7,338 research outputs found
Mechanical forcing of the North American monsoon by orography
A band of intense rainfall extends more than 1,000 km along Mexico’s west coast during Northern Hemisphere summer, constituting the core of the North American monsoon1,2. As in other tropical monsoons, this rainfall maximum is commonly thought to be thermally forced by emission of heat from land and elevated terrain into the overlying atmosphere3–5, but a clear understanding of the fundamental mechanism governing this monsoon is lacking. Here we show that the core North American monsoon is generated when Mexico’s Sierra Madre mountains deflect the extratropical jet stream towards the Equator, mechanically forcing eastward, upslope flow that lifts warm and moist air to produce convective rainfall. These findings are based on analyses of dynamic and thermodynamic structures in observations, global climate model integrations and adiabatic stationary wave solutions. Land surface heat fluxes do precondition the atmosphere for convection, particularly in summer afternoons, but these heat fluxes alone are insufficient for producing the observed rainfall maximum. Our results indicate that the core North American monsoon should be understood as convectively enhanced orographic rainfall in a mechanically forced stationary wave, not as a classic, thermally forced tropical monsoon. This has implications for the response of the North American monsoon to past and future global climate change, making trends in jet stream interactions with orography of central importance
Measuring the Higgs Branching Fraction into two Photons at Future Linear \ee Colliders
We examine the prospects for measuring the \gaga branching fraction of a
Standard Model-like Higgs boson with a mass of 120 GeV at the future TESLA
linear \ee collider, assuming an integrated luminosity of 1 ab and
center-of-mass energies of 350 GeV and 500 GeV. The Higgs boson is produced in
association with a fermion pair via the Higgsstrahlung process \ee ,
with \qq or \nn, or the WW fusion reaction . A relative uncertainty on BF(\hgg) of~16% can be achieved in
unpolarized \ee collisions at =~500 GeV, while for =~350
GeV the expected precision is slightly poorer. With appropriate initial state
polarizations BF(\hgg)/BF(\hgg) can be improved to 10%. If this
measurement is combined with the expected error for the total Higgs width, a
precision of 10% on the \gaga Higgs boson partial width appears feasible.Comment: 14 pages, 5 figure
Three Numerical Puzzles and the Top Quark's Chiral Weak-Moment
Versus the standard model's t --> W b decay helicity amplitudes, three
numerical puzzles occur at the 0.1 % level when one considers the amplitudes in
the case of an additional (f_M + f_E) coupling of relative strength 53 GeV. The
puzzles are theoretical ones which involve the t --> W b decay helicity
amplitudes in the two cases, the relative strength of this additional coupling,
and the observed masses of these three particles. A deeper analytic realization
is obtained for two of them. Equivalent realizations are given for the
remaining one. An empirical consequence of these analytic realizations is that
it is important to search for effects of a large chiral weak-moment of the
top-quark, the effective mass-scale is about 53 GeV. A full theoretical
resolution would include relating the origin of such a chiral weak-moment and
the mass generation of the top-quark, the W-boson, and probably the b-quark.Comment: 18 pages, 1 postscript table (revised to better explain notation,
model #1, add a little material...
Down Type Isosinglet Quarks in ATLAS
We evaluate the discovery reach of the ATLAS experiment for down type
isosinglet quarks, , using both their neutral and charged decay channels,
namely the process with subsequent decays resulting in
, and final states.
