709 research outputs found
Dark Matter and Collider Phenomenology with two light Supersymmetric Higgs Bosons
Recently, it has been pointed out that two different excesses of events
observed at LEP could be interpreted as the CP-even Higgs bosons of the MSSM
with masses of approximately 98 and 114 GeV. If this is the case, the entire
MSSM Higgs sector is required to be light. In this article, we explore such a
scenario in detail. We constrain the Higgs and supersymmetric spectrum using
physics constraints as well as the magnetic moment of the muon. We then
point out the implications for neutralino dark matter -- next generation direct
detection experiments will be sensitive to all MSSM models with such a Higgs
sector. Finally, we find that all models outside of a very narrow corridor of
the parameter space have a charged Higgs boson which will be observed at the
LHC. In those exceptional models which do not contain an observable charged
Higgs, a light top squark will always be seen at the LHC, and likely at the
Tevatron.Comment: 12 pages, 18 figure
Maximum Significance at the LHC and Higgs Decays to Muons
We present a new way to define and compute the maximum significance
achievable for signal and background processes at the LHC, using all available
phase space information. As an example, we show that a light Higgs boson
produced in weak--boson fusion with a subsequent decay into muons can be
extracted from the backgrounds. The method, aimed at phenomenological studies,
can be incorporated in parton--level event generators and accommodate
parametric descriptions of detector effects for selected observables.Comment: 7 pages, 2 figures, changes to wording and new references, published
versio
Precision Measurements of Higgs Couplings: Implications for New Physics Scales
The measured properties of the recently discovered Higgs boson are in good
agreement with predictions from the Standard Model. However, small deviations
in the Higgs couplings may manifest themselves once the currently large
uncertainties will be improved as part of the LHC program and at a future Higgs
factory. We review typical new physics scenarios that lead to observable
modifications of the Higgs interactions. They can be divided into two broad
categories: mixing effects as in portal models or extended Higgs sectors, and
vertex loop effects from new matter or gauge fields. In each model we relate
coupling deviations to their effective new physics scale. It turns out that
with percent level precision the Higgs couplings will be sensitive to the
multi-TeV regime.Comment: Invited review for Journal of Physics G, 33pp; v2: references added
and improved discussion of operator basis in section 2.
Charged Higgs Boson Pairs at the LHC
We compute the cross section for pair production of charged Higgs bosons at
the LHC and compare the three production mechanisms. The bottom-parton
scattering process is computed to NLO, and the validity of the bottom-parton
approach is established in detail. The light-flavor Drell-Yan cross section is
evaluated at NLO as well. The gluon fusion process through a one-loop amplitude
is then compared with these two results. We show how a complete sample of
events could look, in terms of total cross sections and distributions of the
heavy final states.Comment: 15 pages with 8 figure
The Quartic Higgs Coupling at Hadron Colliders
The quartic Higgs self-coupling is the final measurement in the Higgs
potential needed to fully understand electroweak symmetry breaking. None of the
present or future colliders are known to be able to determine this parameter.
We study the chances of measuring the quartic self-coupling at hadron colliders
in general and at the VLHC in particular. We find the prospects challenging.Comment: 5 pages, 4 figure
Examining the Higgs boson potential at lepton and hadron colliders: a comparative analysis
We investigate inclusive Standard Model Higgs boson pair production at lepton
and hadron colliders for Higgs boson masses in the range 120 GeV < m_H < 200
GeV. For m_H < 140 GeV we find that hadron colliders have a very limited
capability to determine the Higgs boson self-coupling, \lambda, due to an
overwhelming background. We also find that, in this mass range, supersymmetric
Higgs boson pairs may be observable at the LHC, but a measurement of the self
coupling will not be possible. For m_H > 140 GeV we examine ZHH and HH nu
bar-nu production at a future e+e- linear collider with center of mass energy
in the range of sqrt{s}=0.5 - 1 TeV, and find that this is likely to be equally
difficult. Combining our results with those of previous literature, which has
demonstrated the capability of hadron and lepton machines to determine \lambda
in either the high or the low mass regions, we establish a very strong
complementarity of these machines.Comment: Revtex, 25 pages, 2 tables, 10 figure
Detection of the neutral MSSM Higgs bosons in the intense-coupling regime at the LHC
We analyse the prospects to detect at the LHC the neutral Higgs particles of
the Minimal Supersymmetric Standard Model, when the masses of the two CP-even
and of the CP-odd boson are close to one another, and the value of
\tb is large. In this "intense-coupling regime", the Higgs bosons have
strongly enhanced couplings to isospin down-type fermions and large total decay
widths, so that the and decay modes of the three
Higgs bosons are strongly suppressed. We advocate the use of the decays into
muon pairs, , to resolve the three Higgs boson peaks:
although the branching ratios are small, , the resolution on
muons is good enough to allow for their detection, if the mass splitting is
large enough. Using an event generator analysis and a fast detector simulation,
we show that only the process , when at least one
of the -quarks is detected, is viable.Comment: 12 pages, latex, 6 figure
Stop Lepton Associated Production at Hadron Colliders
At hadron colliders, the search for R-parity violating supersymmetry can probe scalar masses beyond what is covered by pair production processes. We evaluate the next-to-leading order SUSY-QCD corrections to the associated stop or sbottom production with a lepton through R-parity violating interactions. We show that higher order corrections render the theoretical predictions more stable with respect to variations of the renormalization and factorization scales and that the total cross section is enhanced by a factor up to 70% at the Tevatron and 50% at the LHC. We investigate in detail how the heavy supersymmetric states decouple from the next-to-leading order process, which gives rise to a theory with an additional scalar leptoquark. In this scenario the inclusion of higher order QCD corrections increases the Tevatron reach on leptoquark masses by up to 40 GeV and the LHC reach by up to 200 GeV
Determining the Higgs Boson Self Coupling at Hadron Colliders
Inclusive Standard Model Higgs boson pair production at hadron colliders has
the capability to determine the Higgs boson self-coupling, lambda. We present a
detailed analysis of the gg\to HH\to (W^+W^-)(W^+W^-)\to
(jjl^\pm\nu)(jj{l'}^\pm\nu) and gg\to HH\to (W^+W^-)(W^+W^-)\to
(jjl^\pm\nu)({l'}^\pm\nu {l''}^\mp\nu) (l, {l'}, {l''}=e, \mu) signal channels,
and the relevant background processes, for the CERN Large Hadron Collider, and
a future Very Large Hadron Collider operating at a center-of-mass energy of 200
TeV. We also derive quantitative sensitivity limits for lambda. We find that it
should be possible at the LHC with design luminosity to establish that the
Standard Model Higgs boson has a non-zero self-coupling and that lambda /
lambda_{SM} can be restricted to a range of 0-3.8 at 95% confidence level (CL)
if its mass is between 150 and 200 GeV. At a 200 TeV collider with an
integrated luminosity of 300 fb^{-1}, lambda can be determined with an accuracy
of 8 - 25% at 95% CL in the same mass range.Comment: 28 pages, Revtex3, 9 figures, 3 table
Production of Charged Higgs Boson Pairs in Gluon-Gluon Collisions
The search for charged Higgs bosons, which are predicted in supersymmetric theories, is difficult at hadron colliders if the mass is large. In this paper we present the theoretical set-up for the production of charged Higgs boson pairs at the LHC in gluon-gluon collisions: . When established experimentally, the trilinear couplings between charged and neutral CP-even Higgs bosons, and , can be measured
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