3,111 research outputs found
The Status of Inelastic Dark Matter
In light of recent positive results from the DAMA experiment, as well as new
null results from CDMS Soudan, Edelweiss, ZEPLIN-I and CRESST, we reexamine the
framework of inelastic dark matter with a standard halo. In this framework,
which was originally introduced to reconcile tensions between CDMS and DAMA,
dark matter particles can scatter off of nuclei only by making a transition to
a nearly degenerate state that is roughly 100 \kev heavier. We find that
recent data significantly constrains the parameter space of the framework, but
that there are still regions consistent with all experimental results. Due to
the enhanced annual modulation and dramatically different energy dependence in
this scenario, we emphasize the need for greater information on the dates of
data taking, and on the energy distribution of signal and background. We also
study the specific case of ``mixed sneutrino'' dark matter, and isolate regions
of parameter space which are cosmologically interesting for that particular
model. A significant improvement in limits by heavy target experiments such as
ZEPLIN or CRESST should be able to confirm or exclude the inelastic dark matter
scenario in the near future. Within the mixed sneutrino model, an elastic
scattering signature should be seen at upcoming germanium experiments,
including future results from CDMS Soudan.Comment: 8 pages, 5 figures; updated to include CRESST results; version to
appear in Phys.Rev.
GUT Breaking on the Brane
We present a five-dimensional supersymmetric SU(5) theory in which the gauge
symmetry is broken maximally (i.e. at the 5D Planck scale M_*) on the same 4D
brane where chiral matter is localized. Masses of the lightest Kaluza-Klein
modes for the colored Higgs and X and Y gauge fields are determined by the
compactification scale of the fifth dimension, M_C ~ 10^{15} GeV, rather than
by M_*. These fields' wave functions are repelled from the GUT-breaking brane,
so that proton decay rates are suppressed below experimental limits. Above the
compactification scale, the differences between the standard model gauge
couplings evolve logarithmically, so that ordinary logarithmic gauge coupling
unification is preserved. The maximal breaking of the grand unified group can
also lead to other effects, such as O(1) deviations from SU(5) predictions of
Yukawa couplings, even in models utilizing the Froggatt-Nielsen mechanism.Comment: 20 pages, 3 figure
The Effects of Numeracy and Brand Preference on the Left-Digit Effect
A left-digit effect (LDE) is said to occur when a change in the left-most digit of a value (e.g., when \$4.00 drops to \$2.99 versus when it drops from \$4.01 to \$3.00) significantly increases consumer judgments of the price difference. Thomas and Morwitz (2005) showed that it was the change in the left-digit, rather than the one-cent drop, that affects these perceptions. This effect has domain invariance, meaning the left-digit effect manifests not only in prices, but also in other types of nine-ending numbers (Thomas & Morwitz, 2005). The finding has important implications for pricing practices.
The present study examined whether individual differences in numeracy or affective information based on brand preference influence the left-digit effect. Peters et al. (2006) defined numeracy as the ability to use and understand basic probability and mathematical concepts. People range widely in their ability to use numbers, and the highly numerate encode numeracy and non-numeric information differently than the less numerate when making decisions. We predict that numeracy ability along with brand preference can help negate the left-digit effect and lead to better magnitude perceptions. Using a modification of the experimental paradigm from Thomas and Morwitz, we showed participants two 12-packs of soda that either have a brand name (Coke and Pepsi) or are generic (the control condition). Subsequently, subjects stated their preference between the sodas (e.g., ranging from strongly prefer Coke to strongly prefer Pepsi in the experimental condition). Subjects then took an eight-question math test to assess their numeracy ability (Weller et al., 2012). Results indicated that overall more numerate individuals paradoxically showed larger LDEs. Participants did not show significantly larger LDEs when brand names were used versus when they were not.No embarg
Rapid design/development and clinical deployment of synthetic DNA vaccine technology for difficult immune targets
Recent major improvements in synthetic DNA vaccine technology have changed our view of the use of this platform to impact infectious disease. Synthetic DNA has moved from a weak immune performer, to a highly consistent immune potent platform with the ability to generate protective immune responses in a rapid fashion. We present important recent examples of translational development for important targets such as HPV infection, Ebola, and Zika. Finally, the enhancement of this technology now enables an ability to launch DNA encoded MAb’s. This opens novel areas and new approaches for difficult and important disease targets
An Effective Z'
We describe a method to couple Z' gauge bosons to the standard model (SM),
without charging the SM fields under the U(1)', but instead through effective
higher dimension operators. This method allows complete control over the
tree-level couplings of the Z' and does not require altering the structure of
any of the SM couplings, nor does it contain anomalies or require introduction
of fields in non-standard SM representations. Moreover, such interactions arise
from simple renormalizable extensions of the SM - the addition of vector-like
matter that mixes with SM fermions when the U(1)' is broken. We apply effective
Z' models as explanations of various recent anomalies: the D0 same-sign dimuon
asymmetry, the CDF W+di-jet excess and the CDF top forward-backward asymmetry.
In the case of the W+di-jet excess we also discuss several complementary
analyses that may shed light on the nature of the discrepancy. We consider the
possibility of non-Abelian groups, and discuss implications for the
phenomenology of dark matter as well.Comment: 44 pages; 5 figures. References added, discussion of gamma+jj
constraints update
Applications of DNA vaccine technology towards difficult immune targets
Major improvement in DNA vaccine technology over the past decade has reinvigorated this platform which has conceptual advantages over traditional vaccine platforms. In humans prior generations of DNA vaccines were poorly immunogenic. Through multiple improvements including synthetic optimization, genetic adjuvant technology with enhanced EP delivery this technology exhibits improved performance. These synthetic DNA vaccines drive immune responses similar or superior to live viral vectors. We present data in animal models and in human studies that illuminate their immune potency and clinical efficacy targeting both established infection and in prevention approaches to EID
Nonlocal effects in thin 4H-SiC UV avalanche photodiodes
The avalanche multiplication and excess noise characteristics of 4H-SiC avalanche photodiodes with i-region widths of 0.105 and 0.285 mum have been investigated using 230-365-nm light, while the responsivities of the photodiodes at unity gain were examined for wavelengths up to 375 nm. Peak unity gain responsivities of more than 130 mA/W at 265 nm, equivalent to quantum efficiencies of more than 60%, were obtained for both structures. The measured avalanche characteristics show, that beta > alpha and that the beta/alpha ratio remains large even in thin 4H-SiC avalanche regions. Very low excess noise, corresponding to k(eff) < 0.15 in the local noise model, where k(eff) = alpha/beta(beta/alpha) for hole (electron) injection, was measured with 365-nm light in both structures. Modeling the experimental results using a simple quantum efficiency model and a nonlocal description yields effective ionization threshold energies of 12 and 8 eV for electrons and holes, respectively, and suggests that the dead space in 4H-SiC is soft. Although dead space is important, pure hole injection is still required to ensure low excess noise in thin 4H-SiC APDs owing to beta/alpha ratios that remain large, even at very high fields
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