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Register a new userNew R values in 2-5 GeV from the BESII at BEPC
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Z.G. Zhao
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We report preliminary $R$ values for all 85 energy points scanned in the energy region of 2-5 GeV with the upgraded Beijing Spectrometer (BESII) at the Beijing Electron Positron Collider (BEPC). The typical uncertainty on the R values we measured is about 7%. The new R values have a significant impact on the predicted mass of the Higgs coming from the global fit to the electroweak data, and will also contribute to the interpretation of the E821 g-2 experiment.
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Final results of the measurement of $R = sigma(e^+e^- to hadrons) /sigma(e^+e^- to mu^+mu^-)$ in the energy region from 2 to 5 GeV with the upgraded Beijing Spectrometer (BESII) at the Beijing Electron Positron Collider (BEPC) are presented. Preliminary results of the inclusive momentum spectra and second binomial moment measured with the $R$ scan data at 2.2, 2.6, 3.0, 3.2, 4.6 and 4.8 GeV are reported.
We present recent results from the BES experiment on the observation of the Y(2175) in $J/psito phi f_0(980) eta$, and $eta(2225)$ in $J/psito gamma phi phi$, and X(1440) in $J/psi$ hadronic decays, together with the new observation of $psi(2S)$ radiative decays and hadronic decays into $nksldb+c.c., ldldbpi^0, ldldbeta$. The effort to search for $J/psi$ decays into $gammagamma$ and invisible decays are also reported.
Deep inelastic scattering and its diffractive component, $ep to e^{prime}gamma^* p to e^{prime}XN$, have been studied at HERA with the ZEUS detector using an integrated luminosity of 52.4 pb$^{-1}$. The $M_X$ method has been used to extract the diffractive contribution. A wide range in the centre-of-mass energy $W$ (37 -- 245 GeV), photon virtuality $Q^2$ (20 -- 450 GeV$^2$) and mass $M_X$ (0.28 -- 35 GeV) is covered. The diffractive cross section for $2 < M_X < 15$ GeV rises strongly with $W$, the rise becoming steeper as $Q^2$ increases. The data are also presented in terms of the diffractive structure function, $F^{rm D(3)}_2$, of the proton. For fixed $Q^2$ and fixed $M_X$, $xpom F^{rm D(3)}_2$ shows a strong rise as $xpom to 0$, where $xpom$ is the fraction of the proton momentum carried by the Pomeron. For Bjorken-$x < 1 cdot 10^{-3}$, $xpom F^{rm D(3)}_2$ shows positive $log Q^2$ scaling violations, while for $x ge 5 cdot 10^{-3}$ negative scaling violations are observed. The diffractive structure function is compatible with being leading twist. The data show that Regge factorisation is broken.
Using the KEDR detector at the VEPP-4M $e^+e^-$ collider, we have determined the values of $R$ at thirteen points of the center-of-mass energy between 1.84 and 3.05 GeV. The achieved accuracy is about or better than $3.9%$ at most of the energy points with a systematic uncertainty less than $2.4%$.
Quadrupole amplitudes in the $gamma^{*}NtoDelta$ transition are associated with the issue of nucleon deformation. A search for these small amplitudes has been the focus of a series of measurements undertaken at Bates/MIT by the OOPS collaboration. We report on results from H$(e,e^prime p)pi^0$ data obtained at $Q^2= 0.070$ (GeV/c)$^2$ and invariant mass of W=1155 MeV using the out-of-plane detection technique with the OOPS spectrometers. The $sigma_{LT}$ and $sigma_{T}+epsiloncdot$ $sigma_{L}$ response functions were isolated. These results, along with those of previous measurements at $W$=1172 MeV and $Q^2= 0.127$ (GeV/c)$^2$, aim in elucidating the interplay between resonant and non resonant amplitudes.
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