# Presentation: 944516

## Heavy flavour @ TevatronStatus and prospects

- Flavour in the era of the LHC
- March 2007

- Jónatan Piedra
- MIT

- Heavy flavour @ TevatronStatus and prospects

## Outline

- The Tevatron Collider
- The D and CDF II Detectors
*B**s* Mixing
***s** and ****s*
*B **** hh’*
*B **** ***
***b* *** J/**** *** Lifetime
- Observation of ***b*
- Prospects

## The Tevatron Collider

- pp*bar* collisions at 1.96 TeV
- 2 fb–1 data on tape
- Peak luminosity 2.9 x 1032 cm–2s–1
- Average 6 pp*bar* interactions per bunch crossing
- Anticipate luminosity as high as 3 x 1032 cm–2s–1
*** **challenge for detectors, trigger and reconstruction*

## The D and CDF II Detectors

- The D and CDF II Detectors

- CDF II
-  strong central tracking
-  silicon vertex detector and trigger
-  particle ID (TOF and dE/dx)
-  excellent mass resolution
- D
-  excellent coverage of tracking and muon systems
-  excellent calorimetry and electron ID
-  2 T solenoid, polarity reversed weekly
-  April 2006 Layer 0 installation

## Bs Mixing Neutral B Meson Oscillations

- Oscillation frequencies ***m**d* and ***m**s* determine poorly known *V**td* and *V**ts*
- Theoretical uncertainties reduced in ratio, *11% **** 3%*

*B**s** Mixing* Neutral *B* Meson Oscillations

*WEAK (FLAVOR)*
*EIGENSTATES*

*STRONG (MASS)*
*EIGENSTATES*

**Notes:**
Vij are fundamental parameters that must be measured

## Bs Mixing Signal

- Cleanest topology
- Includes partially reconstructed decays
- Total signal
- 8,800 fully reconstructed decays
- 61,500 semileptonic decays

**Notes:**
Partially reconstructed decays: missing gamma or pi0
Superior decay time resolution gives CDF sensitivity at much larger values of Dms than previous experiments

## Bs Mixing Results

*B**s** Mixing* Results

- Probability that a random fluctuation mimics signal = 8 x 10-8  5.4

**Notes:**
Sensitivity = 31.3 ps-1
A/sigma(A) = 6.1

## s and s Motivation

*L*ight and *H*eavy *B**s* mass eigenstates
***m**s** **** M**H** – M**L*
*** **** ****L** – ****H*
- The mass eigenstates are expected to be almost pure CP eigenstates
- The CP violating mixing phase is predicted to be
***s* = (4.2  1.4) x 10-2
*A.Lenz & U.Nierste, hep-ph/0612167*
- New Physics may alter ***s* leading to a reduction of the observed ** s
** s = ** sSM x |cos ***s*|

- J. Piedra

- March 28, 2007

## s and s Bs  J/ 

*1.1 fb**-1*
*B**s** **** J/**** ***
*	** **J/**** **** *********
*	**** **** **K****K***
- Fit time dependent angular distributions, mass and lifetime
- direct constraint on ***s*
- 4-fold ambiguity, ***s* and (***s*)
*the sign of sin****s** is reversed with the simultaneous reversal of the signs of the cosines of the CP-conserving strong phases ****1** and ****2*

*consistent with the SM prediction*

- J. Piedra

- March 28, 2007

## s and s Flavor Specific Decays

- Flavor specific decays of *B**s* provide independent constraints
- An effective mean lifetime ***fs **= 1/****fs* is related to the physical parameters
- 	*hep-ph/0201071, p.360*
- Use world average value ***fs* = 1.440  0.036 ps
- includes recent D measurement

- J. Piedra

- March 28, 2007

## s and s Charge Asymmetry

- Another constraint on the parameters of the *B**s* system
- Measurement of the semileptonic charge asymmetry induced by *B**s* mixing
- Measurement “*a”*
- Measurement “*b”*
*“**a”* and *“b”** *are nearly independent (correlation < 1%)
- Combination  best estimate of charge asymmetry in semileptonic *B**s*

