arXiv subjects

D0 Collaboration

Publications and source records attributed to D0 Collaboration.

At least 91 records · Page 5Linked to original sources

arXiv2013

Search for a Higgs boson in diphoton final states with the D0 detector in 9.6 fb-1 of p-pbar collisions at sqrt(s)=1.96 TeV

We present a search for a Higgs boson decaying into a pair of photons based on 9.6 fb-1 of p-pbar collisions at sqrt(s)=1.96 TeV collected with the D0 detector at the Fermilab Tevatron Collider. The search employs multivariate techniques to discriminate signal from the non-resonant background and is separately optimized for a standard model and a fermiophobic Higgs boson. No significant excess of data above the background prediction is observed and upper limits on the product of the cross section and branching fraction are derived at the 95% confidence level as a function of Higgs boson mass. For a standard model Higgs boson with mass of 125 GeV, the observed (expected) upper limits are a factor of 12.8 (8.7) above the standard model prediction. The existence of a fermiophobic Higgs boson with mass in the 100-113 GeV range is excluded at the 95% confidence level.

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arXiv2013

Search for the rare decay Bs->mumu

We perform a search for the rare decay Bs->mumu using data collected by the D0 experiment at the Fermilab Tevatron Collider. This result is based on the full D0 Run II dataset corresponding to 10.4 fb^(-1) of ppbar collisions at sqrt(s) = 1.96 TeV. We use a multivariate analysis to increase the sensitivity of the search. In the absence of an observed number of events above the expected background, we set an upper limit on the decay branching fraction of BR(Bs->mumu) < 15x10^(-9) at the 95% C.L.

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arXiv2013

Measurement of the semileptonic charge asymmetry using Bs^0 -> D_s mu X decays

We present a measurement of the time-integrated flavor-specific semileptonic charge asymmetry in the decays of Bs mesons that have undergone flavor mixing, a^s_ls, using B_s^0 (barB_s^0) -> D_s^-/+ mu^+/- X decays, with D_s^-/+ -> phi pi^-/+ and phi 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 D_s^-$ and D_s^+ mass distributions of the B_s^0 and barB^0_s candidates yields the flavor-specific asymmetry a^s_ls = [-1.12 pm 0.74 (stat) +/-0.17 (syst)]% which is the most precise measurement and in agreement with the standard model prediction.

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arXiv2013

Search for Higgs boson production in oppositely charged dilepton and missing energy final states in 9.7 fb-1 of ppbar collisions at sqrts = 1.96 TeV

We present a search for Higgs boson in final states with two oppositely charged leptons and large missing transverse energy as expected in H -> WW -> lvlv decays. The events are selected from the full Run II data sample of 9.7 fb-1 of ppbar collisions collected with the D0 detector at the Fermilab Tevatron Collider at sqrt s = 1.96 TeV. To validate our search methodology, we measure the non-resonant W W production cross section and find sigma_WW = 11.6 +/- 0.7 pb, in agreement with the standard model prediction. In the Higgs boson search, no significant excess above the background expectation is observed. Upper limits at the 95% confidence level on the Higgs boson production cross section are therefore derived. Within the standard model, the Higgs boson mass range 159 < MH < 176 GeV is excluded while the expected exclusion sensitivity is 156 < MH < 172 GeV. For a mass hypothesis of MH = 125 GeV, we exclude Higgs boson production cross sections 4.1 times larger than the standard model expectation, which is compatible with the presence of a Higgs boson at this mass. Within a theoretical framework with a fourth generation of fermions, the mass range 125 < MH < 218 GeV is excluded. The search results are also interpreted in the context of fermiophobic Higgs boson couplings, which yields an exclusion of fermiophobic Higgs boson production cross sections 3.1 times larger than the expectation for MH = 125 GeV.

