18 research outputs found
Upper and Lower Limits on Neutralino WIMP Mass and Spin--Independent Scattering Cross Section, and Impact of New (g-2)_{mu} Measurement
We derive the allowed ranges of the spin--independent interaction cross
section \sigsip for the elastic scattering of neutralinos on proton for wide
ranges of parameters of the general Minimal Supersymmetric Standard Model. We
investigate the effects of the lower limits on Higgs and superpartner masses
from colliders, as well as the impact of constraints from \bsgamma and the
new measurement of \gmtwo on the upper and lower limits on \sigsip. We
further explore the impact of the neutralino relic density, including
coannihilation, and of theoretical assumptions about the largest allowed values
of the supersymmetric parameters. For , requiring the latter to lie
below 1\tev leads to \sigsip\gsim 10^{-11}\pb at \mchi\sim100\gev and
\sigsip\gsim 10^{-8}\pb at \mchi\sim1\tev. When the supersymmetric
parameters are allowed above 1\tev, for 440\gev \lsim \mchi\lsim 1020 \gev
we derive a {\em parameter--independent lower limit} of \sigsip \gsim 2\times
10^{-12}\pb. (No similar lower limits can be set for nor for
1020\gev\lsim\mchi\lsim2.6\tev.) Requiring \abundchi<0.3 implies a {\em
parameter--independent upper limit} \mchi\lsim2.6\tev. The new \epem--based
measurement of restricts \mchi\lsim 350\gev at CL
and \mchi\lsim515\gev at CL, and implies . The largest
allowed values of \sigsip have already become accessible to recent
experimental searches.Comment: LaTeX, 17 pages, 9 eps figures. Version to appear in JHE
Particle Dark Matter - A Theorist's Perspective
Dark matter is presumably made of some new, exotic particle that appears in
extensions of the Standard Model. After giving a brief overview of some popular
candidates, I discuss in more detail the most appealing case of the
supersymmetric neutralino.Comment: Invited talk at PASCOS--03, Mumbai, Indi
Gravitino Dark Matter in the CMSSM and Implications for Leptogenesis and the LHC
In the framework of the CMSSM we study the gravitino as the lightest
supersymmetric particle and the dominant component of cold dark matter in the
Universe. We include both a thermal contribution to its relic abundance from
scatterings in the plasma and a non--thermal one from neutralino or stau decays
after freeze--out. In general both contributions can be important, although in
different regions of the parameter space. We further include constraints from
BBN on electromagnetic and hadronic showers, from the CMB blackbody spectrum
and from collider and non--collider SUSY searches. The region where the
neutralino is the next--to--lightest superpartner is severely constrained by a
conservative bound from excessive electromagnetic showers and probably
basically excluded by the bound from hadronic showers, while the stau case
remains mostly allowed. In both regions the constraint from CMB is often
important or even dominant. In the stau case, for the assumed reasonable ranges
of soft SUSY breaking parameters, we find regions where the gravitino abundance
is in agreement with the range inferred from CMB studies, provided that, in
many cases, a reheating temperature \treh is large, \treh\sim10^{9}\gev. On
the other side, we find an upper bound \treh\lsim 5\times 10^{9}\gev. Less
conservative bounds from BBN or an improvement in measuring the CMB spectrum
would provide a dramatic squeeze on the whole scenario, in particular it would
strongly disfavor the largest values of \treh\sim 10^{9}\gev. The regions
favored by the gravitino dark matter scenario are very different from standard
regions corresponding to the neutralino dark matter, and will be partly probed
at the LHC.Comment: JHEP version, several improvements and update
Direct versus indirect detection in mSUGRA with self-consistent halo models
We perform a detailed analysis of the detection prospects of neutralino dark
matter in the mSUGRA framework. We focus on models with a thermal relic
density, estimated with high accuracy using the DarkSUSY package, in the range
favored by current precision cosmological measurements. Direct and indirect
detection rates are computed implementing two models for the dark matter halo,
tracing opposite regimes for the phase of baryon infall, with fully consistent
density profiles and velocity distribution functions. This has allowed, for the
first time, a fully consistent comparison between direct and indirect detection
prospects. We discuss all relevant regimes in the mSUGRA parameter space,
underlining relevant effects, and providing the basis for extending the
discussion to alternative frameworks. In general, we find that direct detection
and searches for antideuterons in the cosmic rays seems to be the most
promising ways to search for neutralinos in these scenarios.Comment: 26 pages, 9 figure
Prospects for dark matter detection with IceCube in the context of the CMSSM
We study in detail the ability of the nominal configuration of the IceCube
neutrino telescope (with 80 strings) to probe the parameter space of the
Constrained MSSM (CMSSM) favoured by current collider and cosmological data.
