Improving the sensitivity of stop searches with on-shell constrained invariant mass variables

Cho, Won Sang; Gainer, James S.; Kim, Doojin; Matchev, K.; Moortgat, F.; Pape, L.; Park, Myeonghun

doi:10.1007/jhep05(2015)040

Cited by 23 publications

(23 citation statements)

References 165 publications

(245 reference statements)

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“…These are shown for both the bino-dominated LSP (left) and the singlino-dominated LSP (right) cases. Note 11 Various strategies to probe the stops squarks in difficult situations with compressed spectrum are proposed in the literature (see, for example, references [112][113][114] and references therein). Table 4.…”

Section: Diagrammentioning

confidence: 99%

Two light stops in the NMSSM and the LHC

Beuria

Chatterjee

Datta

et al. 2015

J. High Energ. Phys.

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Abstract:We study the viability of having two relatively light top squarks ('stops') in the framework of the Next-to-Minimal Supersymmetric Standard Model (NMSSM). Such light stops render the NMSSM rather 'natural'. These are shown to be allowed by the relevant direct searches at the Large Hadron Collider (LHC) and to be compatible with the latest LHC results on the Higgs sector, other low energy electroweak constraints and recent constraints from the dark matter (DM) sector. We propose dedicated searches for such light stops at the LHC within a 'simplified' scenario that may have a bino-like or a singlino-like neutralino LSP as the DM candidate and point out various final states carrying the imprint of their collective presence. Under certain circumstances, in such a scenario, presence of two light stops may give rise to final states which are not so typical in their search. Thorough studies at the detector level reveal the status of such a scenario after the 8 TeV run of the LHC and shed light on the prospects of its 13 and 14 TeV runs. In favorable regions of the NMSSM parameter space, with low-lying spectra, signals with significance 5σ are possible with a few tens to a few hundreds of fb −1 of integrated luminosity in diverse final states.

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Section: Diagrammentioning

confidence: 99%

Two light stops in the NMSSM and the LHC

Beuria

Chatterjee

Datta

et al. 2015

J. High Energ. Phys.

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“…Very detailed measurements of the shapes of the tails of E T -sensitive observables [26] or their multivariate generalizations [27] may be promising, but a careful accounting of theoretical and experimental errors is not always available, and the one measurement of this type that has been carried out [2] (by ATLAS, in the l+jets channel) does not reach the compression line. A simple cut-and-count style search based on dileptonic m T 2 [28,29] or related constrained mass variables [30] should still be viable due to a particularly sharp turnoff of the background, and is also sensitive near the stealth point. But the maximum mass reach of such a search is ultimately limited by low statistics and exhibits a significant dependence on stop chirality.…”

Section: Jhep03(2016)151mentioning

confidence: 99%

Revealing compressed stops using high-momentum recoils

Macaluso

Park

Shih

et al. 2016

J. High Energ. Phys.

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Searches for supersymmetric top quarks at the LHC have been making great progress in pushing sensitivity out to higher mass, but are famously plagued by gaps in coverage around lower-mass regions where the decay phase space is closing off. Within the common stop-NLSP/neutralino-LSP simplified model, the line in the mass plane where there is just enough phase space to produce an on-shell top quark remains almost completely unconstrained. Here, we show that is possible to define searches capable of probing a large patch of this difficult region, with S/B ∼ 1 and significances often well beyond 5σ. The basic strategy is to leverage the large energy gain of LHC Run 2, leading to a sizable population of stop pair events recoiling against a hard jet. The recoil not only re-establishes a E T signature, but also leads to a distinctive anti-correlation between the E T and the recoil jet transverse vectors when the stops decay all-hadronically. Accounting for jet combinatorics, backgrounds, and imperfections in E T measurements, we estimate that Run 2 will already start to close the gap in exclusion sensitivity with the first few 10s of fb −1 . By 300 fb −1 , exclusion sensitivity may extend from stop masses of 550 GeV on the high side down to below 200 GeV on the low side, approaching the "stealth" point at mt = m t and potentially overlapping with limits from tt cross section and spin correlation measurements.

