B group status and plans

1. B group status and plans Brad Abbott Sept 11, 2002

2. Very Near Term • Trying to get number for average B lifetime (Earlier statement is that we are consistent with PDG) • Addressing issues raised by EB • Issues: Single/Double Gaussian for background • Bias in vertexing • J/Psi cross section • Issues:Efficiencies

3. Very near term • B group would like to have p12 available on the farms to allow us to use D0_mess(event stripper) This will allow us to generate large MC samples. • Currently generating and verifying that p12 is working properly for B sample.

4. Near Term • Studying different tracking algorithms MC • Bs->Ds pi (Hadronic B decay) • Bs->Ds e X (Semileptonic B decay) • D*->D pi (Soft pion) • J/Psi Ks (Ks reconstruction) • Generic B decays

5. MC files • These files allow us to see performance of many of the important issues needed for B physics. • Event yields, pull distributions, vertex resolutions, flavor tagging etc. • Efficiencies for various track definitions etc.

6. Tracking algorithms in Data • J/Psi sample: Number of J/Psi, resolution, Psi`, B lifetime, B+ signal. • Standard good run: Lambda, Ks, D->Kpi?

7. Triggers • Many new triggers available for B physics: • New dimuon triggers (studying performance) • Trying to get a low Pt single muon trigger (needed for hadronic B decays -> Bs mixing). Best reach for DMs for critical for large DMs. • Emphasis has been on muons • No evidence of J/Psi in low Pt dielectron triggers.(2,2.5) EM trigger being prescaled away for now. • Tracking trigger before low Pt electrons possible? • Difficult to look at data from mu-e trigger since no criteria to search for low Pt electrons.

8. Muon ID • Seeing low efficiency for using “Saclay” matching for J/Psi-> mu mu. • Current matching is using ABC muons with Chisq>0 so does not work well for low Pt muons. • Can track extrapolation code be sped up? Discussed with Gavin, some ideas are being investigated. Trying to find someone interested in pursuing this.

9. Other issues • Streaming at L3: low Pt – high Pt stream, should be very useful for many B analyses. Have someone verifying streaming • Would like ability to set bit to allow additional reco on interesting events. Being worked on.

10. Continuing to pick events • Picking of interesting events (root files) Dimuons, single muons. These are often picked ~ 3 weeks after being written to tape. • Picking of raw events, ~ 100/week to allow us to test latest reco code etc. • Picking of small number of dimuon events soon after being collected to allow us to quickly see if problem with trigger, etc.

11. Other Issues • Continuing to ensure that our code runs on thumbnails and contains necessary information for B physics • Currently have 17 Thesis students working on B topics. Lambda_b, Chi_b, B_s mixing and Sin(2 Beta), CP violation

12. Walk before we can run • Before we can do these analyses, we need to do more “bread and butter” physics. • B lifetime, B+ signal, verify tagging performance, Bd mixing, Ks lifetime, Lambda lifetime. (Not as sexy so less interest from people, but necessary in order for people to believe our interesting results)

13. Conclusions • Focusing on underlying issues: triggers, tracking, streaming etc. • Results using muons encouraging, not so encouraging with electrons. • Waiting for track trigger to increase data size.