There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

저작근 근전도에 관한 정상교합자와 ii급 부정교합자의 비교 연구

We present a measurement of form-factor-independent angular observables in the decay B-0 -> K*(892)(0)mu(+)mu(-). The analysis is based on a data sample corresponding to an integrated luminosity of 1.0 fb(-1), collected by the LHCb experiment in pp collisions at a center-of-mass energy of 7 TeV. Four observables are measured in six bins of the dimuon invariant mass squared q(2) in the range 0.1 < q(2) < 19.0 GeV2/c(4). Agreement with recent theoretical predictions of the standard model is found for 23 of the 24 measurements. A local discrepancy, corresponding to 3.7 Gaussian standard deviations is observed in one q(2) bin for one of the observables. Considering the 24 measurements as independent, the probability to observe such a discrepancy, or larger, in one is 0.5%.

Measurement of form-factor-independent observables in the decay B0→K*0μ+μ-

A test of lepton universality, performed by measuring the ratio of the branching fractions of the $B^{0} \rightarrow K^{*0}\mu^{+}\mu^{-}$ and $B^{0} \rightarrow K^{*0}e^{+}e^{-}$ decays, $R_{K^{*0}}$, is presented The $K^{*0}$ meson is reconstructed in the final state $K^{+}\pi^{-}$, which is required to have an invariant mass within 100$\mathrm{\,MeV}c^2$ of the known $K^{*}(892)^{0}$ mass The analysis is performed using proton-proton collision data, corresponding to an integrated luminosity of about 3$\mathrm{\,fb}^{-1}$, collected by the LHCb experiment at centre-of-mass energies of 7 and 8$\mathrm{\,TeV}$ The ratio is measured in two regions of the dilepton invariant mass squared, $q^{2}$, to be \begin{eqnarray*} R_{K^{*0}} = \begin{cases} 066~^{+~011}_{-~007}\mathrm{\,(stat)} \pm 003\mathrm{\,(syst)} & \textrm{for } 0045 < q^{2} < 11~\mathrm{\,GeV^2}c^4 \, , \\ 069~^{+~011}_{-~007}\mathrm{\,(stat)} \pm 005\mathrm{\,(syst)} & \textrm{for } 11\phantom{00} < q^{2} < 60~\mathrm{\,GeV^2}c^4 \,  \end{cases} \end{eqnarray*} The corresponding 954\% confidence level intervals are $[052, 089]$ and $[053, 094]$ The results, which represent the most precise measurements of $R_{K^{*0}}$ to date, are compatible with the Standard Model expectations at the level of 21--23 and 24--25 standard deviations in the two $q^{2}$ regions, respectively

/pdf/test-of-lepton-universality-with-b-0-rightarrow-k-0-ell-ell-4sdv0vmzwy.pdf

Test of lepton universality with $B^{0} \rightarrow K^{*0}\ell^{+}\ell^{-}$ decays

The rare decay B → K*(→ Kπ)μ+μ− is regarded as one of the crucial channels for B physics as the polarization of the K* allows a precise angular reconstruction resulting in many observables that offer new important tests of the Standard Model and its extensions. These angular observables can be expressed in terms of CP-conserving and CP-violating quantities which we study in terms of the full form factors calculated from QCD sum rules on the light-cone, including QCD factorization corrections. We investigate all observables in the context of the Standard Model and various New Physics models, in particular the Littlest Higgs model with T-parity and various MSSM scenarios, identifying those observables with small to moderate dependence on hadronic quantities and large impact of New Physics. One important result of our studies is that new CP-violating phases will produce clean signals in CP-violating asymmetries. We also identify a number of correlations between various observables which will allow a clear distinction between different New Physics scenarios.

Symmetries and Asymmetries of B -> K* mu+ mu- Decays in the Standard Model and Beyond

