arXiv subjects

The KTeV Collaboration

Publications and source records attributed to The KTeV Collaboration.

6 recordsLinked to original sources

arXiv2002

Measurements of the Decay KL->e+e-mu+mu-

The KTeV experiment at Fermilab has isolated a total of 132 events from the rare decay KL->e+e-mu+mu-, with an estimated background of 0.8 events. The branching ratio of this mode is determined to be 2.69 +/- 0.24 (stat) +/- 0.12 (syst) x 10^-9, with a radiative cutoff of M(eemm)^2/M(K)^2 > 0.95. The first measurement using this mode of the parameter alpha from the D'Ambrosio, Isidori, and Portoles model of the KLg*g* vertex yields a result of -1.59 +/- 0.37, consistent with values obtained from other decay modes. Because of the limited statistics, no sensitivity is found to the DIP parameter beta. The magnitude of the angular distribution asymmetry between the e+e- and mu+mu- planes, indicative of a CP-violating contribution to the decay, is found to be consistent with zero. We set a 90% C.L. upper limit of 4.12 x 10^(-11) on the branching ratio of the lepton flavor--violating mode KL->e+-e+-mu+-mu+-, a factor of three improvement over the current limit from the KTeV experiment.

hep-ex↗

arXiv2002

A Measurement of the KL Charge Asymmetry

We present a measurement of the charge asymmetry $δ_L$ in the mode $K_L \to π^{\pm}e^{\mp}ν$ based on 298 million analyzed decays. We measure a value of $δ_L = (3322 \pm 58(stat) \pm 47(sys))\cdot 10^{-6}$, in good agreement with previous measurements and 2.4 times more precise than the current best published result. The result is used to place more stringent limits on CPT and $ΔS = ΔQ$ violation in the neutral kaon system.

hep-ex↗

arXiv2001

Measurements of the rare decay K_{L} -> e^{+} e^{-} e^{+} e^{-}

We observe 441 K_{L} -> e^{+} e^{-} e^{+} e^{-} candidate events with a background of 4.2 events and measure B(K_{L} -> e^{+} e^{-} e^{+} e^{-}) = (3.72 \pm 0.18(stat) \pm 0.23(syst)) \times 10^{-8} in the KTeV/E799II experiment at Fermilab. Using the distribution of the angle between the planes of the e^{+} e^{-} pairs, we measure the CP parameters beta_{CP} = -0.23 \pm 0.09(stat) \pm 0.02(syst) and gamma_{CP} = -0.09 \pm 0.09(stat) \pm 0.02(syst). We also present the first detailed study of the e^{+} e^{-} invariant mass spectrum in this decay mode.

hep-ex↗

arXiv2000

First Observation of the decay KL -> pi0 e e gamma

We report on the first observation of the decay KL -> pi0 ee gamma by the KTeV E799 experiment at Fermilab. Based upon a sample of 48 events with an estimated background of 3.6 +/- 1.1 events, we measure the KL -> pi0 ee gamma branching ratio to be (2.34 +/- 0.35 +/- 0.13)x10^{-8}. Our data agree with recent O(p^6) calculations in chiral perturbation theory that include contributions from vector meson exchange through the parameter a_V. A fit was made to the KL -> pi0 ee gamma data for a_V with the result -0.67 +/- 0.21 +/- 0.12, which is consistent with previous results from KTeV.

hep-ex↗

arXiv2000

A Measurement of the Branching Ratio of $K_L \to e^+e^-γγ$

We report on a study of the decay $K_L \to e^+e^-γγ$ carried out as a part of the KTeV/E799 experiment at Fermilab. The 1997 data yielded a sample of 1543 events, including an expected background of $56 \pm 8$ events. An effective form factor was determined from the observed distribution of the $e^+e^-$ invariant mass. Using this form factor in the calculation of the detector acceptance, the branching ratio was measured to be ${\mathcal B}(K_L \to e^+ e^- γγ, E^*_γ> 5 {MeV}) = (5.84 \pm 0.15 {\rm ~(stat)} \pm 0.32 {\rm ~(sys)})\times 10^{-7}$.

hep-ex↗

arXiv1999

Search for the Weak Decay of a Lightly Bound H Dibaryon

We present results of a search for a neutral, six-quark, dibaryon state called the \h, a state predicted to exist in several theoretical models. Observation of such a state would signal the discovery of a new form of hadronic matter. Analyzing data collected by experiment E799-II, using the KTeV detector at Fermilab, we searched for the decay $H^0 \to Λp \piminus$ and found no candidate events. We exclude the region of lightly bound mass states just below the $ΛΛ$ mass threshold, $2.194~\gev < M_H < 2.231$~\gev, with lifetimes from $\sim$$ 5 \times 10^{-10}$~sec to $\sim$$1 \times 10^{-3}$~sec.

hep-ex↗