We use a sample of 384 million BBbar decays collected with the Babar detector at the PEP-II asymmetric e+e- storage ring to study the flavor-changing neutral current decays B->K(*)l+l-, where l+l- is either e+e- or mu+mu-. We present measurements in two dilepton mass bins, one below the J/psi resonance and the other above, of the lepton forward-backward asymmetry AFB and the longitudinal K* polarization FL in B->K*l+l-, along with isospin rate asymmetries in B->K*l+l- and B->Kl+l- final states.
Measurement of CP Asymmetries and Branching Fractions in B0 -> pi+ pi-, B0 -> K+ pi-, B0 -> pi0 pi0, B0 -> K0 pi0 and Isospin Analysis of B -> pi pi Decays
我们提出了在衰变B 0-> pi+ pi-，B 0-> K+ pi-，B 0-> pi 0 pi 0和B 0-> K 0 pi 0中CP破坏不对称性和分支分数的改进测量的初步结果。此更新包括在SLAC的非对称PEP-II B介子工厂的BaBar实验在Y（4S）共振处获得的所有数据，对应于4.67 +- 5百万个BBbar对。我们发现Spipi = -0.68 +-0.10 +-0.03，Cpipi = -0.25 +-0.08 +-0.02，AKpi = -0.107 +-0.016 +0.006-0.004，Cpi 0 pi 0 = -0.43 +-0.26 +-0.05，BF（B 0-> pi 0 pi 0）=（1.83 +- 0.21 +- 0.13）x 10^-6，BF（B 0-> K 0 pi 0）=（10.1 +- 0.6 +- 0.4）x 10^-6，其中第一个误差是统计误差，第二个误差是系统误差。我们观察到CP破坏，在B 0-> pi+ pi-中显著性为6.7 sigma，在B 0-> K+ pi-中显著性为6.1 sigma。对幺正三角角α的约束由所有B -> pipi速率和不对称性之间的同位旋关系确定。
We compute the isospin asymmetries in $B \to (K^*,ρ) γ$ and $B\to (K,K^*,ρ) l^+l^-$ for low lepton pair invariant mass $q^2$, within the Standard Model (SM) and beyond the SM (BSM) in a generic dimension six operator basis. Within the SM the CP-averaged isospin asymmetries for $B \to (K,K^*,ρ) ll$, between $1{\rm GeV}^2 \leq q^2 \leq 4m_c^2$, are predicted to be small (below 1.5%) though with significant cancellation. In the SM the non-CP averaged asymmetries for $B \to ρll$ deviate by $\approx \pm 5%$ from the CP-averaged ones. We provide physical arguments, based on resonances, of why isospi…
本文给出了B -> K（*）1 + 1-稀有衰变的新的BABAR测量结果，包括分支分数、同位旋不对称性、直接CP破坏和J/psi共振以上双轻子质量的轻子味普适性.在K1 + 1-和K* 1 + 1-衰变中都观察到出乎意料的大的同位旋不对称性。对于Kl +l-和K* l+l-的组合数据，发现与SM的预测有3.9 σ的显著偏差.此外，最近报道了BABAR在B -> K* l+l-的角分析结果，其中测量了J/psi共振以下和以上的双轻子质量的K* 纵向极化和轻子前后不对称性.最后，总结了最近从BABAR搜索B -> pil +1- $ from Belle and B -> K(*) nu anti nu$的结果。
We study the lepton forward-backward asymmetry AFB and the longitudinal K* polarization FL, as well as an observable P2 derived from them, in the rare decays B->K*l+l-, where l+l- is either e+e- or mu+mu-, using the full sample of 471 million BBbar events collected at the Upsilon(4S) resonance with the Babar detector at the PEP-II e+e- collider. We separately fit and report results for the B+->K*+l+l- and B0->K*0l+l- final states, as well as their combination B->K*l+l-, in five disjoint dilepton mass-squared bins. An angular analysis of B+->K*+l+l- decays is presented here for the first time.
