arXiv subjects

B. Aubert

Publications and source records attributed to B. Aubert.

At least 343 records · Page 19Linked to original sources

arXiv2005

Measurements of the B -> X_s gamma Branching Fraction and Photon Spectrum from a Sum of Exclusive Final States

Using 88.9 million BB events collected by the BaBar detector at the Y(4S), we measure the branching fraction for the radiative penguin process B -> X_s gamma from the sum of 38 exclusive final states. The inclusive branching fraction above a minimum photon energy E_gamma > 1.9 GeV is BF (b -> s gamma) = (3.27 +/- 0.18 (stat.) +0.55/-0.40 (syst.) +0.04/-0.09 (theory)) 10^-4. We also measure the isospin asymmetry between B^- -> X_s ubar gamma and B^0bar -> X_s dbar gamma to be Delta_0- = -0.006 +/- 0.058 (stat.) +/- 0.009 (syst.) +/- 0.024 (B^0bar / B^-). The photon energy spectrum is measured in the B rest frame, from which moments are derived for different values of the minimum photon energy. We present fits to the photon spectrum and moments which give the heavy-quark parameters m_b and mu_pi^2. The fitted parameters are consistent with those obtained from semileptonic B -> X_c l nu decays, and are useful inputs for the extraction of Vub from measurements of semileptonic B -> X_u l nu decays.

hep-ex↗

arXiv2005

Dalitz Plot Analysis of D0-->K0bar K+ K-

A Dalitz plot analysis of approximately 12500 D0 events reconstructed in the hadronic decay D0-->K0bar K+ K- is presented. This analysis is based on a data sample of 91.5 fb-1 collected with the BaBar detector at the PEP-II asymmetric-energy e+ e- storage rings at SLAC running at center-of-mass energies on and 40 MeV below the Y4S resonance. The events are selected from e+ e- --> c cbar annihilations using the decay D*+ --> D0 pi+. The following ratio of branching fractions has been obtained: BR = Gamma(D0-->K0bar K+ K-)/Gamma(D0-->K0bar pi+ pi-) = (15.8+/-0.1(stat.)+/-0.5(syst.)x 10-2 Estimates of fractions and phases for resonant and non-resonant contributions to the Dalitz plot are also presented. The a0(980)-->K Kbar projection has been extracted with little background. A search for CP asymmetries on the Dalitz plot has been performed.

hep-ex↗

arXiv2005

Observation of a Broad Structure in the $π^+π^-J/ψ$ Mass Spectrum around 4.26 GeV/$c^2$

We study initial-state radiation events, $e^+e^- \to γ_{ISR}π^+π^-J/ψ$, with data collected with the BaBar detector. We observe an accumulation of events near 4.26 GeV/$c^2$ in the invariant-mass spectrum of $π^+π^-J/ψ$. Fits of the mass spectrum indicate that a broad resonance with a mass of about 4.26 GeV/$c^2$ is required to describe the observed structure. The presence of additional narrow resonances cannot be excluded. The fitted width of the broad resonance is 50 to 90 MeV/$c^2$, depending on the fit hypothesis.

hep-ex↗

arXiv2005

Measurement of the Cabibbo-Kobayashi-Maskawa angle gamma in B-+ -> D(*)K-+ decays with a Dalitz analysis of D -> K0s pi- pi+

We report on a measurement of the Cabibbo-Kobayashi-Maskawa CP-violating phase gamma through a Dalitz analysis of neutral D decays to K0s pi- pi+ in the processes B-+ -> D(*)K-+, D* -> D pi0, D gamma. Using a sample of 227 million BBbar pairs collected by the BaBar detector, we measure the amplitude ratios rB = 0.12+/-0.08+/-0.03+/-0.04 and rB* = 0.17+/-0.10+/-0.03+/-0.03, the relative strong phases deltaB = 104+/-45+17-21+16-24, and deltaB*= -64+/-41+14-12+/-15 between the amplitudes A(B- -> Dbar(*)0 K-) and A(B- -> D(*)0 K-), and gamma = 70+/-31+12-10+14-11. The first error is statistical, the second is the experimental systematic uncertainty and the third reflects the Dalitz model uncertainty. The results for the strong and weak phases have a two-fold ambiguity.

