Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userFlavor changing Z couplings at the LHC
165
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
Models with a non-universal Z exhibit in general flavor changing neutral currents (FCNC) at tree-level. When the Z couplings favor the third generation, flavor changing transitions of the form Ztc and Ztu could be large enough to be observable at the LHC. In this paper we explore this possibility using the associated production of a single top-quark with the Z and find that integrated luminosities of a few hundred fb$^{-1}$ are necessary to probe the interesting region of parameter space.
rate research
Read More
We propose to study the flavor properties of the top quark at the future Circular Electron Positron Collider (CEPC) in China. We systematically consider the full set of 56 real parameters that characterize the flavor-changing neutral interactions of the top quark, which can be tested at CEPC in the single top production channel. Compared with the current bounds from the LEP2 data and the projected limits at the high-luminosity LHC, we find that CEPC could improve the limits of the four-fermion flavor-changing coefficients by one to two orders of magnitude, and would also provide similar sensitivity for the two-fermion flavor-changing coefficients. Overall, CEPC could explore a large fraction of currently allowed parameter space that will not be covered by the LHC upgrade. We show that the $c$-jet tagging capacity at CEPC could further improve its sensitivity to top-charm flavor-changing couplings. If a signal is observed, the kinematic distribution as well as the $c$-jet tagging could be exploited to pinpoint the various flavor-changing couplings, providing valuable information about the flavor properties of the top quark.
A general two Higgs doublet model (2HDM) is adopted to study the signature of flavor changing neutral Higgs (FCNH) decay $phi^0 to tbar{c}+bar{t}c$, where $phi^0$ could be a CP-even scalar ($H^0$) or a CP-odd pseudoscalar ($A^0$). Measurement of the light 125 GeV neutral Higgs boson ($h^0$) couplings at the Large Hadron Collider (LHC) favor the decoupling limit or the alignment limit of a 2HDM, in which gauge boson and diagonal fermion couplings of $h^0$ approach Standard Model values. In such limit, FCNH couplings of $h^0$ are naturally suppressed by a small mixing parameter $cos(beta-alpha)$, while the off-diagonal couplings of heavier neutral scalars $phi^0$ are sustained by $sin(beta-alpha) sim 1$. We study physics background from dominant processes with realistic acceptance cuts and tagging efficiencies. Promising results are found for the LHC running at 13 or 14 TeV collision energies.
We investigate the prospects for discovering a top quark decaying into one light Higgs boson along with a charm quark in top quark pair production at the CERN Large Hadron Collider (LHC). A general two Higgs doublet model is adopted to study the signature of flavor changing neutral Higgs decay $t to cphi^0$, %or $bar{t} to bar{c}phi^0$ where $phi^0$ could be CP-even ($H^0$) or CP-odd ($A^0$). The dominant physics background is evaluated with realistic acceptance cuts as well as tagging and mistagging efficiencies. For a reasonably large top-charm-Higgs coupling ($lambda_{tc}/lambda_{t} agt 0.09$), the abundance of signal events and the %that our acceptance cuts reduction in physics background allow us to establish a $5sigma$ signal for $M_phi sim 125$ GeV at the LHC with a center of mass energy ($sqrt{s}$) of 8 TeV and an integrated luminosity of 20 fb$^{-1}$. The discovery potential will be greatly enhanced with the full energy of $sqrt{s} = 14$ TeV.
We study the constraints on $tto u$ flavor changing neutral Higgs (FCNH) coupling, and how it may be explored further at the Large Hadron Collider (LHC). In the general two Higgs doublet model, such transitions can be induced by a nonzero $rho_{tu}$ Yukawa coupling. We show that such couplings can be constrained by existing searches at the LHC for $m_H$, $m_A$ and, $m_{H^+}$ in the sub-TeV range, where $H$, $A$ and $H^+$ are the exotic $CP$-even, $CP$-odd and charged scalars. We find that a dedicated $ugto t H/tA to t t bar u$ search can probe the available parameter space of $rho_{tu}$ down to a few percent level for $200,mbox{GeV} lesssim m_H,,m_A lesssim 600$ GeV, with discovery possible at high luminosity. Effects of how other extra top Yukawa couplings, such as $rho_{tc}$ and $rho_{tt}$, dilute the sensitivity of the $rho_{tu}$ probe are discussed.
We investigate the prospects of discovering the top quark decay into a charm quark and a Higgs boson ($t to c h^0$) in top quark pair production at the CERN Large Hadron Collider (LHC). A general two Higgs doublet model is adopted to study flavor changing neutral Higgs (FCNH) interactions. We perform a parton level analysis as well as Monte Carlo simulations using textsc{Pythia}~8 and textsc{Delphes} to study the flavor changing top quark decay $t to c h^0$, followed by the Higgs decaying into $tau^+ tau^-$, with the other top quark decaying to a bottom quark ($b$) and two light jets ($tto bWto bjj$). To reduce the physics background to the Higgs signal, only the leptonic decays of tau leptons are used, $tau^+tau^- to e^pmmu^mp +slashed{E}_T$, where $slashed{E}_T$ represents the missing transverse energy from the neutrinos. In order to reconstruct the Higgs boson and top quark masses as well as to effectively remove the physics background, the collinear approximation for the highly boosted tau decays is employed. Our analysis suggests that a high energy LHC at $sqrt{s} = 27$ TeV will be able to discover this FCNH signal with an integrated luminosity $mathcal{L} = 3$ ab$^{-1}$ for a branching fraction ${cal B}(t to ch^0) agt 1.4 times 10^{-4}$ that corresponds to a FCNH coupling $|lambda_{tch}| agt 0.023$. This FCNH coupling is significantly below the current ATLAS combined upper limit of $|lambda_{tch}| = 0.064$.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
