| 1. |
- Aaltonen, T., et al.
(author)
-
Combination of Tevatron Searches for the Standard Model Higgs Boson in the W+W- Decay Mode
- 2010
-
In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 104:6, s. 061802-
-
Journal article (peer-reviewed)abstract
- We combine searches by the CDF and D0 Collaborations for a Higgs boson decaying to W+W-. The data correspond to an integrated total luminosity of 4.8 (CDF) and 5.4 (D0) fb(-1) of p (p) over bar collisions at root s = 1.96 TeV at the Fermilab Tevatron collider. No excess is observed above background expectation, and resulting limits on Higgs boson production exclude a standard model Higgs boson in the mass range 162-166 GeV at the 95% C.L.
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| 2. |
- Aaltonen, T., et al.
(author)
-
Combination of CDF and D0 measurements of the W boson helicity in top quark decays
- 2012
-
In: Physical Review D. - 1550-7998 .- 1550-2368. ; 85:7, s. 071106-
-
Journal article (peer-reviewed)abstract
- We report the combination of recent measurements of the helicity of the W boson from top quark decay by the CDF and D0 collaborations, based on data samples corresponding to integrated luminosities of 2.7-5.4 fb(-1) of p (p) over bar collisions collected during Run II of the Fermilab Tevatron collider. Combining measurements that simultaneously determine the fractions of W bosons with longitudinal (f(0)) and right-handed (f(+)) helicities, we find f(0) = 0.722 +/- 0.081[+/- 0.062(stat) +/- 0.052(syst)] and f(+) = -0.033 +/- 0.046[+/- 0.034(stat) +/- 0.031(syst)]. Combining measurements where one of the helicity fractions is fixed to the value expected in the standard model, we find f(0) = 0.682 +/- 0.057[+/- 0.035(stat) +/- 0.046(syst)] for fixed f(+) and f(+) = -0.015 +/- 0.035[+/- 0.018(stat) +/- 0.030(syst)] for fixed f(0). The results are consistent with standard model expectations.
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| 3. |
- Abazov, V. M., et al.
(author)
-
Search for CP violation in B-s(0) -> mu(+) D-s(-) X decays in p(p)over-bar collisions at root s=1.96 TeV
- 2010
-
In: Physical Review D - Particles, Fields, Gravitation and Cosmology. - 1550-7998 .- 1550-2368. ; 82:1, s. 012003-
-
Journal article (peer-reviewed)abstract
- We have performed a search for CP violation in a sample of B-s(0) -> mu+Ds-X decays corresponding to 5 fb(-1) of proton-antiproton collisions collected by the D0 detector in Run II at the Fermilab Tevatron Collider. New physics in B-s(0) mixing could contribute a significant CP violating weak phase, which would be observed as a difference in the decay-time distribution for B-s(0) -> (B) over bar (0)(s) oscillated states versus that for (B) over bar (0)(s) -> B-s(0). A fit to the decay-time distributions of the B-s(0)/(B) over bar (0)(s) candidates yields the flavor-specific asymmetry as a(fs)(s) = [-1.7 +/- 9.1(stat)(-1.5)(+1.4)(syst) x 10(-3), which excludes CP violation due to new physics within the experimental sensitivity.
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| 4. |
- Abazov, V. M., et al.
(author)
-
Measurement of spin correlation in t(t)over-bar production using dilepton final states
- 2011
-
In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 702:1, s. 16-23
-
Journal article (peer-reviewed)abstract
- We measure the correlation between the spin of the top quark and the spin of the anti-top quark in t (t) over bar -> W(+)bW(-)(b) over bar -> l(+)vbl(-) (v) over bar(b) over bar final states produced in p (p) over bar collisions at a center of mass energy root s = 1.96 TeV, where l is an electron or muon. The data correspond to an integrated luminosity of 5.4 fb(-1) and were collected with the D0 detector at the Fermilab Tevatron collider. The correlation is extracted from the angles of the two leptons in the t and (t) over bar rest frames, yielding a correlation strength C = 0.10(-0.45)(+0.45). in agreement with the NLO QCD prediction within two standard deviations, but also in agreement with the no correlation hypothesis.
