Search results for "Muon"
showing 10 items of 1376 documents
Measurements of single top quark production cross sections and|Vtb|inpp¯collisions ats=1.96 TeV
2011
We present measurements of production cross sections of single top quarks in $\ppbar$ collisions at $\sqrt{s}=1.96\;\rm TeV$ in a data sample corresponding to an integrated luminosity of $5.4\;\rm fb^{-1}$ collected by the D0 detector at the Fermilab Tevatron Collider. We select events with an isolated electron or muon, an imbalance in transverse energy, and two, three, or four jets, with one or two of them containing a bottom hadron. We obtain an inclusive cross section of $\sigma({\ppbar}{\rargap}tb+X, tqb+X) = 3.43\pm^{0.73}_{0.74}\;\rm pb$ and use it to extract the CKM matrix element $0.79 < |V_{tb}| \leq 1$ at the 95% C.L. We also measure $\sigma({\ppbar}{\rargap}tb+X) = 0.68\pm^{0.38}…
Measurement of the top quark pair production cross section in thelepton+jetschannel in proton-antiproton collisions ats=1.96 TeV
2011
We present a measurement of the inclusive top quark pair production cross section in \ppbar collisions at (\sqrt{s}=1.96) TeV utilizing data corresponding to an integrated luminosity of \lumi\ collected with the D0 detector at the Fermilab Tevatron Collider. We consider final states containing one high-$p_{T}$ isolated electron or muon and at least two jets, and we perform three analyses: one exploiting specific kinematic features of \ttbar events, the second using $b$-jet identification, and the third using both techniques to separate \ttbar\ signal from background. In the third case, we determine simultaneously the $t\bar{t}$ cross section and the ratio of the production rates of $W$+heav…
Measurement of B(t→Wb)/B(t→Wq) at s=1.96TeV
2006
We present the measurement of R = B(t -> Wb)/B(t -> Wq) in pp collisions at root s = 1.96 TeV, using 230 pb(-1) of data collected by the DO experiment at the Fermilab Tevatron Collider. We fit simultaneously R and the number (N-tt) of selected top quark pairs (tt), to the number of identified b-quark jets in events with one electron or one muon, three or more jets, and high transverse energy imbalance. To improve sensitivity, kinematical properties of events with no identified b-quark jets are included in the fit. We measure R = 1.03(-0.17)(0.19) (stat + syst), in good agreement with the standard model. We set lower limits of R > 0.61 and vertical bar V-tb vertical bar > 0.78 at 95% confide…
Measurement of Leptonic Asymmetries and Top Quark Polarization in ttbar Production
2013
We present measurements of lepton (l) angular distributions in ttbar -> W+ b W- b -> l+ nu b l- nubar bbar decays produced in ppbar collisions at a center-of-mass energy of sqrt(s)=1.96TeV, where l is an electron or muon. Using data corresponding to an integrated luminosity of 5.4fb^-1, collected with the D0 detector at the Fermilab Collider, we find that the angular distributions of l- relative to anti-protons and l+ relative to protons are in agreement with each other. Combining the two distributions and correcting for detector acceptance we obtain the forward-backward asymmetry A^l_FB = (5.8 +- 5.1(stat) +- 1.3(syst))%, compared to the standard model prediction of A^l_FB (predicted…
Observation of a narrow mass state decaying intoΥ(1S)+γinpp¯collisions ats=1.96 TeV
2012
Using data corresponding to an integrated luminosity of 1.3 fb(-1), we observe a narrow mass state decaying into Gamma(1S) + gamma, where the Gamma(1S) meson is detected by its decay into a pair of oppositely charged muons, and the photon is identified through its conversion into an electron-positron pair. The significance of this observation is 5.6 standard deviations. The mass of the state is centered at 10.551 +/- 0.014(stat) +/- 0.017(syst) GeV/c(2), which is consistent with that of the state recently observed by the ATLAS Collaboration.
Testbeam studies of production modules of the ATLAS Tile Calorimeter
2009
We report test beam studies of {11\,\%} of the production ATLAS Tile Calorimeter modules. The modules were equipped with production front-end electronics and all the calibration systems planned for the final detector. The studies used muon, electron and hadron beams ranging in energy from 3~GeV to 350~GeV. Two independent studies showed that the light yield of the calorimeter was $\sim 70$~pe/GeV, exceeding the design goal by {40\,\%}. Electron beams provided a calibration of the modules at the electromagnetic energy scale. Over 200~calorimeter cells the variation of the response was {2.4\,\%}. The linearity with energy was also measured. Muon beams provided an intercalibration of the respo…
Measurements of the muon component of extensive air showers at 320m.w.e. underground
2003
Abstract The ALEPH detector at LEP has been supplemented with five scintillator telescopes to measure the muon component of cosmic ray air showers underground. The emphasis of the present analysis of a new data set is to measure coincidences over distances up to about 1 km which are sensitive to the forward production of hadronic interactions and the chemical composition of primary cosmic rays in the energy range around 1015 eV. First results indicate that the observed decoherence curve of muons is compatible with a light primary composition and the arrival directions of muons show no obvious clustering in galactic coordinates.
Exclusive ϱ0 and φ muoproduction at large Q2
1994
Abstract Exclusive ϱ 0 and φ muoproduction on deuterium, carbon and calcium has been studied in the kinematic range 2 Q 2 2 and 40 Q 2 dependence of the cross sections, the transverse momentum distributions for the vector mesons, the decay angular distributions and, in the case of the ϱ 0 , nuclear effects. The data for 0 production are compatible with a diffractive mechanism. The distinct features of φ production are a smaller cross section and less steep p t 2 distributions than those for the 0 mesons.
Search for heavy neutrinos in K + → μ + ν μ decays
2017
The NA62 experiment recorded a large sample of K+→μ+νμ decays in 2007. A peak search has been performed in the reconstructed missing mass spectrum. In the absence of a signal, limits in the range 2×10−6 to 10−5 have been set on the squared mixing matrix element |Uμ4|2 between muon and heavy neutrino states, for heavy neutrino masses in the range 300–375 MeV/ c2 . The result extends the range of masses for which upper limits have been set on the value of |Uμ4|2 in previous production search experiments.
Results of prototype studies for a spaghetti calorimeter
1990
In the framework of the LAA project, prototypes for a new type of calorimeter, intended for the detection of both electromagnetic (e.m.) and hadronic showers, muons and missing energy (e.g. neutrinos) at high-luminosity multi-TeV pp colliders, were tested. The detector consists of scintillating plastic fibres embedded in a lead matrix at a volume ratio 1:4, such as to achieve compensation. The optimization of the construction of the detector modules is described, as well as the performance concerning e.m. shower and muon detection and e/π separation. We used electron, pion and muon beams in the energy range 10–150 GeV for this purpose. For the energy resolution of electrons we found 13%/trE…