Forward-backward asymmetries of the bottom and top quarks in warped extra-dimensional models: LHC predictions from the LEP and Tevatron anomalies

Djouadi, Abdelhak; Richard, Francois; Moreau, Gregory

doi:10.1016/j.physletb.2011.06.028

Article
Report number	arXiv:1105.3158 ; CERN-PH-TH-2011-114 ; LPT-ORSAY-11-40 ; CERN-PH-TH-2011-114 ; LPT-ORSAY-11-40
Title	Forward-backward asymmetries of the bottom and top quarks in warped extra-dimensional models: LHC predictions from the LEP and Tevatron anomalies
Author(s)	Djouadi, Abdelhak (Orsay, LPT ; CERN) ; Moreau, Gregory (Orsay, LPT) ; Richard, Francois (Orsay, LAL ; Orsay)
Publication	2011
Imprint	17 May 2011
Number of pages	13
Note	13 pages, 7 figures, new references and a note added on recent ATLAS results
In:	Phys. Lett. B 701 (2011) 458-464
DOI	10.1016/j.physletb.2011.06.028
Subject category	Particle Physics - Phenomenology
Abstract	Within the paradigm of warped extra dimensions, third generation quarks are expected to be the most sensitive to effects beyond the Standard Model. The anomalies observed at the LEP and Tevatron colliders in the forward-backward asymmetries of the bottom (A_FB^b) and top (A_FB^t) quarks can thus be seen as early signatures of warped extra-dimensional scenarios. We propose a realization of such a scenario, with a gauge custodial symmetry in the bulk, which allows to address simultaneously the A_FB^b anomaly and the discrepancies observed recently on A_FB^t at high top quark rapidities and ttbar invariant masses. We also show that the various phenomenological constraints arising from LEP, Tevatron and LHC can be satisfied within the considered model. The model predicts new features, induced by a Kaluza-Klein excitation of the gluon at a mass 1.5-2 TeV, in top quark pair production at the 7 TeV LHC.
Copyright/License	Preprint: © 2011-2025 CERN (License: CC-BY-3.0)

$\small{Left~: The FB asymmetry for the partonic process $q \bar q \to t \bar t$ as a function of the $t\bar t$ invariant mass (in GeV) in the SM at NLO, $\hat A_{\rm FB}^{\rm SM-NLO}(\hat s)$ [blue line], at LO with the RS contribution, $\hat A_{\rm FB}^{\rm LO} (\hat s)$ [dashed red curve] and at NLO, $\hat A_{\rm FB}^{\rm NLO}(\hat s)$ (being the sum of the previous ones) [plain red curve]. We have taken $m_t=172.5$~GeV. Right~: The partonic cross sections $\hat \sigma_{\rm SM-LO}$ (in pb) [blue curve] and $\hat \sigma_{\rm RS+SM+inter.-LO}$ [red curve] for $q \bar q \to t \bar t$.}$ $\small{Left~: The FB asymmetry for the partonic process $q \bar q \to t \bar t$ as a function of the $t\bar t$ invariant mass (in GeV) in the SM at NLO, $\hat A_{\rm FB}^{\rm SM-NLO}(\hat s)$ [blue line], at LO with the RS contribution, $\hat A_{\rm FB}^{\rm LO} (\hat s)$ [dashed red curve] and at NLO, $\hat A_{\rm FB}^{\rm NLO}(\hat s)$ (being the sum of the previous ones) [plain red curve]. We have taken $m_t=172.5$~GeV. Right~: The partonic cross sections $\hat \sigma_{\rm SM-LO}$ (in pb) [blue curve] and $\hat \sigma_{\rm RS+SM+inter.-LO}$ [red curve] for $q \bar q \to t \bar t$.}$ $\small{Left~: The full top quark asymmetry integrated in the two energy ranges $[350,450]$ and $[450,900]$ of invariant mass $M_{t\bar t}$ (in GeV) computed within the RS extension of the SM, $A_{\rm FB}^t$, with $\mu_{\rm F}=\mu_{\rm R}=m_t=172.5$~GeV [red lines] and compared to the SM prediction at NLO, $A_{\rm FB}^{\rm SM}$ [blue lines] as well as to the unfolded CDF data for $m_t=172.5$~GeV \cite{CDF11010034} [black crosses for experimental errors]. In the first energy bin, $A_{\rm FB}^{\rm SM}$ is at $1.0\sigma$ from data whereas $A_{\rm FB}^t$ is at $1.7\sigma$; in the second energy bin, $A_{\rm FB}^{\rm SM}$ is at $-3.4\sigma$ from data whereas $A_{\rm FB}^t$ is away by $-1.7\sigma$. Right~: The asymmetries $A_{\rm FB}^{\vert\Delta y\vert<1}$ and $A_{\rm FB}^{\vert\Delta y\vert>1}$ computed in the RS extension [red lines] and compared to the SM prediction at NLO [blue lines] as well as to the unfolded CDF data \cite{CDF11010034} [black crosses]. In the highest bin, $A_{\rm FB}^{\vert\Delta y\vert>1}$ in the SM is at $-1.9\sigma$ from data whereas $A_{\rm FB}^{\vert\Delta y\vert>1}$ in RS is away by $-1.3\sigma$.}$ Show more plots

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