Kπ Decay Research Articles

K* dynamics in heavy ion collisions

The dynamics of strange vector meson resonances (K * and K *) is investigated within the Parton-Hadron-String Dynamics (PHSD) transport approach. We present the time evolution of the production of K *− resonances from the QGP phase by quark fusion as well as from hadronic sources. We also give a brief overview of the modification of the K * through Kπ decay and K*N interaction in a hot and dense nuclear medium.

Dalitz plot analysis ofηc→K+K−ηandηc→K+K−π0in two-photon interactions

We study the processes γγ→K+K−η and γγ→K+K−π0 using a data sample of 519 fb−1 recorded with the BABAR detector operating at the SLAC PEP-II asymmetric-energy e+e− collider at center-of-mass energies at and near the ϒ(nS) (n=2,3,4) resonances. We observe ηc→K+K−π0 and ηc→K+K−η decays, measure their relative branching fraction, and perform a Dalitz plot analysis for each decay. We observe the K0*(1430)→Kη decay and measure its branching fraction relative to the Kπ decay mode to be R(K0*(1430))=B(K0*(1430)→Kη)B(K0*(1430)→Kπ)=0.092±0.025−0.025+0.010. The ηc→K+K−η and K0*(1430)→Kη results correspond to the first observations of these channels. The data also show evidence for ηc(2S)→K+K−π0 and first evidence for ηc(2S)→K+K−η.6 MoreReceived 27 March 2014DOI:https://doi.org/10.1103/PhysRevD.89.112004© 2014 American Physical Society

Measurement of strong phase in D0 → Kπ decay at BESIII

Based on 2.92 fb-1 of e+e- collision data collected with the BESIII detector at [Formula: see text] GeV, we measured the asymmetry [Formula: see text] of the branching fractions of DCP± → K-π+ (DCP± are the CP-odd and CP-even eigenstates) to be [Formula: see text]. [Formula: see text] is used to extract the strong phase difference δKπ between the doubly Cabibbo-suppressed process [Formula: see text] and Cabibbo-favored D0 → K-π+. By taking inputs of other parameters in world measurements, we obtain cos δKπ = 1.03 ± 0.12 ± 0.04 ± 0.01. This is the most accurate result of cos δKπ to date and can improve the world constrains on the mixing parameters and on γ/ϕ3 in the CKM matrix.

CHARM PHYSICS AT BESIII

We present a selection of recent charm results from the BESIII Collaboration. The topics include measurements of strong phase in D0 → Kπ decay and yCP, decay constant fD+ measurement from D+ → μ+ν, form-factors measurement in D0 → K−e+ν, π−e+ν, Dalitz plot analysis of [Formula: see text], search for D0 → γγ rare decay and Ds decays.

Measurements of branching fractions and directCPasymmetries forB→Kπ,B→ππandB→KKdecays

We report measurements of the branching fractions and direct CP asymmetries (ACP) for B→Kπ, ππ and KK decays (but not π0π0) based on the final data sample of 772×106 BB¯ pairs collected at the Υ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e− collider. We set a 90% confidence-level upper limit for K+K− at 2.0×10−7; all other decays are observed with branching fractions ranging from 10−6 to 10−5. In the B0/B¯0→K±π∓ mode, we confirm Belle’s previously reported large ACP with a value of −0.069±0.014±0.007 and a significance of 4.4σ. For all other flavor-specific modes, we find ACP values consistent with zero, including ACP(K+π0)=+0.043±0.024±0.007 with 1.8σ significance. The difference of CP asymmetry between B±→K±π0 and B0/B¯0→K±π∓ is found to be ΔAKπ≡ACP(K+π0)−ACP(K+π−)=+0.112±0.027±0.007 with 4.0σ significance. We also calculate the ratios of partial widths for the B→Kπ decays. Using our results, we test the validity of the sum rule ACP(K+π−)+ACP(K0π+)Γ(K0π+)Γ(K+π−)−ACP(K+π0)2Γ(K+π0)Γ(K+π−)−ACP(K0π0)2Γ(K0π0)Γ(K+π−)=0 and obtain a sum of −0.270±0.132±0.060 with 1.9σ significance.Received 4 October 2012DOI:https://doi.org/10.1103/PhysRevD.87.031103© 2013 American Physical Society

The [formula omitted] puzzle and the bulk Randall–Sundrum model

The recent measurements of the direct CP asymmetries (ACP) in the penguin-dominated B→Kπ decays show some discrepancy from the standard model (SM) prediction. While ACP of B+→π0K+ and that of B0→π−K+ in the naive estimate of the SM are expected to have very similar values, their experimental data are of the opposite sign and different magnitudes. We study the effects of the custodial bulk Randall–Sundrum model on this ACP. In this model, the misalignment of the five-dimensional (5D) Yukawa interactions to the 5D bulk gauge interactions in flavor space leads to tree-level flavor-changing neutral current by the Kaluza–Klein gauge bosons. In a large portion of the parameter space of this model, the observed non-zero ACP(B+→π0K+)−ACP(B0→π−K+) can be explained only with low Kaluza–Klein mass scale MKK around 1 TeV. Rather extreme parameters is required to explain it with MKK≃3 TeV. The new contributions to well-measured branching ratios of B→Kπ decays are also shown to be suppressed.

