72 research outputs found
Higgs pair production in vector-boson fusion at the LHC and beyond
The production of pairs of Higgs bosons at hadron colliders provides unique
information on the Higgs sector and on the mechanism underlying electroweak
symmetry breaking (EWSB). Most studies have concentrated on the gluon fusion
production mode which has the largest cross section. However, despite its small
production rate, the vector-boson fusion channel can also be relevant since
even small modifications of the Higgs couplings to vector bosons induce a
striking increase of the cross section as a function of the invariant mass of
the Higgs boson pair. In this work, we exploit this unique signature to propose
a strategy to extract the quartic coupling and provide model-independent
constraints on theories where EWSB is driven by new strong interactions. We
take advantage of the higher signal yield of the final state
and make extensive use of jet substructure techniques to reconstruct signal
events with a boosted topology, characteristic of large partonic energies,
where each Higgs boson decays to a single collimated jet . Our results
demonstrate that the coupling can be measured with 45% (20%) precision
at the LHC for 300 (3000) fb, while a 1% precision can be
achieved at a 100 TeV collider.Comment: Updated to match published version in EPJC and fixed typo in Tab. 10
(column labels a & b were swapped
From quarks to nucleons in dark matter direct detection
We provide expressions for the nonperturbative matching of the effective
field theory describing dark matter interactions with quarks and gluons to the
effective theory of nonrelativistic dark matter interacting with
nonrelativistic nucleons. We give the leading and subleading order expressions
in chiral counting. In general, a single partonic operator already matches onto
several nonrelativistic operators at leading order in chiral counting. Thus,
keeping only one operator at the time in the nonrelativistic effective theory
does not properly describe the scattering in direct detection. Moreover, the
matching of the axial--axial partonic level operator, as well as the matching
of the operators coupling DM to the QCD anomaly term, naively include momentum
suppressed terms. However, these are still of leading chiral order due to pion
poles and can be numerically important. We illustrate the impact of these
effects with several examples.Comment: 47 pages, 8 figures. Improved discussion, corrected typographical
errors, updated reference
Complementary constraints on couplings at the LHC
We propose a new strategy to probe the boson couplings to bottom and
charm quarks at the LHC. In this work we mainly focus on the case of bottom
quarks. Here, the boson is produced in association with two -jets and
decays to electrons or muons. In this final state, tagging the charge of the
-jets allows us to measure the charge asymmetry and thus to directly probe
the couplings. The leptonic final state not only allows us to
cleanly reconstruct the boson but also to mitigate the otherwise
overwhelming backgrounds. Furthermore, while LEP could only scan a limited
range of dilepton invariant masses, there is no such limitation at the LHC.
Consequently, this allows us to make full use of the interference between the
amplitudes mediated by a boson and a photon. Using the full high-luminosity
LHC dataset of and with the current flavor and
charge-tagging capabilities would allow us to reject the wrong-sign
right-handed coupling solution by 4. Further improving the
charge-tagging efficiency would disfavor it by 6.Comment: 18 + 8 pages, 9 figure
DirectDM: a tool for dark matter direct detection
We provide a Mathematica package, DirectDM, that takes as input the Wilson
coefficients of the relativistic effective theory describing the interactions
of dark matter with quarks, gluons and photons, and matches it onto an
effective theory describing the interactions of dark matter with neutrons and
protons. The nonperturbative matching is performed at leading order in a chiral
expansion. The one-loop QCD and QED renormalization-group evolution from the
electroweak scale down to the hadronic scale, as well as finite corrections at
the heavy quark thresholds are taken into account. We also provide an interface
with the package DMFormFactor so that, starting from the relativistic effective
theory, one can directly obtain the event rates for direct detection
experiments.Comment: 19 pages, 2 figures; the companion code can be downloaded from
https://directdm.github.i
Renormalization Group Effects in Dark Matter Interactions
We present a renormalization-group (RG) analysis of dark matter interactions
with the standard model, where dark matter is allowed to be a component of an
