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The BaBar Collaboration

Publications and source records attributed to The BaBar Collaboration.

At least 37 records · Page 2Linked to original sources

arXiv2009

Measurements of the $τ$ Mass and Mass Difference of the $τ^{+}$ and $τ^{-}$} at BaBar

We present the result from a precision measurement of the mass of the $τ$ lepton, $M_τ$, based on $423 fb^{-1}$ of data recorded at the $Υ(4S)$ resonance with the BaBar detector. Using a pseudomass endpoint method, we determine the mass to be $1776.68 \pm 0.12 (stat) \pm 0.41 (syst) MeV$. We also measure the mass difference between the $τ^+$ and $τ^-$, and obtain $(M_{τ^{+}}-M_{τ^{-}})/M^τ_{AVG} = (-3.4 \pm 1.3 (stat) \pm 0.3 (syst)) \times 10^{-4}$, where $M^τ_{AVG}$ is the average value of $M_{τ^+}$ and $M_{τ^-}$.

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arXiv2008

Search for Lepton Flavour Violating Decays $τ\to \ell K^0_S$ with the BaBar Experiment

A search for the lepton flavour violating decays $τ^- \to l^- K^0_{\scriptscriptstyle S}$ ($l = e$ or $μ$) has been performed using a data sample corresponding to an integrated luminosity of 469 ${fb}^{-1}$, collected with the {\slshape B\kern-0.1em{\smaller A}\kern-0.1em B\kern-0.1em{\smaller A\kern-0.2em R}} detector at the SLAC PEP-II $e^+e^-$ asymmetric energy collider. No statistically significant signal has been observed in either channel and the estimated upper limits on branching fractions are ${\cal B}(τ^- \to e^- K^0_{\scriptscriptstyle S}) < 3.3 \times 10^{-8}$ and ${\cal B}(τ^- \to μ^- K^0_{\scriptscriptstyle S}) < 4.0 \times 10^{-8}$ at 90% confidence level.

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arXiv2008

Searches for B meson decays to phiphi, phirho, phifzero(980), and fzero(980)fzero(980) final states

We present the results of searches for B decays to charmless final states involving phi, fzero(980), and charged or neutral rho mesons. The data sample corresponds to 384 million BBbar pairs collected with the babar detector operating at the PEP-II asymmetric-energy epem collider at SLAC. We find no significant signals and determine the following 90% confidence level upper limits on the branching fractions, including systematic uncertainties: B(B0->phiphi) < 2.0 x 10^-7, B(B+->phirho+) < 30 x 10^-7, B(B0->phirho0) < 3.3 x 10^-7, B(B0-phif0) x B(f0->pi+pi-) < 3.8 x 10^-7, and B(B0->f0f0) x B(f0->pi+pi-) x B(f0->K+K-) < 2.3 x 10^-7

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arXiv2008

Study of the pi+pi-J/psi Mass Spectrum via Initial-State Radiation at BABAR

We present an update of the study of the Y(4260) resonance, produced in the process $e^+e^-\toγ_{ISR} π^+π^-J/ψ$ using initial-state radiation events at the PEP-II $e^+e^-$ storage rings. This study is based on 454fb$^{-1}$ of data recorded with the {\slshape B\kern-0.1em{\smaller A}\kern-0.1em B\kern-0.1em{\smaller A\kern-0.2em R}} detector at a center-of-mass energy in the $Υ(4S)$ resonance region. From a fit with a single non-relativistic Breit-Wigner shape we obtain updated parameters for the Y(4260) resonance which are $m_Y = 4252 \pm6 ^{+2}_{-3}$MeV/c$^2$ and $Γ_Y = 105 \pm 18^{+4}_{-6}$MeV/c$^2$; we also measure ${\calB}(π^+π^-J/ψ)Γ_{e^+e^-} = (7.5\pm 0.9 \pm0.8)$ eV. We cannot confirm the recent BELLE observation of a broad structure around 4.05GeV/c$^2$ in this decay mode.