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| 5. |
- Abazov, V. M., et al.
(author)
-
Search for flavor changing neutral currents in decays of top quarks
- 2011
-
In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 701:3, s. 313-320
-
Journal article (peer-reviewed)abstract
- We present a search for flavor changing neutral currents in decays of top quarks. The analysis is based on a search for (ℓ,ℓ′=e,μ) final states using 4.1 fb−1 of integrated luminosity of collisions at . We extract limits on the branching ratio B(t→Zq) (q=u,c quarks), assuming anomalous tuZ or tcZ couplings. We do not observe any sign of such anomalous coupling and set a limit of B<3.2% at 95% C.L.
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| 6. |
- Abazov, V. M., et al.
(author)
-
Search for neutral Higgs bosons in the multi-b-jet topology in 5.2 fb(-1) of p(p)over-bar collisions at root s=1.96 TeV
- 2011
-
In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 698:2, s. 97-104
-
Journal article (peer-reviewed)abstract
- Data recorded by the DO experiment at the Fermilab Tevatron Collider are analyzed to search for neutral Higgs bosons produced in association with b quarks. The search is performed in the three-b-quark channel using multijet-triggered events corresponding to an integrated luminosity of 5.2 fb(-1). In the absence of any significant excess above background, limits are set on the cross section multiplied by the branching ratio in the Higgs boson mass range 90 to 300 GeV, extending the excluded regions in the parameter space of the minimal supersymmetric standard model. (C) 2011 Elsevier B.V. All rights reserved.
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| 7. |
- Abazov, V. M., et al.
(author)
-
Search for W' -> tb resonances with left- and right-handed couplings to fermions D0 Collaboration
- 2011
-
In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 699:3, s. 145-150
-
Journal article (peer-reviewed)abstract
- We present a search for the production of a heavy gauge boson, W', that decays to third-generation quarks, by DO Collaboration in p (p) over bar) collisions at root s = 1.96 TeV. We set 95% confidence level upper limits on the production cross section times branching fraction. For the first time, we set limits for arbitrary combinations of left-and right-handed couplings of the W' boson to fermions. For couplings with the same strength as for the standard model W boson, we set the following limits, assuming that there are right-handed neutrinos nu(R) for all three generations with M(W') > m(nu(R)): M(W') > 863 GeV for purely left-handed couplings, M(W') > 885 GeV for purely right-handed couplings, and M(W') > 916 GeV if both left-and right-handed couplings are present. The limit for right-handed couplings improves for M(W') < m(nu(R)) to M(W') > 890 GeV.
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| 8. |
- Abazov, V. M., et al.
(author)
-
Azimuthal decorrelations and multiple parton interactions in gamma+2 jet and gamma+3 jet events in p(p)over-bar collisions at root s=1.96 TeV
- 2011
-
In: Physical Review D - Particles, Fields, Gravitation and Cosmology. - 1550-7998 .- 1550-2368. ; 83:5, s. 052008-
-
Journal article (peer-reviewed)abstract
- Samples of inclusive gamma + 2 jet and gamma + 3 jet events collected by the D0 experiment with an integrated luminosity of about 1 fb(-1) in p (p) over bar collisions at root s = 1.96 TeV are used to measure cross sections as a function of the angle in the plane transverse to the beam direction between the transverse momentum (p(T)) of the gamma + leading jet system (jets are ordered in p(T)) and p(T) of the other jet for gamma + 2 jet, or p(T) sum of the two other jets for gamma + 3 jet events. The results are compared to different models of multiple parton interactions (MPI) in the PYTHIA and SHERPA Monte Carlo (MC) generators. The data indicate a contribution from events with double parton (DP) interactions and are well-described by predictions provided by the PYTHIA MPI models with p(T)-ordered showers and by SHERPA with the default MPI model. The gamma + 2 jet data are also used to determine the fraction of events with DP interactions as a function of the azimuthal angle and as a function of the second jet p(T).
