CEDM constraints on modified sfermion universality and spontaneous CP violation

We discuss the supersymmetric CP problem that arises when the sfermion soft mass universality is modified. We place the 3rd generation SU(5) ten-plet sfermion masses in the weak scale in view of the naturalness. The other sfermion masses are assumed to be universal and a TeV scale in order to weaken the flavor changing neutral current processes and electric dipole moment (EDM) constraints. However this modification generically induces too large up quark chromo-EDM (CEDM) via the weak scale stop loop. In order to suppress this CEDM, we propose certain type of flavor structure where the parameters of the up-(s)quark sector are real whereas those of the down-(s)quark and the charged (s)lepton sectors are complex at the GUT scale. It is shown that, in this set up, up quark CEDM can be suppressed within the range where the current and future experiments have their sensitivity. We briefly illustrate the simple realization of these particular forms of the modified sfermion universality with real up-(s)quark sector by spontaneous CP violation in E$_6$ SUSY GUT with SU(2) flavor symmetry.Comment: Hg EDM bound updated, content modified, figure added, typos corrected, references adde

Constraint from recent ATLAS results on non-universal sfermion mass models and naturalness

We investigate the impact of recent direct supersymmetry (SUSY) searches on a non-universal sfermion mass scenario focusing on naturalness. One of the advantages of this scenario is that the non-universality between third generation and first two generation sfermion masses can relax the tension between naturalness and constraints from flavour and CP violating observables. In the parameter region, where various phenomenological constraints are satisfied, the constraints to this scenario from ATLAS 165pb-1 "0-lepton" search and 35pb-1 "b-jet" search are much weaker than those to the constrained minimal SUSY standard model, because of differences in the main SUSY production processes and the main decay chains. Naturalness can be easily achieved in this scenario in accord with the current direct SUSY searches. An additional dedicated analysis may be needed to discover/exclude this scenario.Comment: 15 pages, 7 figures, 2 table

The Interplay Between GUT and Flavour Symmetries in a Pati-Salam x S4 Model

Both Grand Unified symmetries and discrete flavour symmetries are appealing ways to describe apparent structures in the gauge and flavour sectors of the Standard Model. Both symmetries put constraints on the high energy behaviour of the theory. This can give rise to unexpected interplay when building models that possess both symmetries. We investigate on the possibility to combine a Pati-Salam model with the discrete flavour symmetry $S_4$ that gives rise to quark-lepton complementarity. Under appropriate assumptions at the GUT scale, the model reproduces fermion masses and mixings both in the quark and in the lepton sectors. We show that in particular the Higgs sector and the running Yukawa couplings are strongly affected by the combined constraints of the Grand Unified and family symmetries. This in turn reduces the phenomenologically viable parameter space, with high energy mass scales confined to a small region and some parameters in the neutrino sector slightly unnatural. In the allowed regions, we can reproduce the quark masses and the CKM matrix. In the lepton sector, we reproduce the charged lepton masses, including bottom-tau unification and the Georgi-Jarlskog relation as well as the two known angles of the PMNS matrix. The neutrino mass spectrum can present a normal or an inverse hierarchy, and only allowing the neutrino parameters to spread into a range of values between $\lambda^{-2}$ and $\lambda^2$, with $\lambda\simeq0.2$. Finally, our model suggests that the reactor mixing angle is close to its current experimental bound.Comment: 62 pages, 4 figures; references added, version accepted for publication in JHE

Exploiting process similarity of 3d flash memory for high performance SSDs

© 2019 Association for Computing Machinery.3D NAND flash memory exhibits two contrasting process characteristics from its manufacturing process. While process variability between different horizontal layers are well known, little has been systematically investigated about strong process similarity (PS) within the horizontal layer. In this paper, based on an extensive characterization study using real 3D flash chips, we show that 3D NAND flash memory possesses very strong process similarity within a 3D flash block: the word lines (WLs) on the same horizontal layer of the 3D flash block exhibit virtually equivalent reliability characteristics. This strong process similarity, which was not previously utilized, opens simple but effective new optimization opportunities for 3D flash memory. In this paper, we focus on exploiting the process similarity for improving the I/O latency. By carefully reusing various flash operating parameters monitored from accessing the leading WL, the remaining WLs on the same horizontal layer can be quickly accessed, avoiding unnecessary redundant steps for subsequent program and read operations. We also propose a new program sequence, called mixed order scheme (MOS), for 3D NAND flash memory which can further reduce the program latency. We have implemented a PS-aware FTL, called cubeFTL, which takes advantage of the proposed techniques. Our evaluation results show that cubeFTL can improve the IOPS by up to 48% over an existing PS-unaware FTL.N