163 research outputs found
The fine-tuning price of the early LHC
LHC already probed and excluded half of the parameter space of the
Constrained Minimal Supersymmetric Standard Model allowed by previous
experiments. Only about 0.3% of the CMSSM parameter space survives. This
fraction rises to about 0.9% if the bound on the Higgs mass can be
circumvented.Comment: 7 pages. v3: updated with new bounds from ATLAS and CMS at 1.1/fb
presented at the EPS-HEP-2011 conferenc
Production of neutral MSSM Higgs bosons in collisions: a complete 1-loop calculation
We present the first complete 1-loop diagrammatic calculation of the cross
sections for the neutral Higgs production processes e^+e^-\ra Z^0h^0 and
e^+e^-\ra A^0h^0 in the minimal supersymmetric standard model. We compare the
results from the diagrammatic calculation with the corresponding ones of the
simpler and compact effective potential approximation and discuss the typical
size of the differences.Comment: LaTeX, 16 pages, 8 figures appended in a uuencoded file, complete
PostScript file available at
http://itpaxp1.physik.uni-karlsruhe.de/prep/KA-TP-16-1995/KA-TP-16-199
Constraints on the Charged Higgs Sector from the Tevatron Collider Data on Top Quark Decay
The top quark data in the lepton plus channel offers a viable probe
for the charged Higgs boson signal. We analyse the recent Tevatron collider
data in this channel to obtain a significant limit on the mass in the
large region.Comment: 8 pages, LaTeX file; 2 figures included (PS files
Self-interactions of the lightest MSSM Higgs boson in the large pseudoscalar-mass limit
We investigate the decoupling properties of the Higgs-sector-induced one-loop
corrections in the lightest Higgs-boson self-couplings, in the framework of the
Minimal Supersymmetric Standard Model (MSSM). The renormalized n-point vertex
functions with external Higgs particles in the MSSM and in the SM are derived
to the one-loop level and compared in the MA >> MZ limit. The computation has
been done in a general R_{xi} gauge and the on-shell renormalization scheme is
chosen. By a comparison of the renormalized lightest Higgs-boson h^0 vertex
functions with respect to the corresponding SM ones, we find that the
differences between the predictions of both models are summarized in the
lightest Higgs-boson mass correction Delta Mh. Consequently, the radiative
corrections are absorbed in the Higgs-boson mass, and the trilinear and quartic
h^0 self-couplings acquire the same structure as the couplings of the SM
Higgs-boson. Therefore, decoupling of the heavy MSSM Higgs bosons occurs and
the MSSM h^0 self-interactions converge to the SM ones in the MA >> MZ limit.Comment: LaTeX, 26 pages, 1 figure. Sections 4 and 5 summarized in one
section. Some references added. Published version in Phys. Rev.
The Higgs Boson Production Cross Section as a Precision Observable?
We investigate what can be learned at a linear collider about the sector of
electroweak symmetry breaking from a precise measurement of the Higgs boson
production cross section through the process e+e- -> hZ. We focus on deviations
from the Standard Model arising in its minimal supersymmetric extension. The
analysis is performed within two realistic future scenarios, taking into
account all prospective experimental errors on supersymmetric particle masses
as well as uncertainties from unknown higher order corrections. We find that
information on tan beta and M_A could be obtained from a cross section
measurement with a precision of 0.5 - 1 %. Alternatively, information could be
obtained on the gaugino mass parameters M_2 and mu if they are relatively
small, M_2, mu approximately 200 GeV.Comment: 13 pages, 3 figures. Discussion on experimental errors enlarged,
references added and updated. Version to appear in Phys. Rev.
The Higgs Mass as the Discriminator of Electroweak Models
In the Minimal Supersymmetric Model (MSSM) and the Next to Minimal
Supersymmetric Model [(M+1)SSM], an upper bound on the lightest higgs mass can
be calculated. On the other hand, vacuum stability implies a lower limit on the
mass of the higgs boson in the Standard Model (SM). We find that a gap exists
for GeV between the SM and both the MSSM and the
(M+1)SSM bounds. Thus, if the new top quark mass measurement by CDF remains
valid, a first measurement of the higgs mass will serve to exclude either the
SM or the MSSM/(M+1)SSM higgs sectors. In addition, we discuss Supersymmetric
Grand Unified Theories, other extentions of the SM, the discovery potential of
the lightest higgs, and the assumptions on which our conclusions are based.Comment: 9 pages, 2 figures, VAND-TH-94-1
Implications of partially degenerate neutrinos at a high scale in the light of KamLAND and WMAP
Electroweak radiative corrections can generate the neutrino (mass)
difference required for the large mixing angle solution (LMA) to the solar
neutrino problem if two of the neutrinos are assumed degenerate at high energy.
