Status of B s Mixing at CDF

15 October 2004 Kroll/Bedeschi Collaboration Meeting

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Status of Bs Mixing at CDF

Joseph Kroll (Penn) & Franco Bedeschi (INFN Pisa)Mixing Analysis Coordinators15 October 2004 – CDF Collaboration Meeting

2nd St. Ocean City, NJ, 7 Feb 2004


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Outline:1.Physics importance & current knowledge of ms

2.Method of measurement3.Organization of CDF B mixing analyses4.Recent progress5.Summary6.Appendix: schedule

Manasquan Inlet, NJ, 25 December 2003


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Goal of Flavor Physics

Measure parameters of the CKM Matrix

Test consistency: do measurements of the same parameter withdifferent decays & CP asymmetries give the same result?

Is it unitary? B0 flavor oscillations (md)measure one side

How do B0s oscillations (ms)

fit in this picture?

Why is ms consideredone of the most important Run II measurements?


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Neutral B Meson Flavor Oscillations

Flavor oscillations occur through2nd order weak interactions

e.g.

Same diagrams and formula for ms for Bs except replace “d” with “s”

All factors known well except “bag factor” £ “decay constant”

md = 0.502 § 0.007 ps-1 (2%) (PDG 2004) from Lattice QCD calculations – see hep-ph/0406184

From measurement of md derive |V*tbVtd|2


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B Meson Flavor Oscillations (cont)

If we measure ms then we would know the ratio ms/md

Many theoretical quantities cancel in this ratio, we are left with

from Lattice QCD – see hep-ph/0406184

Since Vts ¼ Vcb this gives us our sideThis is why ms ishigh priority in Run II

md well measured: |V*tbVtd| limited by theoretical uncertainties


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Current Status of ms

Results from LEP, SLD, CDF I ms > 14.5 ps-1 95% CL

see http://www.slac.stanford.edu/xorg/hfag/osc/winter_2004/index.html

Amplitude method:H-G. Moser, A. Roussarie,NIM A384 p. 491 (1997)


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Experimental Steps for Measuring Bs Mixing

1. Extract B0s signal – decay mode must identify b-flavor at decay (TTT)

Examples:

2. Measure decay time (t) in B rest frame (L = distance travelled) (L00)

3. Determine b-flavor at production “flavor tagging” (TOF)

“unmixed” means production and decay flavor are the same

“mixed” means flavor at production opposite flavor at decay

Flavor tag quantified by dilution D = 1 – 2w, w = mistag probability


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Measuring Bs Mixing (cont.)

4. Measure asymmetry

these formulas assume perfect resolution for t

Asymmetry is conceptual: actually perform likelihood fit to expected“unmixed” and “mixed” distributions

Measure md

to validate procedure


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Comment on : Time Integrated Mixing

is the time integrated mixing probability

In principle, a measurement of determines m - the first Bd mixing measurements were measurements - d = 0.186 § 0.004 (PDG 2004) - this does not work for Bs: s = 0.5 (the limit as x!1)

A measurement of

is very interesting


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B Flavor Tagging

We quantify performance with efficiency and dilution D

= fraction of signal with flavor tag

D = 1-2w, w = probability that tag is incorrect (mistag)

Statistical error A on asymmetry A (N is number of signal)

statistical error scales with D2


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Two Types of Flavor Tags

Opposite side

Same side Based on fragmentation tracks or B**

+ Applicable to both B0 and B0s

− other b not always in the acceptance

− Results for B+ and B0 not applicable to B0s

+ better acceptance for frag. tracks than opp. side b

Reminder: for limit on ms must know D

Produce bb pairs: find 2nd b, determine flavor,infer flavor of 1st b


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Same Side Flavor Tags

Based on correlation betweencharge of fragmentation particleand flavor of b in B meson

Decay of P-wave mesonsB** also contributesto B0, B+ (not B0

s)

Expected correlationsdifferent for B+, B0, B0

sTOF


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Illustration of Bs Oscillations

