4,280 research outputs found
Radiative Decays of the Higgs Boson to a Pair of Fermions
We revisit the radiative decays of the Higgs boson to a fermion pair
where denotes a fermion in the Standard Model
(SM). We include the chirality-flipping diagrams via the Yukawa couplings at
the order , the chirality-conserving contributions
via the top-quark loops of the order , and the
electroweak loops at the order . The QED correction is
about and contributes to the running of fermion
masses at a similar level, which should be taken into account for future
precision Higgs physics. The chirality-conserving electroweak-loop processes
are interesting from the observational point of view. First, the branching
fraction of the radiative decay is about a half of
that of , and that of is more than
four orders of magnitude larger than that of , both of which
reach about . The branching fraction of is
of the order . All the leptonic radiative decays are potentially
observable at the LHC Run 2 or the HL-LHC. The kinematic distributions for the
photon energy or the fermion pair invariant mass provide non-ambiguous
discrimination for the underlying mechanisms of the Higgs radiative decay. We
also study the process and evaluate the observability at
the LHC. We find it comparable to the other related studies and better than the
channel in constraining the charm-Yukawa coupling.Comment: 23 pages, 6 figures, 6 tables; Minor corrections, references updated,
version published in JHE
Architectural dynamics and a suitable public space
Bibliography: leave 167
Dark Matter Blind Spots at One-Loop
We evaluate the impact of one-loop electroweak corrections to the
spin-independent dark matter (DM) scattering cross-section with nucleons
(), in models with a so-called blind spot for direct
detection, where the leading-order prediction for the relevant DM coupling to
the Higgs boson, and therefore , are vanishingly small.
Adopting a simple illustrative scenario in which the DM state results from the
mixing of electroweak singlet and doublet fermions, we compute the relevant
higher order corrections to the scalar effective operator contributions to
, stemming from both triangle and box diagrams involving the
SM and dark sector fields. It is observed that in a significant region of the
singlet-doublet model-space, the one-loop corrections ``unblind'' the
tree-level blind spots and lead to detectable SI scattering rates at future
multi-ton scale liquid Xenon experiments, with reaching
values up to a few times , for a weak scale DM with
Yukawa couplings. Furthermore, we find that there always
exists a new SI blind spot at the next-to-leading order, which is
perturbatively shifted from the leading order one in the singlet-doublet mass
parameters. For comparison, we also present the tree-level spin-dependent
scattering cross-sections near the SI blind-spot region, that could lead to a
larger signal. Our results can be mapped to the blind-spot scenario for
bino-Higgsino DM in the MSSM, with other sfermions, the heavier Higgs boson,
and the wino decoupled.Comment: 20 pages, 5 figures; Minor corrections, references updated, version
published in JHE
WIMPs at High Energy Muon Colliders
The Weakly Interacting Massive Particle (WIMP) paradigm is one of the most
compelling scenarios for particle dark matter (DM). We show in this paper that
a high energy muon collider can make decisive statements about the WIMP DM, and
this should serve as one of its main physics driver cases. We demonstrate this
by employing the DM as the lightest member of an electroweak (EW) multiplet,
which is a simple, yet one of the most challenging WIMP scenarios given its
minimal collider signature and high thermal target mass scale of 1 TeV23
TeV. We perform a first study of the reach of high energy muon colliders,
focusing on the simple, inclusive and conservative signals with large missing
mass, through the mono-photon, VBF di-muon and a novel mono-muon channel. Using
these inclusive signals, it is possible to cover the thermal targets of doublet
and triplet with a 10 TeV muon collider. Higher energies, 14 TeV75 TeV,
would ensure a reach above the thermal targets for the higher EW
multiplets. We also estimate the reach of a search for disappearing tracks,
demonstrating the potential significant enhancement of the sensitivity.Comment: v1: 33 pages, 16 figures, 3 tables; v2: minor updates, matches PRD
published version; v3: doublet disappearing track numerical results
corrected, conclusions improves; also matches PRD errat
Revisiting the Pion Leading-Twist Distribution Amplitude within the QCD Background Field Theory
We study the pion leading-twist distribution amplitude (DA) within the
framework of SVZ sum rules under the background field theory. To improve the
accuracy of the sum rules, we expand both the quark propagator and the vertex
(z\cdot \tensor{D})^n of the correlator up to dimension-six operators in the
background field theory. The sum rules for the pion DA moments are obtained, in
which all condensates up to dimension-six have been taken into consideration.
Using the sum rules, we obtain \left|_{\rm 1\;GeV} = 0.338 \pm
0.032, \left|_{\rm 1\;GeV} = 0.211 \pm 0.030 and
\left|_{\rm 1\;GeV} = 0.163 \pm 0.030. It is shown that the
dimension-six condensates shall provide sizable contributions to the pion DA
moments. We show that the first Gegenbauer moment of the pion leading-twist DA
is , which is consistent with those
obtained in the literature within errors but prefers a larger central value as
indicated by lattice QCD predictions.Comment: 13 pages, 7 figure
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