Time-dependent Dalitz Plot Analysis Research Articles

Measurement of cos2β in B0→D(*)h0 with D→KS0π+π− decays by a combined time-dependent Dalitz plot analysis of BaBar and Belle data

We report measurements of $\sin{2\beta}$ and $\cos{2\beta}$ from a time-dependent Dalitz plot analysis of $B^{0} \to D^{(*)} h^{0}$ with $D \to K_{S}^{0} \pi^{+} \pi^{-}$ decays, where the light unflavored and neutral hadron $h^{0}$ is a $\pi^{0}$, $\eta$, or $\omega$ meson. The analysis is performed with a combination of the final data sets of the \babar\ and Belle experiments containing $471 \times 10^{6}$ and $772 \times 10^{6}$ $B\bar{B}$ pairs collected at the $\Upsilon\left(4S\right)$ resonance at the asymmetric-energy B factories PEP-II at SLAC and KEKB at KEK, respectively. We measure $\sin{2\beta} = 0.80 \pm 0.14 \,(\rm{stat.}) \pm 0.06 \,(\rm{syst.}) \pm 0.03 \,(\rm{model})$ and $\cos{2\beta} = 0.91 \pm 0.22 \,(\rm{stat.}) \pm 0.09 \,(\rm{syst.}) \pm 0.07 \,(\rm{model})$. The result for the direct measurement of the angle is $\beta = \left( 22.5 \pm 4.4 \,(\rm{stat.}) \pm 1.2 \,(\rm{syst.}) \pm 0.6 \,(\rm{model}) \right)^{\circ}$. The last quoted uncertainties are due to the composition of the $D^{0} \to K_{S}^{0} \pi^{+} \pi^{-}$ decay amplitude model, which is newly established by a Dalitz plot amplitude analysis of a high-statistics $e^{+}e^{-} \to c\bar{c}$ data sample as part of this analysis. We find the first evidence for $\cos2\beta>0$ at the level of $3.7$ standard deviations. The measurement excludes the trigonometric multifold solution $\pi/2 - \beta = (68.1 \pm 0.7)^{\circ}$ at the level of $7.3$ standard deviations and therefore resolves an ambiguity in the determination of the apex of the CKM Unitarity Triangle. The hypothesis of $\beta = 0^{\circ}$ is ruled out at the level of $5.1$ standard deviations, and thus CP violation is observed in $B^{0} \to D^{(*)} h^{0}$ decays.

First Evidence for cos2β>0 and Resolution of the Cabibbo-Kobayashi-Maskawa Quark-Mixing Unitarity Triangle Ambiguity.

We present first evidence that the cosine of the CP-violating weak phase 2β is positive, and hence exclude trigonometric multifold solutions of the Cabibbo-Kobayashi-Maskawa (CKM) Unitarity Triangle using a time-dependent Dalitz plot analysis of B^{0}→D^{(*)}h^{0} with D→K_{S}^{0}π^{+}π^{-} decays, where h^{0}∈{π^{0},η,ω} denotes a light unflavored and neutral hadron. The measurement is performed combining the final data sets of the BABAR and Belle experiments collected at the ϒ(4S) resonance at the asymmetric-energy B factories PEP-II at SLAC and KEKB at KEK, respectively. The data samples contain (471±3)×10^{6}BB[over ¯] pairs recorded by the BABAR detector and (772±11)×10^{6}BB[over ¯] pairs recorded by the Belle detector. The results of the measurement are sin2β=0.80±0.14(stat)±0.06(syst)±0.03(model) and cos2β=0.91±0.22(stat)±0.09(syst)±0.07(model). The result for the direct measurement of the angle β of the CKM Unitarity Triangle is β=[22.5±4.4(stat)±1.2(syst)±0.6(model)]°. The measurement assumes no direct CP violation in B^{0}→D^{(*)}h^{0} decays. The quoted model uncertainties are due to the composition of the D^{0}→K_{S}^{0}π^{+}π^{-} decay amplitude model, which is newly established by performing a Dalitz plot amplitude analysis using a high-statistics e^{+}e^{-}→cc[over ¯] data sample. CP violation is observed in B^{0}→D^{(*)}h^{0} decays at the level of 5.1 standard deviations. The significance for cos2β>0 is 3.7 standard deviations. The trigonometric multifold solution π/2-β=(68.1±0.7)° is excluded at the level of 7.3 standard deviations. The measurement resolves an ambiguity in the determination of the apex of the CKM Unitarity Triangle.

