12,933 research outputs found
Higgs boson search significance deformations due to mixed-in scalars
The existence of exotic scalars that mix with the Standard Model (SM) Higgs
boson can affect Higgs boson phenomenology in a multitude of ways. We consider
two light Higgs bosons with shared couplings to SM fields and with masses close
to each other, in the range where the h \to WW \to l \nu l \nu is an important
search channel. In this channel, we do not find the dilution of significance of
the `SM-like' Higgs boson that is naively expected because of the mixing. This
is because of leakage of events from the decay of the other scalar into its
signal region. Nevertheless, we show that the broadening of the h\to WW \to l
\nu l \nu significance plots of Standard Model Higgs boson searches could
indicate the first evidence of the the extra scalar state.Comment: 6 pages, 6 figures; v2: all plots now made with the lighter Higgs
mass equal to 125 GeV and other minor corrections made, to be published in
Physics Letters
How well do we need to measure Higgs boson couplings?
Most of the discussion regarding the Higgs boson couplings to Standard Model
vector bosons and fermions is presented with respect to what present and future
collider detectors will be able to measure. Here, we ask the more physics-based
question of how well do we need to measure the Higgs boson couplings? We first
present a reasonable definition of "need" and then investigate the answer in
the context of various highly motivated new physics scenarios: supersymmetry,
mixed-in hidden sector Higgs bosons, and a composite Higgs boson. We find the
largest coupling deviations away from the SM Higgs couplings that are possible
if no other state related to EWSB is directly accessible at the LHC. Depending
on the physics scenario under consideration, we find targets that range from
less than 1% to 10% for vector bosons, and from a few percent to tens of
percent for couplings to fermions.Comment: 9 pages, 10 figures; v3: minor corrections, to be published in
Physical Review
How well do we need to measure the Higgs boson mass and self-coupling?
Much of the discussion regarding future measurements of the Higgs boson mass
and self-coupling is focussed on how well various collider options can do. In
this article we ask a physics-based question of how well do we need colliders
to measure these quantities to have an impact on discovery of new physics or an
impact in how we understand the role of the Higgs boson in nature. We address
the question within the framework of the Standard Model and various beyond the
Standard Model scenarios, including supersymmetry and theories of composite
Higgs bosons. We conclude that the LHC's stated ability to measure the Higgs
boson to better than 150 MeV will be as good as we will ever need to know the
Higgs boson mass in the foreseeable future. On the other hand, we estimate that
the self-coupling will likely need to be measured to better than 20 percent to
see a deviation from the Standard Model expectation. This is a challenging
target for future collider and upgrade scenarios.Comment: 20 pages, 4 figure
Mapping systemic risk: critical degree and failures distribution in financial networks
The 2008 financial crisis illustrated the need for a thorough, functional
understanding of systemic risk in strongly interconnected financial structures.
Dynamic processes on complex networks being intrinsically difficult, most
recent studies of this problem have relied on numerical simulations. Here we
report analytical results in a network model of interbank lending based on
directly relevant financial parameters, such as interest rates and leverage
ratios. Using a mean-field approach, we obtain a closed-form formula for the
"critical degree", viz. the number of creditors per bank below which an
individual shock can propagate throughout the network. We relate the failures
distribution (probability that a single shock induces failures) to the
degree distribution (probability that a bank has creditors), showing in
particular that the former is fat-tailed whenever the latter is. Our criterion
for the onset of contagion turns out to be isomorphic to the condition for
cooperation to evolve on graphs and social networks, as recently formulated in
evolutionary game theory. This remarkable connection supports recent calls for
a methodological rapprochement between finance and ecology.Comment: 19 pages, 4 figure
Bc spectroscopy in a quantum-chromodynamic potential model
We have investigated spectroscopy with the use of a
quantum-chromodynamic potential model which was recently used by us for the
light-heavy quarkonia. We give our predictions for the energy levels and the
1 transition widths. We also find, rather surprisingly, that although
is not a light-heavy system, the heavy quark effective theory with the
inclusion of the and corrections is as successful
for as it is for and .Comment: 10 page ReVTeX pape
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