Example of Asymmetrywith lots of statisticsms = 20 ps-1

Illustrated are - tagging reduces statistics dilution reduces amplitude - decay length resolution damps amplitude further - momentum uncertainty damps amplitude more as decay time t increases

Large ms: Bs! Ds l no goodneed fully reconstructed decayse.g., Bs! Ds


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CDF Bs Mixing History & Organization

• Expected Bs mixing to come early in Run II– turned out not to be the case

• Bs task force created by Tony Liss late Fall 2003• Task force report issued June 2004 (CDFNOTE 7042)• MACs appointed to help organize & coordinate

– Franco Bedeschi (INFN-Pisa) & Joseph Kroll (Penn)

• MACs began in June 2004• Have held three workshops

– 9 June 2004– 12 July 2004 (close out on 14 July)– 1 October 2004

• Current focus is Winter Conferences 2005• Also planning for longer term: Summer 2005 & beyond


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Workshop Agenda from 1 October 2004

• Flavor tagging continued– PID around B mesons (D. Usynin/Penn)– SSKT MC studies (P. Catastini/Pisa)– Status of PID (R. Snider/FNAL)

• Fitting for md

– Terms for likelihood (I. Kravchencko/MIT)– md with J/ K (N. Leonardo/MIT)– md with semileptonics (G.Giurgiu/CMU)

• Preparing for results on ms

– t in SST biased samples (discussion)– Summary and Schedule (J. Kroll/Penn) see

B meeting on 14 October

• Introduction (F. Bedeschi/Pisa)• Proposal for blind analysis (G. Punzi/Pisa)• Status of data sets (Ch. Paus/MIT)• Signals

– Semileptonic (G. Gomez-Ceballos/MIT)– Hadronic (A. Belloni/MIT)– Ds

+! K0S K+ (M. Casarsa/Padova)

• Status of lifetimes– Semileptonic (S. Farrington/Liverpool)– Hadronic (F. Azfar/Oxford)

• Flavor tagging– Summary of OSTs (I. Kravchenko/MIT)– Plan for SSKT (F. Bedeschi/Pisa)– Monte Carlo Tuning (E. Ben-Haim/Paris6)

also involved: ANL, Brandeis, Cantabria, Chicago, Geneva, JHU, Karlsruhe, LBNL/Berkeley, Pittsburgh, Purdue, Rome, Tsukuba, Yale

Big effort involving > 20CDF institutions


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Significant Progress Since June 2004

• Blessed Mixing w SST & OST in l + D (CDFNOTE 7127)

• Blessed update mixing w SST in hadronics (CDFNOTE 7145)

• Blessed several flavor tags– improved soft muon tag (CDFNOTE 7043)– improved/extended jet charge tag (CDFNOTE 7131)– new soft electron tag (CDFNOTE 7121)

• Blessed improved evaluation of sensitivity (CDFNOTE 7170)

• Updated semileptonic/hadronic signals (PR plots)• All of above presented at ICHEP 2004 (50% B Summer 04 results)• improved lifetime resolution w event-by-event PV & L00• Studies of SSKT underway – using TOF & dE/dx, MC tuning• Working towards competitive limit on ms for Winter 2005

– summary of activities with people & schedule appended at end of talk


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Examples of Progress on B0s Signals

“Golden mode” Ds mode


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Examples of B0 & B+ Calibration Signals

6 & 8 track modes!


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Progress on Lifetimes

Know how to measure lifetimeswhen there is no SVT trigger bias

Do we get correct lifetime from SVT biased signals?

