We examine the implications of the recent CDF measurement of the top-quark forward-backward asymmetry, focusing on a scenario with a new color octet vector boson at 1-3 TeV. We study several models, ...as well as a general effective field theory, and determine the parameter space which provides the best simultaneous fit to the CDF asymmetry, the Tevatron top pair production cross section, and the exclusion regions from LHC dijet resonance and contact interaction searches. Flavor constraints on these models are more subtle and less severe than the literature indicates. We find a large region of allowed parameter space at high axigluon mass and a smaller region at low mass; we match the latter to an SU(3)
1
× SU(3)
2
/SU(3)
c
coset model with a heavy vector-like fermion. Our scenario produces discoverable effects at the LHC with only 1–2 fb
−1
of luminosity at
. Lastly, we point out that a Tevatron measurement of the
b
-quark forward-backward asymmetry would be very helpful in characterizing the physics underlying the top-quark asymmetry.
Higgs sector and fine-tuning in the phenomenological MSSM Cahill-Rowley, Matthew W.; Hewett, JoAnne L.; Ismail, Ahmed ...
Physical review. D, Particles, fields, gravitation, and cosmology,
10/2012, Letnik:
86, Številka:
7
Journal Article
Recenzirano
Odprti dostop
The recent discovery of a 125 GeV Higgs, as well as the lack of any positive findings in searches for supersymmetry, has renewed interest in both the supersymmetric Higgs sector and fine-tuning (FT). ...Here, we continue our study of the phenomenological minimal supersymmetric standard model (pMSSM), discussing the light Higgs and FT within the context of two sets of previously generated pMSSM models. We find an abundance of models with experimentally favored Higgs masses and couplings. We investigate the decay modes of the light Higgs in these models, finding strong correlations between many final states. We then examine the degree of FT, considering contributions from each of the pMSSM parameters at up to next-to-leading log order. In particular, we examine the FT implications for our model sets that arise from the discovery of a 125 GeV Higgs. Finally, we investigate a small subset of models with low FT and a light Higgs near 125 GeV, describing the common features of such models. We generically find a light stop and bottom with complex decay patterns into a set of light electroweak gauginos, which will make their discovery more challenging and may require novel search techniques.
The new look pMSSM with neutralino and gravitino LSPs Cahill-Rowley, Matthew W.; Hewett, JoAnne L.; Hoeche, Stefan ...
The European physical journal. C, Particles and fields,
09/2012, Letnik:
72, Številka:
9
Journal Article
Recenzirano
Odprti dostop
The pMSSM provides a broad perspective on SUSY phenomenology. In this paper we generate two new, very large, sets of pMSSM models with sparticle masses extending up to 4 TeV, where the lightest ...supersymmetric particle (LSP) is either a neutralino or gravitino. The existence of a gravitino LSP necessitates a detailed study of its cosmological effects and we find that Big Bang Nucleosynthesis places strong constraints on this scenario. Both sets are subjected to a global set of theoretical, observational and experimental constraints resulting in a sample of ∼225k viable models for each LSP type. The characteristics of these two model sets are briefly compared. We confront the neutralino LSP model set with searches for SUSY at the 7 TeV LHC using both the missing (MET) and non-missing
E
T
ATLAS analyses. In the MET case, we employ Monte Carlo estimates of the ratios of the SM backgrounds at 7 and 8 TeV to rescale the 7 TeV data-driven ATLAS backgrounds to 8 TeV. This allows us to determine the pMSSM parameter space coverage for this collision energy. We find that an integrated luminosity of ∼5–20 fb
−1
at 8 TeV would yield a substantial increase in this coverage compared to that at 7 TeV and can probe roughly half of the model set. If the pMSSM is not discovered during the 8 TeV run, then our model set will be essentially void of gluinos and lightest first and second generation squarks that are ≲700–800 GeV, which is much less than the analogous mSUGRA bound. Finally, we demonstrate that non-MET SUSY searches continue to play an important role in exploring the pMSSM parameter space. These two pMSSM model sets can be used as the basis for investigations for years to come.
