# Presentation: 683936

## Prospects in CP violation measurements at the Tevatron (collider experiments only)

- XVIIiémes Rencontres de Physique de la Vallée d’Aoste
- February 29th  – March 6th, 2004 - La Thuile
_*Diego Tonelli*_
***tonel@fnal.gov***
- Scuola Normale Superiore and INFN – Pisa
- for the CDFII and DØ Collaborations

## The Tevatron pp collider

- The Tevatron *pp* collider

- Superconducting proton-synchrotron: 36 *p*  36 *p* bunches
-                                                              collision every 396 ns at √s = 1.96 TeV
- Luminosity..................................: record peak is  6.7  1031 cm-2 s-1
-                                                               ~ 10 pb-1 / week delivered
- # interactions / bunch-crossing........: < N >poisson  = 1.5  (at 5** ******** 10****31 ****cm****-2****s****-1**)
- Luminous region size....................: 30 cm (beam axis)   30 m (transverse)
-                                                                           **need long Si-vertex****     ****small wrt c********(B) ~ 450 ********m **

**6 ******** 10****31 ****cm****-2****s****-1**

**Improved ****> 2******** during  last year**

## Delivered Luminosity 

- Data taking efficiency: 80 - 90% stable for  both experiments

- ~ 290 pb-1 on tape per experiment

- For the following results:             CDF analyses use: ~65 to  ~190 pb-1 DØ analyses use:  ~ 47 to  ~114 pb-1

## Heavy Flavor physics at the Tevatron

*bb* production x-section  O(105) larger than e+e-  at (4S) /Z0. Incoherent strong production of all *b*-hadrons:  B, B0, Bs, Bc, b, b .
- The Bad
- Total inelastic x-section ~ 103    (*bb*).                    BRs’ for interesting processes O(10-6).
-                      ...and The Ugly
- Messy environments with large combinatorics.

- Need highly selective trigger

## Triggering bs’ (and cs’)

- Triggering* b*s’ (and *c*s’)

- _Di-lepton_
- CDF and DØ
- B  charmonium  Rare  B  
- Two  muons with:
- pT> 1.5 GeV        ||< 1
- pT> 2.5-4.5 GeV  ||<2

- _electron or  ____  and displaced track_
- CDF only
- Semileptonic decays
- Electron  ()  with:
- pT> 4 (1.5) GeV     ||< 1
- and one track  with:
- pT > 2.0 GeV     IP > 120 m

- _Two displaced tracks_
- CDF only
- n-body hadronic B
- Two tracks with:
-  pT > 2.0 GeV
-  pT > 5.5 GeV
- IP > 120 (100) m

- _Single-muon_
- DØ only
- Semileptonic decays
- one muon with:
- pT > 2 - 4 GeV    || <2

- Displaced track trigger at Level 2:  a revolution in hadronic environment ! Accessible rare hadronic decays with high S/B. Soon DØ too.

***conventional***

***new approach***

## Detectors

-         Both detectors
- Silicon microvertex tracker
- Axial solenoid
- Central tracking
- High rate trigger/DAQ
- Calorimeters and muons

-                DØ
- Excellent electron and muon ID
- Excellent tracking acceptance
-                  CDF
- L2 trigger on displaced vertexes
- Particle ID (TOF and dE/dx)
- Excellent mass resolution

## Overall game plan

- CPV at Tevatron: mainly* b*-sector. Unique opportunity to study Bs physics. CDF explores also charm.

## B  h+h'- : towards ,  and direct ACP 

-  hypothesis

- Resolve the signal composition. Admixture of (at least):
- B0d ****    and Charge Conjugate
- B0d **** K+ - and C. C.
- B0s **** KK-  and C. C.
- B0s ****  K- + and C. C.
- pT > 2 GeV/c: TOF doesn’t help
- Combine kinematics with  dE/dx to achieve statistical separation

- Expect ~ 6500 evts / fb-1

## B  h+h'- : resolve peak composition

******/K ******** 1.16******** ****( improved soon ! )**

** ****M******** ****vs (1- p****min****/p****max****)Q****min**

- _Specific ionization_
- dE/dx calibrated on 78K D* decays.

