-
V. M. Abazov,
B. Abbott,
B. S. Acharya,
M. Adams,
T. Adams,
G. D. Alexeev,
G. Alkhazov,
A. Alton,
G. Alverson,
M. Aoki, [......],
H. Yin,
K. Yip,
S. W. Youn,
T. Zhao,
T. G. Zhao,
B. Zhou,
J. Zhu,
M. Zielinski,
D. Zieminska,
L. Zivkovic
[show abstract]
[hide abstract]
ABSTRACT: This report describes a search for associated production of W and Higgs bosons based on data corresponding to an integrated luminosity of L≈5.3 fb-1 collected with the D0 detector at the Fermilab Tevatron pp̅ Collider. Events containing a W→ℓν candidate (with ℓ 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 (MH). The observed and expected 95% C.L. upper limits obtained for an assumed MH=115 GeV are, respectively, factors of 4.5 and 4.8 larger than the value predicted by the standard model.
Phys. Rev. D. 08/2012; 86(3).
-
V. M. Abazov,
B. Abbott,
B. S. Acharya,
M. Adams,
T. Adams,
G. D. Alexeev,
G. Alkhazov,
A. Alton,
G. Alverson,
G. A. Alves, [......],
K. Yip,
S. W. Youn,
J. Zennamo,
T. Zhao,
T. G. Zhao,
B. Zhou,
J. Zhu,
M. Zielinski,
D. Zieminska,
L. Zivkovic
[show abstract]
[hide abstract]
ABSTRACT: We present a measurement of the elastic differential cross section dσ(pp̅ →pp̅ )/dt as a function of the four-momentum-transfer squared t. The data sample corresponds to an integrated luminosity of ≈31 nb-1 collected with the D0 detector using dedicated Tevatron pp̅ Collider operating conditions at √s=1.96 TeV and covers the range 0.26<|t|<1.2 GeV2. For |t|<0.6 GeV2, dσ/dt is described by an exponential function of the form Ae-b|t| with a slope parameter b=16.86±0.10(stat)±0.20(syst) GeV-2. A change in slope is observed at |t|≈0.6 GeV2, followed by a more gradual |t| dependence with increasing values of |t|.
Phys. Rev. D. 07/2012; 86(1).
-
V. M. Abazov,
B. Abbott,
B. S. Acharya,
M. Adams,
T. Adams,
G. D. Alexeev,
G. Alkhazov,
A. Alton,
G. Alverson,
M. Aoki, [......],
Z. Ye,
H. Yin,
K. Yip,
S. W. Youn,
T. Zhao,
B. Zhou,
J. Zhu,
M. Zielinski,
D. Zieminska,
L. Zivkovic
[show abstract]
[hide abstract]
ABSTRACT: We study the processes pp̅ →WZ→ℓ±νℓ+ℓ- and pp̅ →ZZ→ℓ+ℓ-νν̅ , where ℓ=e or μ. Using 8.6 fb-1 of integrated luminosity collected by the D0 experiment at the Fermilab Tevatron collider, we measure the WZ production cross section to be 4.50-0.66+0.63 pb which is consistent with, but slightly larger than, the prediction of the standard model. The ZZ cross section is measured to be 1.64±0.46 pb, in agreement with a prediction of the standard model. Combination with an earlier analysis of the ZZ→ℓ+ℓ-ℓ+ℓ- channel yields a ZZ cross section of 1.44-0.34+0.35 pb.
Phys. Rev. D. 06/2012; 85(11).
-
V. M. Abazov,
B. Abbott,
B. S. Acharya,
M. Adams,
T. Adams,
G. D. Alexeev,
G. Alkhazov,
A. Alton,
G. Alverson,
M. Aoki, [......],
K. Yip,
S. W. Youn,
J. Zennamo,
T. Zhao,
T. G. Zhao,
B. Zhou,
J. Zhu,
M. Zielinski,
D. Zieminska,
L. Zivkovic
[show abstract]
[hide abstract]
ABSTRACT: We measure the Λb0 lifetime in the fully reconstructed decay Λb0→J/ψΛ0 using 10.4 fb-1 of pp̅ collisions collected with the D0 detector at √s=1.96 TeV. The lifetime of the topologically similar decay channel B0→J/ψKS0 is also measured. We obtain τ(Λb0)=1.303±0.075(stat)±0.035(syst) ps and τ(B0)=1.508±0.025(stat)±0.043(syst) ps. Using these measurements, we determine the lifetime ratio of τ(Λb0)/τ(B0)=0.864±0.052(stat)±0.033(syst).
