Abstract
In supersymmetric extensions of the Standard Model, the superpartners of the top quark (stops) play the crucial role in addressing the naturalness problem. For direct pair-production of stops with each stop decaying into a top quark plus the lightest neutralino, the standard stop searches have difficulty finding the stop for a compressed spectrum where the mass difference between the stop and the lightest neutralino is close to the top quark mass, because the events look too similar to the large \( t\overline{t} \) background. With an additional hard ISR jet, the two neutralinos from the stop decays are boosted in the opposite direction and they can give rise to some missing transverse energy. This may be used to distinguish the stop decays from the backgrounds. In this paper we study the semileptonic decay of such signal events for the compressed mass spectrum. Although the neutrino from the W decay also produces some missing transverse energy, its momentum can be reconstructed from the kinematic assumptions and mass-shell conditions. It can then be subtracted from the total missing transverse momentum to obtain the neutralino contribution. Because it suffers from less backgrounds, we show that the semileptonic decay channel has a better discovery reach than the fully hadronic decay channel along the compressed line \( {m}_{\tilde{t}}-{m}_{\tilde{\chi}}\approx {m}_t \). With 300 fb−1, the 13 TeV LHC can discover the stop up to 500 GeV, covering the most natural parameter space region.
Article PDF
Similar content being viewed by others
Avoid common mistakes on your manuscript.
References
ATLAS collaboration, Observation of a new particle in the search for the standard model Higgs boson with the ATLAS detector at the LHC, Phys. Lett. B 716 (2012) 1 [arXiv:1207.7214] [INSPIRE].
CMS collaboration, Observation of a new boson at a mass of 125 GeV with the CMS experiment at the LHC, Phys. Lett. B 716 (2012) 30 [arXiv:1207.7235] [INSPIRE].
ATLAS collaboration, ATLAS Run 1 searches for direct pair production of third-generation squarks at the Large Hadron Collider, Eur. Phys. J. C 75 (2015) 510 [arXiv:1506.08616] [INSPIRE].
CMS collaboration, Search for direct pair production of supersymmetric top quarks decaying to all-hadronic final states in pp collisions at \( \sqrt{s}=8 \) TeV, arXiv:1603.00765 [INSPIRE].
CMS collaboration, Search for direct pair production of scalar top quarks in the single- and dilepton channels in proton-proton collisions at \( \sqrt{s}=8 \) TeV, submitted to JHEP, arXiv:1602.03169 [INSPIRE].
CMS collaboration, Search for direct top squark pair production in the single lepton final state at \( \sqrt{s}=13 \) TeV, CMS-PAS-SUS-16-002 (2016).
K. Hagiwara and T. Yamada, Equal-velocity scenario for hiding dark matter at the LHC, Phys. Rev. D 91 (2015) 094007 [arXiv:1307.1553] [INSPIRE].
H. An and L.-T. Wang, Opening up the compressed region of top squark searches at 13 TeV LHC, Phys. Rev. Lett. 115 (2015) 181602 [arXiv:1506.00653] [INSPIRE].
S. Macaluso, M. Park, D. Shih and B. Tweedie, Revealing compressed stops using high-momentum recoils, JHEP 03 (2016) 151 [arXiv:1506.07885] [INSPIRE].
J. Alwall, M. Herquet, F. Maltoni, O. Mattelaer and T. Stelzer, MadGraph 5: going beyond, JHEP 06 (2011) 128 [arXiv:1106.0522] [INSPIRE].
J. Alwall et al., The automated computation of tree-level and next-to-leading order differential cross sections and their matching to parton shower simulations, JHEP 07 (2014) 079 [arXiv:1405.0301] [INSPIRE].
T. Sjöstrand et al., An introduction to PYTHIA 8.2, Comput. Phys. Commun. 191 (2015) 159 [arXiv:1410.3012] [INSPIRE].
M.L. Mangano, M. Moretti, F. Piccinini, R. Pittau and A.D. Polosa, ALPGEN, a generator for hard multiparton processes in hadronic collisions, JHEP 07 (2003) 001 [hep-ph/0206293] [INSPIRE].
DELPHES 3 collaboration, J. de Favereau et al., DELPHES 3, a modular framework for fast simulation of a generic collider experiment, JHEP 02 (2014) 057 [arXiv:1307.6346] [INSPIRE].
M. Cacciari, G.P. Salam and G. Soyez, The anti-k t jet clustering algorithm, JHEP 04 (2008) 063 [arXiv:0802.1189] [INSPIRE].
M. Czakon and A. Mitov, Top++: a program for the calculation of the top-pair cross-section at hadron colliders, Comput. Phys. Commun. 185 (2014) 2930 [arXiv:1112.5675] [INSPIRE].
M. Botje et al., The PDF4LHC working group interim recommendations, arXiv:1101.0538 [INSPIRE].
A.D. Martin, W.J. Stirling, R.S. Thorne and G. Watt, Uncertainties on α s in global PDF analyses and implications for predicted hadronic cross sections, Eur. Phys. J. C 64 (2009) 653 [arXiv:0905.3531] [INSPIRE].
J. Gao et al., CT10 next-to-next-to-leading order global analysis of QCD, Phys. Rev. D 89 (2014) 033009 [arXiv:1302.6246] [INSPIRE].
R.D. Ball et al., Parton distributions with LHC data, Nucl. Phys. B 867 (2013) 244 [arXiv:1207.1303] [INSPIRE].
C. Borschensky et al., Squark and gluino production cross sections in pp collisions at \( \sqrt{s}=13 \) , 14, 33 and 100 TeV, Eur. Phys. J. C 74 (2014) 3174 [arXiv:1407.5066] [INSPIRE].
CMS collaboration, b-tagging in boosted topologies, CMS-DP-2015-038 (2015).
G. Cowan, K. Cranmer, E. Gross and O. Vitells, Asymptotic formulae for likelihood-based tests of new physics, Eur. Phys. J. C 71 (2011) 1554 [Erratum ibid. C 73 (2013) 2501] [arXiv:1007.1727] [INSPIRE].
Open Access
This article is distributed under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits any use, distribution and reproduction in any medium, provided the original author(s) and source are credited.
Author information
Authors and Affiliations
Corresponding author
Additional information
ArXiv ePrint: 1604.00007
Rights and permissions
Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0), which permits use, duplication, adaptation, distribution, and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.
About this article
Cite this article
Cheng, HC., Gao, C., Li, L. et al. Stop search in the compressed region via semileptonic decays. J. High Energ. Phys. 2016, 36 (2016). https://doi.org/10.1007/JHEP05(2016)036
Received:
Accepted:
Published:
DOI: https://doi.org/10.1007/JHEP05(2016)036