CDF: B+)=1.662 § 0.033 § 0.008 ps(PDG 2004 (B+) = 1.671 § 0.018 ps)

Outstanding mystery in lepton + SVT sampleExpect 488 m (14)

Recent progress in understandingwhat is NOT the problem

Need result from B! D (2 SVT)


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Results on Opposite Side Flavor Tags

Lepton tags

Jet charge tag

Kaon tag

mistags from

SLT(): D2 = (0.70 § 0.04 § 0.05)% SLT(e): D2=(0.37 § 0.03 § 0.06)%

jet from b (b) has negative (positive) charge on average

Run II:D2 = (0.72 § 0.03)%

lower higher D

higher lower D

Largest D2 @ B factories Run II: no useful tag yet(have seen D, too low)

TOF

includes lifetime info too


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Fully Exploit Tag Power by “Binning”

B

pTrel

pTrel

Larger pTrel increases b!

suppresses b! c!, fakes

e.g., pTrel for soft leptons

Dilution dependence determined from dataRequires enormous statistics of lepton + SVT sample


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Fully Exploit Tag Power by “Binning”

Dilution increases with Q_{jet}e.g., Qjet for jet-charge

Need unbinned likelihood fit to exploit dilution binning


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Progress on Same Side (Kaon) Tagging

• SST (re)established in Run II in B0 mixing– B0: D2 = (1.04 § 0.15 § 0.17)%

– B+: D2 = (4.69 § 0.49 § 0.36)%

• SSKT predicted to be most powerful flavor tag for Bs

• Problem: cannot measure D without seeing oscillations– Limit requires knowledge of D (to predict sensitivity)

– do not know if Monte Carlo prediction of D is reliable

• Have ambitious program to compare data and MC for SST– established short term goals

• comparison of fragmentation particles in Monte Carlo to data

• establish B** signals

• measure kaons around B+, B0, Bs in data & MC – should see difference

• Best performance of dE/dx and TOF is critical


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Fit for md & D in lepton + D with OSTs1st time in Run I or II (only SST in Run I)

D = (28§2)% soft muon tag

SECVTX Jet ChargeD = (19§ 1)%

md = 0.593 § 0.53 ps D2 = 0.8% (OST only) D2 = 1.8% (OST & SST)

These are binned asymmetry fitsDo not exploit full power of OSTs(binning in Qjet, pT

rel not used)


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ICHEP 2004: Our Projected Sensitivity

Baseline: D2 = 1.6% (OST only) = 67 fs (achieved)

Stretch: D2 = 2.6% (add SST) = 47 fs (L00, event by evt. PV)

Uses full unbinned likelihood to estimate sensitivity for l Ds

See CDFNOTE 7170 v2.0

(more like 74 fs)

(OST is SLT(e) = 0.4% + SLT() = 0.7% + JQT = 0.7%)


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ICHEP 2004 Projected Sensitivity (cont)

Hadronic Semileptonic


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ICHEP 2004 Projected Sensitivity (cont)

Message: even with only OSTcould have sensitivitycomparable to best experiment.

Combined semileptonic and hadronic

Good motivation to work hard


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Highest Priority Items

1. Unbinned likelihood fit for md exploiting full power of flavor tags, event by event t, S/B in different modes, etc.

2. Resolve lifetime problem in semileptonic modes (l Ds)

3. Measure lifetime in SVT-biased hadronic modes (Ds, etc.)

With blessed OST’s, 1, 2, & 3 may be enough to say something

to accomplish 1. we must

in parallel with 1, 2, 3 4. Study SSKT – determine defensible D from data and MC


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Summary

• Large group of people (> 20 institutes) dedicated to crucial components of Bs mixing measurement

• Significant progress was made this summer – we continue to work towards a 1st result in Winter 2005

• A lists of tasks with responsible people & deadlines is available – see Appendix to this talk. It will continue to evolve.

There is still room to get involvedThis is a long term analysis

It is a collaborative effort“No physicist left behind”


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Appendix: Schedule

Notes:1. There is a web page in preparation – see B web page2. The names on the following schedule indicate the people who are responsible for the particular tasks now & in the future. Many other collaborators contributed to these tasks

in a significant way in the past.


