New Physics from the Top at the LHC

Chen, Chien-Yi; Freitas, Ayres; Han, Tao; Lee, Keith S. M.

doi:10.48550/arxiv.1207.4794

Cited by 8 publications

(15 citation statements)

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“…The above signature appears in numerous new physics scenarios, see e.g. [90][91][92][93]. Since these three observables constitute a very powerful tool in the BSM physics searches we also plot them separately in Figures 24, 25 and 26, for the central scale only and for three different scale choices.…”

Section: Differential Distributionsmentioning

confidence: 99%

Off-shell top quarks with one jet at the LHC: a comprehensive analysis at NLO QCD

Bevilacqua

Hartanto

Kraus

et al. 2016

J. High Energ. Phys.

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We present a comprehensive study of the production of top quark pairs in association with one hard jet in the di-lepton decay channel at the LHC. Our predictions, accurate at NLO in QCD, focus on the LHC Run II with a center-of-mass energy of 13 TeV. All resonant and non-resonant contributions at the perturbative order O(α 4 s α 4 ) are taken into account, including irreducible backgrounds to ttj production, interferences and off-shell effects of the top quark and the W gauge boson. We extensively investigate the dependence of our results upon variation of renormalisation and factorisation scales and parton distribution functions in the quest for an accurate estimate of the theoretical uncertainties. Additionally, we explore a few possibilities for a dynamical scale choice with the goal of stabilizing the perturbative convergence of the differential cross sections far away from the tt threshold. Results presented here are particularly relevant for searches of new physics as well as for precise measurements of the top-quark fiducial cross sections and top-quark properties at the LHC.

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Section: Differential Distributionsmentioning

confidence: 99%

Off-shell top quarks with one jet at the LHC: a comprehensive analysis at NLO QCD

Bevilacqua

Hartanto

Kraus

et al. 2016

J. High Energ. Phys.

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“…Recent experimental searches for direct production of light stops [40][41][42][43][44][45] constrain much of the stop parameter space with m t1 < ∼ 500 GeV, but only for sufficiently light neutralinos. The more squeezed regime will be probed by a combination of traditional missing-E T signatures [46][47][48][49][50][51][52][53][54][55] and spin correlations [56], and even the case of R-parity violation may be constrained soon [57]. Nonetheless, for the moment, these considerations still allow as a logical possibility that light, highly mixed stops significantly alter the Higgs properties.…”

Section: Inverting Hgg With Stopsmentioning

confidence: 99%

Vacuum instabilities with a wrong-sign Higgs–gluon–gluon amplitude

Reece

2013

New J. Phys.

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The recently discovered 125 GeV boson appears very similar to a Standard Model (SM) Higgs, but with data favoring an enhanced h → γ γ rate. A number of groups have found that fits would allow (or, less so after the latest updates, prefer) that the htt coupling have the opposite sign. This can be given meaning in the context of an electroweak chiral Lagrangian, but it might also be interpreted to mean that a new colored and charged particle runs in loops and reinforces the W -loop contribution to h F F, while also producing the oppositesign hGG amplitude to that generated by integrating out the top. Due to a correlation in sign of the new physics amplitudes, when the SM h F F coupling is enhanced the hGG coupling is decreased. Thus, in order to not suppress the rate of h → W W and h → Z Z , which appear to be approximately SM-like, one would need the loop to 'overshoot', not only canceling the top contribution but producing an opposite-sign hGG vertex of about the same magnitude as that in the SM. We argue that most such explanations have severe problems with fine-tuning and, more importantly, vacuum stability. In particular, the case of stop loops producing an opposite-sign hGG vertex of the same size as the SM one is ruled out by a combination of vacuum decay bounds and Large Electron-Positron Collider (LEP) constraints. We also show that scenarios with a sign flip from loops of color octet charged scalars or new fermionic states are highly constrained.

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“…Using this signal topology, it has been found with 100 fb −1 luminosity a light stop mass up to 250 GeV can be probed [58]. Similarly the prospect of a spin zero top partner decaying to top quark and neutral particles was also studied in [63] and the expected discovery limit for light stop mass is close to 675 GeV with 100 fb −1 luminosity. The gluino-stop-neutralino model has been also studied in [68] with two top tagged jets and missing energy.…”

Section: Introductionmentioning

confidence: 91%

“…This together with the discovery of a SM higgs like boson has lead us to look beyond cMSSM, in particular at considering simplified models motivated by naturalness arguments and hence, light third generation sparticles in a general MSSM framework with no specific relations among the soft supersymmetry breaking parameters. This has motivated an avalanche of phenomenological studies in light stops and/or light sbottom scenarios [40,46,47,[56][57][58][59][60][61][62][63][64][65][66][67][68][69][70][71][72]. In terms of collider searches most phenomenological studies have been conducted for predominantly right handed stop and sbottom quarks in the decay channels t → t χ 0 and b 1 → b χ 0 1 [67,[73][74][75][76].…”

Section: Introductionmentioning

confidence: 99%

Stop and sbottom search using dileptonic MT2 variable and boosted top technique at the LHC

Chakraborty

Ghosh

et al. 2013

J. High Energ. Phys.

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The ATLAS and CMS experiments at the CERN LHC have collected about 25 fb −1 of data each at the end of their 8 TeV run, and ruled out a huge swath of parameter space in the context of Minimally Supersymmetric Standard Model (MSSM). Limits on masses of the gluino (g) and the squarks of the first two generations (q) have been pushed to above 1 TeV. Light third generation squarks namely stop and sbottom of sub-TeV masses, on the other hand, are still allowed by their direct search limits. Interestingly, the discovery of a Standard Model (SM) higgs boson like particle with a mass of ∼ 125 GeV favours a light third generation which is also motivated by naturalness arguments. Decays of stop and sbottom quarks can in general produce a number of distinct final states which necessitate different search strategies in the collider experiments. In this paper we, on the other hand, propose a general search strategy to look for third generation squarks in the final state which contains a top quark in the sample along with two additional hard leptons and substantial missing transverse momentum. We illustrate that a search strategy using the dileptonic M T2 , the effective mass m eff and jet substructure to reconstruct the hadronic top quark can be very effective to reduce the SM backgrounds. With the proposed search strategy, we estimate that the third generation squarks with masses up to about 900 GeV can be probed at the 14 TeV LHC with 100 fb −1 luminosity. We also interpret our results in two simplified scenarios where we consider the stop (sbottom) pair production followed by their subsequent decay to a top quark and the second lightest neutralino (lightest chargino). In this case also we find that stop (sbottom) mass up to 1 TeV (0.9 TeV) can be discovered at the 14 TeV LHC with 100 fb −1 integrated luminosity.

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New Physics from the Top at the LHC

Cited by 8 publications

References 0 publications

Off-shell top quarks with one jet at the LHC: a comprehensive analysis at NLO QCD

Off-shell top quarks with one jet at the LHC: a comprehensive analysis at NLO QCD

Vacuum instabilities with a wrong-sign Higgs–gluon–gluon amplitude

Stop and sbottom search using dileptonic MT2 variable and boosted top technique at the LHC

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