We test this possibility with the existing experimental knowledge of the low
energy neutrino mass and mixing parameters. We derive restrictions on ranges of
the high scale mixing matrix elements and obtain predictions for the low energy
parameters required in order to get the LMA solution of the solar neutrino
problem picked out by KamLAND. We find that in the case of standard model this
is achieved only when the (degenerate) neutrino masses lie in the range
(0.7-2) \eV which is at odds with the cosmological limit m_{\nu}<0.23 \eV
(at ) established recently using WMAP results. Thus SM radiative
corrections cannot easily generate the LMA solution in this scenario. However,
the LMA solution is possible in case of the MSSM electroweak corrections with
(almost) degenerate spectrum or with inverted mass hierarchy for limited ranges
in the high scale parameters.Comment: 15 pages, LATEX includes five postscript figure
Search for Heavy Neutral MSSM Higgs Bosons with CMS: Reach and Higgs-Mass Precision
The search for MSSM Higgs bosons will be an important goal at the LHC. We
analyze the search reach of the CMS experiment for the heavy neutral MSSM Higgs
bosons with an integrated luminosity of 30 or 60 fb^-1. This is done by
combining the latest results for the CMS experimental sensitivities based on
full simulation studies with state-of-the-art theoretical predictions of MSSM
Higgs-boson properties. The results are interpreted in MSSM benchmark scenarios
in terms of the parameters tan_beta and the Higgs-boson mass scale, M_A. We
study the dependence of the 5 sigma discovery contours in the M_A-tan_beta
plane on variations of the other supersymmetric parameters. The largest effects
arise from a change in the higgsino mass parameter mu, which enters both via
higher-order radiative corrections and via the kinematics of Higgs decays into
supersymmetric particles. While the variation of can shift the
prospective discovery reach (and correspondingly the ``LHC wedge'' region) by
about Delta tan_beta = 10, we find that the discovery reach is rather stable
with respect to the impact of other supersymmetric parameters. Within the
discovery region we analyze the accuracy with which the masses of the heavy
neutral Higgs bosons can be determined. We find that an accuracy of 1-4% should
be achievable, which could make it possible in favourable regions of the MSSM
parameter space to experimentally resolve the signals of the two heavy MSSM
Higgs bosons at the LHC.Comment: 24 pages, 8 figure
Focus Points and Naturalness in Supersymmetry
We analyze focus points in supersymmetric theories, where a parameter's
renormalization group trajectories meet for a family of ultraviolet boundary
conditions. We show that in a class of models including minimal supergravity,
the up-type Higgs mass has a focus point at the weak scale, where its value is
highly insensitive to the universal scalar mass. As a result, scalar masses as
large as 2 to 3 TeV are consistent with naturalness, and {\em all} squarks,
sleptons and heavy Higgs scalars may be beyond the discovery reaches of the
Large Hadron Collider and proposed linear colliders. Gaugino and Higgsino
masses are, however, still constrained to be near the weak scale. The focus
point behavior is remarkably robust, holding for both moderate and large
\tan\beta, any weak scale gaugino masses and A parameters, variations in the
top quark mass within experimental bounds, and for large variations in the
boundary condition scale.Comment: 30 pages, 17 figure
Low energy supersymmetry with a neutralino LSP and the CDF ee\gamma\gamma + missing E_T event
We present a refined and expanded analysis of the CDF ee\gamma\gamma + \Et
event as superpartner production, assuming the lightest neutralino is the
lightest supersymmetric particle. A general low-energy Lagrangian is
constrained by a minimum cross section times branching ratio into two electrons
and two photons, kinematics consistent with the event, and LEP1-LEP130 data. We
examine how the supersymmetric parameters depend on the kinematics, branching
ratios and experimental predictions with a selectron interpretation of the
event, and discuss to what extent these are modified by other interpretations.
Predictions for imminent CERN LEP upgrades and the present and future Fermilab
Tevatron are presented. Finally, we briefly discuss the possible connection to
other phenomena including a light stop, the neutralino relic density, the shift
in and the associated shift in , and implications for the form
of the theory.Comment: 57 pages, LaTeX, uses epsf.sty, 19 figures. Version accepted for
publication in Phys. Rev. D, with minor changes and a few clarification
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