arXiv subjects
Publications and source records attributed to B. Aubert.
We present updated measurements of the CP-violating parameters S_pipi and C_pipi in B0 -> pi+pi- decays. Using a sample of 227 million Y(4S) -> BBbar decays collected with the BaBar detector at the PEP-II asymmetric-energy e+e- collider at SLAC, we observe 467 +- 33 signal decays and measure S_pipi = -0.30 +- 0.17 (stat) +- 0.03 (syst), and C_pipi = -0.09 +- 0.15 (stat) +- 0.04 (syst).
We present a measurement of the direct CP violating asymmetry in the decay B0 -> K+pi- using 227 x 10^6 Y(4S) -> BBbar decays collected with the BaBar detector at the PEP-II asymmetric-energy e+e- collider at SLAC, we observe a total signal yield of n(K-pi+) + n(K+pi-) = 1606 +- 51 decays and measure the asymmetry [n(K-pi+)-n(K+pi-)]/[n(K-p+-)+n(K+pi-)] = -0.133+-0.030 (stat) +- 0.009 (syst). The probability of observing such an asymmetry in the absence of direct CP violation is 1.3 x 10^-5, corresponding to 4.2 standard deviations.
We search for the factorization-suppressed decays B -> chi_c0 K(*) and B -> chi_c2 K(*), with chi_c0 and chi_c2 decaying into J/psi gamma using a sample of 124 10^6 BBbar events collected with the BABAR detector at the PEP-II storage ring of the Stanford Linear Accelerator Center.
Based on 88 million Y(4S)->BB decays collected by the BaBar experiment at the PEP-II asymmetric-energy B factory at SLAC, we report preliminary results of four analyses which study in semileptonic charmless B decays, B->Xulnu and measure Vub. In events in which one B meson decay to a hadronic final state is fully reconstructed, the semileptonic decay of the second B meson is identified by the detection of a charged lepton. From both the spectrum of the mass of the hadronic system (mX) and the two-dimensional distribution of mX and q^2 we derive the charmless semileptonic branching fraction and we extract Vub=(4.77\pm 0.28(stat.)\pm 0.25 (sys.)^{+0.65}_{-0.39}(theo.)) 10^-3 and Vub=(4.92\pm 0.39(stat.)\pm 0.36 (sys.)\pm 0.46(theo.)) 10^-3, respectively. We use the same sample to extract the true mX distribution for B->Xulnu events. Finally, we identify several exclusive charmless semileptonic B decays, and measure the branching fractions BR(B->pilnu) = (1.08 \pm 0.28(stat.) \pm 0.16(sys.))10^-4 and BR(B-> rho lnu) = (2.57 \pm 0.52(stat.) \pm 0.59(sys.)) 10^-4 using isospin and quark model constraints. We also set limits on BR(B^- -> eta l nu), BR(B^- -> eta' l nu), $BR(B^- -> a^0_0 l nu), and $BR(B^0 -> a^+_0lnu).
A search for the decays B --> rho(770) gamma and B0 --> omega(782)gamma is performed on a sample of 211x10^6 Y(4S)->BBbar events collected by the BABAR detector at the PEP-II asymmetric-energy e+e- storage ring. No evidence for the decays is seen. We set the following limits on the individual branching fractions: BF(B --> rho+ gamma)<1.8 x 10^-6, BF(B --> rho0 gamma)<0.4 x 10^-6, and BF(B --> omega gamma)<1.0 x 10^-6 at the 90% confidence level (C.L.). We use the quark model to limit the combined branching fraction BFbar[B --> (rho/omega) gamma]<1.2 x 10^-6, from which we determine a constraint on the ratio of Cabibbo-Kobayashi-Maskawa matrix elements |V_td|/|V_ts|.
We report measurements of branching fractions and charge asymmetries of exclusive decays of neutral and charged B mesons into two-body final states containing a charmonium state and a light strange meson. The charmonium mesons considered are J/Psi, Psi(2S) and Chi_c1, and the light meson is either K or K*. We use a sample of about 124 million BBbar events collected with the BABAR detector at the PEP-II storage ring at the Stanford Linear Accelerator Center.
