Recent CDF Results on Bs Flavor Oscillations

The CDF Bs Mixing Group

CDF Executive Board Meeting

13 April 2006

J. Kroll (Penn), F. Bedeschi(INFN – Pisa), M. Herndon (Wisconsin), Ch. Paus (MIT), K. Pitts (Illinois)

The CDF Bs Mixing Group

80 people, 27 InstitutionsBig effort with many separateimportant contributions

Made Possible By the CDF Detector

• Trigger– high bandwidth & tremendous flexibility

– XFT and SVT

• Exquisite charged particle tracking– excellent pattern recognition & mass resolution (COT, solenoid)

– precise production & decay point reconstruction (L00, SVX)

• Particle identification– Time of Flight (TOF) and dE/dx in COT

• Extremely dedicated collaborators for operations– a lot of sleepless nights for analysis but many more for operations

– many of the analyzers spent sleepless nights working on critical detector components too

Sequence of CDF Run II Results on Bs Mixing

• Fall 2001: 1st heavy flavor signal from TTT data

• Summer 2002: 1st lifetime measurements

• Winter 2003: 1st fully reconstructed Bs! Ds

• Summer 2003: 1st blessed opposite side flavor tag (muon)

• Summer 2004: 1st B0 md result

A lot of ideas and development in Run I

Sequence of CDF Run II Results on Bs Mixing

• 1st result March 2005 – presented at Moriond QCD– hadronic modes from two-track trigger

– semileptonic modes from lepton + SVT trigger

– opposite-side flavor tags: muons, electrons, jet-charge

– combined sensitivity ms > 8.4 ps-1

• 1st update: October 2005 – presented at PANIC 2005– substantial increase in semileptonic signal from TTT

– several analysis improvements, e.g., • neural net based jet-charge opposite side flavor tag

• improved opposite side flavor tag calibration

• improved boost resolution on semileptonic decays

– combined sensitivity ms > 13.0 ps-1

These results based on 360 pb-1 (0d data)

Current CDF Bs Oscillations Analysis

• This winter our focus shifted to three main areas– adding same-side kaon tagging (SSKT)

• blessed on 23 February 2006

– adding 0h and 0i data (an additional 640pb-1) (done – see later)

– using partially reconstructed hadronic decays (still in progress)

• 1st step – add SSKT to 360pb-1 hadronic analysis– Schedule had us unblinding on 13 March 2006

– DØ announcement at Moriond EWK on 12 March 2006

– CDF unblinded hadronic scan on 13 March 2006 as foreseen

– found ~3 excess @ ms = 17.3 ps-1

– 0d hadronic-only result already much more significant than DØ

– preblessed at B meeting on 16 March 2006

– decided to add 0h & 0i data asap for both hadronics & semileptonics

DØ Result reminder: oscillation probability

Amplitude peaks @ ms = 19ps-1

2.5 discrepant with A=0 (1%)

17 < ms < 21 ps-1 @ 90% CL

10% compatible with A=1

Probability that randomfluctuation produces this signalp-value = (5.0 § 0.3)%

Presented at Moriond EWK on 3/12/06

CDF Hadronic Data (355pb-1)We were on schedule to unblind 1st part of hadronic data on 3/13/06

This result was comparable in sensitivity to DØ result

We had a lot more data, so we decided to add it, and fast

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Rapid Progress from 3/13 to 3/31

• This was a well-tuned analysis & extensively reviewed– Winter 2005 had two independent semileptonic analyses

• included independent fits and data sets, which were fed to each other• direct comparison of amplitude scans

– also independent lifetime measurement in Bs! Ds• Emphasis on adding new data was validation

– signal invariant mass distributions– signal lifetime distributions– particle identification (TOF and dE/dx)– proper time resolution

• Had to understand how to move from limit to measurement– required evaluation of probability of background fluctuation– determination of ms including systematic uncertainties

• Unblinded amplitude scans after B meeting on 3/30/06– presented at Joint Physics Meeting on 3/31/2006

Result: Amplitude Scans in 1 fb-1

Hadronic Decays Semileptonic Decays

Single experiment sensitivity > combination of previous results

Result: -ln(likelihood) & ms, |Vtd/Vts|

A = 1.01 § 0.29 (3.5)

p value: 0.5%

Limited by theoretical(lattice) uncertainties

Impact on CKM Unitarity Triangle

EPS05 EPS05 + CDF

Figures courtesy of Z. Ligeti (LBNL)

Since Blessing on 6 April 2006

• Special Wine & Cheese on Monday 10 April 2006– 3 rehersals: Friday & Sunday afternoon, Monday morning

– 1 West was standing room only

– spectacular performance by speaker Ivan Furic

• FNAL press release on Tuesday 11 April 2006

• 1st Conference presentation at FPCP 2006, Vancouver, BC– CDF contingent flew Monday night

– Rehersal in hotel room Tuesday morning

– Excellent presentation by Guillelmo Gomez Ceballos• Received with great enthusiasm by Flavor community

• Several requests for seminars from National Labs– ANL, BNL, DESY, LBNL, SLAC …

Public Documentation

• PRL in preparation– 1st draft: Ch. Paus, JK

– Godparents: Ristori (Chair), Glenzinski, Wuerthwein

– Heinrich, Punzi are statistics committee consultants

– plan for accelerated review process

• Public Document (CDFNOTE 8204)– K. Pitts editor, many contributors

– circulating in collaboration now – please read and send comments

– would hope to make public by next week

– could serve as PRD draft

• Web page– link on main CDF public page to main plots & talks

– http://www-cdf.fnal.gov/physics/new/bottom/060406.blessed-Bsmix/

What’s Next?

• Analysis improvements (all already well underway)– add satellite peaks (Ds

*, Ds) in hadronic modes

– neural networks for hadronic signal selection

– use all semileptonic trigger paths (lepton + SVT, SUSY dilepton)

– neural networks for opposite side tags

– improve SSKT by combining kinematics and particle id

– use particle id in signal selection (Ds! K*K)

• Technical improvements– reprocess all data offline version 6

at least 1st 360 pb-1

– improvements to fitter implementation• e.g., replace ascii input file with ntuple

• Related physics results (e.g., lifetimes)

Goal: 5 observation for ICHEP 2006