Search

Describes readout electronics designed for the DO Muon Upgrade. Number of detector systems served by the electronics; Functions performed by the processes of the electronics; Discussion of the design and results of the subsystem readout electronics and system interface.

Abstract: The MINERvA 6 [6] Main INjector ExpeRiment ν-A. experiment is designed to perform precision studies of neutrino-nucleus scattering using and neutrinos incident at 1–20GeV in the NuMI beam at Fermilab. This article presents a detailed description of the MINERvA detector and describes the ex situ and in situ techniques employed to characterize the detector and monitor its performance. The detector is composed of a finely segmented scintillator-based inner tracking region surrounded by electromagnetic and hadronic sampling calorimetry. The upstream portion of the detector includes planes of graphite, iron and lead interleaved between tracking planes to facilitate the study of nuclear effects in neutrino interactions. Observations concerning the detector response over sustained periods of running are reported. The detector design and methods of operation have relevance to future neutrino experiments in which segmented scintillator tracking is utilized. [Copyright &y& Elsevier]

Abstract: (Main INjector ExpeRiment ) is a new few-GeV neutrino cross-section experiment that began taking data in the FNAL NuMI (Fermi National Accelerator Laboratory Neutrinos at the Main Injector) beam-line in March of 2010. employs a fine-grained scintillator detector capable of complete kinematic characterization of neutrino interactions. This paper describes the data acquisition system (DAQ) including the readout electronics, software, and computing architecture. [Copyright &y& Elsevier]

The article presents the study of the inclusive production of the X(4140) state with the decay in hadronic collisions. The article mentions that the collision data collected from DO experiment consisting of a central tracking system, calorimeters, and muon detectors at the Fermilab Tevatron collider which reveals the prompt production of an X(4140) state. It reports the fraction of X(4140) events originating from b hadrons.

We present the first search for CPT-violating effects in the mixing of B0s mesons using the full Run II data set with an integrated luminosity of 10.4 fb-1 of proton-antiproton collisions collected using the D0 detector at the Fermilab Tevatron Collider. We measure the CPT-violating asymmetry in the decay B0s →μ±D±s as a function of celestial direction and sidereal phase. We find no evidence for CPT-violating effects and place limits on the direction and magnitude of flavor-dependent CPT- and Lorentz-invariance violating coupling coefficients. We find 95% confidence intervals of Δa⊥ < 1.2× 10-12 GeV and (-0.8 < ΔaT - 0.396ΔaZ < 3.9) × 10-13 GeV. [ABSTRACT FROM AUTHOR]

We present a measurement of the fundamental parameter of the standard model, the weak mixing angle sin2θleff which determines the relative strength of weak and electromagnetic interactions, in pp¯→Z/γ*→e+e- events at a center of mass energy of 1.96 TeV, using data corresponding to 9.7 fb-1 of integrated luminosity collected by the D0 detector at the Fermilab Tevatron. The effective weak mixing angle is extracted from the forward-backward charge asymmetry as a function of the invariant mass around the Z boson pole. The measured value of sin2θleff=0.23147±0.00047 is the most precise measurement from light quark interactions to date, with a precision close to the best LEP and SLD results. [ABSTRACT FROM AUTHOR]

We report the first results of DarkSide-50, a direct search for dark matter operating in the underground Laboratori Nazionali del Gran Sasso (LNGS) and searching for the rare nuclear recoils possibly induced by weakly interacting massive particles (WIMPs). The dark matter detector is a Liquid Argon Time Projection Chamber with a ( 46.4 ± 0.7 ) kg active mass, operated inside a 30 t organic liquid scintillator neutron veto, which is in turn installed at the center of a 1 kt water Cherenkov veto for the residual flux of cosmic rays. We report here the null results of a dark matter search for a ( 1422 ± 67 ) kg d exposure with an atmospheric argon fill. This is the most sensitive dark matter search performed with an argon target, corresponding to a 90% CL upper limit on the WIMP-nucleon spin-independent cross section of 6.1 × 10 − 44 cm 2 for a WIMP mass of 100 Gev / c 2 . [ABSTRACT FROM AUTHOR]

