18 research outputs found
Midi-review: Status of weak scale supersymmetry after LHC Run 2 and ton-scale noble liquid WIMP searches
While LHC has discovered a very Standard Model-like Higgs boson of mass m_h~
125 GeV, no solid signal for physics beyond the Standard Model has emerged so
far at LHC or at WIMP seach experiments. For the case of weak scale
supersymmetry (SUSY), LHC has found rather generally that gluinos are beyond
about 2.2 TeV whilst top squark must lie beyond 1.1 TeV. These limits
contradict older simplistic notions of naturalness that emerged in the
1980s-1990s, leading to the rather pessimistic view that SUSY is now excluded
except for perhaps some remaining narrow corners of parameter space. Yet, this
picture ignores several important developments in SUSY/string theory that
emerged in the 21st century: 1. the emergence of the string theory landscape
and its solution to the cosmological constant problem, 2. a more nuanced view
of naturalness including the notion of "stringy naturalness", 3. the emergence
of anomaly-free discrete R-symmetries and their connection to R-parity,
Peccei-Quinn symmetry, the SUSY mu problem and proton decay and 4. the
importance of including a solution to the strong CP problem. Rather general
considerations from the string theory landscape favor large values of soft
terms, subject to the vacuum selection criteria that electroweak symmetry is
properly broken (no CCB minima) and the resulting magnitude of the weak scale
is not too far from our measured value. Then stringy naturalness predicts a
Higgs mass m_h~ 125 GeV whilst sparticle masses are typically lifted beyond
present LHC bounds. In light of these refinements in theory perspective
confronted by LHC and dark matter search results, we review the most likely
LHC, ILC and dark matter signatures that are expected to arise from weak scale
SUSY as we understand it today.Comment: 47 pages; version 2 includes typo fixes and some added discussion;
version 3 contains minor re-wording on weak scale limits from Agrawal et a
Phenomenology of the String Theory Landscape
In this dissertation, we perform a thorough phenomenological study of the string theory landscape. To this end, we compare and contrast the data collected from particle accelerators and detectors against various models of observable particle phenomena. One stark indirect evidence of underlying string theory is the existence of supersymmetric (SUSY) particles, a variety of new particles resulting from a symmetry between the bosons and fermions observed in nature: i.e. every boson should be paired with a fermionic partner and vice versa. The discovery of the Higgs boson at the LHC in 2012, the particle responsible for giving mass to matter particles (e.g. electrons) and the massive gauge bosons, has provided us with strong bounds on the masses of these yet unobserved superpartner particles, which when combined with string theory landscape arguments, can yield strong statistical predictions for observing SUSY in future upgrades to particle accelerators. Various SUSY models are explored in the context of string landscape statistics by which we can rule some models out as realistic extensions to the Standard Model (SM). We also argue how realistic SUSY models requires the Higgs boson mass to be around 125 GeV with superpartners beyond current energy limits of the LHC - just what is observed experimentally. Additionally, we also analyze the prospect of detecting dark matter particles which only gravitate and exhibit at best only weak interactions. The emergence of SUSY also equips us with such Weakly Interacting Massive Particles (WIMPs), whose mass range can then be statistically predicted using string landscape arguments
Radiative natural supersymmetry emergent from the string landscape
In string theory with flux compactifications, anthropic selection for
structure formation from a discretuum of vacuum energy values provides at
present our only understanding of the tiny yet positive value of the
cosmological constant. We apply similar reasoning to a toy model of the
multiverse restricted to vacua with the MSSM as the low energy effective
theory. Here, one expects a statistical selection favoring large soft SUSY
breaking terms leading to a derived value of the weak scale in each pocket
universe (with appropriate electroweak symmetry breaking) which differs from
the weak scale as measured in our universe. In contrast, the SUSY preserving
\mu parameter is selected uniformly on a log scale as is consistent with the
distribution of SM fermion masses: this favors smaller values of \mu. An
anthropic selection of the weak scale to within a factor of a few of our
measured value -- in order to produce complex nuclei as we know them (atomic
principle) -- provides statistical predictions for Higgs and sparticle masses
in accord with LHC measurements. The statistical selection then more often
leads to (radiatively-driven) {\it natural} SUSY models over the Standard Model
or finely-tuned SUSY models such as mSUGRA/CMSSM, split, mini-split, spread,
high scale or PeV SUSY. The predicted Higgs and superparticle spectra might be
testable at HL-LHC via higgsino pair production but is certainly testable at
higher energy hadron colliders with \sqrt{s}~ 30-100 TeV.Comment: 21 pages with 13 .png figures; version 2 includes corrected Fig.
LHC SUSY and WIMP dark matter searches confront the string theory landscape
Abstract The string theory landscape of vacua solutions provides physicists with some understanding as to the magnitude of the cosmological constant. Similar reasoning can be applied to the magnitude of the soft SUSY breaking terms in supersymmetric models of particle physics: there appears to be a statistical draw towards large soft terms which is tempered by the anthropic requirement of the weak scale lying not too far from ∼ 100 GeV. For a mild statistical draw of m soft n with n = 1 (as expected from SUSY breaking due to a single F term) then the light Higgs mass is preferred at ∼ 125 GeV while sparticles are all pulled beyond LHC bounds. We confront a variety of LHC and WIMP dark matter search limits with the statistical expectations from a fertile patch of string theory landscape. The end result is that LHC and WIMP dark matter detectors see exactly that which is expected from the landscape: a Standard Model-like Higgs boson of mass 125 GeV but as yet no sign of sparticles or WIMP dark matter. SUSY from the n = 1 landscape is most likely to emerge at LHC in the soft opposite-sign dilepton plus jet plus MET channel. Multi-ton noble liquid WIMP detectors should be able to completely explore the n = 1 landscape parameter space