未来对撞机对这类过程的探测灵敏度。
We consider pair production of bileptons $Y^{++}Y^{--}$ at the LHC for the presently accumulated integrated luminosity of $150/fm$. It is shown that the entire mass range 800 GeV $\leq$ M(Y) $\leq$ 2000 GeV can be successfully searched. A bilepton resonance will have an exceptionally large ratio of signal to background because the standard model prediction is so infinitesimal. A $5σ$ discovery is quite feasible.
We present a complete calculation of the singly and doubly charged gauge bosons (bileptons) contribution to the static properties of the W boson in the framework of the minimal 331 model, which accommodates the bileptons in an SU_L(2) doublet. A nonlinear R_ξgauge is used and a slightly modified version of the Passarino-Veltman reduction scheme is employed as in this case the Gram determinant vanishes. It is found that the bilepton contribution is of the same order of magnitude as those arising from other weakly coupled renormalizable theories, like the two-Higgs doublet model and supersymmetr…
In the upcoming LHC Run 2, at $\sqrt{s} \sim13$ TeV, it is suggested to seek unusually charged ($Q= -4/3$ and $+5/3$) quarks with mass $M_Q \sim 3$ TeV which carry lepton number ($L = +2$ and $-2$ respectively) and decay superweakly to a bilepton $Y$ with mass $M_Y\sim2.5$ TeV and a usual quark. These long-lived decays will have displaced decay vertices and produce a striking final state in $pp$ which contains two separated jets together with two pairs of correlated like-sign charged leptons. Such a process was inaccessible energetically in LHC Run 1 with $\sqrt{s} \sim8$ TeV. The simplest the…
331 Models and Bilepton Searches at LHC
本研究针对标准模型的遗留问题，聚焦含类矢量夸克与新规范玻色子的331最小扩展模型，首次纳入所有类矢量夸克相关过程分析LHC上双荷双轻子对的产生，并借助ATLAS实验结果得出双轻子质量大于1300 GeV的约束。
Heavy Quark Decays in the Bilepton Model
重子模型中研究重夸克衰变，通过双lepton衰变机制在高能对撞机中可能被观测到
The production of $W^+ W^-$ pair in hadron colliders was calculated up to loop corrections by some authors in the Electroweak standard model (SM) framework. This production was also calculated, at the tree level, in some extensions of the SM such as the vector singlet, the fermion mirror fermion and the vector doublet models by considering the contributions of new neutral gauge bosons and exotic fermions. The obtained results for $e^+ e^-$ and $pp$ collisions pointed out that the new physics contributions are quite important. This motivates us to calculate the production of a more massive char…
The 3-3-1 electroweak model is the simplest chiral extension of the standard model which predicts single and double charged bileptons and exotic quarks carrying -4/3 and 5/3 units of the positron charge. In this paper we study the possibilities of the production and decay of one of these exotic quarks at CERN LEPII-LHC collider. For typical vector bilepton, exotic quark masses and mixing angles we obtained between 20 and 750 events per year. Angular distributions are also presented.
Phenomenology of the doubly-charged vector bilepton
本文研究双电荷矢量双轻子 U^{±±} 的现象学，通过LHC三μ子过程与七个三体轻子衰变约束其参数，并分析最小3-3-1模型的耦合跑动，发现其微扰区大于传统预期。
Rescuing 331 bileptons from the Landau pole
针对带β=√3的最简331模型中低能朗道极点会破坏TeV能标双轻子预言的问题，研究人员分析该问题并探索通过扩展最简331模型将朗道极点移至更高能标的可行性。
We analyze the effects of a doubly charged vector bilepton as well as exotic quarks with charge 5/3 e and -4/3 e on light by light scattering. We consider mass values in the range 0.3--1 TeV, which would be reached at the planned future linear colliders. It is found that such exotic particles, especially the doubly charged vector bilepton, give raise to remarkable deviations from the standard model cross section. The virtual effects arising from these particles would provide an indirect test to a particular model which is based on the SU_c(3) X SU_L(3) X U_x(1) gauge symmetry, known as the 331…
Predicting Three Generations of Fermions: Discovery Prospects of the Bilepton Model
研究双电荷双 lepton 对的产生及在高亮度 LHC 上的发现潜力，分析其与重夸克质量的关系，探讨两种不同产生机制对参数空间的互补探测。
We point out that when doubly-charged bileptons are pair produced at the LHC, kinematics dictate that they are both almost at rest in the lab frame and therefore their decays lead to final state muons in a characteristic X-shape with only very tiny track curvature because of the high muon energies. Such X-events have essentially no standard model background and provide a smoking gun for the 331 model.
