6,613 research outputs found
Avian embryonic development in hyperdynamic environments
Embryos which developed for 24 hours in the oviduct of hens maintained at 2 G and which were subsequently incubated at Earth gravity had a 14% reduction in hatchability. Increased mortality during the first 4 days, and an increase in embryonic abnormalities were of the types usually found during the first mortality peak (2-3 days). Embryos in eggs that were produced at Earth gravity and continued their development on the centrifuge at fields of 2 G or less did not appear to be greatly affected by the treatment. At 4 G, 91% of the embryos died, mostly on the first and second days of incubation. Abnormalities prominent in the centrifuged eggs include: (a) a failure of the primitive streak to develop; (b) interference with the development of the axial skeleton; (c) multiple hemorrhages, mostly petechial which is consistent with capillary fragility; and (d) retardation of embryo growth, possibly caused by an interference with gaseous diffusion, the result of an acceleration-induced increase in gas density in the centrifuging incubator
Two Photon Radiation in W and Z Boson Production at the Tevatron Collider
We present a calculation of two photon radiation in W and Z boson production
in hadronic collisions, based on the complete matrix elements for the processes
q\bar q'\to\ell^\pm\nu\gamma\gamma and q\bar q\to\ell^+\ell^-\gamma\gamma,
including finite charged lepton masses. In order to achieve stable numerical
results over the full phase space, multiconfiguration Monte Carlo techniques
are used to map the peaks in the differential cross section. Numerical results
are presented for the Fermilab Tevatron.Comment: Revtex, 28 pages, 3 figure
and couplings in collision with polarized beams
The potential of e mode of linear collider to probe
and vertices is investigated through the Z boson
production from the procees . Considering the longitudinal and
transverse polarization states of the Z boson and incoming polarized beams we
find the 95% C.L. limits on the form factors , ,
and with integrated luminosity 500
and 0.5, 1, 1.5 TeV energies. It is shown that the polarization can
improve sensitivities by factors 2-3 depending on the energy.Comment: 12 pages, 8 EPS figure
Higher-order QED corrections to W-boson mass determination at hadron colliders
The impact of higher-order final-state photonic corrections on the precise
determination of the W-boson mass at the Tevatron and LHC colliders is
evaluated. In the presence of realistic selection criteria, the shift in the W
mass from a fit to the transverse mass distribution is found to be about 10 MeV
in the channel and almost negligible in the
channel. The calculation, which is implemented in a Monte Carlo event generator
for data analysis, can contribute to reduce the uncertainty associated to the W
mass measurement at future hadron collider experiments.Comment: 9 pages, 2 figures, 1 table, RevTe
Vector Boson Pair Production in Hadronic Collisions at Order : Lepton Correlations and Anomalous Couplings
We present cross sections for production of electroweak vector boson pairs,
, and , in and collisions, at next-to-leading
order in . We treat the leptonic decays of the bosons in the
narrow-width approximation, but retain all spin information via decay angle
correlations. We also include the effects of and anomalous
couplings.Comment: 23 pages, 8 figures, 3 table
Effects of the R-parity violation in the minimal supersymmetric standard model on dilepton pair production at the CERN LHC
We investigate in detail the effects of the R-parity lepton number violation
in the minimal supersymmetric standard model (MSSM) on the parent process at the CERN Large Hadron Collider (LHC). The numerical
comparisons between the contributions of the R-parity violating effects to the
parent process via the Drell-Yan subprocess and the gluon-gluon fusion are
made. We find that the R-violating effects on pair production at the
LHC could be significant. The results show that the cross section of the pair productions via gluon-gluon collision at the LHC can be of the order
of fb, and this subprocess maybe competitive with the production
mechanism via the Drell-Yan subprocess. We give also quantitatively the
analysis of the effects from both the mass of sneutrino and coupling strength
of the R-parity violating interactions.Comment: 18 pages, 10 figures, accepted by Phys. Rev.
Prospects for Searching for Excited Leptons during RunII of the Fermilab Tevatron
This letter presents a study of prospects of searching for excited leptons
during RunII of the Fermilab Tevatron. We concentrate on single and pair
production of excited electrons in the photonic decay channel in one CDF/DO
detector equivalent for 2 fb^{-1}. By the end of RunIIa, the limits should be
easily extended beyond those set by LEP and HERA for excited leptons with mass
above about 190 GeV.Comment: 4 pages, 8 figure
Probing the equation of state in the AGS energy range with 3-d hydrodynamics
The effect of (i) the phase transition between a quark gluon plasma (QGP) and
a hadron gas and (ii) the number of resonance degrees of freedom in the
hadronic phase on the single inclusive distributions of 16 different types of
produced hadrons for Au+Au collisions at AGS energies is studied.
We have used an exact numerical solution of the relativistic hydrodynamical
equations without free parameters which, because of its 3-d character,
constitutes a considerable improvement over the classical Landau solution.
Using two different equations of state (eos) - one containing a phase
transition from QGP to the Hadronic Phase and two versions of a purely hadronic
eos - we find that the first one gives an overall better description of the
Au+Au experimental data at energies.
We reproduce and analyse measured meson and proton spectra and also make
predictions for anti-protons, deltas, anti-deltas and hyperons. The low m_t
enhancement in pi- spectra is explained by baryon number conservation and
strangeness equilibration.
We also find that negative kaon data are more sensitive to the eos, as well
as the K-/pi- ratio. All hyperons and deltas are sensitive to the presence of a
phase transition in the forward rapidity region. Anti-protons, Omegas and heavy
anti-baryons are sensitive in the whole rapidity range.Comment: 25 pages (.tex) and 9 figures (.ps
Electroweak-correction effects in gauge-boson pair production at the LHC
We have studied the effect of one-loop logarithmic electroweak radiative
corrections on WZ and production processes at the LHC. We present
analytical results for the leading-logarithmic electroweak corrections to the
corresponding partonic processes du -> WZ, Wgamma. Using the leading-pole
approximation we implement these corrections into Monte Carlo programs for
. We find that electroweak corrections
lower the predictions by 5-20% in the physically interesting region of large
transverse momentum and small rapidity separation of the gauge bosons.Comment: 28 pages, LaTex, 13 eps figures included; references added and
corrected typo
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