CP-violating Asymmetries Research Articles

CP violation in the b → sℓ+ℓ− transition beyond the standard model

In this study the CP asymmetry in the b → sℓ+ℓ− transition was investigated in minimal extension of the standard model where Ceff9 receives an extra weak phase due to the new physics effects. We observed that CP-violation asymmetry can be measurable in the framework of this scenario.

Measurement of branching fractions andCP-violating charge asymmetries forB-meson decays toD(*)D¯(*), and implications for the Cabibbo-Kobayashi-Maskawa angleγ

We present measurements of the branching fractions and charge asymmetries of B decays to all D(*)D(*) modes. Using 232 million BBbar pairs recorded on the Upsilon(4S) resonance by the BaBar detector at the e+e- asymmetric B factory PEP-II at the Stanford Linear Accelerator Center, we measure the branching fractions BF(B0 -> D*+D*-) = (8.1 +- 0.6 +- 1.0) x 10^-4, BF(B0 -> D*+-D-+) = (5.7 +- 0.7 +- 0.7) x 10^-4, BF(B0 -> D+D-) = (2.8 +- 0.4 +- 0.5) x 10^-4, BF(B+ -> D*+D*0) = (8.1 +- 1.2 +- 1.2) x 10^-4, BF(B+ -> D*+D0) = (3.6 +- 0.5 +- 0.4) x 10^-4, BF(B+ -> D+D*0) = (6.3 +- 1.4 +- 1.0) x 10^-4, and BF(B+ -> D+D0) = (3.8 +- 0.6 +- 0.5) x 10^-4, where in each case the first uncertainty is statistical and the second systematic. We also determine the limits BF(B0 -> D*0D*0) < 0.9 x 10^-4, BF(B0 -> D*0D0) < 2.9 x 10^-4, and BF(B0 -> D0D0) < 0.6 x 10^-4, each at 90% confidence level. All decays above denote either member of a charge conjugate pair. We also determine the CP-violating charge asymmetries A(B0 -> D*+-D-+) = 0.03 +- 0.10 +- 0.02, A(B+ -> D*+D*0) = -0.15 +- 0.11 +- 0.02, A(B+ -> D*+D0) = -0.06 +- 0.13 +- 0.02, A(B+ -> D*+D*0) = 0.13 +- 0.18 +- 0.04, and A(B+ -> D+D0) = -0.13 +- 0.14 +- 0.02. Additionally, when we combine these results with information from time-dependent CP asymmetries in B0 -> D*+D*- decays and world-averaged branching fractions of B decays to Ds(*)D(*) modes, we find the CKM phase gamma is favored to lie in the range [0.07-2.77] radians (with a +0 or +pi radians ambiguity) at 68% confidence level.

DARK-MATTER PARTICLES AND BARYONS FROM INFLATION AND SPONTANEOUS CP VIOLATION IN THE EARLY UNIVERSE

We present aspects of a model which attempts to unify the creation of cold dark matter, a CP-violating baryon asymmetry, and also a small, residual vacuum energy density, in the early universe. The model contains a primary scalar (inflaton) field and a primary pseudoscalar field, which are initially related by a cosmological, chiral symmetry. The nonzero vacuum expectation value of the pseudoscalar field spontaneously breaks CP invariance.

THE NORMALIZATION EFFECT OF NEUTRAL B0MESON ASYMMETRY

In the study of CP violation asymmetry in CPLEAR, the decay rate of neutral meson is normalized and its experimental analysis has been well established, while normalization effect has been considered in B physics. After investigation on the normalization effect in BABAR, we conclude that it can be justified to neglect this effect due to the suppressed decays that are contributed from both B0and [Formula: see text].

