1,081 research outputs found
Clear Experimental Signature of Charge-Orbital density wave in NdCaMnO
Single Crystals of NdCaMnO have been prepared by the
travelling floating-zone method, and possible evidence of a charge -orbital
density wave in this material presented earlier [PRB68,092405 (2003)] using
High Resolution Electron Microscopy [HRTEM] and Electron Diffraction [ED]. In
the current note we present direct evidence of charge-orbital ordering in this
material using heat capacity measurements. Our heat capacity measurements
indicate a clear transition consistent with prior observation. We find two main
transitions, one at temperature K, and other at
K. In addition, we may also conclude that there is a strong electron-phonon
coupling in this material.Comment: 7 pages, 8 figure
Vacuum Stability Higgs Mass Bound Revisited with Implications for Extra Dimension Theories
We take the standard model to be an effective theory including higher
dimensional operators suppressed by scale and re-examine the higgs
mass bounds from the requirements of vacuum stability. Our results show that
the effects of the higher dimensional operators on the higgs mass limits are
significant. As an implication of our results, we study the vacuum stability
higgs mass bounds in theories with extra dimensions.Comment: Latex, 14 pages, 1 figure. Added references. To appear in Phys. Rev.
Large Electric Dipole Moments of Heavy Leptons
In many models of CP violation, the electric dipole moments (EDMs) of leptons
scale as the cube of the lepton mass. In these models, the EDM of a 100 GeV
heavy lepton would be a billion times greater than that of the muon, and could
be as large as a 0.01 e-fermi. In other models, in which the heavy leptons have
different properties from the lighter generations, a similarly large EDM can be
obtained. A large EDM could dominate the electromagnetic properties of heavy
leptons. The angular distribution and production cross-section of both charged
and neutral heavy leptons with large dipole moments is calculated and
discussed. The interesting possibility that a heavy neutrino with a large EDM
could leave an ionization track in a drift chamber is investigated.Comment: Discussion expanded extensively to include model-dependence of
results. Calculations unchanged. Note Added To Acknowledgments: This paper is
dedicated to the memory of Nathan Isgu
Universal Extra Dimensions and Kaluza Klein Bound States
We study the bound states of the Kaluza-Klein (KK) excitations of quarks in
certain models of Universal Extra Dimensions. Such bound states may be detected
at future lepton colliders in the cross section for the pair production of
KK-quarks near threshold. For typical values of model parameters, we find that
"KK-quarkonia" have widths in the 10 - 100 MeV range, and production cross
sections of order a few picobarns for the lightest resonances. Two body decays
of the constituent KK-quarks lead to distinctive experimental signatures. We
point out that such KK resonances may be discovered before any of the higher KK
modes.Comment: 21 pages LaTeX, 9 eps figure
Production of (super)heavy quarkonia and new Higgs physics at hadron colliders
Based on the two Higgs doublet model, we study the effect of Higgs-boson
exchange on the (super)heavy quarkonium \bar QQ, which induces a strong
attractive force between a (super)heavy quark Q and an antiquark \bar Q. An
interesting application is the decay of (super)heavy quarkonia \bar QQ into a
Higgs boson associated with gauge bosons. The criterion for making the \bar QQ
bound state is studied. We also show that non-perturbative effects due to
gluonic field fluctuations are rather small in such a heavy quark sector.
Possible enhancement for productions and decays of \bar QQ bound states made
from the fourth generation quark Q is discussed for \bar p p (at the Tevatron)
and pp (at the LHC) collisions.Comment: 18 pages, REVTeX, 9 figures. V2: minor changes, references and
acknowledgments adde
Higgs and SUSY searches at future colliders
In this talk, I discuss some aspects of Higgs searches at future colliders,
particularly comparing and contrasting the capabilities of LHC and Next Linear
Collider (NLC), including the aspects of Higgs searches in supersymmetric
theories. After this, I will discuss how the search and study of sparticles
other than the Higgs can give information about the parameters of the Minimal
Supersymmetric Standard Model (MSSM).Comment: 20 pages, 12 figures, laTeX, requires pramana.sty,ias.sty added. In
the Proceedings of XII DAE symposium, Chandigarh, December 199
The renormalization group and spontaneous compactification of a higher-dimensional scalar field theory in curved spacetime
The renormalization group (RG) is used to study the asymptotically free
-theory in curved spacetime. Several forms of the RG equations for
the effective potential are formulated. By solving these equations we obtain
the one-loop effective potential as well as its explicit forms in the case of
strong gravitational fields and strong scalar fields. Using zeta function
techniques, the one-loop and corresponding RG improved vacuum energies are
found for the Kaluza-Klein backgrounds and . They are given in terms of exponentially convergent series, appropriate
for numerical calculations. A study of these vacuum energies as a function of
compactification lengths and other couplings shows that spontaneous
compactification can be qualitatively different when the RG improved energy is
used.Comment: LaTeX, 15 pages, 4 figure
A Multi-scale Subtraction Scheme and Partial Renormalization Group Equations in the -symmetric -theory
To resum large logarithms in multi-scale problems a generalization of \MS
is introduced allowing for as many renormalization scales as there are generic
scales in the problem. In the new \lq\lq minimal multi-scale subtraction
scheme'' standard perturbative boundary conditions become applicable. However,
the multi-loop beta functions depend on the various renormalization scale
ratios and a large logarithms resummation has to be performed on them. Using
these improved beta functions the \lq\lq partial'' renormalization group
equations corresponding to the renormalization point independence of physical
quantities allows one to resum the logarithms. As an application the leading
and next-to-leading order two-scale analysis of the effective potential in the
-symmetric -theory is performed. This calculation indicates that
there is no stable vacuum in the broken phase of the theory for .Comment: 27 pages, LaTex, no figures (a version with three figures is
available from the authors
Top quark electric and chromo electric dipole moments in the general two Higgs Doublet model
We study the electric and chromo electric dipole moment of top quark in the
general two Higgs Doublet model (model III). We analyse the dependency of this
quantity to the new phases coming from the complex Yukawa couplings and masses
of charged and neutral Higgs bosons. We observe that the electric and chromo
elecric dipole moments of top quark are at the order of 10^{-21} e cm and
10^{-20} g_s cm, which are extremely large values compared to ones calculated
in the SM and also two Higgs Doublet model with real Yukawa couplings.Comment: 9 pages,10 figure
- …