9,414 research outputs found
Supersymmetry Reach of Tevatron Upgrades: The Large Case
The Yukawa couplings of the tau lepton and the bottom quark become comparable
to, or even exceed, electroweak gauge couplings for large values of the SUSY
parameter . As a result, the lightest tau slepton \ttau_1 and
bottom squark \tb_1 can be significantly lighter than corresponding sleptons
and squarks of the first two generations. Gluino, chargino and neutralino
decays to third generation particles are significantly enhanced when
is large. This affects projections for collider experiment reach
for supersymmetric particles. In this paper, we evaluate the reach of the
Fermilab Tevatron collider for supersymmetric signals in the
framework of the mSUGRA model. We find that the reach via signatures with
multiple isolated leptons ( and ) is considerably reduced. For very
large , the greatest reach is attained in the multi-jet+\eslt
signature. Some significant extra regions may be probed by requiring the
presence of an identified -jet in jets+\eslt events, or by requiring one
of the identified leptons in clean trilepton events to actually be a hadronic 1
or 3 charged prong tau. In an appendix, we present formulae for chargino,
neutralino and gluino three body decays which are valid at large .Comment: 31 page Revtex file including 10 PS figure
Ground-state degeneracies leave recognizable topological scars in the one-particle density
In Kohn-Sham density functional theory (KS-DFT) a fictitious system of
non-interacting particles is constructed having the same ground-state (GS)
density as the physical system of interest. A fundamental open question in DFT
concerns the ability of an exact KS calculation to spot and characterize the GS
degeneracies in the physical system. In this article we provide theoretical
evidence suggesting that the GS density, as a function of position on a 2D
manifold of parameters affecting the external potential, is "topologically
scarred" in a distinct way by degeneracies. These scars are sufficiently
detailed to enable determination of the positions of degeneracies and even the
associated Berry phases. We conclude that an exact KS calculation can spot and
characterize the degeneracies of the physical system
Weighing the universe with accelerators and detectors
Suppose the lightest superpartner (LSP) is observed at colliders, and WIMPs
are detected in explicit experiments. We point out that one cannot immediately
conclude that cold dark matter (CDM) of the universe has been observed, and we
determine what measurements are necessary before such a conclusion is
meaningful. We discuss the analogous situation for neutrinos and axions; in the
axion case we have not found a way to conclude axions are the CDM even if
axions are detected.Comment: 15 pages, 3 figures; minor changes included and typos fixe
Probing Neutralino Resonance Annihilation via Indirect Detection of Dark Matter
The lightest neutralino of R-parity conserving supersymmetric models serves
as a compelling candidate to account for the presence of cold dark matter in
the universe. In the minimal supergravity (mSUGRA) model, a relic density can
be found in accord with recent WMAP data for large values of the parameter
, where neutralino annihilation in the early universe occurs via the
broad s-channel resonance of the pseudoscalar Higgs boson . We map out rates
for indirect detection of neutralinos via 1. detection of neutrinos arising
from neutralino annihilation in the core of the earth or sun and 2. detection
of gamma rays, antiprotons and positrons arising from neutralino annihilation
in the galactic halo. If indeed -resonance annihilation is the main sink for
neutralinos in the early universe, then signals may occur in the gamma ray,
antiproton and positron channels, while a signal in the neutrino channel would
likely be absent. This is in contrast to the hyperbolic branch/focus point
(HB/FP) region where {\it all} indirect detection signals are likely to occur,
and also in contrast to the stau co-annihilation region, where {\it none} of
the indirect signals are likely to occur.Comment: 12 pages including 4 eps figure
Probing Minimal Supergravity at the CERN LHC for Large
For large values of the minimal supergravity model parameter , the
tau lepton and the bottom quark Yukawa couplings become large, leading to
reduced masses of -sleptons and -squarks relative to their first and
second generation counterparts, and to enhanced decays of charginos and
neutralinos to -leptons and -quarks. We evaluate the reach of the CERN
LHC collider for supersymmetry in the mSUGRA model parameter space. We
find that values of GeV can be probed with just 10
fb of integrated luminosity for values as high as 45, so
that mSUGRA cannot escape the scrutiny of LHC experiments by virtue of having a
large value of . We also perform a case study of an mSUGRA model at
where \tz_2\to \tau\ttau_1 and \tw_1\to \ttau_1\nu_\tau
with branching fraction. In this case, at least within our
simplistic study, we show that a di-tau mass edge, which determines the value
of m_{\tz_2}-m_{\tz_1}, can still be reconstructed. This information can be
used as a starting point for reconstructing SUSY cascade decays on an
event-by-event basis, and can provide a strong constraint in determining the
underlying model parameters. Finally, we show that for large there
can be an observable excess of leptons, and argue that signals
