51,806 research outputs found
Mass-degenerate Higgs bosons at 125 GeV in the Two-Higgs-Doublet Model
The analysis of the Higgs boson data by the ATLAS and CMS Collaborations
appears to exhibit an excess of h --> gamma\gamma events above the Standard
Model (SM) expectations; whereas no significant excess is observed in h --> ZZ*
--> {four lepton} events, albeit with large statistical uncertainty due to the
small data sample. These results (assuming they persist with further data)
could be explained by a pair of nearly mass-degenerate scalars, one of which is
a SM-like Higgs boson and the other is a scalar with suppressed couplings to
W+W- and ZZ. In the two Higgs doublet model, the observed \gamma\gamma and ZZ*
--> {four lepton} data can be reproduced by an approximately degenerate CP-even
(h) and CP-odd (A) Higgs boson for values of \sin(\beta-\alpha) near unity and
0.7 < \tan\beta < 1. An enhanced \gamma\gamma signal can also arise in cases
where m_h ~ m_H, m_H ~ m_A, or m_h ~ m_H ~ m_A. Since the ZZ* --> {four lepton}
signal derives primarily from a SM-like Higgs boson whereas the \gamma\gamma
signal receives contributions from two (or more) nearly mass-degenerate states,
one would expect a slightly different invariant mass peak in the ZZ* --> {four
lepton} and \gamma\gamma channels. The phenomenological consequences of such
models can be tested with additional Higgs data that will be collected at the
LHC in the near future.Comment: 18 pages, 19 pdf figures, v2: references added, v3&v4: added refs and
explanation
Preserving the validity of the Two-Higgs Doublet Model up to the Planck scale
We examine the constraints on the two Higgs doublet model (2HDM) due to the
stability of the scalar potential and absence of Landau poles at energy scales
below the Planck scale. We employ the most general 2HDM that incorporates an
approximately Standard Model (SM) Higgs boson with a flavor aligned Yukawa
sector to eliminate potential tree-level Higgs-mediated flavor changing neutral
currents. Using basis independent techniques, we exhibit robust regimes of the
2HDM parameter space with a 125 GeV SM-like Higgs boson that is stable and
perturbative up to the Planck scale. Implications for the heavy scalar spectrum
are exhibited.Comment: 36 pages, 4 figures, 4 tables (Version 3: typographical error in eq.
(A.28) corrected
Electrolytes between dielectric charged surfaces: Simulations and theory
We present a simulation method to study electrolyte solutions in a dielectric
slab geometry using a modified 3D Ewald summation. The method is fast and easy
to implement, allowing us to rapidly resum an infinite series of image charges.
In the weak coupling limit, we also develop a mean-field theory which allows us
to predict the ionic distribution between the dielectric charged plates. The
agreement between both approaches, theoretical and simulational, is very good,
validating both methods. Examples of ionic density profiles in the strong
electrostatic coupling limit are also presented. Finally, we explore the
confinement of charge asymmetric electrolytes between neutral surfaces
MIMAC-He3 : A Micro-TPC Matrix of Chambers of He3 for direct detection of Wimps
The project of a micro-TPC matrix of chambers of \hetrois for direct
detection of non-baryonic dark matter is presented. The privileged properties
of He3 are highlighted. The double detection (ionization - projection of
tracks) is explained and its rejection evaluated. The potentialities of
MIMAC-He3 for supersymmetric dark matter search are discussed.Comment: to appear in Proc. of the 9th International Conference on Topics in
Astroparticle and Underground Physics (TAUP 2005), Zaragoza, Sept. 200
Lorentz-violating nonminimal coupling contributions in mesonic hydrogen atoms and generation of photon higher-order derivative terms
We have studied the contributions of Lorentz-violating CPT-odd and CPT-even
nonminimal couplings to the energy spectrum of the mesonic hydrogen and the
higher-order radiative corrections to the effective action of the photon sector
of a Lorentz-violating version of the scalar electrodynamics. By considering
the complex scalar field describes charged mesons (pion or kaon), the
non-relativistic limit of the model allows to attain upper-bounds by analyzing
its contribution to the mesonic hydrogen energy. By using the experimental data
for the strong correction shift and the pure QED transitions , the best upper-bound for the CPT-odd coupling is
and for the CPT-even one is
. Besides, the CPT-odd radiative correction to the
photon action is a dimension-5 operator which looks like a higher-order
Carroll-Field-Jackiw term. The CPT-even radiative contribution to the photon
effective action is a dimension-6 operator which would be a higher-order
derivative version of the minimal CPT-even term of the standard model
extension
Coupling vortex dynamics with collective excitations in Bose-Einstein Condensates
Here we analyze the collective excitations as well as the expansion of a
trapped Bose-Einstein condensate with a vortex line at its center. To this end,
we propose a variational method where the variational parameters have to be
carefully chosen in order to produce reliable results. Our variational
calculations agree with numerical simulations of the Gross-Pitaevskii equation.
The system considered here turns out to exhibit four collective modes of which
only three can be observed at a time depending of the trap anisotropy. We also
demonstrate that these collective modes can be excited using well established
experimental methods such as modulation of the s-wave scattering length
Three-dimensional quasi-Tonks gas in a harmonic trap
We analyze the macroscopic dynamics of a Bose gas in a harmonic trap with a
superimposed two-dimensional optical lattice, assuming a weak coupling between
different lattice sites. We consider the situation in which the local chemical
potential at each lattice site can be considered as that provided by the
Lieb-Liniger solution. Due to the weak coupling between sites and the form of
the chemical potential, the three-dimensional ground-state density profile and
the excitation spectrum acquire remarkable properties different from both 1D
and 3D gases. We call this system a quasi-Tonks gas. We discuss the range of
applicability of this regime, as well as realistic experimental situations
where it can be observed.Comment: 4 pages, 3 figures, misprints correcte
- …