[Show abstract][Hide abstract] ABSTRACT: LHC-7 has narrowed down the mass range of the light Higgs boson. This result
is consistent with the supergravity unification framework, and the current
Higgs boson mass window implies a rather significant loop correction to the
tree value pointing to a relatively heavy scalar sparticle spectrum with
universal boundary conditions. It is shown that the largest value of the Higgs
boson mass is obtained on the Hyperbolic Branch of radiative breaking. The
implications of light Higgs boson in the broader mass range of 115 GeV to 131
GeV and a narrower range of 123 GeV to 127 GeV are explored in the context of
the discovery of supersymmetry at LHC-7 and for the observation of dark matter
in direct detection experiments.
Physical Review D 04/2012; 85(7):075001. DOI:10.1103/PhysRevD.85.075001 · 4.86 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The recent excess observed by CDF in Bs0→μ+μ- is interpreted in terms of a possible supersymmetric origin. An analysis is given of the parameter space of mSUGRA and nonuniversal SUGRA under the combined constraints from LHC-7 with 1.04 fb-1 of integrated luminosity, under the new XENON-100 limits on the neutralino-proton spin-independent cross section and under the CDF Bs0→μ+μ- 90% C.L. limit reported to arise from an excess number of dimuon events. It is found that the predicted value of the branching ratio Bs0→μ+μ- for mSUGRA parameter points consistent with all constraints contains the following set of next to lightest particles beyond the standard model: chargino, stau, stop or CP odd (even) Higgs. The lower bounds of sparticles, including those from the LHC, XENON and CDF Bs0→μ+μ- constraint, are exhibited and the shift in the allowed range of sparticle masses arising solely due to the extra constraint from the CDF result is given. It is pointed out that the two-sided CDF 90% C.L. limit puts upper bounds on sparticle masses. An analysis of possible signatures for early discovery at the LHC is carried out corresponding to the signal region in Bs0→μ+μ-. Implications of GUT-scale nonuniversalities in the gaugino and Higgs sectors are discussed.
Physical Review D 12/2011; 84(11):115011. DOI:10.1103/PhysRevD.84.115011 · 4.86 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We investigate the connection between the conservation of R-parity in
supersymmetry and the Stueckelberg mechanism for the mass generation of the B-L
vector gauge boson. It is shown that with universal boundary conditions for
soft terms of sfermions in each family at the high scale and with the
Stueckelberg mechanism for generating mass for the B-L gauge boson present in
the theory, electric charge conservation guarantees the conservation of
R-parity in the minimal B-L extended supersymmetric standard model. We also
discuss non-minimal extensions. This includes extensions where the gauge
symmetries arise with an additional U(1)_{B-L} x U(1)_X, where U(1)_X is a
hidden sector gauge group. In this case the presence of the additional U(1)_X
allows for a Z' gauge boson mass with B-L interactions to lie in the sub-TeV
region overcoming the multi-TeV LEP constraints. The possible tests of the
models at colliders and in dark matter experiments are analyzed including
signals of a low mass Z' resonance and the production of spin zero bosons and
their decays into two photons. In this model two types of dark matter
candidates emerge which are Majorana and Dirac particles. Predictions are made
for a possible simultaneous observation of new physics events in dark matter
experiments and at the LHC.
Journal of High Energy Physics 09/2011; 2012(1). DOI:10.1007/JHEP01(2012)038 · 6.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We point out that in theories where the gravitino mass, $M_{3/2}$, is in the
range (10-50)TeV, with soft-breaking scalar masses and trilinear couplings of
the same order, there exists a robust region of parameter space where the
conditions for electroweak symmetry breaking (EWSB) are satisfied without large
imposed cancellations. Compactified string/M-theory with stabilized moduli that
satisfy cosmological constraints generically require a gravitino mass greater
than about 30 TeV and provide the natural explanation for this phenomenon. We
find that even though scalar masses and trilinear couplings (and the
soft-breaking $B$ parameter) are of order (10-50)TeV, the Higgs vev takes its
expected value and the $\mu$ parameter is naturally of order a TeV. The
mechanism provides a natural solution to the cosmological moduli and gravitino
problems with EWSB.