Phys. Rev. D. 06/2012; 85(11).
-
Collaboration,
V. M. Abazov,
B. Abbott,
B. S. Acharya,
M. Adams,
T. Adams,
G. D. Alexeev,
G. Alkhazov,
A. Alton,
G. Alverson, [......],
K. Yip,
S. W. Youn,
J. Zennamo,
T. Zhao,
T. G. Zhao,
B. Zhou,
J. Zhu,
M. Zielinski,
D. Zieminska,
L. Zivkovic
[show abstract]
[hide abstract]
ABSTRACT: We present a measurement of the elastic differential cross section
$d\sigma(p\bar{p}\rightarrow p\bar{p})/dt$ as a function of the
four-momentum-transfer squared t. The data sample corresponds to an integrated
luminosity of $\approx 31 nb^{-1}$ collected with the D0 detector using
dedicated Tevatron $p\bar{p} $ Collider operating conditions at sqrt(s) = 1.96
TeV and covers the range $0.26 <|t|< 1.2 GeV^2$. For $|t|<0.6 GeV^2$,
d\sigma/dt is described by an exponential function of the form $Ae^{-b|t|}$
with a slope parameter $ b = 16.86 \pm 0.10(stat) \pm 0.20(syst) GeV^{-2}$. A
change in slope is observed at $|t| \approx 0.6 GeV^2$, followed by a more
gradual |t| dependence with increasing values of |t|.
06/2012;
-
V. M. Abazov,
B. Abbott,
B. S. Acharya,
M. Adams,
T. Adams,
G. D. Alexeev,
G. Alkhazov,
A. Alton,
G. Alverson,
G. A. Alves, [......],
K. Yip,
S. W. Youn,
J. Yu,
S. Zelitch,
T. Zhao,
B. Zhou,
J. Zhu,
M. Zielinski,
D. Zieminska,
L. Zivkovic
[show abstract]
[hide abstract]
ABSTRACT: We describe a model-independent search for physics beyond the standard model in lepton final states. We examine 117 final states using 1.1 fb-1 of pp̅ collisions data at √s=1.96 TeV collected with the D0 detector. We conclude that all observed discrepancies between data and model can be attributed to uncertainties in the standard model background modeling, and hence we do not see any evidence for physics beyond the standard model.
Phys. Rev. D. 05/2012; 85(9).
-
V M Abazov,
B Abbott,
B S Acharya,
M Adams,
T Adams,
G D Alexeev,
G Alkhazov,
A Alton,
G Alverson,
G A Alves, [......],
H Yin,
K Yip,
S W Youn,
J Yu,
T Zhao,
B Zhou,
J Zhu,
M Zielinski,
D Zieminska,
L Zivkovic
[show abstract]
[hide abstract]
ABSTRACT: We study WW and WZ production with ℓνqq (ℓ=e,μ) final states using data collected by the D0 detector at the Fermilab Tevatron Collider corresponding to 4.3 fb(-1) of integrated luminosity from pp collisions at sqrt[s]=1.96 TeV. Assuming the ratio between the production cross sections σ(WW) and σ(WZ) as predicted by the standard model, we measure the total WV (V=W,Z) cross section to be σ(WV)=19.6(-3.0)(+3.2) pb and reject the background-only hypothesis at a level of 7.9 standard deviations. We also use b-jet discrimination to separate the WZ component from the dominant WW component. Simultaneously fitting WW and WZ contributions, we measure σ(WW)=15.9(-3.2)(+3.7) pb and σ(WZ)=3.3(-3.3)(+4.1) pb, which is consistent with the standard model predictions.