We search for a charged partner of the X(3872) in the decay B --> X- K, X- --> J/psi pi- pi0, using 234 million BBbar events collected at the Y(4S) resonance with the BaBar detector at the PEP-II e+e- asymmetric-energy storage ring. The resulting product branching fraction upper limits are BR(B0 --> X- K+, X- --> J/psi pi- pi0) < 5.4 x 10(-6) and BR(B- --> X- K0bar,X- --> J/psi pi- pi0) < 22 x 10(-6) at the 90% confidence level.
We report on a study of direct CP violation in the decay B- -> D(*)0 K- with a Dalitz analysis of the D0 -> Ks pi- pi+ decay using a sample of 227 million BBbar pairs collected by the BaBar detector. Reference to the charge-conjugate state is implied here. We constrain the amplitude ratio rB=|A(B- -> D0bar K-)|/|A(B- -> D0 K-)| to be <0.19 at the 90% confidence level and rB*=|A(B- -> D*0bar K-)|/|A(B- -> D*0 K-)| = 0.155 +0.070-0.077 +/- 0.040 +/- 0.020 and we measure the relative strong phase deltaB=(114 +/- 41 +/- 8 +/- 10) deg and deltaB*=(303 +/- 34 +/- 14 +/- 10) deg between the amplitudes A(B- -> D(*)0bar K-) and A(B- -> D(*)0 K-). From these samples we measure gamma =(70 +/- 26 +/- 10 +/- 10) deg. The first error is statistical, the second error accounts for experimental uncertainties and the third error reflects the Dalitz model uncertainty. For this preliminary result we have quoted confidence intervals obtained with a Bayesian technique assuming a uniform prior in rB, gamma and deltaB.
Based on a sample of 227 million BBbar pairs collected by the BaBar detector at the PEP-II asymmetric-energy B Factory at SLAC, we measure the branching fraction B(B0 -> pi0pi0) = (1.17 +- 0.32 +- 0.10) x 1e-6, and the asymmetry C(pi0pi0) = -0.12 +- 0.56 +- 0.06. The B0 -> pi0pi0 signal has a significance of 5.0 sigma. We also measure B(B+ -> pi+pi0) = (5.8 +- 0.6 +- 0.4) x 1e-6, B(B+ -> K+pi0) = (12.0 +- 0.7 +- 0.6) x 1e-6, and the charge asymmetries A(pi+pi0) = -0.01 +- 0.10 +- 0.02 and A(K+pi0) = 0.06 +- 0.06 +- 0.01. Using isospin relations we find an upper bound on the angle difference |alpha - alpha(eff)| of 35 degrees at the 90% C.L.
We report on searches for B- to D0(bar) K- and B- to D*0(bar) K-, with D*0(bar) to D0(bar) pi0 or D*0(bar) to D0(bar) gamma, and D0(bar) to K+ pi- (and charge conjugates). These final states, which we denote as [K+pi-]_D K- and [K+pi-]_D* K-, can be reached through the b --> c transition B- to D(*)0 K- followed by the doubly Cabibbo-suppressed D0 to K+ pi-, or through the b --> u transition B- to D0bar K- followed by the Cabibbo-favored D0bar to K+ pi-, or through interference of the two. Our results are based on 227 million Upsilon(4s) to BBbar decays collected with the BaBar detector at SLAC. We measure the ratio R_Kpi == (Gamma(B+ to [K-pi+]_D K+) + Gamma(B- to [K+pi-]_D K-))/ (Gamma(B+ to [K+pi-]_D K+) + Gamma(B- to [K-pi+]_D K-)) = 0.013 + 0.011 - 0.009, R*_Kpi,D0pi0 == (Gamma(B+ to [K-pi+]_D*(pi0) K+) + Gamma(B- to [K+pi-]_D*(pi0) K-)) (Gamma(B+ to [K+pi-]_D*(pi0) K+) + Gamma(B- to [K-pi+]_D*(pi0) K-)) = -0.001 + 0.010 - 0.006 and R*_Kpi,D0gam == (Gamma(B+ to [K-pi+]_D*(gam) K+) + Gamma(B- to [K+pi-]_D*(gam) K-)) (Gamma(B+ to [K+pi-]_D*(gam) K+) + Gamma(B- to [K-pi+]_D*(gam) K-)) = 0.011 + 0.019 - 0.013. We set R_Kpi < 0.030 (90% C.L.) and from this limit we extract the amplitude ratio rB == |A(B- to D0bar K-)/A(B- to D0 K-)| < 0.23 at the 90% confidence level. This limit is obtained with the most conservative assumptions on the values of the CKM angle gamma and the strong phases in the B and D decay amplitudes. From the measurements of R*_Kpi,D0pi0 and R*_Kpi,D0gam we extract rB*^2 == |A(B- to D*0bar K-)/A(B- to D*0 K-)|^2 = 4.6 + 15.2 - 7.3 x 10-3 and rB*^2<(0.16)^2 at the 90% confidence level.