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arXiv2008

Search for Invisible Decays of a Light Scalar in Radiative Transitions Upsilon(3S) -> gamma A0

We search for a light scalar particle produced in single-photon decays of the Upsilon(3S) resonance through the process Upsilon(3S) -> gamma A0, A0 -> invisible. Such an object appears in Next-to-Minimal Supersymmetric extensions of the Standard Model, where a light CP-odd Higgs boson naturally couples strongly to b-quarks. If, in addition, there exists a light, stable neutralino, decays of A0 could be preferentially to an invisible final state. We search for events with a single high-energy photon and a large missing mass, consistent with a 2-body decay of Upsilon(3S). We find no evidence for such processes in a sample of 122*10^6 Upsilon(3S) decays collected by the BABAR collaboration at the PEP-II B-factory, and set 90% C.L. upper limits on the branching fraction B(Upsilon(3S) -> gamma A0)*B(A0 -> invisible) at (0.7-31)*10^{-6} in the mass range m(A0)<=7.8 GeV. The results are preliminary.

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arXiv2008

Measurement of the Branching Fraction, Polarization, and CP Asymmetries in B0->rho0rho0 Decay, and Implications for the CKM Angle alpha

We study B0->rho0rho0 decays in a sample of 465*10^6 Upsilon (4S)->BBbar events collected with the BABAR detector at the PEP-II asymmetric-energy e+e- collider located at the Stanford Linear Accelerator Center (SLAC). We measure the branching fraction B = (0.92 +/- 0.32 +/- 0.14)*10^{-6} and longitudinal polarization fraction f_L = 0.75^{+0.11}_{-0.14} +/- 0.04, where the first uncertainty is statistical and the second is systematic. The evidence for the B0->rho0rho0 signal has a significance of 3.1 standard deviations, including systematic uncertainties. We investigate the proper-time dependence of the longitudinal component in the decay and measure the CP-violating coefficients S^{00}_L = (0.3 +/- 0.7 +/- 0.2) and C^{00}_L = (0.2 +/- 0.8 +/- 0.3). We study the implication of these results for the unitarity triangle angle alpha.

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arXiv2008

Measurement of the tau -> 3pi eta nu Branching Fraction and a Search for a Second-Class Current in the tau -> eta'(958) pi nu Decay

The "τ\to 3πην" decay with the "η\to γγ" mode is studied using 384 fb^-1 of data collected by the BaBar detector. The branching fraction is measured to be (1.60+/-0.05+/-0.11)x10^-4. It is found that "τ\to f1 πνto 3πην" is the dominant decay mode with a branching fraction of (1.11+/-0.06+/-0.05)x10^-4. The first error on the branching fractions is statistical and the second systematic. In addition, a 90% confidence level upper limit on the branching fraction of the "τ\to η'(958) πν" decay is measured to be 7.2x10^-6. This last decay proceeds through a second-class current and is expected to be forbidden in the limit of isospin symmetry.

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arXiv2007

Study of B0 --> l+l'- decays (l,l' = e,mu)

We present a search for the decays B0 --> e+e-, B0 --> mu+ mu- and B0 --> e mu using data collected with the BABAR detector at the PEP-II e+e-collider at SLAC. Using a dataset corresponding to 384 x 10^6 BBbar pairs, we do not find evidence of any of the three decay modes. We obtain upper limit on the branching fractions, at 90% confidence level, of B(B0 --> e+e-)< 11.3 x 10^{-8}, B(B0 --> mu+ mu-) < 5.2 x 10^{-8}, and B(B0 --> e mu) < 9.2 x 10^{-8}.

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arXiv2007

Search for the decay B+ -> Kbar*0(892) K+

We report on a search for the process B+ -> Kbar*0(892) K+ using 232 10^6 Upsilon(4S) -> BBbar decays collected with the BaBar detector at the PEP-II asymmetric-energy B Factory at SLAC. From a signal yield of 25 +/- 13 [stat] +/- 7 [syst] B+ -> Kbar*0(892) (-> K- pi+) K+ events, we place an upper limit on the branching fraction BF(B+ -> Kbar*0(892) K+) of 1.1 10^-6, at the 90% confidence level.