might serve to provide new information about the underlying model framework.Comment: 22 page REVTEX file including 8 figure
Mixed Higgsino Dark Matter from a Large SU(2) Gaugino Mass
We observe that in SUSY models with non-universal GUT scale gaugino mass
parameters, raising the GUT scale SU(2) gaugino mass |M_2| from its unified
value results in a smaller value of -m_{H_u}^2 at the weak scale. By the
electroweak symmetry breaking conditions, this implies a reduced value of \mu^2
{\it vis \`a vis} models with gaugino mass unification. The lightest neutralino
can then be mixed Higgsino dark matter with a relic density in agreement with
the measured abundance of cold dark matter (DM). We explore the phenomenology
of this high |M_2| DM model. The spectrum is characterized by a very large wino
mass and a concomitantly large splitting between left- and right- sfermion
masses. In addition, the lighter chargino and three light neutralinos are
relatively light with substantial higgsino components. The higgsino content of
the LSP implies large rates for direct detection of neutralino dark matter, and
enhanced rates for its indirect detection relative to mSUGRA. We find that
experiments at the LHC should be able to discover SUSY over the portion of
parameter space where m_{\tg} \alt 2350-2750 ~GeV, depending on the squark
mass, while a 1 TeV electron-positron collider has a reach comparable to that
of the LHC. The dilepton mass spectrum in multi-jet + \ell^+\ell^- + \eslt
events at the LHC will likely show more than one mass edge, while its shape
should provide indirect evidence for the large higgsino content of the decaying
neutralinos.Comment: 36 pages with 26 eps figure
The Reach of the Fermilab Tevatron and CERN LHC for Gaugino Mediated SUSY Breaking Models
In supersymmetric models with gaugino mediated SUSY breaking (inoMSB), it is
assumed that SUSY breaking on a hidden brane is communicated to the visible
brane via gauge superfields which propagate in the bulk. This leads to GUT
models where the common gaugino mass is the only soft SUSY breaking
term to receive contributions at tree level. To obtain a viable phenomenology,
it is assumed that the gaugino mass is induced at some scale beyond the
GUT scale, and that additional renormalization group running takes place
between and as in a SUSY GUT. We assume an SU(5) SUSY GUT above
the GUT scale, and compute the SUSY particle spectrum expected in models with
inoMSB. We use the Monte Carlo program ISAJET to simulate signals within the
inoMSB model, and compute the SUSY reach including cuts and triggers approriate
to Fermilab Tevatron and CERN LHC experiments. We find no reach for SUSY by the
Tevatron collider in the trilepton channel. %either with or without %identified
tau leptons. At the CERN LHC, values of (1160) GeV can be probed
with 10 (100) fb of integrated luminosity, corresponding to a reach in
terms of of 2150 (2500) GeV. The inoMSB model and mSUGRA can likely
only be differentiated at a linear collider with sufficient energy to
produce sleptons and charginos.Comment: 17 page revtex file with 9 PS figure
Target dark matter detection rates in models with a well-tempered neutralino
In the post-LEP2 era, and in light of recent measurements of the cosmic
abundance of cold dark matter (CDM) in the universe from WMAP, many
supersymmetric models tend to predict 1. an overabundance of CDM and 2.
pessimistically low rates for direct detection of neutralino dark matter.
However, in models with a ``well-tempered neutralino'', where the neutralino
composition is adjusted to give the measured abundance of CDM, the neutralino
is typically of the mixed bino-wino or mixed bino-higgsino state. Along with
the necessary enhancement to neutralino annihilation rates, these models tend
to give elevated direct detection scattering rates compared to predictions from
SUSY models with universal soft breaking terms. We present neutralino direct
detection cross sections from a variety of models containing a well-tempered
neutralino, and find cross section asymptotes with detectable scattering rates.
These asymptotic rates provide targets that various direct CDM detection
experiments should aim for. In contrast, in models where the neutralino mass
rather than its composition is varied to give the WMAP relic density via either
resonance annihilation or co-annihilation, the neutralino remains essentially
bino-like, and direct detection rates may be below the projected reaches of all
proposed experiments.Comment: 13 pages including 1 EPS figur
Reach of the Fermilab Tevatron for minimal supergravity in the region of large scalar masses
The reach of the Fermilab Tevatron for supersymmetric matter has been
calculated in the framework of the minimal supergravity model in the clean
trilepton channel. Previous analyses of this channel were restricted to scalar
masses m_0<= 1 TeV. We extend the analysis to large values of scalar masses
m_0\sim 3.5 TeV. This includes the compelling hyperbolic branch/focus point
(HB/FP) region, where the superpotential \mu parameter becomes small. In this
region, assuming a 5\sigma (3\sigma) signal with 10 (25) fb^{-1} of integrated
luminosity, the Tevatron reach in the trilepton channel extends up to
m_{1/2}\sim 190 (270) GeV independent of \tan\beta . This corresponds to a
reach in terms of the gluino mass of m_{\tg}\sim 575 (750) GeV.Comment: 11 page latex file including 6 EPS figures; several typos corrected
and references adde
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