We present a new determination of the parity of the neutral pion via the double Dalitz decay pi0-->e+e-e+e-. Our sample, which consists of 30,511 candidate decays, was collected from KL-->pi0pi0pi0 ...decays in flight at the KTeV-E799 experiment at Fermi National Accelerator Laboratory. We confirm the negative pi0 parity and place a limit on scalar contributions to the pi0-->e+e-e+e- decay amplitude of less than 3.3% assuming CPT conservation. The pi0gamma*gamma* form factor is well described by a momentum-dependent model with a slope parameter fit to the final state phase-space distribution. Additionally, we have measured the branching ratio of this mode to be B(pi0-->e+e-e+e-)=(3.26+/-0.18)x10(-5).
We present the Transition Radiation Detectors (TRD), coupled with the electron trigger, which were designed and built for selecting rare decays of neutral kaons in the KTeV experiment at Fermilab. ...The TRD is a powerful detector for identification of electrons in off-line analysis. A pion-electron rejection factor of 300:1 can be achieved with the KTeV TRD system. The electron trigger also uses signals from the TRD to discriminate electrons on-line. A system of programmable LeCroy 2366 modules runs a pattern recognition algorithm on TRD output with applied pulse height thresholds. A decision on the number of electrons which passed through TRDs is made in less than 500 nanoseconds. A desirable trigger rate suppression or signal efficiency can be achieved by choosing initialization constants for particular experimental conditions. During the experimental run the TRD trigger provided a required trigger rate suppression factor of 1.7-6 with signal efficiency of 97%-85%. In this summary paper we describe briefly the TRD, the main trigger components, and ifs functions. The performance of the TRD and the electron trigger in the KTeV experiment is also summarized.
Measurements of the decay KL-->e+ e- gamma Abouzaid, E; Arenton, M; Barker, A R ...
Physical review letters,
2007-Aug-03, 20070803, Letnik:
99, Številka:
5
Journal Article
Recenzirano
The E799-II (KTeV) experiment at Fermilab has collected 83 262 K(L)-->e+ e- gamma(gamma) events above a background of 79 events. We measure a decay width, normalized to the K(L)-->pi0pi0pi(D)0 ...(pi0-->gammagamma, pi0-->gammagamma, pi(D0-->e+ e- gamma(gamma)) decay width, of Gamma(K(L)-->e+e-gamma(gamma))/Gamma(K(L)-->pi0pi0pi(D)0)=(1.3302+/-0.0046(stat)+/-0.0102(syst)) x 10(-3). We also measure parameters of two K(L)gamma*gamma form factor models. In the Bergström-Massó-Singer parametrization, we find Calpha(K*)= -0.517 +/- 0.030(stat) +/- 0.022(syst). We separately fit for the first parameter of the D'Ambrosio-Isidori-Portolés model and find alpha(DIP)= -1.729 +/- 0.043(stat) +/- 0.028(syst).
We present a measurement of B(π0→e+e-γ)/B(π0→γγ), the Dalitz branching ratio, using data taken in 1999 by the E832 KTeV experiment at Fermi National Accelerator Laboratory. We use neutral pions from ...fully reconstructed KL decays in flight; the measurement is based on ~60 thousand KL→π0π0π0→γγγγe+e-γ decays. We normalize to KL→π0π0π0→6γ decays. We find B(π0→e+e-γ)/B(π0→γγ) (me+e->15 MeV/c2)=3.920±0.016(stat)±0.036(syst)×10-3. Using the Mikaelian and Smith prediction for the e+e- mass spectrum, we correct the result to the full e+e- mass range. The corrected result is B(π0→e+e-γ)/B(π0→γγ)=1.1559±0.0047(stat)±0.0106(syst)%. This result is consistent with previous measurements, and the uncertainty is a factor of 3 smaller than any previous measurement.
We present a measurement of B(π0→e+e−γ)/B(π0→γγ), the Dalitz branching ratio, using data taken in 1999 by the E832 KTeV experiment at Fermi National Accelerator Laboratory. We use neutral pions from ...fully reconstructed KL decays in flight; the measurement is based on ∼60 thousand KL→π0π0π0→γγγγe+e−γ decays. We normalize to KL→π0π0π0→6γ decays. We find B(π0→e+e−γ)/B(π0→γγ) (me+e−>15 MeV/c2)=3.920±0.016(stat)±0.036(syst)×10−3. Using the Mikaelian and Smith prediction for the e+e− mass spectrum, we correct the result to the full e+e− mass range. The corrected result is B(π0→e+e−γ)/B(π0→γγ)=1.1559±0.0047(stat)±0.0106(syst)%. This result is consistent with previous measurements, and the uncertainty is a factor of 3 smaller than any previous measurement.
The Fermilab KTeV experiment has searched for lepton-flavor-violating decays of the K(L) meson in three decay modes. We observe no events in the signal region for any of the modes studied, and we set ...the following upper limits for their branching ratios at the 90% C.L.: BR(K(L) --> pi(0) micro(+/-) e(-/+)) <7.6 x 10(-11); BR(K(L) --> pi(0)pi(0) micro(+/-) e(-/+)) <1.7 x 10(-10); BR(pi(0) --> micro(+/-) e(-/+)) <3.6 x 10(-10). This result represents a factor of 82 improvement in the branching ratio limit for K(L) --> pi(0) micro(+/-) e(-/+) and is the first reported limit for K(L) --> pi(0)pi(0) micro(+/-) e(-/+).
The KTeV E799 experiment has conducted a search for the rare decays KL→π0π0µ+µ- and KL→π0π0X0→ π0π0µ+µ-, where the X0 is a possible new neutral boson that was reported by the HyperCP experiment with ...a mass of (214.3 ± 0.5) MeV/c2. We find no evidence for either decay. We obtain upper limits of Br(KL→π0π0X0 →π0π0µ+µ-) < 1.0 x 10-10 and Br(KL→ π0π0µ+µ-) < 9.2 x 10-11 at the 90% confidence level. This result rules out the pseudoscalar X0 as an explanation of the HyperCP result under the scenario that the d¯sX0 coupling is completely real.
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