4 th B Mixing Workshop Summary (4 November 2004)

1. 4th B Mixing Workshop Summary(4 November 2004) Joseph Kroll (Penn) Franco Bedeschi (INFN-Pisa) CDF B Meeting 11 November 2004 18

2. Topics Covered • Triggers for B physics • Data sets for B mixing • Hadronic and semileptonic signal optimization • Lifetime measurements in hadronic and semileptonics • Combined opposite side tag using blessed ICHEP ’04 tags • Same side tagging, Monte Carlo tuning, B** • dE/dx, TOF, combined particle ID • Fits for mixing including input to fit • Systematics for limit for ms • Blinding for ms fit Counted more than 40 people in attendance Kroll/Bedeschi

3. Overall Impression • Group has transformed from end of summer complacency to focused preparation for La Thuile & beyond • people are working very hard • A lot of activity in subgroups – full agendas • Requiring weekly reports very helpful too • Since 3rd workshop: significant progress in some areas • Other areas progress may be too slow to make La Thuile • need to focus further effort there • We are revising the schedule and list of tasks • includes producing more detailed preblessing/blessing schedule Kroll/Bedeschi

4. Data Sets and Signal Optimization Further discussion BPAK on 11/12/04? • Data sets are a concern • BsNtuple • ready for J/, l + D (but without final TOF) • B hadronic started ~ 1 November (was expected done 8 Nov) • Italian skim • 25% missing, not all concatenated – no plan for completion provided • does not contain modes like B! D • Signal optimization • not much new in hadronic modes • K. Gibson presented optimization in semileptonic modes • signals consistent with previous MIT signals • good cross-check to give us confidence in selection 19 Stick with ICHEP 04 selection for J/ K & l + D Kroll/Bedeschi

5. Suggested Strategy for B Hadronics • Stick with the selection criteria used in BF ratio analysis • verify there are no lifetime related criteria that compromise mixing • We have to do this anyway • not enough time to reproduce MC templates for signal/background • Continue to try to complete Italian skim • Make sure B hadronic BsNtuple completed asap • when it’s done, run over entire data set and produce a list of run and event numbers (datlist) • Use datlist to produce signal sample that all can use • full event for those using charmods • can remake BsNtuples in various versions if necessary Kroll/Bedeschi

6. Lifetimes (semileptonics) • Continue to pursue solutions to the “lifetime problem” • More hypotheses eliminated as sole cause of discrepancy • Using 8 GeV lepton sample (no SVT bias) • is the lifetime okay? • Investigating additional backgrounds • none on their own is sufficient to explain discrepancy • try using SVT(ttrue) ! SVT(treco) • difficult behavior at treco < 0 • not an issue in TTT (two tracks, little signal with t_{reco} < 0) • Problem probably combination of several effects Kroll/Bedeschi

7. Lifetimes (hadronic) • Work on background description and fitting • MIT group also looking at lifetime as step in m fit • following Padova et al. use (treco) • parameterize eff. function so that fit is analytic • significant increase in speed of fit • applying same approach to semileptonics • Continued progress since workshop Kroll/Bedeschi

8. Opposite Side Flavor Tags • Tagging code in 5.3.4 – including SECVTX updates (speed) • Reproducing old results – almost done • unexpected subtleties with l + SVT side selection (4 SVX hits on l) • Tag overlap investigated – reasonable scheme defined • combined performance close to what we expected • Measurement of tag performance in other samples • behind schedule • but progress since workshop – see semilept. on 9 & 16Nov. 2004 • We need more people here • independent checks extremely important • needs more time to “stabilize” Kroll/Bedeschi

9. MC Tuning, B**, PID, SS(K)T • MC tuning progress since last workshop • Factor 2 in msel=1 MC sample (Bowler fragmentation) • MC describes data very well in many kinematic quantities • pT(B) & in cone of 0.7: pT, pTrel, pLrel, • away tracks pT okay,  has some discrepancies • 5.3.4 frozen – includes fragmentation z and hard scatter type • ready to begin large MC production (semileptonics for SST study) • B** • clear signal in B±! J/ K± • showed progress on understanding signal • plan to turn out a result by mid-December Kroll/Bedeschi

10. MC Tuning, B**, PID, SS(K)T • Combined particle id ready for blessing (public code there) • includes dE/dx & TOF for single tracks & track pairs • TOF release • big effort led to 5.3.4 release • ad-hoc corrections missed release – OK – can apply on ntuple level • waiting for new BsNtuples to validate on data • SS(K)T studies • added PID parameterization to MC • without PID data and MC agree very well • with PID – see discrepancy - use likelihood ratio to select K (LR>0) • LR>0: more K in data than MC; LR<0: more  in MC than data • still under investigation Kroll/Bedeschi

11. Likelihood Fits for md • MIT focused on fitting for lifetime (necessary prereq.) • ANL/CMU • fit is ready – tested now with realistic MC • added EBE PV, L00, taggers to ntuples (optimization work too) • Still need to close the loop – very high priority • even if lifetime issue not resolved, need to push to the end soon • MIT working on adding mixing cosine term (speed issue again) • there will be surprises – best to find out about them early • re-examining likelihood formulation (“Punzi effect”) • since workshop also examining alternate form (B. Wicklund) • must close the loop to measure our OST dilution (& sensitivity) Kroll/Bedeschi

12. Issues for ms • Blinding – proposal is to scramble B flavor at decay • document produced on schedule • presentation produced lively discussion • raises issue of signing off on procedure as well as blinding • Study of effect of systematics on ms sensitivity • OST – uncertainty has potential 10% effect on amplitude • lifetime resolution – need to understand scale factor to 10% no one (that we know of) is working on this Kroll/Bedeschi

13. Comment on Schedule(Looking at our plan as shown on B Mixing web page) • Behind on hadronic data sets • update on datlist and data sets this week @ BPAK • also L00 alignment in “e” data set (post COT recovery) • Probably stick with signal selection criteria as they are now • Expect update on hadronic lifetimes on 22 Nov 2004 • OST validation taking longer than expected (help?) • SS(K)T proceeding – need to formulate plan for PR blessing • Closing loop for md: remains to be seen if we meet milestone • PID tools on schedule – need user experience with TOF 5.3.4 • Need discussion of whole ms procedure – not just blinding Kroll/Bedeschi

14. From 14 October 2004 Result on ms • Difficult to work this far ahead – we can work backwards from La Thuile & draw some conclusions: • 24 Feb 2005 last day to bless results for La Thuile • 17 Feb 2005 unblind results on ms • 03 Feb 2005 prebless results on ms • 20 Jan 2005 bless results on md for ms (Collaboration mtg.) • 06 Jan 2005 prebless results on md for ms • Better have full likelihood machinery for md determination using hadronic and semileptonic samples and OSTs before the Winter holiday – this includes a substantial amount of documentation prepared. Kroll/Bedeschi

15. Calendar Gasp! now we are here! on week proposed B mixing workshop Collaboration meeting last Thursday meeting holiday La Thuile begins here Kroll/Bedeschi

16. Summary • Significant directed effort underway • Progress in many areas but goal of result by La Thuile remains very ambitious • Continuing to revisit schedule • try to prepare more detailed blessing schedule • Thanks to all who contributed to workshop • Two warnings for the future: • must devote necessary effort (people) to triggers to ensure we get data to tape for B mixing & B physics in the future • must start organizing for data sets for Summer 05 now – we need a workable solution different from what we have done in the past Kroll/Bedeschi