Physical Review Letters 05/2012; 108(18):181803. · 7.37 Impact Factor
-
The SELEX Collaboration,
A. Blanco-Covarrubias,
J. Engelfried,
U. Akgun,
G. Alkhazov,
J. Amaro-Reyes,
A. G. Atamantchouk,
A. S. Ayan,
M. Y. Balatz,
N. F. Bondar, [......],
A. N. Vasiliev,
D. V. Vavilov,
E. Vázquez-Jáuregui,
V. S. Verebryusov,
V. A. Victorov,
V. E. Vishnyakov,
A. A. Vorobyov,
K. Vorwalter,
J. You,
R. Zukanovich-Funchal
[show abstract]
[hide abstract]
ABSTRACT: Using data taken by SELEX during the 1996–1997 fixed target run at Fermilab, we study the production of charmed hadrons on
copper and carbon targets withΣ
−, p, π
−, and π
+ beams. Parametrizing the dependence of the inclusive production cross section on the atomic number A as A
α
, we determine α forD
+, D
0, D
s
+, D
+(2010), Λ
c
+, and their respective anti-particles, as a function of their transverse momentum p
t
and scaled longitudinal momentumx
F
. Within our statistics there is no dependence of α on x
F
for any charm species for the interval 0.1<x
F
<1.0. The average value of α for charm production by pion beams is α
meson=0.850±0.028. This is somewhat larger than the corresponding average α
baryon=0.755±0.016 for charm production by baryon beams (Σ
−, p).
PACS13.85.Ni-14.65.Dw-24.85.+p
European Physical Journal C 04/2012; 64(4):637-644. · 3.63 Impact Factor
-
V M Abazov,
B Abbott,
B S Acharya,
M Adams,
T Adams,
G D Alexeev,
G Alkhazov,
A Alton,
G Alverson,
M Aoki, [......],
H Yin,
K Yip,
S W Youn,
T Zhao,
T G Zhao,
B Zhou,
J Zhu,
M Zielinski,
D Zieminska,
L Zivkovic
[show abstract]
[hide abstract]
ABSTRACT: We present a measurement of the W boson mass using data corresponding to 4.3 fb(-1) of integrated luminosity collected with the D0 detector during Run II at the Fermilab Tevatron pp collider. With a sample of 1,677,394 W → eν candidate events, we measure M(W) = 80.367 ± 0.026 GeV. This result is combined with an earlier D0 result determined using an independent Run II data sample, corresponding to 1 fb(-1) of integrated luminosity, to yield M(W) = 80.375 ± 0.023 GeV.
Physical Review Letters 04/2012; 108(15):151804. · 7.37 Impact Factor
-
V M Abazov,
B Abbott,
B S Acharya,
M Adams,
T Adams,
G D Alexeev,
G Alkhazov,
A Alton,
G Alverson,
M Aoki, [......],
Z Ye,
H Yin,
K Yip,
S W Youn,
T Zhao,
B Zhou,
J Zhu,
M Zielinski,
D Zieminska,
L Zivkovic
[show abstract]
[hide abstract]
ABSTRACT: We present a search for Kaluza-Klein (KK) particles predicted by models with universal extra dimensions (UED) using a data set corresponding to an integrated luminosity of 7.3 fb(-1), collected by the D0 detector at a pp center-of-mass energy of 1.96 TeV. The decay chain of KK particles can lead to a final state with two muons of the same charge. This signature is used to set a lower limit on the compactification scale of R(-1)>260 GeV in a minimal UED model.
Physical Review Letters 03/2012; 108(13):131802. · 7.37 Impact Factor
-
V M Abazov,
B Abbott,
B S Acharya,
M Adams,
T Adams,
G D Alexeev,
J Alimena,
G Alkhazov,
A Alton,
G Alverson, [......],
H Yin,
K Yip,
S W Youn,
J Yu,
T Zhao,
B Zhou,
J Zhu,
M Zielinski,
D Zieminska,
L Zivkovic
[show abstract]
[hide abstract]
ABSTRACT: We report on a search for charged massive long-lived particles (CMLLPs), based on 5.2 fb(-1) of integrated luminosity collected with the D0 detector at the Fermilab Tevatron pp collider. We search for events in which one or more particles are reconstructed as muons but have speed and ionization energy loss (dE/dx) inconsistent with muons produced in beam collisions. CMLLPs are predicted in several theories of physics beyond the standard model. We exclude pair-produced long-lived gauginolike charginos below 267 GeV and Higgsino-like charginos below 217 GeV at 95% C.L., as well as long-lived scalar top quarks with mass below 285 GeV.