Recent results on CP violation at B factories

We review recent results of the Beauty Factories BaBar and Belle on CP violation in the quark sector and constraints on the CKM unitarity triangle. We first present the recent measurement, using BaBar and Belle data, of cos(2β) = cos(2ϕ1) in B0 → D(∗)h0 with $D \rightarrow {K^{0}_{S}} \pi ^{+} \pi ^{-}$ decays, using a combined time-dependent Dalitz plot analysis. The BaBar Dalitz plot analysis of the $B^{+} \rightarrow {K^{0}_{S}} \pi ^{+} \pi ^{0}$ decay is also presented, and shows an evidence for direct CP violation in B+ → K∗(892)π0. A recently published BaBar measurement of the |V ub| CKM matrix element allows to contrain one side of the unitarity triangle. These analyses use the data sets of the BaBar and Belle experiments containing 471 × 106 and 772 × 106 $B\overline {B}$ pairs collected at the Υ(4S) resonance at the asymmetric-energy B factories PEP-II at SLAC and KEKB at KEK, respectively.

Bs0(B¯s0)→DCP0KK¯: Detecting and discriminating new physics inBs0−B¯s0mixing

If the weak phase of B_s-anti B_s mixing (2 beta_s) is found to be significantly different from zero, this is a clear signal of new physics (NP). However, if such a signal is found, we would like an unambiguous determination of 2 beta_s in order to ascertain which NP models could be responsible. In addition, in the presence of NP, the width difference \Delta\Gamma_s between the two B_s mass eigenstates can be positive or negative, and ideally this sign ambiguity should be resolved experimentally. Finally, in order to see if the NP is contributing to \Gamma^s_{12} in addition to M^s_{12}, the precise measurement of |\Gamma^s_{12}| is crucial. In this paper, we consider several different methods of measuring B_s-anti B_s mixing using two- and three-body decays with ${\bar b} \to {\bar c} u {\bar s}$ and ${\bar b} \to {\bar u} c {\bar s}$ transitions. We find that the most promising of these is a time-dependent Dalitz-plot analysis of $B_s (\bar B_s) \to D^0_{CP} K {\bar K}$. With these decays, all of the above issues can be addressed, and the measurement of the weak phase gamma is also possible. We also note that, with all three-body decays it is possible to resolve the sign ambiguity of \Delta\Gamma_s even without determining the CP phase phi_s.

Charm and Charm spectroscopy

Recent developements in D mixing physics and charm spectroscopy will be discussed. Focus will be on the BaBar experimental results for the D mixing: first evidence of the D 0 -mixing (hadronic D 0 decays), lifetime difference and time-dependent Dalitz plot analysis of D 0 → K + π − π 0 . Then, recent results on charm spectroscopy will be presented with particular focus on the new D s states that have been discovered in the last few years. Some of these states were not expected theoretically: their masses, widths, quantum numbers, and decay modes do not fit the existing spectroscopic classication, which is based mostly on potential model calculations.

A method of measuring cos(2β) using a time-dependent dalitz plot analysis of B0 → DCPπ+π−

We present a feasibility study of a previously outlined method for measuring both the sine and the cosine of twice the Cabibbo–Kobayashi—Maskawa (CKM) Unitarity Triangle angle β using a time-dependent Dalitz plot analysis of B0 → Dπ+π− decays, where the neutral D meson is reconstructed in decays to CP eigenstates. We show that this method can be used at the B factories to make a measurement of cos(2β) that is competitive with, or more precise than, other techniques using different quark-level transitions, while sin(2β) can be measured to a better precision than any existing measurement using transitions. Furthermore, this technique has great potential to be employed at LHCb.

Charm mixing from BABAR**Supported by Università di Pisa and INFN. Also Supported by U.S. Department of Energy and SLAC, Stanford University

We present recent results from BABAR experiment for D0-D̄0 mixing measurements. Mixing parameters can be measured in different ways using different D0 decay modes, here we discuss the most sensitive analyses such as D0 → K+π− where we had the first evidence of charm mixing, the measurement of the ratio of lifetimes of the decays D0 → K+K− and D0 → π+π− relative to D0 → K−π+, the time dependent Dalitz plot analysis of D0 → K+π−π0. New limits on CP-violating time-integrated asymmetries in D0 → K+K− and D0 → π+π− are also discussed. The analyses presented are based on 384 fb−1 data collected with the BABAR detector at the PEP-II asymmetric B Factory.