- _Kinematics_
- Exploit correlation between mass, charge and momentum imbalance

**MC**

**MC**

**MC**

**MC**

**MC**

**MC**

## B  h+h'- results (only 65/pb)

**f****s****·****BR (B****s ******** KK) / f****d****·****BR (B****d ********K********) = 0.74 ****±**** 0.20 ****(stat)**** ****±**** 0.22 ****(syst)**
_**First evidence of B**__**s **__****__**K**__**+**__**K**__**-**__** decays.**_
** ****Direct A****CP****(B****d********K********)    = ****0.02 ± 0.15 ****(stat)**** ****± 0.02 ****(syst)**
- 15% statistical error,  systematic comparable with B-factories
** ****BR(B****d ************) / BR(B****d ********K********)   = ****0.26 ± 0.11 ****(stat)**** ± 0.06**** ****(syst)**
- Consistent with B-factories results.

- Measurement of the relative populations.  Not sensitive (yet) to  B0s ****  K- + .     Dominant systematic from dE/dx calibrations

## B  h+h'-   what’s next ? 

- Almost done: upgraded measurement on current ~200/pb: will be  competitive on direct **A****CP** and sensitive to  **B****s ******** K ********.**

- Longer time-scale: tagging + time dependent analysis measure  w/o penguin pollution as suggested in *(Fleischer and Matias: PR D66**9** (2002) 054009)  *

- Medium term: BRs’ alone could provide, with minimal dynamic assumptions, a measurement of      *(R. Fleischer  hep-ph/0306270)*

## B0s - B0s mixing

- Unique opportunity at Tevatron
-                  Key issues
-  B0s  flavor identification at decay
-  B0s  flavor identification at production
-  High Yield with good S/B.
-  High resolution on proper decay time

- B0s - B0s mixing

**...****additional difficulty wrt B****d**** **

## B0s - B0s mixing

- Was Bs   or Bs at the time of decay ?
- Triggering and reconstruction of  flavor-specific final states:
- high c resolution, low yield            Bs  Ds (  )  (Ds    [ KK ] )
- high yield & S/B, worse c resol.    Bs  Ds l  + X   (Ds    [ KK ] )
- Was Bs   or Bs at production ? charge-flavor correlations and *bb *production:

- Primary vertex

**Soft  lepton**

**Jet charge**

**opposite  Kaon**

- Bs

**b-hadron**

- c

**Flavor-tag side**

**Vertexing side**

**fragmentation  Kaon **

- +

- Ds-

## Significance of a B0s mixing measurement 

- Units of sigma

| D2    [%] |   CDF | DØ |
| --- | --- | --- |
| Soft muon | 0.7  0.1 | 1.6  1.1 |
| Soft electron | in progress | in progress |
| Jet charge | in progress | 3.3  1.7 |
| Same side  | 2.4  1.2 | 5.5  2.0 |
| Opp. side kaon |  in progress | N/A |
| Same side kaon |  in progress | N/A |

|  |   c  [ fs ] |
| --- | --- |
| CDF | 67   (50 exp. with LØØ) |
| DØ | 110 - 150 |

**vertexing  and  momentum resolution **

## Towards B0s  mixing – hadronic side

**Flavor-tag side**

- B0s D-s + [ -] +[[K+K-] -] +    and  charge conjugate

- Fully reconstructed CDF  “golden channel”, maximum proper time resolution: resolve fast oscillations.
- Low statistics: add soon Bs  Ds  and  Ds  K*K / KsK / 
- Reconstructed  the signal with        Yield / lumi = 0.7 pb   S/B ~ 2 measure BR(Bs Ds )

**D****s**

**D*****s****  ****and **** ****others**

## Towards B0s  mixing – semileptonic side

**Flavor-tag side**

- B0s  D-s l+ + X[-] l+ [[K+K-] -] l+ and C.C.
-                          high yield and clean but neutrino: poor c

- Yield / lumi ~ 31 pb just muons !