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| 9. |
- Abazov, V. M., et al.
(author)
-
b-Jet identification in the D0 experiment
- 2010
-
In: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 620:2-3, s. 490-517
-
Journal article (peer-reviewed)abstract
- Algorithms distinguishing jets originating from b quarks from other jet flavors are important tools in the physics program of the D0 experiment at the Fermilab Tevatron p (p) over bar collider. This article describes the methods that have been used to identify b-quark jets, exploiting in particular the long lifetimes of b-flavored hadrons, and the calibration of the performance of these algorithms based on collider data.
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| 10. |
- Abazov, V. M., et al.
(author)
-
Measurement of color flow in t(t)over-bar events from p(p)over-bar collisions at root s=1.96 TeV
- 2011
-
In: Physical Review D - Particles, Fields, Gravitation and Cosmology. - 1550-7998. ; 83:9, s. 092002-
-
Journal article (peer-reviewed)abstract
- We present the first measurement of the color representation of the hadronically decaying W boson in t (t) over bar events, from 5.3 fb(-1) of integrated luminosity collected with the D0 experiment. A novel calorimeter-based vectorial variable, "jet pull," is used, sensitive to the color-flow structure of the final state. We find that the fraction of uncolored W bosons is 0.56 +/- 0.42(stat + syst), in agreement with the standard model.
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| 11. |
- Abazov, V. M., et al.
(author)
-
Measurement of the ratio of inclusive cross sections sigma(p(p)over-bar -> Z plus b-quark jet)/sigma(p(p)over-bar -> Z plus jet) at root s=1.96 TeV
- 2011
-
In: Physical Review D - Particles, Fields, Gravitation and Cosmology. - 1550-7998. ; 83:3, s. 031105-
-
Journal article (peer-reviewed)abstract
- The ratio of the cross section for p (p) over bar interactions producing a Z boson and at least one b-quark jet to the inclusive Z + jet cross section is measured using 4.2 fb(-1) of p (p) over bar collisions collected with the D0 detector at the Fermilab Tevatron collider at root s = 1.96 TeV. The Z -> l(+) l- candidate events with at least one b jet are discriminated from Z + charm and light jet(s) events by a novel technique that exploits the properties of the tracks associated to the jet. The measured ratio is 0: 0193 +/- 0: 0027 for events having a jet with transverse momentum p(T) > 20 GeV and pseudorapidity vertical bar eta vertical bar <= 2.5, which is the most precise to date and is consistent with theoretical predictions.
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| 12. |
- Abazov, V. M., et al.
(author)
-
Measurement of the top quark pair production cross section in the lepton plus jets channel in proton-antiproton collisions at root s=1.96 TeV
- 2011
-
In: Physical Review D. - 1550-7998 .- 1550-2368. ; 84:1, s. 012008-
-
Journal article (peer-reviewed)abstract
- We present a measurement of the inclusive top quark pair production cross section in p (p) over bar collisions at root s = 1.96 TeV utilizing data corresponding to an integrated luminosity of 5.3 fb(-1) collected with the D0 detector at the Fermilab Tevatron Collider. We consider final states containing one high-p(T) isolated electron or muon and at least two jets, and we perform three analyses: one exploiting specific kinematic features of t (t) over bar events, the second using b-jet identification, and the third using both techniques to separate the t (t) over bar signal from the background. In the third case, we determine simultaneously the t (t) over bar cross section and the ratio of the production rates of W + heavy flavor jets and W + light flavor jets, which reduces the impact of the systematic uncertainties related to the background estimation. Assuming a top quark mass of 172.5 GeV, we obtain sigma(t (t) over bar) = 7.78(-0.64)(-0.77)pb. This result agrees with predictions of the standard model.
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| 13. |
- Abazov, V. M., et al.