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“…In figure 12 we present the p T distribution of the harder lepton (left panel) and the E T distribution (right panel) which clearly demonstrate how similar the behaviors of the SM background and the signal could get. In this context, techniques to exploit differences in spin-correlations inherent to tt and t t * systems [82], use of various transverse mass variables [143] including the one like m T2 in the dileptonic decay channel [144], incorporating a new variable like 'topness' [145] using asymmetric decays of the top squarks have been proposed to study the 'stealth' top squark regime in search for an improved sensitivity. Clearly the issue demands dedicated addressal which is beyond the scope of the present discussion.…”

Section: The 'Stealth' Top Squark Scenariomentioning

confidence: 99%

Light top squarks in aU(1)Rlepton number model with a right handed neutrino and the LHC

Chakraborty¹,

Datta²,

Huitu³

et al. 2016

Phys. Rev. D

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Light top squarks in U (1) R lepton number model with a right handed neutrino and the LHC We investigate the phenomenology of top squarks at the Large Hadron Collider (LHC) in a supersymmetric model where lepton number is identified with an approximate U (1)R symmetry in such a way that one of the left chiral sneutrinos can acquire a large vacuum expectation value (vev) and can play the role of the down-type Higgs. This R-symmetry allows a subset of trilinear R-parity violating interactions, which determine the collider phenomenology of this model in a significant way. The gauginos are Dirac particles and gluinos are relatively heavy in this class of models. The model contains a right handed neutrino superfield, which gives a tree level mass to one of the active neutrinos. An order one neutrino Yukawa coupling also helps enhance the Higgs boson mass at the tree level and results in a very light bino-like neutralino ( χ 0 2 ) with mass around a few hundred MeV, which is a carrier of missing (transverse) energy (✚ ET ). The model can accommodate two rather light top squarks, compatible with the observed mass of the Higgs boson. The lighter top squark ( t1) can decay into t χ 0 2 , and thus the signal would be similar to the signal of top quark pair production at the LHC. In addition, fully visible decays such as t2 → be + can give rise to interesting final states. Such signals at the LHC combined with other features like a heavy gluino could provide a strong evidence for this kind of a model. Our analysis shows that m t 1 < ∼ 575 (750) GeV and m t 2 < ∼ 1.2 (1.4) TeV can be probed with 5σ statistical significance at the 13 TeV LHC with 300 (3000) fb −1 of integrated luminosity. Finally, we observe that in the presence of super-light carriers of ✚ ET , the so-called 'stealth' top squark scenario may naturally appear in our model. I. INTRODUCTIONThe discovery of a Higgs boson at the Large Hadron Collider (LHC) with a mass around 125 GeV [1, 2] is of immense importance in high energy physics and, in particular, in the context of electroweak symmetry breaking. However, in spite of its enormous success over the years, the Standard Model (SM) of particle physics suffers from several drawbacks. From a theoretical perspective, the naturalness problem remains a troublesome issue in the framework of SM. Supersymmetry (SUSY) renders an elegant solution to this problem and has become the most popular choice for physics beyond the standard model (BSM) to date. Nevertheless, searches for superpartners by the LHC collaborations (ATLAS and CMS) in pp collisions at the centre-of-mass energies of √ s = 7 TeV and 8 TeV have shown no significant excess [3,4] over the SM background. This has put stringent lower limits on the superpartner masses in many different SUSY scenarios. Recent experimental analyses within the framework of a simplified phenomenological minimal supersymmetric standard model (pMSSM) have set a lower bound of 1.7 TeV [5] for comparable masses of the gluino and the first two generation squarks.On top of that, find...

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Improving the sensitivity of stop searches with on-shell constrained invariant mass variables

Cited by 23 publications

References 165 publications

Two light stops in the NMSSM and the LHC

Two light stops in the NMSSM and the LHC

Revealing compressed stops using high-momentum recoils

Light top squarks in aU(1)Rlepton number model with a right handed neutrino and the LHC

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