# Presentation: 273309

## B PHYSICS AT THE TEVATRONKAREN GIBSON, UNIVERSITY OF PITTSBURGH 

- Split, Croatia 	    Physics @ the LHC	October 3, 2008

## B Physics Program at Tevatron Has Been Tremendously Successful!

- Complements excellent programs at B-factories
- Many unique measurements made at Tevatron
- Observation of Bs mixing, b-baryons
- CPV in Bs  J/
- Several measurements (*e.g.* lifetimes, direct CPV) in B0/B+ systems are approaching sensitivity of BABAR/Belle

## A Special Time for TeV(atron)

- Tevatron can contribute uniquely to B physics for the next few years
- Transition between first run of B factories, LHC experiments
- At advent of LHC era, consider Tevatron B physics program present and future
- Highlight recent results (from 2008)
- Anticipate results to come
- 2-4x the statistics can be added to many existing measurements before the end of Run II!

## CDF and D0 Detectors Have Different Strengths in Detecting B Hadrons

- Excellent calorimetry, muon id, can reverse direction of B field
-  Large sample of semi-leptonic decays, forward decays, good direct CPV meas.

- Strong tracking system, ability to trigger on displaced tracks
-  Good mass resolution, high statistics in non-leptonic decays

## Three Main Categories of B Physics Results Discussed Today

- Production
- Birth of B hadrons
- Lifetimes
- Death of B hadrons
- CP Violation
- The curious things in between

- B(s) will be discussed in context of SUSY,
- see Tuesday’s talk by D. Toback for details

## Production

**MICHELANGELO Buonarroti**Creation of Adamc. 1510

## Searching for New Particles

- Look for things that we think should be there and also for things that shouldn’t
- Can find some surprises
*e.g.*  X, Y, Z particles
- Many b-baryons have not been observed until Run II!
- Observed b (2006), b (2007) and recently b (2008)

## Investigate Properties of X(3872)

- First observed by Belle collaboration in 2003
- Observed in decay X(3872)  J/
- Nature of particle is still unknown
- D*D “molecule”? 4-quark state?
- Search for mass splitting, measure absolute mass
- Observation of mass splitting offers evidence of tetra-quark
- No mass splitting makes absolute mass interesting
- Checks possibility of bound-state D*D

**www-cdf.fnal.gov/physics/new/bottom/080724.blessed-X-Mass/**

## No Mass Splitting Observed in X(3872)

- Fit mass with Breit-Wigner convolved with resolution
- Result consistent with no mass splitting
- Assign upper limit CL

- m(X(3872)) < 3.2 (3.6) MeV/c2 at 90% (95%) C.L.

## Most Precise Measurement ofX(3872) Mass

- m(X(3872)) = 3871.61 +- 0.16 (stat) +- 0.19 (syst) MeV/c2

- Measured mass is below D*D threshold, although uncertainties are within threshold
-  D*D bound state is still a possibility

## First Observation of b Baryon

- Announced by D0 on Aug. 29, 2008
- Observation made with 1.3 fb-1 of data
- Builds on previous observation of b

**arXiv:0808.4142, submitted to PRL**

## Previous Observation of b

- In 2007, both CDF and D0 observed the b and made a precise determination of its mass
- bJ/], p

##  Reconstruction Improved with Special Selection Techniques

- Use boosted decision tree (BDT) to improve identification of  signal

- Before BDT

- After BDT

- Veto
- 0

- Re-process data with higher IP req. to increase / acceptance!

## Observe Significant bSignal

- Observe 17.8 ± 4.9 (stat) ± 0.8 (syst) events
- m = 6.165 ± 0.010(stat) ± 0.013 (syst) GeV/c2

- Calculate signal significance to be 5.4

- Expect 5.946.12GeV/c2 from theory

## Lifetimes

**CARAVAGGIO**
- Judith Beheading Holofernes
- c. 1598

## Why Measure Lifetimes?

- Test HQET predictions
- Have previously seen1-2 discrepancies between  lifetime predictions and measurements in Bs0, b0
- Expect (B+) > (B0)  (Bs0)  > (b0) » (Bc+)
- Because they’re there?
- Fundamental quantity, give complete picture of B’s
- Useful for other measurements (e.g. b-tagging)

- HFAG 2006

## Bs0Lifetime Now Agrees with HQET  

- Blinded measurement of lifetime in 1.3 fb-1 of data
- Data collected with displaced track trigger
- 	 must correct for trigger bias (use Monte Carlo)

- c(Bs0) = 455 ± 12 (stat.) ±  7 (syst.) m

- Very compatible with HQET predictions that c(B0)  c(Bs0)
- (c(B0)  = 458.7 ± 2.7, PDG 2008)

- Partially reco. decays double statistics!

