7,058 research outputs found
Detecting Gluino-Containing Hadrons
When SUSY breaking produces only dimension-2 operators, gluino and photino
masses are of order 1 GeV or less. The gluon-gluino bound state has mass
1.3-2.2 GeV and lifetime > 10^{-5} - 10^{-10} s. This range of mass and
lifetime is largely unconstrained because missing energy and beam dump
techniques are ineffective. With only small modifications, upcoming K^0 decay
experiments can study most of the interesting range. The lightest
gluino-containing baryon (uds-gluino) is long-lived or stable; experiments to
find it and the uud-gluino are also discussed.Comment: 13 pp, 1 figure (uuencoded). Descendant of hep-ph/9504295,
hep-ph/9508291, and hep-ph/9508292, focused on experimental search
techniques. To be published in Phys Rev Let
A procedure for implanting a spinal chamber for longitudinal in vivo imaging of the mouse spinal cord.
Studies in the mammalian neocortex have enabled unprecedented resolution of cortical structure, activity, and response to neurodegenerative insults by repeated, time-lapse in vivo imaging in live rodents. These studies were made possible by straightforward surgical procedures, which enabled optical access for a prolonged period of time without repeat surgical procedures. In contrast, analogous studies of the spinal cord have been previously limited to only a few imaging sessions, each of which required an invasive surgery. As previously described, we have developed a spinal chamber that enables continuous optical access for upwards of 8 weeks, preserves mechanical stability of the spinal column, is easily stabilized externally during imaging, and requires only a single surgery. Here, the design of the spinal chamber with its associated surgical implements is reviewed and the surgical procedure is demonstrated in detail. Briefly, this video will demonstrate the preparation of the surgical area and mouse for surgery, exposure of the spinal vertebra and appropriate tissue debridement, the delivery of the implant and vertebral clamping, the completion of the chamber, the removal of the delivery system, sealing of the skin, and finally, post-operative care. The procedure for chronic in vivo imaging using nonlinear microscopy will also be demonstrated. Finally, outcomes, limitations, typical variability, and a guide for troubleshooting are discussed
A Window in the Dark Matter Exclusion Limits
We consider the cross section limits for light dark matter candidates
( to 10 GeV). We calculate the interaction of dark matter in the crust
above underground dark matter detectors and find that in the intermediate cross
section range, the energy loss of dark matter is sufficient to fall below the
energy threshold of current underground experiments. This implies the existence
of a window in the dark matter exclusion limits in the micro-barn range.Comment: 10 pages, 8 figure
Living roots magnify the response of soil organic carbon decomposition to temperature in temperate grassland.
Increasing atmospheric carbon dioxide (CO2) concentration is both a strong driver of primary productivity and widely believed to be the principal cause of recent increases in global temperature. Soils are the largest store of the world's terrestrial C. Consequently, many investigations have attempted to mechanistically understand how microbial mineralisation of soil organic carbon (SOC) to CO2 will be affected by projected increases in temperature. Most have attempted this in the absence of plants as the flux of CO2 from root and rhizomicrobial respiration in intact plant-soil systems confounds interpretation of measurements. We compared the effect of a small increase in temperature on respiration from soils without recent plant C with the effect on intact grass swards. We found that for 48 weeks, before acclimation occurred, an experimental 3 °C increase in sward temperature gave rise to a 50% increase in below ground respiration (ca.0.4 kg C m−2; Q10=3.5), whereas mineralisation of older SOC without plants increased with a Q10 of only 1.7 when subject to increases in ambient soil temperature. Subsequent 14C dating of respired CO2 indicated that the presence of plants in swards more than doubled the effect of warming on the rate of mineralisation of SOC with an estimated mean C age of ca.8 y or older relative to incubated soils without recent plant inputs. These results not only illustrate the formidable complexity of mechanisms controlling C fluxes in soils, but also suggest that the dual biological and physical effects of CO2 on primary productivity and global temperature have the potential to synergistically increase the mineralisation of existing soil C
Mock Catalogs for UHECR Studies
We provide realistic mock-catalogs of cosmic rays above 40 EeV, for a pure
proton composition, assuming their sources are a random subset of ordinary
galaxies in a simulated, volume-limited survey, for various choices of source
density: 10^-3.5 Mpc^-3, 10^-4.0 Mpc^-3 and 10^-4.5 Mpc^-3. The spectrum at the
source is taken to be E^-2.3 and the effects of cosmological redshifting as
well as photo-pion and e^+ e^- energy losses are included.Comment: 7 pages, 4 figure
Effective CP violation in the Standard Model
We study the strength of effective CP violation originating from the CKM
matrix in the effective action obtained by integrating out the fermions in the
Standard Model. Using results obtained by Salcedo for the effective action in a
general chiral gauge model, we find that there are no CKM CP-violating terms to
fourth order in a gauge-covariant derivative expansion that is non-perturbative
in the Higgs field. The details of the calculation suggest that, at zero
temperature, the strength of CP violation is approximately independent of the
overall scale of the Yukawa couplings. Thus, order of magnitude estimates based
on Jarlskog's invariant could be too small by a factor of about 10^{17}.Comment: 19 pages, no figure
Radiative Decay of Vector Quarkonium: Constraints on Glueballs and Light Gluinos
Given a resonance of known mass, width, and J^{PC}, we can determine its
gluonic branching fraction, b(R->gg), from data on its production in radiative
vector quarkonium decay, V -> gamma+R. For most resonances b(R->gg) is found to
be O(10%), consistent with being q-qbar states, but we find that both
pseudoscalars observed in the 1440 MeV region have b(R->gg) ~ 1/2 - 1, and
b(f_0^{++}->gg) ~ 1/2. As data improves, b(R->gg) should be a useful
discriminator between q-qbar and gluonic states and may permit quantitative
determination of the extent to which a particular resonance is a mixture of
glueball and q-qbar. We also examine the regime of validity of pQCD for
predicting the rate of V -> gamma+eta_gluino, the ``extra'' pseudoscalar bound
state which would exist if there were light gluinos. From the CUSB limit on
peaks in Upsilon -> gamma X, the mass range 3 GeV < m(eta_gluino) < 7 GeV can
be excluded. An experiment must be significantly more sensitive to exclude an
eta_gluino lighter than this.Comment: 36pp (inc figs),RU-94-04. (Replaces original which didn't latex
correctly and didn't have figures.
Diary of Colonel and Mrs. I.N. Ebey
"Whidby Island has always figured in the history of the Puget Sound country…No further attempt at settlement was made until the arrival of Isaac N. Ebey, in 1850.
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