B physics results from DØ DØ detector Tracker Tracking per as long as mance Tracking per as long as mance

B physics results from DØ DØ detector Tracker Tracking per as long as mance Tracking per as long as mance www.phwiki.com

B physics results from DØ DØ detector Tracker Tracking per as long as mance Tracking per as long as mance

Modenessi, Jennifer, Features Writer has reference to this Academic Journal, PHwiki organized this Journal B physics results from DØ Jan Stark (LPSC Grenoble) as long as the DØ Collaboration Moriond EW, March 21-28, 2004 DØ detector Tracker Trigger: muon+track covers <2.2 SMT+ CFT max = 1.65 8×2 CFT layers SMT region max = 2.5 4 SMT layers = - ln (tan(/2)) SMT Strayer University-Newport News Campus VA www.phwiki.com

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Tracking per as long as mance Impact Parameter Resolution (DCA) 53 m @ PT = 1 GeV in addition to 15 m @ higher PT Can provide K/ separation as long as Ptot< 400 MeV p/ separation as long as Ptot<700 MeV NOT yet used as long as PID SMT dE/dx MC Data Tracking per as long as mance as long as kaons from DD0 pT spectrum of soft pion from DD0 Efficient muon in addition to tracking system give us a large sample of semileptonic B decays Tracks are reconstructed over a wide range starting from pT = 180 MeV Data from semileptonic decays (B m D X) X(3872) J/ + - Last summer, Belle announced a new particle at 3872 MeV/c2, observed in B+ decays: B+ K+ X(3872), X(3872) J/ + -. Belle’s discovery has been confirmed by CDF in addition to DØ. DØ preliminary: 300 61 events 4.4 effect M = 0.768 0.004 (stat) 0.004 (syst) GeV/c2 X(3872) production properties What kind of particle is the X - charmonium - an exotic meson molecule - something else Compare our sample of X particles to our sample of (2S), e.g. - split into two regions (plot), - two bins in decay length dl: dl < 0.02 cm: 230 59 events dl > 0.02 cm: 77 25 events X(3872) (2S) comparison No significant differences between (2S) in addition to X have been observed yet. This comparison will be even more useful once we have models of the production in addition to decay of, e.g., meson molecules that predict the observables used in the comparison. Observation of the charged analog X+ J/ + 0 would rule out cc hypothesis. Observation of radiative decays X c would favour cc hypothesis (Belle set limit). Use Dzero’s calorimeter to identify low energy 0 in addition to : work in progress. (B+)/(B0) from semileptonic decays Have record statistics of reconstructed semileptonic B+ in addition to B0 decays in h in addition to . First application: measure lifetime ratio (B+)/(B0) will show some other applications later Sample compositions: “D0 sample”: + K+ – + (anything except slow ) B+ 82 % B0 16 % Bs 2 % “D sample”: + D0 – + anything B+ 12 % B0 86 % Bs 2 % Estimates based on measured branching fractions in addition to isospin relations.

(B+)/(B0): fitting strategy Group events into 8 bins of Visible Proper Decay Length (VPDL): Measure ri = N(+ D-)/N(+ D0) in each bin i. Combinatorial background with true D0 in D sample is subtracted using wrong-sign distribution (normalisation from full sample, previous slide). no need as long as parameterisation of background VPDL distribution Additional inputs to the fit: – sample compositions (previous slide) – K-factors (from simulation) K = pT(D0) / pT(B) [separately as long as different (groups of) decay modes] – Relative reconstruction efficiencies CY as long as different decay modes B Y (from simulation) – Slow pion reconstruction efficiency [flat as long as pT(D0) > 5 GeV (one of our cuts)] – Decay length resolution (from simulation) – (B+) = 1.674 0.018 ps [PDG] one example VPDL bin VPDL = LT / pT( D0) MB LT = transverse decay length (B+)/(B0): results Preliminary result: (B+)/(B0) = 1.093 0.021 (stat) 0.022 (syst) Syst. dominated by: – time dependence of slow reconstruction efficiency – relative reconstruction efficiencies CY – Br(B+ + D- + X) – K-factors – decay length resolution differences D0 D The preliminary DØ measurement is one of the most precise results, in addition to it is consistent with previous measurements. Exclusive B decays Can also reconstruct hadronic B decays exclusively ( improved proper time resolution). Some examples on the right. Preliminary lifetime measurement using B0 J/(+-) KS(+-): (B0) = 1.56 (stat) 0.13 (syst) ps Consistent with world average: (B0) = 1.542 0.016 ps [PDG] B0 J/(+-) KS(+-) b J/(+-) (p -) lxy/(lxy)>4.5 114 pb-1 N = 39 12 250 pb-1

