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Title: Hunting for the top partner in the littlest Higgs model with T parity at the CERN LHC

Abstract

We study the littlest Higgs model with T parity at the CERN LHC through pair productions of the T-odd top quark partner (T{sub -}) which decays into the top quark and the lightest T-odd particle. We identify the region of parameters favored by the electroweak and cosmological considerations. The signal and background events are simulated with fast detector simulation to study the discovery potential at the LHC. We find that the hemisphere analysis recently proposed by the CMS Collaboration is very useful to separate the signal from the tt background. We discuss the observability of the top tagged signal in the effective mass (M{sub eff}) versus the transverse missing energy (E{sub Tmiss}) plane. We show that, for all our sample parameter sets with M{sub T{sub -}}{<=}900 GeV, the excess of the signal over the background can be visible as a bump structure in the E{sub Tmiss} distribution for 50 fb{sup -1} at relatively high M{sub eff} intervals.

Authors:
; ;  [1]
  1. Theory Group, KEK, 1-1 Oho, Tsukuba, 305-0801 (Japan)
Publication Date:
OSTI Identifier:
21020091
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. D, Particles Fields; Journal Volume: 75; Journal Issue: 5; Other Information: DOI: 10.1103/PhysRevD.75.055006; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; CERN LHC; COSMOLOGY; DISTRIBUTION; EFFECTIVE MASS; ELECTROMAGNETIC INTERACTIONS; GEV RANGE; HIGGS MODEL; PAIR PRODUCTION; PARITY; PARTICLE DECAY; PARTICLE IDENTIFICATION; POTENTIALS; T QUARKS; TOPONIUM; WEAK INTERACTIONS

Citation Formats

Matsumoto, Shigeki, Nojiri, Mihoko M., and Nomura, Daisuke. Hunting for the top partner in the littlest Higgs model with T parity at the CERN LHC. United States: N. p., 2007. Web. doi:10.1103/PHYSREVD.75.055006.
Matsumoto, Shigeki, Nojiri, Mihoko M., & Nomura, Daisuke. Hunting for the top partner in the littlest Higgs model with T parity at the CERN LHC. United States. doi:10.1103/PHYSREVD.75.055006.
Matsumoto, Shigeki, Nojiri, Mihoko M., and Nomura, Daisuke. Thu . "Hunting for the top partner in the littlest Higgs model with T parity at the CERN LHC". United States. doi:10.1103/PHYSREVD.75.055006.
@article{osti_21020091,
title = {Hunting for the top partner in the littlest Higgs model with T parity at the CERN LHC},
author = {Matsumoto, Shigeki and Nojiri, Mihoko M. and Nomura, Daisuke},
abstractNote = {We study the littlest Higgs model with T parity at the CERN LHC through pair productions of the T-odd top quark partner (T{sub -}) which decays into the top quark and the lightest T-odd particle. We identify the region of parameters favored by the electroweak and cosmological considerations. The signal and background events are simulated with fast detector simulation to study the discovery potential at the LHC. We find that the hemisphere analysis recently proposed by the CMS Collaboration is very useful to separate the signal from the tt background. We discuss the observability of the top tagged signal in the effective mass (M{sub eff}) versus the transverse missing energy (E{sub Tmiss}) plane. We show that, for all our sample parameter sets with M{sub T{sub -}}{<=}900 GeV, the excess of the signal over the background can be visible as a bump structure in the E{sub Tmiss} distribution for 50 fb{sup -1} at relatively high M{sub eff} intervals.},
doi = {10.1103/PHYSREVD.75.055006},
journal = {Physical Review. D, Particles Fields},
number = 5,
volume = 75,
place = {United States},
year = {Thu Mar 01 00:00:00 EST 2007},
month = {Thu Mar 01 00:00:00 EST 2007}
}
  • In the littlest Higgs model with T-parity (LHT) the newly introduced mirror quarks have flavor-changing couplings with the standard model (SM) quarks and may enhance the flavor-changing neutral-current (FCNC) top-quark interactions which are extremely suppressed in the SM. In this work we perform a comprehensive study for the contributions of these mirror fermions to various top-quark FCNC decays and productions at the LHC, which includes the decays t{yields}cV (V=g, {gamma}, Z), t{yields}cgg and the productions proceeding through the parton processes cg{yields}t, gg{yields}tc, cg{yields}tg, cg{yields}t{gamma} and cg{yields}tZ. We find that although these FCNC processes can be greatly enhanced by the LHTmore » contributions, they are hardly accessible at the LHC. Therefore, the LHT model may not cause the FCNC problem in the top-quark sector if the top-quark property is proved to be SM-like at the LHC.« less
  • We consider the top-quark pair production at the upcoming LHC and investigate the contributions of the new particles to the related observables within the framework of the littlest Higgs model with T-parity(LHT). It is found that the LHT model can generate significant corrections to the tt production cross section and their spin correlations.
  • Higgs boson productions at the LHC will serve as a sensitive probe of various little Higgs models. In this work we comparatively study two littlest Higgs models with different T-parity constructions through examining their effects in three production processes of the Higgs boson at the LHC, namely, the productions of a single Higgs, a Higgs-pair, as well as a Higgs boson associated with a pair of top and antitop quarks. The two models are characterized by predicting a top partner with, respectively, even and odd T-parity, which cancels the Higgs mass quadratic divergence caused by the top quark. We findmore » that both models can alter the standard model cross sections sizably and their corrections also differ significantly. Therefore, the Higgs boson productions at the LHC might shed some light on these two models or even distinguish them.« less
  • In the framework of the littlest Higgs model with T parity (LHT), we study the production processes of T-even (T{sub +}) and T-odd (T{sub -}) partners of the top quark at the Large Hadron Collider (LHC). We show that the signal events can be distinguished from the standard model backgrounds, and that information about mass and mixing parameters of the top partners can be measured with relatively good accuracies. With the measurements of these parameters, we show that a nontrivial test of the LHT can be performed. We also discuss a possibility to reconstruct the thermal relic density of themore » lightest T-odd particle A{sub H} using the LHC results and show that the scenario where A{sub H} becomes dark matter may be checked.« less
  • We analyze the rare and flavor-changing decay of the top quark into a charm quark and a gauge boson in the littlest Higgs model with T parity (LHT). We calculate the one-loop level contributions from the T parity odd mirror quarks and gauge bosons. We find that the decay t{yields}cV, (V=g,{gamma},Z) in the LHT model can be significantly enhanced relative to those in the standard model. Our numerical results show that the top quark flavor-changing neutral current decay can be as large as Br(t{yields}cg){approx}10{sup -2}, Br(t{yields}cZ){approx}10{sup -5}, and Br(t{yields}c{gamma}){approx}10{sup -7} in the favorite parameter space in the LHT model.