236 research outputs found
Working Paper 35: Carbon Cycling in Southwestern Forests: Reservoirs, Fluxes, and the Effects of Fire and Management
Forests play a key role in regulating the carbon cycle
of the Earth system. Understanding carbon storage in forest ecosystems has become increasingly important as human activities release more carbon dioxide (CO2) into the Earthâs atmosphere. The intent of this working paper is to explain the basics of the carbon cycle detailing how much carbon moves through vegetation, water, and soils over time. The paper also summarizes where current science suggests that carbon cycling patterns are most likely to change in the coming years to decades, and how management can influence these changes.
Water (H2O) and atmospheric gases, particularly carbon dioxide, interact with living things, soils and rock to regulate natural habitats and sustain ecosystems (NRC 2001). The capacity of landscapes to transfer (âfluxâ) and store (âsequesterâ) elemental carbon has a direct effect on atmospheric concentrations of CO2 with further feedbacks on the water and nitrogen cycles. In the literature, carbon contained in vegetation and soils is typically referred to as âreservoirsâ or âpoolsâ (Post et al. 1990, Schimel 1995, Cole et al. 2007)
Fact Sheet: Carbon Cycling in Southwestern Forests: Reservoirs, Fluxes, and the Effects of Fire and Management
Forest death from extreme drought and wildfires are reducing regional carbon reservoirs and overall forest sequestration capacity. At the same time, land use practices and development have increased the vulnerabil- ity of some forests during extreme droughts. The intent of this fact sheet is to explain the basics of the car- bon cycle in southwestern forests. It also summarizes how carbon cycling patterns are most likely to change in the coming years to decades in the Southwest
Higgs pair production in the MSSM with explicit CP violation
In the minimal supersymmetric standard model with explicit CP violation,
associated production of the lightest Higgs boson with heavier ones is
analyzed. Due to explicit CP violation, the Higgs bosons are no longer CP
eigenstates so that both of the heavy Higgs bosons contribute to the process.
While the radiative corrections in the Higgs sector turn out to be quite
important, the vertex radiative corrections remain small as in the CP
conserving theory.Comment: 5 pp, 5 figs, Talk at Valencia 99, Valencia, Spain, May 3-8, 199
Using tourism free-choice learning experiences to promote environmentally sustainable behaviour: The role of post-visit âaction resourcesâ
This paper argues the need for the providers of ecotourism and other freeâchoice environmental learning experiences to promote the adoption of environmentally sustainable actions beyond their own sites, when visitors return to their home environments. Previous research indicates that although visitors often leave such experiences with a heightened awareness of conservation issues and intentions to adopt environmentally responsible behaviours, only a minority translate these intentions into real actions. Building on research and theory in relation to visitor experiences in freeâchoice learning environments, the paper identifies three different stages in the educational process and proposes a strategy for facilitating the translation of visitors' behavioural intentions into the adoption of sustainable actions through the provision of postâvisit action resources
s-Channel Production of MSSM Higgs Bosons at a Muon Collider with Explicit CP Violation
A muon collider with controllable energy resolution and transverse beam
polarization provides a powerful probe of the Higgs sector in the minimal
supersymmetric standard model with explicit CP violation, through s-channel
production of Higgs bosons. The production rates and the CP-even and CP-odd
transverse-polarization asymmetries are complementary in diagnosing CP
violation in the Higgs sector.Comment: 12 pages, 5 figures. Some statements for clarity and references
added. To appear in Phys. Rev.
CP Phases in Correlated Production and Decay of Neutralinos in the Minimal Supersymmetric Standard Model
We investigate the associated production of neutralinos
accompanied by the neutralino
leptonic decay , taking into
account initial beam polarization and production-decay spin correlations in the
minimal supersymmetric standard model with general CP phases but without
generational mixing in the slepton sector. The stringent constraints from the
electron EDM on the CP phases are also included in the discussion. Initial beam
polarizations lead to three CP--even distributions and one CP--odd
distribution, which can be studied independently of the details of the
neutralino decays. We find that the production cross section and the branching
fractions of the leptonic neutralino decays are very sensitive to the CP
phases. In addition, the production--decay spin correlations lead to several
CP--even observables such as lepton invariant mass distribution, and lepton
angular distribution, and one interesting T--odd (CP--odd) triple product of
the initial electron momentum and two final lepton momenta, the size of which
might be large enough to be measured at the high--luminosity future
electron--positron collider or can play a complementary role in constraining
the CP phases with the EDM constraints.Comment: Revtex, 37 pages, 12 eps figure
Probing MSSM Higgs Sector with Explicit CP Violation at a Photon Linear Collider
The CP properties of Higgs bosons can be probed through their s-channel
resonance productions via photon-photon collisions by use of circularly and/or
linearly polarized backscattered laser photons at a TeV-scale linear e^+ e^-
collider. Exploiting this powerful tool, we investigate in detail the Higgs
sector of the minimal supersymmetric Standard Model with explicit CP violation.Comment: 18 pages, 5 figures. Some comments added and typos corrected. To
appear in Phys. Rev.
Additional phases induced by the supersymmetric CP phases
The explicit CP violation in the MSSM radiatively induces a finite
unremovable alignment between the Higgs doublets. This additinal phase can be
as large as the original CP phases in certain portions of the MSSM parameter
space. Considering the specific case of the charginos, this additional phase is
shown to induce a conceivable amount of CP violation near the would--be CP
conserving points. Moreover, the CP violation in the absence of this phase is
smaller than the one in the presence of it, and the former can never compete
with the latter, however large is.Comment: 29 pp, 15 fig
Instantons and the endpoint of the lepton energy spectrum in charmless semileptonic decays
A recent calculation by Chay and Rey has shown that instantons may make a
significant contribution to the lepton energy spectrum near its endpoint. Using
an ansatz borrowed from the study of high energy baryon number violating
processes, we investigate whether these corrections could spoil the relation
between the nonperturbative contributions to this spectrum and to the photon
energy spectrum in radiative decays. We find, in general, that this
universality may well fail unless the spectrum is smeared over a region which
is considerably larger than had previously been thought necessary. This result
affects the possibility of performing a reliable measurement of using
inclusive decays.Comment: Slightly revised version, to appear in Phys. Rev. D. A few additional
comments have been added on the approximations which are used. 13 pages, 2
embedded uuencoded figures, uses REVTe
Effects of the supersymmetric phases on the neutral Higgs sector
By using the effective potential approximation and taking into account the
dominant top quark and scalar top quark loops, radiative corrections to MSSM
Higgs potential are computed in the presence of the supersymmetric CP-violating
phases. It is found that, the lightest Higgs scalar remains essentially CP-even
as in the CP-invariant theory whereas the other two scalars are heavy and do
not have definite CP properties. The supersymmetric CP-violating phases are
shown to modify significantly the decay rates of the scalars to fermion pairs.Comment: 24 pp, 8 figs, 2 tables, typos and errors correcte
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