We describe a measurement of the time-integrated luminosity of the data collected by the BABAR experiment at the PEP-II asymmetric-energy e+e- collider at the Upsilon(4S), Upsilon(3S), and ...Upsilon(2S) resonances and in a continuum region below each resonance. We measure the time-integrated luminosity by counting e+e- --> e+e- and (for the Upsilon(4S) only) e+e- --> mu+mu- candidate events, allowing additional photons in the final state. We use data-corrected simulation to determine the cross sections and reconstruction efficiencies for these processes, as well as the major backgrounds. Due to the large cross sections of e+e- --> e+e- and +e- --> mu+mu-, the statistical uncertainties of the measurement are substantially smaller than the systematic uncertainties. The dominant systematic uncertainties are due to observed differences between data and simulation, as well as uncertainties on the cross sections. For data collected on the Upsilon(3S) and Upsilon(2S) resonances, an additional uncertainty arises due to Upsilon --> e+e- background. For data collected off the Upsilon resonances, we estimate an additional uncertainty due to the time-dependent efficiency variations, which can affect the short off-resonance runs.
We study the process $e^+e^-\to J/\psi\pi^{+}\pi^{-}$ with initial-state-radiation events produced at the PEP-II asymmetric-energy collider. The data were recorded with the BaBar detector at ...center-of-mass energies 10.58 and 10.54 GeV, and correspond to an integrated luminosity of 454 $\mathrm{fb^{-1}}$. We investigate the $J/\psi \pi^{+}\pi^{-}$ mass distribution in the region from 3.5 to 5.5 $\mathrm{GeV/c^{2}}$. Below 3.7 $\mathrm{GeV/c^{2}}$ the $\psi(2S)$ signal dominates, and above 4 $\mathrm{GeV/c^{2}}$ there is a significant peak due to the Y(4260). A fit to the data in the range 3.74 -- 5.50 $\mathrm{GeV/c^{2}}$ yields a mass value $4244 \pm 5$ (stat) $ \pm 4$ (syst)$\mathrm{MeV/c^{2}}$ and a width value $114 ^{+16}_{-15}$ (stat)$ \pm 7$(syst)$\mathrm{MeV}$ for this state. We do not confirm the report from the Belle collaboration of a broad structure at 4.01 $\mathrm{GeV/c^{2}}$. In addition, we investigate the $\pi^{+}\pi^{-}$ system which results from Y(4260) decay.
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.
Rare Decays and CP Violation in the B s System Borissov, Guennadi; Fleischer, Robert; Schune, Marie-Hélène
Annual review of nuclear and particle science,
01/2013, Letnik:
63, Številka:
1
Journal Article
Recenzirano
Odprti dostop
CP-violating phenomena and rare decays of B
0
s
mesons offer interesting probes to test the quark-flavor sector of the Standard Model. In view of the many new results reported, in particular from the ...Large Hadron Collider, this topic received a great deal of attention in 2012. We provide an overview of the most recent experimental results and new theoretical developments, and we discuss the prospects for future exploration of the B
0
s
meson system.
In this article we present the physics programs for LHCb and for an e+e− high luminosity asymmetric B factory. Using a few examples, we will show how the measurements which can be performed will ...allow us to study, in a unique manner, the structure of the New Physics beyond the Standard Model, if discovered at LHC with the general purpose detectors ATLAS and CMS, and/or eventually to extend the domain of the New Physics search to larger energy not accessible at LHC.
Dans cet article nous présentons le programme de physique de LHCb et celui dʼune future usine à B asymétriques e+e− à haute luminosité. En utilisant quelques exemples nous montrerons comment les mesures qui seront effectuées permettront dʼétudier la structure de la nouvelle physique au delà du Modèle Standard si elle est mise en évidence par les expériences ATLAS et CMS au LHC, et/ou dʼétendre le domaine de la recherche de la nouvelle physique à des énergies plus élevées et non accessibles au LHC.
The photon spectrum in the inclusive electromagnetic radiative decays of the B meson, B → X s γ plus B → X d γ , is studied using a data sample of ( 382.8 ± 4.2 ) × 10 6 Υ ( 4 S ) → B ¯¯¯ B decays ...collected by the BABAR experiment at SLAC. The spectrum is used to extract the branching fraction B ( B → X s γ ) = ( 3.21 ± 0.33 ) × 10 − 4 for E γ > 1.8 GeV and the direct C P asymmetry A C P ( B → X s + d γ ) = 0.057 ± 0.063 . The effects of detector resolution and Doppler smearing are unfolded to measure the photon energy spectrum in the B meson rest frame.
The first observation of the decays Λb0→χc 1p K- and Λb0→χc 2p K- is reported using a data sample corresponding to an integrated luminosity of 3.0 fb-1, collected by the LHCb experiment in p p ...collisions at center-of-mass energies of 7 and 8 TeV. The following ratios of branching fractions are measured: B/(Λb0→χc 1p K-) B (Λb0→J /ψ p K-) =0.242 ±0.014 ±0.013 ±0.009 ,B/(Λb0→χc 2p K-) B (Λb0→J /ψ p K-) =0.248 ±0.020 ±0.014 ±0.009 ,B/(Λb0→χc 2p K-) B (Λb0→χc 1p K-) =1.02 ±0.10 ±0.02 ±0.05 , where the first uncertainty is statistical, the second systematic, and the third due to the uncertainty on the branching fractions of the χc 1→J /ψ γ and χc 2→J /ψ γ decays. Using both decay modes, the mass of the Λb0 baryon is also measured to be mΛb0=5619.44 ±0.28 ±0.26 MeV /c2 , where the first and second uncertainties are statistical and systematic, respectively.
The CP asymmetry in the mixing of B0s and B̅0s mesons is measured in proton-proton collision data corresponding to an integrated luminosity of 3.0 fb−1, recorded by the LHCb experiment at ...centre-of-mass energies of 7 and 8 TeV. Semileptonic B0s and B̅0s decays are studied in the inclusive mode D∓sμ±νμX with the D∓s mesons reconstructed in the K+K−π∓ final state. Correcting the observed charge asymmetry for detection and background effects, the CP asymmetry is found to be assl=(0.39±0.26±0.20)%, where the first uncertainty is statistical and the second systematic. This is the most precise measurement of assl to date, and is consistent with the prediction from the Standard Model of particle physics.
The polarization of photons produced in radiative B-s(0) decays is studied for the first time. The data are recorded by the LHCb experiment in pp collisions corresponding to an integrated luminosity ...of 3 fb(-1) at center-of-mass energies of 7 and 8 TeV. A time-dependent analysis of the B-s(0) ->phi gamma decay rate is conducted to determine the parameter A(Delta), which is related to the ratio of right-over left-handed photon polarization amplitudes in b -> s gamma transitions. A value of A(Delta) = -0.98(-0.52)(-0.20)(+0.46)(+0.23) is measured. This result is consistent with the standard model prediction within 2 standard deviations.
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