5,685 research outputs found
Responses of young cucumber plants to a diurnal temperature drop at different times of day and night
In greenhouse production of a number of vegetable and ornamental plant species, a short diurnal temperature drop in the end of the night or in the morning is commonly used to reduce stem elongation as an alternative to chemical growth retardants. Experiments were carried out to quantify the effects of a temperature drop at different times of the day and night on growth and photosynthetic activity of young cucumber plants. During 6 days plants were exposed daily to a temperature of 10 °C for 2 h at the beginning, in the middle and at the end of the night and day periods. The results have shown that plant response to drop may be qualitatively different in the light and darkness. While strongest effects of drop are observed when it is given in the daytime, for practical application in greenhouses it is more appropriate to reduce temperature at night. However, it may not be strictly necessary for cucumber seedlings to apply drop at the end of the night as it was stated in the literature. Thus, our results may cast doubt on the following statements: (a) temperature drops are not effective when delivered at other times of the day or night (except before sunrise), (b) optimal time for drop effects depends on the daily dynamics of stem and petiole elongation rate. It is rather drop itself is capable of modifying the dynamics of plant growth in the daily cycle.</p
Observation of Radiative Leptonic Decay of the Tau Lepton
Using 4.68 fb^{-1} of e^+e^- annihilation data collected with the CLEO II
detector at the Cornell Electron Storage Ring (CESR) we have studied tau
radiative decays tau -> mu nu nu gamma and tau -> e nu nu gamma. For a 10 MeV
minimum photon energy in the tau rest frame, the branching fraction of
radiative tau decay to a muon or electron is measured to be
(3.61+-0.16+-0.35)*10^{-3} or (1.75+-0.06+-0.17)*10^{-2}, respectively. The
branching fractions are in agreement with the Standard Model theoretical
predictions.Comment: 11 pages postscript, also available through
http://w4.lns.cornell.edu/public/CLN
Hadronic Structure in the Decay
We report on a study of the invariant mass spectrum of the hadronic system in
the decay tau- -> pi- pi0 nu_tau. This study was performed with data obtained
with the CLEO II detector operating at the CESR e+ e- collider. We present fits
to phenomenological models in which resonance parameters associated with the
rho(770) and rho(1450) mesons are determined. The pi- pi0 spectral function
inferred from the invariant mass spectrum is compared with data on e+ e- -> pi+
pi- as a test of the Conserved Vector Current theorem. We also discuss the
implications of our data with regard to estimates of the hadronic contribution
to the muon anomalous magnetic moment.Comment: 39 pages postscript, also available through
http://w4.lns.cornell.edu/public/CLN
Resonant Structure of and Decays
The resonant structure of the four pion final state in the decay is analyzed using 4.27 million pairs
collected by the CLEO II experiment. We search for second class currents in the
decay using spin-parity analysis and establish an
upper limit on the non-vector current contribution. The mass and width of the
resonance are extracted from a fit to the
spectral function. A partial wave analysis of the resonant structure of the
decay is performed; the spectral decomposition of
the four pion system is dominated by the and final
states.Comment: 34 pages postscript, also available through
http://w4.lns.cornell.edu/public/CLN
A Measurement of the Decay Asymmetry Parameters in \Xi_{c}^{0}\to \X^{-}\pi^{+}
Using the CLEO II detector at the Cornell Electron Storage Ring we have
measured the decay asymmetry parameter in the decay . We find , using the world average value of
we obtain . The physically allowed range of a decay
asymmetry parameter is . Our result prefers a negative value:
is at the 90% CL. The central value occupies the
middle of the theoretically expected range but is not yet precise enough to
choose between models.Comment: 10 pages postscript, also available through
http://w4.lns.cornell.edu/public/CLN
Search for Baryon and Lepton Number Violating Decays of the Lepton
We have searched for five decay modes of the tau lepton that simultaneously
violate lepton and baryon number: tau -> anti-proton gamma, tau -> anti-proton
pi0, tau -> anti-proton eta, tau -> anti-proton 2pi0, and tau -> anti-proton
pi0eta. The data used in the search were collected with the CLEO II detector at
the Cornell Electron Storage Ring (CESR). The integrated luminosity of the data
sample is 4.7 fb^{-1}, corresponding to the production of 4.3 x 10^6 tau+tau-
events. No evidence is found for any of the decays, resulting in much improved
upper limits on the branching fractions for the two-body decays and first upper
limits for the three-body decays.Comment: 8 pages, postscript file also available through
http://w4.lns.cornell.edu/public/CLN
Rare Decays of the
We have searched for the rare decays of the eta prime meson to e+ e- eta, e+
e- pizero, e+ e- gamma, and e mu in hadronic events at the CLEO II detector.
The search is conducted on 4.80 fb^-1 of e+ e- collisions at the Cornell
Electron Storage Ring. We find no signal in any of these modes, and set 90%
confidence level upper limits on their branching fractions of 2.4 X 10^-3, 1.4
X 10^-3, 0.9 X 10^-3, and 4.7 X 10^-4, respectively. We also investigate the
Dalitz plot of the common decay of the eta prime to pi+ pi- eta. We fit the
matrix element with the Particle Data Group parameterization and find Re(alpha)
= -0.021 +- 0.025, where alpha is a linear function of the kinetic energy of
the eta.Comment: 12 pages postscript, also available through
http://w4.lns.cornell.edu/public/CLN
First Observation of
We report on a study of exclusive radiative decays of the Upsilon(1S)
resonance collected with the CLEO-II detector operating at CESR. We present the
first observation of the radiative decays Upsilon(1S)->gamma pi+pi- and
Upsilon(1S)->gamma pi0pi0. For the dipion mass regime m(pipi)>1.0 GeV, we
obtain Br(Upsilon(1S)->gamma pi+pi-=(6.3+/-1.2+/-1.3) x 10^(-5), and
Br(Upsilon(1S)->gamma pi0pi0=(1.7+/-0.6+/-0.3) x 10^(-5). The observed gamma
pipi events are consistent with the hypothesis Upsilon(1S)->gamma f2(1270).Comment: 9 pages, postscript file also available through
http://w4.lns.cornell.edu/public/CLN
Further Search for the Two-Photon Production of the Glueball Candidate
The CLEOII detector at the Cornell e+ e- storage ring CESR has been used to
search for the two-photon production of the decaying into pi+ pi-.
No evidence for a signal is found in data corresponding to an integrated
luminosity of 4.77/fb and a 95% CL upper limit on of 2.5 eV is set. If this result is combined with the BES Collaboration's
measurement of in radiative decay, a 95% CL
lower limit on the stickiness of the of 73 is obtained. If the
recent CLEO result for \Gamma_{two-photon} * BR{\K_S K_S} is combined with
the present result, the stickiness of the is found to be larger
than 102 at the 95% CL. These results for the stickiness (the ratio of the
probabilities for two-gluon coupling and two-photon coupling) provide further
support for a substantial neutral parton content in the .Comment: 8 pages, postscript file also available through
http://w4.lns.cornell.edu/public/CLN
Limit on Tau Neutrino Mass from
From a data sample of 29058
decays observed in the CLEO detector we derive a 95% confidence upper limit on
the tau neutrino mass of 28 MeV.Comment: 17 pages postscript, also available through
http://w4.lns.cornell.edu/public/CLN
- …