Branching ratio andCPAsymmetry ofB→ρη(′)decays in the perturbative QCD approach

In this paper,we calculate the branching ratios and CP-violating asymmetries for $B^0 \to \rho^0 \eta^{(\prime)}$ and $B^+\to \rho^+ \etap$ decays in the perturbative QCD factorization approach. In this approach, we not only calculate the usual factorizable contributions, but also evaluate the non-factorizable and annihilation type contributions. Besides the current-current operators, the contributions from the QCD and electroweak penguin operators are also taken into account. The theoretical predictions for the branching ratios are $Br(B^+ \to \rho^+ \eta^{(\prime)}) \approx 9 \times 10^{-6}$ and $Br(B^0 \to \rho^0 \eta^{(\prime)}) \approx 5 \times 10^{-8}$, which agree well with the measured values and currently available experimental upper limits. We also predict large CP-violating asymmetries in these decays: $A_{CP}^{dir}(\rho^\pm \eta)\approx -13 %$, $A_{CP}^{dir}(\rho^\pm \eta^\prime)\approx -18 %$, $A_{CP}^{dir}(\rho^0 \eta)\approx -41%$, $A_{CP}^{dir}(\rho^0 \eta^\prime)\approx -27%$, $A_{CP}^{mix}(\rho^0 \eta)\approx +25%$, and $A_{CP}^{mix}(\rho^0 \eta^\prime) \approx +11%$, which can be tested by the current or future B factory experiments.

Measurements of neutralBdecay branching fractions toKS0π+π−final states and the charge asymmetry ofB0→K*+π−

We analyze the decay B0→KS0π+π− using a sample of 232×106 Υ(4S)→BB¯ decays collected with the BABAR detector at the SLAC PEP-II asymmetric-energy B factory. A maximum likelihood fit finds the following branching fractions: B(B0→K0π+π−)=(43.0±2.3±2.3)×10−6, B(B0→f0(→π+π−)K0)=(5.5±0.7±0.5±0.3)×10−6 and B(B0→K*+π−)=(11.0±1.5±0.5±0.5)×10−6. For these results, the first uncertainty is statistical, the second is systematic, and the third (if present) is due to the effect of interference from other resonances. We also measure the CP-violating charge asymmetry in the decay B0→K*+π−, AK*π=−0.11±0.14±0.05.Received 4 August 2005DOI:https://doi.org/10.1103/PhysRevD.73.031101©2006 American Physical Society

Search for direct CP violation in the decays [formula omitted

We report a measurement of the direct CP violation asymmetry parameter Ag in charged kaon decays K±→π±π+π− by the NA48/2 experiment at the CERN SPS. The experiment has been designed not to be limited by systematics in the asymmetry measurement. Using 1.67×109 such decays collected during the 2003 run, the charge asymmetry in the Dalitz plot linear slope parameter g has been measured to be Ag=(1.7±2.9)×10−4. The precision of the result is limited by the statistics used.

Supersymmetric contributions toB0s→K+K-

Inspired by the existing calculation of B->piK decays in supersymmetry (SUSY), we evaluate the dominant SUSY contributions to Bs->K+K-. We show that the observables of this process can be significantly modified in the presence of SUSY. In particular, the branching ratio can be increased considerably compared to the prediction of the standard model (SM). The effect is even more dramatic for the CP-violating asymmetries A_dir and A_mix. These asymmetries, expected to be small in the SM (A_dir is predicted to take only positive values), change drastically with SUSY contributions. The measurement of these observables can therefore be used to detect the presence of physics beyond the SM, and put constraints on its parameters.

Branching ratio and CP asymmetry of [formula omitted] decays in the perturbative QCD approach

We calculate the branching ratios and CP-violating asymmetries for B 0 → π 0 η ( ′ ) and B + → π + η ( ′ ) decays in the perturbative QCD (pQCD) factorization approach here. We not only calculate the usual factorizable contributions, but also evaluate the non-factorizable and annihilation type contributions. Besides the current–current operators, the contributions from the QCD and electroweak penguin operators are also taken into account. The pQCD results for the CP-averaged branching ratios are Br ( B + → π + η ) ≈ 4.1 × 10 −6 , Br ( B + → π + η ′ ) ≈ 2.4 × 10 −6 , and Br ( B 0 → π 0 η ( ′ ) ) ≈ 0.2 × 10 −6 , which agree very well with the measured values or currently available experimental upper limits. We also predict large CP-violating asymmetries in these decays: A CP dir ( π ± η ( ′ ) ) ∼ A CP dir ( π 0 η ( ′ ) ) ∼ − 0.35 , and A CP mix ( π 0 η ( ′ ) ) ∼ 0.67 , but with large errors. The pQCD prediction for A CP dir ( π ± η ) ( A CP dir ( π ± η ′ ) ) has the same (opposite) sign with the primary measured values. Further improvements in both theory and experiments are needed to clarify this discrepancy.