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arXiv2012

Measurement of the differential photon+ c-jet cross section and the ratio of differential photon+ c and photon+ b cross sections in proton-antiproton collisions at sqrt(s) = 1.96 TeV

We present measurements of the differential cross section $dσ/dp_{T}^γ$ for the associated production of a $c$-quark jet and an isolated photon with rapidity $|y^γ|< 1.0$ and transverse momentum $30 < p_{T}^γ < 300$ GeV. The $c$-quark jets are required to have $|y^{jet}| < 1.5$ and $p_{T}^{jet} >15$ GeV. The ratio of differential cross sections for photon+ c and photon+ b production as a function of $p_{T}^γ$ is also presented. 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 $p\bar{p}$ Collider at $\sqrt{s}=$1.96 TeV. The obtained results are compared to next-to-leading order perturbative QCD calculations using various parton distribution functions, to predictions based on the $k_{T}$-factorization approach, and to predictions from the Sherpa and Pythia Monte Carlo event generators.

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arXiv2012

Measurement of the photon$+b$-jet production differential cross section in $p\bar{p}$ collisions at $\sqrt{s}=1.96~\TeV$

We present measurements of the differential cross section dsigma/dpT_gamma for the inclusive production of a photon in association with a b-quark jet for photons with rapidities |y_gamma|< 1.0 and 30 15 GeV and rapidity |y_jet| < 1.5. 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 $p\bar{p}$ Collider at sqrt(s)=1.96 TeV. 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 kT-factorization QCD approach, and those from the Sherpa and Pythia Monte Carlo event generators.

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arXiv2012

Study of the decay $B_s^0 \rightarrow J/ψf_2^{\prime}(1525)$ in $μ^+ μ^- K^+K^-$ final states

We investigate the decay $B_s^0 \rightarrow J/ψK^+ K^-$ for invariant masses of the $K^+K^-$ pair in the range $1.35<M(K^+K^-)<2$ GeV. The data sample corresponds to an integrated luminosity of 10.4 fb$^{-1}$ of $p \bar{p}$ collisions at $\sqrt{s} = 1.96$ TeV accumulated with the D0 detector at the Fermilab Tevatron collider. From the study of the invariant mass and spin of the $K^+K^-$ system, we find evidence for the two-body decay \bsf and measure the relative branching fraction of the decays \bsf and \bsdec to be $R_{f_2^{\prime}/ϕ} = 0.19 \pm 0.05 \rm \thinspace{(stat)} \pm 0.04 \rm \thinspace{(syst)}$.

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arXiv2012

Measurement of the combined rapidity and $p_T$ dependence of dijet azimuthal decorrelations in $p\bar{p}$ collisions at $\sqrt{s}=1.96\,$TeV

We present the first combined measurement of the rapidity and transverse momentum dependence of dijet azimuthal decorrelations, based on the recently proposed quantity $R_{Δϕ}$. The variable $R_{Δϕ}$ 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 for the parameter $Δϕ_{\rm max}$. The quantity $R_{Δϕ}$ is measured in $p\bar{p}$ collisions at $\sqrt{s}=1.96\,$TeV, as a function of the dijet rapidity interval, the total scalar transverse momentum, and $Δϕ_{\rm max}$. 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, except in the kinematic region of large dijet rapidity intervals and large $Δϕ_{\rm max}$.

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arXiv2012

Measurement of angular correlations of jets at sqrt(s)=1.96 TeV and determination of the strong coupling at high momentum transfers

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 Delta-R 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 Delta-R 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 pp-bar collisions at sqrt(s)=1.96 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.

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arXiv2012

Measurement of the semileptonic charge asymmetry in B0 meson mixing with the D0 detector

We present a measurement of the semileptonic mixing asymmetry for B0 mesons, a^d_{sl}, using two independent decay channels: B0 -> mu+D-X, with D- -> K+pi-pi-; and B0 -> mu+D*-X, with D*- -> antiD0 pi-, antiD0 -> K+pi- (and charge conjugate processes). We use a data sample corresponding to 10.4 fb^{-1} of ppbar collisions at sqrt(s) = 1.96 TeV, collected with the D0 experiment at the Fermilab Tevatron collider. We extract the charge asymmetries in these two channels as a function of the visible proper decay length (VPDL) of the B0 meson, correct for detector-related asymmetries using data-driven methods, and account for dilution from charge-symmetric processes using Monte Carlo simulation. The final measurement combines four signal VPDL regions for each channel, yielding a^d_{sl} = [0.68 \pm 0.45 \text{(stat.)} \pm 0.14 \text{(syst.)}]%. This is the single most precise measurement of this parameter, with uncertainties smaller than the current world average of B factory measurements.

