33 research outputs found
Little String Theory at a TeV
We propose a framework where the string scale as well as all compact dimensions are at the electroweak scale TeV. The weakness of gravity is attributed to the small value of the string coupling , presumably a remnant of the dilaton's runaway behavior, suggesting the possibility of a common solution to the hierarchy and dilaton-runaway problems. In spite of the small , in type II string theories with gauge interactions localized in the vicinity of NS5-branes, the standard model gauge couplings are of order one and are associated with the sizes of compact dimensions. At a TeV these theories exhibit higher dimensional and stringy behavior. The models are holographically dual to a higher dimensional non-critical string theory and this can be used to compute the experimentally accessible spectrum and self-couplings of the little strings. In spite of the stringy behavior, gravity remains weak and can be ignored at collider energies. The Damour-Polyakov mechanism is an automatic consequence of our scenario and may lead to small violations of the equivalence principle, potentially observable in satellite experiments
Experimental signatures of low energy gauge mediated supersymmetry breaking
The experimental signatures for gauge mediated supersymmetry breaking are presented. The phenomenology associated with this class of models is distinctive since the gravitino is naturally the LSP. The next lightest supersymmetric particle (NLSP) can be a gaugino, Higgsino, or right handed slepton. Decay of the NLSP to its partner plus the LSP proceeds through the Goldstino component of the gravitino. For a significant range of parameters this decay can take place within the detector, and can be measured as a displaced vertex or kink in a charged particle track. In the case that the NLSP is mostly gaugino, we identify the discovery modes as e^+e^- \rightarrow \gamma \gamma + \Emiss, and p \bar{p} \rightarrow l^+ l^- \gamma \gamma + \EmissT. If the NLSP is a right handed slepton the discovery modes are e^+ e^- \rightarrow l^+ l^- + \Emiss and p \bar{p} \rightarrow l^+ l^- + \EmissT. An NLSP which is mostly Higgsino is also considered. Finally, these theories can contain scalar particles which mediate sub-millimeter range coherent forces of gravitational strength
Phenomenology, Astrophysics and Cosmology of Theories with Sub-Millimeter Dimensions and TeV Scale Quantum Gravity
We recently proposed a solution to the hierarchy problem not relying on
low-energy supersymmetry or technicolor. Instead, the problem is nullified by
bringing quantum gravity down to the TeV scale. This is accomplished by the
presence of new dimensions of sub-millimeter size, with the SM
fields localised on a 3-brane in the higher dimensional space. In this paper we
systematically study the experimental viability of this scenario. Constraints
arise both from strong quantum gravitational effects at the TeV scale, and more
importantly from the production of massless higher dimensional gravitons with
TeV suppressed couplings. Theories with are safe due mainly to the
infrared softness of higher dimensional gravity. For , the six dimensional
Planck scale must be pushed above TeV to avoid cooling SN1987A and
distortions of the diffuse photon background. Nevertheless, the particular
implementation of our framework within type I string theory can evade all
constraints, for any , with string scale TeV. We also
explore novel phenomena resulting from the existence of new states propagating
in the higher dimensional space. The Peccei-Quinn solution to the strong CP
problem is revived with a weak scale axion in the bulk. Gauge fields in the
bulk can mediate repulsive forces times stronger than
gravity at sub-mm distances, and may help stabilize the proton.
Higher-dimensional gravitons produced on our brane and captured on a different
"fat" brane can provide a natural dark matter candidate.Comment: 51 pages, late
Supersymmetric Unification Without Low Energy Supersymmetry And Signatures for Fine-Tuning at the LHC
The cosmological constant problem is a failure of naturalness and suggests
that a fine-tuning mechanism is at work, which may also address the hierarchy
problem. An example -- supported by Weinberg's successful prediction of the
cosmological constant -- is the potentially vast landscape of vacua in string
theory, where the existence of galaxies and atoms is promoted to a vacuum
selection criterion. Then, low energy SUSY becomes unnecessary, and
supersymmetry -- if present in the fundamental theory -- can be broken near the
unification scale. All the scalars of the supersymmetric standard model become
ultraheavy, except for a single finely tuned Higgs. Yet, the fermions of the
supersymmetric standard model can remain light, protected by chiral symmetry,
and account for the successful unification of gauge couplings. This framework
removes all the difficulties of the SSM: the absence of a light Higgs and
sparticles, dimension five proton decay, SUSY flavor and CP problems, and the
cosmological gravitino and moduli problems. High-scale SUSY breaking raises the
mass of the light Higgs to about 120-150 GeV. The gluino is strikingly long
lived, and a measurement of its lifetime can determine the ultraheavy scalar
mass scale. Measuring the four Yukawa couplings of the Higgs to the gauginos
and higgsinos precisely tests for high-scale SUSY. These ideas, if confirmed,
will demonstrate that supersymmetry is present but irrelevant for the hierarchy
problem -- just as it has been irrelevant for the cosmological constant problem
-- strongly suggesting the existence of a fine-tuning mechanism in nature.Comment: Typos and equations fixed, references adde
Matter-wave Atomic Gradiometer Interferometric Sensor (MAGIS-100)
MAGIS-100 is a next-generation quantum sensor under construction at Fermilab
that aims to explore fundamental physics with atom interferometry over a
100-meter baseline. This novel detector will search for ultralight dark matter,
test quantum mechanics in new regimes, and serve as a technology pathfinder for
future gravitational wave detectors in a previously unexplored frequency band.
It combines techniques demonstrated in state-of-the-art 10-meter-scale atom
interferometers with the latest technological advances of the world's best
atomic clocks. MAGIS-100 will provide a development platform for a future
kilometer-scale detector that would be sufficiently sensitive to detect
gravitational waves from known sources. Here we present the science case for
the MAGIS concept, review the operating principles of the detector, describe
the instrument design, and study the detector systematics.Comment: 65 pages, 18 figure