Search results for "Muon"
showing 10 items of 1376 documents
Search for the standard model Higgs boson in tau lepton final states
2012
We present a search for the standard model Higgs boson in final states with an electron or muon and a hadronically decaying tau lepton in association with zero, one, or two or more jets using data corresponding to an integrated luminosity of up to 7.3 fb^{-1} collected with the D0 detector at the Fermilab Tevatron collider. The analysis is sensitive to Higgs boson production via gluon gluon fusion, associated vector boson production, and vector boson fusion, and to Higgs boson decays to tau lepton pairs or W boson pairs. Observed (expected) limits are set on the ratio of 95% C.L. upper limits on the cross section times branching ratio, relative to those predicted by the Standard Model, of 1…
Measurement of the tt¯ production cross section in pp¯ collisions at s=1.96 TeV in dilepton final states
2005
We present a measurement of the top quark pair ($t\bar{t}$) production cross section ($\sigma_{t\bar{t}}$) in $p\bar{p}$ collisions at $\sqrt{s}=1.96$ TeV using 230 pb$^{-1}$ of data collected by the D0 experiment at the Fermilab Tevatron Collider. We select events with one charged lepton (electron or muon), missing transverse energy, and jets in the final state. We employ lifetime-based b-jet identification techniques to further enhance the $t\bar{t}$ purity of the selected sample. For a top quark mass of 175 GeV, we measure $\sigma_{t\bar{t}}=8.6^{+1.6}_{-1.5}(stat.+syst.)\pm 0.6(lumi.)$ pb, in agreement with the standard model expectation
Measurement of atmospheric neutrino oscillations with the ANTARES neutrino telescope
2012
The data taken with the ANTARES neutrino telescope from 2007 to 2010, a total live time of 863 days, are used to measure the oscillation parameters of atmospheric neutrinos. Muon tracks are reconstructed with energies as low as 20 GeV. Neutrino oscillations will cause a suppression of vertical upgoing muon neutrinos of such energies crossing the Earth. The parameters determining the oscillation of atmospheric neutrinos are extracted by fitting the event rate as a function of the ratio of the estimated neutrino energy and reconstructed flight path through the Earth. Measurement contours of the oscillation parameters in a two-flavour approximation are derived. Assuming maximal mixing, a mass …
Cosmology with a very light Lμ − Lτ gauge boson
2019
In this paper, we explore in detail the cosmological implications of an abelian L − L gauge extension of the Standard Model featuring a light and weakly coupled Z′. Such a scenario is motivated by the longstanding ∼ 4σ discrepancy between the measured and predicted values of the muon’s anomalous magnetic moment, (g − 2) , as well as the tension between late and early time determinations of the Hubble constant. If sufficiently light, the Z′ population will decay to neutrinos, increasing the overall energy density of radiation and altering the expansion history of the early universe. We identify two distinct regions of parameter space in this model in which the Hubble tension can be significa…
Search for lepton flavor violating decays τ±→l± ω
2008
A search for lepton flavor violating decays of a {tau} to a lighter-mass charged lepton and an {omega} vector meson is performed using 384.1 fb{sup -1} of e{sup +}e{sup -} annihilation data collected with the BABAR detector at the Stanford Linear Accelerator Center PEP-II storage ring. No signal is found, and the upper limits on the branching ratios are determined to be {beta}({tau}{sup {+-}} {yields} e{sup {+-}}{omega}) < 1.1 x 10{sup -7} and {beta}({tau}{sup {+-}} {yields} {mu}{sup {+-}}{omega}) < 1.0 x 10{sup -7} at 90% confidence level.
Measurement of the Spin Structure of the Deuteron in the DIS Region
2005
We present a new measurement of the longitudinal spin asymmetry A_1^d and the spin-dependent structure function g_1^d of the deuteron in the range 1 GeV^2 < Q^2 < 100 GeV^2 and 0.004< x <0.7. The data were obtained by the COMPASS experiment at CERN using a 160 GeV polarised muon beam and a large polarised 6-LiD target. The results are in agreement with those from previous experiments and improve considerably the statistical accuracy in the region 0.004 < x < 0.03.
Measurements of the T2K neutrino beam properties using the INGRID on-axis near detector
2012
Precise measurement of neutrino beam direction and intensity was achieved based on a new concept with modularized neutrino detectors. INGRID (Interactive Neutrino GRID) is an on-axis near detector for the T2K long baseline neutrino oscillation experiment. INGRID consists of 16 identical modules arranged in horizontal and vertical arrays around the beam center. The module has a sandwich structure of iron target plates and scintillator trackers. INGRID directly monitors the muon neutrino beam profile center and intensity using the number of observed neutrino events in each module. The neutrino beam direction is measured with accuracy better than 0.4 mrad from the measured profile center. The …
The MATHUSLA test stand
2020
The rate of muons from LHC $pp$ collisions reaching the surface above the ATLAS interaction point is measured and compared with expected rates from decays of $W$ and $Z$ bosons and $b$- and $c$-quark jets. In addition, data collected during periods without beams circulating in the LHC provide a measurement of the background from cosmic ray inelastic backscattering that is compared to simulation predictions. Data were recorded during 2018 in a 2.5 $\times$ 2.5 $\times$ 6.5~$\rm{m}^3$ active volume MATHUSLA test stand detector unit consisting of two scintillator planes, one at the top and one at the bottom, which defined the trigger, and six layers of RPCs between them, grouped into three $(x…
Construction of two large-size four-plane micromegas detectors
2015
We report on the construction and initial performance studies of two micromegas detector quadruplets with an area of 0.5 m$^2$. They serve as prototypes for the planned upgrade project of the ATLAS muon system. Their design is based on the resistive-strip technology and thus renders the detectors spark tolerant. Each quadruplet comprises four detection layers with 1024 readout strips and a strip pitch of 415 $\mu$m. In two out of the four layers the strips are inclined by $\pm$1.5$^{\circ}$ to allow for the measurement of a second coordinate. We present the detector concept and report on the experience gained during the detector construction. In addition an evaluation of the detector perfor…
Temperature effect on RPC performance in the ARGO-YBJ experiment
2009
The ARGO-YBJ experiment has been taking data for nearly 2 years. In order to monitor continuously the performance of the Resistive Plate Chamber detectors and to study the daily temperature effects on the detector performance, a cosmic ray muon telescope was setup near the carpet detector array in the ARGO-YBJ laboratory. Based on the measurements performed using this telescope, it is found that, at the actual operating voltage of 7.2kV, the temperature effect on the RPC time resolution is about 0.04ns/degrees C and on the particle detection efficiency is about 0.03%/degrees C. Based on these figures we conclude that the environmental effects do not affect substantially the angular resoluti…