[Show abstract][Hide abstract] ABSTRACT: Constraints on dark matter from the first CMS and ATLAS SUSY searches are
investigated. It is shown that within the minimal supergravity model, the early
search for supersymmetry at the LHC has depleted a large portion of the
signature space in dark matter direct detection experiments. In particular, the
prospects for detecting signals of dark matter in the XENON and CDMS
experiments are significantly affected in the low neutralino mass region. Here
the relic density of dark matter typically arises from slepton coannihilations
in the early universe. In contrast, it is found that the CMS and ATLAS analyses
leave untouched the Higgs pole and the Hyperbolic Branch/Focus Point regions,
which are now being probed by the most recent XENON results. Analysis is also
done for supergravity models with non-universal soft breaking where one finds
that a part of the dark matter signature space depleted by the CMS and ATLAS
cuts in the minimal SUGRA case is repopulated. Thus, observation of dark matter
in the LHC depleted region of minimal supergravity may indicate
non-universalities in soft breaking.
Modern Physics Letters A 03/2011; 26(21). DOI:10.1142/S0217732311036292 · 1.20 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The CMS and the ATLAS Collaborations have recently reported on the search for
supersymmetry with 35 pb$^{-1}$ of data and have put independent limits on the
parameter space of the supergravity unified model with universal boundary
conditions at the GUT scale for soft breaking, i.e., the mSUGRA model. We
extend this study by examining other regions of the mSUGRA parameter space in
$A_0$ and $\tan\beta$. Further, we contrast the reach of CMS and ATLAS with 35
pb$^{-1}$ of data with the indirect constraints, i.e., the constraints from the
Higgs boson mass limits, from flavor physics and from the dark matter limits
from WMAP. Specifically it is found that a significant part of the parameter
space excluded by CMS and ATLAS is essentially already excluded by the indirect
constraints and the fertile region of parameter space has yet to be explored.
We also emphasize that gluino masses as low as 400 GeV but for squark masses
much larger than the gluino mass remain unconstrained and further that much of
the hyperbolic branch of radiative electroweak symmetry breaking, with low
values of the Higgs mixing parameter $\mu$, is essentially untouched by the
recent LHC analysis.
Physics Letters B 03/2011; 699(5). DOI:10.1016/j.physletb.2011.04.041 · 6.13 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We present a focused study of a predictive unified model whose measurable
consequences are immediately relevant to early discovery prospects of
supersymmetry at the LHC. ATLAS and CMS have released their analysis with
35~pb$^{-1}$ of data and the model class we discuss is consistent with this
data. It is shown that with an increase in luminosity the LSP dark matter mass
and the gluino mass can be inferred from simple observables such as kinematic
edges in leptonic channels and peak values in effective mass distributions.
Specifically, we consider cases in which the neutralino is of low mass and
where the relic density consistent with WMAP observations arises via the
exchange of Higgs bosons in unified supergravity models. The magnitudes of the
gaugino masses are sharply limited to focused regions of the parameter space,
and in particular the dark matter mass lies in the range $\sim (50-65) ~\rm
GeV$ with an upper bound on the gluino mass of $575~{\rm GeV}$, with a typical
mass of $450~{\rm GeV}$. We find that all model points in this paradigm are
discoverable at the LHC at $\sqrt s = 7 \rm ~TeV$. We determine lower bounds on
the entire sparticle spectrum in this model based on existing experimental
constraints. In addition, we find the spin-independent cross section for
neutralino scattering on nucleons to be generally in the range of $\sigma^{\rm
SI}_{\na p} = 10^{-46 \pm 1}~\rm cm^2$ with much higher cross sections also
possible. Thus direct detection experiments such as CDMS and XENON already
constrain some of the allowed parameter space of the low mass gaugino models
and further data will provide important cross-checks of the model assumptions
in the near future.