electroweak multiplet, and has a mass at or below the electroweak scale. We
consider, in addition to the gauge interactions, the complete set of effective
operators for dark matter interactions with the standard model above the weak
scale, up to and including mass dimension six. We calculate the RG evolution of
these operators from the high scale Lambda down to the weak scale, and perform
the matching to the tower of effective theories below the weak scale. We also
summarize the RG evolution below the weak scale and the matching to the
nonrelativistic nuclear interactions. We present several numerical examples and
show that in certain cases the dark matter - nucleus scattering rate can change
by orders of magnitude when the electroweak running is included.Comment: 62 pages, 16 figures. Updated references; version published in JHE
Chiral Effective Theory of Dark Matter Direct Detection
We present the effective field theory for dark matter interactions with the
visible sector that is valid at scales of O(1 GeV). Starting with an effective
theory describing the interactions of fermionic and scalar dark matter with
quarks, gluons and photons via higher dimension operators that would arise from
dimension-five and dimension-six operators above electroweak scale, we perform
a nonperturbative matching onto a heavy baryon chiral perturbation theory that
describes dark matter interactions with light mesons and nucleons. This is then
used to obtain the coefficients of the nuclear response functions using a
chiral effective theory description of nuclear forces. Our results consistently
keep the leading contributions in chiral counting for each of the initial
Wilson coefficients.Comment: 64 pages, 3 figures, 2 tables. Fixed typographical error
Nonstandard Yukawa Couplings and Higgs Portal Dark Matter
We study the implications of non-standard Higgs Yukawa couplings to light
quarks on Higgs-portal dark matter phenomenology. Saturating the present
experimental bounds on up-quark, down-quark, or strange-quark Yukawa couplings,
the predicted direct dark matter detection scattering rate can increase by up
to four orders of magnitude. The effect on the dark matter annihilation cross
section, on the other hand, is subleading unless the dark matter is very light
-- a scenario that is already excluded by measurements of the Higgs invisible
decay width. We investigate the expected size of corrections in
multi-Higgs-doublet models with natural flavor conservation, the type-II
two-Higgs-doublet model, the Giudice-Lebedev model of light quark masses,
minimal flavor violation new physics models, Randall-Sundrum, and composite
Higgs models. We find that an enhancement in the dark matter scattering rate of
an order of magnitude is possible. Finally, we point out that a discovery of
Higgs-portal dark matter could lead to interesting bounds on the light-quark
Yukawa couplings.Comment: 38 pages, 12 figures; minor mistake in numerics fixed, conclusions
unchanged; references adde
Higgs Assisted Q-balls from Pseudo-Nambu-Goldstone Bosons
Motivated by recent constructions of TeV-scale strongly-coupled dynamics,
either associated with the Higgs sector itself as in pseudo-Nambu-Goldstone
boson (pNGB) Higgs models or in theories of asymmetric dark matter, we show
that stable solitonic Q- balls can be formed from light pion-like pNGB fields
carrying a conserved global quantum number in the presence of the Higgs field.
We focus on the case of thick-wall Q-balls, where solutions satisfying all
constraints are shown to exist over a range of parameter values. In the limit
that our approximations hold, the Q-balls are weakly bound and parametrically
large, and the form of the interactions of the light physical Higgs with the
Q-ball is determined by the breaking of scale symmetry.Comment: 24 pages, 6 figures, 1 tabl
Constraining Light-Quark Yukawa Couplings from Higgs Distributions
We propose a novel strategy to constrain the bottom and charm Yukawa
couplings by exploiting LHC measurements of transverse momentum distributions
in Higgs production. Our method does not rely on the reconstruction of
exclusive final states or heavy-flavour tagging. Compared to other proposals it
leads to an enhanced sensitivity to the Yukawa couplings due to distortions of
the differential Higgs spectra from emissions which either probe quark loops or
are associated to quark-initiated production. We derive constraints using data
from LHC Run I, and we explore the prospects of our method at future LHC runs.
Finally, we comment on the possibility of bounding the strange Yukawa coupling.Comment: Added analysis of the Higgs transverse momentum distribution. Version
published in Physical Review Letter
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