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Register a new userNew CP-odd Observable in H -> t bar{t}
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We study a CP-violating triple product correlation that occurs in the decay of a neutral Higgs boson into tbar{t} pairs when the Higgs boson does not have a definite CP nature. We consider the H -> t bar{t} decay channel as well as the gluon fusion process gg -> H -> t bar{t}. The asymmetry in Higgs decay, normalized to the H -> t bar{t} width, can reach the 6% percent level. In the gluon fusion process the corresponding normalized asymmetry is smaller by an order of magnitude. We present a crude estimate of this observable at the LHC.
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In this paper, we explore the impact of extra radiation on predictions of $pp to tbar{t}X, X = h/W^{pm}/Z$ processes within the dimension-6 SMEFT framework. While full next-to-leading order calculations are of course preferred, they are not always practical, and so it is useful to be able to capture the impacts of extra radiation using leading-order matrix elements matched to the parton shower. While a matched leading-order calculation for $tbar{t}X$ is not expected to reproduce the next-to-leading order inclusive cross section precisely, we show that it does capture the relative impact of the EFT effects by considering the ratio of matched SMEFT inclusive cross sections to Standard Model values, $sigma_{rm SMEFT}(tbar{t}Xj)/sigma_{rm SM}(tbar{t}Xj) equiv mu$. Furthermore, we compare leading order calculations with and without extra radiation and find several cases, such as the effect of the operator $(varphi^{dagger}i!overleftrightarrow{D}_{!mu}varphi) (bar{t}gamma^mu t)$ on $tbar{t}h$ and $tbar{t}W$, for which the relative cross section prediction increases by more than $10%$ -- significantly larger than the uncertainty derived by varying the input scales in the calculation, including the additional scales required for matching. Being leading order at heart, matching has the benefit that it can be applied to all operators and processes relevant to $pp to tbar{t}X, X = h/W^{pm}/Z +$ jet, is computationally fast and not susceptible to negative weights. Therefore, it is a useful approach in $tbar{t}X+$ jet studies where complete next-to-leading order results are currently unavailable or unwieldy.
We discuss lepton charge asymmetries in $t bar t$ and $t bar t gamma$ production at the LHC, which can be measured in the semileptonic decay channel $t bar t to W^+ b , W^- bar b to ell^+ u b , q bar q bar b$ (or the charge conjugate). Considering several variants of a new physics scenario with a light colour octet, it is seen that for $t bar t$ these asymmetries may have a sensitivity competitive with the dilepton asymmetry already measured. For $t bar t gamma$ the new leptonic asymmetries, as well as the $t bar t$ charge asymmetry, will reach their full potential with the high luminosity LHC upgrade. These asymmetries can pinpoint deviations at the $3sigma-4sigma$ level for new physics scenarios where the charge asymmetries already measured in $t bar t$ production agree within $1sigma$.
Appreciable CP Asymmetries (~ 10%) can arise in the reaction e+ e- -> t bar-t Z already at TREE-LEVEL in models with two Higgs doublets. For a neutral Higgs particle, h, with a mass in the range 50 GeV < m_h < 400 GeV, it may be possible to detect a 2-3 sigma CP-odd effect in e+ e- -> t bar-t Z in ~ 1-2 years of running of a future high energy e+e- collider with c.m. energies of ~ 1-2 TeV and an integrated luminosity of 200-500 inverse fb.
We derive the geodesic equation for determining the Ryu-Takayanagi surface in $AdS_3$ deformed by single trace $mu T bar T + varepsilon_+ J bar T + varepsilon_- T bar J$ deformation for generic values of $(mu, varepsilon_+, varepsilon_-)$ for which the background is free of singularities. For generic values of $varepsilon_pm$, Lorentz invariance is broken, and the Ryu-Takayanagi surface embeds non-trivially in time as well as spatial coordinates. We solve the geodesic equation and characterize the UV and IR behavior of the entanglement entropy and the Casini-Huerta $c$-function. We comment on various features of these observables in the $(mu, varepsilon_+, varepsilon_-)$ parameter space. We discuss the matching at leading order in small $(mu, varepsilon_+, varepsilon_-)$ expansion of the entanglement entropy between the single trace deformed holographic system and a class of double trace deformed theories where a strictly field theoretic analysis is possible. We also comment on expectation value of a large rectangular Wilson loop-like observable.
We compute the Hagedorn temperature of $mu T bar T + varepsilon_+ J bar T + varepsilon_-T bar J$ deformed CFT using the universal kernel formula for the thermal partition function. We find a closed analytic expression for the free energy and the Hagedorn temperature as a function of $mu$, $varepsilon_+$, and $varepsilon_-$ for the case of a compact scalar boson by taking the large volume limit. We also compute the Hagedorn temperature for the single trace deformed $AdS_3 times S^1 times T^3 times S^3$ using holographic methods. We identify black hole configurations whose thermodynamics matches the functional dependence on $(mu, varepsilon_+, varepsilon_-)$ of the double trace deformed compact scalars.
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