[Show abstract][Hide abstract] ABSTRACT: We analyze supergravity models that predict a low mass gluino within the
landscape of sparticle mass hierarchies. The analysis includes a broad class of
models that arise in minimal and in non-minimal supergravity unified frameworks
and in extended models with additional $U(1)^n_X$ hidden sector gauge
symmetries. Gluino masses in the range $(350-700)$ GeV are investigated. Masses
in this range are promising for early discovery at the LHC at $\sqrt s =7$ TeV
(LHC-7). The models exhibit a wide dispersion in the gaugino-Higgsino
eigencontent of their LSPs and in their associated sparticle mass spectra. A
signature analysis is carried out and the prominent discovery channels for the
models are identified with most models needing only $\sim 1 \rm fb^{-1}$ for
discovery at LHC-7. In addition, significant variations in the discovery
capability of the low mass gluino models are observed for models in which the
gluino masses are of comparable size due to the mass splittings in different
models and the relative position of the light gluino within the various
sparticle mass hierarchies. The models are consistent with the current
stringent bounds from the Fermi-LAT, CDMS-II, XENON100, and EDELWEISS-2
experiments. A subclass of these models, which include a mixed-wino LSP and a
Higgsino LSP, are also shown to accommodate the positron excess seen in the
PAMELA satellite experiment.
[Show abstract][Hide abstract] ABSTRACT: A solution to the PAMELA positron excess with Higgsino dark matter within
extended supergravity grand unified (SUGRA) models is proposed. The models are
compliant with the photon constraints recently set by Fermi-LAT and produce
positron as well as antiproton fluxes consistent with the PAMELA experiment.
The SUGRA models considered have an extended hidden sector with extra degrees
of freedom which allow for a satisfaction of relic density consistent with
WMAP. The Higgsino models are also consistent with the CDMS-II and XENON100
data and are discoverable at LHC-7 with 1 fb^(-1) of luminosity. The models are
testable on several fronts.
[Show abstract][Hide abstract] ABSTRACT: An analysis of spin independent neutralino-proton cross sections σSI(χp) that includes this low mass region is given. The analysis is done in minimal supersymmetric standard model (MSSM) with radiative electroweak symmetry breaking (REWSB). It is found that cross sections as large as 10-40 cm2 can be accommodated in MSSM within the REWSB framework. However, inclusion of sparticle mass limits from current experiments, as well as lower limits on the Higgs searches from the Tevatron, and the current experimental upper limit on Bs→μ+μ- significantly limit the allowed parameter space reducing σSI(χp) to lie below ∼10-41 cm2 or even lower for neutralino masses around 10 GeV. These cross sections are an order of magnitude lower than the cross sections needed to explain the reported data in the recent dark matter experiments in the low neutralino mass region.
[Show abstract][Hide abstract] ABSTRACT: Most analyses of dark matter within supersymmetry assume the entire cold dark matter arising only from weakly interacting neutralinos. We study a new class of models consisting of $U(1)^n$ hidden sector extensions of the MSSM that includes several stable particles, both fermionic and bosonic, which can be interpreted as constituents of dark matter. In one such class of models, dark matter is made up of both a Majorana dark matter particle, i.e., a neutralino, and a Dirac fermion with the current relic density of dark matter as given by WMAP being composed of the relic density of the two species. These models can explain the PAMELA positron data and are consistent with the anti-proton flux data, as well as the photon data from FERMI-LAT. Further, it is shown that such models can also simultaneously produce spin independent cross sections which can be probed in CDMS-II, XENON-100 and other ongoing dark matter experiments. The implications of the models at the LHC and at the NLC are also briefly discussed. Comment: Journal: Physical Review D, Latex 32 pages, 4 eps figures
[Show abstract][Hide abstract] ABSTRACT: Signatures of soft supersymmetry breaking at the CERN LHC and in dark matter experiments are discussed with focus drawn to light superparticles, and in particular light gauginos and their discovery prospects. Connected to the above is the recent PAMELA positron anomaly and its implications for signatures of SUSY in early runs at the Large Hadron Collider. Other new possibilities for physics beyond the Standard Model are also briefly discussed. 1. Dual Probes of SUSY We review here testable predictions of high scale models with universal and non universal soft [supersymmetry] 1 breaking within the framework of applied supergravity (SUGRA) and effective models of string theories with D-branes supporting chiral gauge theories (for recent related reviews see [2,3]). Common to all these models are the ingredients needed for working in the predictive SUGRA framework, namely: (a) an effective
[Show abstract][Hide abstract] ABSTRACT: Recent re-evaluations of the Standard Model (SM) contribution to Br(b→sγ) hint at a positive correction from new physics. Since a charged Higgs boson exchange always gives a positive contribution to this branching ratio, the constraint points to the possibility of a relatively light charged Higgs. It is found that under the HFAG constraints and with re-evaluated SM results large cancellations between the charged Higgs and the chargino contributions in supersymmetric models occur. Such cancellations then correlate the charged Higgs and the chargino masses often implying both are light. Inclusion of the more recent evaluation of gμ−2 is also considered. The combined constraints imply the existence of several light sparticles. Signatures arising from these light sparticles are investigated and the analysis indicates the possibility of their early discovery at the LHC in a significant part of the parameter space. We also show that for certain restricted regions of the parameter space, such as for very large tanβ under the 1σ HFAG constraints, the signatures from Higgs production supersede those from sparticle production and may become the primary signatures for the discovery of supersymmetry.
