We measure the mass difference Δm0 between the D*(2010)+ and the D0 and the natural linewidth Γ of the transition D*(2010)+ → D0π+. The data were recorded with the BABAR detector at center-of-mass ...energies at and near the Υ(4S) resonance, and correspond to an integrated luminosity of approximately 477 fb(-1). The D0 is reconstructed in the decay modes D0 → K- π+ and D0 → K- π+ π- π+. For the decay mode D0 → K- π+ we obtain Γ = (83.4±1.7±1.5) keV and Δm0 = (145425.6±0.6±1.7) keV, corrected where the quoted errors are statistical and systematic, respectively. For the D0 → K- π+ π- π+ mode we obtain Γ = (83.2±1.5±2.6) keV and Δm0 = (145426.6±0.5±1.9) keV. corrected The combined measurements yield Γ = (83.3±1.2±1.4) keV and Δm0 = (145425.9±0.4±1.7) keV; the width is a factor of approximately 12 times more precise than the previous value, while the mass difference is a factor of approximately 6 times more precise.
We present results of a search for CP violation in B0- B0 mixing with the BABAR detector. We select a sample of B0→D*- Xℓ+ ν decays with a partial reconstruction method and use kaon tagging to assess ...the flavor of the other B meson in the event. We determine the CP violating asymmetry ACP≡N(B0B0)-N(B0B0)/N(B0B0)+N(B0B0)=(0.06±0.17(-0.32)(+0.38))%, corresponding to ΔCP=1-|q/p|=(0.29±0.84(-1.61)(+1.88))×10(-3).
Optimally combined confidence limits Janot, P.; Le Diberder, F.
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
1998, Letnik:
411, Številka:
2
Journal Article
Recenzirano
An analytical and optimal procedure to combine statistically independent sets of confidence levels on a quantity is presented. This procedure does not impose any constraint on the methods followed by ...each analysis to derive its own limit. It incorporates the a priori statistical power of each of the analyses to be combined, in order to optimize the overall sensitivity. It can, in particular, be used to combine the mass limits obtained by several analyses searching for the Higgs boson in different decay channels, with different selection efficiencies, mass resolution and expected background. It can also be used to combine the mass limits obtained by several experiments (e.g. ALEPH, DELPHI, L3 and OPAL, at LEP 2) independently of the method followed by each of these experiments to derive their own limit. A method to derive the limit set by one analysis is also presented, along with an unbiased prescription to optimize the expected mass limit in the no-signal-hypothesis.
Belle II aerogel RICH detector Burmistrov, L.; Adachi, I.; Le Diberder, F. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2020, Letnik:
958
Journal Article
Recenzirano
The aerogel Ring Imaging CHerenkov counter (ARICH) is the particle identification device installed in the forward region of the Belle II detector at the SuperKEKB accelerator facility in Japan. The ...first electron–positron collisions at SuperKEKB took place on April 26, 2018, during the so called phase 2 run. The measured performance of the detector based on recorded Bhabha events during phase 2 is presented. We measure a 14 mrad average angular resolution per photon and 10 photons per Bhabha electron in the 6–8 GeV/c momentum range.
Development of alignment algorithm for Belle II Aerogel RICH counter Tamechika, S.; Adachi, I.; Burmistrov, L. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
02/2020, Letnik:
952
Journal Article
Recenzirano
We have developed an alignment algorithm for the Belle II Aerogel RICH (ARICH) counter using the Monte Carlo simulation of e+e−→μ+μ−. We applied the developed algorithm to the e+e−→e+e− data obtained ...at the commissioning of Belle II, and found the displacement and rotation of ARICH to be around 1mm and less than 0.01∘, respectively, which is consistent with the values estimated from mechanical tolerance.
A search is presented for the four-body decay B0→ppp¯p¯ in a sample of 471 million BB¯ pairs collected with the BABAR detector, operated at the SLAC PEP-II asymmetric-energy e+e− collider. The ...center-of-mass energy is 10.58 GeV. From a fit to the distribution of the energy-substituted mass mES, the branching fraction B(B0→ppp¯p¯)=(1.1±0.5±0.2)×10−7 is extracted, where the first uncertainty is statistical and the second is systematic. The significance of the signal, including the systematic uncertainty, is 2.9 standard deviations. The upper limit on the branching fraction is determined to be 2.0×10−7 at 90% confidence level.
A new dark sector antibaryon, denoted ψ_{D}, could be produced in decays of B mesons. This Letter presents a search for B^{+}→ψ_{D}+p (and the charge conjugate) decays in e^{+}e^{-} annihilations at ...10.58 GeV, using data collected in the BABAR experiment. Data corresponding to an integrated luminosity of 398 fb^{-1} are analyzed. No evidence for a signal is observed. Branching fraction upper limits in the range from 10^{-7}-10^{-5} are obtained at 90% confidence level for masses of 1.0<m_{ψ_{D}}<4.3 GeV/c^{2}. The result is also reinterpreted to provide the first limits on a supersymmetric model with R-parity violation and a light neutralino.
The DIRC particle identification system for the BaBar experiment Aleksan, R.; Amerman, L.; Aston, D. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
02/2005, Letnik:
538, Številka:
1-3
Journal Article
Recenzirano
Odprti dostop
A new type of ring-imaging Cherenkov detector is being used for hadronic particle identification in the BABAR experiment at the SLAC B Factory (PEP-II). This detector is called DIRC, an acronym for ...Detection of Internally Reflected Cherenkov (Light). This paper will discuss the construction, operation and performance of the BABAR DIRC in detail.
An angular analysis of the decay B¯→D*ℓ-ν¯ℓ, ℓ∈{e,μ}, is reported using the full e+e- collision data set collected by the BABAR experiment at the ϒ(4S) resonance. One B meson from the ϒ(4S)→BB¯ decay ...is fully reconstructed in a hadronic decay mode, which constrains the kinematics and provides a determination of the neutrino momentum vector. The kinematics of the semileptonic decay is described by the dilepton mass squared, q2, and three angles. The first unbinned fit to the full four-dimensional decay rate in the standard model is performed in the so-called Boyd-Grinstein-Lebed approach, which employs a generic q2 parametrization of the underlying form factors based on crossing symmetry, analyticity, and QCD dispersion relations for the amplitudes. A fit using the more model-dependent Caprini-Lellouch-Neubert (CLN) approach is performed as well. Our form factor shapes show deviations from previous fits based on the CLN parametrization. The latest form factors also provide an updated prediction for the branching fraction ratio R(D*)≡B(B¯→D*τ-ν¯τ)/B(B¯→D*ℓ-ν¯ℓ)=0.253±0.005. Finally, using the well-measured branching fraction for the B¯→D*ℓ-ν¯ℓ decay, a value of |Vcb|=(38.36±0.90)×10-3 is obtained that is consistent with the current world average for exclusive B¯→D(*)ℓ-ν¯ℓ decays and remains in tension with the determination from inclusive semileptonic B decays to final states with charm.
We report on the first search for electron-muon lepton flavor violation (LFV) in the decay of a b quark and b antiquark bound state. We look for the LFV decay Υ(3S)→e±μ∓ in a sample of 118 million ...Υ(3S) mesons from 27 fb-1 of data collected with the BABAR detector at the SLAC PEP-II e+e- collider operating with a 10.36 GeV center-of-mass energy. No evidence for a signal is found, and we set a limit on the branching fraction BΥ(3S)→e±μ∓<3.6×10-7 at 90% C. L. This result can be interpreted as a limit ΛNP/gNP2>80 TeV on the energy scale ΛNP divided by the coupling-squared gNP2 of relevant new physics (NP).
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