We present an updated measurement of the Bos lifetime using the semileptonic decays Bos → D-sμ+vX , with D-s → ϕπ- and ϕ → K+K- (and the charge conjugate process). This measurement uses the full Tevatron Run 13 sample of proton-antiproton collisions at √s = 1.96 TeV, comprising an integrated luminosity of 10.4 fb-1. We find a flavor-specific lifetime τfs(Bos) = 1.479 ± 0.010(stat) ± 0.021 (syst) ps. This technique is also used to determine the Bo lifetime using the analogous Bo → D-sμ+vX decay with D- → ϕπ- and ϕ → K+K-, yielding τ(Bo) = 1.534 ± 0.019(stat) ± 0.021 (syst) ps. Both measurements are consistent with the current world averages, and the Bos lifetime measurement is one of the most precise to date. Taking advantage of the cancellation of systematic uncertainties, we determine the lifetime ratio τfs(Bos)/τ(Bo) = 0.964 ± 0.013(stat) ± 0.007(syst). [ABSTRACT FROM AUTHOR]

Although the existence of dark matter is supported by many evidences, based on astrophysical measurements, its nature is still completely unknown. One major candidate is represented by weakly interacting massive particles (WIMPs), which could in principle be detected through their collisions with ordinary nuclei in a sensitive target, producing observable low-energy (<100 keV) nuclear recoils. The DarkSide program aims at the WIPMs detection using a liquid argon time projection chamber (LAr-TPC). In this paper we quickly review the DarkSide program focusing in particular on the next generation experiment DarkSide-G2, a 3.6-ton LAr-TPC. The different detector components are described as well as the improvements needed to scale the detector from DarkSide-50 (50 kg LAr-TPC) up to DarkSide-G2. Finally, the preliminary results on background suppression and expected sensitivity are presented. [ABSTRACT FROM AUTHOR]

The ability to identify jets which originated from b quarks is an important tool of the physics program of the D0 experiment at the Fermilab Tevatron p p ¯ collider. This paper describes a new algorithm designed to select jets originating from b quarks while suppressing the contamination caused by jets from other quark flavors and gluons. Additionally, a new technique, the System N method, for determining the misidentification rate directly from data is presented. [ABSTRACT FROM AUTHOR]

The calibration of jet energy measured in the D0 detector is presented, based on p p ¯ collisions at a center-of-mass energy of 1.96 TeV at the Fermilab Tevatron collider. Jet energies are measured using a sampling calorimeter composed of uranium and liquid argon as the passive and active media, respectively. This paper describes the energy calibration of jets performed with γ + jet , Z + jet and dijet events, with jet transverse momentum p T > 6 GeV and pseudorapidity range | η | < 3.6 . The corrections are measured separately for data and simulation, achieving a precision of 1.4–1.8% for jets in the central part of the calorimeter and up to 3.5% for the jets with pseudorapidity | η | = 3.0 . Specific corrections are extracted to enhance the description of jet energy in simulation and in particular of the effects due to the flavor of the parton originating the jet, correcting biases up to 3–4% in jets with low p T originating from gluons and up to 6–8% in jets from b quarks. [ABSTRACT FROM AUTHOR]

We present constraints on models containing non-standard-model values for the spin J and parity P of the Higgs boson H in up to 9.7 fb-1 of p... collisions at √s = 1.96 TeV collected with the DO detector at the Fermilab Tevatron Collider. These are the first studies of Higgs boson JP with fermions in the final state. In the ZH → llb..., WH → lvb..., and ZH → llb... final states, we compare the standard model (SM) Higgs boson prediction, JP = 0+, with two alternative hypotheses, JP = 0- and JP = 2+. We use a likelihood ratio to quantify the degree to which our data are incompatible with non-SM JP predictions for a range of possible production rates. Assuming that the production rate in the signal models considered is equal to the SM prediction, we reject the JP = 0- and JP = 2+ hypotheses at the 97.6% CL and at the 99.0% CL, respectively. The expected exclusion sensitivity for a JP = 0- (JP = 2+) state is at the 99.86% (99.94%) CL. Under the hypothesis that our data are the result of a combination of the SM-like Higgs boson and either a JP = 0- or a JP- 2+ signal, we exclude a JP= 0- fraction above 0.80 and a JP= 2+ fraction above 0.67 at the 95% CL. The expected exclusion covers JP = 0- (JP = 2+) fractions above 0.54 (0.47). [ABSTRACT FROM AUTHOR]