We search for the rare flavor-changing neutral-current decay $B^+ \to K^+ ν\barν$ in a data sample of 82 fb$^{-1}$ collected with the {\sl BABAR} detector at the PEP-II B-factory. Signal events are selected by examining the properties of the system recoiling against either a reconstructed hadronic or semileptonic charged-B decay. Using these two independent samples we obtain a combined limit of ${\mathcal B}(B^+ \to K^+ ν\barν)<5.2 \times 10^{-5}$ at the 90% confidence level. In addition, by selecting for pions rather than kaons, we obtain a limit of ${\mathcal B}(B^+ \to π^+ ν\barν)<1.0 \times 10^{-4}$ using only the hadronic B reconstruction method.
We describe searches for B meson decays to the charmless vector-vector final states omega K* and omega rho in 89 million B-Bbar pairs produced in e+e- annihilation at sqrt(s)=10.58 GeV. We measure the following branching fractions in units of 10^{-6}: BF(B0 -> omega K*0) = 3.4 +1.8 -1.6 +/- 0.4 (<6.0), BF(B+ -> omega K*+) = 3.5 +2.5 -2.0 +/- 0.7 (<7.4), BF(B0 -> omega rho0) = 0.6 +1.3 -1.1 +/- 0.4 (<3.3), and BF(B+ -> omega rho+) = 12.6 +3.7 -3.3 +/- 1.6. The first error quoted is statistical, the second systematic, and the upper limits are defined at 90% confidence level. For B+ -> omega rho+ we also measure the longitudinal spin alignment fraction f_L = 0.88 +0.12 -0.15 +/- 0.03 and charge asymmetry Ach = (5 +/- 26 +/- 2)%.
We report on a search for the flavor-changing neutral current decays $\Dz\to e^+e^-$ and $\Dz\toμ^+μ^-$, and the lepton-flavor violating decay $\Dz\to e^\pmμ^\mp$. The measurement is based on $122 {fb}^{-1}$ of data collected by the \babar detector at the PEP-II asymmetric $e^+e^-$ collider. No evidence is found for any of the decays. The upper limits on the branching fractions, at the 90 % confidence level, are $1.2\times 10^{-6}$ for $\Dz\to e^+e^-$, $1.3\times 10^{-6}$ for $\Dz\toμ^+μ^-$, and $8.1\times 10^{-7}$ for $\Dz\to e^\pmμ^\mp$.
We present results on $B\to J/ψ\xspace Kπ$ decays using $e^+e^-$ annihilation data collected with the BABAR detector at the $Υ(4S)$ resonance. The detector is located at the PEP-II asymmetric-energy storage ring facility at the Stanford Linear Accelerator Center. Using approximately 88 million $B\bar{B}$ pairs, we measure the decay amplitudes for the flavor eigenmodes and observe strong-phase differences indicative of final-state interactions with a significance of 7.6 standard deviations. We use the interference between the $Kπ$ $S$-wave and $P$-wave amplitudes in the region of the $K^*(892)$ to resolve the ambiguity in the determination of these strong phases. We then perform an ambiguity-free measurement of $\cos2β$ using the angular and time-dependent asymmetry in $B\to J/ψ\xspace K^{*0}(K_S^0π^0$) dec With $\sin 2 β$ fixed at its measured value and $\cos 2 β$ treated as an in we find $\cos 2β=2.72_{-0.79}^{+0.50}\mathrm{(stat)} \pm 0.27\mathrm{(syst)}$, de sign of $\cos 2β$ to be positive at 86% CL.
