We study the impact of the multi-lepton searches at the LHC on supersymmetric models with compressed mass spectra. For such models the acceptances of the usual search strategies are significantly reduced due to requirement of large effective mass and missing E_T. On the other hand, lepton searches do have much lower thresholds for missing E_T and p_T of the final state objects. Therefore, if a model with a compressed mass spectrum allows for multi-lepton final states, one could derive constraints using multi-lepton searches. For a class of simplified models we study the exclusion limits using ATLAS multi-lepton search analyses for the final states containing 2-4 electrons or muons with a total integrated luminosity of 1-2/fb at \sqrt{s}=7 TeV. We also modify those analyses by imposing additional cuts, so that their sensitivity to compressed supersymmetric models increase. Using the original and modified analyses, we show that the exclusion limits can be competitive with jet plus missing E_T searches, providing exclusion limits up to gluino masses of 1 TeV. We also analyse the efficiencies for several classes of events coming from different intermediate state particles. This allows us to assess exclusion limits in similar class of models with different cross sections and branching ratios without requiring a Monte Carlo simulation.
Constraining non-commutative geometry with W/Z+jet production at the LHC
Université de Batna-1(巴特纳大学);Laboratoire de Physique des Rayonnements et de leurs Interactions avec la Matière, Département de Physique, Faculté des Sciences de la Matière, Université de Batna-1(巴特纳大学物质科学学院物理系辐射及其与物质相互作用物理实验室);Laboratoire de Physique Energétique Appliquée, Département de Physique, Faculté des Sciences de la Matière, Université de Batna-1(巴特纳大学物质科学学院物理系应用能源物理实验室)
Constraints from the decay B_s -> mu mu and LHC limits on Supersymmetry
纯轻子衰变B_s -> mu mu在标准模型(SM)中被强烈抑制,但在超对称性中可以有很大的增强,特别是在大的tanbe值下。从最近的LHC数据中对这个衰变通道的新限制已经被用来声称这些限制比直接搜索更能限制超对称参数空间。然而,直接搜索几乎不依赖于tanbe,而BR(B_s -> mu mu)与tanbe成正比^[6]。遗迹密度约束要求在参数空间的大区域中具有大的tanbe,这可能导致B_s -> mu mu的大值。然而,如果与遗迹密度相结合,BR(B_s -> mu mu)的实验上限并不比直接搜索和目前的Higgs极限更能约束CMSSM的参数空间。我们还观察到负干扰的超对称参数区域,其中B_s -> mu mu值比SM期望值低三倍,即使在大的tanbe值下。
Natural Supersymmetry and Implications for Higgs physics
我们重新分析了LHC边界轻第三代方在自然超对称性,其中的sparticles质量成反比,其领先的日志贡献的电弱对称性破缺规模。希格斯玻色子是最轻的超对称粒子;顶部和底部的正方形是次轻的超对称粒子,它们衰变为中性和带电的希格斯玻色子,其分支比由汤川耦合和运动学决定。一旦把比诺和维诺质量取到它们的自然(重)值,希格斯诺的质量几乎是简并的。我们考虑三种情况下停止和sbottom质量:(I)$\tilde{t}_R$是轻的,(II)$\tilde{t}_L$和$\tilde{b}_L$是轻的,(III)$\tilde{t}_R$,$\tilde{t}_L$,和$\tilde{b}_L$是轻的。目前,专用停靠点搜索对情景二和情景三敏感,但对情景一不敏感。由于$\tilde{t} \ra b \charp_1$和$\tilde{b} \ra b \neut_{1,2}$,底层动机搜索($2 b + \rm{MET}$)影响了两种squark风格,限制了场景I和III,对场景II的限制稍弱。这些搜索的总体结果对自然超对称性产生了相对较强的约束。剩下的两个地区是:(1)“压缩楔形”,其中$(m_{\tilde{q}} - |μ|)/m_{\tilde{q}} \ll 1$,和(2)“运动极限”区域,其中$m_{\tilde{q}} \gsim 600-750 GeV, at the kinemat…