Tuesday, September 13, 2011

More Experiments, No New Physics.

New lower bounds have been set for various forms of beyond the Standard Model physics at LHC at the 95% confidence level based on dijet observations:

Excited quarks q* = 2.07 TeV
Randall-Meade Quantum Black Holes (for n=6) = 3.37 TeV
Axigluon = 2.01 TeV
Color Octet Scalar = 1.71 TeV

There are also new SUSY limits: "squark masses below 1.1 TeV are excluded at 95% CL. Gluino masses below 1.1 TeV are also ruled out at 95% CL for values of the universal scalar mass parameter below 500 GeV."

And, "Lepton flavor violations in charged lepton give good signatures for the new physics. We review recent searches for lepton flavor violation in tau decays at B-factories. In these searches, optimization for background reduction is important to obtain high sensitivity. No evidence for these decays is observed and 90% confidence level upper limits have been set on the branching fractions at the O(10^{-8}) level."

Lepton-flavor-violating (LFV) decays of charged leptons are expected to have negligible probability even including neutrino oscillations in the Standard Model (SM). The branching fractions of
τμγ including SM+ neutrino oscillations are less than O

However, many extensions of SM, such as supersymmetry (SUSY) and large extra dimensions, predict enhanced LFV decays with branching fractions close to the current experimental sensitivity. With certain combinations of new physics parameters, the branching fractions for LFV
τ decays can be as high as

7, which is already accessible in high-statistics B-factory experiments. Therefore, an observation of LFV decay will be a clear signature for new physics beyond the SM.

τ leptons are expected to be coupled strongly with new physics and have many
possible LFV decay modes due to their large mass. Therefore,
τ leptons are ideal objects to search for the LFV decays.  SUSY, which is the most popular candidate among New Physics (NP) models, induces naturally LFV at one-loop through the scalar lepton mixing.

If a typical SUSY mass is larger than1 TeV, processes via one-loop contributions with SUSY particles are suppressed. When scalar leptons are much heavier than weak scale, LFV occurs via a Higgs-mediated LFV mechanism.

Finally, another weird relationship:

it has been noted that the solar and atmospheric neutrino mixing
angles 12 and 23 measured from neutrino oscillation experiments and the quark mixing angles q12 and q23 reveal a surprising relation

12 + q12 ≃ 23 + q23 ≃ 45◦, (3)

which is satisfied by the experimental results

12 + q12 = 47.4 ± 1.1 􀀀+3.3−3.0 ◦ and 23 + q23 =45.2+4.2−2.9 􀀀+10.8−7.4 ◦

to within a few percent accuracy [1, 2]. This quark-lepton complementarity(QLC) relation (3) has been interpreted as an evidence for certain quark-lepton symmetry or quark-lepton unification as shown in [6]. In the light of the QLC, it is still experimentally allowed for the neutrino mixing matrix to be composed of a CKM-like matrix and maximal mixing matrices as shown in [7, 8].

In [7], it is shown in the framework of supersymmetric standard model that different combination of the mixing matrix leads to different prediction for the branching ratios of lepton flavor violating decays li → lj, which makes it possible to discriminate the possible compositions. Among possible compositions, in this paper, we consider the following parametrization:

U(PMNS) = R(32) (pi/4) U(†CKM) R(21) (pi/ 4),

(4) where UCKM denotes the CKM mixing matrix. The reason why we consider this particular parametrization for the QLC relation is that it is well compared and has similar merit to the triminimal parametrization so that we can simply examine if the effects of deviations from the TB mixing can be compatible with the QLC relation or not by investigating a few observables presented by simple formulas. The parametrization given by Eq.(4) can be obtained from the grand unification or quark-lepton symmetry as shown in [7].

The concept was noted here in 1990 and applied, for example, here to make neutrino mixing predictions.

Thus, it may be that the four parameters each that go into the CKM and PMNS matrixes may really be a single set of four parameters, and if suspicions that mass ratios and related to the CKM and PMNS matrixes, then those four parameters could explain the mass matrixes of the fermions as well (plus a base mass from which all other mass could be derived). See, e.g. here and here, and here.

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