3,817 research outputs found
Probing the CP nature of the Higgs bosons by top-pair production at photon linear colliders
We study effects of heavy Higgs bosons on the top-pair production process at
photon linear colliders. The interference patterns between the resonant
Higgs-production amplitudes and the continuum QED amplitudes are examined. The
patterns tell us not only the CP nature of the Higgs bosons but also the phase
of the --Higgs vertex which gives new information about the Higgs
couplings to new charged particles. We point out that it is necessary to use
circularly polarized photon beams to produce efficiently heavy Higgs bosons
whose masses exceed the electron beam energy, and show that the above
interference patterns of the production amplitudes can be studied by observing
top decay angular distributions. Analytic expressions for the helicity
amplitudes for the sequential process are presented in
terms of the generic production amplitudes.Comment: 34 pages, LATEX file with 6 PS figures, comments adde
Entropy for Quark States
We discuss the quantum state structure using the standard model for three
colored quarks in the fundamental representations of making up the
singlet ground state of the hadrons. This allows us to calculate a finite von
Neumann entropy from the quantum reduced density matrix, which we explicitly
evaluate for the quarks in a model for the meson and baryon states. Finally we
look into the general effects and implications of entanglement in the
color space.Comment: 9 pages, 0 figure
Exclusive J/\psi Productions at e^+ e^- Colliders
Exclusive quarkonium pair production in electron-positron collisions is
studied in non-relativistic QCD. The obtained cross section for J/\psi + \eta_c
production in the leading order is confronted against the recent measurements
by the Belle Collaboration at KEKB. It is shown that a large renormalization
K-factor is necessary to explain the experimental data. We point out that the
J^{PC}=0^{-+} nature of the hadronic systems that are assigned to be \eta_c
should be tested by the triple angular distributions in terms of the scattering
angle, and, polar and azimuthal angles of J/\psi into leptons. We further study
J/\psi + J/\psi and \Upsilon + \Upsilon productions at LEP energies. Although
the axial-vector couplings of the Z-boson to charm and bottom quarks allow
production of such pairs when one of them is polarised transversally and the
other longitudinally, we find that the integrated luminosity at Z pole
accumulated by LEP is not large enough to observe the exclusive pair production
of quarkonium.Comment: 11 pages, 2 eps figures, LaTe
Light bottom squark and gluino confront electroweak precision measurements
We address the compatibility of a light sbottom (mass 2\sim 5.5 \gev) and a
light gluino (mass 12\sim 16 \gev) with electroweak precision measurements.
Such light particles have been suggested to explain the observed excess in the
quark production cross section at the Tevatron. The electroweak observables
may be affected by the sbottom and gluino through the SUSY-QCD corrections to
the vertex. We examine, in addition to the SUSY-QCD corrections, the
electroweak corrections to the gauge boson propagators from the stop which are
allowed to be light from the SU(2) symmetry. We find that this scenario is
strongly disfavored from electroweak precision measurements unless the heavier
sbottom mass eigenstate is lighter than 180\gev and the left-right mixing in
the stop sector is sufficiently large. This implies that one of the stops
should be lighter than about 98\gev.Comment: 4 pages, revtex, 2 figures. Reference added, version to appear in
Phys.Rev.Let
Low-luminosity Extragalactic Water Masers toward M82, M51, and NGC4051
Sub-arcsecond observations using the Very Large Array (VLA) are presented for
low-luminosity water maser in M82, M51, and NGC4051. New maser features have
been detected within the M82 starburst complex. They are largely associated
with star-forming activity, such as optically identified starburst-driven
winds, H II regions, or the early phase of star formation in the galaxy. The
water maser in M51 consists of blueshifted and redshifted features relative to
thesystemic velocity of the galaxy. The redshifted features are measured to the
northwest of the nuclear radio source, while the location of the blueshifted
counterpart is displaced by about 2" from the radio source. A small velocity
gradient closely aligned with the radio jet is detected from the redshifted
