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Register a new userMeasurement of the DA$Phi$NE luminosity with the KLOE detector using large angle Bhabha scattering
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KLOE Collaboration
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We describe the method of measuring the integrated luminosity of the $e^+e^-$ collider DA$Phi$NE, the Frascati $phi-$factory. The measurement is done with the KLOE detector selecting large angle Bhabha scattering events and normalizing them to the effective cross section. The $e^+e^- to e^+e^-(gamma)$ cross section is calculated using different event generators which account for the $O(alpha)$ radiative initial and final state corrections, and the $phi$ resonance contribution. The accuracy of the measurement is 0.6%, where 0.3% comes from systematic errors related to the event counting and 0.5% from theoretical evaluations of the cross section.
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Prospective presentation is given for the experimental program of the KLOE-2 Collaboration, to be performed using the DA$Phi$NE $e^+e^-$ collider upgraded in luminosity. Data with the total luminosity of 25 fb$^{-1}$ are aimed to be collected in 3 years. Major modifications of the accelerator and the spectrometer are described. The KLOE-2 physics program contains: CKM unitarity and lepton universality tests, $gammagamma$ physics, search for quantum decoherence and testing CPT conservation, low-energy QCD, rare kaon decays, physics of $eta$ and $eta^prime$, structure of low-mass scalars, contribution of vacuum polarization to $(g-2)_{mu}$, possible search for WIMP dark matter. In this paper only selected physics subjects are reported.
Investigation at a $phi$--factory can shed light on several debated issues in particle physics. We discuss: i) recent theoretical development and experimental progress in kaon physics relevant for the Standard Model tests in the flavor sector, ii) the sensitivity we can reach in probing CPT and Quantum Mechanics from time evolution of entangled kaon states, iii) the interest for improving on the present measurements of non-leptonic and radiative decays of kaons and eta/eta$^prime$ mesons, iv) the contribution to understand the nature of light scalar mesons, and v) the opportunity to search for narrow di-lepton resonances suggested by recent models proposing a hidden dark-matter sector. We also report on the $e^+ e^-$ physics in the continuum with the measurements of (multi)hadronic cross sections and the study of gamma gamma processes.
This document reviews the physics program of the KLOE-2 detector at DA$Phi$NE upgraded in energy and provides a simple solution to run the collider above the $phi$-peak (up to 2, possibly 2.5 GeV). It is shown how a precise measurement of the multihadronic cross section in the energy region up to 2 (possibly 2.5) GeV would have a major impact on the tests of the Standard Model through a precise determination of the anomalous magnetic moment of the muon and the effective fine-structure constant at the $M_Z$ scale. With a luminosity of about $10^{32}$cm$^{-2}$s$^{-1}$, DA$Phi$NE upgraded in energy can perform a scan in the region from 1 to 2.5 GeV in one year by collecting an integrated luminosity of 20 pb$^{-1}$ (corresponding to a few days of data taking) for single point, assuming an energy step of 25 MeV. A few years of data taking in this region would provide important tests of QCD and effective theories by $gammagamma$ physics with open thresholds for pseudo-scalar (like the $eta$), scalar ($f_0,f_0$, etc...) and axial-vector ($a_1$, etc...) mesons; vector-mesons spectroscopy and baryon form factors; tests of CVC and searches for exotics. In the final part of the document a technical solution for the energy upgrade of DA$Phi$NE is proposed.
Recently the peak luminosity achieved on the DA{Phi}NE collider has been improved by almost a factor three by implementing a novel collision scheme based on large Piwinski angle and Crab-Waist. This encouraging result opened new perspectives for physics research and a new run with the KLOE-2 detector has been scheduled to start by spring 2010. The KLOE-2 installation is a complex operation requiring a careful design effort and a several months long shutdown. The high luminosity interaction region has been deeply revised in order to take into account the effect on the beam caused by the solenoidal field of the experimental detector and to ensure background rejection. The shutdown has been also used to implement several other modifications aimed at improving beam dynamics: the wiggler poles have been displaced from the magnet axis in order to cancel high order terms in the field, the feedback systems have been equipped with stronger power supplies and more efficient kickers and electrodes have been inserted inside the wiggler and the dipole vacuum chambers, in the positron ring, to avoid the e-cloud formation. A low level RF feedback has been added to the cavity control in both rings.
A measurement of the vector to pseudoscalar conversion decay $phi to pi^0 e^+e^-$ with the KLOE experiment is presented. A sample of $sim 9500$ signal events was selected from a data set of 1.7 fb$^{-1}$ of $e^+e^-$ collisions at $sqrt{s} sim m_{phi}$ collected at the DA$Phi$NE $e^+e^-$ collider. These events were used to obtain the first measurement of the transition form factor $| F_{phi pi^0}(q^2) |$ and a new measurement of the branching ratio of the decay: $rm{BR},(phi to pi^0 e^+e^-) = (,1.35 pm 0.05^{,,+0.05}_{,,-0.10},) times 10 ^{-5}$. The result improves significantly on previous measurements and is in agreement with theoretical predictions.
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