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Schedule

• We have put together a list of tasks

• Each task has– list of people doing the work

• these people are considered “responsible” for delivering

– the venue where they report the results of their work• specify the subgroup or B group

– the various near term tasks including time estimates

– long term tasks have more vague time estimates

• Weekly status reports– we want status reports at subgroups on key tasks every week

– does not have to be full presentation, can be one slide on previous week’s activities


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Data Sets

• Data set definition– 5.3.X

– all data up to August 2004 shutdown except COT compromised

• Good run list– Furic & Nahn

– reports at BPAK

– by 4 November 2004

• Skim of SVT two track data set– Belforte, Casarsa, Delli, Fella,

Lucchesi

– reports at BPAK

– 2 sections of the data• up to 13 February 2004

• after COT recovery

• Skim (continued)– Status of data up to 13 Feb 2004

• Bs! Ds, Ds! K*K or KSK complete

• finish other 7 modes by 4 Nov 2004

• B-! D0-, D0! K+-, K+-+-, K+K-, +-

• B0! D-+, D-! K-++

• B0s! Ds

-+, Ds! ,

– post COT recovery data• processing in parallel with above

• complete by end of November 2004

– Some modes not included• e.g., B! D* & D• can be added – no time estimate


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Data Sets (continued)

• B Sntuple– Paus

– reports at BPAK

– based on 5.3.1

– includes all modes

– will include all data to Aug 2004

– J/ K by 18 Oct 2004

– lepton + D by 26 Oct 2004

– B hadronic by 8 Nov 2004

• Direct access to data (datlists)– Furic & Paus

– reports at BPAK

– available 1 Dec 2004

• Comments– must do better for Summer 05 &

beyond• need to start organizing this now

• volunteer (BPAK) needed

– for Winter 2004 success of datlists is critical

– B sntuple• no update of TOF possible

• event by event PV, L00 not included in present production

– 1 Oct 2004: Ch. Paus reports 30 pb-1 data bad due to CMX – use anyway?


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Signal Optimization

• Hadronic modes– Casarsa, Lucchesi, Squillacioti, Shapiro

– reports at B Hadronic

– complete by 4 Nov 2004

• Semileptonic modes– Gibson

– reports at Semileptonics

– update on 26 Oct 2004

– schedule for finalizing not established

Concern: inadequate personnel and coming too late


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Lifetimes

• Semileptonic– Clark, Farrington, Tanaka,

Ukegawa, Uozumi


– near term (by 4 Nov 2004)• Tanaka x-check of l + D+

• d0 cut on D* (D+, D0 too?)

• generate more c-cbar MC

• result in 8 GeV (no SVT)

– long term (no estimate)• have to see results of near term

to decide how to proceed

• Hadronic

• “MC free” approach– Azfar, Boudreau, Huffman,

Rademacher, Rahaman

– reports at B hadronic

– fitting test and refinement• Azfar, Rademacher

• B+! D0+ in progress

– stripping & ntuple production (data & MC)

• Azfar, Rahaman

• B+! D0+ done

• B0, Bs, &b modes in progress

• complete by 4 Nov 2004


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Lifetimes (continued)

• Hadronic “MC free” continued– Systematics

• alignment (Boudreau, Rahaman)

• SVT eff. (Azfar, Rademacher)

• background parameterization (Huffman, Rademacher)

• all in progress already for B+ mode – done by 4 Nov 2004

• others follow later

• Hadronic – SVT eff. method– Da Ronco, Donega, Giagu,

Giolo, Lucchesi

– update SVT curves by

4 Nov 2004

– preliminary result (lifetime okay or not okay) by 22 Nov 2004


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Opposite Side Flavor Tags

• Validation of blessed Summer 2004 SLT(), SLT(e), JQT– Giurgiu, Kravchenko


– means putting taggers in repository & verifying we get the same results

– complete by 19 Oct 2004

• Creation of simple combination of above tags– Giurgiu, Kravchenko


– determine tag overlaps and combined D2 (including binning) on J/K • report on 19 Oct 2004

– evaluation of more sophisticated combinations (max D, diff. classes)• time scale not established


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Same Side (Kaon) Tag

• Further development of SS(K)T– Bedeschi, Catastini, Punzi, Scuri, Squillacioti– reports to Semileptonics– compare SS(K)T algorithms in data & MC using J/ K samples