Physical Review Letters 03/2012; 108(12):121802. · 7.37 Impact Factor
-
V. M. Abazov,
B. Abbott,
B. S. Acharya,
M. Adams,
T. Adams,
G. D. Alexeev,
G. Alkhazov,
A. Alton,
G. Alverson,
G. A. Alves, [......],
H. Yin,
K. Yip,
S. W. Youn,
J. Yu,
T. Zhao,
B. Zhou,
J. Zhu,
M. Zielinski,
D. Zieminska,
L. Zivkovic
[show abstract]
[hide abstract]
ABSTRACT: We present a measurement of pp̅ →Zγ→ℓ+ℓ-γ (ℓ=e, μ) production with a data sample corresponding to an integrated luminosity of 6.2 fb-1 collected by the D0 detector at the Fermilab Tevatron pp̅ Collider. The results of the electron and muon channels are combined, and we measure the total production cross section and the differential cross section dσ/dpTγ, where pTγ is the momentum of the photon in the plane transverse to the beam line. The results obtained are consistent with the standard model predictions from next-to-leading order calculations. We use the transverse momentum spectrum of the photon to place limits on anomalous ZZγ and Zγγ couplings.
Phys. Rev. D. 02/2012; 85(5).
-
The CDF,
Collaborations: T. Aaltonen,
V. M. Abazov,
B. Abbott,
B. S. Acharya,
M. Adams,
T. Adams,
G. D. Alexeev,
G. Alkhazov,
A. Alton, [......],
J. C. Yun,
A. Zanetti,
Y. Zeng,
T. Zhao,
B. Zhou,
J. Zhu,
M. Zielinski,
D. Zieminska,
L. Zivkovic,
S. Zucchelli
[show abstract]
[hide abstract]
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 ppbar
collisions collected during Run II of the Fermilab Tevatron Collider. Combining
measurements that simultaneously determine the fractions of W bosons with
longitudinal (f0) and right-handed (f+) helicities, we find f0 = 0.722 \pm
0.081 [\pm 0.062 (stat.) \pm 0.052 (syst.)] and f+ = -0.033 \pm 0.046 [\pm
0.034 (stat.) \pm 0.031 (syst.)]. Combining measurements where one of the
helicity fractions is fixed to the value expected in the standard model, we
find f0 = 0.682 \pm 0.057 [\pm 0.035 (stat.) \pm 0.046 (syst.)] and f+ =
-0.015\pm0.035 [\pm 0.018 (stat.) \pm 0.030 (syst.)]. The results are
consistent with standard model expectations.
02/2012;
-
V. M. Abazov,
B. Abbott,
B. S. Acharya,
M. Adams,
T. Adams,
G. D. Alexeev,
G. Alkhazov,
A. Alton,
G. Alverson,
G. A. Alves, [......],
K. Yip,
S. W. Youn,
J. Yu,
S. Zelitch,
T. Zhao,
B. Zhou,
J. Zhu,
M. Zielinski,
D. Zieminska,
L. Zivkovic
[show abstract]
[hide abstract]
ABSTRACT: We report an updated measurement of the CP-violating phase, ϕsJ/ψϕ, and the decay-width difference for the two mass eigenstates, ΔΓs, from the flavor-tagged decay Bs0→J/ψϕ. The data sample corresponds to an integrated luminosity of 8.0 fb-1 accumulated with the D0 detector using pp̅ collisions at √s=1.96 TeV produced at the Fermilab Tevatron collider. The 68% Bayesian credibility intervals, including systematic uncertainties, are ΔΓs=0.163-0.064+0.065 ps-1 and ϕsJ/ψϕ=-0.55-0.36+0.38. The p-value for the Standard Model point is 29.8%.