The integrated luminosity required for observation of a heavy quark is
estimated for a mass range between 600 and 1000 GeV using the combination of
results from different search channels.Comment: 12 page
Search for the intermediate Mass Higgs Signal at TeV colliders
The intermediate mass Higgs (IMH) can be abundantly produced through the
process at TeV colliders, which are
realized by the laser back-scattering method. We search for the signature of
plus missing transverse momentum, with and
without considering the -tagging. We also analyse all the potential
backgrounds from and . With our selective acceptance cuts these backgrounds
are reduced to a manageable level. We find that for the entire intermediate
mass range 60 -- 150~GeV the Higgs discovery should be viable. We also present
detail formulas for the helicity amplitudes of these processes.Comment: Latex(Revtex), 30 pages, 8 figures in postscript format (uuencoded),
NUHEP-TH-93-
Resonant CP Violation in Higgs Radiation at e^+e^- Linear Collider
We study resonant CP violation in the Higgsstrahlung process e^+e^- ->
H_{1,2,3} (Z -> e^+e^-, \mu^+\mu^-) and subsequent decays H_{1,2,3} -> b
\bar{b}, \tau^-\tau^+, in the MSSM with Higgs-sector CP violation induced by
radiative corrections. At a high-energy e^+e^- linear collider, the recoil-mass
method enables one to determine the invariant mass of a fermion pair produced
by Higgs decays with a precision as good as 1 GeV. Assuming an integrated
luminosity of 100/fb, we show that the production lineshape of a coupled system
of neutral Higgs bosons decaying into b\bar{b} quarks is sensitive to the
CP-violating parameters. When the Higgs bosons decay into \tau^-\tau^+, two CP
asymmetries can be defined using the longitudinal and transverse polarizations
of the tau leptons. Taking into account the constraints from electric dipole
moments, we find that these CP asymmetries can be as large as 80 %, in a
tri-mixing scenario where all three neutral Higgs states of the MSSM are nearly
degenerate and mix significantly.Comment: 22 pages, 8 figures, to appear in Phys. Rev.
Production of Doubly Charged Higgs Bosons at Linear e-e- Colliders
Production of doubly charged Higgs bosons via the s-channel process e-e- ->
H-- -> l-l- at future linear collider energies is studied by taking into
account initial state radiation (ISR) and beamstrahlung (ISR + BS), final state
radiation (FSR) and detector smearing effects. The discovery bounds of lepton
flavour conserving and violating couplings are obtained for doubly charged
Higgs bosons. It is found that future linear colliders with centre of mass
energies and will be able to probe the doubly charged Higgs bosons with
diagonal couplings down to 10^-4 and 10^-3, respectively.Comment: 22 pages, 12 figures, 4 table
Holonomy of the Ising model form factors
We study the Ising model two-point diagonal correlation function by
presenting an exponential and form factor expansion in an integral
representation which differs from the known expansion of Wu, McCoy, Tracy and
Barouch. We extend this expansion, weighting, by powers of a variable
, the -particle contributions, . The corresponding
extension of the two-point diagonal correlation function, , is shown, for arbitrary , to be a solution of the sigma
form of the Painlev{\'e} VI equation introduced by Jimbo and Miwa. Linear
differential equations for the form factors are obtained and
shown to have both a ``Russian doll'' nesting, and a decomposition of the
differential operators as a direct sum of operators equivalent to symmetric
powers of the differential operator of the elliptic integral . Each is expressed polynomially in terms of the elliptic integrals and . The scaling limit of these differential operators breaks the
direct sum structure but not the ``Russian doll'' structure. The previous -extensions, are, for singled-out values ( integers), also solutions of linear differential
equations. These solutions of Painlev\'e VI are actually algebraic functions,
being associated with modular curves.Comment: 39 page
Probing the Higgs mechanism via
We investigate the sensitivity of the reaction to
the Higgs sector based on the complete one-loop corrections in the minimal
Standard Model and the gauged non-linear -model. While this sensitivity
is very strong for the suppressed cross-section of equally polarized photons
and longitudinal W bosons, it is only marginal for the dominant mode of
transverse polarizations. The corrections within the -model turn out to
be UV-finite in accordance with the absence of \log\MH terms in the Standard
Model with a heavy Higgs boson.Comment: 12 pages uuencoded postscrip
Infrared Behavior of Three-Point Functions in Landau Gauge Yang-Mills Theory
Analytic solutions for the three-gluon and ghost-gluon vertices in Landau
gauge Yang-Mills theory at low momenta are presented in terms of hypergeometric
series. They do not only show the expected scaling behavior but also additional
kinematic divergences when only one momentum goes to zero. These singularities,
which have also been proposed previously, induce a strong dependence on the
kinematics in many dressing functions. The results are generalized to two and
three dimensions and a range of values for the ghost propagator's infrared
exponent kappa.Comment: 21 pages, 29 figures; numerical data of the infrared dressing
functions can be obtained from the authors v2: a few minor changes,
corresponds to version appearing in EPJ
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