dzero experiment recent results
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DZero experiment Recent results. Теватрон вышел на проектную светимость, и в настоящее время за 1 месяц работы набирается интегральная светимость больше чем во всём Run I. Сейчас интегральная светимость – ~ 5 fb -1 , к концу 2009 г. – 6- 7 fb -1 , 2010 – 8-9 fb -1 , 2011 ?. - PowerPoint PPT PresentationTRANSCRIPT
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DZero experiment
Recent results
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Теватрон вышел на проектную светимость, и в настоящее время за 1 месяц работы набирается интегральная светимость больше чем во всём Run I.
Сейчас интегральная светимость – ~ 5 fb-1, к концу 2009 г. – 6-7 fb-1, 2010 – 8-9 fb-1, 2011 ?
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800 000 micro strips, Δx= 50 – 70 μm
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PNPI
Readout electronics for 50 000 mini drift tubesSoftware for the data acquisition by our electronicsSoftware for the electronics interfaceDetermination of the D0-Tevatron luminosityCalibration of the D0 CalorimeterCalibration of the D0 ICDReprogramming of the electronicsEstimation of the D0 SM background for top quark and Higgs boson physics
Publications
~ 20 in 2007~ 40 in 2008~ 100 in total during Run IIOur contribution - 1 paper
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Top quark cross section production: σ = 6.8 +/- 0.6 pb
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Assuming that production isgoverned by the SM, Topquark mass can be extractedcomparing the measured cross section with theory
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t - anti-t forward-backward asymmetry
pp → tt + X
Events where the top quark is moreforward with respect to the p-beam
Events where the anti-top quark is moreforward with respect to the p-beam
The SM NLO QCD – Abf = 5-10%First measurement (D0): Abf = 12 +/- 8 %
The measured Abf is consistent with the MC NLO SM predictions
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Mt & MW → MH
mt ~ gold atom
It is the only bare quark.It decays so quickly thatthe strong force does notconfine it.
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Single top quark production for the first time was observed at D0
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D0
CDF
0.68 ≤ |Vtb| ≤ 1.0
SM → Vtb ≈ 1.0 (6 quarks)
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B – B mixing and oscillations
|B1› = ( |B› + |B› ) / √2 = |BH› BH → MH, ΓH
|B2› = ( |B› - |B› ) / √2 = |BL› BL → ML, ΓL
If initially start with a B →
Prob[B](t) = [ exp(-Γ1t) + exp(-Γ2t) + 2 exp(-Γt) cos(Δmt)]
Prob[B](t) = [ exp(-Γ1t) + exp(-Γ2t) - 2 exp(-Γt) cos(Δmt)]
A={N[B](t) – N[B](t)}/{N[B](t) + N[B](t)} ≈ cos(Δmt)
Asymmetry A
Δm = MH – ML
ΔΓ = ΓL - ΓH
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Bs0 oscillations Bs
0 – (bs) τ(Bs) ≈ 1.5 ps
|Vtd|/|Vts|=0.21 +/- 0.01
This result rules out some versions of the SUSY theory which predict faster rates of oscillations
Bs0 → μ+ Ds
– X, Ds
– → φπ–, φ→K+ K–
Δms ~ |VtbVts|2, Δmd ~ |VtbVtd|2
SM: Δms = 21 +5 -4 ps-1 D0: 17 ≤ Δms ≤ 21 ps-1
CDF: Δms = 17.3 +0.4 – 0.2 ps-1
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Bs0 mixing parameters
Bs0 → J/ψ φ
J/ψ → μ+μ–
Φ → K+K–
SM → Φs = – 0.04 +/- 0.01
Time-dependent angulardistributions of μ+, μ–, K+, K–
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First direct observation of the strange b baryon Ξb-
The STANDARD MODEL d us cb t
Md=6 MeV, Mu=3 MeV,Ms=100 MeV, Mc=1.2 GeV,Mb=4.4 GeV, Mt=173 GeV
Λb(udb) was observed previously
Ξb−(dsb) - ? – indirect evidence was obtained at the CERN LEP collider
An excess of Ξ− events was observed in jets.
This excess was interpreted as due to Ξb− → Ξ− l − X
The lifetime of Ξb− was estimated to be 1.4 +/- 0.3 ps.
