76 research outputs found
A Dark Sector for , and a Diphoton Resonance
We revisit a set of dark sector models, motivated by anomalies observed in
decays and the muon anomalous magnetic moment, in the light of a recently
reported diphoton excess around 750GeV. Interpreting the excess as a scalar
resonance associated with the symmetry breaking sector of a dark gauge group,
we show that a diphoton cross section of few fb can be accomodated, together
with anomalies in and within a minimal dark sector model. The
resulting prominent collider signatures are in the form of wide resonant
signals into top and muon pair final states below TeV. The model
further predicts a dark matter candidate, yet with a significantly
underabundant relic density, unless produced by an appropriate non-thermal
mechanism.Comment: 7 pages, 3 figure
Probing New Physics with Isotope Shift Spectroscopy
We investigate the potential to probe physics beyond the Standard Model with
isotope shift measurements of optical atomic clock transitions. We first derive
the reach for generic new physics above the GeV scale at the effective field
theory level, as well as estimate the limits on possible new spin-independent
forces mediated by sub-GeV states coupled to electrons and neutrons. We also
study the weak force and show that isotope shifts could provide strong
constraints on the couplings to valence quarks, which complement
precision observables at LEP and atomic parity violation experiments. Finally,
motivated by recent experimental hints of a new 750 GeV resonance in diphotons,
we also consider the potential to probe its parity-preserving couplings to
electrons, quarks and gluons with this method. In particular, combining the
diphoton signal with indirect constraints from and isotope shifts in
Ytterbium allows to probe the resonance coupling to electrons with
unprecedented precision.Comment: 6 pages, 2 figures, 2 table
A Dark Matter Relic From Muon Anomalies
We show that the recently reported anomalies in
transitions, as well as the long-standing discrepancy, can be
addressed simultaneously by a new massive abelian gauge boson with loop-induced
coupling to muons. Such a scenario typically leads to a stable dark matter
candidate with a thermal relic density close to the observed value. Dark matter
in our model couples dominantly to leptons, hence signals in direct detection
experiments lie well below the current sensitivity. The LHC, in combination
with indirect detection searches, can test this scenario through distinctive
signatures with muon pairs and missing energy.Comment: 10 pages, 7 figures, 1 tabl
Probing Atomic Higgs-like Forces at the Precision Frontier
We propose a novel approach to probe new fundamental interactions using
isotope shift spectroscopy in atomic clock transitions. As concrete toy example
we focus on the Higgs boson couplings to the building blocks of matter: the
electron and the up and down quarks. We show that the attractive Higgs force
between nuclei and their bound electrons, that is poorly constrained, might
induce effects that are larger than the current experimental sensitivities.
More generically, we discuss how new interactions between the electron and the
neutrons, mediated via light new degrees of freedom, may lead to measurable
non-linearities in a King plot comparison between isotope shifts of two
different transitions. Given state-of-the-art accuracy in frequency comparison,
isotope shifts have the potential of being measured with sub-Hz accuracy, thus
potentially enabling the improvement of current limits on new fundamental
interactions. Candidate atomic system for this measurement require two
different clock transitions and four zero nuclear spin isotopes. We identify
several systems that satisfy this requirement and also briefly discuss existing
measurements. We consider the size of the effect related to the Higgs force and
the requirements for it to produce an observable signal.Comment: 7 pages, added focus on light higgs-like mediators, electron density
at the nucleus improved with effective quantum number, version accepted for
publication in PR
Charming the Higgs
We show that current Higgs data permit a significantly enhanced Higgs
coupling to charm pairs, comparable to the Higgs to bottom pairs coupling in
the Standard Model, without resorting to additional new physics sources in
Higgs production. With a mild level of the latter current data even allow for
the Higgs to charm pairs to be the dominant decay channel. An immediate
consequence of such a large charm coupling is a significant reduction of the
Higgs signal strengths into the known final states as in particular into bottom
pairs. This might reduce the visible vector-boson associated Higgs production
rate to a level that could compromise the prospects of ever observing it. We
however demonstrate that a significant fraction of this reduced signal can be
recovered by jet-flavor-tagging targeted towards charm-flavored jets. Finally
we argue that an enhanced Higgs to charm pairs coupling can be obtained in
various new physics scenarios in the presence of only a mild accidental
cancellation between various contributions.Comment: 8 pages, 3 figure
Higgs Up-Down CP Asymmetry at the LHC
We propose a new observable designed to probe CP-violating coupling of the
Higgs boson to W bosons using associated Higgs production. We define an
asymmetry that measures the number of leptons from W decays relative to the
plane defined by the beam line and the Higgs boson momentum. The orientation of
that plane is determined by the direction of fermions in the initial state, so
that in a proton-proton collider it requires rapidity cuts that preferentially
select quarks over antiquarks.Comment: 7 pages, 3 figure
Up Asymmetries From Exhilarated Composite Flavor Structures
We present a class of warped extra dimension (composite Higgs) models which
conjointly accommodates the t\bar t forward-backward asymmetry observed at the
Tevatron and the direct CP asymmetry in singly Cabibbo suppressed D decays
first reported by the LHCb collaboration. We argue that both asymmetries, if
arising dominantly from new physics beyond the Standard Model, hint for a
flavor paradigm within partial compositeness models in which the right-handed
quarks of the first two generations are not elementary fields but rather
composite objects. We show that this class of models is consistent with current
data on flavor and CP violating physics, electroweak precision observables,
dijet and top pair resonance searches at hadron colliders. These models have
several predictions which will be tested in forthcoming experiments. The CP
asymmetry in D decays is induced through an effective operator of the form
(\bar u c)_{V+A}(\bar s s)_{V+A} at the charm scale, which implies a larger CP
asymmetry in the D^0\to K^+K^- rate relative the D^0\to \pi^+\pi^- channel.
This prediction is distinctive from other Standard Model or dipole-based new
physics interpretation of the LHCb result. CP violation in D-\bar D mixing as
well as an an excess of dijet production of the LHC are also predicted to be
observed in a near future. A large top asymmetry originates from the exchange
of an axial resonance which dominantly produces left-handed top pairs. As a
result a negative contribution to the lepton-based forward-backward asymmetry
in t\bar t production, as well as O(10%) forward-backward asymmetry in b\bar b
production above m_{b\bar b}\simeq 600GeV at the Tevatron is expected.Comment: 35 pages, 7 fig
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