B0/B0 mixing The B0/B0 mixing frequency md has been measured with high precision, most recently at the B factories. Measurements of md constrain Vtd, but current limitations are due to theoretical inputs. We use our large sample of semileptonic B0/B0 decays to measure md: – benchmark the initial state flavour tagging results in this talk are based on opposite side muon tags – can also constrain more exotic models of b production at hadron colliders e.g. Berger et al., Phys. Rev. Lett. 86, 4231 (2001) B0 B0/B0 mixing: results Preliminary results: md = 0.506 0.055 (stat) 0.049 (syst) ps-1 Syst. dominated by uncertainty on +D- yield per VPDL bin. Consistent with world average: 0.502 0.007 ps-1 Tagging efficiency: Tagging purity: Work in progress: – also use electron tags – other tagging methods: jet charge, same side tagging. 250 pb-1 Bs decays Semileptonic decays: – Very good statistics – If ms 15 ps-1 expect a measurement with 500 pb-1. Fully reconstructed hadronic decays: – Poor statistics – Excellent proper time resolution – Need a few fb-1 of data to reach ms 18 ps-1.

Observation of B D X Figure from CLEO Collaboration, hep-ex/9908009 Plot on the right summarises D meson spectroscopy. Qualitative underst in addition to ing from HQET (heavy quark limit) Spin of heavy quark becomes conserved quantity (good quantum number). Angular momentum of light degrees of freedom also becomes good quantum number. Expect sets of doublets, e.g. (D1, D2). Sates of this particular doublet decay via D-wave narrow. The D10, D20 have been observed in addition to studied in several experiments, most recently by BaBar in addition to Belle in B- D0 – [hep-ex/0308026, hep-ex/0307021]. We study D10, D20 produced in semileptonic B decays. Constrain D spectroscopy; also improve underst in addition to ing of the sample of semileptonic B decays we use as long as lifetime, mixing, measurements. Observation of B D X Start from our “B D- + anything” sample, in addition to “reconstruct another +”. Look at mass of D- + system. Work in progress: extract separate amplitude, phase as long as each state. wrong-sign combinations Excess in right-sign combinations can be interpreted as combined effect of D10 in addition to D20. From topological analyses at LEP we know: Br(B D+ – X) = 0.48 0.10 % Dؒs preliminary result constrains the resonant contribution Br(B {D10,D20} X) Br({D10,D20} D+ -) = 0.280 0.021 (stat) 0.088 (syst) % . Bs + – sensitivity study Bs + – is a promising window on possible physics beyond the SM. In the SM, the expected branching ratio is small: Br(Bs + -) = (3.4 0.5) 10-9 [Buras, Phys. Lett. B566 115 (2003)] Bd + – is suppressed by additional factor Vtd/Vts 410-2. MSSM: Br(Bs + -) tan6 at large tan , enhancement of up to 2-3 orders of magnitude [Dedes et al., FERMILAB-PUB-02-129-T] Background rejection via – isolation of muon pair – decay length – opening angle between in addition to Data (L dt 100 pb-1) loose selection

Bs + – sensitivity study Optimised cuts using R in addition to om Grid Search [Prosper, CHEP’95; Punzi, CSPP’03] based on the mass sideb in addition to s. After optimisation: expect 7.3 1.8 background events in signal region Expected limit (Feldman/Cousins): Br(Bs + -) < 9.1 10-7 @ 95 % CL (stat only) Br(Bs + -) < 1.0 10-6 @ 95 % CL (stat + syst) (expected signal has been normalised to B J/ K ) 180 pb-1 The analysis has not been unblinded yet (signal region still hidden). Published CDF Run I result (98 pb-1): Br(Bs + -) < 2.6 10-6 @ 95 % CL Summary Observation of the X(3872) at DØ; study of production properties Precise measurement of (B+)/(B0) Measurement of md, benchmark flavour tagging Observation of B D X at DØ Dؒs sensitivity to Bs The exciting times have started; stay tuned as long as more. Reminder: all results are preliminary. Backup slides Flavour tagging: figure of merit Opposite side muon tags: Dilution: D = 2 -1 = 0.460 0.045 Figure of merit: D2 = 1.01 0.20 % Summary: older results Modenessi, Jennifer Contra Costa Times Features Writer www.phwiki.com

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