Adopting conservative assumptions about the galactic halo model and the
expected experiment performance, we find that IceCube has a probability between
2% and 12% of achieving a 5sigma detection of dark matter annihilation in the
Sun, depending on the choice of priors for the scalar and gaugino masses and on
the astrophysical assumptions. We identify the most important annihilation
channels in the CMSSM parameter space favoured by current constraints, and we
demonstrate that assuming that the signal is dominated by a single annihilation
channel canlead to large systematic errors in the inferred WIMP annihilation
cross section. We demonstrate that ~ 66% of the CMSSM parameter space violates
the equilibrium condition between capture and annihilation in the center of the
Sun. By cross-correlating our predictions with direct detection methods, we
conclude that if IceCube does detect a neutrino flux from the Sun at high
significance while direct detection experiments do not find a signal above a
spin-independent cross section sigma_SI^p larger than 5x10^{-9} pb, the CMSSM
will be strongly disfavoured, given standard astrophysical assumptions for the
WIMP distribution. This result is robust with respect to a change of priors. We
argue that the proposed low-energy DeepCore extension of IceCube will be an
ideal instrument to focus on relevant CMSSM areas of parameter space.Comment: 32 pages, 12 figures. Updated discussion of comparison with direct
detection. References added. Main results unchanged. Matches version accepted
by JCA
A Markov chain Monte Carlo analysis of the CMSSM
We perform a comprehensive exploration of the Constrained MSSM parameter space employing a Markov Chain Monte Carlo technique and a Bayesian analysis. We compute superpartner masses and other collider observables, as well as a cold dark matter abundance, and compare them with experimental data. We include uncertainties arising from theoretical approximations as well as from residual experimental errors of relevant Standard Model parameters. We delineate probability distributions of the CMSSM parameters, the collider and cosmological observables as well as a dark matter direct detection cross section. The 68% probability intervals of the CMSSM parameters are: 0.52 TeV < m1/2 < 1.26 TeV, m0 < 2.10 TeV, -0.34 TeV < A0 < 2.41 TeV and 38.5 < tan \u3b2 < 54.6. Generally, large fractions of high probability ranges of the superpartner masses will be probed at the LHC. For example, we find that the probability of mg < 2.7TeV is 78%, of mqR < 2.5TeV is 85% and of m\u3c7\ub11 < 0.8TeV is 65%. As regards the other observables, for example at 68% probability we find 3.5
710-9 < BR(Bs \u2192 \u3bc+\u3bc-) < 1.7
710-8, 1.9
710-10 < \u3b4a SUSY \u3bc < 9.9
710-10 and 1
7 10 -10 pb < \u3c3SIp < 1
7 10 -8 pb for direct WIMP detection. We highlight a complementarity between LHC and WIMP dark matter searches in exploring the CMSSM parameter space. We further expose a number of correlations among the observables, in particular between BR(Bs \u2192 \u3bc+\u3bc-) and BR(B \u2192 X s\u3b3) or \u3c3SIp. Once SUSY is discovered, this and other correlations may prove helpful in distinguishing the CMSSM from other supersymmetric models. We investigate the robustness of our results in terms of the assumed ranges of CMSSM parameters and the effect of the (g - 2)\u3bc anomaly which shows some tension with the other observables. We find that the results for m0, and the observables which strongly depend on it, are sensitive to our assumptions, while our conclusions for the other variables are robust
Dark Matter And With Minimal Soft SUSY Breaking
CMSSM boundary conditions are usually used when calculating cosmological dark
matter densities. In this paper we calculate the cosmological density of dark
matter in the MSSM using minimal soft SUSY breaking boundary
conditions. These boundary conditions incorporate several attractive features:
they are consistent with Yukawa unification, they result in a
"natural" inverted scalar mass hierarchy and they reduce the dimension 5
operator contribution to the proton decay rate. With regards to dark matter, on
the other hand, this is to a large extent an unexplored territory with large
squark and slepton masses , large and small . We find that in most regions of parameter space the cosmological density of
dark matter is considerably less than required by the data. However there is a
well--defined, narrow region of parameter space which provides the observed
relic density of dark matter, as well as a good fit to precision electroweak
data, including top, bottom and tau masses, and acceptable bounds on the
branching fraction of . We present predictions for Higgs
and SUSY spectra, the dark matter detection cross section and the branching
ratio in this region of parameter space.Comment: 15 pages, 5 figure
Implications for the Constrained MSSM from a new prediction for b to s gamma
We re-examine the properties of the Constrained MSSM in light of updated
constraints, paying particular attention to the impact of the recent
substantial shift in the Standard Model prediction for BR(B to X_s gamma). With
the help of a Markov Chain Monte Carlo scanning technique, we vary all relevant
parameters simultaneously and derive Bayesian posterior probability maps. We
find that the case of \mu>0 remains favored, and that for \mu<0 it is
considerably more difficult to find a good global fit to current constraints.
