118676148
Can Up FCNC solve the $\Delta A_{CP}$ puzzle?
We investigate the attempt using flavor violation gauge interaction in the up sector to explain the LHCb recently observed large $\Delta A_{CP}$ ($A_{CP}(D^{0}\to K^{+}K^{-})-A_{CP}(D^{0}\to \pi^{+}\pi^{-})$). We study an Abelian model that only right-handed up quarks is charged under it and the 1-3 coupling is maximized. The simultaneous 1-3 2-3 mixing is realized by a quark mixing of 1-2 generation. Given the easy identification of top quark, the model can be directly tested by $\Delta F=1$ and $\Delta F=2$ processes at the hadron colliders as associated top production $g c \to t Z^{\prime}$ or same-sign top scattering $u u\to t t$. The direct search bounds are still consistent with the assumption that $ut$ and $ct$ couplings are equal but the same-sign top scattering bound is expected to be reached very soon. However, since there is no CKM-like suppression, the corresponding parameter space for generating $\Delta A_{CP}$ is completely excluded by the $D^{0}-\bar{D}^{0}$ mixing. We conclude that the up FCNC type models cannot explain the $\Delta A_{CP}$ while to be consistent with the $D^{0}-\bar{D}^{0}$ mixing constraint at the same time. On the other hand, a model as SM with fourth family extension has better chance to explain the large $\Delta A_{CP}$ consistently.
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.
118412591
Stabilizing the axion and a natural solution to the mu problem of supersymmetry
The axion solution to the strong CP problem makes use of a global Peccei-Quinn (PQ) U(1) symmetry which is susceptible to violations from quantum gravitational effects. We show explicitly how discrete gauge symmetries can protect the axion from such violations. PQ symmetry emerges as an accidental global symmetry from discrete gauge symmetries which are subgroups of the anomalous U(1) of string origin. We also show how the Dine-Fischler-Srednicki-Zhitnitsky (DFSZ) axion model provides a natural solution to mu problem of supersymmetry as mu ~ M_{SUSY} ~ M^2_{PQ}/M_{Pl}.
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 $\mathcal{O}({10}^{\ensuremath{-}5})$.
118767477
Testing origin of neutrino masses at the CERN Large Hadron Collider
122736097
A Study of Missing Transverse Energy in Minimum Bias Events with In-time Pile-up at The Large Hadron Collider using The ATLAS Detector and $\sqrt{s}$=7 TeV Proton-Proton Collision Data
110466342
Performance and Aging Studies of BaBar Resistive Plate Chambers
The BaBar detector is currently operating nearly 200 Resistive Plate Chambers (RPCs), constructed as part of an upgrade of the forward endcap muon detector in 2002. Although the average RPC efficiency remains high, numerous changes in the RPC performance (increased currents and rates) have been observed. A few of the highest rate RPCs have suffered efficiency losses of more than 15%. Several types of efficiency loss have been observed. Tests with humidified gas have shown that some of the lost efficiency is recoverable. However, efficiency losses in the highest rate regions have not yet improved with humid gases.