Physics Letters B 03/2010; 685(2):174-181. DOI:10.1016/j.physletb.2010.01.055 · 6.13 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Motivated by specific connections to dark matter signatures, we study the prospects of observing the presence of a relatively light gluino whose mass is in the range ∼(500–900) GeV with a wino-like lightest supersymmetric particle with mass in the range of ∼(170–210) GeV. The light gaugino spectra studied here is generally different from other models, and in particular those with a wino dominated LSP, in that here the gluinos can be significantly lighter. The positron excess reported by the PAMELA satellite data is accounted for by annihilations of the wino LSP and their relic abundance can generally be brought near the WMAP constraints due to the late decay of a modulus field re-populating the density of relic dark matter. We also mention the recent FERMI photon constraints on annihilating dark matter in this class of models and implications for direct detection experiments including CDMS and XENON. We study these signatures in models of supersymmetry with non-minimal soft breaking terms derived from both string compactifications and related supergravity models which generally lead to non-universal gaugino masses. At the LHC, large event rates from the three-body decays of the gluino in certain parts of the parameter space are found to give rise to early discovery prospects for the gaugino sector. Excess events at the 5 sigma level can arise with luminosity as low as O(100) pb−1 at a center of mass energy of 10 TeV and ≲O(1) fb−1 at .
Physics Letters B 02/2010; 687(4-687):363-370. DOI:10.1016/j.physletb.2010.03.055 · 6.13 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The Large Hadron Collider presents an unprecedented opportunity to probe the realm of new physics in the TeV region and shed light on some of the core unresolved issues of particle physics. These include the nature of electroweak symmetry breaking, the origin of mass, the possible constituent of cold dark matter, new sources of CP violation needed to explain the baryon excess in the universe, the possible existence of extra gauge groups and extra matter, and importantly the path Nature chooses to resolve the hierarchy problem – is it supersymmetry or extra dimensions. Many models of new physics beyond the standard model contain a hidden sector which can be probed at the LHC. Additionally, the LHC will be a top factory and accurate measurements of the properties of the top and its rare decays will provide a window to new physics. Further, the LHC could shed light on the origin of neutralino masses if the new physics associated with their generation lies in the TeV region. Finally, the LHC is also a laboratory to test the hypothesis of TeV scale strings and D brane models. An overview of these possibilities is presented in the spirit that it will serve as a companion to the Technical Design Reports (TDRs) by the particle detector groups ATLAS and CMS to facilitate the test of the new theoretical ideas at the LHC. Which of these ideas stands the test of the LHC data will govern the course of particle physics in the subsequent decades.
