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-σ). Between 3 to 5 mm/yr of this motion appears to be accommodated along the Death Valley fault, implying 30–50 m of strain accumulation over the next 10,000 yr. If so, there is potential for 5 to 10 M_(w) 6.5–7.5 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

Search for minimal supergravity in single-electron events with jets and large missing transverse energy in pp-bar collisions at s√=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 DØ detector at the Fermilab Tevatron pp-bar collider at s√=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 a0(980)a_0(980)-mesons in πN\pi N and NN collisions and a0/f0a_0/f_0-mixing

We consider near-threshold $a_0(980)$-meson production in $\pi N$ and $NN$ 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 $\pi N$ reactions are used to calculate the contribution of the $a_0$ meson to the cross sections and invariant $K \bar K$ mass distributions of the reactions $pp\to pn K^+\bar K^0$ and $pp\to pp K^+K^-$. It is found that the experimental observation of $a_0^+$ mesons in the reaction $pp\to pn K^+\bar K^0$ is much more promising than the observation of $a_0^0$ mesons in the reaction $pp\to pp K^+K^-$. Effects of isospin violation in the reactions $pN \to d a_0$, $pd \to \mathrm{^3He/^3H} a_0$, and $dd \to \mathrm{^4He} a_0$, which are induced by $a_0(980)$--$f_0(980)$ 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 s√=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 DØ detector. The 1994–1996 data sample of s√=1.8 TeV pp-bar collisions was analyzed for events containing two leptons (e or μ), two or more jets, and missing transverse energy. Assuming the minimal supergravity model, with A(0)=0 and μ<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 tanβ=2, and present exclusion contours in the (m(0),m(1/2)) plane for tanβ=2–6

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

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 Zγ events and limits on anomalous ZZγ and Zγγ couplings in pp̄ collisions at s=1.96TeV

We present a measurement of the Zγ production cross section and limits on anomalous ZZγ and Zγγ couplings for form-factor scales of Λ=750 and 1000 GeV. The measurement is based on 138 (152) candidates in the eeγ (μμγ) final state using 320(290)pb-1 of pp̄ 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, |h10,30γ|<0.23, and |h20,40γ|<0.019 for Λ=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-