We measure the mass of the top quark in lepton + jets final states using the full sample of pp collision data collected by the DO experiment in Run II of the Fermilab Tevatron Collider at √s = 1.96 TeV, corresponding to 9.7 fb-1 of integrated luminosity. We use a matrix element technique that calculates the probabilities for each event to result from ft production or background. The overall jet energy scale is constrained in situ by the mass of the W boson. We measure m, = 174.98 ± 0.76 GeV. This constitutes the most precise single measurement of the top-quark mass. [ABSTRACT FROM AUTHOR]

Abstract: The electron and photon reconstruction and identification algorithms used by the D0 Collaboration at the Fermilab Tevatron collider are described. The determination of the electron energy scale and resolution is presented. Studies of the performance of the electron and photon reconstruction and identification are summarized. The results are based on measurements of Z boson decay events of and collected in collisions at a center-of-mass energy of 1.96TeV using an integrated luminosity of up to 10fb−1. [Copyright &y& Elsevier]

We present a measurement of the W boson production charge asymmetry in p → W + X → + ev + X events at a center of mass energy of 1.96 TeV, using 9.7-1 of integrated luminosity collected with the D0 detector at the Fermilab Tevatron Collider. The neutrino longitudinal momentum is determined by using a neutrino weighting method, and the asymmetry is measured as a function of the W boson rapidity. The measurement extends over wider electron pseudorapidity region than previous results and is the most precise to date, allowing for precise determination of proton parton distribution functions in global fits. [ABSTRACT FROM AUTHOR]

We present a measurement of the direct CP-violating charge asymmetry in Ds±→ϕπ± decays where the ϕ meson decays to K+K-, using the full Run II data set with an integrated luminosity of 10.4 fb-1 of proton-antiproton collisions collected using the D0 detector at the Fermilab Tevatron Collider. The normalized difference ACP in the yield of Ds+ and Ds- mesons in these decays is measured by fitting the difference between their reconstructed invariant mass distributions. This results in an asymmetry of ACP = [-0.38 ± 0.27]%, which is the most precise measurement of this quantity to date. The result is consistent with the standard model prediction of zero CP asymmetry in this decay. [ABSTRACT FROM AUTHOR]

Abstract: We present an overview of the muon reconstruction and identification methods employed by the D0 collaboration to analyze the Run II (2001–2011) data of the Fermilab Tevatron collider at . We discuss the performance of these methods, how it is measured using D0 data, and how it is properly modeled by the D0 simulation program. In its pseudorapidity acceptance, , the muon system identifies high-p T muons ( ) with efficiencies ranging from 72% to 89%. Muons tracks are reconstructed in the D0 central tracking system with efficiencies ranging from 85% to 92% and with a typical relative momentum resolution of 10% for . Isolation criteria reject multijet background with efficiencies of 87–99%. [Copyright &y& Elsevier]

We present the first measurements of the ratios of cross sections σ(p̄p→Z+c jet)/σ(p̄p→Z+jet) and σ(p̄p→Z+c jet)/σ(p̄p→Z+b jet) for the associated production of a Z boson with at least one charm or bottom quark jet. Jets have transverse momentum pTjet > 20 GeV and pseudorapidity ∣ηjet∣<2.5. These cross section ratios are measured differentially as a function of jet and Z boson transverse momenta, based on 9.7 fb-1 of p̄p collisions collected with the D0 detector at the Fermilab Tevatron Collider at √s=1.96 TeV. The measurements show significant deviations from perturbative QCD calculations and predictions from various event generators. [ABSTRACT FROM AUTHOR]

