Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userSearch for a 33.9 MeV/c^2 Neutral Particle in Pion Decay
101
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
The E815 (NuTeV) neutrino experiment has performed a search for a 33.9 MeV/c^2 weakly-interacting neutral particle produced in pion decay. Such a particle may be responsible for an anomaly in the timing distribution of neutrino interactions in the KARMEN experiment. E815 has searched for this particles decays in an instrumented decay region; no evidence for this particle was found. The search is sensitive to pion branching ratios as low as 10^-13.
rate research
Read More
The reaction p(e,e^{prime}pi^+)X^0 was studied with two high resolution magnetic spectrometers to search for narrow baryon resonances. A missing mass resolution of 2.0 MeV was achieved. A search for structures in the mass region of 0.97 < M_{X^0} < 1.06 GeV yielded no significant signal. The yield ratio of p(e,e^{prime}pi^+)X^0/p(e,e^{prime}pi^+)n was determined to be (-0.35 +/- 0.35) times 10^{-3} at 1.004 GeV and (0.34 +/- 0.42) times 10^{-3} at 1.044 GeV.
We report on the observation of a K$_s$p resonance signal at a mass of 1765$pm$5 MeV/c$^2$, with intrinsic width $Gamma = 108pm 22$ MeV/c$^2$, produced inclusively in $Sigma^-$-nucleus interactions at 340 GeV/c in the hyperon beam experiment WA89 at CERN. The signal was observed in the kinematic region $x_F>0.7$, in this region its production cross section rises approximately linearly with $(1-x_F)$, reaching $BR(Xto K_S p)cdot dsigma /dx_F = (5.2pm 2.3) mu b $ per nucleon at $x_F=0.8$. The hard xf spectrum suggests the presence of a strong leading particle effect in the production and hence the identification as a $Sigma^{*+}$ state. No corresponding peaks were observed in the $K^- p$ and $Lambda pi^{pm}$ mass spectra.
We report the results of a search for the decay $K^+ to pi^+ u bar u$ in the kinematic region with $pi^+$ momentum $140 < P < 195$ MeV/c using the data collected by the E787 experiment at BNL. No events were observed. When combined with our previous search in this region, one candidate event with an expected background of $1.22 pm 0.24$ events results in a 90% C.L. upper limit of $2.2 times 10^{-9}$ on the branching ratio of $K^+ to pi^+ u bar u$. We also report improved limits on the rates of $K^+ to pi^+ X^0$ and $K^+ to pi^+ X^1 X^2$ where $X^0, X^1, X^2$ are hypothetical, massless, long-lived neutral particles.
We have searched for the decay $K^+ to pi^+ u bar u$ in the kinematic region with pion momentum below the $K^+ to pi^+ pi^0$ peak. One event was observed, consistent with the background estimate of $0.73pm 0.18$. This implies an upper limit on $B(K^+ to pi^+ u bar u)< 4.2times 10^{-9}$ (90% C.L.), consistent with the recently measured branching ratio of $(1.57^{+1.75}_{-0.82}) times 10^{-10}$, obtained using the standard model spectrum and the kinematic region above the $K^+ to pi^+ pi^0$ peak. The same data were used to search for $K^+ to pi^+ X^0$, where $X^0$ is a weakly interacting neutral particle or system of particles with $150 < M_{X^0} < 250 {rm ~MeV/c^2}$.
New data are presented on the p(e,ep)pi^0 reaction at threshold at a four-momentum transfer of Q^2=0.05 GeV^2/c^2. The data were taken with the three-spectrometer setup of the A1 Collaboration at the Mainz Microtron MAMI. The complete center of mass solid angle was covered up to a center of mass energy of 4 MeV above threshold. Combined with measurements at three different values of the virtual photon polarization epsilon, the structure functions sigma_T, sigma_L, sigma_{TT}, and sigma_{TL} are determined. The results are compared with calculations in Heavy Baryon Chiral Perturbation Theory and with a phenomenological model. The measured cross section is significantly smaller than both predictions.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
