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

2. 18 November 2004Kroll/Bedeschi2 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  m s Blinding for  m s fit Counted more than 40 people in attendance

3. 18 November 2004Kroll/Bedeschi3 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 3 rd 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

4. 18 November 2004Kroll/Bedeschi4 Data Sets and Signal Optimization 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 Further discussion BPAK on 11/12/04? 19 Stick with ICHEP 04 selection for J/  K & l + D

5. 18 November 2004Kroll/Bedeschi5 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

6. 18 November 2004Kroll/Bedeschi6 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 (t true ) !  SVT (t reco ) –difficult behavior at t reco < 0 –not an issue in TTT (two tracks, little signal with t_{reco} < 0) Problem probably combination of several effects

7. 18 November 2004Kroll/Bedeschi7 Lifetimes (hadronic) Work on background description and fitting MIT group also looking at lifetime as step in  m fit –following Padova et al. use  (t reco ) –parameterize eff. function so that fit is analytic –significant increase in speed of fit –applying same approach to semileptonics Continued progress since workshop

8. 18 November 2004Kroll/Bedeschi8 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”

9. 18 November 2004Kroll/Bedeschi9 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 p T (B) & in cone of 0.7: p T, p T rel, p L rel, away tracks p T 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

10. 18 November 2004Kroll/Bedeschi10 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

11. 18 November 2004Kroll/Bedeschi11 Likelihood Fits for  m d 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)

12. 18 November 2004Kroll/Bedeschi12 Issues for  m s 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  m s 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

13. 18 November 2004Kroll/Bedeschi13 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  m d : remains to be seen if we meet milestone PID tools on schedule – need user experience with TOF 5.3.4 Need discussion of whole  m s procedure – not just blinding

14. 18 November 2004Kroll/Bedeschi14 Result on  m s 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  m s –03 Feb 2005 prebless results on  m s –20 Jan 2005 bless results on  m d for  m s (Collaboration mtg.) –06 Jan 2005 prebless results on  m d for  m s Better have full likelihood machinery for  m d determination using hadronic and semileptonic samples and OSTs before the Winter holiday – this includes a substantial amount of documentation prepared. From 14 October 2004

15. 18 November 2004Kroll/Bedeschi15 Calendar on week proposed B mixing workshop Collaboration meeting last Thursday meeting Gasp! now we are here! La Thuile begins here holiday

16. 18 November 2004Kroll/Bedeschi16 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