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arXiv2012

Search for charged massive long-lived particles at sqrt(s)= 1.96 TeV

We present a search for charged massive long-lived particles (CMLLPs) that are pair produced in p-pbar collisions at sqrt(s)= 1.96 TeV collected by the D0 experiment at the Fermilab Tevatron collider. Our result is a combination of two searches where either one or both CMLLPs are reconstructed in the detector. We select events with muon-like particles that have both speed and ionization energy loss dE/dx different from muons produced in p-pbar collisions. In the absence of evidence for CMLLPs corresponding to 6.3 fb-1 of integrated luminosity, we set limits on the CMLLP masses in several supersymmetric models, excluding masses below 278 GeV for long-lived gaugino-like charginos, and masses below 244 GeV for long-lived higgsino-like charginos at the 95% C.L. We also set limits on the cross section for pair production of long-lived scalar tau leptons that range from 0.04 pb to 0.008 pb for scalar tau lepton masses of 100 to 300 GeV.

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arXiv2012

Measurement of the ppbar -> W+b+X production cross section at \sqrt{s}=1.96 TeV

We present a measurement of the cross section for $W$ boson production in association with at least one {$b$-quark} jet in proton-antiproton collisions. The measurement is made using data corresponding to an integrated luminosity of 6.1\ifb recorded with the D0 detector at the Fermilab Tevatron \ppbar Collider at $\sqrt{s}=1.96$ TeV. We measure an inclusive cross section of {$σ(W \sim(\toμν) + b + X) = 1.04 \pm 0.05\thinspace$(stat.) $\pm 0.12 \thinspace$(syst.) pb} and $σ(W (\to eν) + b + X) = 1.00$ \pm 0.04 \thinspace$(stat.) $\pm 0.12 \thinspace$(syst.) pb in the phase space defined by $p_T^ν> 25$ GeV, $p_T^{\text{$b$-jet}}>20$ GeV, $|η^{\text{$b$-jet}}|<1.1$, and a muon (electron) with $p_T^\ell>20$ GeV and $|η^μ|<1.7$ ($|η^e|<1.1$ or $1.5<|η^e|<2.5$). The combined result per lepton family is $σ(W (\to \ell ν) + b + X) = 1.05$ $\pm 0.12 \thinspace$(stat.+syst.) for $|η^\ell|<1.7$. The results are in agreement with predictions from next-to-leading order QCD calculations using \textsc{mcfm}, $σ(W+b)\cdot {\cal B}(W \to \ell ν)= 1.34 ^{+0.41}_{-0.34}\thinspace(\textrm{syst.})$, and also with predictions from the \textsc{sherpa} and \textsc{madgraph} Monte Carlo event generators.

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arXiv2012

Search for $WH$ associated production in $p \bar{p}$ collisions at $\sqrt{s}=1.96\,{\rm TeV}$

This report describes a search for associated production of $W$ and Higgs bosons based on data corresponding to an integrated luminosity of $\cal{L}$$ \approx 5.3 \rm fb^{-1}$ collected with the D0 detector at the Fermilab Tevatron $p\bar{p}$ Collider. Events containing a $W\rightarrow \ell ν$ candidate (with $\ell$ corresponding to $e$ or $μ$) are selected in association with two or three reconstructed jets. One or two of the jets are required to be consistent with having evolved from a $b$ quark. A multivariate discriminant technique is used to improve the separation of signal and backgrounds. Expected and observed upper limits are obtained for the product of the $WH$ production cross section and branching ratios and reported in terms of ratios relative to the prediction of the standard model as a function of the mass of the Higgs boson ($M_{H}$). The observed and expected 95% C.L. upper limits obtained for an assumed $M_{H}=115 \rm GeV$ are, respectively, factors of 4.5 and 4.8 larger than the value predicted by the standard model.

