197 research outputs found
Search for Light Gluinos via the Spontaneous Appearance of pi+pi- Pairs with an 800 GeV/c Proton Beam at Fermilab
We searched for the appearance of pi+pi- pairs with invariant mass greater
than 648 MeV in a neutral beam. Such an observation could signify the decay of
a long-lived light neutral particle. We find no evidence for this decay. Our
null result severely constrains the existence of an R0 hadron, which is the
lightest bound state of a gluon and a light gluino, and thereby also the
possibility of a light gluino. Depending on the photino mass, we exclude the R0
in the mass and lifetime ranges of 1.2 -- 4.6 GeV and 2E-10 -- 7E-4 seconds,
respectively. (To Appear in Phys. Rev. Lett.)Comment: Documentstyle aps,epsfig,prl (revtex), 6 pages, 7 figure
Search for the Decay K_L -> pi^0 nu nubar using pi^0 -> e^+ e^- gamma
We report on a search for the decay K_L -> pi^0 nu nubar, carried out as a
part of E799-II, a rare K_L decay experiment at Fermilab. Within the Standard
Model, the K_L -> pi^0 nu nubar decay is dominated by direct CP violating
processes, and thus an observation of the decay implies confirmation of direct
CP violation. Due to theoretically clean calculations, a measurement of B(K_L
-> pi^0 nu nubar) is one of the best ways to determine the CKM parameter eta.
No events were observed, and we set an upper limit B(K_L -> pi^0 nu nubar) <
5.9 times 10^-7 at the 90% confidence level.Comment: 5 pages, 4 figure
Search for the Decay
We report on a search for the decay \klpimumu carried out as a part of the
KTeV experiment at Fermilab. This decay is expected to have a significant
violating contribution and a direct measurement will either support the CKM
mechanism for CP violation or point to new physics. Two events were observed in
the 1997 data with an expected background of events, and we set
an upper limit \BR{\klpimumu} at the 90% confidence
level.Comment: See also "Observation of the Decay ", also by the KTeV collaboratio
A Measurement of the KL Charge Asymmetry
We present a measurement of the charge asymmetry in the mode based on 298 million analyzed decays. We measure a
value of , 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 violation in the neutral kaon system.Comment: Submitted to Physical Review Letters, Dec 31, 2001. 4 pages, 4
figure
Observation of the Decay
We have observed the decay at the KTeV
experiment at Fermilab. This decay presents a formidable background to the
search for new physics in . The 1997 data yielded a
sample of 4 signal events, with an expected background of 0.155 0.081
events. The branching ratio is )
with
, consistent with a QED calculation
which predicts .Comment: See also the paper "Search for the Decay ", also by the KTeV collaboratio
Search for the Decay Kl -> pi0 e+ e-
We report on a search for the decay Kl -> pi0 e+ e- carried out by the
KTeV/E799 experiment at Fermilab. This decay is expected to have a significant
CP violating contribution and the measurement of its branching ratio could
support the CKM mechanism for CP violation or could point to new physics. Two
events were observed in the 1997 data with an expected background of 1.06
+-0.41 events, and we set an upper limit Br(Kl -> pi0 e+ e-) < 5.1 x 10^-10 at
the 90% confidence level.Comment: 13 pages, 2 figure
Measurement of the Decay KL -> Pi0 Gamma Gamma
We report on a new measurement of the decay KL -> pi0 gamma gamma by the KTeV
experiment at Fermilab. We determine the KL -> pi0 gamma gamma branching ratio
to be (1.68 +/- 0.07 +/- 0.08)x10**-6. Our data shows the first evidence for a
low-mass gamma gamma signal as predicted by recent O(p**6) chiral perturbation
calculations that include vector meson exchange contributions. From our data,
we extract a value for the effective vector coupling aV = -0.72 +/- 0.05 +/-
0.06.Comment: 5 pages, 4 figure
A Measurement of the Branching Ratio of
We report on a study of the decay 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 events. An
effective form factor was determined from the observed distribution of the
invariant mass. Using this form factor in the calculation of the
detector acceptance, the branching ratio was measured to be .Comment: 5 pages, 4 figure
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 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 integrating over
the entire phase space of a mode and the first such effect observed in an
angular variable.Comment: 4 pages 4 figures submitted to pr
A New Measurement of the Radiative Ke3 Branching Ratio and Photon Spectrum
We present a preliminary report on a new measurement of the radiative neutral
Ke3 branching ratio and the first study of the photon spectrum in this decay.
We find BR(Ke3g, E*_g>30 GeV, Th*_eg>20 deg)/BR(Ke3) =
0.911+-0.009(stat)+0.021-0.010(syst)%. Our measurement of the spectrum is
consistent with inner bremsstrahlung only as the source of photons at the 2
sigma level.Comment: 5 pages, 4 figures, proceedings paper from Meson 2000, Cracow,
Poland, May 200
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