(author)
-
Measurement of the W boson helicity in top quark decays using 5.4 fb(-1) of p(p)over-bar collision data
- 2011
-
In: Physical Review D - Particles, Fields, Gravitation and Cosmology. - 1550-7998 .- 1550-2368. ; 83:3, s. 032009-
-
Journal article (peer-reviewed)abstract
- We present a measurement of the helicity of the W boson produced in top quark decays using t (t) over bar decays in the l + jets and dilepton final states selected from a sample of 5.4 fb(-1) of collisions recorded using the D0 detector at the Fermilab Tevatron p (p) over bar collider. We measure the fractions of longitudinal and right-handed W bosons to be f(0) = 0.669 +/- 0.102[+/- 0.078(stat.) +/- 0.065(syst.) +/- and f(+) = 0.023 +/- 0.053[+/- 0.041(stat.) +/- 0.034(syst.)], respectively. This result is consistent at the 98% level with the standard model. A measurement with f(0) fixed to the value from the standard model yields f(+) = 0.010 +/- 0.037[+/- 0.022(stat.) +/- 0.030(syst.).].
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| 14. |
- Abazov, V. M., et al.
(author)
-
Search for flavor changing neutral currents via quark-gluon couplings in single top quark production using 2.3 fb(-1) of p(p)over-bar collisions
- 2010
-
In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 693:2, s. 81-87
-
Journal article (peer-reviewed)abstract
- We present a search for flavor changing neutral currents via quark-gluon couplings in a sample of single top quark final states corresponding to 2.3 fb(-1) of integrated luminosity collected with the DO detector at the Fermilab Tevatron Collider. We select events containing a single top quark candidates with an additional jet, and obtain separation between signal and background using Bayesian neural networks. We find consistency between background expectation and observed data, and set limits on flavor changing neutral current gluon couplings of the top quark to up quarks (tgu) and charm quarks (tgc). The cross section limits at the 95% C.L. are sigma(tgu) < 0.20 pb and sigma(tgc) < 0.27 pb. These correspond to limits on the top quark decay branching fractions of B(t -> gu) < 2.0 x 10(-4) and B(t -> gc) < 3.9 x 10(-3).
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| 15. |
- Abazov, V. M., et al.
(author)
-
Search for Resonant WW and WZ Production in p(p)over-bar Collisions at root s=1.96 TeV
- 2011
-
In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 107:1, s. 011801-
-
Journal article (peer-reviewed)abstract
- We search for resonant WW or WZ production by using up to 5: 4 fb(-1) of integrated luminosity collected by the D0 experiment in run II of the Fermilab Tevatron Collider. The data are consistent with the standard model background expectation, and we set limits on a resonance mass by using the sequential standard model W' boson and the Randall-Sundrum model graviton G as benchmarks. We exclude a sequential standard model W' boson in the mass range 180-690 GeV and a Randall-Sundrum graviton in the range 300-754 GeV at 95% C. L.
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| 16. |
- Abazov, V. M., et al.
(author)
-
Search for Single Vectorlike Quarks in p(p)over-bar Collisions at root s=1.96 TeV
- 2011
-
In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 106:8, s. 081801-
-
Journal article (peer-reviewed)abstract
- We present a search for hypothetical vectorlike quarks in p (p) over bar collisions at root s = 1.96 TeV. The data were collected by the D0 detector at the Fermilab Tevatron Collider and correspond to an integrated luminosity of 5.4 fb(-1). We select events with a final state composed of a W or Z boson and a jet consistent with a heavy object decay. We observe no significant excess in comparison to the background prediction and set limits on production cross sections for vectorlike quarks decaying to W + jet and Z + jet. These are the most stringent limits to date for electroweak single vectorlike quark production at hadron colliders.
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| 17. |
- Abazov, V. M., et al.
(author)
-
Search for the rare decay B-s(0) -> mu(+)mu(-)
- 2010
-
In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 693:5, s. 539-544
-
Journal article (peer-reviewed)abstract
- We present the results of a search for the flavor changing neutral current decay B-s(0) -> mu(+)mu(-) using 6.1 fb(-1) of p (p) over bar collisions at root s = 1.96 TeV collected by the D0 experiment at the Fermilab Tevatron Collider. The observed number of B-s(0) candidates is consistent with background expectations. The resulting upper limit on the branching fraction is B(B-s(0) -> mu(+)mu(-)) < 5.1 x 10(-8) at the 95% C.L. This limit is a factor of 2.4 better than that of the previous DO analysis and the best limit to date. Published by Elsevier B.V.