Abstract: We present measurements of the cross sections for the two main production modes of single top quarks in collisions at in the Run II data collected with the D0 detector at the Fermilab Tevatron Collider, corresponding to an integrated luminosity of 9.7 fb−1. The s-channel cross section is measured to be with no assumptions on the value of the t-channel cross section. Similarly, the t-channel cross section is measured to be . We also measure the combined cross section as and set a lower limit on the CKM matrix element at C.L., assuming . The probability to measure a cross section for the s channel at the observed value or higher in the absence of signal is , corresponding to a significance of 3.7 standard deviations. [Copyright &y& Elsevier]

Abstract: We present measurements of direct photon pair production cross sections using of data collected with the D0 detector at the Fermilab Tevatron collider. The results are presented as differential distributions of the photon pair invariant mass , pair transverse momentum , azimuthal angle between the photons , and polar scattering angle in the Collins–Soper frame . Measurements are performed for isolated photons with transverse momenta for the leading (next-to-leading) photon in , pseudorapidities , and a separation in η–ϕ space . We present comparisons with the predictions from Monte Carlo event generators diphox and resbos implementing QCD calculations at next-to-leading order, 2γ nnlo at next-to-next-to-leading order, and sherpa using matrix elements with higher-order real emissions matched to parton shower. [Copyright &y& Elsevier]

We have isolated ν̅ μ charged-current quasielastic (QE) interactions occurring in the segmented scintillator tracking region of the MINERvA detector running in the NuMI neutrino beam at Fermilab. We measure the flux-averaged differential cross section, dσ/dQ2, and compare to several theoretical models of QE scattering. Good agreement is obtained with a model where the nucleon axial mass, MA, is set to 0.99  GeV/c2 but the nucleon vector form factors are modified to account for the observed enhancement, relative to the free nucleon case, of the cross section for the exchange of transversely polarized photons in electron-nucleus scattering. Our data at higher Q2 favor this interpretation over an alternative in which the axial mass is increased. [ABSTRACT FROM AUTHOR]

We report a study of νμ charged-current quasielastic events in the segmented scintillator inner tracker of the MINERvA experiment running in the NuMI neutrino beam at Fermilab. The events were selected by requiring a μ- and low calorimetric recoil energy separated from the interaction vertex. We measure the flux-averaged differential cross section, dσ/dQ2, and study the low energy particle content of the final state. Deviations are found between the measured dσ/dQ2 and the expectations of a model of independent nucleons in a relativistic Fermi gas. We also observe an excess of energy near the vertex consistent with multiple protons in the final state. [ABSTRACT FROM AUTHOR]

We present a measurement of the direct CP-violating charge asymmetry in B± mesons decaying to J/ψK± and J/ψπ± where J/ψ decays to μ+μ-, using the full run II data set of 10.4 fb-1 of proton-antiproton collisions collected using the D0 detector at the Fermilab Tevatron Collider. A difference in the yield of B- and B+ mesons in these decays is found by fitting to the difference between their reconstructed invariant mass distributions resulting in asymmetries of AJ/ψK = [0.59 ± 0.37]%, which is the most precise measurement to date, and AJ/ψπ = [-4.2 ± 4.5]%. Both measurements are consistent with standard model predictions. [ABSTRACT FROM AUTHOR]

Abstract: We present the first combined measurement of the rapidity and transverse momentum dependence of dijet azimuthal decorrelations, using the recently proposed quantity . The variable measures the fraction of the inclusive dijet events in which the azimuthal separation of the two jets with the highest transverse momenta is less than a specified value of the parameter . The quantity is measured in collisions at , as a function of the dijet rapidity interval, the total scalar transverse momentum, and . The measurement uses an event sample corresponding to an integrated luminosity of 0.7 fb−1 collected with the D0 detector at the Fermilab Tevatron Collider. The results are compared to predictions of a perturbative QCD calculation at next-to-leading order in the strong coupling with corrections for non-perturbative effects. The theory predictions describe the data well, except in the kinematic region of large dijet rapidity intervals and small . [Copyright &y& Elsevier]