In both cases we find a strong preference for a focus point region. This leads
to improved prospects for detecting neutralino dark matter in direct searches,
while superpartner searches at the LHC become more problematic, especially when
\mu<0. In contrast, prospects for exploring the whole mass range of the
lightest Higgs boson at the Tevatron and the LHC remain very good, which
should, along with dark matter searches, allow one to gain access to the
otherwise experimentally challenging focus point region. An alternative measure
of the mean quality-of-fit which we also employ implies that present data are
not yet constraining enough to draw more definite conclusions. We also comment
on the dependence of our results on the choice of priors and on some other
assumptions.Comment: JHEP versio
Dark Matter And With Minimal Soft SUSY Breaking II
We update and extend to larger masses our previous analysis of the MSSM with
minimal [MSOSM] soft SUSY breaking boundary conditions. We
find a well--defined, narrow region of parameter space which provides the
observed relic density of dark matter, in a domain selected to fit precision
electroweak data, including top, bottom and tau masses. The model is highly
constrained which allows us to make several predictions. We find the light
Higgs mass GeV and also upper bounds on the mass of the
gluino \mgluino\lsim3.1 TeV and lightest neutralino \mchi\lsim450 GeV. As
the CP odd Higgs mass increases, the region of parameter space consistent
with WMAP data is forced to larger values of and smaller values of
. Hence, we find an upper bound m_A \lsim 1.3 TeV. This in turn leads to
lower bounds on (assuming minimal
flavor violation) and on the dark matter spin independent detection cross
section \sigsip > 10^{-9} pb. Finally, we extend our previous analysis to
include WIMP signals in indirect detection and find prospects for WIMP
detection generally much less promising than in direct WIMP searches.Comment: 24 page
Large Beyond-Leading-Order Effects in b -> s gamma in Supersymmetry with General Flavor Mixing
We examine squark--gluino loop effects on the process in
minimal supersymmetry with general flavor mixing in the squark sector. In the
regime of heavy squarks and gluino, we derive analytic expressions for the
beyond--LO corrections to the Wilson coefficients and find them to be often
large, especially at large and . The ensuing ranges of
values of the Wilson coefficients are typically smaller than in the LO
approximation, and sometimes even change sign. This has the effect of often
reducing, relative to the LO, the magnitude of supersymmetric contributions to
. This ``focusing effect'' is caused by contributions
from: (i) an RG evolution of the Wilson coefficients; (ii) a correction to the
LO chargino contribution to the Wilson coefficients, which can considerably
reduce the LO gluino contribution. This partial cancellation of the two
contributions takes place only in the case of general flavor mixing. As a
result, stringent lower bounds on the mass scale of superpartners, which apply
in the case of minimal flavor violation, can be substantially reduced for even
small departures from the scenario. The often disfavored case of can
also become allowed for as small as 200 GeV, compared to >
500 GeV at LO and over 2 TeV in the case of minimal flavor violation.
Limits on the allowed amount of flavor mixing among the 2nd and 3rd generation
down--type squarks are also typically considerably weakened. The input CKM
matrix element can be larger than the experimental value by a
factor of ten, or can be as small as zero.Comment: 46 page, 36 figures. v2: some clarifications and Ref.[5] added.
Version to appear in JHE