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arXiv2007

Search for CP Violation in the Decays D0 --> K- K+ and D0 --> pi- pi+

We measure CP-violating asymmetries of neutral charmed mesons in the modes D0 --> K- K+ and D0 --> pi- pi+ with the highest precision to date by using D0 --> K- pi+ decays to correct detector asymmetries. An analysis of 385.8 fb-1 of data collected with the BaBar detector yields values of aCP(KK) = (0.00 +/- 0.34 (stat.) +/- 0.13 (syst.))% and aCP(pipi) = (-0.24 +/- 0.52 (stat.) +/- 0.22 (syst.))%, which agree with Standard Model predictions.

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arXiv2007

Measurement of ${CP}\xspace$ Violation Parameters with a Dalitz Plot Analysis of $B^\pm \to D_{π^+π^-π^0} K^\pm$

We report the results of a CP violation analysis of the decay B+/- --> D(pipipi0)K+/-, where D(pipipi0) indicates a neutral D meson detected in the final state pi+pi-pi0, excluding K_S pi0. The analysis makes use of 324 million e+e- --> BB events recorded by the BaBar experiment at the PEP-II e+e- storage ring. By analyzing the pi+pi-pi0 Dalitz plot distribution and the B+/- --> D(pipipi0)K+/- branching fraction and decay rate asymmetry, we calculate parameters related to the phase gamma of the CKM unitarity triangle. We also measure the magnitudes and phases of the components of the D0 --> pi+pi-pi0 decay amplitude.

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arXiv2006

Searches for B0 decays to eta K0, eta eta, eta' eta', eta phi, and eta' phi

We search for B0 meson decays into two-body combinations of K0, eta, eta', and phi mesons in 324 million B Bbar pairs collected with the BaBar detector at the PEP-II asymmetric-energy e+e- collider at SLAC. We measure the following branching fractions (upper limits at 90% confidence level) in units of 10^{-6}: Br(B0->eta K0) =1.8+0.7-0.6 +-0.1(2.9), Br(B0->eta eta)=1.1+0.5-0.4 +-0.1(1.8), Br(B0->eta phi)=0.1+-0.2 +-0.1(0.6), Br(B0->eta' phi)=0.2+0.4-0.3 +-0.1(1.0), Br(B0->eta' eta')=1.0+0.8-0.6 +-0.1(2.4), where the first error is statistical and the second systematic.

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arXiv2006

Measurement of the Branching Fraction and Photon Energy Moments of B->X_s gamma and A_{cp}(B->X_(s+d) gamma)

The photon spectrum in B -> X_s gamma decay, where X_s is any strange hadronic state, is studied using a data sample of 88.5 million e+e- -> Upsilon(4S) -> BBbar decays collected by the BaBar experiment at SLAC. The partial branching fraction, Delta B(B -> X_s gamma)=(3.67 +- 0.29(stat.) +- 0.34(sys.) +- 0.29(model)) times 10^-4, the first moment =2.288 +- 0.025 +- 0.017 +- 0.015 GeV and the second moment - ^2 =0.0328 +- 0.0040 +- 0.0023 +- 0.0036 GeV^2 are measured for the photon energy range 1.9 GeV < E_gamma < 2.7 GeV. They are also measured for narrower E_gamma ranges. The moments are then fit to recent theoretical calculations to extract the Heavy Quark Expansion parameters, m_b and mu_pi^2, and to extrapolate the partial branching fraction to E_gamma>1.6 GeV. In addition, the direct CP asymmetry A_CP(B -> X_(s+d) gamma) is measured to be -0.110 +- 0.115(stat.) +- 0.017(sys.).