We investigate the sensitivity of the next generation of flavor-based low-energy experiments to probe the supersymmetric parameter space in the context of the phenomenological minimal supersymmetric ...Standard Model and examine the complementarity with direct searches for supersymmetry at the 13 TeV LHC in a quantitative manner. To this end, we enlarge the previously studied phenomenological minimal supersymmetric Standard Model parameter space to include all physical nonzero CP-violating phases, namely those associated with the gaugino mass parameters; Higgsino mass parameter and the trilinear couplings of the top quark, bottom quark, and tau lepton. We find that future electric dipole moment and flavor measurements can have a strong impact on the viability of these models even if the sparticle spectrum is out of reach of the 13 TeV LHC. In particular, the lack of positive signals in future low-energy probes would exclude values of the phases between scriptO(10 super(-2)) and scriptO(10 super(-1)). We also find regions of parameter space where large phases remain allowed due to cancellations. Most interestingly, in some rare processes, such as BR(B sub(s)1 mu super(+) mu super(-)), we find that contributions arising from CP-violating phases can bring the potentially large supersymmetry contributions into better agreement with experiment and Standard Model predictions.
Supersymmetry without prejudice at the LHC Conley, John A.; Gainer, James S.; Hewett, JoAnne L. ...
The European physical journal. C, Particles and fields,
07/2011, Letnik:
71, Številka:
7
Journal Article
Recenzirano
Odprti dostop
The discovery and exploration of Supersymmetry in a model-independent fashion will be a daunting task due to the large number of soft-breaking parameters in the MSSM. In this paper, we explore the ...capability of the ATLAS detector at the LHC (
TeV, 1 fb
−1
) to find SUSY within the 19-dimensional pMSSM subspace of the MSSM using their standard transverse missing energy and long-lived particle searches that were essentially designed for mSUGRA. To this end, we employ a set of ∼71k previously generated model points in the 19-dimensional parameter space that satisfy all of the existing experimental and theoretical constraints. Employing ATLAS-generated SM backgrounds and following their approach in each of 11 missing energy analyses as closely as possible, we explore all of these 71k model points for a possible SUSY signal. To test our analysis procedure, we first verify that we faithfully reproduce the published ATLAS results for the signal distributions for their benchmark mSUGRA model points. We then show that, requiring all sparticle masses to lie below 1(3) TeV, almost all (two-thirds) of the pMSSM model points are discovered with a significance
S
>5 in at least one of these 11 analyses assuming a 50% systematic error on the SM background. If this systematic error can be reduced to only 20% then this parameter space coverage is increased. These results are indicative that the ATLAS SUSY search strategy is robust under a broad class of Supersymmetric models. We then explore in detail the properties of the kinematically accessible model points which remain unobservable by these search analyses in order to ascertain problematic cases which may arise in general SUSY searches.
A
bstract
A heavy Standard Model Higgs boson is not only disfavored by electroweak precision observables but is also excluded by direct searches at the 7 TeV LHC for a wide range of masses. Here, we ...examine scenarios where a heavy Higgs boson can be made consistent with both the indirect constraints and the direct null searches by adding only one new particle beyond the Standard Model. This new particle should be a weak multiplet in order to have additional contributions to the oblique parameters. If it is a color singlet, we find that a heavy Higgs with an intermediate mass of 200–300 GeV can decay into the new states, suppressing the branching ratios for the standard model modes, and thus hiding a heavy Higgs at the LHC. If the new particle is also charged under QCD, the Higgs production cross section from gluon fusion can be reduced significantly due to the new colored particle one-loop contribution. Current collider constraints on the new particles allow for viable parameter space to exist in order to hide a heavy Higgs boson. We categorize the general signatures of these new particles, identify favored regions of their parameter space and point out that discovering or excluding them at the LHC can provide important in- direct information for a heavy Higgs. Finally, for a very heavy Higgs boson, beyond the search limit at the 7 TeV LHC, we discuss three additional scenarios where models would be consistent with electroweak precision tests: including an additional vector-like fermion mixing with the top quark, adding another U(1) gauge boson and modifying triple-gauge boson couplings.
Recent theoretical results have demonstrated that noncommutative geometries naturally appear within the context of string or M theory. One consequence of this possibility is that QED takes on a ...non-Abelian nature due to the introduction of 3- and 4-point functions. In addition, each QED vertex acquires a momentum dependent phase factor. We parametrize the effects of noncommutative space-time coordinates and show that they lead to observable signatures in several 2{yields}2 QED processes in e{sup +}e{sup -} collisions. In particular, we examine pair annihilation, Moller and Bhabha scattering, as well as {gamma}{gamma}{yields}{gamma}{gamma} scattering and show that noncommutative scales of order a TeV can be probed at high energy linear colliders.
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