**www-cdf.fnal.gov/physics/new/bottom/080207.blessed-bs-lifetime/**

## Bc Lifetime Agrees with Theoretical Predictions 

- Simultaneously fit mass and lifetime

- c(Bc) = 134.3  11 (stat)  10 (syst) m

**arXiv:0805.2614,**
**submitted to PRL**

## Bc Lifetime Agrees with TheoreticalPredictions and D0 

- Fit e,  channels separately, combine L afterwards

- c(Bc) = 142  15 (stat)  6 (syst) m

**www-cdf.fnal.gov/physics/new/bottom/080327.blessed-BC_LT_SemiLeptonic/**

## b0 Lifetime Question Closer to Resolution  

- Measure lifetime in displaced track sample
- First fit mass, then lifetime

**www-cdf.fnal.gov/physics/new/bottom/080703.blessed-lblcpi-ct/**

## New Measurements Are in Good Agreement with Predicted Lifetimes

- New measurements of lifetime are in good agreement with theoretical predictions!

- WA

## New Technique Used to Measure B Lifetime 

- Measured in displaced track sample
- Novel method for correcting for trigger bias without using Monte Carlo

- c(B+) = 498.2 ± 6.8 (stat.) ±  4.5 (syst.) m,
- (c(B+) = 491.1 ± 3.3 m, PDG 2008)

- Use acceptance function to correct for trigger bias on event-by-event basis

**www-cdf.fnal.gov/physics/new/bottom/080612.blessed-MCfree_Blifetime/**

## CP Violation

**HOLBEIN, Hans the Elder**The Martyrdom of Saint Sebastianc. 1516

## Three Types of CP Violation

- Decay of hadrons (direct CPV)
- Only type of CPV for charged mesons
- Mixing of neutral mesons (indirect CPV)
- Semi-leptonic decays of neutral meson
- Interference between mixing and decay
- B0  J/ Ks0  sin2
- Bs0  J/  sin2s

- Use flavor tagging for more powerful measurement of CP phases!

## CPV Phases in Bs0 Sensitive to New Physics

- CPV in Bs0J/ gives access to phase, sensitive to NP

- ms = mH – mL   2|M12|
-   =  L  H  2|12|cos(s),
- where s= arg(M12/12) ~0.004 in SM

- SM prediction

- Measured at Tevatron in 2006!

- Mixing governed by Schrodinger eqn.

## Discrepancy with SM Remains in CDF’s Flavor-Tagged BsJ/ 

- Recent update finds 1.8 (p-value = 7%) discrepancy with SM prediction for s J/
- Expect further improvement in statistical precision shortly!

**1.5******** discrepancy **
**w/SM**

**www-cdf.fnal.gov/physics/new/bottom/080724.blessed-tagged_BsJPsiPhi_update_prelim/**

## Similar Discrepancy Observed byD0 in Flavor-Tagged BsJ/ 

- D0 result very similar to CDF’s!
- Discrepancy w/SM is 1.7, p-value = 0.085

- Trend is identical,
- s J/  2s

- D0 finds agreement in strong phase || between BsJ/ (assuming
- sJ/ = 0) and BJ/ K*0
-  Use phases in BJ/ K*0 to choose one of two solutions?

**arXiv:0808.1297v1**

## More Significant Discrepancy in Combined BsJ/ Result

- See G. Giurgiu’s talk in Friday parallel session for details!

- New CDF result not included in combination!

**arXiv:0808.1297v1**

- G. Hou et al suggest that discrepancy might be due to t’ quark w/mass
- ~300 GeV/c2 – 1 TeV/c2

## Most Precise Measurement of Bs0 Semileptonic Asymmetry  

- New flavor-tagged measurement of Bs0 semileptonic asymmetry, assl
- BsDsX [] X
- Depends on lifetime, , ms, and assl

**Previous, untagged measurement **
**a****s****sl**** = 0.0245 ******** 0.0193 (stat) ******** 0.0035 (syst)**

- Most precise measurement to date!

