我们提出了一种研究LHC上通过胶子-胶子融合产生双希格斯粒子的新方法。涉及两个标准模型类希格斯玻色子$hh$的相关费曼图在简化模型框架内进行计算，该框架使得能够以模型无关的方式解释新物理的可能信号，并将这些信号映射到特定理论上。这是通过将这种信号过程分解为其所有振幅平方及其相对干涉项来实现的，每一项都具有明确的耦合结构。我们以最小和次最小超对称表示为案例展示了这一过程的威力，在这些情况下，新物理效应源于进入$gg\ o hh$环中的顶squark。Squark既改变了积分截面，又在微分分布中相对于标准模型产生了独特的运动学特征。这些效应可以追溯到相关的图解和耦合结构，并允许对该过程进行详细分析。为此，我们对这些新物理场景的参数空间进行了系统扫描，并确定了在当前和即将进行的LHC运行中可能具有可观测特征的基准点。
英文摘要：
We present a novel approach to the study of di-Higgs production via gluon-gluon fusion at the LHC. The relevant Feynman diagrams involving two Standard Model-like Higgs bosons $hh$ are computed within a simplified model approach that enables one to interpret possible signals of new physics in a model-independent way as well as to map these onto specific theories. This is possible thanks to a decomposition of such a signal process into all its squared amplitudes and their relative interferences, each of which has a well-defined coupling structure. We illustrate the power of this procedure for the case of both a minimal and next-to-minimal representation of Supersymmetry, for which the new physics effects are due to top squarks entering the loops of $gg\to hh$. The squarks yield both a change of the integrated cross section and peculiar kinematic features in its differential distributions with respect to the Standard Model. These effects can in turn be traced back to the relevant diagrammatic and coupling structures and allow for a detailed analysis of the process. In order to do so, we perform systematic scans of the parameter spaces of such new physics scenarios and identify benchmark points which exhibit potentially observable features during the current and upcoming runs of the LHC.
Impact of squark generation mixing on the search for squarks and gluinos at LHC
在最小超对称标准模型（MSSM）下，研究了LHC中夸克生成混合对夸克和胶子产生和衰变的影响。我们发现，混合效应可以是非常大的平方代混合参数的一个显着范围内，尽管非常强的约束夸克味违反（QFV）从B介子的实验数据。我们发现在有利的条件下，QFV衰变分支比B（Gluino -> c bar{t}（t bar{c}）neutralino_1）可以高达50%，这可能导致在LHC上产生显著的QFV信号。我们还发现夸克生成混合可以在粲顶夸克不变质量分布中产生一种新的多边（3边或4边）结构。此外，我们还发现由于混合效应，两个最轻的上型方核~ u_{1,2}可以同时对衰变~u_i -> c neutralino_1和~u_i -> t neutralino_1产生很大的分支比，从而在LHC上以显著的速率产生QFV信号“pp -> c bar{t}（t bar{c}）+ missing-E_T + X”.这些显着的签名可以提供一个强有力的测试超对称QFV在LHC和可能有重要的影响，寻找方和胶子和MSSM参数的确定在LHC。
在最小超对称标准模型（MSSM）中，研究了夸克世代混合对夸克和胶子产生和衰变的影响，重点研究了第二代和第三代夸克的混合.考虑到从B-物理实验的限制，我们表明，在参数空间中存在的各种区域的夸克和/或胶子衰变到夸克味违反（QFV）的最终状态可以有大的分支比。这里我们考虑正方体的费米子衰变和玻色子衰变。相应的QFV信号的速率，例如pp -> t t bar{c} bar{c} missing-E_T X，在LHC（14 TeV）处可以是显著的。我们发现，列入味混合效应可以是重要的搜索的方和胶子和确定的MSSM在LHC的基本模型参数。
We investigate possible scenarios of light-squark production at the LHC as a new mechanism to produce Higgs bosons in association with jets. The study is motivated by the SUSY search for H+jets events, performed by the CMS collaboration on 8 and 13 TeV data using the razor variables. Two simplified models are proposed to interpret the observations in this search. The constraint from Run I and the implications for Run II and beyond are discussed.