Following the updated measurement of the lepton flavour universality (LFU) ratio $$R_K$$ in $$B\rightarrow K\ell \ell $$ decays by LHCb, as well as a number of further measurements, e.g. $$R_{K^*}$$ by Belle and $$B_s \rightarrow \mu \mu $$ by ATLAS, we analyse the global status of new physics in $$b\rightarrow s$$ transitions in the weak effective theory at the b-quark scale, in the Standard Model effective theory above the electroweak scale, and in simplified models of new physics. We find that the data continues to strongly prefer a solution with new physics in semi-leptonic Wilson coefficients. A purely muonic contribution to the combination $$C_9 = -C_{10}$$, well suited to UV-complete interpretations, is now favoured with respect to a muonic contribution to $$C_9$$ only. An even better fit is obtained by allowing an additional LFU shift in $$C_9$$. Such a shift can be renormalization-group induced from four-fermion operators above the electroweak scale, in particular from semi-tauonic operators, able to account for the potential discrepancies in $$b \rightarrow c$$ transitions. This scenario is naturally realized in the simplified $$U_1$$ leptoquark model. We also analyse simplified models where a LFU effect in $$b\rightarrow s\ell \ell $$ is induced radiatively from four-quark operators and show that such a setup is on the brink of exclusion by LHC di-jet resonance searches.

/pdf/b-decay-discrepancies-after-moriond-2019-29574tu7zz.pdf

B-decay discrepancies after Moriond 2019

Rather than sticking to the full U(3)3 approximate symmetry normally invoked in Minimal Flavour Violation, we analyze the consequences on the current flavour data of a suitably broken U(2)3 symmetry acting on the first two generations of quarks and squarks. A definite correlation emerges between the ΔF=2 amplitudes $\mathcal{M}( K^{0} \to \bar{K}^{0} )$
 , $\mathcal{M}( B_{d} \to \bar{B}_{d} )$
 and $\mathcal{M}( B_{s} \to \bar{B}_{s} )$
 , which can resolve the current tension between $\mathcal{M}( K^{0} \to \bar{K}^{0} )$
 and $\mathcal{M}( B_{d} \to \bar{B}_{d} )$
 , while predicting $\mathcal{M}( B_{s}\to \bar{B}_{s} )$
 . In particular, the CP violating asymmetry in B
 s
 →ψφ is predicted to be positive S
 ψφ
 =0.12±0.05 and above its Standard Model value (S
 ψφ
 =0.041±0.002). The preferred region for the gluino and the left-handed sbottom masses is below about 1÷1.5 TeV. An existence proof of a dynamical model realizing the U(2)3 picture is outlined.

U(2) and minimal flavour violation in supersymmetry

Recent experimental results on angular observables in the rare decay B→K
 ∗
 μ
 +
 μ
 − show significant deviations from Standard Model predictions. We investigate the possibility that these deviations are due to new physics. Combining all relevant data on b→s rare decays, we show that a consistent explanation of most anomalies can be obtained by new physics contributing simultaneously to the semi-leptonic vector operator O
 9 and its chirality-flipped counterpart $O_{9}'$
 . A partial explanation is possible with new physics in O
 9 or in dipole operators only. We study in detail the implications for models of new physics, in particular the minimal supersymmetric standard model, models with partial compositeness and generic models with flavour-changing Z′ bosons. In all considered models, contributions to B→K
 ∗
 μ
 +
 μ
 − of the preferred size imply a spectrum close to the TeV scale. We stress that measurements of CP asymmetries in B→K
 ∗
 μ
 +
 μ
 − could provide valuable information to narrow down possible new physics explanations.

New physics in B→K ∗ μμ?

The quark sector of the Standard Model exhibits an approximate U(2)3 flavour symmetry. This symmetry, broken in specific directions dictated by minimality, can explain the success of the Cabibbo-Kobayashi-Maskawa picture of flavour mixing and CP violation, confirmed by the data so far, while allowing for observable deviations from it, as expected in most models of ElectroWeak Symmetry Breaking. Building on previous work in the specific context of supersymmetry, we analyze the expected effects and we quantify the current bounds in a general Effective Field Theory framework. As a further relevant example we then show how the U(2)3 symmetry and its breaking can be implemented in a generic composite Higgs model and we make a first analysis of its peculiar consequences. We also discuss how some partial extension of U(2)3 to the lepton sector can arise, both in general and in composite Higgs models. An optimistic though conceivable interpretation of the considerations developed in this paper gives reasons to think that new physics searches in the flavour sector may be about to explore an interesting realm of phenomena.

David M. Straub

Papers

Symmetries and Asymmetries of B -> K* mu+ mu- Decays in the Standard Model and Beyond

B-decay discrepancies after Moriond 2019

U(2) and minimal flavour violation in supersymmetry

New physics in B→K ∗ μμ?

Flavour physics from an approximate U(2)^3 symmetry