Measurement of the time-dependentCP-violating asymmetry inB0→KS0π0γdecays

We present a measurement of the time-dependent CP-violating asymmetry in $B^0 \to K^{*}_0\gamma$ decays with $K^{*}_0\to K^{0}_s\pi^0$ based on 232 million $\Upsilon(4\mathrm{S})\to B\bar{B}$ decays collected with the BaBar detector at the PEP-II asymmetric-energy $e^{+}e^{-}$ collider at SLAC. In a sample containing $157\pm 16$ signal decays, we measure $S_{K^{*}_0\gamma} = -0.21 \pm 0.40 \pm 0.05$ and $C_{K^{*}_0\gamma}= -0.40 \pm 0.23 \pm 0.03$, where the first error is statistical and the second systematic. We also explore $B^0 \to K^{0}_s\pi^0\gamma$ decays with $1.1<m_{K^{0}_s\pi^0}<1.8$ GeV$/c^2$ and find $59\pm13$ signal events with $S_{K^{0}_s\pi^0} = 0.9 \pm 1.0 \pm 0.2$ and $C_{K^{0}_s\pi^0} = -1.0 \pm 0.5 \pm 0.2$.

Branching Fraction and CP Asymmetries of B0→KS0KS0KS0

We present measurements of the branching fraction and time-dependent CP-violating asymmetries in B0-->K0(S)K0(S)K0(S) decays based on 227 x 10(6) Upsilon4S-->BB decays collected with the BABAR detector at the PEP-II asymmetric-energy B factory at SLAC. We obtain a branching fraction of (6.9(+0.9)(-0.8)+/-0.6) x 10(-6), and CP asymmetries C=-0.34(+0.28)(-0.25)+/-0.05 and S=-0.71(+0.38)(-0.32)+/-0.04, where the first uncertainties are statistical and the second systematic.

Measurement of time-dependentCP-violating asymmetries and constraints onsin(2β+γ)with partial reconstruction ofB→D*∓π±decays

We present a measurement of the time-dependent CP-violating asymmetries in decays of neutral B mesons to the final states D*-+ pi+-, using approximately 232 million BBbar events recorded by the BABAR experiment at the PEP2 e+e- storage ring. Events containing these decays are selected with a partial reconstruction technique, in which only the high-momentum pi+- from the B decay and the low-momentum pi-+ from the D*-+ decay are used. % We measure the parameters related to 2beta+gamma to be a_D*pi=-0.034 +- 0.014 +- 0.009 and c_l_D*pi = -0.019 +- 0.022 +- 0.013. With some theoretical assumptions, we interpret our results in term of the lower limits |\sin(2beta+gamma)|> 0.62 (0.35) at 68% (90%) confidence level.

DALITZ PLOT ANALYSES OF CHARMLESS B DECAYS

We present preliminary results of maximum-likelihood Dalitz plot analyses performed by the BABAR Collaboration of the charmless hadronic decays B0 → K+π-π0, B+ → K+π-π+, and B+ → π+π-π+. We report inclusive decay rates, as well as fractions and phases for intermediate resonant decays. We also report CP-violating charge asymmetries for intermediate resonant decays of neutral B mesons.

Measurement of CP-Violating Asymmetries in B0 → (ρπ)0 Using a Time-Dependent Dalitz Plot Analysis

We present the preliminary measurement of CP-violating asymmetries in B0 → (ρπ)0 → π+π-π0 decays using a time-dependent Dalitz plot analysis. The results are obtained from a data sample of 213 million [Formula: see text] decays, collected by the BaBar detector at the PEPII asymmetric-energy B -Factory at SLAC. We measure 16 coefficients of the bilinear form factor terms occurring in the time-dependent decay rate of the B0 meson with the use of a maximum-likelihood fit. The physically relevant CP parameters are derived from these coefficients.

