14,672 research outputs found
Constraining Sommerfeld Enhanced Annihilation Cross-sections of Dark Matter via Direct Searches
In a large class of models we show that the light scalar field responsible
for the Sommerfeld enhancement in the annihilation of dark matter leads to
observable direct detection rates, due to its mixing with the standard model
Higgs. As a result the large annihilation cross-section of dark matter at
present epoch, required to explain the observed cosmic ray anomalies, can be
strongly constrained by direct searches. In particular Sommerfeld boost factors
of order of a few hundred are already out of the CDMS-II upper bound at 90%
confidence level for reasonable values of the model parameters.Comment: 6 pages, 5 figures. v2: discussion on BBN constraints added and BBN
bounds implementend in figure 3, updated references. Version to appear on
Phys.Lett.
Higgs portal, fermionic dark matter, and a Standard Model like Higgs at 125 GeV
We show that fermionic dark matter (DM) which communicates with the Standard
Model (SM) via the Higgs portal is a viable scenario, even if a SM-like Higgs
is found at around 125 GeV. Using effective field theory we show that for DM
with a mass in the range from about 60 GeV to 2 TeV the Higgs portal needs to
be parity violating in order to be in agreement with direct detection searches.
For parity conserving interactions we identify two distinct options that remain
viable: a resonant Higgs portal, and an indirect Higgs portal. We illustrate
both possibilities using a simple renormalizable toy model.Comment: 16 pages, 4 figures; references and discussion of Sommerfeld effect
added; matches published versio
Hunting for Dark Matter Coannihilation by Mixing Dijet Resonances and Missing Transverse Energy
Simplified models of the dark matter (co)annihilation mechanism predict
striking new collider signatures untested by current searches. These models,
which were codified in the coannihilation codex, provide the basis for a dark
matter (DM) discovery program at the Large Hadron Collider (LHC) driven by the
measured DM relic density. In this work, we study an exemplary model featuring
-channel DM coannihilation through a scalar diquark mediator as a
representative case study of scenarios with strongly interacting coannihilation
partners. We discuss the full phenomenology of the model, ranging from low
energy flavor constraints, vacuum stability requirements, and precision Higgs
effects to direct detection and indirect detection prospects. Moreover,
motivated by the relic density calculation, we find significant portions of
parameter space are compatible with current collider constraints and can be
probed by future searches, including a proposed analysis for the novel
signature of a dijet resonance accompanied by missing transverse energy (MET).
Our results show that the TeV LHC with luminosity
should be sensitive to mediators as heavy as 1 TeV and dark matter in the
400--500 GeV range. The combination of searches for single and paired dijet
peaks, non-resonant jets + MET excesses, and our novel resonant dijet + MET
signature have strong coverage of the motivated relic density region,
reflecting the tight connections between particles determining the dark matter
abundance and their experimental signatures at the LHC.Comment: 35 pages, 9 figure
Indirect Searches for Dark Matter: a status review
I review in a schematic way the current status of indirect searches for Dark
Matter: I list the main relevant experimental results of the recent years and I
discuss the excitements and disappointments that their phenomenological
interpretations in terms of almost-standard annihilating Dark Matter have
brought along. I then try to individuate the main directions which have emerged
from the recent very intense model-building activity. In passing, I list the
main sources of uncertainties that affect this kind of searches.Comment: 32 pages, several figures. Extended version of the text for the
Proceedings of Lepton-Photon 2011, Mumbai. Comments and notifications of
inaccuracies, oversights or omissions are welcome (except on ref. [154]). v2:
refs added. v3: updated bounds and added short discussions of gamma-ray line
claims. (v4: just a couple of corrections in refs.) v5: more refs & details
added, updated neutrino bound
Top quark physics in hadron collisions
The top quark is the heaviest elementary particle observed to date. Its large
mass makes the top quark an ideal laboratory to test predictions of
perturbation theory concerning heavy quark production at hadron colliders. The
top quark is also a powerful probe for new phenomena beyond the Standard Model
of particle physics. In addition, the top quark mass is a crucial parameter for
scrutinizing the Standard Model in electroweak precision tests and for
predicting the mass of the yet unobserved Higgs boson. Ten years after the
discovery of the top quark at the Fermilab Tevatron top quark physics has
entered an era where detailed measurements of top quark properties are
undertaken. In this review article an introduction to the phenomenology of top
quark production in hadron collisions is given, the lessons learned in Tevatron
Run I are summarized, and first Run II results are discussed. A brief outlook
to the possibilities of top quark research a the Large Hadron Collider,
currently under construction at CERN, is included.Comment: 84 pages, 32 figures, accepted for publication by Reports on Progress
in Physic
- …