Phys. Rev. D. 02/2012; 85(3).
-
Collaboration,
V. M. Abazov,
B. Abbott,
B. S. Acharya,
M. Adams,
T. Adams,
G. D. Alexeev,
G. Alkhazov,
A. Alton,
G. Alverson, [......],
Z. Ye,
H. Yin,
K. Yip,
S. W. Youn,
T. Zhao,
B. Zhou,
J. Zhu,
M. Zielinski,
D. Zieminska,
L. Zivkovic
[show abstract]
[hide abstract]
ABSTRACT: We present a search for the pair production of scalar top quarks
($\tilde{t}_{1}$), the lightest supersymmetric partners of the top quarks, in
$p\bar{p}$ collisions at a center-of-mass energy of 1.96 TeV, using data
corresponding to an integrated luminosity of {7.3 $fb^{-1}$} collected with the
\dzero experiment at the Fermilab Tevatron Collider. Each scalar top quark is
assumed to decay into a $b$ quark, a charged lepton, and a scalar neutrino
($\tilde{\nu}$). We investigate final states arising from $\tilde{t}_{1}
\bar{\tilde{t}_{1}} \rightarrow b\bar{b}\mu\tau \tilde{\nu} \tilde{\nu}$ and
$\tilde{t}_{1} \bar{\tilde{t}_{1}} \rightarrow b\bar{b}\tau\tau \tilde{\nu}
\tilde{\nu}$. With no significant excess of events observed above the
background expected from the standard model, we set exclusion limits on this
production process in the ($m_{\tilde{t}_{1}}$,$m_{\tilde{\nu}}$) plane.
02/2012;
-
V M Abazov,
B Abbott,
B S Acharya,
M Adams,
T Adams,
G D Alexeev,
G Alkhazov,
A Alton,
G Alverson,
G A Alves, [......],
H Yin,
K Yip,
S W Youn,
J Yu,
T Zhao,
B Zhou,
J Zhu,
M Zielinski,
D Zieminska,
L Zivkovic
[show abstract]
[hide abstract]
ABSTRACT: We present a measurement of the ratio of events with correlated t and t ̅t spins to the total number of t ̅t events. This ratio f is evaluated using a matrix-element-based approach in 729 t ̅t candidate events with a single lepton ℓ (electron or muon) and at least four jets. The analyzed p ̅p collisions data correspond to an integrated luminosity of 5.3 fb(-1) and were collected with the D0 detector at the Fermilab Tevatron collider operating at a center-of-mass energy √s=1.96 TeV. Combining this result with a recent measurement of f in dileptonic final states, we find f in agreement with the standard model. In addition, the combination provides evidence for the presence of spin correlation in t ̅t events with a significance of more than 3 standard deviations.
Physical Review Letters 01/2012; 108(3):032004. · 7.37 Impact Factor
-
V M Abazov,
B Abbott,
B S Acharya,
M Adams,
T Adams,
G D Alexeev,
G Alkhazov,
A Alton,
G Alverson,
G A Alves, [......],
K Yip,
S W Youn,
J Yu,
S Zelitch,
T Zhao,
B Zhou,
J Zhu,
M Zielinski,
D Zieminska,
L Zivkovic
[show abstract]
[hide abstract]
ABSTRACT: We present a search for pair production of doubly charged Higgs bosons in the processes qq¯→H(++)H(--) decaying through H(±±)→τ(±)τ(±),μ(±)τ(±),μ(±)μ(±). The search is performed in pp¯ collisions at a center-of-mass energy of √s = 1.96 TeV using an integrated luminosity of up to 7.0 fb(-1) collected by the D0 experiment at the Fermilab Tevatron Collider. The results are used to set 95% C.L. limits on the pair production cross section of doubly charged Higgs bosons and on their mass for different H(±±) branching fractions. Models predicting different H(±±) decays are investigated. Assuming B(H(±±)→τ(±)τ(±))=1 yields an observed (expected) lower limit on the mass of a left-handed H(L)(±±) boson of 128 (116) GeV and assuming B(H(±±)→μ(±)τ(±))=1 the corresponding limits are 144 (149) GeV. In a model with B(H(±±)→τ(±)τ(±))=B(H(±±)→μ(±)τ(±))=B(H(±±)→μ(±)μ(±))=1/3, we obtain M(H(L)(±±))>130 (138) GeV.
