1 / 20

Novosibirsk

Moscow State University. For the D0 collaboration. Valentin Kuzmin. Novosibirsk. February 27 - March 2. Phi Psi 2006. Russia. 2006. In this talk we report On. D** mesons Observed by D0 detector and Searches of Flavor Changing Neutral Current Charm Decays. -.

cbaur
Télécharger la présentation

Novosibirsk

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Moscow State University For the D0 collaboration Valentin Kuzmin Novosibirsk February 27 - March 2 Phi Psi 2006 Russia 2006

  2. In this talk we report On D** mesons Observed by D0 detector and Searches of Flavor Changing Neutral Current Charm Decays PhiPsi 2006

  3. - • Run I (1992 – 1995) √s = 1.8 TeV • delivered ~ 260 pb-1 • Run II (2002 – ) √s = 1.96 TeV • collisions every 396 ns • rate to tape 50 Hz • delivers ~ 15 pb-1/week (January 2006) • max luminosity 1.58·1032 (January 2006) - Tevatron pp-collider More than 1.4 fb-1 delivered &1.2 fb-1 recorded data for physics Feb 2002 April 2001 Jul 2002 first data for analyses detector commissioning • So far reconstructed ~1 fb-1 ~10x the total Run I data PhiPsi 2006

  4. The DZero Experiment • Beam line shielding • Reduces accelerator background • Silicon tracker • Coverage up to |η| <2 • Fiber tracker • Coverage up to | η| <2 • 8 double layers • Solenoid (2 Tesla) • Forward + central muon system • Coverage up to | η | <2 • Three level trigger system • Outputs 50 Hz PhiPsi 2006

  5. D** mesons Four orbitally excited D-meson states, collectively known as D** • Previous studies by various experiments • Theoretical interest of Heavy Quark Effective Theory (HQET) • hyperfine splitting between states • with different jq • semileptonic branching fractions (B  D**) are among least model-dependent predictions • D0 has studies on the narrow (jq=3/2) resonances D1(2420),D2*(2460) decaying  D*+π Four (L=1) resonant states decaying thru • S-waves expected to be wide (~100MeV) (jq=1/2) • D-waves expected to be narrow (~20MeV) (jq=3/2) seen by various experiments PhiPsi 2006

  6. _ _ _ _ _ D**, signal selection • Data: 460 pb-1 • Search for : BD1,2* + µνX in chain:D1,2* D*- + π+ , D*-D0 + π- ,D0K+ + π- • selection all events with D0 and µ, (216870±1280 events) • combine withπ-and selectD* (55450±280 events) • suppression cc by cuts on significance and proper decay length of theBmeson (31160±230 D*- events) • in such events combine D*- and π- • Fit found signal with two relativistic Breit-Wigner’s functions convoluted with the detector • resolution and 2nd order polynom(bkgnd). Fixed [PDG] M(D2*)-M(D1)and widths PhiPsi 2006

  7. D** mesons properties Semileptonic (B→D**) branching fractions and their ratio PDG PDG MC • Assuming that the D1 meson decays • only intoD*π • Assuming that the D2* meson decays • into D*π in (30±6)% of the cases [PDG] • Ratio (first direct measurement) • HQET = 1.6│mc= ∞ Different from PDG value (0.74 ±0.16)% by 2.5σ In agreement with [PDG] 95% CL upper limit 0.65% PhiPsi 2006

  8. DS1 meson search are orbitally excited states of meson We will look for narrow (L=1,jq=3/2,JP=1+) in Data: 485pb-1 Muon plus 5-Track final state 52670±330 D* candidates In 0.142-0.149GeV mass difference window 5900±100 candidates 0.47 0.52 PhiPsi 2006

  9. Evidence of DS1(2536)meson D±s1(2536) signal Gaussian for the signal plus an exponential with a threshold cutoff at M(D*) +M(KS) 0 • 18.5±5.5 D±s1(2536) candidates • 2536±1 MeV/c2 position • 3.4σ significance Towards investigation of D±s1(2536) properties — there are no experimental measurements of Br(BS→DS**) PhiPsi 2006

  10. D±→m+m- p PRD66 (2002) 014009 f RPV SUSY ω SM c→u m(m+m-) (GeV/c2) FCNC searches Motivation • For every rare SM process there is a “beyond the SM” theory in which it is enhanced. • RPV SUSY can enhance SM suppressed FCNC processes. • FCNC processes with down type quarks • s->d type studied with kaons (K±,K0) • b->s type studied with B mesons. • FCNC processes with up type quarks • Still lot of room for new results • In this talk we focus on c→u transitions PhiPsi 2006

  11. FCNC c -> u transitions with D± & Ds± D±→μ+μ- π Ds±→μ+μ- π • Non-resonant decays (GIM suppressed, Br~10-8) • Non-resonant decays (Penguin & Box diagrams absent) • Resonant decay • (Analogous to b->sl+l- studies after • B+->K+J/ψ->K+μ+μ- observation) Penguin Box Br(Ds± → φπ) (3.6±0.9)x10-2 Br(φ → μ+μ-) (2.85±0.19)x10-4 • Resonant decay (dominant, Br~10-6) • Observation = essential step to study c->ul+l- FCNC transitions – – – • In pp collisions at √s = 1.96 TeV σ(pp → cc) ~ microbarns • Ds± production mechanisms at the Tevatron: • Prompt production: pp -> cc -> Ds±+X • Secondary production: pp ->bb ->B+X -> Ds±+Y+X • Ds±and D± decay products tend to be within a narrow jet – – – – PhiPsi 2006 – – – –

