879 research outputs found
Functional phases and angular momentum characteristics of Tkatchev and Kovacs
No full textUnderstanding the technical requirements and underlying biomechanics of complex release and re-grasp skills on high bar allows coaches and scientists to develop safe and effective training programmes. The aim of this study was to examine the differences in the functional phases between the Tkatchev and Kovacs skills and to explain how the angular momentum demands are addressed. Images of 18 gymnasts performing 10 Tkatchevs and 8 Kovacs at the Olympic Games were recorded (50 Hz), digitised and reconstructed (3D Direct Linear Transformation). Orientation of the functional phase action, defined by the rapid flexion to extension of the shoulders and extension to flexion of the hips as the performer passed through the lower vertical, along with shoulder and hip angular kinematics, angular momentum and key release parameters (body angle, mass centre velocity and angular momentum about the mass centre and bar) were compared between skills. Expected differences in the release parameters of angle, angular momentum and velocity were observed and the specific mechanical requirement of each skill were highlighted. Whilst there were no differences in joint kinematics, hip and shoulder functional phase were significantly earlier in the circle for the Tkatchev. These findings highlight the importance of the orientation of the functional phase in the preceding giant swing and provide coaches with further understanding of the critical timing in this key phase
Quelques questions de la théorie de la croissance et de la condensation des bulles dans les chambres à bulles
No full textMeasurement of the branching ratio and form factors for the decay K-L ->pi(+/-)pi(0)e(-/+)nu(e)((nu)over-bar(e))
No full textThe decay was investigated with the NA48 detector at CERN SPS using a beam of long-lived neutral kaons. The branching ratio was fixed from a sample of 5464 events with 62 background events. The form factors and were found to be in agreement with previous measurements but with higher accuracy. The coupling parameter of the chiral Lagrangian was evaluated from the data.The K L →π ± π 0 e ∓ ν e ( ν ̄ e ) decay was investigated with the NA48 detector at CERN SPS using a beam of long-lived neutral kaons. The branching ratio Br (K L →π ± π 0 e ∓ ν e ( ν ̄ e ))=(5.21±0.07 stat ±0.09 syst )×10 −5 was fixed from a sample of 5464 events with 62 background events. The form factors f ̄ s , f ̄ p , λ g and h̄ were found to be in agreement with previous measurements but with higher accuracy. The coupling parameter of the chiral Lagrangian L 3 =(−4.1±0.2)×10 −3 was evaluated from the data.The decay was investigated with the NA48 detector at CERN SPS using a beam of long-lived neutral kaons. The branching ratio was fixed from a sample of 5464 events with 62 background events. The form factors , , and were found to be in agreement with previous measurements but with higher accuracy. The coupling parameter of the chiral Lagrangian was evaluated from the data
Space charge in ionization detectors and the NA48 electromagnetic calorimeter
No full textThe subject of space charge due to positive ions slowly moving in parallel plate ionization chambers is considered. A model for the degradation of the detector response is developed, with particular emphasis on electromagnetic calorimeters. The topics discussed include: (a) the stationary; (b) the time dependent cases; (c) the limit of very large space charge, (d) the electric field dependence of the electron drift velocity; (e) the effect of longitudinal development of showers; (f) the behaviour of the average reductions of response; and (g) the non-uniformity of response for different positions of the shower axis inside the cell defined by the electrodes. The NA48 calorimeter is used as application and for comparison of results. (C) 1999 Elsevier Science B.V. All rights reserved
Measurement of the decay rate and form factor parameter alpha(K*) in the decay K-L -> e(+)e(-)gamma
No full textThe decay rate of the neutral K meson K-L --> e(+)e(-)gamma has been measured with the NA48 detector at the CERN SPS. A total of 6864 events has been observed with an estimated background of 10 events. The branching ratio is Gamma(K-L --> e(+)e(-)gamma)/Gamma(K-L --> all) = (1.06 +/- 0.02(stat) +/- 0.02(sys) +/- 0.04(calc)) X 10(-5). The parameter alpha(K*) describing the relative strength of the two contributing amplitudes to this decay through intermediate pseudoscalar or vector mesons was measured to be alpha(K*) = -0.36 +/- 0.06(stat) +/- 0.02(sys). (C) 1999 Published by Elsevier Science B.V. All rights reserved
Measurement of the decay rate and form factor parameter in the decay
No full textThe decay rate of the neutral K meson has been measured with the NA48 detector at the CERN SPS. A total of 6864 events has been observed with an estimated background of 10 events. The branching ratio is . The parameter describing the relative strength of the two contributing amplitudes to this decay through intermediate seudoscalar or vector mesons, was measured to be $\mathrm{\alpha_{K^{*}} = -0.36 \pm 0.06_{stat.} \pm 0.02_{sys.}}
First measurement of the rate K-L(0)->pi mu nu gamma RID C-6551-2009 RID A-4071-2012
No full textIn a preliminary version of the NA48 experiment at the CERN SPS, in which an iron-scintillator sandwich calorimeter was used as a photon detector, the ratio of K-L --> pi mu nu gamma and K-L --> pi mu nu decays was measured. The branching ratio BR(K-L --> pi mu nu gamma,E-gamma*greater than or equal to 30 MeV)/(K-L --> pi mu nu) is found to be (2.08+/-0.17(-0.21)(+0.16)x10(-3), where the first error is statistical and the second systematic. The result is in agreement with theoretical predictions. (C) 1998 Elsevier Science B.V
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