653 research outputs found
A Comparison of Mixed-Higgs Scenarios In the NMSSM and the MSSM
We study scenarios in the minimal and next-to minimal supersymmetric models
in which the lightest CP-even Higgs boson can have mass below the 114 GeV
standard model LEP limit by virtue of reduced ZZ coupling due to substantial
mixing among the Higgs bosons. We pay particular attention to the size of
corrections from superpartners needed for these scenarios to be viable and
point to boundary conditions at large scales which lead to these scenarios
while at the same time keeping electroweak fine tuning modest in size. We find
that naturalness of electroweak symmetry breaking in the mixed-Higgs scenarios
of both models points to the same region of soft supersymmetry breaking terms,
namely those leading to large mixing in the stop sector at the electroweak
scale, especially if we also require that the lightest CP-even Higgs explains
the Higgs-like LEP events at about 98 GeV.Comment: 14 pages, 19 figure
The NMSSM Solution to the Fine-Tuning Problem, Precision Electroweak Constraints and the Largest LEP Higgs Event Excess
We present an extended study of how the Next to Minimal
Supersymmetric Model easily avoids fine-tuning in electroweak symmetry
breaking for a SM-like light Higgs with mass in the vicinity of 100\gev, as
beautifully consistent with precision electroweak data, while escaping LEP
constraints due to the dominance of decays with so that
a\to \tauptaum or jets. The residual branching ratio for h\to
b\anti b explains perfectly the well-known LEP excess at \mh\sim 100\gev.
Details of model parameter correlations and requirements are discussed as a
function . Comparisons of fine-tuning in the NMSSM to that in the
MSSM are presented. We also discuss fine-tuning associated with scenarios in
which the is essentially pure singlet, has mass m_a>30\gev, and decays
primarily to \gam\gam leading to an h\to aa\to 4\gam Higgs signal.Comment: 26 pages, 37 figures, published version with minor text and reference
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Fulde-Ferrell-Larkin-Ovchinnikov Superconducting State in CeCoIn5
We report specific heat measurements of the heavy fermion superconductor
CeCoIn5 in the vicinity of the superconducting critical field H_{c2}, with
magnetic field in the [110], [100], and [001] directions, and at temperatures
down to 50 mK. The superconducting phase transition changes from second to
first order for field above 10 T for H || [110] and H || [100]. In the same
range of magnetic field we observe a second specific heat anomaly within the
superconducting state. We interpret this anomaly as a signature of a
Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) inhomogeneous superconducting state. We
obtain similar results for H || [001], with FFLO state occupying a smaller part
of the phase diagram.Comment: 4 pages, 3 figures, submitted to Phys. Rev. Letter
Unusual Higgs or Supersymmetry from Natural Electroweak Symmetry Breaking
This review provides an elementary discussion of electroweak symmetry
breaking in the minimal and the next-to-minimal supersymmetric models with the
focus on the fine-tuning problem -- the tension between natural electroweak
symmetry breaking and the direct search limit on the Higgs boson mass. Two
generic solutions of the fine-tuning problem are discussed in detail: models
with unusual Higgs decays; and models with unusual pattern of soft
supersymmetry breaking parameters.Comment: 23 pages, 6 figures; invited review by MPL
Anisotropy of Thermal Conductivity and Possible Signature of the Fulde-Ferrell-Larkin-Ovchinnikov state in CeCoIn_5
We have measured the thermal conductivity of the heavy-fermion superconductor
CeCoIn_5 in the vicinity of the upper critical field, with the magnetic field
perpendicular to the c axis. Thermal conductivity displays a discontinuous jump
at the superconducting phase boundary below critical temperature T_0 ~ 1 K,
indicating a change from a second to first order transition and confirming the
recent results of specific heat measurements on CeCoIn_5. In addition, the
thermal conductivity data as a function of field display a kink at a field H_k
below the superconducting critical field, which closely coincides with the
recently discovered anomaly in specific heat, tentatively identified with the
appearance of the spatially inhomogeneous Fulde-Ferrell-Larkin-Ovchinnikov
(FFLO) superconducting state. Our results indicate that the thermal
conductivity is enhanced within the FFLO state, and call for further
theoretical investigations of the order parameter's real space structure (and,
in particular, the structure of vortices) and of the thermal transport within
the inhomogeneous FFLO state.Comment: 19 pages, 6 figures, submitted to Prhys. Rev.
Biochemical correlates of cardiac hypertrophy. I. Experimental model; changes in heart weight, RNA content, and nuclear RNA polymerase activity
Cardiac hypertrophy occurred in mature rats after producing supravalvular aortic stenosis with a specially designed silver clip. For 2 weeks following this procedure, heart weight, body weight, and RNA content of the myocardium were serially determined. Heart weight and RNA content increased within 24 hours of aortic banding, reaching a maximal level in 2 days and remaining elevated during the 2 weeks of observation. Nuclei were isolated and purified from heart muscle homogenates, and changes in RNA polymerase activity following aortic banding were determined. The nearest neighbor frequency of the bases of the RNA synthesized by the polymerase from nuclear preparations was identical in both the banded animals and the sham-operated controls. Both groups could thus be compared on the basis of the enzyme assay. RNA polymerase activity in nuclei from the hearts of banded rats rose rapidly when compared with the activity in sham-operated rats; peak values were reached on the second day, the earliest detectable change being around 12 hours. The increase in RNA polymerase activity represents one of the earliest biochemical events that take place in the myocardium following aortic banding
The Fulde-Ferrell-Larkin-Ovchinnikov State in the Organic Superconductor k-(BEDT-TTF)2Cu(NCS)2 as Observed in Magnetic Torque Experiments
We present magnetic-torque experiments on the organic superconductor
k-(BEDT-TTF)2Cu(NCS)2 for magnetic fields applied parallel to the 2D
superconducting layers. The experiments show a crossover from a second-order to
a first-order transition when the upper critical field reaches 21 T. Beyond
this field, which we interpret as the Pauli limit for superconductivity, the
upper critical field line shows a pro-nounced upturn and a phase transition
line separates the superconducting state into a low- and a high-field phase. We
interpret the data in the framework of a Fulde-Ferrell-Larkin-Ovchinnikov
state.Comment: 2 pages, 1 figur
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