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Register a new userRecent BABAR results on measurement of exclusive hadronic cross sections
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Authors
Denis Bernard
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The measurement of exclusive $e^+e^-$ to hadrons processes is a significant part of the physics program of $BABAR$ experiment, aimed to improve the calculation of the hadronic contribution to the muon $g-2$ and to study the intermediate dynamics of the processes. We present the most recent results obtained by using the full data set of about 470,fb$^{-1}$ collected by the BABAR detector at the PEP-II $e^+e^-$ collider at a center-of-mass energy of about 10.6 GeV. In particular, we report the results on $e^+e^-$ annihilation into six- and seven-pion final states. The study of the very rich dynamics of these processes can help to understand the difference seen between the QCD prediction and the sum of exclusive cross sections in the energy region around 2 GeV, thus improving the precision on the total hadronic cross section and of the $g-2$ calculation. Additionally, we report the results on a dedicated study to shed light on the resonant states production in the energy region around 2.2 GeV, which is presently rather unclear. We measure the reaction $e^+e^-to K_SK_L$ with data collected with the $BABAR$ detector and analyse these data in conjunction with published BESIII data on $e^+e^-to K^+K^-$ and $BABAR$ data on $e^+e^-to K^+K^-$, $pi^+pi^-$, $pi^+pi^-eta$, $pi^+pi^-omega$. This study supports the existence of an isovector resonance $rho(2230)$ consistent with the resonance observed by BESIII.
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We present a review of recent results from BaBar experiment. BaBar detector has collected about 256 millions of $Bbar B$ events at PEP-II, the asymmetric $e^+e^-$ collider located at SLAC running at the $Upsilon(4S)$ resonance. We have studied CP violation in B mesons, observing the first evidence of direct CP violation in B meson decays and measured CP asymmetries relevant for the determination of the angles of the CKM Unitarity Triangle. BaBar physics program covers many other topics, including measurements of CKM matrix elements, charm physics, and search for new physics processes.
High-Q^2 NC and CC DIS cross sections have been measured by H1 and ZEUS at HERA. Both NC and CC results based on data taken during the year 1994-2000 are in good agreement with Standard Model expectations. The structure function xF_3 is extracted from the NC cross sections and the mass of the W propagator is extracted from the CC cross sections. Valence quark distributions are derived by means of an NLO QCD fit.
We present results on the Central Exclusive Production of charged particle pairs $h^{+}h^{-}$ ($h = pi, K, p$), $ppto p^prime+h^{+}h^{-}+p^prime$, obtained with the STAR experiment at RHIC in proton-proton collisions at a center-of-mass energy of $sqrt{s} = 200$ GeV. All final-state particles were reconstructed, including forward-scattered protons detected in the Roman Pot system. As a result, the Double Pomeron Exchange (DPE) events were selected and the non-exclusive backgrounds were efficiently rejected. Differential fiducial cross sections were measured as functions of observables related to the central hadronic final state and to the forward-scattered protons. The measured cross sections were compared to phenomenological model predictions based on the DPE. We also present preliminary results on the measurement of the same physics process at higher collision energy $sqrt{s} = 510$ GeV. The data demonstrate features similar to those observed at $sqrt{s} = 200$ GeV.
The cross sections for the reactions $e^+e^- to phieta, quad phieta, quad rhoeta, quad rhoeta$ have been measured using a data sample of 516 fb$^{-1}$ collected with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. The corresponding values of the cross sections are: $1.4 pm 0.4 pm 0.1$ fb $(phieta)$, $5.3 pm 1.1 pm 0.4$ fb $(phieta)$, $3.1 pm 0.5 pm 0.1$ fb $(rhoeta)$ and $3.3 pm 0.6 pm 0.2$ fb $(rhoeta)$. The energy dependence of the cross sections is presented using Belle measurements together with those of CLEO and BaBar.
We report about the studies of the decay channels B- -> D0 K-, B0 -> D*- a1+ and B0 -> Ds(*)- pi+ with a sample of 62.10^6 Upsilon(4S) decays into B meson pairs collected with the BaBar detector at the PEP II asymmetric e+ e- collider.
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