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| 18. |
- Abazov, V. M., et al.
(author)
-
Search for the Standard Model Higgs Boson in the H -> WW -> lvq '(q)over-bar Decay Channel
- 2011
-
In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 106:17, s. 171802-
-
Journal article (peer-reviewed)abstract
- We present a search for the standard model Higgs boson (H) in p (p) over bar collisions at root s = 1.96 TeV in events containing a charged lepton (l), missing transverse energy, and at least two jets, using 5.4 fb(-1) of integrated luminosity recorded with the D0 detector at the Fermilab Tevatron Collider. This analysis is sensitive primarily to Higgs bosons produced through the fusion of two gluons or two electroweak bosons, with subsequent decay H -> WW -> lvq'(q) over bar, where l is an electron or muon. The search is also sensitive to contributions from other production channels, such as WH -> lvb (b) over bar. In the absence of a signal, we set limits at the 95% C.L. on the cross section for H production sigma(p (p) over bar -> H + X) in these final states. For a mass of M-H = 160 GeV, the limit is a factor of 3.9 larger than the cross section in the standard model and consistent with an a priori expected sensitivity of 5.0.
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| 19. |
- Abazov, V. M., et al.
(author)
-
Search for W H associated production in 5.3 fb(-1) of p(p)over-bar collisions at the Fermilab Tevatron
- 2011
-
In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 698:1, s. 6-13
-
Journal article (peer-reviewed)abstract
- We present a search for associated production of Higgs and W bosons in p (p) over bar collisions at a center of mass energy of root s = 1.96 TeV in 5.3 fb(-1) of integrated luminosity recorded by the DO experiment. Multivariate analysis techniques are applied to events containing one lepton, an imbalance in transverse energy, and one or two b-tagged jets to discriminate a potential WH signal from Standard Model backgrounds. We observe good agreement between data and expected backgrounds, and set an upper limit of 4.5 (at 95% confidence level and for m(H) = 115 GeV) on the ratio of the WH cross section multiplied by the branching fraction of H -> b (b) over bar to its Standard Model prediction, which is consistent with an expected limit of 4.8.
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| 20. |
- Abazov, V. M., et al.
(author)
-
Dependence of the t(t)over-bar production cross section on the transverse momentum of the top quark
- 2010
-
In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 693:5, s. 515-521
-
Journal article (peer-reviewed)abstract
- We present a measurement of the differential cross section for t (t) over bar events produced in p (p) over bar collisions at root s = 1.96 TeV as a function of the transverse momentum (p(T)) of the top quark. The selected events contain a high-p(T) lepton (l), a large imbalance in p(T). four or more jets with at least one candidate for a b jet, and correspond to 1 fb(-1) of integrated luminosity recorded with the D0 detector. Objects in the event are associated through a constrained kinematic fit to the t (t) over bar -> WbW (b) over bar -> lvbq (q) over bar' (b) over bar process. Results from next and next-to-next-to-leading-order perturbative QCD calculations agree with the measured differential cross section. Comparisons are also provided to predictions from Monte Carlo event generators using QCD calculations at different levels of precision. (C) 2010 Elsevier B.V. All rights reserved.
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| 21. |
- Abazov, V. M., et al.
(author)
-
Determination of the Width of the Top Quark
- 2011
-
In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 106:2, s. 022001-
-
Journal article (peer-reviewed)abstract
- We extract the total width of the top quark, Gamma(t), from the partial decay width Gamma(t -> Wb) measured using the t-channel cross section for single top-quark production and from the branching fraction B(t -> Wb) measured in t (t) over bar t events using up to 2.3 fb(-1) of integrated luminosity collected by the D0 Collaboration at the Tevatron p (p) over bar Collider. The result is Gamma(t) = 1.99(-0.55)(+0.69) GeV, which translates to a top-quark lifetime of tau(t) = (3.3-(+1.3)(0.9)) x 10(-25) s. Assuming a high mass fourth generation b' quark and unitarity of the four-generation quark-mixing matrix, we set the first upper limit on vertical bar V-tb'vertical bar < 0.63 at 95% C.L.