• use combined dE/dx & TOF particle ID• report by 4 Nov 2004

• Study particle species produced around B+, B0, B0s

– Heijboer, Jones, Kroll, Usynin– reports to Semileptonics– Measure particle species in data

• initial report using private TOF calibration in July 2004• further progress requires updated TOF calibration and B Sntuples

– MC production in parallel – estimate Dec 2004


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Same Side Kaon Tag (continued)

• Comparison MC & data, tuning fragmentation– Ben-Haim, Maksimovic, Pursley

– reports to Monte Carlo & Semileptonics

– update on 4 Nov 2004

• B** – Ben-Haim, Maksimovic, Pursley

– reports to J/ & B hadronics

– signal in B+! J/ K+ (update 4 Nov 2004)

– signal in SVT hadronic samples (December?)


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Likelihood Fitting for md

• MIT/Cantabria/Karlsruhe– Belloni, Gomez-Ceballos,

Kravchenko, Leonardo, Paus, Piedra

– reports to Semileptonics

– likelihood fit B!J/ K with SST exists – see last workshop

– need to add OSTs

– developing fits for l + D &

D, D3– Fully tested with preliminary

result on md by 1 Dec 2004

• Argonne/CMU– Giurgiu, Paulini, Tanaka

– reports to Semileptonics

– full likelihood for ms exists; used for ICHEP 04 projections

– developing for md w l + D incorporating blessed OSTs

• 1st version fit working and tested on toy MC – see last workshop

• working on including tagging & vertexing in data ntuple – report at 4 Nov 2004

• run on MC to determine add. K factors: 30 Nov 2004

• 1st result on md by 7 Dec 2004


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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.


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In Preparation for ms

• Decision on blinding procedure– Punzi

– reports to B meeting

– written proposal submitted to B group before 4 Nov 2004

– present at workshop on 4 Nov 2004, sign off at following B meeting

• Quantities for input to likelihood fit (flat file content)– Kravchenko & Tanaka

– reports to semileptonics

– written proposal submitted to B group before 4 Nov 2004

– present at workshop on 4 Nov 2004


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Common Tools

• dE/dx in COT– COT dE/dx group (Giagu)

– reports to BPAK group

– validation of entire data set up to Aug 2004 shutdown in progress

– ready for 5.3.4 release on 29 Oct 2004

• TOF– TOF group (Snider)

– reports to BPAK group

– in process of revising/validating calibration schemes

– hope to be ready for 5.3.4 release on 29 Oct 2004


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Common Tools (continued)

• Combined dE/dx & TOF PID– Ciocci, Morello, Punzi, Squillacioti,

Tonelli

– reports to BPAK

– available now in private version: resolution functions for each particle type separately for dE/dx & TOF

– include in public code infrastructure by 18 Oct 2004 – validate

– include in 5.3.4 release on 29 Oct 2004

– include combination of TOF and dE/dx for 29 Oct 2004 release

– demonstrate utility with examples by 4 Nov 2004

• Event by Event Vertexing incl. L00– Cerri, Lucchesi, Shapiro

– reports to BPAK

– code available & will be in 5.3.4 rel.

– documentation by 4 Nov 2004


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Monte Carlo Production

• Oversight of Monte Carlo Generation/Production– D’Auria

– reports to Monte Carlo

– outstanding issues• existing MC samples produced by various groups privately not registered

• only aware of one collaborative effort to generate MC for semileptonics– see talk by Usynin at semileptonics subgroup on 28 Sep 2004


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Some Concluding Remarks

• We have made progress assigning tasks and making a schedule

• The schedule needs to be studied further to see if we are on target to have a result for Winter 2005

• Particular concern is Dec 2004 – how do we go from 1st results on md to documented blessed results by early Jan 2005?

• Two more workshops planned in 2004– November 3 & 4

• off week – we thought it would help to spread the pain over 2 days

– December 16


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Calendar

on week

proposedB mixingworkshop

Collaborationmeeting

last Thursdaymeeting

Gasp! now we are here!

La Thuile begins here

holiday

Better get back to work

Documents

Status of B s Mixing at CDF