We report the first evidence for isospin violation in $B \to K^* γ$ and the first measurement of difference of $CP$ asymmetries between $B^+ \to K^{*+} γ$ and $B^0 \to K^{*0} γ$. This analysis is based on the data sample containing $772 \times 10^6 B\bar{B}$ pairs that was collected with the Belle detector at the KEKB energy-asymmetric $e^+ e^-$ collider. We find evidence for the isospin violation with a significance of 3.1$σ$, $Δ_{0+} = (+6.2 \pm 1.5 ({\rm stat.}) \pm 0.6 ({\rm syst.}) \pm 1.2 (f_{+-}/f_{00}))$\%, where the third uncertainty is due to the uncertainty on the fraction of $B^+B^…
We introduce a set of observables representing angular distribution asymmetries, which can be viewed as a generalization of the forward-backward asymmetry of angular distributions, and can be used as an effective tool to search for $C\!P$ violation in three-body decays of bottom and charmed baryons. We propose to search for such $C\!P$ asymmetries (1) in decays with $Λ^0$, $Σ^\pm$, or $Λ_c^+$ involved, such as $Λ_b\to Λ^0 D$ and $Λ_b\toΛ^0ρ(770)^0$; and (2) in three-body decays of bottom baryons with opposite parity intermediate resonances involved. Typical examples include $Ξ_b^-\to p K^- K^-…
The approximate symmetry of the strong interactions under isospin transformations is among the most precise tools available to control hadronic matrix elements. It is crucial in extracting fundamental parameters, but also provides avenues for the search of phenomena beyond the Standard Model. The precision of the resulting predictions requires special care when determining the quantities they are to be tested with. Specifically, in the extraction of branching ratios often isospin symmetry is assumed at one point or another implicitly, implying a significant bias for precision analyses. We extr…
Single decay-lepton angular distributions in polarized e+e- --> t tbar and simple angular asymmetries as a measure of CP-violating top dipole couplings
We study the spin correlations to probe time-reversal~(T) asymmetries in the decays of $Λ_b \to ΛV ~(V=ϕ, ρ^0, ω, K^{*0})$. The eigenstates of the T-odd operators are obtained along with definite angular momenta. We obtain the T-odd spin correlations from the complex phases among the helicity amplitudes. We give the angular distributions of $Λ_b \to Λ(\to p π^-)V(\to PP')$ and show the corresponding spin correlations, where $P^{(\prime)}$ are the pseudoscalar mesons. Due to the helicity conservation of the $s$ quark in $Λ$, we deduce that the polarization asymmetries of $Λ$ are close to $-1$. …
We examine the validity of the generalized factorization method and calculate the angular correlations in the charmful three-body baryonic decays of $\bar B^0\to Λ\bar p D^{(*)+}$. With the timelike baryonic form factors newly extracted from the measured baryonic $B$ decays, we obtain ${\cal B}(\bar B^0\to Λ\bar p D^+,Λ\bar p D^{*+})=(1.85\pm 0.30,2.75\pm 0.24)\times 10^{-5}$ to agree with the recent data from the BELLE Collaboration, which demonstrates that the theoretical approach based on the factorization still works well. For the angular distribution asymmetries, we find ${\cal A}_θ(\bar …
A novel approach to reconstruct inclusive $\bar{B} \to X_{s} \ell^{+}\ell^{-}$ decays is presented. The method relies on isopsin symmetry to extrapolate the semi-inclusive signature $X_{b}\to K^{+} \ell^{+}\ell^{-} X$ to the fully inclusive rate in $B^{+}$ and $B^{0}$ decays. We investigate the possibility to measure branching fractions and other observables such as lepton universality ratios and $CP$ asymmetries. As a proof of concept, fast simulation is used to compare the $X_{b}\to K^{+} \ell^{+}\ell^{-} X$ signature with a fully inclusive approach. Several experimental advantages are seen …
The semi-leptonic baryonic $b\to s$ decay, $Λ_b\rightarrow Λ\ell^+\ell^-$, has been studied and new angular observables and asymmetries have been proposed which can test the presence of new physics beyond the standard model.