hep-ex↗

arXiv2005

Amplitude Analysis of the Decay B+- -> pi+- pi+- pi-+

We present a Dalitz-plot analysis of charmless B+- decays to the final state pi+- pi+- pi-+ using 210 fb^-1 of data recorded by the BABAR experiment at sqrt(s) = 10.58 GeV. We measure the branching fractions B(B+- -> pi+- pi+- pi-+) = (16.2 +- 1.2 +- 0.9) x 10^-6 and B(B+- -> rho^0(770) pi+-) = (8.8 +- 1.0 +- 0.6 +0.1-0.7) x 10^-6. Measurements of branching fractions for the quasi-two-body decays B+- -> rho^0(1450) pi+-, B+- -> f_0(980) pi+- and B+- -> f_2(1270) pi+- are also presented. We observe no charge asymmetries for the above modes, and there is no evidence for the decays B+- -> chic0 pi+-, B+- -> f_0(1370) pi+- and B+- -> sigma pi+-.

hep-ex↗

arXiv2005

Improved Measurements of Branching Fractions for B0 -> pi+pi-, K+pi-, and Search for K+K- at BaBar

We present preliminary measurements of branching fractions for the charmless two-body decays B0 -> pi+pi- and K+pi-, and a search for B0 -> K+K- using a data sample of approximately 227 million BBbar decays. Signal yields are extracted with a multi-dimensional maximum likelihood fit, and the efficiency is corrected for the effects of final-state radiation. We find the charge-averaged branching fractions (in units of 10^{-6}): Br(B0 -> pi+pi-) = 5.5 +- 0.4 +- 0.3, Br(B0 -> K+pi-) = 19.2 +- 0.6 +- 0.6, Br(B0 -> K+K-) = < 0.40. The errors are statistical followed by systematic, and the upper limit on K+K- represents a confidence level of 90%.

hep-ex↗

arXiv2005

Search for b->u transitions in B- -> D0 K- and B- -> D*0 K-

We search for B- ==> \tilde{D0}K- and B- ==> \tilde{D*0}K-, with \tilde{D*0} ==> \tilde{D0}pi0 or \tilde{D*0} ==> \tilde{D0}gamma, and \tilde{D0} ==> K+pi- (and charge conjugates). These final states can be reached through the b==>c transition B- ==> D0(*)K- followed by the doubly CKM-suppressed D0 ==> K+pi-, or the b==>u transition B- ==> D0bar(*)K- followed by the CKM-favored D0bar ==> K+pi-. The interference of these two amplitudes is sensitive to the angle gamma of the unitarity triangle. Our results are based on 232 million Upsilon(4S)==>BBbar decays collected with the BaBar detector at SLAC. We find no significant evidence for these decays. We set a limit r_B = |A(B- ==> D0bar K-)/A(B- ==> D0 K-)| < 0.23 at 90% C.L. using the most conservative assumptions on the values of the CKM angle gamma and the strong phases in the B and D decay amplitudes. In the case of the D* we set a 90% C.L. limit r*_B^2 = |A(B- ==> D*0bar K-)/A(B- ==> D*0 K-)|^2 < (0.16)^2 which is independent of assumptions on gamma and strong phases.

hep-ex↗

arXiv2005

Measurement of CP Asymmetries in B0-> KS pi0 pi0 Decays

We present a preliminary measurement of the time-dependent CP asymmetry for the neutral B-meson decay into the CP = +1 final state KS pi0 pi0, with KS-> pi+ pi- and pi0-> gamma gamma. We use a sample of approximately 227 million B-meson pairs recorded at the Y(4S) resonance by the BaBar detector at the PEP-II B-Factory at SLAC. From a maximum likelihood fit we extract the mixing-induced CP-violation parameter S = 0.84 +/- 0.71(stat} +/- 0.08{syst) and the direct CP-violation parameter C = 0.27 +/- 0.52(stat) +/- 0.13(syst}, where the first uncertainty is statistical and the second systematic.

hep-ex↗

arXiv2005

Measurement of the B0 --> pi- l+ nu and B+ --> pi0 l+ nu Branching Fractions and Determination of |V_ub| in Y(4S) Events Tagged by a Fully Reconstructed B Meson

