4,908 research outputs found
New Particles Working Group Report of the Snowmass 2013 Community Summer Study
This report summarizes the work of the Energy Frontier New Physics working
group of the 2013 Community Summer Study (Snowmass)
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
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
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
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
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.Comment: 14 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
Light Gluino Search for Decays Containing pi+pi- or pi0 from a Neutral Hadron Beam at Fermilab
We report on two null searches, one for the spontaneous appearance of
pairs, another for a single , consistent with the decay of
a long-lived neutral particle into hadrons and an unseen neutral particle. For
the lowest level gluon-gluino bound state, known as the , we exclude the
decays and for
the masses of and in the theoretically allowed range. In
the most interesting mass range, , we exclude
lifetimes from seconds to as high as seconds,
assuming perturbative QCD production for the .Comment: 15 pages, 7 figure
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