Phenomenological studies on D0-D0 mixing and strong phase difference

Most recently, both BABAR and Belle experiments found evidences of neutral D mixing. In this paper, we discuss the constraints on the strong phase difference in D0→Kπ decay from the measurements of the mixing parameters y′, yCP, and x at the B-factories. With CP tag technique at ψ（3770） peak, the extraction of the strong phase difference at BES-Ⅲ is discussed. The sensitivity of the measurement of the mixing parameter y is estimated in BES-Ⅲ experiment at ψ（3770） peak. Finally, we make an estimate on the measurements of mixing rate RM.

EXTRACTING THE CKM PHASE ANGLE γ(≡ φ3) FROM ISOSPIN ANALYSIS IN B → Kπ DECAY

We propose a new method to extract the CKM phase angle γ(≡ φ3) from the isospin analysis in B → Kπ decays only. Unlike previously proposed methods, we do not employ flavor SU (3) symmetry, so that this method is free from the hadronic uncertainty coming from the SU (3) breaking effect. Neither we adopt any Dalitz-plot analysis, which may involve multiple strong phases and large final state interactions. Since no theoretical assumption, except the isospin relations, is imposed on B → Kπ decays, this method will work well, regardless of possible new physics effects unless the isospin relations do not hold. Since the mixing induced CP asymmetry SKSπ0 plays a crucial role in this method, more precise measurement on SKSπ0 in future experiments will be greatly helpful to extract γ accurately. Using current experimental data for B → Kπ including SKSπ0, we extract γ within [Formula: see text] or [Formula: see text].

IS THERE ANY PUZZLE OF NEW PHYSICS IN B → Kπ DECAYS?

Due to re-parametrization invariance of decay amplitudes, any single new physics (NP) amplitude arising through either the electro-weak penguin (EWP) or the color-suppressed tree amplitude can be embedded simultaneously into both the color-suppressed tree and the EWP contribution in B → Kπ decays. We present a systematic method to extract each standard model (SM)-like hadronic parameter as well as new physics parameters in analytic way, so that one can pinpoint them once experimental data are given. Using the currently available experimental data for B → Kπ modes, we find two possible analytic results: one showing the large SM-like color-suppressed tree contribution and the other showing the large SM-like EWP contribution. The magnitude of the NP amplitude and its weak phase are quite large. For instance, we find |PNP/P′| = 0.39 ± 0.13, φNP = 92° ± 15° and δNP = 7° ± 26°, which are the ratio of the NP-to-SM contribution, the weak and the strong phase of the NP amplitude, respectively. We also investigate the dependence of the NP contribution on the weak phase γ and the mixing induced CP asymmetry of B0 → KSπ0, respectively

Analytic resolution of puzzle in [formula omitted] decays

We present a systematic method to extract each Standard Model (SM)-like hadronic parameter as well as new physics parameters in analytic way for B→Kπ decays. Using the analytic method to the currently available experimental data, we find two possible solutions physically equivalent: one showing the large SM-like color-suppressed tree contribution and the other showing the large SM-like electroweak penguin contribution. The magnitude of new physics (NP) amplitude and its weak phase are quite large. For instance, we find |PNP/P|=0.39±0.13, ϕNP=91°±15° and δNP=8°±27°, which are the ratio of the NP to the SM penguin contribution, the weak and the relative strong phase of the NP amplitude, respectively.

D0-D̄0 mixing and CP violation at BES-III**Supported by Knowledge Innovation Project of CAS (U-612, U-530 (IHEP)) and 100 Talents Program of CAS

Recently, both BaBar and Belle experiments found evidences of neutral D mixing. In this paper, we discuss the sensitivities of the measurements of D mixing parameters at BES-III. With CP tag technique at ψ(3770) peak, the extraction of the strong phase difference in D0 → Kπ decay at BES-III are discussed. We also make an estimate on the measurements of the mixing rate RM by using the coherent data at ψ(3770) peak. The CP violation in D system is predicted with an unobserved level in the Standard Model. Any significant CP violation in the D system indicates the existence of new physics. The sensitivity of the measurements of CP violation in the D system is estimated in the coherent D decays. Finally, the search for the rare D decays are discussed, in which some of the forbidden decays are smoking gun of new physics.