Using the helicity amplitude technique, we derive differential decay widths and angular distributions for the decay cascade $D\to K_{1}(1270,1400)\ell^+ν_{\ell}\to (Kππ)\ell^+ν_{\ell} (\ell=e,μ)$, in which the electron and muon mass is explicitly included. Using a set of phenomenological results for $D\to K_1$ form factors, we calculate partial decay widths and branching fractions for $D^0\to K_1^-\ell^+ν_{\ell}$ and $D^+\to K_1^0\ell^+ν_{\ell}$, but find that results for ${\cal B}(D\to K_1(1270)e^+ν_{e})$ are larger than recent BESIII measurements by about a factor 1.5. We further demonstrate…
We report measurements of isospin asymmetry $Δ_{0-}$ and difference of direct $CP$ asymmetries $ΔA_{CP}$ between charged and neutral $B \to X_s γ$ decays. This analysis is based on the data sample containing $772 \times 10^6 B\bar{B}$ pairs that was collected with the Belle detector at the KEKB energy-asymmetric $e^+ e^-$ collider. Using a sum-of-exclusive technique with invariant $X_s$ mass up to 2.8~GeV/$c^2$, we obtain $Δ_{0-} = \bigl[-0.48 \pm 1.49 {\rm (stat.)} \pm 0.97 {\rm (syst.)} \pm 1.15 {(f_{+-}/f_{00})}\bigr]$\% and $ΔA_{CP} = \bigl[+3.69 \pm 2.65 {\rm (stat.)} \pm 0.76{\rm (syst.)…
We analyze patterns from CP-violating new physics (NP) in hadronic and semileptonic rare charm $\vert Δc \vert=\vert Δu\vert=1$ transitions. Observation of direct CP-violation in hadronic decays, as in $ΔA_{\text{CP}}$, provides opportunities for $c \to u \,\ell^+ \ell^-$, $\ell=e,μ$ transitions, and vice versa. For the concrete case of flavorful, anomaly-free $Z^\prime$-models a NP-interpretation of $ΔA_{\text{CP}}$ suggests measurable CP-asymmetries in semileptonic decays such as $D \to π\, \ell^+ \ell^-$ or $D \to ππ\, \ell^+ \ell^-$. Conversely, an observation of CP-violation in $c \to u\,…
Improving the sensitivity to CP-violation in the Higgs sector is one of the pillars of the precision Higgs programme at the Large Hadron Collider. We present a simple method that allows CP-sensitive observables to be directly constructed from the output of neural networks. We show that these observables have improved sensitivity to CP-violating effects in the production and decay of the Higgs boson, when compared to the use of traditional angular observables alone. The kinematic correlations identified by the neural networks can be used to design new analyses based on angular observables, with…
We perform a phenomenological analysis of the $\cos 2 ϕ$ azimuthal asymmetry in virtual photon plus jet production induced by the linear polarization of gluons in unpolarized $pA$ collisions. Although the linearly polarized gluon distribution becomes maximal at small $x$, TMD evolutionleads to a Sudakov suppression of the asymmetry with increasing invariant mass of the $γ^*$-jet pair. Employing a small-$x$ model input distribution, the asymmetry is found to be strongly suppressed under TMD evolution, but still remains sufficiently large to be measurable in the typical kinematical region access…
We study angular observables in the $e^+e^-\to Z H\to \ell^+ \ell^-\,b\bar{b}$ channel at future circular $e^+ e^-$ colliders such as CEPC and FCC-ee. Taking into account the impact of realistic cut acceptance and detector effects, we forecast the precision of six angular asymmetries at CEPC (FCC-ee) with center-of-mass energy $\sqrt{s} =$ 240 GeV and 5 (30) ${\rm ab}^{-1}$ integrated luminosity. We then determine the projected sensitivity to a range of operators relevant for the Higgs-strahlung process in the dimension-6 Higgs EFT. Our results show that angular observables provide complementa…