We report preliminary measurements of the charmless exclusive semileptonic branching fractions of the B0 --> pi- l+ nu and B+ --> pi0 l+ nu decays, based on 211 fb-1 of data collected at the Y(4S) resonance by the BABAR detector. In events in which the decay of one B meson 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 and a pion. We measure the partial branching fractions for B0 --> pi- l+ nu and B+ --> pi0 l+ nu in three regions of the invariant mass squared of the lepton pair, and we obtain the total branching fractions BF(B0 --> pi- l+ nu) = (1.14 +/- 0.27(stat) +/- 0.17(syst)) x 10^-4 and BF(B+ --> pi0 l+ nu) = (0.86 +/- 0.22(stat) +/- 0.11(syst)) x 10^-4. Using isospin symmetry, we measure the combined total branching fraction BF(B0 --> pi- l+ nu) = (1.28 +/- 0.23(stat) +/- 0.16(syst)) x 10^-4. Theoretical predictions of the form-factor are used to determine the magnitude of the Cabibbo-Kobayashi-Maskawa matrix element |V_ub| = (3.7 +/- 0.3(stat) +/- 0.2(syst) +0.8-0.5(FF)) x 10^-3, where the last error is due to the form-factor normalization.

hep-ex↗

arXiv2005

A Study of b --> c and b -->u Interference in the Decay B- --> [K+ pi-]_D K*-

Using a sample of 232 x 10^6 Upsilon(4S)--> B B-bar events collected with the BABAR detector at the PEP-II B-factory we study the decay B- --> [K+ pi-]_D K*- where the K+ pi- is either from a Cabibbo-favored D0-bar decay or doubly-suppressed D0 decay. We measure two observables that are sensitive to the CKM angle gamma; the ratio R of the charge-averaged branching fractions for the suppressed and favored decays; and the charge asymmetry A of the suppressed decays: R=0.046 +/- 0.031(stat.) +/- 0.008(syst.) A=-0.22 +/- 0.61(stat.) +/- 0.17(syst.).

hep-ex↗

arXiv2005

Measurement of gamma in B-+ -> D() K-+ and B-+ -> D K-+ decays with a Dalitz analysis of D -> Ks pi- pi+

We present a measurement of the Cabibbo-Kobayashi-Maskawa CP-violating phase gamma with a Dalitz plot analysis of neutral D-meson decays to the Ks pi- pi+ final state from B-+ -> D(*) K-+ and B-+ -> D K*-+ decays, using a sample of 227 million BBbar pairs collected by the BaBar detector. We measure gamma = 67 +/- 28 +/- 13 +/- 11, where the first error is statistical, the second is the experimental systematic uncertainty and the third reflects the Dalitz model uncertainty. This result suffers from a two-fold ambiguity. The contribution to the Dalitz model uncertainty due to the description of the pipi S-wave in D0 -> Ks pi- pi+, evaluated using a K-matrix formalism, is found to be 3 degrees.

hep-ex↗

arXiv2005

Dalitz Plot Study of B0 --> K+K-K0S Decays

We present a study of the dynamics in B0 --> K+ K- K0S decays with approximately 230 million BBbar events collected by the BABAR detector at SLAC. We find that the Dalitz plot distribution is best parameterized with the phi K0S mode, an S-wave K+ K- resonance near 1500 MeV/c^2, and a large non-resonant contribution. We set limits on resonances not included in our model, and study models for the non-resonant contribution.

hep-ex↗

arXiv2005

Measurement of Double Charmonium Production in $e^+e^-$ Annihilations at $\sqrt{s}=10.6$ GeV

We study $e^+e^-\to J/ψc\bar{c}$ by measuring the invariant mass distribution recoiling against fully reconstructed $J/ψ$ decays, using 124 fb$^{-1}$ of data collected with a center-of-mass energy of 10.6 GeV with the $BaBar$ detector. We observe signals for $η_c(1S)$, $χ_{c0}$, and $η_c(2S)$ in the recoil mass distribution, thus confirming previous measurements. We measure $σ(e^+e^-\to J/ψ+c\bar{c}) {\cal B} (c\bar{c} \to >2 \mathrm{charged})$ to be $17.6\pm2.8\textrm{(stat)}^{+1.5}_{-2.1}\textrm{(syst)}$ fb, $10.3\pm2.5\textrm{(stat)}^{+1.4}_{-1.8}\textrm{(syst)}$ fb, and $16.4\pm3.7\textrm{(stat)}^{+2.4}_{-3.0}\textrm{(syst)}$ fb with $c\bar{c}=η_c(1S)$, $χ_{c0}$, and $η_c(2S)$, respectively.

hep-ex↗

arXiv2005

Measurement of Time-Dependent CP-Violating Asymmetries in B0 Meson Decays to eta'K0L