Examination of flavor SU(3) in B, [formula omitted] decays

We study a relation between the weak phase γ and the rates and CP asymmetries of several Kπ decays of B+, B0, and Bs, emphasizing the impact of the latter measurements. Current data indicate large SU(3) breaking in the strong phases or failure of factorization (including its application to penguin amplitudes) in Kπ modes of B0 and Bs. SU(3) and factorization only remain approximately valid if the branching ratio for Bs→K−π+ exceeds its current value of (5.27±1.17)×10−6 by at least 42%, or if a parameter ξ describing ratios of form factors and decay constants is shifted from its nominal value by more than twice its estimated error.

D0-D̄0 mixing at BaBar

This article reviews the recent measurement of D0-D̄0 mixing with the D0 → Kπ decay channel from the BaBar experiment at the PEP-II B-Factory. Averages from the Heavy Flavor Averaging Group between this result and a previous result from BELLE are also presented.

Suppression of flavor symmetry breaking in B decay sum rules

While flavor symmetries are useful for studying hadronic B decays, symmetry relations for amplitudes and decay rates are usually violated by first order symmetry breaking corrections. We point out two cases in which first order symmetry breaking is suppressed by a small ratio of amplitudes: (1) An isospin sum rule for four B→Kπ decays, where isospin breaking is shown to be negligible. (2) An SU(3) sum rule for pairs of B→Kπ and B→Kη8, generalized to pairs of B→Kπ, B→Kη and B→Kη′.

The [formula omitted] puzzle and supersymmetric models

In the light of new experimental results on B→Kπ decays, we study the decay processes B→Kπ in the framework of both R-parity conserving (SUGRA) and R-parity violating supersymmetric models. We find that any possible deviations from the Standard Model indicated by the current data for the branching ratios and the direct CP asymmetries of B→Kπ can be explained in both R-parity conserving SUGRA and R-parity violating SUSY models. However, there is a difference between the predictions of both models to the time-dependent CP asymmetry observable SKSπ0 whose current experimental results include large uncertainties. We demonstrate that this difference can be useful for testing both models with more accurate data for SKSπ0 and ACP+− in the near future.

A precise sum rule among four [formula omitted] CP asymmetries

A sum rule relation is proposed for direct CP asymmetries in B→Kπ decays. Leading terms are identical in the isospin symmetry limit, while subleading terms are equal in the flavor SU(3) and heavy quark limits. The sum rule predicts ACP(B0→K0π0)=−0.17±0.06 using current asymmetry measurements for the other three B→Kπ decays. A violation of the sum rule would be evidence for new physics in b→sq¯q transitions.

Rates and asymmetries in B→Kπ decays

We discuss a potential discrepancy in an approximate relation among B→Kπ rates which, with increased statistical significance, would imply new physics in ΔI=1 transitions. An approximate relation between CP-violating rate differences in B0/B0→K±π∓ and B±→K±π0 is used to combine these rate differences to reduce upper limits on the two CP asymmetries. These rates and asymmetries are used to update bounds on the CKM phase γ.

B → Kπ decays and the weak phase angle γ

The large branching ratios for B → Kπ decays as observed by the CLEO Collaboration indicate that penguin interactions contribute a major part to the decay rates and provide an interference between the Cabibbo-suppressed tree and penguin contributions resulting in a CP-asymmetry between the B → Kπ and its charge conjugate mode. The CP-averaged decay rates depend also on the weak phase γ and give us a determination of this phase. In this talk, I would like to report on a recent analysis of B → Kπ decays using factorisation model with final state interaction phase shift included. We find that factorisation seems to describe qualitatively the latest CLEO data. We also obtain a relation for the branching ratios independent of the strength of the strong penguin interactions. This relation gives a central value of 0.60 × 10 −5 for B( B̄ 0 → K̄ 0π 0), somewhat smaller than the latest CLEO measurement. We also find that a ratio obtained from the CP-averaged B → Kπ decay rates could be used to test the factorisation model and to determine the weak angle γ with more precise data, though the latest CLEO data seem to favor γ in the range 90° – 120°.

Fat penguins and imaginary penguins in perturbative QCD

We evaluate B→ Kπ decay amplitudes in perturbative QCD picture. It is found that penguin contributions are dynamically enhanced by nearly 50% compared to those assumed in the factorization approximation. It is also shown that annihilation diagrams are not negligible, and give large strong phases. Our results for branching ratios of B→ Kπ decays for a representative parameter set are consistent with data.

Amplitude analysis for D to Kπ decays

An amplitude analysis for D to K pi decay is made. The ratio of the two isospin amplitudes I=1/2 and 3/2 is calculated. The relative phase of these two amplitudes is determined. A reanalysis of K to 2 pi decay amplitude is also presented.