We study the process e+e−→π+π−ηγ, where the photon is radiated from the initial state. About 8000 fully reconstructed events of this process are selected from the BABAR data sample with an integrated ...luminosity of 469 fb−1. Using the π+π−η invariant mass spectrum, we measure the e+e−→π+π−η cross section in the e+e− center-of-mass energy range from 1.15 to 3.5 GeV. The cross section is well described by the Vector-Meson dominance model with four ρ-like states. We observe 49±9 events of the J/ψ decay to π+π−η and measure the product ΓJ/Ψ→e+e−BJ/Ψ→π+π−η=2.34±0.43stat±0.16syst eV.
Using the initial-state radiation method, the e + e − → KSKL cross section from 1.98 to 2.54 GeV is measured in a data sample of 469 fb −1 collected with the BABAR detector. The results are used in ...conjunction with previous BABAR results for the e + e − → K + K − , e + e − → π + π − , e + e − → π + π − η , and e + e − → ω π π cross sections to investigate the nature of the resonance structure recently observed by the BESIII experiment in the e + e − → K+K− cross section.
We report a measurement of the time-dependent CP asymmetry of B¯0 → D$^{(*)}_{CP}$h0 decays, where the light neutral hadron h0 is a π0, η, or ω meson, and the neutral D meson is reconstructed in the ...CP eigenstates K+K–, K$^{0}_{S}$π0, or K$^{0}_{S}$ω. The measurement is performed combining the final data samples collected at the Υ(4S) resonance by the BABAR and Belle experiments at the asymmetric-energy B factories PEP-II at SLAC and KEKB at KEK, respectively. The data samples contain (471 ± 3) × 106 BB¯ pairs recorded by the BABAR detector and (772 ± 11) × 106 BB¯ pairs recorded by the Belle detector. We measure the CP asymmetry parameters –ηfS = +0.66 ± 0.10(stat) ± 0.06(syst) and C = –0.02 ± 0.07(stat) ± 0.03(syst). Here, these results correspond to the first observation of CP violation in B¯0 → D$^{(*)}_{CP}$h0 decays. The hypothesis of no mixing-induced CP violation is excluded in these decays at the level of 5.4 standard deviations.
We report measurements of sin2β and cos2β using a time-dependent Dalitz plot analysis of B0 → D ( * ) h0 with D → KS0π+π- decays, where the light unflavored and neutral hadron h0 is a π0 , η , or ω ...meson. The analysis uses a combination of the final data sets of the B a B ar and Belle experiments containing 471×106 and 772×106 B B ¯ pairs collected at the Υ ( 4S ) resonance at the asymmetric-energy B factories PEP-II at SLAC and KEKB at KEK, respectively. We measure 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 is β= ( 22.5±4.4 ( stat ) ±1.2 ( syst ) ±0.6 ( model ) ) ° . The last quoted uncertainties are due to the composition of the D0 → KS0π+π- decay amplitude model, which is newly established by a Dalitz plot amplitude analysis of a high-statistics e+e- → c c ¯ data sample as part of this analysis. We find the first evidence for cos2β>0 at the level of 3.7 standard deviations. The measurement excludes the trigonometric multifold solution π / 2-β= ( 68.1±0.7 ) ° 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 β=0° is ruled out at the level of 5.1 standard deviations, and thus CP violation is observed in B0 → D ( * ) h0 decays. The measurement assumes no direct CP violation in B0 → D ( * ) h0 decays.
We search for single-photon events in 53 fb^{-1} of e^{+}e^{-} collision data collected with the BABAR detector at the PEP-II B-Factory. We look for events with a single high-energy photon and a ...large missing momentum and energy, consistent with production of a spin-1 particle A^{'} through the process e^{+}e^{-}→γA^{'}; A^{'}→invisible. Such particles, referred to as "dark photons," are motivated by theories applying a U(1) gauge symmetry to dark matter. We find no evidence for such processes and set 90% confidence level upper limits on the coupling strength of A^{'} to e^{+}e^{-} in the mass range m_{A^{'}}≤8 GeV. In particular, our limits exclude the values of the A^{'} coupling suggested by the dark-photon interpretation of the muon (g-2)_{μ} anomaly, as well as a broad range of parameters for the dark-sector models.
We search for invisible decays of the Upsilon(1S) meson using a sample of 91.4 x 10(6) Upsilon(3S) mesons collected at the BABAR/PEP-II B factory. We select events containing the decay Upsilon(3S) ...--> pi(+)pi(-)Upsilon(1S) and search for evidence of an undetectable Upsilon(1S) decay recoiling against the dipion system. We set an upper limit on the branching fraction B(Upsilon(1S) --> invisible) < 3.0 x 10(-4) at the 90% confidence level.
The BaBar detector: Upgrades, operation and performance Couderc, F.; Prudent, X.; Groysman, Y. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
11/2013, Letnik:
729, Številka:
C
Journal Article
Recenzirano
Odprti dostop
The BaBar detector operated successfully at the PEP-II asymmetric e+e− collider at the SLAC National Accelerator Laboratory from 1999 to 2008. This report covers upgrades, operation, and performance ...of the collider and the detector systems, as well as the trigger, online and offline computing, and aspects of event reconstruction since the beginning of data taking.
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