3,151 research outputs found
Global Positioning System constraints on fault slip rates in the Death Valley region, California and Nevada
We estimated horizontal velocities at 15 locations in the vicinity of Yucca Mountain, Nevada, from Global Positioning System surveys conducted between 1991 and 1996. We used these velocity estimates to infer slip rates on two major Quaternary faults within the eastern California shear zone (ECSZ), the Hunter Mountain and Death Valley faults. The sum of slip rates across the two faults is well determined at 5 ± 1 mm/yr (1-Ï). Between 3 to 5 mm/yr of this motion appears to be accommodated along the Death Valley fault, implying 30â50 m of strain accumulation over the next 10,000 yr. If so, there is potential for 5 to 10 M_(w) 6.5â7.5 earthquakes during this period, a finding consistent with paleoseismological studies of the fault zone. Yucca Mountain, which lies 50 km east of the ECSZ, is the proposed location for the disposal of high-level nuclear waste in the United States
Measurement of the inclusive and dijet cross-sections of b-jets in pp collisions at sâ=7~TeV with the ATLAS detector
Search for minimal supergravity in single-electron events with jets and large missing transverse energy in pp-bar collisions at sâ=1.8TeV
This is the publisher's version, also available electronically from http://journals.aps.org/prd/abstract/10.1103/PhysRevD.66.112001.We describe a search for evidence of minimal supergravity (MSUGRA) in 92.7pb(-1) of data collected with the DĂ detector at the Fermilab Tevatron pp-bar collider at sâ=1.8TeV. Events with a single electron, four or more jets, and large missing transverse energy were used in this search. The major backgrounds are from W+jets, misidentified multijet, tt-bar, and WW production. We observe no excess above the expected number of background events in our data. A new limit in terms of MSUGRA model parameters is obtained
Near-threshold production of -mesons in and NN collisions and -mixing
We consider near-threshold -meson production in and
collisions. An effective Lagrangian approach with one-pion exchange is applied
to analyze different contributions to the cross section for different isospin
channels. The Reggeon exchange mechanism is also evaluated for comparison. The
results from reactions are used to calculate the contribution of the
meson to the cross sections and invariant mass distributions
of the reactions and . It is found that
the experimental observation of mesons in the reaction is much more promising than the observation of mesons in
the reaction . Effects of isospin violation in the reactions
, , and , which are induced by -- mixing, are also analyzed.Comment: 43 pages, including 16 eps figures, to be bublished in Phys. Atom.
Nucl. (Yad. Fiz.) vol. 65, No. 11 (2002
Search for dilepton signatures from minimal low-energy supergravity in pp-bar collisions at sâ=1.8 TeV
This is the publisher's version, also available electronically from http://journals.aps.org/prd/abstract/10.1103/PhysRevD.63.091102.We report on a search for supersymmetry using the DĂ detector. The 1994â1996 data sample of sâ=1.8 TeV pp-bar collisions was analyzed for events containing two leptons (e or ÎŒ), two or more jets, and missing transverse energy. Assuming the minimal supergravity model, with A(0)=0 and ÎŒ<0, various thresholds were employed to optimize the search. No events were found beyond expectation from the background. We set a lower limit at the 95% C.L. of 255 GeV/c(2) for equal mass squarks and gluinos for tanÎČ=2, and present exclusion contours in the (m(0),m(1/2)) plane for tanÎČ=2â6
Design and Implementation of the New D0 Level-1 Calorimeter Trigger
Increasing luminosity at the Fermilab Tevatron collider has led the D0
collaboration to make improvements to its detector beyond those already in
place for Run IIa, which began in March 2001. One of the cornerstones of this
Run IIb upgrade is a completely redesigned level-1 calorimeter trigger system.
The new system employs novel architecture and algorithms to retain high
efficiency for interesting events while substantially increasing rejection of
background. We describe the design and implementation of the new level-1
calorimeter trigger hardware and discuss its performance during Run IIb data
taking. In addition to strengthening the physics capabilities of D0, this
trigger system will provide valuable insight into the operation of analogous
devices to be used at LHC experiments.Comment: 43 pages, 20 figures, version published in Nucl. Instrum. and Methods
Differential cross section for w boson production as a function of transverse momentum in proton-antiproton collisions at â s = 1.8 TeV
Measurement of Semileptonic Branching Fractions of B Mesons to Narrow D** States
Using the data accumulated in 2002-2004 with the DO detector in
proton-antiproton collisions at the Fermilab Tevatron collider with
centre-of-mass energy 1.96 TeV, the branching fractions of the decays B ->
\bar{D}_1^0(2420) \mu^+ \nu_\mu X and B -> \bar{D}_2^{*0}(2460) \mu^+ \nu_\mu X
and their ratio have been measured: BR(\bar{b}->B) \cdot BR(B-> \bar{D}_1^0
\mu^+ \nu_\mu X) \cdot BR(\bar{D}_1^0 -> D*- pi+) =
(0.087+-0.007(stat)+-0.014(syst))%; BR(\bar{b}->B)\cdot BR(B->D_2^{*0} \mu^+
\nu_\mu X) \cdot BR(\bar{D}_2^{*0} -> D*- \pi^+) =
(0.035+-0.007(stat)+-0.008(syst))%; and (BR(B -> \bar{D}_2^{*0} \mu^+ \nu_\mu
X)BR(D2*0->D*- pi+)) / (BR(B -> \bar{D}_1^{0} \mu^+ \nu_\mu X)\cdot
BR(\bar{D}_1^{0}->D*- \pi^+)) = 0.39+-0.09(stat)+-0.12(syst), where the charge
conjugated states are always implied.Comment: submitted to Phys. Rev. Let
Study of ZÎł events and limits on anomalous ZZÎł and Zγγ couplings in ppÌ collisions at s=1.96TeV
We present a measurement of the ZÎł production cross section and limits on anomalous ZZÎł and Zγγ couplings for form-factor scales of Î=750 and 1000 GeV. The measurement is based on 138 (152) candidates in the eeÎł (ÎŒÎŒÎł) final state using 320(290)pb-1 of ppÌ collisions at s=1.96TeV. The 95% C.L. limits on real and imaginary parts of individual anomalous couplings are |h10,30Z|<0.23, |h20,40Z|<0.020, |h10,30Îł|<0.23, and |h20,40Îł|<0.019 for Î=1000GeV. © 2005 The American Physical Society
Measurement of the Lifetime Difference in the B_s^0 System
We present a study of the decay B_s^0 -> J/psi phi We obtain the CP-odd
fraction in the final state at time zero, R_perp = 0.16 +/- 0.10 (stat) +/-
0.02 (syst), the average lifetime of the (B_s, B_sbar) system, tau (B_s^0)
=1.39^{+0.13}_{-0.16} (stat) ^{+0.01}_{-0.02} (syst) ps, and the relative width
difference between the heavy and light mass eigenstates, Delta Gamma/Gamma =
(Gamma_L - Gamma_H)/Gamma =0.24^{+0.28}_{-0.38} (stat) ^{+0.03}_{-0.04} (syst).
With the additional constraint from the world average of the B_s^0$lifetime
measurements using semileptonic decays, we find tau (B_s^0)= 1.39 +/- 0.06 ~ps
and Delta Gamma/\Gamma = 0.25^{+0.14}_{-0.15}. For the ratio of the B_s^0 and
B^0 lifetimes we obtain tau(B_s^0)/tau(B^0)} = 0.91 +/- 0.09 (stat) +/- 0.003
(syst).Comment: submitted to Phys. Rev. Lett. FERMILAB-PUB-05-324-
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