We observe a signal for the doubly charmed baryon Ξcc+ in the decay mode Ξcc+→pD+K− to complement the previous reported decay Ξcc+→Λc+K−π+ in data from SELEX, the charm hadroproduction experiment at ...Fermilab. In this new decay mode we observe an excess of 5.62 events over a combinatoric background estimated by event mixing to be 1.38±0.13 events. The mixed background has Gaussian statistics, giving a signal significance of 4.8σ. The Poisson probability that a background fluctuation can produce the apparent signal is less than 6.4×10−4. The observed mass of this state is 3518±3 MeV/c2, consistent with the published result. Averaging the two results gives a mass of 3518.7±1.7 MeV/c2. The observation of this new weak decay mode confirms the previous SELEX suggestion that this state is a double charm baryon. The relative branching ratio for these two modes is 0.36±0.21.
The KTeV E799 experiment has conducted a search for the rare decays, K(L)→π(0)π(0)μ(+)μ(-) and K(L)→π(0)π(0)X(0)→π(0)π(0)μ(+)μ(-), where the X(0) is a possible new neutral boson that was reported by ...the HyperCP experiment with a mass of (214.3 ± 0.5) MeV/c(2). We find no evidence for either decay. We obtain upper limits of Br(K(L)→π(0)π(0)X(0)→π(0)π(0)μ(+)μ(-)) < 1.0 × 10(-10) and Br(K(L)→π(0)π(0)μ(+)μ(-)) < 9.2 × 10(-11) at the 90% confidence level. This result rules out the pseudoscalar X(0) as an explanation of the HyperCP result under the scenario that the dsX(0) coupling is completely real.
The xi0 muon semileptonic decay has been observed for the first time with nine identified events using the KTeV beam line and detector at Fermilab. The decay is normalized to the xi0 beta decay mode ...and yields a value for the ratio of decay rates gamma(xi0 --> sigma+ mu- nu(mu))/gamma(xi0 --> sigma+ e- nu(e)) of 1.8(-0.5)(+0.7)(stat) +/- 0.2(syst) x 10(-2). This is in agreement with the SU(3) flavor symmetric quark model.
The $\Xi^0$ muon semileptonic decay has been observed for the first time with nine identified events using the KTeV beam line and detector at Fermilab. The decay is normalized to the $\Xi^0$ beta ...decay mode and yields a value for the ratio of decay rates $\Gamma(\Xi^0 \to \Sigma^+\mu^- \overline{nu}_{\mu})/\Gamma(\Xi^0 \to \Sigma^+e^- \overline{\nu}_e) of 1.8_{-0.5}^{+0.7}(stat)\pm0.2(syst)×10^{-2}$. This is in agreement with the SU(3) flavor symmetric quark model.
We report the first observation of a charm-strange meson D(+)(sJ)(2632) at a mass of 2632.5+/-1.7 MeV/c(2) in data from SELEX, the charm hadro-production experiment E781 at Fermilab. This state is ...seen in two decay modes, D(+)(s)eta and D0K+. In the D(+)(s)eta decay mode we observe a peak with 101 events over a combinatoric background of 54.9 events at a mass of 2635.4+/-3.3 MeV/c(2). There is a corresponding peak of 21 events over a background of 6.9 at 2631.5+/-2.0 MeV/c(2) in the decay mode D0K+. The decay width of this state is <17 MeV/c(2) at 90% confidence level. The relative branching ratio Gamma(D0K+)/Gamma(D(+)(s)eta) is 0.14+/-0.06. The mechanism that keeps this state narrow is unclear. Its decay pattern is also unusual, being dominated by the D(+)(s)eta decay mode.
Coherent π+π−π− production in the interactions of a beam of 600GeVπ− mesons with C, Cu and Pb nuclei has been studied with the SELEX facility (Experiment E781 at Fermilab). The a2(1320) meson signal ...has been detected in the Coulomb (low q2) region. The Primakoff formalism used to extract radiative decay width of this meson yields Γ=284±25±25keV, which is the most precise measurement to date.
PDF