Heavy vector-boson hunting is one of the major analyses undertaken by the experiments carried out at the LHC. I will explore two scenarios which have not been investigated yet by the experimental collaborations. The first scenario consists in searching for Z' bosons, predicted by U(1)' GUT-inspired models, by studying its supersymmetric decays, leading to resonant final states with charged leptons and missing energy. Afterwards, I shall discuss the 331 model and the production of doubly-charged vector bileptons, yielding events with two same-sign lepton pairs at the LHC.
The theoretical analysis of production, lifetime, and decays of doubly heavy baryons is presented. The lifetime of $Ξ_{cc}^{++}$ baryon recently measured by the LHCb Collaboration is used to estimate the lifetimes of other doubly heavy baryons. The production and the possibility of observation of $Ξ_{bc}$ baryon at LHC are discussed.
In the paper we discuss contribution of the doubly intrinsic heavy mechanism into the production of $B_c$ meson, the doubly heavy baryons and the all-charm tetraquark at a future fixed-target experiment at the LHC (AFTER@LHC). The production cross sections and the mean values of Feynman-x for the finale states are presented.
Doubly charged Higgs bosons are very important in particle physics nowadays because they can give mass to neutrinos through seesaw mechanisms. In this work we present the results in the searching for doubly charged Higgs at the CERN LHC for a 3-3-1 model.
Doubly charged scalars are common figures in several beyond the Standard Model studies, especially those related to neutrino masses. In this work, we estimate the High-Luminosity (HL-LHC) and High-Energy LHC (HE-LHC) sensitivity to doubly charged scalars assuming they decay promptly and exclusively into charged leptons. Our study focuses on the fit to the same-sign dilepton mass spectra and it is based on proton-proton collisions at $13$ TeV, $14$ TeV and $27$ TeV with integrated luminosity of $\mathcal{L}=139 fb^{-1}, 3 $ab$^{-1}$ and $15$ab$^{-1}$. We find that HL-LHC may probe doubly charge…
We studied the signatures at the LHC of the electroweak SU(2) lepton doublet which embeds a doubly charged lepton. The doubly charged lepton pair and single production rates, which are different from the triplet case, are studied and all the detectable decay modes are considered. We also applied the same kinematic cuts as in triplet case to reduce the background at LHC and the needed integrated luminosities to find the doubly charged leptons with different masses are analyzed. We also suggested a method to distinguish the exotic lepton doublet and triplet.
In the minimal extension of the standard electroweak theory with ultra massive Majorana neutrinos, the process e- + e- -> mu- + mu- could be observable, in sharp contrast with the reaction e- + e- -> W- + W- which is entirely controlled by neutrinoless double beta decay $ββ_{0 ν}$ data. Our result provides the process background that must be confronted "new physics" models which postulate doubly charged particles, such as the gauge bilepton Y^{-} in the $SU(3)_{\rm c} \times SU(3)_{\rm L} \times U(1)$ model, the left-right $SU(2)_{\rm L} \times SU(2)_{\rm R} \times U(1)_{\rm B-L}$ one, and its…
Using a peculiar version of the SU(3)L x U(1)N electroweak model, we investigate the production of doubly charged Higgs boson at the Large Hadron Collider. Our results include branching ratio calculations for the doubly charged Higgs and for one of the neutral scalar bosons of the model.