- Yield / lumi ~ 7.6 pb  & electrons

**D****s**

**D****+**

**D****+**

**D****s**

## Prospects on B0s - B0s mixing

**Flavor-tag side**

- CDF today
- Hadronic modes only. Performance:
- 1600 events/ fb-1      S/B ~ 2/1
- D2 ~ 4%                 ******c******** **= 67 fs
- 2 sensitivity ms=15/ps with 0.5 fb-1

- CDF slightly improved
- Hadronic modes only. Performance:
- 2000 events/ fb-1      S/B ~ 2/1
- D2 ~ 5% (K tagging)  ******c****** = 50 fs
- 5 for** **ms = 18/ps  with 1.7 fb-1
- 5 for** **ms = 24/ps  with 3.2 fb-1

- DØ projections
- Semileptonic only. Performance:
- Yield:  30K    +   4K events/ fb-1
- D2  :  ~ 10%   -  ~ 50%
- S/B ~ 1/3              ******c******** **= 150 fs
- 1.5 for** **ms = 15/ps  with 0.5 fb-1

## Run I aside:  CDF average time-integrated            mixing probability   (PRD69, 2004: 012002)

- Ratio R = LS/OS of like (LS) to opposite sign (OS) dileptons in ~100 pb-1  of double semileptonic decays of* bb*. 2-D fit of the impact parameter in samples of , e. If mixing occurs LS increases. R related to the average time-integrated mixing parameter :

- numerator:      only Bd and Bs denominator:     all b-hadrons

- CDF Run Ia + Run Ib new result:
- = 0.152  0.007(stat) 0.011(syst)
- World average (LEP): 0.118  0.005

- A probe for either mixing or fragmentation fractions

- Indication of discrepancy with world average, confirms early hints from  hadronic colliders ?
- UA1:     0.1570.020 0.032
- CDF Ia: 0.1310.0200.016

## B0s J/ : a probe for sin(2s)  

- Measurement of Vts weak phase
- Expected very small. Anomalous CPV phases if asymmetry observed. Both experiments.
- B  V V: CP parity of final state depends on the relative angular momentum. Need angular analysis. s too!

- Yield / lumi ~ 0.2 pb

- B0s J/    [+-] [K+K-]  and Charge Conjugate

- N(Bs) = 133  7

- CDF yield: 120  13 in 140 pb-1

## CPV in other B  PV and B  V V 

- searching  for  B  V V
- B0s     and c.c. (s too!)
- B0d    K*            and c.c.
- B0d    K0s                and c.c.
- ..and for baryons             (SM expects ~10% CPV)
- 0b                  and c.c.
- 0b   pK- / p -         and c.c.

**Expect ~ 200 events/fb****-1**** **

- Measure direct ACP  in B+  K+   [K+K-] K+   and C.C.

## Direct ACP in Cabibbo suppressed D0   

- Yield / lumi ~ 0.2 pb

- D0 K+K- / +- and C.C.
- SM expects  O(10-3) CPV in charm. Sensitive to non-SM CPV sources.
- Excellent purity through D* - tag:                D*  D0S (Q = 39 MeV)                  cut on M (D*) - M(D0)
-  - sign (S) tags D0 flavor
-  - eliminate reflection BCKG

- ACP (D0 KK) = 2.0  1.2 (stat)  0.6 (syst) %
**  ****PDG world average  = 0.5 ******** 1.6 %**
- ACP (D0  ) = 1.0  1.3 (stat)  0.6 (syst) %
**   ****PDG world average  = 2.1 ******** 2.6 %**

- Dominant syst. from detector asymmetries and BCKG subtraction

**D****0**** ********KK**

**D****0**** ******** ******

## B  D K (expected yields only)

**Flavor-tag side**

-     Extract  from Cabibbo suppressed B charmed decays:
-     B-D0 K- [K-+] K-   and  B-D0 K- [K+ -] K-  and C. C.
-     B0sD-s K+ [-] K+[[K+K-] -] K+      and C. C.

