8,823 research outputs found
SUPERSYMMETRY REACH OF AN UPGRADED TEVATRON COLLIDER
We examine the capability of a TeV Tevatron collider
to discover supersymmetry, given a luminosity upgrade to amass of
data. We compare with the corresponding reach of the Tevatron Main Injector
( of data). Working within the framework of minimal supergravity
with gauge coupling unification and radiative electroweak symmetry breaking, we
first calculate the regions of parameter space accessible via the clean
trilepton signal from \tw_1\tz_2\to 3\ell +\eslt production, with detailed
event generation of both signal and major physics backgrounds. The trilepton
signal can allow equivalent gluino masses of up to GeV to
be probed if is small. If is large, then GeV can
be probed for and large values of , the
rate for \tz_2\to\tz_1\ell\bar{\ell} is suppressed by interference effects,
and there is {\it no} reach in this channel. We also examine regions where the
signal from \tw_1\overline{\tw_1}\to \ell\bar{\ell}+\eslt is detectable.
Although this signal is background limited, it is observable in some regions
where the clean trilepton signal is too small. Finally, the signal
\tw_1\tz_2\to jets+\ell\bar{\ell} +\eslt can confirm the clean trilepton
signal in a substantial subset of the parameter space where the trilepton
signal can be seen. We note that although the clean trilepton signal may allow
Tevatron experiments to identify signals in regions of parameter space beyond
the reach of LEP II, the dilepton channels generally probe much the same region
as LEP II.Comment: 19 page REVTEX file; a uuencoded PS file with PS figures is available
via anonymous ftp at ftp://hep.fsu.edu/preprints/baer/FSUHEP950301.u
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
Probing Slepton Mass Non-Universality at e^+e^- Linear Colliders
There are many models with non-universal soft SUSY breaking sfermion mass
parameters at the grand unification scale. Even in the mSUGRA model scalar mass
unification might occur at a scale closer to M_Planck, and renormalization
effects would cause a mass splitting at M_GUT. We identify an experimentally
measurable quantity Delta that correlates strongly with delta m^2 =
m^2_{selectron_R}(M_GUT) - m^2_{selectron_L}(M_GUT), and which can be measured
at electron-positron colliders provided both selectrons and the chargino are
kinematically accessible. We show that if these sparticle masses can be
measured with a precision of 1% at a 500 GeV linear collider, the resulting
precision in the determination of Delta may allow experiments to distinguish
between scalar mass unification at the GUT scale from the corresponding
unification at Q ~ M_Planck. Experimental determination of Delta would also
provide a distinction between the mSUGRA model and the recently proposed
gaugino-mediation model. Moreover, a measurement of Delta (or a related
quantity Delta') would allow for a direct determination of delta m^2.Comment: 15 pages, RevTeX, 4 postscript figure
Impact of Muon Anomalous Magnetic Moment on Supersymmetric Models
The recent measurement of a_\mu =\frac{g_\mu -2}{2} by the E821 Collaboration
at Brookhaven deviates from the quoted Standard Model (SM) central value
prediction by 2.6\sigma. The difference between SM theory and experiment may be
easily accounted for in a variety of particle physics models employing weak
scale supersymmetry (SUSY). Other supersymmetric models are distinctly
disfavored. We evaluate a_\mu for various supersymmetric models, including
minimal supergravity (mSUGRA), Yukawa unified SO(10) SUSY GUTs, models with
inverted mass hierarchies (IMH), models with non-universal gaugino masses,
gauge mediated SUSY breaking models (GMSB), anomaly-mediated SUSY breaking
models (AMSB) and models with gaugino mediated SUSY breaking (inoMSB). Models
with Yukawa coupling unification or multi-TeV first and second generation
scalars are disfavored by the a_\mu measurement.Comment: 25 page REVTEX file with 10 PS figures. Minor rewording, typos
corrected, references adde
The Reach of the CERN Large Hadron Collider for Gauge-Mediated Supersymmetry Breaking Models
We examine signals for sparticle production at the CERN Large Hadron Collider
(LHC) within the framework of gauge mediated supersymmetry breaking models with
a low SUSY breaking scale for four different model lines, each of which leads
to qualitatively different signatures. We first examine the reach of the LHC
via the canonical E_T^miss and multilepton channels that have been advocated
within the mSUGRA framework. Next, we examine special features of each of these
model lines that could serve to further enhance the SUSY signal over Standard
Model backgrounds. We use ISAJET to evaluate the SUSY reach of experiments at
the LHC. We find that the SUSY reach, measured in terms of m(gluino), is at
least as large, and sometimes larger, than in the mSUGRA framework. In the best
case of the co-NLSP scenario, the reach extends to m(gluino) >~ 3 TeV, assuming
10 fb^-1 of integrated luminosity.Comment: 30 page Revtex file plus 12 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
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
Neutralino dark matter in mSUGRA/CMSSM with a 125 GeV light Higgs scalar
The minimal supergravity (mSUGRA or CMSSM) model is an oft-used framework for
exhibiting the properties of neutralino (WIMP) cold dark matter (CDM). However,
the recent evidence from Atlas and CMS on a light Higgs scalar with mass
m_h\simeq 125 GeV highly constrains the superparticle mass spectrum, which in
turn constrains the neutralino annihilation mechanisms in the early universe.
We find that stau and stop co-annihilation mechanisms -- already highly
stressed by the latest Atlas/CMS results on SUSY searches -- are nearly
eliminated if indeed the light Higgs scalar has mass m_h\simeq 125 GeV.
Furthermore, neutralino annihilation via the A-resonance is essentially ruled
out in mSUGRA so that it is exceedingly difficult to generate
thermally-produced neutralino-only dark matter at the measured abundance. The
remaining possibility lies in the focus-point region which now moves out to
m_0\sim 10-20 TeV range due to the required large trilinear soft SUSY breaking
term A_0. The remaining HB/FP region is more fine-tuned than before owing to
the typically large top squark masses. We present updated direct and indirect
detection rates for neutralino dark matter, and show that ton scale noble
liquid detectors will either discover mixed higgsino CDM or essentially rule
out thermally-produced neutralino-only CDM in the mSUGRA model.Comment: 17 pages including 9 .eps figure
Hidden SUSY at the LHC: the light higgsino-world scenario and the role of a lepton collider
While the SUSY flavor, CP and gravitino problems seem to favor a very heavy
spectrum of matter scalars, fine-tuning in the electroweak sector prefers low
values of superpotential mass \mu. In the limit of low \mu, the two lightest
neutralinos and light chargino are higgsino-like. The light charginos and
neutralinos may have large production cross sections at LHC, but since they are
nearly mass degenerate, there is only small energy release in three-body
sparticle decays. Possible dilepton and trilepton signatures are difficult to
observe after mild cuts due to the very soft p_T spectrum of the final state
isolated leptons. Thus, the higgsino-world scenario can easily elude standard
SUSY searches at the LHC. It should motivate experimental searches to focus on
dimuon and trimuon production at the very lowest p_T(\mu) values possible. If
the neutralino relic abundance is enhanced via non-standard cosmological dark
matter production, then there exist excellent prospects for direct or indirect
detection of higgsino-like WIMPs. While the higgsino-world scenario may easily
hide from LHC SUSY searches, a linear e^+e^- collider or a muon collider
operating in the \sqrt{s}\sim 0.5-1 TeV range would be able to easily access
the chargino and neutralino pair production reactions.Comment: 20 pages including 12 .eps figure
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