We studied the signatures of an electroweak SU(2) lepton triplet which contains a doubly charged heavy lepton. The most interesting and easily detected final states are originating from the doubly charged lepton pair and single production, that we analyzed at a center of mass energy of 14 TeV. We propose useful kinematic cuts to reduce the backgrounds and computed the integrated luminosity needed to discover or exclude the doubly charged leptons for various masses.
We study the production of doubly charged excited leptons at the LHC. These exotic states are predicted in extended weak isospin composite models. A recent analysis of such exotic states was based on a pure gauge model with magnetic type interactions. We include here the mechanism of contact interactions and show that this turns out to dominate the production of the doubly charged leptons. We perform a feasibility analysis of the observation of the tri-lepton signature associated with the production of the exotic doubly charged lepton simulating the response of a generic detector. We give excl…
Interactions among the standard model gauge bosons and scalar fields in the framework of SU(3)_C X SU(3)_L X U(1)_X gauge model with minimal (economical) Higgs content are presented. From these couplings, all scalar fields including the neutral scalar $h$ and the Goldstone bosons can be identified and their couplings with the usual gauge bosons such as the photon, the charged $W^\pm$ and the neutral $Z$, without any additional condition, are recovered. In the effective approximation, full content of scalar sector can be recognized. The CP-odd part of Goldstone associated with the neutral non-H…
We show that the photon-photon fusion process contributes significantly to the pair production of doubly charged Higgs bosons at the LHC at a level comparable to the Drell-Yan production. We reinterpret the ATLAS lower limit of 570 GeV (420 GeV) on the mass of $Δ_{L}^{\pm\pm}$ ($Δ_{R}^{\pm\pm}$) arising from $SU(2)_L$ triplet (singlet) scalar by including the photon initiated process and derive a new lower limit of 748 GeV (570 GeV), assuming that $Δ^{\pm \pm}$ decays into $e^\pm e^\pm$ 100% of the time. We have also shown that the 5$σ$ discovery reach for ${Δ_{L}^{\pm\pm}}$ (${Δ_{R}^{\pm\pm}}…
Since the LHCb collaboration announced the observation of the doubly charmed baryon $Ξ_{cc}^{++}$, a series of studies of doubly heavy baryons have been presented. In this work, I analyse the non-leptonic weak decays of doubly heavy baryons $Ξ_{bc}$ and $Ω_{bc}$ under the flavor $SU(3)$ symmetry. I mainly focus on the $W$-exchange diagrams, which will contribute to the decay channels with final states are light meson and light baryon. These channels would be helpful for searching for $Ξ_{bc}$ and $Ω_{bc}$ at LHC. And these channels and relations of corresponding decay widths could be examined …
We study the pair production of doubly charged Higgs bosons at the Large Hadron Collider (LHC), assuming the doubly charged Higgs to be part of an SU(2)_L triplet which generates Majorana masses for left-handed neutrinos. Such pair-production has the advantage that it is not constrained by the triplet vacuum expectation value, which tends to make the single production rate rather small. We point out that, in addition to the Drell-Yan (DY) production mechanism, two-photon processes also contribute to H++H++ production at a level comparable to the QCD corrections to the DY channel. Decays of the…
We explore a realistic supersymmetric SU(2)_L \times SU(2)_R \times U(1)_B-L model spontaneously broken at around 10^12 GeV. The presence of D and F-flat directions gives rise to TeV mass doubly charged particles which can be found at the LHC. We implement TeV scale leptogenesis and employing both type I and II seesaw, the three light neutrinos are partially degenerate with masses in the 0.02-0.1 eV range. The effective mass parameter for neutrinoless double beta decay is 0.03-0.05 eV. We also find the interesting relation tan 2 θ_13 ~ [Δm^2_{\odot} / Δm^2_{atm}] [sin 2 θ_12 /tan 2 θ_23] <~ 0.…
We investigate the hadronic production of the doubly heavy baryon $Ξ_{bc}$ at the large hadron collider (LHC), where contributions from the four $(bc)$-diquark states $(bc)_{\bf\bar{3},6}[^1S_0]$ and $(bc)_{\bf\bar{3},6}[^3S_1]$ have been taken into consideration. Numerical results show that under the condition of $p_T>4$ GeV and $|y|<1.5$, sizable $Ξ_{bc}$ events about $ 1.7\times 10^7$ and $3.5\times10^9$ per year can be produced for the center-of-mass energy $\sqrt{S}=7$ TeV and $\sqrt{S}=14$ TeV respectively. For experimental usage, the total and the interested differential cross-sections …
We review the SM extensions with scalar multiplets including doubly-charged components eventually observable as di-leptonic resonances at the LHC. Special emphasis is payed to the limits on LNV implied by doubly-charged scalar searches at the LHC, and to the characterization of the multiplet doubly-charged scalars belong to if they are observed to decay into same-sign charged lepton pairs.