Physical Review Letters 01/2012; 108(2):021801. · 7.37 Impact Factor
-
V. M. Abazov,
B. Abbott,
B. S. Acharya,
M. Adams,
T. Adams,
G. D. Alexeev,
G. Alkhazov,
A. Alton,
G. Alverson,
G. A. Alves, [......],
K. Yip,
S. W. Youn,
J. Yu,
S. Zelitch,
T. Zhao,
B. Zhou,
J. Zhu,
M. Zielinski,
D. Zieminska,
L. Zivkovic
[show abstract]
[hide abstract]
ABSTRACT: We present a measurement of forward-backward asymmetry in top quark-antiquark production in proton-antiproton collisions in the final state containing a lepton and at least four jets. Using a data set corresponding to an integrated luminosity of 5.4 fb-1, collected by the D0 experiment at the Fermilab Tevatron Collider, we measure the tt̅ forward-backward asymmetry to be (9.2±3.7)% at the reconstruction level. When corrected for detector acceptance and resolution, the asymmetry is found to be (19.6±6.5)%. We also measure a corrected asymmetry based on the lepton from a top quark decay, found to be (15.2±4.0)%. The results are compared to predictions based on the next-to-leading-order QCD generator mc@nlo. The sensitivity of the measured and predicted asymmetries to the modeling of gluon radiation is discussed.
Phys. Rev. D. 12/2011; 84(11).
-
V M Abazov,
B Abbott,
B S Acharya,
M Adams,
T Adams,
G D Alexeev,
G Alkhazov,
A Alton,
G Alverson,
G A Alves, [......],
K Yip,
S W Youn,
J Yu,
S Zelitch,
T Zhao,
B Zhou,
J Zhu,
M Zielinski,
D Zieminska,
L Zivkovic
[show abstract]
[hide abstract]
ABSTRACT: We measure the cross section and the difference in rapidities between photons and charged leptons for inclusive W(→lν) + γ production in eγ and μγ final states. Using data corresponding to an integrated luminosity of 4.2 fb(-1) collected with the D0 detector at the Fermilab Tevatron Collider, the measured cross section times branching fraction for the process pp → Wγ + X → lνγ + X and the distribution of the charge-signed photon-lepton rapidity difference are found to be in agreement with the standard model. These results provide the most stringent limits on anomalous WWγ couplings for data from hadron colliders: -0.4<Δκ(γ)<0.4 and -0.08<λ(γ)<0.07 at the 95% C.L.
Physical Review Letters 12/2011; 107(24):241803. · 7.37 Impact Factor
-
V. M. Abazov,
B. Abbott,
B. S. Acharya,
M. Adams,
T. Adams,
G. D. Alexeev,
G. Alkhazov,
A. Alton,
G. Alverson,
G. A. Alves, [......],
K. Yip,
S. W. Youn,
J. Yu,
S. Zelitch,
T. Zhao,
B. Zhou,
J. Zhu,
M. Zielinski,
D. Zieminska,
L. Zivkovic
[show abstract]
[hide abstract]
ABSTRACT: We present measurements of production cross sections of single top quarks in pp̅ collisions at √s=1.96 TeV in a data sample corresponding to an integrated luminosity of 5.4 fb-1 collected by the D0 detector at the Fermilab Tevatron Collider. We select events with an isolated electron or muon, an imbalance in transverse energy, and two, three, or four jets, with one or two of them containing a bottom hadron. We obtain an inclusive cross section of σ(pp̅ →tb+X,tqb+X)=3.43±0.740.73 pb and use it to extract the CKM matrix element 0.79<|Vtb|≤1 at the 95% C.L. We also measure σ(pp̅ →tb+X)=0.68±0.350.38 pb and σ(pp̅ →tqb+X)=2.86±0.630.69 pb when assuming, respectively, tqb and tb production rates as predicted by the standard model.
Phys. Rev. D. 12/2011; 84(11).
