Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userSearch for the dark photon in $B^0 to A^{prime} A^{prime}$, $A^{prime} to e^+ e^-$, $mu^+ mu^-$, and $pi^+ pi^-$ decays at Belle
74
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We present a search for the dark photon $A^{prime}$ in the $B^0 to A^{prime} A^{prime}$ decays, where $A^{prime}$ subsequently decays to $e^+ e^-$, $mu^+ mu^-$, and $pi^+ pi^-$. The search is performed by analyzing $772 times 10^6$ $Boverline{B}$ events collected by the Belle detector at the KEKB $e^+ e^-$ energy-asymmetric collider at the $Upsilon (4S)$ resonance. No signal is found in the dark photon mass range $0.01~mathrm{GeV}/c^2 le m_{A^{prime}} le 2.62~mathrm{GeV}/c^2$, and we set upper limits of the branching fraction of $B^0 to A^{prime} A^{prime}$ at the 90% confidence level. The products of branching fractions, $mathcal{B}(B^0 to A^{prime} A^{prime}) times mathcal{B}(A^{prime} to e^+ e^-)^2$ and $mathcal{B}(B^0 to A^{prime} A^{prime}) times mathcal{B}(A^{prime} to mu^+ mu^-)^2$, have limits of the order of $10^{-8}$ depending on the $A^{prime}$ mass. Furthermore, considering $A^{prime}$ decay rate to each pair of charged particles, the upper limits of $mathcal{B}(B^0 to A^{prime} A^{prime})$ are of the order of $10^{-8}$-$10^{-5}$. From the upper limits of $mathcal{B}(B^0 to A^{prime} A^{prime})$, we obtain the Higgs portal coupling for each assumed dark photon and dark Higgs mass. The Higgs portal couplings are of the order of $10^{-2}$-$10^{-1}$ at $m_{h} simeq m_{B^0} pm 40~mathrm{MeV}/c^2$ and $10^{-1}$-$1$ at $m_{h} simeq m_{B^0} pm 3~mathrm{GeV}/c^2$.
rate research
Read More
We have measured several branching ratios for $psi^prime$ decay using the data collected by FNAL E835 experiment during year 2000, obtaining ${cal B}(psi^prime to e^+ e^-) = 0.0068pm0.0001pm0.0004$, ${cal B}(psi^prime to J/psi pi^+ pi^-) = 0.292pm0.005pm0.018$, ${cal B}(psi^prime to J/psi pi^0 pi^0) = 0.167pm0.005pm0.014$ and ${cal B}(psi^prime to J/psi eta) = 0.028pm0.002pm0.002$. We also present a measurement of the dipion mass distribution in the decays $psi^prime to J/psi pi pi$.
Theories beyond the standard model often predict the existence of an additional neutral boson, the $Z^{prime}$. Using data collected by the Belle II experiment during 2018 at the SuperKEKB collider, we perform the first searches for the invisible decay of a $Z^{prime}$ in the process $e^+ e^- to mu^+ mu^- Z^{prime}$ and of a lepton-flavor-violating $Z^{prime}$ in $e^+ e^- to e^{pm} mu^{mp} Z^{prime}$. We do not find any excess of events and set 90% credibility level upper limits on the cross sections of these processes. We translate the former, in the framework of an $L_{mu}-L_{tau}$ theory, into upper limits on the $Z^{prime}$ coupling constant at the level of $5 times 10^{-2}$ -- $1$ $M_{Z^prime}leq 6$ GeV/$c^2$.
The presently world largest data sample of pi0 --> gamma e+e- decays containing nearly 5E5 events was collected using the WASA detector at COSY. A search for a dark photon U produced in the pi0 --> gamma U --> gamma e+e- decay from the pp-->pppi^0 reaction was carried out. An upper limit on the square of the U-gamma mixing strength parameter epsilon^2 of 5e-6 at 90% CL was obtained for the mass range 20 MeV <M_U< 100 MeV. This result together with other recent experimental limits significantly reduces the M_U vs. epsilon^2 parameter space preferred by the measured value of the muon anomalous magnetic moment.
New results are reported from a measurement of $pi^0$ electroproduction near threshold using the $p(e,e^{prime} p)pi^0$ reaction. The experiment was designed to determine precisely the energy dependence of $s-$ and $p-$wave electromagnetic multipoles as a stringent test of the predictions of Chiral Perturbation Theory (ChPT). The data were taken with an electron beam energy of 1192 MeV using a two-spectrometer setup in Hall A at Jefferson Lab. For the first time, complete coverage of the $phi^*_{pi}$ and $theta^*_{pi}$ angles in the $p pi^0$ center-of-mass was obtained for invariant energies above threshold from 0.5 MeV up to 15 MeV. The 4-momentum transfer $Q^2$ coverage ranges from 0.05 to 0.155 (GeV/c)$^2$ in fine steps. A simple phenomenological analysis of our data shows strong disagreement with $p-$wave predictions from ChPT for $Q^2>0.07$ (GeV/c)$^2$, while the $s-$wave predictions are in reasonable agreement.
Based on a sample of $1.31 times 10^9$ $J/psi$ events collected with the BESIII detector, an amplitude analysis of the isospin-violating decays $eta^prime rightarrow pi^+pi^-pi^0$ and $eta^prime rightarrow pi^0pi^0pi^0$ is performed. A significant $P$-wave contribution from $eta^prime rightarrow rho^{pm} pi^{mp}$ is observed for the first time in $eta^prime rightarrow pi^+pi^-pi^0$. The branching fraction is determined to be ${mathcal B}(eta^prime rightarrow rho^{pm}pi^{mp})=(7.44pm0.60pm1.26pm1.84)times 10^{-4}$, where the first uncertainty is statistical, the second systematic, and the third model dependent. In addition to the nonresonant $S$-wave component, there is a significant $sigma$ meson component. The branching fractions of the combined $S$-wave components are determined to be ${mathcal B}(eta^prime rightarrow pi^+pi^-pi^0)_S=(37.63pm0.77pm2.22pm4.48)times 10^{-4}$ and ${mathcal B}(eta^prime rightarrow pi^0pi^0pi^0)=(35.22pm0.82pm2.54)times 10^{-4}$, respectively. The latter one is consistent with previous BESIII measurements.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