We examine the same-sign single dilepton productions of $\ell_i^{\pm}\ell_j^{\pm} (\ell_{i,j}=e,μ)$ in high-energy proton-proton collisions at the Large Hadron Collider (LHC) in models with doubly charged Higgs scalars as well as heavy Majorana neutrinos. We demonstrate that these spectacular productions can be detected at the LHC for a class model in which the doubly charged Higgs scalars couple only to the right-handed charged leptons. The ranges of the possible doubly charged Higgs masses and mixings to observe the processes at the LHC are discussed.
Low-mass doubly-charged Higgs bosons at LHC
研究低质量双电荷希格斯玻色子在LHC上的探测，通过多变量分析区分异常喷射与标准模型喷射，并提出新的搜索方法，发现其可能通过已收集的Run 2 LHC数据直接探测。
The doubly charged Higgs bosons $H^{\pm\pm}$ searches at the Large Hadron Collider (LHC) have been studied extensively and strong bound is available for $H^{\pm\pm}$ dominantly decaying into a pair of same-sign di-leptons. In this paper we point out that there is a large cavity in the light $H^{\pm\pm}$ mass region left unexcluded. In particular, $H^{\pm\pm}$ can dominantly decay into $WW$ or $WW^*$ (For instance, in the type-II seesaw mechanism the triplet acquires a vacuum expectation value around 1 GeV.), and then it is found that $H^{\pm\pm}$ with mass even below $2m_W$ remains untouched b…
We present a detailed discussion on the doubly charmed baryon $Ξ_{cc}$ production at the RHIC and LHC via the proton-nucleus ($p$-N) and nucleus-nucleus (N-N) collision modes. The extrinsic charm mechanism via the subprocesses $g+c\to (cc)[n]+\bar{c}$ and $c+c\to (cc)[n]+g$ together with the gluon-gluon fusion mechanism via the subprocess $g+g\to(cc)[n]+\bar{c}+\bar{c}$ have been taken into consideration, where the intermediate diquark is in $[n]=[^1S_0]_{\bf 6}$-state or $[^3S_1]_{\bar{\bf 3}}$-state, respectively. Total and differential cross sections have been discussed under various collis…
Probing long-lived doubly charged scalar in the Georgi-Machacek model at the LHC and in far detectors
本文研究在LHC和远探测器中探测Georgi-Machacek模型中长寿命双电荷标量的潜力，通过分析位移顶点等信号特征，结合LHC与远探测器搜索，预计可覆盖质量50至180 GeV下大部分参数空间。
We have investigated production of doubly charged Higgs particles $Δ_{L,R}^{++}$ via WW fusion process in proton-proton collisions at LHC energies in the framework of the left-right symmetric model. The production cross section of the right-triplet Higgs is for representative values of model parameters at femtobarn level. The discovery reach depends on the mass of the right-handed gauge boson W_R. At best $Δ_R^{++}$ mass up to 2.4 TeV are achievable within one year run. For $Δ^{++}_L$ the corresponding limit is 1.75 TeV which depends on the value of the left-triplet vev v_L. Comparison with Dr…
The only possible doubly-charged scalar decays into two Standard Model particles are into pairs of same-sign charged leptons, H$^{\pm\pm}\rightarrow {l}^\pm {l}^\pm, {l} = e, μ, τ$, or gauge bosons, H$^{\pm\pm}\rightarrow W^\pm W^\pm$; being necessary the observation of both to assert the violation of lepton number. However, present ATLAS and CMS limits on doubly-charged scalar production are obtained under specific assumptions on its branching fractions into dileptons only. Although they can be extended to include decays into dibosons and lepton number violating processes. Moreover, the produ…
We analyze the next-to-leading order QCD corrections to the production of doubly-charged Higgs particles at hadron colliders in extensions of the SM with Higgs isospin triplets. At both the Tevatron and the LHC, these corrections are found to be moderate in size increasing the cross sections by about 20--30%. The residual theoretical uncertainties are of the order of 10--15% which is sufficient for experimental searches for these particles at the Tevatron and LHC.