Measurement of the branching fraction and theCP-violating asymmetry for the decayB0→KS0π0

We measure the branching fraction and the CP-violating asymmetry of B0→KS0π0 decays with 227 million Υ(4S)→BB¯ events collected with the BABAR detector at the PEP-II asymmetric-energy e+e− collider at SLAC. We obtain a branching fraction B(B0→K0π0)=(11.4±0.9±0.6)×10−6 and CP-violating asymmetry parameters CKS0π0=0.06±0.18±0.03 and SKS0π0=0.35−0.33+0.30±0.04, where the first error is statistical and the second systematic.Received 4 March 2005DOI:https://doi.org/10.1103/PhysRevD.71.111102©2005 American Physical Society

Measurement of Polarization and Triple-Product Correlations inB→ϕK*Decays

We present measurements of decay amplitudes and triple-product correlations in B-->phiK* decays based on 253 fb(-1) of data recorded at the Upsilon(4S) resonance with the Belle detector at the KEKB e(+)e(-) storage ring. The decay amplitudes for the three different helicity states are determined from the angular distributions of final-state particles. The longitudinal polarization amplitudes are found to be 0.45 +/- 0.05 +/- 0.02 for B0-->phiK(*0) and 0.52 +/- 0.08 +/- 0.03 for B+ -->phiK(*+) decays. CP- and T-odd CP-violating triple-product asymmetries are measured to be consistent with zero.

Branching fraction, polarization and CP-violating asymmetries in [formula omitted] decays

We present measurements of the branching fraction, the polarization parameters and CP-violating asymmetries in B0→D∗+D∗− decays using a 140 fb−1 data sample collected at the ϒ(4S) resonance with the Belle detector at the KEKB energy-asymmetric e+e− collider. We obtain B(B0→D∗+D∗−)=[0.81±0.08(stat)±0.11(syst)]×10−3, R⊥=0.19±0.08(stat)±0.01(syst), R0=0.57±0.08(stat)±0.02(syst), S=−0.75±0.56(stat)±0.12(syst) and A=−0.26±0.26(stat)±0.06(syst). Consistency with Standard Model expectations is also discussed.

CP-violating asymmetry in chargino decay into neutralino and W boson

In the MSSM with complex parameters, loop corrections to χ˜i±→χ˜j0W± lead to a CP violating asymmetry ACP=(Γ(χ˜i+→χ˜j0W+)−Γ(χ˜i−→χ˜j0W−))/(Γ(χ˜i+→χ˜j0W+)+Γ(χ˜i−→χ˜j0W−)). We calculate this asymmetry at full one-loop level. We perform a detailed numerical analysis for χ˜1±→χ˜10W± and χ˜2±→χ˜10W± analyzing the dependence on the parameters and phases involved. Asymmetries of several percent are obtained. We also discuss the feasibility of measuring these asymmetries at LHC.

Factorization fits to charmless strangelessBdecays

We present fits to charmless strangeless hadronic B decay data for mean branching ratios and CP-violating asymmetries using the QCD factorization model of Beneke et al. Apart from one CP-violating parameter, the model gives a very good representation of 26 measured data. We find the CKM angle alpha = (93.5 +/- 8.4 -1.3) degrees and to be quite stable to plausible "charming penguin" corrections.

Measurements of the Branching Fraction andCP-Violation Asymmetries inB0→f0(980)KS0

We present measurements of the branching fraction and CP-violating asymmetries in the decay B0-->f0(980)K0S. The results are obtained from a data sample of 123 x 10(6) Upsilon(4S)-->BB decays. From a time-dependent maximum likelihood fit, we measure the branching fraction B(B0-->f0(980)(-->pi+pi-)K0)=(6.0+/-0.9+/-0.6+/-1.2)x10(-6), the mixing-induced CP violation parameter S=-1.62(+0.56)(-0.51)+/-0.09+/-0.04, and the direct CP violation parameter C=0.27+/-0.36+/-0.10+/-0.07, where the first errors are statistical, the second systematic, and the third due to model uncertainties. We measure the f0(980) mass and width to be mf0(980)=(980.6+/-4.1+/-0.5+/-4.0) MeV/c2 and Gammaf0(980)=(43(+12)(-9)+/-3+/-9) MeV/c2, respectively.