4,170 research outputs found
Detecting Gluino-Containing Hadrons
When SUSY breaking produces only dimension-2 operators, gluino and photino
masses are of order 1 GeV or less. The gluon-gluino bound state has mass
1.3-2.2 GeV and lifetime > 10^{-5} - 10^{-10} s. This range of mass and
lifetime is largely unconstrained because missing energy and beam dump
techniques are ineffective. With only small modifications, upcoming K^0 decay
experiments can study most of the interesting range. The lightest
gluino-containing baryon (uds-gluino) is long-lived or stable; experiments to
find it and the uud-gluino are also discussed.Comment: 13 pp, 1 figure (uuencoded). Descendant of hep-ph/9504295,
hep-ph/9508291, and hep-ph/9508292, focused on experimental search
techniques. To be published in Phys Rev Let
Radiative Decay of Vector Quarkonium: Constraints on Glueballs and Light Gluinos
Given a resonance of known mass, width, and J^{PC}, we can determine its
gluonic branching fraction, b(R->gg), from data on its production in radiative
vector quarkonium decay, V -> gamma+R. For most resonances b(R->gg) is found to
be O(10%), consistent with being q-qbar states, but we find that both
pseudoscalars observed in the 1440 MeV region have b(R->gg) ~ 1/2 - 1, and
b(f_0^{++}->gg) ~ 1/2. As data improves, b(R->gg) should be a useful
discriminator between q-qbar and gluonic states and may permit quantitative
determination of the extent to which a particular resonance is a mixture of
glueball and q-qbar. We also examine the regime of validity of pQCD for
predicting the rate of V -> gamma+eta_gluino, the ``extra'' pseudoscalar bound
state which would exist if there were light gluinos. From the CUSB limit on
peaks in Upsilon -> gamma X, the mass range 3 GeV < m(eta_gluino) < 7 GeV can
be excluded. An experiment must be significantly more sensitive to exclude an
eta_gluino lighter than this.Comment: 36pp (inc figs),RU-94-04. (Replaces original which didn't latex
correctly and didn't have figures.
3-D Imaging Applied To Foot Structures In Walking
Pedagogic and coaching experiments have demonstrated that learning and training difficulties encountered by physical education students, athletes and coaches are frequently related to poor or inadequate 3-D visual representation of human body structures and movement. In order to counteract this important shortcoming, a low cost computer platform including an Amiga 3000T computer, preparation software (Imagine and DCTV) and presentation software, has been developed. The purpose of this study was to generate 3-D objects of the ankle-foot structures and to animate these objects in order to accurately illustrate plantar flexion, dorsiflexion, supination and pronation of the foot as a function of the walking cycle. Using anatomical and biomechanical informations available in literature, this 3-D imaging study has succeeded in producing an interactive software permitting individual as well as large group visualisation (with the use of a video projector) of tibia and fibula interactions with talus, as well as movements of tarsal and metatarsal bones during the different support phases in walking. Positions and roles of ligaments have also been illustrated. Subsequent laboratory experiments have demonstrated that intermediate-term retention of knowledge is favored in teaching when using this computer-assisted technique. Actually, in a test-retest situation, intermediate retention decreased by 10.87% when using traditional teaching; the decrease in retention was only a slight 0.450 /0 when using this 3-D imaging program as a visualisation aid. Sports training and coaching have also benefitted from the use of this tool
Comment on "Correlation between Compact Radio Lout Quasars and Ultrahigh Energy Cosmic Rays"
In a recent paper, Farrar and Biermann argue that there is a strong
correlation between the direction of the five highest-energy cosmic-ray events
and compact, radio-loud quasars. This Comment shows that this analysis contains
several inconsistencies and errors so that the significance of any such
correlation is certainly greatly overestimated and perhaps nonexistent.Comment: 2 pages, REVTE
Correlation between Compact Radio Quasars and Ultra-High Energy Cosmic Rays
Some proposals to account for the highest energy cosmic rays predict that
they should point to their sources. We study the five highest energy events
(E>10^20 eV) and find they are all aligned with compact, radio-loud quasars.
The probability that these alignments are coincidental is 0.005, given the
accuracy of the position measurements and the rarity of such sources. The
source quasars have redshifts between 0.3 and 2.2. If the correlation pointed
out here is confirmed by further data, the primary must be a new hadron or one
produced by a novel mechanism.Comment: 8 pages, 3 tables, revtex. with some versions of latex it's necessary
to break out the tables and latex them separately using article.sty rather
than revtex.st
Clustering in Highest Energy Cosmic Rays: Physics or Statistics?
Directional clustering can be expected in cosmic ray observations due to
purely statistical fluctuations for sources distributed randomly in the sky. We
develop an analytic approach to estimate the probability of random cluster
configurations, and use these results to study the strong potential of the
HiRes, Auger, Telescope Array and EUSO/OWL/AirWatch facilities for deciding
whether any observed clustering is most likely due to non-random sources.Comment: 19 pages, LaTeX, 3 figure
Experiments to Find or Exclude a Long-Lived, Light Gluino
Gluinos in the mass range ~1 1/2 - 3 1/2 GeV are absolutely excluded. Lighter
gluinos are allowed, except for certain ranges of lifetime. Only small parts of
the mass-lifetime parameter space are excluded for larger masses unless the
lifetime is shorter than ~ 2 10^{-11} (m_{gluino}/ GeV) sec. Refined mass and
lifetime estimates for R-hadrons are given, present direct and indirect
experimental constraints are reviewed, and experiments to find or definitively
exclude these possibilities are suggested.Comment: 27 pp, latex with 1 uufiled figure, RU-94-35. New version amplifies
discussion of some points and corresponds to version for Phys. Rev.
Wide-angle elastic scattering and color randomization
Baryon-baryon elastic scattering is considered in the independent scattering
(Landshoff) mechanism. It is suggested that for scattering at moderate
energies, direct and interchange quark channels contribute with equal color
coefficients because the quark color is randomized by soft gluon exchange
during the hadronization stage. With this assumption, it is shown that the
ratio of cross sections at CM angle
decreases from a high energy value of R_{\pbar p / pp} \approx 1/2.7, down to
R_{\pbar p / pp} \approx 1/28, compatible with experimental data at moderate
energies. This sizable fall in the ratio seems to be characteristic of the
Landshoff mechanism, in which changes at the quark level have a strong effect
precisely because the hadronic process occurs via multiple quark scatterings.
The effect of color randomization on the angular distribution of proton-proton
elastic scattering and the cross section ratio is also discussed.Comment: 18 pages, latex2e, 4 uuencoded figures, include
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