Invited "News & Views" for the journal, SCIENCE CHINA: Physics, Mechanics & Astronomy, on a recently new search for the doubly charmed baryon $Ξ_{cc}^+$ at the LHC, which is done by the LHCb Collaboration, arXiv:1909.12273.
In type II seesaw model of neutrino mass generation, we study a remarkable signal of same-sign tetra-lepton (SS4L) signal at the Large hadron collider. When doubly charged Higgs is lightest, the heavier singly charged or neutral Higgs boson produces a doubly charged Higgs boson through its fast gauge decay. This leads to a novel signature of same-sign tetra-leptons resulting from a pair production of same-sign doubly charged Higgs bosons. We study production cross section for the SS4L signal in parameter space of the mass splitting among triplet components and the triplet vacuum expectation va…
We consider the production at the LHC of exotic composite leptons of charge Q=+2e. Such states are allowed in composite models which contain extended isospin multiplets (Iw=1 and Iw=3/2). These doubly charged leptons couple with Standard Model [SM] fermions via gauge interactions, thereby delineating and restricting their possible decay channels. We discuss the production cross section at the LHC of L++ (p p --> L++, l-) and concentrate on the leptonic signature deriving from the cascade decays L++ --> W+, l+ --> l+, l+, ν_l i.e. p p --> l-, l+, l+, ν_l showing that the invariant mass distribu…
We consider the minimal 3-3-1 model with three sterile neutrinos transforming as singlet under the $SU(3)_L\otimes U(1)_X$ symmetry. This model, with or without sterile neutrinos, predicts flavor violating interactions in both quark and lepton sectors, since all the charged fermions mass matrices can not be assumed diagonal in any case. Here we accommodate the lepton masses and the Pontecorvo-Maki-Nakawaga-Sakata matrix at the same time, and as consequence the Yukawa couplings and the unitary matrices which diagonalize the mass matrices are not free parameters anymore. We study some phenomenol…
In the framework of diquark model for production we discuss the yields and observation prospects for excited states of doubly heavy baryons at LHC kinematic conditions.
No process without a standard model (SM) background has been observed so far. As a tool in the study of a class of models containing doubly charged vector bileptons, we propose one such process that, violating lepton flavor number conservation, has no contribution from the SM: $pp\to μ^+μ^+μ^- e^-$. By carefully isolating the parameters to keep them free, we are able to acquire a notion of how a possible PMNS-like matrix present in the relevant charged current parametrization could affect the observables. We find that an interesting section of the space of parameters can be explored at the cur…
Search for doubly charged scalars in type-II seesaw mechanism through photon fusion at the LHC
针对II型跷跷板机制预言的双荷标量粒子Δ±±，研究其在14 TeV LHC上通过光子聚变伴随质子超周边碰撞的成对产生，基于不同中微子质量层级末态提出搜索策略，获得了显著的质量排除限，为探索新物理提供新途径。
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