Time-dependent Dalitz plot analysis ofB0→D∓K0π±decays

We present for the first time a measurement of the weak phase 2b+g obtained from a time-dependent Dalitz plot analysis of B^0 -> D-(+) K0 Pi+(-) decays. Using a sample of approximately 347*10^{6} BBbar pairs collected by the BABAR detector at the PEP-II asymmetric-energy storage rings, we obtain 2b+g = (83 +/- 53 +/- 20) degrees and (263 +/- 53 +/- 20) degrees assuming the ratio r of the b -> u and b -> c decay amplitudes to be 0.3. The magnitudes and phases for the resonances associated with the b -> c transitions are also extracted from the fit.

Measurement ofD0−D¯0Mixing Parameters inD0→Ksπ+π−Decays

We report a measurement of D0−D¯0 mixing parameters in D0→KS0π+π− decays using a time-dependent Dalitz-plot analysis. We first assume CP conservation and subsequently allow for CP violation. The results are based on 540 fb−1 of data accumulated with the Belle detector at the KEKB e+e− collider. Assuming negligible CP violation, we measure the mixing parameters x=(0.80±0.29−0.07−0.14+0.09+0.10)% and y=(0.33±0.24−0.12−0.08+0.08+0.06)%, where the errors are statistical, experimental systematic, and systematic due to the Dalitz decay model, respectively. Allowing for CP violation, we obtain the CP-violating parameters |q/p|=0.86−0.29−0.03+0.30+0.06±0.08 and arg(q/p)=(−14−18−3−4+16+5+2)°.Received 21 June 2007DOI:https://doi.org/10.1103/PhysRevLett.99.131803©2007 American Physical Society

Measurement ofCP-violating asymmetries inB0→(ρπ)0using a time-dependent Dalitz plot analysis

We report a measurement of CP-violating asymmetries in B0-->(rhopi)0-->pi+pi-pi0 decays using a time-dependent Dalitz plot analysis. The results are obtained from a data sample of 375 million Y(4S) --> BBbar decays, collected by the BaBar detector at the PEP-II asymmetric-energy B Factory at SLAC. We measure 26 coefficients of the bilinear form-factor terms occurring in the time-dependent decay rate of the B0 meson. We derive the physically relevant quantities from these coefficients. In particular, we measure a constraint on the angle alpha of the Unitarity Triangle.

Expected accuracy in a measurement of the CKM angle α using a Dalitz plot analysis of B 0 → ρπ decays in the BTeV project

A precise measurement of the angle {alpha} in the CKM triangle is very important for a complete test of Standard Model. A theoretically clean method to extract {alpha} is provided by B{sup 0} {yields} {rho}{pi} decays. Monte Carlo simulations to obtain the BTeV reconstruction efficiency and to estimate the signal to background ratio for these decays were performed. Finally the time-dependent Dalitz plot analysis, using the isospin amplitude formalism for tre and penguin contributions, was carried out. It was shown that in one year of data taking BTeV could achieve an accuracy on {alpha} better than 5{sup o}.

Measurement ofCPAsymmetry in a Time-Dependent Dalitz Analysis ofB0→(ρπ)0and a Constraint on the Quark Mixing Matrix Angleϕ2

We present a measurement of CP asymmetry using a time-dependent Dalitz plot analysis of B0-->pi+pi-pi0 decays based on a 414 fb(-1) data sample containing 449 x 10(6) BB pairs. The data was collected on the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric energy e+ e- collider. Combining our analysis with information on charged B decay modes, we perform a full Dalitz and isospin analysis and obtain a constraint on the CKM angle phi2, 68 degrees < phi2 < 95 degrees as the 68.3% confidence interval for the phi2 solution consistent with the standard model (SM). A large SM-disfavored region also remains.

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.

CKM phaseαthroughB→a0π

We propose the decay modes $B \to a_0 (\to \eta \pi) \pi$ to determine the CKM phase $\alpha$. One can analyze these modes through (i) the $B \to a_0 \pi$ isospin pentagon, (ii) the time dependent Dalitz plot of $B^0(t) \to a_0^{\pm} \pi^{\mp} \to \eta \pi^+ \pi^-$, and (iii) the time dependence of $B^0(t) \to a_0^0 (\to \eta \pi^0) \pi^0$. We show that the $a_0 \pi$ modes have certain advantages as compared to the $\rho \pi$ modes, and strongly recommend the time dependent Dalitz plot analysis in the $a_0 \pi$ channel.