We present a new, completely revised calculation of the muon anomalous magnetic moment, \(a_\mu=(g_{\mu}-2)/2\), comparing it with the more recent experimental determination of this quantity; this ...furnishes an important test of theories of strong, weak and electromagnetic interactions. These theoretical and experimental determinations give the very precise numbers, $$10^{11}\times a_\mu=\cases{116 591 806\pm50\pm10 ({\rm rad.})\pm30 (\ell\times\ell)\quad\hbox{Th., no \(\tau\)}\cr 116 591 889\pm49\pm10 ({\rm rad.})\pm30 (\ell\times\ell)\quad\hbox{Theory, \(\tau\)}\cr 116 592 080\pm60\quad\hbox{Experiment}.\cr}$$ In the theoretical evaluations, the first quantity does not, and the second one does, use information from \(\tau\) decay. The first errors for the theoretical evaluations include statistical plus systematic errors; the other ones are the estimated errors due to incomplete treatment of radiative corrections and the estimated error in the light-by-light scattering contribution. We thus have a significant mismatch between theory and experiment. We also use part of the theoretical calculations to give a precise evaluation of the electromagnetic coupling on the \(Z\), \(\bar{\alpha}_{\rm Q.E.D.}(M^2_{Z})\), of the masses and widths of the (charged and neutral) rho resonances, of the scattering length and effective range for the P wave in \(\pi\pi\) scattering, and of the quadratic radius and second coefficient of the pion form factor.
Two drift tubes (DTs) chambers of the CMS muon barrel system were exposed to a 40
MHz bunched muon beam at the CERN SPS, and for the first time the whole CMS Level-1 DTs-based trigger system chain ...was tested. Data at different energies and inclination angles of the incident muon beam were collected, as well as data with and without an iron absorber placed between the two chambers, to simulate the electromagnetic shower development in CMS. Special data-taking runs were dedicated to test for the first time the Track Finder system, which reconstructs track trigger candidates by performing a proper matching of the muon segments delivered by the two chambers. The present paper describes the results of these measurements.
Fine synchronization of the CMS muon drift tubes local trigger Aldaya, M.; Amapane, N.; Battilana, C. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
08/2006, Letnik:
564, Številka:
1
Journal Article
Recenzirano
The drift tubes based CMS barrel muon trigger, which uses self-triggering arrays of drift tubes, is able to perform the identification of the muon parent bunch crossing using a rather sophisticated ...algorithm. The identification is unique only if the trigger chain is correctly synchronized. Some beam test time was devoted to take data useful to investigate the synchronization of the trigger electronics with the machine clock. Possible alternatives were verified and the dependence on muon track properties was studied.
We perform a new calculation of the hadronic contributions, \(a({\rm Hadronic})\) to the anomalous magnetic moment of the muon, \(a_\mu\). For the low energy contributions of order \(\alpha^2\) we ...carry over an analysis of the pion form factor \(F_\pi(t)\) using recent data both on \(e^+e^-\to\pi^+\pi^-\) and \(\tau^+\to \bar{\nu}_\tau \pi^+\pi^0\). In this analysis we take into account that the phase of the form factor is equal to that of \(\pi\pi\) scattering. This allows us to profit fully from analyticity properties so we can use also experimental information on \(F_\pi(t)\) at spacelike \(t\). At higher energy we use QCD to supplement experimental data, including the recent measurements of \(e^+e^-\to {\rm hadrons}\) both around 1 GeV and near the \(\bar{c}c\) threshold. This yields a precise determination of the \(O(\alpha^2)\) and \(O(\alpha^2)+O(\alpha^3)\) hadronic part of the photon vacuum polarization pieces, $$10^{11}\times a^{(2)}({\rm h.v.p.})=6 909\pm64;\quad 10^{11}\times a^{(2+3)}({\rm h.v.p.})=7 002\pm66$$ As byproducts we also get the masses and widths of the \(\rho^0, \rho^+\), and very accurate values for the charge radius and second coefficient of the pion. Adding the remaining order \(\alpha^3\) hadronic contributions we find $$10^{11}\times a^{\rm theory}(\hbox{Hadronic})= 6 993\pm69\quad(e^+e^- + \tau + {\rm spacel.})$$ The figures given are obtained including \(\tau\) decay data. This is to be compared with the recent experimental value, $$10^{11}\times a^{\rm exp.}(\hbox{Hadronic})=7 174\pm150.$$
We perform a new, detailed calculation of the hadronic contributions to the running electromagnetic coupling, \(\bar{\alpha}\), defined on the Z particle (91 GeV). We find for the hadronic ...contribution, including radiative corrections, $$10^5\times \deltav_{\rm had.}\alpha(M_Z^2)= 2740\pm12,$$ or, excluding the top quark contribution, $$10^5\times \deltav_{\rm had.}\alpha^{(5)}(M_Z^2)= 2747\pm12.$$ Adding the pure QED corrections we get a value for the running electromagnetic coupling of $$\bar{\alpha}_{\rm Q.E.D.}(M_Z^2)= {{1}\over{128.965\pm0.017}}.$$
In this case report, we describe a tawny owl chick (Strix aluco) coming from a Wild Fauna Recovery Center with multiple congenital malformations in the limbs. The animal was unable to fly and showed ...marked malnutrition and poor general appearance. Physical, radiologic, and anatomic examinations showed osseous malformations including dislocation of radius and carpometacarpus with abnormal nonfunctional fixation of ligamentum propatagialis, absence of most parts of the bones of the manus in both wings, and twisted nonfused left tarsometatarsus with marked griphosis of digits. Routine toxicologic and pathologic examinations did not reveal a specific etiology.
Dijet production by almost real photons has been studied at HERA with the ZEUS detector. Jets have been identified using the cone algorithm. A cut on
x
γ
OBS, the fraction of the photon energy ...participating in the production of the two jets of highest transverse energy, is used to define cross sections sensitive to the parton distributions in the proton and in the photon. The dependence of the dijet cross sections on pseudorapidity has been measured for
x
γ
OBS ⩾ 0.75 and
x
γ
OBS < 0.75. The former is sensitive to the gluon momentum density in the proton. The latter is sensitive to the ginon in the photon. The cross sections are corrected for detector acceptance and compared to leading order QCD calculations.
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