We present an inclusive search for strange pentaquark production in e+e- interactions at a center-of-mass energy of 10.58 GeV using 123 fb-1 of data collected with the BaBar detector. We look for the states that have been reported previously: the Theta+(1540), interpreted as a ududsbar state; and the Xi--(1860) and Xi0(1860), candidate dsdsubar and uss(uubar+ddbar) states, respectively. In addition we search for other members of the antidecuplet and corresponding octet to which these states are thought to belong. We find no evidence for the production of such states and set preliminary limits on their production cross sections as functions of c.m. momentum. The corresponding limits on the Theta+(1540) and Xi--(1860) rates per e+e- to qqbar event are well below the rates measured for ordinary baryons of similar mass.
We present a search for B decays to charmless final states involving charged or neutral a0 mesons. The data sample corresponds to 89 million BBbar pairs collected with the BABAR detector operating at the PEP-II asymmetric-energy B Factory at SLAC. We find no significant signals and determine the following 90% C.L. upper limits: BR(B0 -> a0-pi+) < 5.1x10{-6}, BR(B0 -> a0-K+) < 2.1x10{-6}, BR(B- -> a0-K0bar) < 3.9x10{-6}, BR(B+ -> a00pi+) < 5.8x10{-6}, BR(B+ -> a00K+) < 2.5x10{-6}, and BR(B0 -> a00K0) < 7.8x10{-6}, where in all cases BR indicates the product of branching fractions for B -> a0X and a0 -> etapi, where X indicates K or pi.
We present a preliminary measurement of \rone, \rtwo and \rhosq which are the three parameters used to characterize the $B\rar D^*\ell\barν_e$ form factors ($A_1$, $V$, and $A_2$). We use $85 \times 10^6$ $B\bar B$-pairs accumulated on the \upsfs resonance at PEP-II. In this analysis we use the decay mode $\bar B^0\rar D^{+*}e^-\barν$ and its charge conjugate. The $D^{*+}$ is reconstructed in the channel $D^{*+}\to D^0π^+$ and the $D^0$ in the channel $\dtokpi$. We parameterize the \ff s in terms of their ratios (determined by the parameters $R_1$ and $R_2$) and the common slope $\rhosq$ in the variable $w$ (a quantity related to the momentum transfer in the decay process). These parameters are determined via an unbinned maximum likelihood fit to the distributions in four kinematic variables (three decay angles and $w$). The results are $R_1= 1.328 \pm 0.055\pm 0.025\pm 0.025$ and $R_2=0.920 \pm 0.044\pm 0.020\pm 0.013 $ for the ratios and $\rhosq= 0.769\pm 0.039 \pm 0.019\pm 0.032 $ for the slope. The stated errors are the statistical uncertainty from the data, statistical uncertainty from the size of the Monte Carlo sample and the systematic uncertainty, respectively.
We search for B+/- --> [K^-/+ pi+/-]_D K+/- decays, where [K-/+ pi+/-]_D indicates that the K-/+ pi+/- pair originates from the decay of a D0 or D0bar. Results are based on 120 million Upsilon(4S) --> B Bbar decays collected with the BaBar detector at SLAC. We set an upper limit on the ratio R_Kpi = {Gamma(B+ --> [K- pi+]_D K+) + Gamma(B- --> [K+ pi-]_D K-)}/ {Gamma(B+ --> [K+ pi-]_D K+) + Gamma(B- --> [K- pi+]_D K-)} < 0.026 (90% C.L.). This constrains the amplitude ratio r_B = |A(B- --> D0bar K-)/A(B- --> D0 K-)| < 0.22 (90% C.L.), consistent with expectations. The small value of r_B favored by our analysis suggests that the determination of the Cabibbo-Kobayashi-Maskawa phase gamma from B --> D K will be difficult.