We have performed a search for the η b ( 1 S ) meson in the radiative decay of the Υ ( 2 S ) resonance using a sample of 91.6 × 10 6 Υ ( 2 S ) events recorded with the BABAR detector at the PEP-II B ...factory at the SLAC National Accelerator Laboratory. We observe a peak in the photon energy spectrum at E γ = 609.3 + 4.6 − 4.5 ( stat ) ± 1.9 ( syst ) MeV , corresponding to an η b ( 1 S ) mass of 9394.2 + 4.8 − 4.9 ( stat ) ± 2.0 ( syst ) MeV / c 2 . The branching fraction for the decay Υ ( 2 S ) → γ η b ( 1 S ) is determined to be 3.9 ± 1.1 ( stat ) + 1.1 − 0.9 ( syst ) × 10 − 4 . We find the ratio of branching fractions B Υ ( 2 S ) → γ η b ( 1 S ) / B Υ ( 3 S ) → γ η b ( 1 S ) = 0.82 ± 0.24 ( stat ) + 0.20 − 0.19 ( syst ) .
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.
The upgrade of the Belle II forward calorimeter Manoni, E.; Aloisio, A.; Baccaro, S. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
02/2017, Letnik:
845
Journal Article
Recenzirano
The new facility SuperKEKB will be an upgrade of the existing KEKB electron–positron asymmetric collider, with a target luminosity of 8×1035cm−2s−1, about 40 times greater than that of KEKB. The ...detector will also be upgraded to cope with the higher luminosity, pile-up and occupancy. We report here on the design and development of the new pure CsI calorimeter for the forward region. An intensive R&D is being carried on to study the performance of pure CsI crystals with Avalanche Photodiodes readout. Results about the relative energy resolution of this detector, along with radiation hardness studies of all the components, are presented. A matrix of 16 crystals has been put on an electron beam at the BTF facility in Frascati and results in terms of energy resolution of this prototype are also discussed.
Here we perform the first measurement on the D0-D0 mixing parameters using a time-dependent amplitude analysis of the decay D0→π+π-π0. The data were recorded with the BABAR detector at center-of-mass ...energies at and near the $Y$(4S) resonance, and correspond to an integrated luminosity of approximately 468.1 fb-1. The neutral D meson candidates are selected from D*(2010)+→D0π$+\atop{s}$ decays where the flavor at the production is identified by the charge of the low-momentum pion, π$+\atop{s}$. The measured mixing parameters are x=(1.5±1.2±0.6)% and y=(0.2±0.9±0.5)%, where the quoted uncertainties are statistical and systematic, respectively.
We study the process e+e- -> pi+pi-pi+pi-gamma, with a photon emitted from the initial-state electron or positron, using 454.3 fb^-1 of data collected with the BABAR detector at SLAC, corresponding ...to approximately 260,000 signal events. We use these data to extract the non-radiative sigma(e+e- ->pi+pi-pi+pi-) cross section in the energy range from 0.6 to 4.5 Gev. The total uncertainty of the cross section measurement in the peak region is less than 3%, higher in precision than the corresponding results obtained from energy scan data.
Using a sample of (470.9±2.8)×106 BB¯ pairs, we measure the decay branching fraction B(B0→D*−π+π−π+)=(7.26±0.11±0.31)×10−3, where the first uncertainty is statistical and the second is systematic. ...Our measurement will be helpful in studies of lepton universality by measuring B(B0→D*−τ+ντ) using τ+→π+π−π+ν¯τ decays, normalized to B(B0→D*−π+π−π+).
We search for a light Higgs boson A 0 in the radiative decay Υ ( 3 S ) → γ A 0 , A 0 → τ + τ − , τ + → e + ν e ¯ ν τ , or τ + → μ + ν μ ¯ ν τ . The data sample contains 122 × 10 6 Υ ( 3 S ) events ...recorded with the BABAR detector. We find no evidence for a narrow structure in the studied τ + τ − invariant mass region of 4.03 < m τ + τ − < 10.10 GeV / c 2 . We exclude at the 90% confidence level (C.L.) a low-mass Higgs boson decaying to τ + τ − with a product branching fraction B ( Υ ( 3 S ) → γ A 0 ) × B ( A 0 → τ + τ − ) > ( 1.5 - 16 ) × 10 − 5 across the m τ + τ − range. We also set a 90% C.L. upper limit on the τ + τ − decay of the η b at B ( η b → τ + τ − ) < 8 % .
Recent investigations have suggested that the six-quark combination uuddss could be a deeply bound state (S) that has eluded detection so far, and a potential dark matter candidate. We report the ...first search for a stable, doubly strange six-quark state in Υ→S$\bar{Λ}\bar{Λ}$ decays based on a sample of 90×10$^{6}$Υ(2S) and 110×106Υ(3S) decays collected by the BABAR experiment. No signal is observed, and 90% confidence level limits on the combined Υ(2S,3S) → S$\bar{Λ}\bar{Λ}$ branching fraction in the range (1.2-1.4) × 10-7 are derived for mS < 2.05 GeV. These bounds set stringent limits on the existence of such exotic particles.
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