NO(HSO4), a Fairly Ionic Solid

The colourless solid NO(HSO₄), known as “lead‐chamber crystals”, was investigated ever since its first preparation more than two centuries ago. Its overall ionic nature now is confirmed by X‐ray crystallography [Pna2₁, a = 7.3558(4), b = 6.8924(3), c = 7.7017(3) Å, Z = 4]. The next neighbours of the NO⁺ cations are four hydrogensulfate oxygen atoms, forming a distorted square at a distance of about 2.5 Å from the nitrogen atom. The square pattern next to the nitrogen atom is the most widespread coordination figure about an NO⁺ ion in a nitrosyl salt. Depending on the anion, the interaction goes along with a decrease of the N–O stretch's excitation energy.     

Measurement of the branching ratio and form factor of K(L)-->mu(+)mu(-)gamma

We report on the analysis of the rare decay K(L)-->mu(+)mu(-)gamma the 1997 data from the KTeV experiment at Fermilab. A total of 9327 candidate events are observed with 2.4% background, representing a factor of 40 increase in statistics over the current world sample. We find that B(K(L)-->mu(+)mu(-)gamma) = (3.62 +/- 0.04(stat) +/- 0.08(syst)) x 10(-7). The form factor parameter alpha(K*) is measured to be alpha(K*) = -0.160(+0.026)(-0.028). In addition, we make the first measurement of the parameter alpha from the D'Ambrosio-Isidori-Portolés form factor, finding alpha = -1.54 +/- 0.10. In that model, this alpha measurement limits the Cabibbo-Kobayashi-Maskawa parameter rho>-0.2.     

Observation of CP violation in K(L)-->pi(+)pi(-)e(+)e(-) decays

We report the first observation of a manifestly CP violating effect in the K(L)-->pi(+)pi(-)e(+)e(-) decay mode. A large asymmetry was observed in the distribution of these decays in the CP-odd and T-odd angle straight phi between the decay planes of the e(+)e(-) and pi(+)pi(-) pairs in the K(L) center of mass system. After acceptance corrections, the overall asymmetry is found to be [13.6+/-2. 5(stat)+/-1.2(syst)]%. This is the largest CP-violating effect yet observed when integrating over the entire phase space of a mode and the first such effect observed in an angular variable.     

Search for the weak decay of a lightly bound H0 dibaryon

We present results of a search for a new form of hadronic matter, a six-quark, dibaryon state called the H0, a state predicted to exist in several theoretical models. Analyzing data collected by experiment E799-II at Fermilab, we searched for the decay H0-->Lambdappi(-) and found no candidate events. We place an upper limit on [B(H0-->Lambdappi(-))dsigma(H)/dOmega]/(dsigma(Xi)/dOmega) and, in the context of published models, exclude the region of lightly bound mass states just below the LambdaLambda mass threshold, 2.194相似文献   

Measurement of the branching ratio and asymmetry of the decay Xi degrees -->Sigma degrees gamma

We have studied the rare weak radiative hyperon decay Xi degrees -->Sigma degrees gamma in the KTeV experiment at Fermilab. We have identified 4045 signal events over a background of 804 events. The dominant Xi degrees -->Lambdapi degrees decay, which was used for normalization, is the only important background source. An analysis of the acceptance of both modes yields a branching ratio of B(Xi degrees -->Sigma degrees gamma)/B(Xi degrees -->Lambdapi degrees ) = (3.34+/-0.05+/-0.09)x10(-3). By analyzing the final state decay distributions, we have also determined that the Sigma degrees emission asymmetry parameter for this decay is alpha(XiSigma) = -0.63+/-0.09.