Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userLimits on top FCNC decay t$rightarrow$cH and t$rightarrow$c$gamma$ from CLIC at 380 GeV
45
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
FCNC top decays are very strongly suppressed in the Standard Model and the observation of any such decay would be a direct signature of physics beyond SM. Many new physics scenarios predict contributions to FCNC processes and the largest enhancement in many models is for t$rightarrow$cH decay. Enhancements for the decay channel t$rightarrow$c$gamma$ are more modest, but the decay still has a clearly identifiable kinematic signature. Prospects for measuring these decays at CLIC running at 380 GeV were studied with full detector simulation, taking the luminosity distribution, beam polarization and beam induced background into account. Top pair production events with t$rightarrow$cH decays can be identified based on the kinematic constraints and flavour tagging information. The analysis was divided into three steps: classification of top pair candidate events, event quality determination and kinematic reconstruction based on signal or background hypotheses, and final separation of signal from background. To obtain optimal results, selection criteria based on the dedicated Boosted Decision Trees (BDT) were used at each step. The expected limit on BR(t$rightarrow$cH)$times$BR(H$rightarrow bbar{b}$) from a combined analysis of hadronic and semi-leptonic top pair samples, as well as the limit on BR(t$rightarrow$c$gamma$) from hadronic top pair decays are presented.
rate research
Read More
u007fA search for radiative decays of the $P$-wave spin singlet charmonium resonance $h_c$ is performed based on $4.48 times 10^{8}$ $psi$ events collected with the BESIII detector operating at the BEPCII storage ring. Events of the reaction channels $h_{c} rightarrow gamma eta$ and $gamma eta$ are observed with a statistical significance of $8.4 sigma$ and $4.0 sigma$, respectively, for the first time. The branching fractions of $h_{c} rightarrow gamma eta$ and $h_{c} rightarrow gamma eta$ are measured to be $mathcal{B}(h_{c} rightarrow gamma eta)=(1.52 pm 0.27 pm 0.29)times10^{-3}$ and $mathcal{B}(h_{c} rightarrow gamma eta)=(4.7 pm 1.5 pm 1.4)times10^{-4}$, respectively, where the first errors are statistical and the second are systematic uncertainties.
We present a measurement of the ratio of the top-quark branching fractions $R=mathcal{B}(trightarrow Wb)/mathcal{B}(trightarrow $ $q$ represents quarks of flavors $b$, $s$, or $d$, in the final state, in events with two charged leptons, missing transverse energy and at least two jets. The measurement uses $sqrt{s}$ = 1.96 TeV proton--antiproton collision data corresponding to an integrated luminosity of 8.7 fb$^{-1}$ and collected with the Collider Detector at Fermilab during Run II of the Tevatron. We measure $R=0.87 pm 0.07$ (stat+syst), and extract the magnitude of the Cabibbo-Kobayashi-Maskawa matrix element, $left|V_{tb}right| = 0.93 pm 0.04$ (stat+syst) assuming three generations of quarks. Under these assumptions, a lower limit of $|V_{tb}|>0.85$ at 95% credibility level is set.
A search for the rare radiative leptonic decay $D_s^+togamma e^+ u_e$ is performed for the first time using electron-positron collision data corresponding to an integrated luminosity of 3.19 fb$^{-1}$, collected with the BESIII detector at a center-of-mass energy of 4.178 GeV. No evidence for the $D_s^+togamma e^+ u_e$ decay is seen and an upper limit of $mathcal B(D_s^+togamma e^+ u_e)<1.3times 10^{-4}$ is set on the partial branching fraction at a 90% confidence level for radiative photon energies $E_{gamma}^*>0.01$~GeV.
The ratios of the branching fractions of the decays $Lambda_{c}^{+} rightarrow p pi^{-} pi^{+}$, $Lambda_{c}^{+} rightarrow p K^{-} K^{+}$, and $Lambda_{c}^{+} rightarrow p pi^{-} K^{+}$ with respect to the Cabibbo-favoured $Lambda_{c}^{+} rightarrow p K^{-} pi^{+}$ decay are measured using proton-proton collision data collected with the LHCb experiment at a 7 TeV centre-of-mass energy and corresponding to an integrated luminosity of 1.0 fb$^{-1}$: begin{align*} frac{mathcal{B}(Lambda_{c}^{+} rightarrow p pi^{-} pi^{+})}{mathcal{B}(Lambda_{c}^{+} rightarrow p K^{-} pi^{+})} & = (7.44 pm 0.08 pm 0.18),%, frac{mathcal{B}(Lambda_{c}^{+} rightarrow p K^{-} K^{+})}{mathcal{B}(Lambda_{c}^{+} rightarrow p K^{-} pi^{+})} &= (1.70 pm 0.03 pm 0.03),%, frac{mathcal{B}(Lambda_{c}^{+} rightarrow p pi^{-} K^{+})}{mathcal{B}(Lambda_{c}^{+} rightarrow p K^{-} pi^{+})} & = (0.165 pm 0.015 pm 0.005 ),%, end{align*} where the uncertainties are statistical and systematic, respectively. These results are the most precise measurements of these quantities to date. When multiplied by the world-average value for $mathcal{B}(Lambda_{c}^{+} rightarrow p K^{-} pi^{+})$, the corresponding branching fractions are begin{align*} mathcal{B}(Lambda_{c}^{+} rightarrow p pi^{-} pi^{+}) &= (4.72 pm 0.05 pm 0.11 pm 0.25) times 10^{-3}, mathcal{B}(Lambda_{c}^{+} rightarrow p K^{-} K^{+}) &= (1.08 pm 0.02 pm 0.02 pm 0.06) times 10^{-3}, mathcal{B}(Lambda_{c}^{+} rightarrow p pi^{-} K^{+}) &= (1.04 pm 0.09 pm 0.03 pm 0.05) times 10^{-4}, end{align*} where the final uncertainty is due to $mathcal{B}(Lambda_{c}^{+} rightarrow p K^{-} pi^{+})$.
We present the full $mathcal{O}(alpha)$ electroweak radiative corrections to the process $e^+e^- rightarrow t bar{t} gamma$ at the International Linear Collider (ILC). The computation is performed with the help of the GRACE-Loop system. We present the total cross-section and the top quark forward-backward asymmetry ($A_{FB}$) as a function of the center-of-mass energy and compare them with the process $e^+e^- rightarrow t bar{t}$. We find that the value of $A_{FB}$ in $t bar{t} gamma$ production is larger than $A_{FB}$ in $tbar{t}$ production. It is an important result for the measurement of the top quark forward-backward asymmetry at the ILC. Applying a structure function method, we also subtract the QED correction to gain the genuine weak correction in both the $alpha$ scheme and the $G_{mu}$ scheme ($delta_{W}^{G_{mu}}$). We obtain numerical values for $delta_{W}^{G_{mu}}$ which are changing from 2% to -24% when we vary the center-of-mass energy from 360 GeV to 1 TeV.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
