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 ?

micro strips, Δx= 50 – 70 μm

PNPI Readout electronics for mini drift tubes Software for the data acquisition by our electronics Software for the electronics interface Determination of the D0-Tevatron luminosity Calibration of the D0 Calorimeter Calibration of the D0 ICD Reprogramming of the electronics Estimation of the D0 SM background for top quark and Higgs boson physics Publications ~ 20 in 2007 ~ 40 in 2008 ~ 100 in total during Run II Our contribution - 1 paper

Top quark cross section production: σ = 6.8 +/- 0.6 pb

Assuming that production is governed by the SM, Top quark mass can be extracted comparing the measured cross section with theory

t - anti-t forward-backward asymmetry pp tt + X Events where the top quark is more forward with respect to the p-beam Events where the anti-top quark is more forward with respect to the p-beam The SM NLO QCD – A bf = 5-10% First measurement (D0): A bf = 12 +/- 8 % The measured A bf is consistent with the MC NLO SM predictions

M t & M W M H m t ~ gold atom It is the only bare quark. It decays so quickly that the strong force does not confine it.

Single top quark production for the first time was observed at D0

D0 CDF 0.68 |V tb | 1.0 SM V tb 1.0 (6 quarks)

B – B mixing and oscillations |B 1 = ( |B + |B ) / 2 = |B H B H M H, Γ H |B 2 = ( |B - |B ) / 2 = |B L B L M L, Γ L If initially start with a B Prob[B](t) = [ exp(-Γ 1 t) + exp(-Γ 2 t) + 2 exp(-Γt) cos(Δmt)] Prob[B](t) = [ exp(-Γ 1 t) + exp(-Γ 2 t) - 2 exp(-Γt) cos(Δmt)] A={N[B](t) – N[B](t)}/{N[B](t) + N[B](t)} cos(Δmt) Asymmetry A Δm = M H – M L ΔΓ = Γ L - Γ H

B s 0 oscillations B s 0 – (bs) τ( B s ) 1.5 ps |V td |/|V ts |=0.21 +/ This result rules out some versions of the SUSY theory which predict faster rates of oscillations B s 0 μ + D s – X, D s – φπ –, φK + K – Δm s ~ |V tb V ts | 2, Δm d ~ |V tb V td | 2 SM: Δm s = ps -1 D0: 17 Δm s 21 ps -1 CDF: Δm s = – 0.2 ps -1

B s 0 mixing parameters B s 0 J/ψ φ J/ψ μ + μ – Φ K + K – SM Φ s = – / Time-dependent angular distributions of μ +, μ –, K +, K –

First direct observation of the strange b baryon Ξ b - The STANDARD MODELd u s c b t M d =6 MeV, M u =3 MeV, M s =100 MeV, M c =1.2 GeV, M b =4.4 GeV, M t =173 GeV Λ b (udb) was observed previously Ξ b (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 Ξ b Ξ l X The lifetime of Ξ b was estimated to be 1.4 +/- 0.3 ps. The mass of Ξ b is expected to be 5.7 – 5.8 GeV DELPHI 1995, ALEPH 1996, DELPHI D0 – first direct observation of Ξ b -- Phys. Rev. Lett. 99, (2007)

Ξ b 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. (Ξ b ) = ~ mm (Ξ ) = ~ 5 cm (Λ) = ~ 5 cm

Mass spectrum of Ξ –

Mass spectrum of Ξ b –

M(Ξ b )= / GeV 15 событий над фоном в 3 события. Significance

First observation of the doubly strange b baryon Ω b -

M(Ω - ) = Gev/c 2 Mass spectrum of Ω –

M(Ω b - ), theory: 5.9 – 6.1 GeV/c 2 probability of background fluctuation - < 7*10 -8 Mass spectrum of Ω b –

Higgs search at DZero Higgs production rate excluded on the 95% C.L. Previous studies – M Higgs > 114 GeV Indirect evidence – M Higgs < 180 GeV

D0+CDF exclude a Higgs boson with a mass of ~170 GeV at the 95% confidential level. Combined D0 and CDF result

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 σ Experiment D0: σ = 1.6 +/- 0.6 pb, Experiment CDF: σ = 1.4 +/- 0.7 pb.

M[X(3872)] = (stat) (syst) MeV/c2; M[D 0 ] + M[D 0 *] = X(3872) – (cc), (ccqq), (D 0 D 0 *) ? X(3872) J/ψ ππ ψ(2S) J/ψ ππ X(3872) is not a 4 quark state

Inclusive jet production pQCD – perturbative QCD

Распределения по поперечному импульсу лидирующей струи для одно-, дважды-, трижды- и четырежды инклюзивным событиям: (a), (b), (c) и (d), соответственно. Гистограммы показывают результаты моделирования PYTHIA. Г. Обрант Данные свидетельствуют о большом (~50%) вкладе в сечение множественных партонных взаимодействий

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 + bpp γ + c

Димюонный спектр в области инвариантной массы B s 2µ Br(B s 2µ) = * % CL ? (SM - 3*10 -9 ) B s 2µ

Search for excited electrons Leptons and quarks consist of 3 fermions or a boson and a fermion ? The distribution of the e 2 γ invariant mass compared with the SM expectation and a possible e* signal for m e * = 100 GeV D0 no evidence of e* with m[e*] 800 GeV

Search for charged massive stable particles (tau sleptons, gaugino-like charginos, higgsino-like charginos, candidates for dark matter)

No evidence for such particles. σ < 0.3 – 0.04 pb for stau masses 60 – 300 GeV

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.

Search for large extra dimensions Kaluza-Klein graviton pp g + γ register a photon with p t > 90 GeV and E t _ miss > 70 GeV Lower limits on the fundamental mass scale M D

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

MET distribution of the data for p t (μ) > 15 GeV, Σ E t (calorimeter) < 15 GeV. In 2009, simulations of the MET spectrum for the signal, simulations of the background processes.

CDF