3,610 research outputs found
Measurements of the QCD Colour Factors at LEP
A summary of the measurements of the QCD colour factors at LEP is presented.
Such measurements provide a test of the gauge group structure underlying the
theory of strong interactions. A variety of methods have been applied by the
various experiments, and perfect consistency with the expectation of QCD with
SU(3) as gauge group is found.Comment: 9 pages, Latex, Talk presented at the 5th Topical Seminar on The
Irresistible Rise of the Standard Model, San Miniato, Italy, April 199
The Bose-Einstein distribution functions and the multiparticle production at high energies
The evolution properties of propagating particles produced at high energies
in a randomly distributed environment are studied. The finite size of the phase
space of the multiparticle production region as well as the chaoticity can be
derived.Comment: 18 pages, LaTeX, no figures, no table
High Energy Gamma--Radiation from the Galactic Center due to Neutralino Annihilation
We study the NGS (Non--dissipative Gravitational Singularity) model, which
successfully describes the non--linear stage of evolution of perturbations (see
[1], [2] and references therein). This model predicts DM density distribution
with which holds from very small
distances up to very large distances . Assuming the neutralino to be a CDM particle, we
calculate the annihilation of neutralinos in the vicinity of the singularity
(Galactic Center). If neutralinos are the dominant component of DM in our
Galaxy, the produced energy is enough to provide the whole observed activity of
the GC. Neutralinos of the most general composition and of mass in the range
20~{\rm GeV} \leq m_\c \leq 1~{\rm TeV} are considered. We find the
neutralino compositions which give the relic density needed for the Mixed Dark
Matter (MDM) model and we evaluate for these compositions the high--energy
() gamma--ray flux under the constraint that the
radio flux is lower than the observational limit. The compositions with the
detectable gamma--ray flux which we found are provided by a set of almost pure
gaugino states with the neutralino mass between and GeV. We
demonstrate that a detectable high--energy gamma--ray flux is produced by the
neutralino annihilation also in the case when neutralinos provide a small
fraction (down to ) of the DM in our Galaxy. The predicted flux is
for E_\gamma \gsim
300~{\rm MeV}Comment: Plain TeX 11 pages 4 figures available on request. Preprint numbers
LNGS 94/90 - DFTT 5/9
Time-Shift in the OPERA set-up: proof against superluminal neutrinos without the need of knowing the CERN-LNGS distance and Reminiscences on the origin of the Gran Sasso Lab, of the 3rd neutrino and of the "Teramo Anomaly"
The LVD time stability allows to establish a time-shift in the OPERA
experiment, thus providing the first proof against Superluminal neutrinos,
using the horizontal muons of the "Teramo Anomaly". This proof is particularly
interesting since does not need the knowledge of the distance between the place
where the neutrinos are produced (CERN) and the place where they are detected
(LNGS). Since the Superluminal neutrinos generated in the physics community a
vivid interest in good and bad behaviour in physics research, the author
thought it was appropriate to recall the origin of the Gran Sasso Lab, of the
3rd neutrino, of the horizontal muons due to the "Teramo Anomaly" and of the
oscillation between leptonic flavours, when the CERN-Gran Sasso neutrino beam
was included in the project for the most powerful underground Laboratory in the
world.Comment: 35 pages, 25 Figures, Invited paper at the Gran Sasso mini-Workshop
on LNGS results on the neutrino velocity topic, Gran Sasso, Italy, 28 March
201
Transverse Tau Polarization in Decays of the Top and Bottom Quarks in the Weinberg Model of CP Non-conservation
We show that the transverse polarization asymmetry of the -lepton in
the decay is extremely sensitive to CP violating
phases arising from the charged Higgs exchange in the Weinberg model of CP
non-conservation. Qualitatively, the polarization asymmetries are enhanced over
rate or energy asymmetries by a factor of . Thus for optimal values of the parameters the method requires top pairs to be observable rather than needed for rate or energy
asymmetries. We also examine polarization in b decays via and find that it can also be very effective in constraining the CP
violation parameters of the extended Higgs sector.Comment: 11,1 figure, SLAC-PUB-608
The QCD Coupling Constant
This paper presents a summary of the current status of determinations of the
strong coupling constant alpha_s. A detailed description of the definition,
scale dependence and inherent theoretical ambiguities is given. The various
physical processes that can be used to determine alpha_s are reviewed and
attention is given to the uncertainties, both theoretical and experimental.Comment: 56 page
Radiative Corrections to Neutralino and Chargino Masses in the Minimal Supersymmetric Model
We determine the neutralino and chargino masses in the MSSM at one-loop. We
perform a Feynman diagram calculation in the on-shell renormalization scheme,
including quark/squark and lepton/slepton loops. We find generically the
corrections are of order 6%. For a 20 GeV neutralino the corrections can be
larger than 20%. The corrections change the region of
parameter space which is ruled out by LEP data. We demonstrate that, e.g., for
a given and the lower limit on the parameter can shift
by 20 GeV.Comment: 11 pages, JHU-TIPAC-930030, PURD-TH-93-13, uses epsf.sty, 6 uuencoded
postscript figures, added one sentence and a referenc
Optimized Variables of the Study of Polarization
The value of the -baryon polarization can be extracted from inclusive data
at LEP with better than 10\% precision based on current statistics. We present
a new variable by which to measure the polarization, which is the ratio of the
average electron energy to the average neutrino energy. This variable is both
sensitive to polarization and insensitive to fragmentation uncertainties.Comment: 10 pages (LaTeX), 2 figures, MIT-CTP-2270, CERN-PPE/94-0
Multiplicity with a Thrust Cut
We evaluate the multiplicity of hadrons in the -annihilation at a
given thrust in the modified leading-log approximation, including
corrections. The calculation is done at a large value of
by the use of the factorisation which takes place in the
one-particle-inclusive cross section at a given . At a small , a
different type of factorisation takes place, which also enable us to evaluate
the multiplicity. Two approaches are compared numerically. Measuring this
quantity near , we can determine the multiplicity ratio between a
gluon-jet and a quark-jet.Comment: OCHA-PP-32, LATEX FILE, 21
Dominant Three-Body Decays of a Heavy Higgs and Top Quark
We calculate the dominant three body Higgs decays, and , in the Standard Model. We
find that the branching ratios of these decays are of the order of few percent
for large Higgs masses. We comment on the behaviour of the partial decay width
below the threshold.
Numerical results of the following three body top decays, and , are also given. We discuss the feasibility of
observing these Higgs and top decays at future high energy colliders.Comment: 19 pages (13 Figs can be sent by request), TeX, MZ-TH/92-2
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