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arXiv2006

A Search for the $B^0 \to e^+e^-γ$ and $B^0 \to μ^+μ^-γ$ Decays

With the BaBar detector at the PEP-II asymmetric $B$ Factory at SLAC, we present the first search for the decays $B^0\to\ell^+\ell^-γ$ ($l=e, μ$). Using a data set of 292 $fb^{-1}$ collected at the $Υ(4S)$ resonance, we find no significant signal and set the following branching fraction upper limits at 90% confidence level: $\mathcal{B}(B^0\to e^+e^-γ)<0.7\times 10^{-7}$ and $\mathcal{B}(B^0\to μ^+μ^-γ)<3.4\times 10^{-7}$.

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arXiv2006

Search for B Meson Decays to eta' eta' K

We describe searches for decays of B mesons to the charmless final states eta' eta' K. The data consist of 228 million B Bbar pairs produced in e+ e- annihilation, collected with the BaBar detector at the Stanford Linear Accelerator Center. The 90% confidence level upper limits for the branching fractions are Br(B0->eta' eta' K0)<31 10^{-6} and Br(B+->eta' eta' K+)<25 10^{-6}.

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arXiv2004

Measurement of Time-Dependent CP-Violating Asymmetries in B0 Meson Decays to eta' K0

We present a preliminary measurement of CP-violating parameters S and C from fits of the time-dependence of B0 meson decays to eta' K0. The data were recorded with the BaBar detector at PEP-II and correspond to 227 * 10^6 B-Bbar pairs produced in e+e- annihilation through the Upsilon(4S) resonance. From a maximum likelihood fit we measure the CP-violation parameters S = 0.27 +/- 0.14 (stat) +/- 0.03 (syst) and C = -0.21 +/- 0.10 (stat) +/- 0.03 (syst).

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arXiv2004

Measurement of the inclusive electron spectrum in charmless semileptonic B decays near the kinematic endpoint and determination of |Vub|

We study the inclusive electron spectrum of B->X_u e nu decays near the kinematic limit for B->X_c e nu transitions using a sample of 88 million Upsilon(4S) decays recorded by the BABAR detector at the PEP II e+e- storage rings. For the electron momentum interval of 2.0 - 2.6 GeV/c the partial branching fraction is measured to be DeltaB(B->X_u e nu) = (0.480 +/- 0.029_{stat} +/- 0.053_{syst})x10^{-3}. Combining this result on with measurements of the inclusive photon spectrum in B->X_s gamma transition we find |V_ub|=(3.94 +/- 0.25_{exp} +/- 0.37_{f_u} +/- 0.19_{theory})x10^{-3}, where the first error represents the combined statistical and systematic experimental uncertainty of the partial branching fraction measurement, the second refers to the uncertainty of the determination of the fraction f_u of the inclusive electron spectrum that falls within our cuts, and the third error is due to theoretical uncertainties in the QCD corrections, plus the uncertainty in the b-quark mass. All results are preliminary.

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arXiv2004

Determination of |Vub| in inclusive semileptonic B meson decays

We present a preliminary determination of the CKM matrix element |Vub| based on the analysis of semileptonic B decays from a sample of 88 million Upsilon(4S) decays collected with the BaBar detector at the e+e- storage ring. Charmless semileptonic B decays are selected using the electron energy E_e and the invariant mass q^2 of the electron-neutrino pair. The neutrino momentum is inferred from a measurement of the visible energy and momentum in the detector and knowledge of the e+e- beam momenta. The partial branching fraction is determined in a region of the q^2-E_e plane where semileptonic B decays to charm are highly suppressed. The total charmless semileptonic branching fraction is extracted using a theoretical calculation based on the heavy quark expansion. Preliminary results yield |Vub| = (4.57 +/- 0.21 +/- 0.25 +/- 0.34 +0.59/-0.29 +/- 0.22) x 10^{-3} where the uncertainties are from statistics (data and MC), detector modeling, background modeling, the shape function, and the heavy quark operator product expansion, respectively.

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