The mass of Ξb− is expected to be 5.7 – 5.8 GeV
DELPHI 1995, ALEPH 1996, DELPHI 2004.
D0 – first direct observation of Ξb− -- Phys. Rev. Lett. 99, 052001 (2007)
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Ξb− → J/ + Ξ−
J/ → + -
Ξ− → −
→ p −
J/ (cc) M=3.097 GeV
Ξ− (dss) M=1.315 GeV, = 290 ps.
(uds) M=1.116 GeV, = 263 ps.
(Ξb−) = ~ mm
(Ξ−) = ~ 5 cm
(Λ) = ~ 5 cm
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Mass spectrum of Ξ
–
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Mass spectrum of Ξb–
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M(Ξb−)=5.774 +/- 0.19 GeV
15 событий над фоном в 3 события.
Significance - 5.5 .
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First observation of the doubly strange b baryon Ωb-
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M(Ω-) = 1.672 Gev/c2
Mass spectrum of Ω –
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M(Ωb-) , theory: 5.9 – 6.1 GeV/c2
probability of background fluctuation - < 7*10-8
Mass spectrum of Ωb–
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Higgs search at DZero
Higgs production rate excluded on the 95% C.L.
Previous studies – MHiggs > 114 GeV Indirect evidence – MHiggs < 180 GeV
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D0+CDF exclude a Higgs boson with a mass of ~170 GeV at the 95% confidential level.
Combined D0 and CDF result
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First observation of double Z production
pp → ZZ ZZ → 4e, 4μ, 2e2μ Observed 3 events, the background being 0.14 events.Theory: σ = 1.4 +/- 0.1 pb. The significance is 5.7 σExperiment D0: σ = 1.6 +/- 0.6 pb,Experiment CDF: σ = 1.4 +/- 0.7 pb.
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M[X(3872)] = 3871.61 +- 0.16 (stat) +- 0.19 (syst) MeV/c2; M[D0] + M[D0*] = 3.871.81
X(3872) – (cc), (ccqq), (D0D0*) ?
X(3872) → J/ψ ππ ψ(2S) → J/ψ ππ X(3872) is not a 4 quark state
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Inclusive jet production
pQCD – perturbative QCD
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Распределения по поперечному импульсу лидирующей струи дляодно- , дважды- , трижды- и четырежды инклюзивным событиям:(a), (b), (c) и (d), соответственно. Гистограммы показывают результаты моделирования PYTHIA.
Г. Обрант
Данные свидетельствуюто большом (~50%) вкладев сечение множественныхпартонных взаимодействий
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b and c quarks in the proton
Production rate for photons in association with a b quark (left) or a c quark (right) versus the photon transverse momentum
pp → γ + b pp → γ + c
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Димюонный спектр в области инвариантной массы Bs→2µ
Br(Bs →2µ) = 5.1 → 0.9*10-7 95% CL → 10-8 ?
(SM - 3*10-9)
Bs→2µ
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Search for excited electrons
Leptons and quarks consist of3 fermions or a boson and a fermion ?
The distribution of the e2γ invariant masscompared with the SM expectation and a possible e* signal for me* = 100 GeV
D0 → no evidence of e* with m[e*] ≤ 800 GeV
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Search for charged massive “stable” particles(tau sleptons, gaugino-like charginos, higgsino-like charginos,candidates for dark matter)
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No evidence for such particles. σ < 0.3 – 0.04 pb for stau masses 60 – 300 GeV
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Search for scalar or vector particles decaying into Zγ
Z → l+l-
Experimental limits on the production cross section:M = 140 GeV – σ ≤ 3 pb, M = 600 GeV – σ ≤ 0.2 pb.
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Search for large extra dimensions
Kaluza-Klein graviton
pp → g + γ register a photon with pt > 90 GeV and Et _miss > 70 GeV
Lower limits on the fundamental massscale MD
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Поиск квантовой гравитации
pp → W(Z) + g W → μ + ν g – Kaluza-Klein graviton
Отбор: малая суммарная энергия в калориметре, большой поперечный импульс μ – мезона, большая недостающая поперечная энергия. pp → W(Z) + g modernized generator has been included to Pythia 8.3
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MET distribution of the data for pt(μ) > 15 GeV, Σ Et (calorimeter) < 15 GeV.
In 2009, simulations of the MET spectrum for the signal, simulations of the background processes.
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CDF
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