4,246 research outputs found
Measurement of the photon structure function at ALEPH
The photon structure function F2gamma has been measured with data taken by
the ALEPH collaboration at LEP centre-of-mass energies sqrt s = 91 GeV with <
Q^2 > of 9.9, 20.7 and 284 GeV^2 and sqrt s = 183 GeV with of 13.7 and
56.5 GeV^2. For the data at sqrt s = 183 GeV a two-dimensional unfolding method
employing the principle of maximum entropy is used, which reduces the errors
compared to one-dimensional methods.Comment: 5 pages, 5 figures, To be published in proceedings "PHOTON99
Single and pair production of heavy leptons in model
We investigate the single and pair production of new heavy leptons via string
inspired model at future linear colliders. Signal and corresponding
backgrounds for these leptons are studied. We have found that single production
of heavy leptons is more relevant than that of pair production, as expected.
For a maximal mixing value of 0.1, the upper mass limits of 2750 GeV in the
single case and 1250 GeV in the pair production case are obtained at
TeV collider option.Comment: 14 pages, 10 figure
Simulations of Time-Resolved X-Ray Diffraction in Laue Geometry
A method of computer simulation of Time-Resolved X-ray Diffraction (TRXD) in
asymmetric Laue (transmission) geometry with an arbitrary propagating strain
perpendicular to the crystal surface is presented. We present two case studies
for possible strain generation by short-pulse laser irradiation: (i) a
thermoelastic-like analytic model; (ii) a numerical model including effects of
electron-hole diffusion, Auger recombination, deformation potential and thermal
diffusion. A comparison with recent experimental results is also presented.Comment: 9 pages, 11 figure
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
Intermittency and Exotic Channels
It is pointed out that accurate measurements of short-range two-particle
correlations in like-charge and in channels should be
very helpful in determining the origin of the \lq\lq intermittency\rq\rq\
phenomenon observed recently for the like-charge pion pairs.Comment: 5 p., plain tex, preprint T94/078(Saclay), LPTHE 94/58(Orsay
Method for Flavor Tagging in Neutral B Meson Decays
A method is proposed for tagging the flavor of neutral mesons in the
study of CP-violating decay asymmetries. The method makes use of a possible
difference in interactions in or systems with isospins 1/2
and 3/2, and would be particularly clean if the systems can be
detected as ``'' resonances.Comment: Submitted to Phys. Rev. D. 11 pages, LaTeX, Technion-PH-92-40 / PITHA
92/39 / EFI 92-5
Lepton flavor conserving Z -> l^+ l^-$ decays in the general two Higgs doublet model
We calculate the new physics effects to the branching ratios of the lepton
flavor conserving decays Z -> l^+ l^- in the framework of the general two Higgs
Doublet model. We predict the upper limits for the couplings
|\bar{\xi}^{D}_{N,\mu\tau}| and |\bar{\xi}^{D}_{N,\tau\tau}| as 3\times 10^2
GeV and 1\times 10^2 GeV, respectively.Comment: 9 pages, 3 figure
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
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
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