We present a measurement of the time-integrated flavor-specific semileptonic charge asymmetry in the decays of Bs0 mesons that have undergone flavor mixing, asls, using Bs0 (‾Bs0 ) → Ds± μ±X decays, with Ds± → ∅ π± and ∅ → K+K-, using 10.4 fb-1 of proton-antiproton collisions collected by the D0 detector during Run II at the Fermilab Tevatron Collider. A fit to the difference between the time-integrated Ds- and Ds+ mass distributions of the Bs0 and ‾Bs0 candidates yields the flavor-specific asymmetry asls = [-1.12 ± 0.74 (stat) ± 0.17 (syst)]%, which is the most precise measurement and in agreement with the standard model prediction. [ABSTRACT FROM AUTHOR]

Abstract: We present a measurement of the average value of a new observable at hadron colliders that is sensitive to QCD dynamics and to the strong coupling constant, while being only weakly sensitive to parton distribution functions. The observable measures the angular correlations of jets and is defined as the number of neighboring jets above a given transverse momentum threshold which accompany a given jet within a given distance ΔR in the plane of rapidity and azimuthal angle. The ensemble average over all jets in an inclusive jet sample is measured and the results are presented as a function of transverse momentum of the inclusive jets, in different regions of ΔR and for different transverse momentum requirements for the neighboring jets. The measurement is based on a data set corresponding to an integrated luminosity of 0.7 fb−1 collected with the D0 detector at the Fermilab Tevatron Collider in collisions at . The results are well described by a perturbative QCD calculation in next-to-leading order in the strong coupling constant, corrected for non-perturbative effects. From these results, we extract the strong coupling and test the QCD predictions for its running over a range of momentum transfers of 50–400 GeV. [Copyright &y& Elsevier]

We present a search for the standard model Higgs boson in final states with a charged lepton (electron or muon), missing transverse energy, and two or three jets, at least one of which is identified as a b-quark jet. The search is primarily sensitive to WH → lvbb̅ production and uses data corresponding to 9.7 fb-1 of integrated luminosity collected with the D0 detector at the Fermilab Tevatron pp̅ Collider at √s = 1.96 TeV. We observe agreement between the data and the expected background. For a Higgs boson mass of 125 GeV, we set a 95% C.L. upper limit on the production of a standard model Higgs boson of 5.2 X σSM where σSM is the standard model Higgs boson production cross section, while the expected limit is 4.7 X σSM. [ABSTRACT FROM AUTHOR]

Abstract: We present a search for the standard model Higgs boson in 9.5 fb−1 of collisions at collected with the D0 detector at the Fermilab Tevatron Collider. The final state considered contains a pair of b jets and is characterized by an imbalance in transverse energy, as expected from production. The search is also sensitive to the channel when the charged lepton is not identified. The data are found to be in good agreement with the expected background. For a Higgs boson mass of 125 GeV, we set a limit at the 95% C.L. on the cross section , assuming standard model branching fractions, that is a factor of 4.3 times larger than the theoretical standard model value, while the expected factor is 3.9. The search is also used to measure a combined WZ and ZZ production cross section that is a factor of times the standard model prediction of 4.4 pb, with an observed significance of 2.0 standard deviations. [Copyright &y& Elsevier]

Abstract: 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 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 ττ, WW, ZZ and 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 22 (14) at a Higgs boson mass of 115 GeV and 6.8 (7.7) at 165 GeV. [Copyright &y& Elsevier]

Abstract: We present measurements of the differential cross section for the inclusive production of a photon in association with a b-quark jet for photons with rapidities and , as well as for photons with and , where is the photon transverse momentum. The b-quark jets are required to have and rapidity . The results are based on data corresponding to an integrated luminosity of 8.7 fb−1, recorded with the D0 detector at the Fermilab Tevatron Collider at . The measured cross sections are compared with next-to-leading order perturbative QCD calculations using different sets of parton distribution functions as well as to predictions based on the -factorization QCD approach, and those from the sherpa and pythia Monte Carlo event generators. [Copyright &y& Elsevier]