- Babar/Belle

- Bu    D: ~ 24K per fb-1      Bd  D K: ~ 2.2K per fb-1

- Bs    Ds: ~ 1.6K per fb-1 Bs    Ds K: ~ 130 per fb-1

## Summary and final remarks

**Flavor-tag side**

- Substantial Tevatron improvement during last year, and performance is steadily ramping.
- From masses / lifetimes  transition ongoing to “second generation” measurements: CDF and DØ ready for CPV studies. Deep understanding of tracking and of  most low-level tools
- CDF: already world-class charm physics, soon exciting CPV results on B  h+h'- . Less fast than expected but moving to attack  Bs mixing in hadronic decays, SM favorite region accessible by   the end of 2004                                                                       Many other channels in future B  V V, B  DK ....
- DØ: very high semileptonic yields, lot of progress on  flavor tagging. Preparing for Bs mixing in semileptonic decays.

## BACKUP SLIDES

**Flavor-tag side**

## Tevatron Collider collaborations

**Flavor-tag side**

## CDF Detector Upgrades

## D0 Detector Upgrades

*2.0 T magnetic   field*
*Lever arm 52 cm*

- 4 silicon layers+disks
- Suited to limited space
- 2.8 < r < 10 cm
- |η| ≤ 3.0, cosθ = 0.993

- Now! Sci-Fi tracks @ L1
- Next! Silicon track s@ L2
- 5000 / 1000 / 50 Hz

- 8 layer Sci-Fi tracker |η| ≤ 1.7
- 10 < r < 52 cm, 80k channels
- VLPC’s at 9K, 85% QE
- σ(hit) ~ 100 μm

- Pre-shower
- Particle id
- Energy

- Some resolutions:
- pT ~ (2.0  0.2 pT)%
- J/Ψ mass ~27 MeV
- EM E ~ 15%/√E
- Had E ~ 80%/√E
- d0 ~ 13+50/pT μm
- Primary vtx ~15 μm
- Secondary vtx:
- r-Φ ~ 40 μm
- r-z ~ 80 μm

- μ coverage to
- |η| ≤ 2.0
- 90% in phi

## BACKUP SLIDES

**Flavor-tag side**

## ..more semileptonic B0s

**Flavor-tag side**

- Yield 700 events/ fb-1

## ..more semileptonic B0s

**Flavor-tag side**

- Yield 700 events/ fb-1

## Two-body Charm-less B Decays: Physics Motivations

-  Bd ****  / K   accessible at B-factories too:
-   Branching ratios
-   Direct  ACP in Bd ****  K :      ACP = (N+ - N-) /(N+ + N-)
-   Direct + mixing  ACP in Bd ****  :
-           ACP (t) = ACP cos(md t) + ACP sin(md t)
-  Bs **** KK / K   _only at Tevatron__, __never observed:_
-   Branching ratios
-   Direct ACP in Bs ****  K :       ACP = (N+ - N-) /(N+ + N-)
-   Direct + mixing  ACP  in Bs **** KK :
-      ACP (t) = ACP cos(ms t) + ACP sin(ms t)

- mix

- dir

- dir

- mix

## Physics Motivations (II)

- The combination of Bd and Bs decays provides a promising way to extract CP-related physical parameters avoiding the “penguin pollution”. *(R. Fleischer PLB45**9** (1999) 306)*
- Assume U-spin symmetry (d  s), the  ACP  are function of the CKM angles  and  and of the amplitude ratio P/T (~ dei)   4 equation with 4 unknowns (, , d, ).                                        A combined fit of the 4 CP asymmetries measures ,   and P/T ratio.
- Above strategy need time-dependent analysis with tagged samples: long term goal

##  Statistical resolution on   ACP(Bd K)

- BaBar: 0.035

- Sensitive to th.  predictions

- Best measurement today by BaBar: 0.035
- CDF needs ~850 pb-1 to reach that accuracy.
- Theory* predicts:      ACP  [-13%, + 5%] with ~1500 pb-1  CDF gets sensitive to it.

- * Keum, Sanda hep-ph/0306004  Beneke, Neubert hep-ph/0308039

## Projections on time-dependent ACP on tagged samples 

- We do not have a resolution to extrapolate from.                Use the analytic expressions for the expected resolutions:
- Assume a _minimal improvement scenario_  with:

-  6.48 pb specific yield
-  + 25% in S/B
-     (wrt current S/B)
-  D2  = 5% (today is 4%)

-  Proper time resol. = 50 fs
-     (today is 67 fs)
-  Trigger lifetime cut = 0.5
-  xs = 30