3,038 research outputs found
Naturalness and a light
Models with a light, additional gauge boson are attractive extensions of the
standard model. Often these models are only considered as effective low energy
theory without any assumption about an UV completion. This leaves not only the
hierarchy problem of the SM unsolved, but introduces a copy of it because of
the new fundamental scalars responsible for breaking the new gauge group. A
possible solution is to embed these models into a supersymmetric framework.
However, this gives rise to an additional source of fine-tuning compared to the
MSSM and poses the question how natural such a setup is. One might expect that
the additional fine-tuning is huge, namely, . In
this paper we point out that this is not necessarily the case. We show that it
is possible to find a focus point behaviour also in the new sector in
co-existence to the MSSM focus point. We call this 'Double Focus Point
Supersymmetry'. Moreover, we stress the need for a proper inclusion of
radiative corrections in the fine-tuning calculation: a tree-level estimate
would lead to predictions for the tuning which can be wrong by many orders of
magnitude. As showcase, we use the extended MSSM and discuss
possible consequence of the observed anomaly. However, similar
features are expected for other models with an extended gauge group which
involve potentially large Yukawa-like interactions of the new scalars.Comment: 11 pages, 4 figures, two column format, reference update
Neutralino Dark Matter in Gauge Mediation After Run I of LHC and LUX
Neutralino can be the dark matter candidate in the gauge-mediated
supersymmetry breaking models if the conformal sequestered mechanism is assumed
in the hidden sector. In this paper, we study this mechanism by using the
current experimental results after the run I of LHC and LUX. By adding new
Yukawa couplings between the messenger fields and Higgs fields, we find that
this mechanism can predict a neutralino dark matter with correct relic density
and a Higgs boson with mass around 125 GeV. All our survived points have some
common features. Firstly, the Higgs sector falls into the decoupling limit. So
the properties of the light Higgs boson are similar to the predictions of the
Standard Model one. Secondly, the correct EWSB hints a relatively small
-term, which makes the lightest neutralino lighter than the lightest stau.
So a bino-higgsino dark matter with correct relic density can be achieved. And
the relatively small -term results in a small fine-tuning. Finally, this
bino-higgsino dark matter can pass all current bounds, including both
spin-independent and spin-dependent direct searches. The spin-independent cross
section of our points can be examined by further experiments.Comment: Minor changes, version to appear in Phys. Lett.
Higgs Mass and Muon Anomaly in MSSM with Gauge-Gravity hybrid Mediation
In general, we can propose the hybrid supersymmetry breakings and hybrid
mediations in the Supersymmetric Standard Models (SSMs). In this paper, we
study the hybrid mediation for supersymmetry (SUSY) breaking. In particular, we
study how to keep the good properties of gravity mediation, gauge mediation,
and anomaly mediation, while solve their problems simultaneously. As an
example, we consider the anomaly-gravity mediation, where all the
supersymmetric particles (sparticles) obtain the SUSY breaking soft terms from
the traditional gravity mediation while gauge mediation gives dominant
contributions to the soft terms in the colored sector due to the splitted
messengers. Thus, we can realize the electroweak supersymmetry naturally where
the sleptons, sneutrinos, and electroweakinos are light within one TeV while
the squarks and gluino are heavy around a few TeVs. And then we can explain 125
GeV Higgs mass, satisfy the LHC SUSY search bounds, and explain the anomalous
magnetic momement of muon, etc. Moreover, the gluino and squarks are well
beyond the current LHC Run II searches.Comment: 19 pages, add discussions and figures about the mode
Supersoft Supersymmetry, Conformal Sequestering, and Single Scale Supersymmetry Breaking
Supersymmetric Standard Models (SSMs) with Dirac gauginos have the appealing
supersoft property that they only cause finite contributions to scalar masses.
Considering gauge mediated SUSY breaking with conformal sequestering and
assuming there is one and only one fundamental parameter with dimension mass
arising from supersymmetry breaking, we find a cancellation between the
dominant terms that contribute to the EWFT. The resulting EWFT measure can be
of order one even for supersymmetric particle masses and -terms in the TeV
range.Comment: 6 pages, 1 figure; v2: title and abstract changed, small rephrasing
of the text, conclusions unchanged. Matches version accepted for publication
by PR
Focus Point Supersymmetry in Extended Gauge Mediation
We propose a small extenion of the minimal gauge mediation through the
combination of extended gauge mediation and conformal sequestering. We show
that the focus point supersymmetry can be realized naturally, and the
fine-tuning is signifcantly reduced compared to the minimal gauge mediation and
extended gauge mediation without focus point. The Higgs boson mass is around
125 GeV, the gauginos remain light, and the gluino is likely to be detected at
the next run of the LHC. However, the multi-TeV squarks is out of the reach of
the LHC. The numerical calculation for finetuning shows that this model remains
natural.Comment: 23 pages, 7 figures, references adde
Towards the Natural Gauge Mediation
The sweet spot supersymmetry (SUSY) solves the mu problem in the Minimal
Supersymmetric Standard Model (MSSM) with gauge mediated SUSY breaking (GMSB)
via the generalized Giudice-Masiero (GM) mechanism where only the mu-term and
soft Higgs masses are generated at the unification scale of the Grand Unified
Theory (GUT) due to the approximate PQ symmetry. Because all the other SUSY
breaking soft terms are generated via the GMSB below the GUT scale, there
exists SUSY electroweak (EW) fine-tuning problem to explain the 125 GeV Higgs
boson mass due to small trilinear soft term. Thus, to explain the Higgs boson
mass, we propose the GMSB with both the generalized GM mechanism and
Higgs-messenger interactions. The renormalization group equations are runnings
from the GUT scale down to EW scale. So the EW symmetry breaking can be
realized easier. We can keep the gauge coupling unification and solution to the
flavor problem in the GMSB, as well as solve the \mu/B_{\mu}-problem. Moreover,
there are only five free parameters in our model. So we can determine the
characteristic low energy spectra and explore its distinct phenomenology. The
low-scale fine-tuning measure can be as low as 20 with the light stop mass
below 1 TeV and gluino mass below 2 TeV. The gravitino dark matter can come
from a thermal production with the correct relic density and be consistent with
the thermal leptogenesis. Because gluino and stop can be relatively light in
our model, how to search for such GMSB at the upcoming run II of the LHC
experiment could be very interesting.Comment: 22 pages, 7 figures, Late
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