**www-d0.fnal.gov/Run2Physics/WWW/results/prelim/B/B55/**

## / Measured in BsD(*)sD(*)s Consistent with World Average

- Measure branching ratio to determine 2.8 fb-1
- Search for one Ds, other to Ds 

- Assuming SM, s= 0, CP = 

- Find

**Consistent with WA (2007) ********/********=**
**0.096 ****+ 0.048 ****-0.053**

**www-d0.fnal.gov/Run2Physics/WWW/results/prelim/B/B53/**

- Under certain theoretical assumptions, BsD(*)sD(*)s  is nearly CP even

## New Measurement of Direct CPV in BJ/K() 

- SM predicts ACP(BJ/K) ~ 0.003
- NP might produce asymmetries up to ~0.01

- ACP(BJ/K)  = +0.0075  0.0061 (stat)  0.0027 (syst)
- ACP(BJ/)  = 0.09  0.08 (stat)  0.03 (syst)

- PRL **100**, 211802 (2008)

## Looking to the Future

**MCGUINNESS, Ryan**The Need to Know
- 2008

## Many Interesting New and Updated Measurements to Come!

- Updates to CPV measurements
- Expect 2-4x higher yield depending on measurement
- More flavor-tagged CPV results
- Updated lifetimes with higher statistics
- Updated BJ/X lifetimes with 2x more data
- Will give most precise B+, b0 lifetimes to date
- New lifetime measurements with novel techniques
- BsDs lifetime measured with MC-free method
- Observation of new states?

## Valuable Contributions to Study of B Hadrons Made at Tevatron

- Exciting time for B physics at the Tevatron!
- Many significant contributions to knowledge of B hadrons has been made
- Expect many interesting, important updates in the next couple of years!
- Look forward to contributions to field from LHC experiments!

## Back-up

## Selection of X(3872)

- Use ANN to select events
- Optimize selection on Monte Carlo (signal) and mass sidebands (background)

## Mass Splitting of X(3872)

- Model resolution with Monte Carlo simulation
- Width scale floats freely in fit

## Cross-Checks of b Signal (1)

- Check WS events and mass sidebands for spurious excesses
- None observed!

## Cross-Checks of b Signal (2)

- Check lifetime distribution of b candidate events
- Consistent with B hadron lifetime

## Cut-based Analysis of b 

- Alternatively, try using simpler cut-based analysis
- Find 15.7 ± 5.3 (stat) events
- m = 6.177 ± 0.015 GeV/c2
- Signal significance is 3.9

## b Significance Calculation 

- Evaluate significance from likelihood ratio of background only hypothesis  (LB) to signal + background hypothesis (LS+B)

## Bs0Mass Fit in Lifetime Measurement

- Perform simultaneous unbinned maximum likelihood fit to mass and lifetime
- Use partially reconstucted decays to double statistics
- e.g. Bs0Ds0)
- ~2200 Bs0 candidates

## Comparison of Bs0Lifetime with Prev. Results

- Bs0 lifetime is higher than recently measured Bs0 lifetimes in flavor-specific decay modes
- Expect 50% of L, H in flavor-specific modes

## Measurement of BcJ/eX Lifetime 

- Fit lifetime only, use mass as cross-check
- Determine all background shapes and normalizations from data if possible, MC otherwise  constrain in fit

- c(Bc J/eX ) = 122   (stat) m

## Measurement of BcJ/X Lifetime 

- Fit lifetime only, use mass as cross-check
- Determine all background shapes and normalizations from data if possible, MC otherwise  constrain in fit

- c(Bc J/X ) = 179 33 27 (stat) m

## Combination of Semilep. BcLifetimes 

- Combine -2lnLe, -2lnL

## Unitarity Relations in B0/Bs0 

- s

## Mixing and Decay in Bs0  

- 	Mixing between particle and anti-particle occurs through the loop processes

- Oscillations are very fast-
- ~3 trillion times per second!

- New particles can contribute to box diagram!

## New Physics in Bs0 Decays

- Bs0 Bs0 oscillations observed by CDF
- Mixing frequency ∆ms now very well-measured
- Precisely determines |M12| - in good agreement w/SM pred.
- Phase of mixing amplitude is still very poorly determined!

- New physics could produce large CP phase!

-  M12 = |M12|eim, where m = arg( VtbVts*)2