Dirac gauginos are a well-motivated extension of the MSSM, leading to interesting phenomenological consequences. At the LHC, gluino-pair production is enhanced while squark production is suppressed as compared to the MSSM, and the decay signatures are altered by a more complex chargino and neutralino spectrum. We investigate how this impacts current gluino and squark mass limits from Run~2 of the LHC. Concretely, we compare different assumptions about the electroweak-ino spectrum through four benchmark models paying particular attention to the effect of the trilinear $λ_S$ coupling, which indu…
We present predictions for the total cross sections for pair production of squarks and gluinos at the LHC including a combined NNLL resummation of soft and Coulomb gluon effects. We derive all terms in the NNLO cross section that are enhanced near the production threshold, which include contributions from spin-dependent potentials and so-called annihilation corrections. The NNLL corrections at $\sqrt{s}=13$ TeV range from up to $20\%$ for squark-squark production to $90\%$ for gluino pair production relative to the NLO results and reduce the theoretical uncertainties of the perturbative calcul…
We perform a threshold resummation calculation for the associated production of squarks and electroweakinos at the LHC to the next-to-leading logarithmic (NLL) accuracy. Analytical results for the process-dependent soft anomalous dimension and the hard matching coefficient are presented. The resummed results are matched to fixed-order predictions at next-to-leading order (NLO) in QCD, which are generalised to scenarios with non-universal squark masses and mixings. Numerically, the NLL contributions increase the total NLO cross section by $2\%$ to $6\%$ for squark masses ranging from 1 TeV to 3…
Impact of squark generation mixing on the search for gluinos at LHC
在最小超对称标准模型（MSSM）中，研究了平方生成混合对胶子衰变的影响。我们发现，尽管B介子观测量对夸克味破坏（QFV）的实验约束很强，但由于这种效应，在MSSM参数空间的相当一部分，QFV的胶子衰变分支比B（胶子-> c bar{t}（t bar{c}）+中性子1）可以很大（高达~50%）.这可能对寻找胶子和在LHC上确定MSSM参数产生重要影响。
Impact of squark generation mixing on the search for gluinos at LHC
本文研究了具有夸克生成混合的最小超对称标准模型（MSSM）中的胶子衰变。我们表明，这种混合的影响上的胶子衰变分支比可以是非常大的一个重要部分的MSSM参数空间，尽管非常强的实验约束夸克味违反（QFV）从B介子观测。特别是我们发现，在较好的条件下，QFV胶子衰变胶子-> c bar{t}（bar{c} t）+ neutralino_1的分支比可达50%.我们还发现，夸克生成混合可以导致在粲顶夸克不变质量分布的多边缘（3-或4-边缘）的结构。这个显著结构的出现为LHC上的超对称QFV提供了一个额外的强有力的测试。这将对寻找胶子和在LHC上确定MSSM参数产生重要影响。
The higgsino Lightest Supersymmetric Particle (LSP) scenario opens up the possibility of decays of strongly produced particles to an intermediate neutralino, due to the Yukawa-suppressed direct decays to the higgsino. Those decays produce multijet signals with a Higgs or a $Z$ boson being produced in the decay of the intermediate neutralino to the LSP. In this paper we study the discovery prospects of squarks that produce $b$-jets and leptons in the final state. Our collider analysis provides signal significances at the 3$σ$ level for luminosities of 1 ab$^{-1}$, and at the 5$σ$ level if we pr…
We utilize the recent LHC-13 TeV data to study the lower mass bound on top-squark (stop) in natural supersymmetry. We recast the LHC sparticle inclusive search of $(\ge 1){\rm jets} + E^{miss}_T$ with $α_T$ variable, the direct stop pair search (1-lepton channel and all-hadronic channel) and the monojet analyses. We find that these searches are complementary depending on stop and higgsino masses: for a heavy stop the all-hadronic stop pair search provides the strongest bound, for an intermediate stop the inclusive SUSY analysis with $α_T$ variable is most efficient, while for a compressed stop…
We study the potential of the LHC accelerator, and a future 33 TeV proton collider, to observe the production of a light top squark pair in association with the lightest Higgs boson (${\tilde t}_1 {\tilde t}_1 h_1$), as predicted by the Next-to-Minimal Supersymmetric Standard Model (NMSSM). We scan randomly about ten million points of the NMSSM parameter space, allowing all possible decays of the lightest top squark and lightest Higgs boson, with no assumptions about their decay rates, except for known physical constraints such as perturbative bounds, Dark matter relic density consistent with …
Light top squarks (stops) and light higgsinos are the key features of natural SUSY, where the higgsinos $\tildeχ^{\pm}_{1}$ and $\tildeχ^0_{1,2}$ are nearly degenerate and act as the missing transverse energy ($E^{miss}_T$) at the LHC. Besides the strong production, the stop can be produced via the electroweak interaction. The determination of the electroweak properties of the stop is an essential task for the LHC and future colliders. So in this paper, we investigate the single stop ($\tilde{t}_1$) production $pp \to \tilde{t}_1+ E^{miss}_T$ in the natural SUSY at the LHC, which gives the mon…
The comparison of the results of direct detection of Dark Matter, obtained with various target nuclei, requires model-dependent, or even arbitrary, assumptions. Indeed, to draw conclusions either the spin-dependent (SD) or the spin-independent (SI) interaction has to be neglected. In the light of the null results from supersymmetry searches at the LHC, the squark sector is pushed to high masses. We show that for a squark sector at the TeV scale, the framework used to extract contraints from direct detection searches can be redefined as the number of free parameters is reduced. Moreover, the co…
We explore signatures related to squark decays in the framework of non-minimally flavour-violating Supersymmetry. We consider a simplified model where the lightest squark consists of an admixture of charm and top flavour. By recasting the existing LHC searches for top and charm squarks, we show that the limits on squark masses from these analyses are significantly weakened when the top-charm mixing is sizeable. We propose a dedicated search for squarks based on the $tc+{E_{\mathrm{T}}^{\mathrm{miss}}}$ final state which enhances the experimental sensitivity for the case of high mixing, and we …
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 examine the detection prospects for a long-lived bi$ν$o, a pseudo-Dirac bino which is responsible for neutrino masses, at the LHC and at dedicated long-lived particle detectors. The bi$ν$o arises in $U(1)_R$-symmetric supersymmetric models where the neutrino masses are generated through higher dimensional operators in an inverse seesaw mechanism. At the LHC the bi$ν$o is produced through squark decays and it subsequently decays to quarks, charged leptons and missing energy via its mixing with the Standard Model neutrinos. We consider long-lived bi$ν$os which escape the ATLAS or CMS detector…