  12. MC Sum Prompt secondary FCNC, data selection Data: 508pb-1 • Μ = χ2πμμ-vtx + (1/pT(π))2 + (ΔRπ)2 • χ2πμμ-vtx - three particle vertex • ΔRπ– transverse distance between • π and (μμ)system ω f  min(M) Sideband data for background studies 0.96 < m(μ+μ-) < 1.06 GeV/c2 π track selection • Track in the same jet as μ+μ- pair. • Track from the same vertex as the μ+μ- pair. Ds± and D± signal region Ds± and D± selection • μ+μ- & π track form a good vertex • 1.3 < m(μ+μ- π ) < 2.5 GeV/c2 • p(μ+μ- π) in the PV→SV direction 3.3 candidate/event Do you see the Ds± or D± ? PhiPsi 2006

  13. FCNC, background suppression variables To minimize background, we employ 4 variables: • ID: tracking isolation of Ds± ID=p(D)/Σp(cone), cone ΔR < 1 • SD: transverse flight length significance of Ds± SD = Lxy/σ(Lxy) • RS: ratio of π impact parameter significance to SD • RS= (IPπ/σ(IPπ))/SD • θD: collinearity angle Angle between direction PV→SV and p(Ds±) we use likelihood function of these variables to extract Ds± and D± PhiPsi 2006

  14. Correlated Independent Combined likelihood variable θD vs SD • Isolation ID is independent of SD,θD & RS • SD,θD & RS are independent if SV well separated from PV • Combined likelihood “L” reflecting correlations: L=L(ID)xL(SD,θD,RS)if SD <20 L=L(ID)xL(SD)xL(θD)xL(RS) if SD >20 Likelihood Ratio “d” Signal Background • Plot likelihood ratio “d” : • d=L(Signal)/(L(Signal)+L(Background)) PhiPsi 2006

  15. FCNC, signal extraction • The red histogram is after selection d>0.9 In the Ds± region 1.91 <m(μ+μ- π) <2.03 GeV/c2 • 51 events found • 18±4 background events expected 31±7 Ds± events observed (corresponds to >7σ significance) • Relax cut on likelihood ratio to 0.75 and Fit 2 Gaussians (signal) & exponential (background) • Free Number(Ds±),mean(Ds±), σ(Ds±), Number(D±) • Fix mean(Ds±)-mean(D±) to 1.969-1.869 GeV • Fix σ(D±) to m(D±)/m(Ds±) x σ(Ds±) • Use the above found mean(Ds±), σ(Ds±) and fit the d>0.9 distribution need more data for observation, we will set the upper limit on D± -> μ+μ-π decays 13.2+5.6-4.9 D± events observed (corresponds to >2.7σ significance) PhiPsi 2006

  16. Br(D± →φπ →μ+μ- π) Br(D± →φπ →μ+μ- π) <0.28 (90% C.L) = 0.17 Br(Ds± →φπ →μ+μ- π) Br(Ds± →φπ →μ+μ- π) FCNC, branching ratios Br(D± →φπ →μ+μ- π) N(D±) f(Ds±) ε(Ds±) x x = ε(D±) Br(Ds± →φπ →μ+μ- π) N(Ds±) f(D±) Measured or Limit Setting To determine PDG Literature From MC ±0.08±0.06 ±0.07±0.07 PDG: Br(Ds± →φπ)·Br(φ→μ+μ-) +0.79+0.76 Br(D± →φπ →μ+μ- π) = (1.70 )x10-6 Br(D± →φπ →μ+μ- π) <3.14x10-6 (90% C.L) -0.73 -0.82 In agreement with expected [PDG]:Br(D± →φπ)· Br(φ→μ+μ-) =1.75 x10-6 +3.6 and the CLEO measurement: (2.7 -1.8 ±0.2) x10-6 PhiPsi 2006

  17. Conclusion • Using 460pb-1 of DØ’s data sample we observe semileptonic decays of B in D10(2420),D2*0(2460). The narrow D** mesons branching fractions were separately measured for such decays. The ratio between semileptonic fractions of the two modes is R=1.31±0.29(stat)±0.47(syst) in agreement with HQET • The D0 Collaboration also observes the Ds1(2536) resonance and the measurement of its properties is in progress. • We see final state of the decay Ds± →φπ →μ+μ- πwith a significance of 7 standard deviations. DØ has nice sensitivity to study FCNC in charm decays and we now continue to search the non-resonant continuum for signs of physics going beyond the Standard Model. • Tevatron is doubling the luminosity each year MORE GREAT PHYSICS RESULTS are coming soon PhiPsi 2006

  18. Back up

  19. PhiPsi 2006

  20. Result: Br ( D± → π± μ+μ- ) limit UL ∞ ∫drL (r) ∫drL (r) 0 0 Br(D±→fπ→μ+μ- π) N(D±;>0.9) f(Ds±) ε(Ds±;d>0.75) = x x Br(Ds±→fπ→μ+μ- π) N(Ds±;>0.75) f(D±) ε(D±;d>0.9) To determine PDG Literature From Limit Setting From MC • 90% C.L. upper limit on Br(D±→fπ→μ+μ- π) found by: N(D±;>0.9) = 0.9, where r= N(Ds±;>0.75) Uncertainties summary Br(D±→fπ→μ+μ- π) < 0.28 (at 90% C.L.) Br(Ds±→fπ→μ+μ- π) Br ( D± →π± μ+μ-) < 3.14 x 10-6 (at 90% C.L.) PhiPsi 2006

More Related