We present a preliminary measurement of CP-violating parameters S and C from fits of the time-dependence of B0 meson decays to eta'K0L. The data were recorded with the BABAR detector at PEP-II and correspond to 232 10^6 BBbar pairs produced in e+e- annihilation through the Y(4S) resonance. By fitting the time-dependent CP asymmetry of the reconstructed B0 --> eta'K0L events, we find S = 0.60 +- 0.31 +- 0.04 and C = 0.10 +- 0.21 +- 0.03, where the first error quoted is statistical and the second is systematic. We also perform a combined fit using both eta'K0S and eta'K0L data, and find S = 0.36 +- 0.13 +- 0.03 and C = -0.16 +- 0.09 +- 0.02.

hep-ex↗

arXiv2005

Measurements of the Branching Fraction and Time-Dependent CP-Asymmetries of B0->J/Psi pi0 Decays

We present measurements of the branching fraction and time-dependent CP asymmetries in B0->J/Psi pi0 decays based on (231.8 +/- 2.6)*10^6 Upsilon(4S) -> BBbar decays collected with the BaBar detector at the PEP-II asymmetric-energy B factory at SLAC during the years 1999-2004. We obtain a branching fraction B(B0->J/Psi pi0) = (1.94 +/- 0.22 (stat) +/- 0.17 (syst))*10^-5. We also measure the CP asymmetry parameters C = -0.21 +/- 0.26 (stat) +/- 0.09 (syst) and S = -0.68 +/- 0.30 (stat) +/- 0.04 (syst). All results presented in this paper are preliminary.

hep-ex↗

arXiv2005

Measurement of CP-voilating parameters in fully reconstructed B->D(*)+-pi-+ and B->D+-rho-+ decays

We present a preliminary measurement of the CP-violating parameters in fully reconstructed B->D^(*)+-pi-+ and B->D^+-rho-+ decays in approximately 232 million Y(4S)->BBbar$ decays collected with the BaBar detector at the PEP-II asymmetric-energy B factory at SLAC. From a maximum likelihood fit to the time-dependent decay distributions we obtain for the parameters related to the CP violation quantity sin(2beta+gamma): a[Dpi] = -0.013 +/- 0.022 (stat.) +/- 0.007 (syst.), clep[Dpi] = -0.043 +/- 0.042 (stat.) +/- 0.011 (syst.), a[D*pi] = -0.043 +/- 0.023 (stat.) +/- 0.010 (syst.), clep[D*pi] = 0.047 +/- 0.042 (stat.) +/- 0.015 (syst.), a[Drho] = -0.024 +/- 0.031 (stat.) +/- 0.010 (syst.), clep[Drho] = -0.098 +/- 0.055 (stat.) +/- 0.019 (syst.).

hep-ex↗

arXiv2005

Measurement of Time-dependent CP-Violating Asymmetries in B^0 -> K^0_S K^0_S K^0_S Decays

We present preliminary measurements of the CP asymmetry parameters in B^0 -> K^0_S K^0_S K^0_S decays, reconstructing two of the K^0_S into pi^+pi^- and one into pi^0pi^0. In a sample of 227M $B\bar B$ pairs collected by the BABAR detector at the PEP-II B-Factory at SLAC, we find the CP parameters to be S = -0.25^{+0.68}_{-0.61} (stat) +/- 0.05 (syst) and C = 0.56^{+0.34}_{-0.43} (stat) +/- 0.04 (syst). Combining this result with the previous BABAR measurement, obtained from events with three K^0_S decaying into pi^+pi^-, we get S = -0.63^{+0.32}_{-0.28} (stat) +/- 0.04(syst) C = -0.10 +/- 0.25 (stat) +/- 0.05 (syst)

hep-ex↗

arXiv2005

Measurement of the Branching Fraction of Upsilon(4S) --> B0B0bar

We report the first measurement of the branching fraction f00 for Upsilon(4S) --> B0B0bar. The data sample consists of 81.7 fb^-1 collected at the Upsilon(4S) resonance with the BABAR detector at the PEP-II asymmetric-energy e^+e^- storage ring. Using partial reconstruction of the decay B0bar --> D^{*+} \ell^{-} \barν_{\ell} in which only the charged lepton and the soft pion from the decay D^{*+} --> D0 pi^+ are reconstructed, we obtain f00 = 0.487 \pm 0.010(stat) \pm 0.008(sys). Our result does not depend on the branching fractions of B0bar --> D^{*+} \ell^{-} \barν_{\ell} and D^{*+} --> D0 pi^+ decays, on the ratio of the charged and neutral B meson lifetimes, nor on the assumption of isospin symmetry.

hep-ex↗