**input from *****B*****-factories**

**Notes:**
Dms/Gs >> 1

## s and s Results

- Repeat fit to *B**s** **** J/**** *** (1 fb-1) with
- constraint from charge asymmetry
- constraint from WA ***fs*
- The contours indicate error ellipses ***ln(**L**) = 0.5* (39% CL)

***s* ambiguity remains unsolved
- For the solution with
*	****s* < 0, cos ***1* > 0 and cos ***2* < 0

***s* tan***s* = 0.02 ps-1

## B  hh’ Motivation

- The Tevatron has access to *B**s*, *B**0* and baryons
- physics program complementary to the *e****e*** *B-*factories
- Currently accesible BR can constrain theory
- compare measurements with allowed regions in spaces of *B**0** **** ********* and *B**s** **** K****K*** observables
- probe for New Physics

- J. Piedra

- March 28, 2007

## B  hh’ Strategy

- Two sets of optimized cuts
- (loose) to measure *A**CP**(B**0** **** K********)*
- (tight) to observe *B**s** **** K******* and measure *N(B**s** **** K********) / N(B**0** **** K********)*

- Despite excellent mass resolution (23 MeV/c) modes overlap in a peak
- PID resolution is insufficient for event-by-event separation
- Fit signal composition with a likelihood that combines information from kinematics (mass and momenta) and particle ID (dE/dx)

- J. Piedra

- March 28, 2007

## B  hh’ BR Results

- Measured
- Using HFAG 2006 averaged values

*BR(B**0 **→ **********)* in agreement
- 	with *B*-factories measurement

## B  hh’ Rare Modes

*B **** hh’* Rare Modes

- Signal = 6 modes combination
*B**0 **** ********−****K**+****−* and *B**s **** K**+**K**−** *already established
- Set limits on annihilation modes
*B**s **** ********−****and **B**0 **** K****K**−*
- 3 new rare modes observed

## B  hh’ Direct CP Asymmetry 

- “Is observed direct CP violation in *B**0 **** K******** *due to NP?
- 	Check SM prediction of equal violation in *B**s** **** K*******”
*Lipkin, Phys. Lett. B621:126 (2005)*
*Gronau & Rosner Phys.Rev. D71 074019 (2005)*
- Expect large *A**CP**(B**s **** K********)*  0.37
- Sign opposite to *A**CP**(B**0 **** K********)*

- First measurement of CP asymmetry in the *B**s*  system

**Notes:**
plot: L(Bs) / [L(Bs) + L(Bsbar)]
Direct CP asymmetry measurement for Lb modes in progress

## B   Motivation and Strategy

- Standard Model prediction very suppressed
- Sizeable New Physics enhancement predicted in many scenarios
- Blind optimization using signal Monte Carlo and sideband data
- Normalize to known *B**+** **** J/**** K**+*
- Reconstruct normalization mode in the same data, applying same criteria
- Evaluate expected background, open the box and calculate *BR* or limit

## B   Signal Discrimination

*M**B* ± 2.5 (~120 MeV) mass window

- vertex displacement *** = LM**B** / p**B*

- fraction of *p**T**(B)* within ***R* = 1

-  angle between *p**B* and decay axis

## B   Results

- 780 pb-1 CDF *B**s* limit
-  BR(*B**s **** ***) < 8 (10) x 10-8 @ 90% (95%) C.L.
*CDF update coming soon (sensitivity x2)*
- 2 fb-1 DØ *B**s* limit
-  BR(*B**s **** ***) < 7.5 (9.3) x 10-8 @ 90% (95%) C.L.
- 780 pb-1 CDF *B**0* limit, world’s best
-  BR(*B**0** **** ***) < 2.3 (3.0) x 10-8 @ 90% (95%) C.L.

- 110 fb-1 BaBar *hep-ex/0408096*
- BR(*B**0** *** **) < 8.3 x 10-8 @ 90%  C.L.

