24,464 research outputs found
Flavor and Collider Signatures of Asymmetric Dark Matter
We consider flavor constraints on, and collider signatures of, Asymmetric
Dark Matter (ADM) via higher dimension operators. In the supersymmetric models
we consider, R-parity violating (RPV) operators carrying B-L interact with n
dark matter (DM) particles X through an interaction of the form W = X^n
O_{B-L}, where O_{B-L} = q l d^c, u^c d^c d^c, l l e^c. This interaction
ensures that the lightest ordinary supersymmetric particle (LOSP) is unstable
to decay into the X sector, leading to a higher multiplicity of final state
particles and reduced missing energy at a collider. Flavor-violating processes
place constraints on the scale of the higher dimension operator, impacting
whether the LOSP decays promptly. While the strongest limitations on RPV from
n-\bar{n} oscillations and proton decay do not apply to ADM, we analyze the
constraints from meson mixing, mu-e conversion, mu -> 3 e and b -> s l^+ l^-.
We show that these flavor constraints, even in the absence of flavor
symmetries, allow parameter space for prompt decay to the X sector, with
additional jets and leptons in exotic flavor combinations. We study the
constraints from existing 8 TeV LHC SUSY searches with (i) 2-6 jets plus
missing energy, and (ii) 1-2 leptons, 3-6 jets plus missing energy, comparing
the constraints on ADM-extended supersymmetry with the usual supersymmetric
simplified models.Comment: 63 pages, 26 figures, 10 tables, revtex
Flexible Resolution of Authorisation Conflicts in Distributed Systems
Flexible Resolution of Authorisation Conflicts in Distributed System
On Models of New Physics for the Tevatron Top A_FB
CDF has observed a top forward-backward asymmetry discrepant with the
Standard Model prediction at 3.4 \sigma. We analyze models that could generate
the asymmetry, including flavor-violating W's, horizontal Z'_Hs, triplet and
sextet diquarks, and axigluons. We consider the detailed predictions of these
models for the invariant mass and rapidity distributions of the asymmetry at
the parton level, comparing against the unfolded parton-level CDF results.
While all models can reproduce the asymmetry with the appropriate choice of
mass and couplings, it appears at first examination that the extracted
parton-level invariant mass distribution for all models are in conflict with
Tevatron observations. We show on closer examination, however, that t tbar
events in Z'_H and W' models have considerably lower selection efficiencies in
high invariant mass bins as compared to the Standard Model, so that W', Z'_H,
and axigluon models can generate the observed asymmetry while being consistent
with the total cross-section and invariant mass spectrum. Triplet and sextet
models have greater difficulty producing the observed asymmetry while remaining
consistent with the total cross-section and invariant mass distribution. To
more directly match the models and the CDF results, we proceed to decay and
reconstruct the tops, comparing our results against the "raw" CDF asymmetry and
invariant mass distributions. We find that the models that successfully
generate the corrected CDF asymmetry at the parton level reproduce very well
the more finely binned uncorrected asymmetry. Finally, we discuss the early LHC
reach for discovery of these models, based on our previous analysis
[arXiv:1102.0018].Comment: 29 pages, 14 figures, 2 table
Two Conditions for Galaxy Quenching: Compact Centres and Massive Haloes
We investigate the roles of two classes of quenching mechanisms for central
and satellite galaxies in the SDSS (): those involving the halo and
those involving the formation of a compact centre. For central galaxies with
inner compactness ,
the quenched fraction is strongly correlated with
with only weak halo mass dependence. However, at higher and lower
, sSFR is a strong function of and mostly
independent of . In other words, divides galaxies into those with high sSFR
below and low sSFR above this range. In both the upper and lower regimes,
increasing shifts the entire sSFR distribtuion to lower sSFR
without a qualitative change in shape. This is true even at fixed , but
varying at fixed adds no quenching information. Most of the
quenched centrals with are dense (), suggesting compaction-related
quenching maintained by halo-related quenching. However, 21% are diffuse,
indicating only halo quenching. For satellite galaxies in the outskirts of
halos, quenching is a strong function of compactness and a weak function of
host . In the inner halo, dominates quenching, with
of the satellites being quenched once . This regional effect is greatest for the least massive
satellites. As demonstrated via semi-analytic modelling with simple
prescriptions for quenching, the observed correlations can be explained if
quenching due to central compactness is rapid while quenching due to halo mass
is slow.Comment: 16 pages, 11 figures, MNRAS accepte
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