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(-/+).
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).
Using the complete KTeV data set of 5,241 candidate K(L)--> pi(+) pi(-) e(+) e(-) decays (including an estimated background of 204 +/- 14 events), we have measured the coupling g(CR)= 0.163 +/- ...0.0149(stat) +/- 0.023(syst) of the CP conserving charge radius process and from it determined a K(0) charge radius of <r(2)(K(0))> = -0.077 +/- 0.007(stat) +/- 0.011(syst)fm(2). We have determined a first experimental upper limit of 0.04 (90% C.L.) /g(e1)/ / /g(M1)/ of the couplings for the E1 and M1 direct photon emission processes. We also report the measurement of /g(M1)/ including a vector form factor /g(M1)/(1 + (a(1)/a(2))/((M(2)(p)-(M(2)(k))= 2M(K)E(gamma*)), where vector /g(M1)/= 1.11+/- 0.12(stat) +/- 0.08(syst) and a(1)/a(2) = -0.744 +/- 0.027(stat) +/- 0.032(syst) GeV(2)/c(2). Finally, a CP-violating asymmetry of 13.6 +/- 1.4(stat) +/- 1.5(syst)% in the CP and T odd angle phi between the decay planes of the e(+) e(-) and pi(+) pi(-) pairs in the K(L) center of mass is reported.
Beam-based alignment of the NuMI target station components at FNAL Zwaska, R.; Bishai, M.; Childress, S. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2006, Letnik:
568, Številka:
2
Journal Article
Recenzirano
Odprti dostop
The Neutrinos at the Main Injector (NuMI) facility is a conventional horn-focused neutrino beam which produces muon neutrinos from a beam of mesons directed into a long evacuated decay volume. The ...relative alignment of the primary proton beam, target, and focusing horns affects the neutrino energy spectrum delivered to experiments. This paper describes a check of the alignment of these components using the proton beam.
Forward single π0 production by coherent neutral-current interactions, νA→νAπ0, is investigated using a 2.8×1020 protons-on-target exposure of the MINOS Near Detector. For single-shower topologies, ...the event distribution in production angle exhibits a clear excess above the estimated background at very forward angles for visible energy in the range 1–8 GeV. Cross sections are obtained for the detector medium comprised of 80% iron and 20% carbon nuclei with ⟨A⟩=48, the highest-⟨A⟩ target used to date in the study of this coherent reaction. The total cross section for coherent neutral-current single π0 production initiated by the νμ flux of the NuMI low-energy beam with mean (mode) Eν of 4.9 GeV (3.0 GeV), is 77.6±5.0(stat)−16.8+15.0(syst)×10−40 cm2 pernucleus. The results are in good agreement with predictions of the Berger-Sehgal model.
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.
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