## b  J/  Lifetime Results

- CDF and D**** have measured ***b** **** J/**** *** lifetime
- Smaller boost uncertainty than ***b** **** ****c** l*** *(world average dominated)*
- Earlier ***(****b**)/****(B**0**)* ~ 0.94 predictions were 2 above experiment
- new calculations including higher order effects predict lower ratio

|  | CDF 1.0 fb-1 | D 1.2 fb-1 |
| --- | --- | --- |
| signal | 538  38 | 174  21 |
| (b) [ps] |  |  |

**Notes:**
D0 selection: tight cuts to reject Jpsi Ks background

## b  J/  Lifetime Summary

- Current NLO QCD + 1/*m**b*4
- (***b*)/(*B*0) = 0.86 ± 0.05
- HFAG 2005 world average
- (***b*)/(*B*0) = 0.803 ± 0.047
- New CDF result
- 	about 3 above PDG 2006
- New D results
- 	consistent with PDG 2006 & CDF
- Need more experimental inputs
- Soon ***b** **** ****c**** ***** lifetime from CDF
- 	*yield ~ 3,000*

- J. Piedra

- March 28, 2007

## Observation of b

***b* (*udb*) only established *b*-baryon
- Next accessible baryons:
*	**uub* and *ddb* states
- Look at ***b** **** ****c **** *sample
- Signals consistent with lowest lying charged ***b* states

## Summary

- Very fast turn around of results at the Tevatron
- D already showing 2 fb-1 results
- Competitive and complementary program to *B*-factories
*B**s* mixing measured
***m**s* = 17.77  0.10 (stat.)  0.07 (syst.) ps-1
- First observation of
*B**s** **** K*******
***b** **** pK***
***b** **** p*****
- First measurement of direct CPV in *B**s*
*B **** *** limits ~10-8
- Observation of ***b*

## Prospects I

*B**s* mixing phase ***s* not constrained by ***m**s*
***s* and ***s* from
*B**s** **** J/**** ***
*B**s** **** K****K***
- flavor specific decays *B**s** **** D**s**l****, D**s***
- semileptonic charge asymmetry *A**SL*
- BR(*B**s** **** D**s**(*)** D**s**(*) *)
*ALL THESE MEASUREMENTS SHOULD CONVERGE*

## Prospects II

- Direct measurement of ***s*
- measure time dependent CP asymmetry in *B**s** **** J/**** ***
*A**CP**mix* from *B**s** **** J/**** **** *(*A**CP**mix, theory* = 0.07  0.50)
- CKM angle **  51o  20o
*D**0* mixing (evidence from Belle and BaBar)
*D**0* direct CP asymmetry
- Rare charm decays
*D**0** **** l****l’*** could be world’s best
*D****(s)** **** *** or *K***
- New *b*-baryon decay modes
- CDF looking at

## Backup

- J. Piedra

- March 28, 2007

## Bs Mixing Asymmetry

- J. Piedra

- March 28, 2007

## D0 Mixing Charm Mixing

- Mixing observed in *K**0*, *B**d* and *B**s*, but not yet in *D**0*
- Charm mixing is slower than *B* or *K* mixing
- Use *D* **** D**0** ****+* to tag the original flavor as *D**0* or *anti-D**0*
*D**0** **** K**-** ****+*, Cabibbo Favored (CF)
*D**0** **** K**+** ****-*, Doubly Cabibbo Suppressed (DCS)

- J. Piedra

- March 28, 2007

## D0 Mixing Belle and BaBar

- Reminder
*y** = **** / 2***
*x** = ****m / ***
*y’** = **y**cos**** – **x**sin***
** = strong phase difference between CF and DCS amplitudes
- mixing parameter *y**CP** = ****(D**0** **** K**-****+**) / ****(D**0** **** K**+**K**-**)*
- in CP conservation limit *y**CP* = *y*
- Belle
*	**hep-ex/0703036*
- 540 fb-1
*y**CP* = 1.31 ± 0.32 (stat) ± 0.25 (syst) %
- more than 3 above zero
- BaBar
*	**hep-ex/0703020*
- 384 fb-1
*y’* = 0.97 ± 0.44 (stat) ± 0.31 (syst) %
- 3.9 deviation from zero
- Evidence for *D**0* mixing