30208210
Nearly degenerate gauginos and dark matter at the LHC
Motivated by dark-matter considerations in supersymmetric theories, we investigate in a fairly modelindependent way the detection at the LHC of nearly degenerate gauginos with mass differences between a few GeV and about 30 GeV. Due to the degeneracy of gaugino states, the conventional leptonic signals are likely lost. We first consider the leading signal from glu ino production and decay. We find that it is quite conceivable to reach a large statistical significance for the multi-jet plus missing energy signal with an integrated luminosity about 50 pb −1 (50 fb −1 ) for a gluino mass of 500 GeV (1 TeV). If gluinos are not too heavy, less than about 1.5 TeV, this channel can typically probe gaugino masses up to about 100 GeV below the gluino mass. We then study the Drell-Yan type of gaugino pair production in association with a hard QCD jet, for gaugino masses in the range of 100‐150 GeV. The signal observation may be statistically feasible with about 10 fb −1 , but systematically challenging due to the lack of distinct ive features for the signal distributions. By exploiting gaugino pair pr oduction through weak boson fusion, signals of large missing energy plus two forward-backward jets may be observable at a 4‐6σ level above the large SM backgrounds with an integrated luminosity of 100‐300 fb −1 . Finally, we point out that searching for additional isolated soft muons in the range pT ∼ 3‐10 GeV in the data samples discussed above may help to enrich the signal and to control the systematics. Signific ant efforts are made to explore the connection between the signal kinematics and the relevant masses for the gluino and gauginos, to probe the mass scales of the superpartners, in particular the LSP dark matter.
119101850
Higgs precision measurements and flavor physics: a supersymmetric example
Rare decays in flavor physics often suffer from Helicity suppress and Loop suppress. Helicity flip is a direct consequence of chiral $$U(3)$$U(3) symmetry breaking and electroweak symmetry breaking. The identical feature is also shared by the mass generation of SM fermions. In this review, we use the Minimal Supersymmetric Standard Model (MSSM) as an example to illustrate an explicit connection between bottom Yukawa coupling and rare decay process of $$b\rightarrow s\gamma $$b→sγ. We take a symmetry approach to study the common symmetry breaking in supersymmetric correction to bottom quark mass generation and $$b\rightarrow s\gamma $$b→sγ. We show that Large Peccei-Quinn symmetry breaking effect and $$R$$R-symmetry breaking effect required by $$b\rightarrow s\gamma $$b→sγ inevitably lead to significant reduction of bottom Yukawa $${y}_{b}$$yb. To compromise the reduction in $$b\bar{b}$$bb¯, a new decay is also needed to keep the Higgs total width as the SM value.
118767477
Testing origin of neutrino masses at the CERN Large Hadron Collider
119188638
GeV Majorana neutrinos in top-quark decay at the LHC
We explore the $\ensuremath{\Delta}L=2$ same-sign dilepton signal from top-quark decay via a Majorana neutrino at the LHC in the top anti-top pair production samples. The signature is same-sign dilepton plus multijets with no significant missing energy. The most optimistic region lies where the Majorana neutrino mass is between $15\char21{}65\text{ }\text{ }\mathrm{GeV}$. For $300\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ integrated luminosity, it is possible to probe ${S}_{ij}$, the effective mixing parameter, to $\mathcal{O}({10}^{\ensuremath{-}5})$.
9128580
BaBar forward endcap upgrade
The muon and neutral hadron detector (instrumented flux return or IFR) in the forward endcap of the BaBar detector at SLAC was upgraded by the installation of a new generation of resistive plate chambers (RPCs) and by increasing the absorber. The chamber replacement was made necessary by the rapid aging and efficiency loss of the original BaBar RPCs. Based on our experience with those original RPCs and 24 RPCs with thinner linseed oil treatments, improvements in the design, construction, and testing of the new generation RPCs were implemented and are described in detail.
117044754
Natural Quark Mass Matrices