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| 22. |
- Abazov, V. M., et al.
(author)
-
Double parton interactions in gamma+3 jet events in p(p)over-bar collisions at root s=1.96 TeV
- 2010
-
In: Physical Review D. - 1550-7998 .- 1550-2368. ; 81:5, s. 052012-
-
Journal article (peer-reviewed)abstract
- We have used a sample of gamma + 3 jets events collected by the D0 experiment with an integrated luminosity of about 1 fb(-1) to determine the fraction of events with double parton scattering (f(DP)) in a single p (p) over bar collision at root s = 1.96 TeV. The DP fraction and effective cross section (sigma(eff)), a process-independent scale parameter related to the parton density inside the nucleon, are measured in three intervals of the second (ordered in p(T)) jet transverse momentum p(T)(jet2) within the range 15 <= p(T)(jet2) <= 30 GeV. In this range, f(DP) varies between 0.23 <= f(DP) <= 0.47, while sigma(eff) has the average value sigma(ave)(eff) = 16.4 +/- 0.3(stat) +/- 2.3(syst) mb.
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| 23. |
- Abazov, V. M., et al.
(author)
-
Evidence for an anomalous like-sign dimuon charge asymmetry
- 2010
-
In: Physical Review D. - 1550-7998. ; 82:13, s. 032001-
-
Journal article (peer-reviewed)abstract
- We measure the charge asymmetry A of like-sign dimuon events in 6.1 fb(-1) of p (p) over bar collisions recorded with the D0 detector at a center-of-mass energy root s = 1.96 TeV at the Fermilab Tevatron collider. From A, we extract the like-sign dimuon charge asymmetry in semileptonic b-hadron decays: A(sl)(b) = -0.00957 +/- 0.00251 (stat) +/- 0.00146 (syst). This result differs by 3.2 standard deviations from the standard model prediction A(sl)(b)(SM) = (-2.3(0.6)(+0.5)) x 10(-4) and provides first evidence of anomalous CP violation in the mixing of neutral B mesons.
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| 24. |
- Abazov, V. M., et al.
(author)
-
Evidence for an Anomalous Like-Sign Dimuon Charge Asymmetry
- 2010
-
In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 105:8, s. 081801-
-
Journal article (peer-reviewed)abstract
- We measure the charge asymmetry A =(N++ -N--)/(N++ + N--) of like-sign dimuon events in 6.1 fb(-1) of p (p) over bar collisions recorded with the D0 detector at a center-of-mass energy root s = 1: 96 TeV at the Fermilab Tevatron collider. From A we extract the like-sign dimuon charge asymmetry in semileptonic b-hadron decays: A(sl)(b) = -0.009 57 +/- 0.00251(stat) +/- 0.001 46(sys). It differs by 3.2 standard deviations from the standard model prediction A(sl)(b)(SM) = (-2.3(-0.6)(+0.5)) x 10(-4), and provides first evidence of anomalous CP violation in the mixing of neutral B mesons.
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| 25. |
- Abazov, V. M., et al.
(author)
-
High mass exclusive diffractive dijet production in p(p)over-bar collisions at root s=1.96 TeV
- 2011
-
In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 705:3, s. 193-199
-
Journal article (peer-reviewed)abstract
- We present evidence for diffractive exclusive dijet production with an invariant dijet mass greater than 100 GeV in data collected with the DO experiment at the Fermilab Tevatron Collider. A discriminant based on calorimeter information is used to measure a significant number of events with little energy (typically less than 10 GeV) outside the dijet system, consistent with the diffractive exclusive dijet production topology. The probability for these events to be explained by other dijet production processes is 2 x 10(-6), corresponding to a 4.7 standard deviation significance.
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