[Show abstract][Hide abstract] ABSTRACT: An analysis is given connecting event rates for the direct detection of neutralino dark matter with the possible signatures of supersymmetry at the LHC. It is shown that if an effect is seen in the direct detection experiments at a level of $O(10^{-44})$ cm$^2$ for the neutralino-proton cross section, then within the mSUGRA model the next heavier particle above the neutralino is either a stau, a chargino, or a CP odd/CP even (A/H) Higgs boson. Further, the collider analysis shows that models with a neutralino-proton cross section at the level of $(1-5)\times 10^{-44}$ cm$^2$ could be probed with as little as 1 fb$^{-1}$ of integrated luminosity at the LHC at $\sqrt s=10$ TeV. The most recent limit from the five tower CDMS II result on WIMP-nucleon cross section is discussed in this context. It is argued that the conclusions of the analysis given here are more broadly applicable with inclusion of non-universalities in the SUGRA models. Comment: Published in PRD
[Show abstract][Hide abstract] ABSTRACT: The PAMELA positron excess is analyzed within the framework of nonuniversal SUGRA models with an extended $U(1)^n$ gauge symmetry in the hidden sector leading to neutralino dark matter with either a mixed Higgsino-wino LSP or an essentially pure wino dominated LSP. The Higgsino-wino LSP can produce the observed PAMELA positron excess and satisfy relic density constraints in the extended class of models due to a near degeneracy of the mass spectrum of the extended neutralino sector with the LSP mass. The simultaneous satisfaction of the WMAP relic density data and the PAMELA data is accomplished through a co-annihilation mechanism ($B_{\rm Co}-mechanism$), and leads to predictions of a neutralino and a chargino in the mass range (180-200) GeV as well as low lying sparticles accessible at colliders. We show that the models are consistent with the antiproton constraints from PAMELA as well as photon flux data from EGRET and FERMI-LAT. Predictions for the scalar neutralino proton cross section relevant for the direct detection of dark matter are also discussed and signatures at the LHC for these PAMELA inspired models are analyzed. It is shown that the mixed Higgsino-wino LSP model will be discoverable with as little as 1 fb$^{-1}$ of data and is thus a prime candidate for discovery in the low luminosity runs at the LHC. Comment: 13 pages, 7 figures; additional refs. in v2; published in PRD
[Show abstract][Hide abstract] ABSTRACT: The possibility that the gluino is the next to the lightest supersymmetric particle (NLSP) is discussed and it is shown that this situation arises in nonuniversal SUGRA models within a significant part of the parameter space compatible with all known experimental bounds. It is then shown that the gluino NLSP (GNLSP) models lead to a compressed sfermion spectrum with the sleptons often heavier than the squarks at least for the first two generations. The relic density here is governed by gluino coannihilation which is responsible for a relatively small mass splitting between the gluino and the neutralino masses. Thus the GNLSP class of models is very predictive first because the SUSY production cross sections at the LHC are dominated by gluino production and second because the gluino production itself proceeds dominantly through a single channel which allows for a direct determination of the gluino mass and an indirect determination of the neutralino mass due to a linear relation between these two masses which is highly constrained by coannihilation. A detailed analysis of these models shows that the jet production and tagged b-jets from the gluino production can be discriminated from the standard model background with appropriate cuts. It is found that the GNLSP models can be tested with just 10 fb$^{-1}$ of integrated luminosity and may therefore be checked with low luminosity runs in the first data at the LHC. Thus if a GNLSP model is realized, the LHC will turn into a gluino factory through a profuse production of gluinos with typically only a small fraction $\lesssim 5%$ of total SUSY events arising from other production modes over the allowed GNLSP model parameter space. Comment: 33 pages, 8 figures, accepted for publication in Physical Review D
[Show abstract][Hide abstract] ABSTRACT: The recent positron excess observed in the PAMELA satellite experiment strengthens previous experimental findings. We give here an analysis of this excess in the framework of the Stueckelberg extension of the standard model which includes an extra $U(1)_X$ gauge field and matter in the hidden sector. Such matter can produce the right amount of dark matter consistent with the WMAP constraints. Assuming the hidden sector matter to be Dirac fermions it is shown that their annihilation can produce the positron excess with the right positron energy dependence seen in the HEAT, AMS and the PAMELA experiments. Further test of the proposed model can come at the Large Hadron Collider. The predictions of the $\bar p/p$ flux ratio also fit the data.