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arXiv2012

Measurement of the top quark mass in $\boldsymbol{\ppbar}$ collisions using events with two leptons

We present a measurement of the top quark mass ($m_t$) in $p\bar{p}$ collisions at $\sqrt{s} = 1.96$ TeV using $t\bar{t}$ events with two leptons ($ee$, $eμ$, or $μμ$) and accompanying jets in $4.3 fb^{-1}$ of data collected with the D0 detector at the Fermilab Tevatron collider. We analyze the kinematically underconstrained dilepton events by integrating over their neutrino rapidity distributions. We reduce the dominant systematic uncertainties from the calibration of jet energy using a correction obtained from $t\bar{t}$ events with a final state of a single lepton plus jets. We also correct jets in simulated events to replicate the quark flavor dependence of the jet response in data. We measure $m_t = 173.7 \pm 2.8\thinspace(\rm stat) \pm 1.5\thinspace(\rm syst)$ GeV and combining with our analysis in 1 fb$^{-1}$ of preceding data we measure $m_t = 174.0 \pm 2.4\thinspace(\rm stat) \pm 1.4\thinspace(\rm syst)$ GeV. Taking into account statistical and systematic correlations, a combination with the D0 matrix element result from both data sets yields $m_t = 173.9 \pm 1.9\thinspace(\rm stat) \pm 1.6\thinspace(\rm syst)$ GeV.

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arXiv2012

Combined search for the standard model Higgs boson decaying to b bbar using the D0 Run II data set

We present the results of the combination of searches for the standard model Higgs boson produced in association with a W or Z boson and decaying into b bbar using the data sample collected with the D0 detector in p pbar collisions at sqrt{s}=1.96 TeV at the Fermilab Tevatron Collider. We derive 95% CL upper limits on the Higgs boson cross section relative to the standard model prediction in the mass range 100 GeV <= M_H <= 150 GeV, and we exclude Higgs bosons with masses smaller than 102 GeV at the 95% CL. In the mass range 120 GeV <= M_H <= 145 GeV the data exhibit an excess above the background prediction with a global significance of 1.5 standard deviations, consistent with the expectation in the presence of a standard model Higgs boson.

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arXiv2012

Search for the standard model Higgs boson in ZH -> l+ l- bbbar production with the D0 detector in 9.7 fb-1 of ppbar collisions at sqrt(s)=1.96 TeV

We present a search for the standard model (SM) Higgs boson produced in association with a Z boson in 9.7 fb-1 of ppbar collisions collected with the D0 detector at the Fermilab Tevatron Collider at sqrt(s) = 1.96 TeV. Selected events contain one reconstructed Z-> e+e- or Z-> mu+mu- candidate and at least two jets, including at least one jet identified as likely to contain a b quark. To validate the search procedure, we also measure the cross section for ZZ production in the same final state. It is found to be consistent with its SM prediction. We set upper limits on the ZH production cross section times branching ratio for H->bbbar at the 95% C.L. for Higgs boson masses 90 < M_H < 150 GeV. The observed (expected) limit for M_H = 125 GeV is 7.1 (5.1) times the SM cross section.

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arXiv2012

Search for the standard model Higgs boson in the ZH->vvbb channel in 9.5 fb-1 of ppbar collisions at sqrt(s) = 1.96 TeV

We present a search for the standard model Higgs boson in 9.5 fb-1 of ppbar collisions at sqrt(s) = 1.96 TeV 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 ppbar->ZH->vvbb production. The search is also sensitive to the WH->lvbb 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 sigma(ppbar->[Z/W]H), 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 0.94 +/- 0.31(stat) +/- 0.34(syst) times the standard model prediction of 4.4 pb, with an observed significance of 2.0 standard deviations.

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arXiv2012

Measurement of the ratio of three-jet to two-jet cross sections in pp-bar collisions at sqrt(s) = 1.96 TeV

We present a measurement of the ratio of multijet cross sections in pp-bar collisions at sqrt(s) = 1.96 TeV at the Fermilab Tevatron Collider. The measurement is based on a data set corresponding to an integrated luminosity of 0.7 fb-1 collected with the D0 detector. The ratio of the inclusive three-jet to two-jet cross sections, R3/2, has been measured as a function of the jet transverse momenta. The data are compared to QCD predictions in different approximations. Popular tunes of the PYTHIA event generator do not agree with the data, while SHERPA provides a reasonable description of the data. A perturbative QCD prediction in next-to-leading order in the strong coupling constant, corrected for non-perturbative effects, gives a good description of the data.

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