118767477
Testing origin of neutrino masses at the CERN Large Hadron Collider
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.
54180574
Inverse seesaw in supersymmetry
Abstract We study a mechanism where tiny neutrino masses arise only from radiative contribution in a supersymmetric model. Without tuning the Higgs vev or Yukawa coupling, the tree-level light neutrino mass is rotated away by introducing a new singlet neutrino s L that forms a Dirac mass term with the right-handed neutrino n R in each generation. Even with the U ( 1 ) Lep lepton number violation term as non-zero right-handed Majorana neutrino mass M R n R c ¯ n R , the lightest neutrino remains massless at tree level due to an approximate symmetry. Consequently, tiny neutrino masses then only arise from radiative contributions and the right-handed neutrino Majorana mass M R can be at O ( keV ) to give rise to the correct light neutrino mass at O ( eV ) . Supersymmetry ensures that the Majorana neutrino masses M R n R c ¯ n R and M R ⁎ s L c ¯ s L are not generated simultaneously.
119611263
Pair production of doubly charged scalars: Neutrino mass constraints and signals at the CERN LHC
We study the pair production of doubly charged Higgs bosons at the CERN Large Hadron Collider (LHC), assuming the doubly charged Higgs to be part of an SU(2){sub L} triplet which generates Majorana masses for left-handed neutrinos. Such pair production has the advantage that it is not constrained by the triplet vacuum expectation value, which tends to make the single production rate rather small. We point out that, in addition to the Drell-Yan production mechanism, two-photon processes also contribute to H{sup ++}H{sup --} production at a level comparable to the QCD corrections to the Drell-Yan channel. Decays of the doubly charged Higgs into both the l{sup +}l{sup +} and W{sup +}W{sup +} modes are studied in detail to optimize the signal observation over the backgrounds. Doubly charged scalars should be observable at the LHC with 300 fb{sup -1} integrated luminosity in the l{sup {+-}}l{sup {+-}} channel up to the mass range of 1 TeV even with a branching fraction of about 60%, and in the W{sup {+-}}W{sup {+-}} channel up to a mass of 700 GeV. Such a doubly charged Higgs, if it is a member of a triplet that generates neutrino masses, cannot be long-lived on the scale ofmore » collider detectors although it might lead to a displaced secondary vertex during its decay if it is lighter than about 250 GeV.« less
118938933
Flavor dependence of annihilation parameters in QCD factorization
For $B_{d,s} \to \pi^\mp K^\pm$ and $K^{(\ast)} K^{(\ast)}$ decays, the flavor symmetry breaking effects may be particularly small since the final state interactions should be the same between the corresponding $B_d$ and $B_s$ decays due to the charge conjugation symmetry of the final states. This is consistent with the newly measured direct CP asymmetry of $B_s \to \pi^+ K^-$. These decays are thus supposed to be important in testing the Standard Model and in probing new physics effects. However, the observation of pure annihilation decay $B_s \to \pi^+ \pi^-$ appears to imply a large annihilation scenario with $\rho_A \sim 3$, in contrast to the case of $\rho_A \sim 1$ in $B_{u,d}$ decays in the framework of QCD factorization. This seems to indicate unexpectedly large flavor symmetry breaking effects between the annihilation amplitudes of $B_s$ and $B_{u,d}$ decays. This apparent contradiction could be resolved by noticing that there is a priori no reason to justify the common practice of assuming the universality of annihilation parameters for different Dirac structures of effective operators. We then argue that, for $B_{d,s} \to \pi^\mp K^\pm$ decays, the flavor symmetry breaking effects of annihilation amplitudes have all been included in the initial state decay constants and are thus small. But the flavor symmetry breaking effects in $B_{d,s} \to K^{(\ast)} K^{(\ast)}$ decays are likely to be much larger, as part of the annihilation topologies of $B_s \to K K$ decay could be related to $B_s \to \pi^+ \pi^-$ decay. Therefore when new physics effects are searched for in these decay channels, care must be taken to consider the potentially large flavor symmetry breaking effects in more details.
118409650
NLSP gluino search at the Tevatron and early LHC
We investigate the collider phenomenology of gluino-bino co-annihilation scenario both at the Tevatron and 7 TeV LHC. This scenario can be realized, for example, in a class of realistic supersymmetric models with non-universal gaugino masses and t − b−τ Yukawa unification. The NLSP gluino and LSP bino should be nearly degenerate in mass, so that the typical gluino search channels involving leptons or hard jets are not available. Consequently, the gluino can be lighter than various bounds on its mass from direct searches. We propose a new search for NLSP gluino involving multi-b final states, arising from the three-body decay $ \tilde{g} \to b\overline b \tilde{\chi }_1^0 $. We identify two realistic models with gluino mass of around 300 GeV for which the three-body decay is dominant, and show that a 4.5 σ observation sensitivity can be achieved at the Tevatron with an integrated luminosity of 10 fb−1. For the 7TeV LHC with 50 pb−1 of integrated luminosity, the number of signal events for the two models is $ \mathcal{O}\left( {10} \right) $, to be compared with negligible SM background events.
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