Signs of tops from highly mixed stops

Journal of High Energy Physics, Jun 2015

Supersymmetric extensions of the Standard Model with highly mixed squark flavours beyond minimal flavour violation provide interesting scenarios of new physics, which have so far received limited attention. We propose a calculable realization of such scenarios in models of gauge mediation augmented with an extra interaction between the messengers and the up type squark. We compute the supersymmetric spectrum and analyze the flavour physics constraints on such models. In a simplified model approach, we show that scenarios with maximal squark flavour mixing result in interesting phenomenological signatures at the LHC. We show that the model can be probed up to masses of m ũ  ≲ 950 GeV in the single-top event topology at LHC14 with as little as 300 fb−1. The most distinctive signature of highly mixed scenarios, the same sign positive charge di-top, can be also probed to comparable squark masses at high luminosity LHC14.

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Signs of tops from highly mixed stops

Received: April Signs of tops from highly mixed stops Mihailo Backovi´c 0 1 2 4 Alberto Mariotti 0 1 2 Michael Spannowsky 0 1 2 3 0 Durham University , Durham DH1 3LE, U.K 1 and International Solvay Institutes , Pleinlaan 2, B-1050 Brussels , Belgium 2 Universite Catholique de Louvain , Louvain-la-neuve , Belgium 3 Institute for Particle Physics Phenomenology, Department of Physics 4 Center for Cosmology , Particle Physics and Phenomenology - CP3 Supersymmetric extensions of the Standard Model with highly mixed squark flavours beyond minimal flavour violation provide interesting scenarios of new physics, which have so far received limited attention. We propose a calculable realization of such scenarios in models of gauge mediation augmented with an extra interaction between the messengers and the up type squark. We compute the supersymmetric spectrum and analyze the flavour physics constraints on such models. In a simplified model approach, we show that scenarios with maximal squark flavour mixing result in interesting phenomenological signatures at the LHC. We show that the model can be probed up to masses of mu˜ . 950 GeV in the single-top event topology at LHC14 with as little as 300 fb−1. The most distinctive signature of highly mixed scenarios, the same sign positive charge di-top, can be also probed to comparable squark masses at high luminosity LHC14. bTheoretische Natuurkunde and IIHE/ELEM; Vrije Universiteit Brussel Contents 1 Introduction The model formulation Low energy constraints Extended gauge mediation Mass spectrum Simplified model Branching ratios Benchmark points Collider signatures Top signatures at LHC14 Production modes and cross sections Constraints from LHC8 Event generation and reconstruction Single-top channel Same sign top channel Conclusions Introduction s = 14 TeV, and – 1 – have recently been discussed in refs. [6–10]. possibly unusual flavor patterns. hence be a robust hint of large squark mixing. – 2 – The model formulation Low energy constraints first and the third generation. M = m˜2(I6×6 + δu) δRL δRR u u – 3 – Extended gauge mediation tial couplings induce large A-terms. – 4 – Z4 R-symmetry contribution is mf2˜ = X Crf˜gr4 2Λ2fs tion are Crgr2 Λ2 − 4d8Uπ2 cij λ2h m2UiUj = 256π4 cij λ2dU λ2dφ − 2 m2Qij = − 256π4 (y†.c.y)ij Λ – 5 – consider at least one stop to be quite heavy. Mgr = mf2˜ = by adding expressions (2.4), (2.5), (2.6). We also computed the contribution taken from [57] and are summarized in table 2. – 6 – Flavour Observable Imposed limit Neutron EDM |dn| [0.84, 1.16] [0.87, 1.08] [0.90, 1.06] [0.90, 1.17] [0.85, 1.13] [0.95, 1.01] [0.95, 1.03] [0.99, 1.01] [0.12, 1.87] [0.875, 1.125] [0.68, 1.34] [0.997, 1.003] ≤ 8.82 × 10−15 GeV ≤ 2.9 × 10−26 (e cm) HFAG [60] HFAG [60] HFAG [60] HFAG [60] HFAG [60] HFAG [60] HFAG [60] HFAG [60] HFAG [60] HFAG [60] SUSYFLAVOR SUSYFLAVOR – 7 – two axes). formula in a fully flavored MSSM see e.g. [65]. to have a large enough Higgs mass. one light squark state. – 9 – |U14| U14 is the sup-stop mixing angle (here U15 ' 0). than few TeV’s. 1.9 × 105 GeV 2.31 × 106 GeV 446 GeV 1.56 TeV 526 GeV 260 GeV 124 GeV 2.5 × 105 GeV 2.315 × 106 GeV 657 GeV 1.99 TeV 688 GeV 345 GeV 124 GeV ∼ 0 ∼ 0 – 10 – m3/2 1/k × 612 eV m3/2 1/k × 614 eV the previous section. been recently discussed in [6]. explained in section 2.2. m3/2 = √3kMPl Simplified model – 11 – u˜1 + t∗/u∗ 1 u˜1 = √2 (u˜R + t˜R) collider analysis. mixture of sup and stop right-handed squarks u˜1 = √ (u˜R + t˜R). Branching ratios regions of the squark-neutralino plane [7]. few % level, but we do not consider it in the following. – 12 – of maximal mixing reads into tops drops abruptly. – 13 – Benchmark Point 1 2 TeV 450 GeV 200 GeV Benchmark Point 2 2 TeV 700 GeV 200 GeV Benchmark Point 3 2 TeV 700 GeV 400 GeV Benchmark Point 4 2 TeV 950 GeV 200 GeV Benchmark Point 5 2 TeV 950 GeV 400 GeV 10−1 2.0 TeV u˜1 mixing angles |U14| = |U15| = √1 |U14| = |U15| = √1 |U14| = |U15| = √1 |U14| = |U15| = √1 |U14| = |U15| = √1 2.0 TeV to 2 TeV. Benchmark points Collider signatures Production modes and cross sections the following production modes: pp → u˜1u˜1∗ pp → u˜1u˜1 pp → u˜1g˜ – 14 – ˜∗ ˜∗ t∗/u∗ we will not consider them in our analysis. a pure up squark. energy signatures. – 15 – figure 6) Constraints from LHC8 We find from the ATLAS jets plus E/ T search [71]. possible value at 8 TeV [78, 79]. 2.0 TeV 104000 mu˜ [ GeV ] channels (u˜1u˜∗, u˜1u˜1, u˜1g˜). The solid, blue curve is the same total cross section for the MMUT 1 the appropriate K-factors. reducing the efficiencies. – 17 – evaluation of the LHC reach see [80]. discuss its phenomenology at LHC14. leads to weaker bounds. duction modes (4.3) and (4.4) – 18 – Event generation and reconstruction and lepton isolation. process generation level. final state. Single-top channel direct top production is irrelevant. 7Here we define mT ≡ q2 plT E/ T (1 − cos(Δφl/ET ). – 19 – mT [ GeV ] 10−1 10−2 10−5 10−2 rbA10−4 400 500 600 700 800 /E T [ GeV ] mT [ GeV ] uncompressed mass spectrum scenario. kinematic cuts: E/ T > 250 GeV , mT > mTmin , – 20 – W + b¯b W + b¯b < 0.1 W + t < 0.1 W + t < 0.1 1.0 × 10−3 2.9 × 10−5 3.4 × 10−3 S/√B (300 fb−1) S/√B (300 fb−1) l + E/ T + b Nl = 1, Nb = 1 E/ T > 250 GeV mT > 210 GeV l + E/ T + b Nl = 1, Nb = 1 E/ T > 250 GeV mT > 410 GeV 0.093 0.12 0.13 0.36 0.48 4.1 × 104 0.30 0.34 order to improve the statistics in the signal region. (0.32, 20.0) (0.24, 11.0) (0.12,3.8) (0.11, 5.3) (0.11,3.4) show S/B and S/√ masses of roughly . 1 TeV.8 – 21 – charged leptons is an excellent candidate. cross sections. of figure 9. here we employ a set of cuts: E/ T > 120 GeV , mT (l1+) > mTmin , produce final states with two positive leptons. – 22 – 200 250 300 350 400 50 100 150 200 250 300 350 400 mT [ GeV ] 10−5 10−2 /E T [ GeV ] /E T [ GeV ] 0 100 200 300 400 500 600 700 800 0 100 200 300 400 500 600 700 800 mT [ GeV ] luminosity LHC. – 23 – l+l+ + E/ T + jj Nl+ = 2, Nl− = 0 Nj > 1 E/ T > 120 GeV mT > 200 GeV l+l+ + E/ T + jj Nl+ = 2, Nl− = 0 0.031 Nj > 1 E/ T > 120 GeV mT > 400 GeV < 0.01 0.014 0.0068 < 0.01 < 0.01 < 0.01 < 0.01 < 0.01 W +jets rare proc. S/√B(3000 fb−1) W +jets rare proc. S/√B (3000 fb−1) (0.21, 7.9) (0.31, 7.5) (0.26, 4.1) (0.22 , 5.3) (0.26, 4.0) Conclusions the context of the MSSM. – 24 – of the up type higgs soft mass: respectively. tuned than natural SUSY. Higgs mass. – 25 – at the LHC Run II. 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Mihailo Backović, Alberto Mariotti, Michael Spannowsky. Signs of tops from highly mixed stops, Journal of High Energy Physics, 2015, 122, DOI: 10.1007/JHEP06(2015)122