Abstract: We present measurements of the tWb coupling form factors using information from electroweak single top quark production and from the helicity of W bosons from top quark decays in events. We set upper limits on anomalous tWb coupling form factors using data collected with the D0 detector at the Tevatron collider corresponding to an integrated luminosity of . [Copyright &y& Elsevier]

Abstract: We present a search for the production of neutral Higgs bosons decaying into pairs in collisions at a center-of-mass energy of 1.96 TeV. The data, corresponding to an integrated luminosity of 5.4 fb−1, were collected by the D0 experiment at the Fermilab Tevatron Collider. We set upper limits at the 95% C.L. on the product of production cross section and branching ratio for a scalar resonance decaying into pairs, and we interpret these limits as limits on the production of Higgs bosons in the minimal supersymmetric standard model (MSSM) and as constraints in the MSSM parameter space. [Copyright &y& Elsevier]

Abstract: This Letter describes measurements of inclusive jet cross sections (), presented as total inclusive cross sections and differentially in the nth jet transverse momentum. The measurements are made using data corresponding to an integrated luminosity of 4.2 fb−1 collected by the D0 detector at the Fermilab Tevatron Collider, and achieve considerably smaller uncertainties on production cross sections than previous measurements. The measurements are compared to next-to-leading order perturbative QCD (pQCD) calculations in the jet multiplicity bins and to leading order pQCD calculations in the 4-jet bin. The measurements are generally in agreement with pQCD calculations, although certain regions of phase space are identified where these predictions could better match the data. [Copyright &y& Elsevier]

Abstract: We describe the design, construction, and performance of the upgraded DØmuon system for Run II of the Fermilab Tevatron collider. Significant improvements have been made to the major subsystems of the DØmuon detector: trigger scintillation counters, tracking detectors, and electronics. The Run II central muon detector has a new scintillation counter system inside the iron toroid and an improved scintillation counter system outside the iron toroid. In the forward region, new scintillation counter and tracking systems have been installed. Extensive shielding has been added in the forward region. A large fraction of the muon system electronics is also new. [Copyright &y& Elsevier]

Abstract: We examine properties of candidate events in lepton+jets final states to establish the helicities of W bosons in decays. Our analysis is based on a direct calculation of a probability density for each event to correspond to a final state, as a function of the helicity of the W boson. Using the 125 events/pb of data collected by the DØ experiment at the Fermilab Tevatron Collider at , we obtain a longitudinal helicity fraction , consistent with the prediction of from the standard model. [Copyright &y& Elsevier]

Abstract: We describe a measurement of the mass of the top quark from the purely hadronic decay modes of pairs using all-jet data produced in collisions at at the Fermilab Tevatron Collider. The data, which correspond to an integrated luminosity of , were collected with the DØ detector from 1992 to 1996. We find a top quark mass of . [Copyright &y& Elsevier]

The standard model of particle physics contains parameters-such as particle masses-whose origins are still unknown and which cannot be predicted, but whose values are constrained through their interactions. In particular, the masses of the top quark (Mt) and W boson (MW) constrain the mass of the long-hypothesized, but thus far not observed, Higgs boson. A precise measurement of Mt can therefore indicate where to look for the Higgs, and indeed whether the hypothesis of a standard model Higgs is consistent with experimental data. As top quarks are produced in pairs and decay in only about 10-24?s into various final states, reconstructing their masses from their decay products is very challenging. Here we report a technique that extracts more information from each top-quark event and yields a greatly improved precision (of ± 5.3?GeV/c2) when compared to previous measurements. When our new result is combined with our published measurement in a complementary decay mode and with the only other measurements available, the new world average for Mt becomes 178.0 ± 4.3?GeV/c2. As a result, the most likely Higgs mass increases from the experimentally excluded value of 96 to 117?GeV/c2, which is beyond current experimental sensitivity. The upper limit on the Higgs mass at the 95% confidence level is raised from 219 to 251?GeV/c2. [ABSTRACT FROM AUTHOR]