151 research outputs found
Higgs Mass Bounds Separate Models of Electroweak Symmetry Breaking
Vacuum stability implies a lower limit on the mass of the higgs boson in the
Standard Model (SM). In contrast, an upper limit on the lightest higgs mass can
be calculated in supersymmetric (susy) models. The main uncertainty in each
limit is the value of the top mass, which may now be fixed by the recent CDF
result. We study the possibility that these bounds do not overlap, and find
that (i) a mass gap emerges at GeV between the SM and the Minimal
Susy Standard Model (MSSM); and between the SM and the Minimal plus Singlet
Susy Model [(M+1)SSM] if the independent scalar self--coupling of the latter is
perturbatively small or if the parameter is large; this gap widens
with increasing ; (ii) there is no overlap between the SM and the MSSM
bounds at even smaller values of for the value (--2)
preferred in Supersymmetric Grand Unified Theories. Thus, if the new top mass
measurement remains valid, a measurement of the first higgs mass will serve to
exclude either the SM or MSSM/(M+1)SSM higgs sectors. In addition, we discuss
the upper bound on the lightest higgs mass in susy models with an extended
higgs sector, and in models with a strongly interacting higgs sector. Finally,
we comment on the discovery potential for the lightest higgses in these models.Comment: 18 pages, 5 figures, VAND-TH-94-1
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ADC Nonlinearity Correction for the Majorana Demonstrator
Imperfections in analog-to-digital conversion (ADC) cannot be ignored when signal digitization requirements demand both wide dynamic range and high resolution, as is the case for the Majorana Demonstrator 76Ge neutrinoless double-beta decay search. Enabling the experiment's high-resolution spectral analysis and efficient pulse shape discrimination required careful measurement and correction of ADC nonlinearities. A simple measurement protocol was developed that did not require sophisticated equipment or lengthy data-taking campaigns. A slope-dependent hysteresis was observed and characterized. A correction applied to digitized waveforms prior to signal processing reduced the differential and integral nonlinearities by an order of magnitude, eliminating these as dominant contributions to the systematic energy uncertainty at the double-beta decay Q value
Indication for the disappearance of reactor electron antineutrinos in the Double Chooz experiment
The Double Chooz Experiment presents an indication of reactor electron
antineutrino disappearance consistent with neutrino oscillations. A ratio of
0.944 0.016 (stat) 0.040 (syst) observed to predicted events was
obtained in 101 days of running at the Chooz Nuclear Power Plant in France,
with two 4.25 GW reactors. The results were obtained from a single 10
m fiducial volume detector located 1050 m from the two reactor cores. The
reactor antineutrino flux prediction used the Bugey4 measurement as an anchor
point. The deficit can be interpreted as an indication of a non-zero value of
the still unmeasured neutrino mixing parameter \sang. Analyzing both the rate
of the prompt positrons and their energy spectrum we find \sang = 0.086
0.041 (stat) 0.030 (syst), or, at 90% CL, 0.015 \sang 0.16.Comment: 7 pages, 4 figures, (new version after PRL referee's comments
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Results of the MAJORANA DEMONSTRATOR's Search for Double-Beta Decay of 76Ge to Excited States of 76Se
The MAJORANA DEMONSTRATOR is searching for double-beta decay of 76Ge to excited states (E.S.) in 76Se using a modular array of high purity Germanium detectors. 76Ge can decay into three E.S.s of 76Se. The E.S. decays have a clear event signature consisting of a ββ-decay with the prompt emission of one or two γ-rays, resulting in with high probability in a multi-site event. The granularity of the DEMONSTRATOR detector array enables powerful discrimination of this event signature from backgrounds. Using 21.3 kg-y of isotopic exposure, the DEMONSTRATOR has set world leading limits for each E.S. decay, with 90% CL lower half-life limits in the range of (0.56 2.1) ⋅ 1024 y. In particular, for the 2v transition to the first 0+ E.S. of 76Se, a lower half-life limit of 0.68 ⋅ 1024 at 90% CL was achieved
Yukawa Unified Supersymmetric SO(10) Model: Cosmology, Rare Decays and Collider Searches
It has recently been pointed out that viable sparticle mass spectra can be
generated in Yukawa unified SO(10) supersymmetric grand unified models
consistent with radiative breaking of electroweak symmetry. Model solutions are
obtained only if , and positive -term
contributions to scalar masses from SO(10) gauge symmetry breaking are used. In
this paper, we attempt to systematize the parameter space regions where
solutions are obtained. We go on to calculate the relic density of neutralinos
as a function of parameter space. No regions of the parameter space explored
were actually cosmologically excluded, and very reasonable relic densities were
found in much of parameter space. Direct neutralino detection rates could
exceed 1 event/kg/day for a Ge detector, for low values of GUT scale
gaugino mass . We also calculate the branching fraction for decays, and find that it is beyond the 95% CL experimental limits in
much, but not all, of the parameter space regions explored. However, recent
claims have been made that NLO effects can reverse the signs of certain
amplitudes in the calculation, leading to agreement between
theory and experiment in Yukawa unified SUSY models. For the Fermilab Tevatron
collider, significant regions of parameter space can be explored via
and searches. There also exist some limited regions of
parameter space where a trilepton signal can be seen at TeV33. Finally, there
exist significant regions of parameter space where direct detection of bottom
squark pair production can be made, especially for large negative values of the
GUT parameter .Comment: Added comparison to Blazek/Raby results and added Comments on de Boer
et al. b->s gamma result
Probing Supergravity Grand Unification in the Brookhaven g-2 Experiment
A quantitative analysis of \amu\equiv{1\over 2}(g-2)_\mu within the
