9,128 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
Interlayer Couplings Mediated by Antiferromagnetic Magnons
Collinear antiferromagnets (AFs) support two degenerate magnon excitations
carrying opposite spin polarizations, by which magnons can function as
electrons in various spin-related phenomena. In an insulating
ferromagnet(F)/AF/F trilayer, we explore the magnon-mediated interlayer
coupling by calculating the magnon thermal energy in the AF as a function of
the orientations of the Fs. The effect manifests as an interlayer exchange
interaction and a perpendicular magnetic anisotropy; they both depend on
temperature and the AF thickness. In particular, the exchange interaction turns
out to be antiferromagnetic at low temperatures and ferromagnetic at high
temperatures, whose magnitude can be eV for nanoscale
separations, allowing experimental verification.Comment: Physical Review Letters 121, 207202 (2018
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