features. The redshifted maser most likely amplifies the background radio
continuum jet, while the blueshifted counterpart marks off-nuclear star
formation in the galaxy. All of the detected maser features in the narrow-line
Seyfert 1 galaxy NGC 4051 remain unresolved by new VLA observations. Due to the
low luminosity of the maser, the maser excitation is not directly related to
the active galactic nucleus.Comment: 20 pages, 10 figures. Accepted for publication in AJ (17/Oct/2006
Gender Pay Gap: A Macro Perspective
This paper examines the factors influencing the gender wage gap by using an unbalanced cross-country aggregated panel data set for a sample covering 53 economies for the period 1995–2010. Using robust estimators proposed by Lewbel (2012) to correct for heterogeneity and endogeneity, results suggest that a higher female share in the industry sector tends to widen the gender wage gap regardless of a country’s development stage. While having more children widens the gender wage gap, as expected, the effect is only statistically significant for developing countries. In developed countries, more labor force participation by women seems to narrow the gender wage gap, probably due to the number of female labor market entrants taking up higher-paying service sector jobs. For developing countries, closing the gender gaps in labor force participation and education is not sufficient to achieve gender wage parity. Higher-paying jobs should be created by developing the service sector in these economies
Direct extraction of hadronic form factors from elastic-scattering data
Non-forward elastic hadron-scattering data are collected and analysed within
the Regge approach. Through an analysis of the data in small bins in , we
have directly extracted the pomeron trajectory and the hadronic form factors
(or reggeon couplings). We found higher values than usually used for the
intercept and for the slope of the soft pomeron trajectory. The presence of
zeros in for the effective hadronic form factors is emphasised.Comment: 4 pages, 5 figures, talk given at Diffraction 2004, Cala Gonone,
Sardinia, Italy, 18-23 September 200
Consequences of a Possible Di-Gamma Resonace at TRISTAN
If high mass di-gamma events observed at LEP are due to the production of a
di-gamma resonance via its leptonic coupling, its consequences can be observed
at TRISTAN. We find that a predicted decay branching rate is too small to
account for the observed events if the resonance spin is zero, due to a strong
cancellation in the decay amplitudes. Such a cancellation is absent if the
resonance has a spin two. We study the consequences of a tensor production in
the processes , and at TRISTAN
energies. Complete helicity amplitudes with tensor boson exchange contributions
are given, and the signal can clearly be identified from various distributions.
TRISTAN experiments are also sensitive to the virtual tensor boson exchange
effects, which reduce to the contact interaction terms in the high mass limit.Comment: 23 pages in revtex, 7 figures (not included) available upon request,
KEK-TH-35
What could be learnt from Positronium for Quarkonium?
In order to fulfill Low's theorem requirements, a new lowest order basis for
bound state decay computations is proposed, in which the binding energy is
treated non-perturbatively. The properties of the method are sketched by
reviewing standard positronium decay processes. Then, it is shown how applying
the method to quarkonia sheds new light on some longstanding puzzles.Comment: 12 pages, 10 figures. Talk given at the ETH Workshop on Positronium
Physics, May 30-31, 2003, Zurich, Switzerlan
Study of Single W production in e-gamma collisions through the decay lepton spectrum to probe gamma-WW couplings
We investigate the effect of anomalous gamma-W-W couplings in e-gamma --> nu
W through the angular and energy spectrum of the secondary leptons. Within the
narrow-width approximation, a semi-analytical study of the secondary lepton
energy-angle double distribution is considered. Utility of observables derived
from this is demonstrated by considering the anomalous coupling,
delta-kappa-gamma. Results of our investigation for typical ILC machine
considered at Ecm = 300-1000 GeV re-affirms potential of this collider as a
precision machine.Comment: Typos corrected, discussion added in section 2 for clarity, error in
fig.2 corrected, figures 7 and 8 replaced with better resolutio
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