framework of Supergravity Grand Unification and radiative breaking of the
electro-weak symmetry is given. It is found that is dominated
by the chiral interference term from the light chargino exchange, and that this
term carries a signature which correlates strongly with the sign of . Thus
as a rule for and for
with very few exceptions when tan. At the quantitative level it is
shown that if the E821 BNL experiment can reach the expected sensitivity of
and there is a reduction in the hadronic error by a factor
of four or more, then the experiment will explore a majority of the parameter
space in plane in the region m_0\lsim 400 GeV, m_{\tilde
g}\lsim 700 GeV for \tanbeta \gsim 10 assuming the experiment will not
discard the Standard Model result within its uncertainty limit. For
smaller \tanbeta, the SUSY reach of E821 will still be considerable. Further,
if no effect within limit of the Standard Model value is seen, then
large \tanbeta scenarios will be severely constrained within the current
naturalness criterion, ie., m_0, m_{\tilde g}\lsim 1 TeV.Comment: 27 pages, Latex, uuencoded figure file to be obtained and processed
separately for two figures. Figures may also be sent on request by mai
Resolving the Constrained Minimal and Next-to-Minimal Supersymmetric Standard Models
We perform a detailed analysis of the next-to-minimal supersymmetric standard
model (NMSSM), imposing the constraints of two-loop gauge coupling unification,
universal soft supersymmetry breaking and the correct pattern of electroweak
symmetry breaking. We compare our results with those for the minimal
supersymmetric standard model (MSSM) using closely related techniques and, as
far as possible, a common set of input and output variables. In general, in the
constrained NMSSM, there are much stronger correlations between parameters than
in the constrained MSSM, and we map out the allowed parameter space. We also
give a detailed discussion of how to resolve the two models experimentally,
concentrating primarily on the prospects at LEPII.Comment: 76 pages, latex, no macros, uuencoded figures included separately.
This version (to appear in Phys. Rev. D) contains various minor change
Cigarette Smoke-Related Hydroquinone Dysregulates MCP-1, VEGF and PEDF Expression in Retinal Pigment Epithelium in Vitro and in Vivo
Age-related macular degeneration (AMD) is the leading cause of legal blindness in the elderly population. Debris (termed drusen) below the retinal pigment epithelium (RPE) have been recognized as a risk factor for dry AMD and its progression to wet AMD, which is characterized by choroidal neovascularization (CNV). The underlying mechanism of how drusen might elicit CNV remains undefined. Cigarette smoking, oxidative damage to the RPE and inflammation are postulated to be involved in the pathophysiology of the disease. To better understand the cellular mechanism(s) linking oxidative stress and inflammation to AMD, we examined the expression of pro-inflammatory monocyte chemoattractant protein-1 (MCP-1), pro-angiogenic vascular endothelial growth factor (VEGF) and anti-angiogenic pigment epithelial derived factor (PEDF) in RPE from smoker patients with AMD. We also evaluated the effects of hydroquinone (HQ), a major pro-oxidant in cigarette smoke on MCP-1, VEGF and PEDF expression in cultured ARPE-19 cells and RPE/choroids from C57BL/6 mice.MCP-1, VEGF and PEDF expression was examined by real-time PCR, Western blot, and ELISA. Low levels of MCP-1 protein were detected in RPE from AMD smoker patients relative to controls. Both MCP-1 mRNA and protein were downregulated in ARPE-19 cells and RPE/choroids from C57BL/6 mice after 5 days and 3 weeks of exposure to HQ-induced oxidative injury. VEGF protein expression was increased and PEDF protein expression was decreased in RPE from smoker patients with AMD versus controls resulting in increased VEGF/PEDF ratio. Treatment with HQ for 5 days and 3 weeks increased the VEGF/PEDF ratio in vitro and in vivo.We propose that impaired RPE-derived MCP-1-mediated scavenging macrophages recruitment and phagocytosis might lead to incomplete clearance of proinflammatory debris and infiltration of proangiogenic macrophages which along with increased VEGF/PEDF ratio favoring angiogenesis might promote drusen accumulation and progression to CNV in smoker patients with dry AMD
The CARMENES search for exoplanets around M dwarfs High-resolution optical and near-infrared spectroscopy of 324 survey stars
The CARMENES radial velocity (RV) survey is observing 324 M dwarfs to search for any orbiting planets. In this paper, we present the survey sample by publishing one CARMENES spectrum for each M dwarf. These spectra cover the wavelength range 520–1710 nm at a resolution of at least R >80 000, and we measure its RV, Hα emission, and projected rotation velocity. We present an atlas of high-resolution M-dwarf spectra and compare the spectra to atmospheric models. To quantify the RV precision that can be achieved in low-mass stars over the CARMENES wavelength range, we analyze our empirical information on the RV precision from more than 6500 observations. We compare our high-resolution M-dwarf spectra to atmospheric models where we determine the spectroscopic RV information content, Q, and signal-to-noise ratio. We find that for all M-type dwarfs, the highest RV precision can be reached in the wavelength range 700–900 nm. Observations at longer wavelengths are equally precise only at the very latest spectral types (M8 and M9). We demonstrate that in this spectroscopic range, the large amount of absorption features compensates for the intrinsic faintness of an M7 star. To reach an RV precision of 1 m s−1 in very low mass M dwarfs at longer wavelengths likely requires the use of a 10 m class telescope. For spectral types M6 and earlier, the combination of a red visual and a near-infrared spectrograph is ideal to search for low-mass planets and to distinguish between planets and stellar variability. At a 4 m class telescope, an instrument like CARMENES has the potential to push the RV precision well below the typical jitter level of 3–4 m s−1
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