# Presentation: 414580

## b Physics at the Tevatron part I: m and md,s

*b* Physics at the Tevatron part I: *m* and *m**d,s*

- Masses of *b*-hadrons,
- rare decays and
- oscillation measurements
- at CDF and D0

- Saverio D’Auria, University of Glasgow
- For the CDF and D0 collaborations

- XL Rencontres de Moriond EW

- 11/3/2005

## Introduction: CDF and D0 detectors

**CDF:**
**Excellent p****T**** resolution,**** **
**displaced track trigger **
**              ******** ****fully hadronic decay modes**
**Tracking: Silicon + Drift Chamber**
**dE/dx, ToF particle ID**

**D0:**
**Excellent muon trigger **
**Tracking coverage** || < 2
**Tracking: Silicon + SciFib****, **

- Tevatron performances: see G. Bernardi’s transparencies
- Great *b*-physics capabilities

- 11/3/2005

## |y| < 1 CDF submitted to PRD hep-ex/0412071 

**Trigger issues**

*b* Production cross section:

- Inelastic cross section:  60 mb factor 1/1000 trigger.
- Compare with *b*-factories:  is 103 higher,
- 			       L is pb (TeVatron) vs. fb (*Y*(4S))

|  | b | L cm s | Integrated L | b-events |
| --- | --- | --- | --- | --- |
| Tevatron | 29 | 1.2 10 | 600 pb 2 | 13.8 109 |
| KEK | 0.001 | 1.5210 | 371 fb | 0.37 109 |
| BaBar | 0.001 | 0.9510 | 256 fb | 0.25 109 |

- CDF, D0:

- Trigger crucial point:
- 2  from J/,
- soft lepton, (soft lepton+non prompt track)
- 2 non-prompt tracks (CDF)

- e,

- P.V.

- (Track)

- 11/3/2005

**Notes:**
Track based analysis

## Only meson to have 2 spectator-model weak decays with comparable amplitudes (b and c decays).

- Possible contamination for Bs decays
- Perfect source of flavour-tagged Bs
- Measure angle  in                      self-tagged decays

**Relevance of mass measurements**

**Relevance of B****c**

- Spectroscopy of heavy-light quark system, to complement quarkonia
- Verify detailed calculation and hypothesis (potential,  NRQCD ....)
- Validation of Lattice QCD
- Spectroscopy of heavy-heavy mesons: quarkonia vs. Bc.

- [Masetti, Fleischer-Wyler,Kiselev]

- 11/3/2005

## Fully reconstructed modes using J/ trigger

- Fully reconstructed modes using J/ trigger
- D0 more candidates
- CDF better mass resolution
- (11 MeV, J/ mass constrained)

**Calibration using J/******** mass, **
**checked against the *****Y, *****systematics sub-MeV**

***b***** hadron masses**

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## Systematics below 1 MeV for high statistics channels

- Systematics below 1 MeV for high statistics channels
- Best single measurements of *b*-hadron masses

***b***** hadron masses**

**B****+**

**B****0**

**B****s**** ****mass**

******b ****mass**

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## Tevatron best place to measure Bc mass precisely

- CDF: Search for fully reconstructed mode

- Trigger: 2 ’s from J/pT > 1.5 GeV/c
- 2-body topology, reference mode B+  J/ K+
- Blind search: range: semileptonic mass ± 2m .
- Experimental issues:
- 		lifetime, small *BR*, small prod.
- expected 10-50 events, based on Run I rate.

- 

- 

- 

- P.V.

**Background:**
- Prompt J/ associated to random prompt track
- 		 require lifetime
- Secondary J/with prompt track
- Secondary J/ with non prompt track
- 		 require good vertexing

**CDF Fully reconstructed B****c**

- 11/3/2005

## CDF Fully reconstructed Bc

- After box open: scan search region with binned likelihood fit:
-  mass fixed (scanned), Gaussian width fixed (resolution), S,B fit parameters

**CDF Fully reconstructed B****c**

- Score function

- Threshold value

- From “*toy Monte Carlo*”, P  1/1000 false positive

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## Unbinned likelihood fit. Mass: fit parameter, width fixed.

- Mass = 6287.0 ± 4.8(stat.) ± 1.1(syst.) MeV/c2

**Main systematics:**
- Fit function/Background
- Momentum scale
- pT spectrum

- Theory in very good agreement.
- Potential models, NRQCD, LQCD
*Good topic for Moriond QCD*

**CDF Fully reconstructed B****c**

- This result

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## D0 Semi-leptonic Bc decay

- Inclusive measurement BcJ/ X
- Same strategy, require 3rd track be a .
- Inclusive measurement, no pointing constraint.
- No lifetime cut  mass and lifetime measurement
- Depends on Monte Carlo for Probability Density Function and “k-factor”
- Control sample: (2S) X X(expected low BR)
- Signal: 95±12±11 candidates,
- Significance likelihood ratio 60
- Mass =                             MeV/c2

- D0 ICHEP 04

- 5.4    5.6   5.8   6.0   6.2   6.4   6.6    6.8
- 	             Mass (GeV/c2)

- Systematic uncertainties from MC sample composition and decay model; background fraction. Larger than stat.

**-2 log(Likelihood)**

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**Notes:**
231 candidates (S+B)

## b and c-mesons excited states

- Evidence for the decay
- Bs Ds1(2536)  X
- Signal: 18 ± 5.5 candidates, 3.5 

- ICHEP 04

- 435pb

- Studies of excited b-mesons for Same Side tagging & MC tuning
- Soft  from fragmentation and decay

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## B-hadrons mass summary

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## CDF/D0 Rare decays

- BR = (3.4 ±0.54)   place to look for new Physics
- mSUGRA models enhanced 10 to 100 (Dedes, Dreiner, Nierste, hep-ph/0108037)
- SO(10) models 100 (Dermisek, Rabi et al. hep-ph/0304101)
- MSSM models enhanced 1000
- D0 updated measurement to include 300 pb
- CDF uses 171 pb Mass resolution 27 MeV/c2
- Limits on both Bd and Bs  Both analyses blind

|  | BR (Bs  | BR(Bd ) |
| --- | --- | --- |
| D0 |  | ---------- |
| CDF |  |  |

******% CL**

- D0 looking for BR (Bs Closed box
- Attainable Sensitivity = 1.2 10 (95% CL)

**CDF/D0 Rare decays**

- 

- 

- b

- s

- 300 pb-1

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**Notes:**
D0 relies on J/psi K, cdf doesn’t.
CDF has a lifetime cut ct > 200 mum
D0 uses lxy/sigma > 18.5 !!
Both use isolation cuts.
CDF & D0 both published PRL
Phi mumu predicted at the level of 10-6

## Mixing measurements

**Mixing measurements**

- Reconstruct signal(s) flavor specific (selection cuts)
- Measure decay time for each candidate
- Establish flavor (        )  at production ( tagging)

- Mixing Asymmetry

- Need high statistics sample, well measured lifetime.

- Tagging production flavor

- Statistics reduced by a factor D2**: **
- N  tagged events = D2N useful events

- *m*s:
- lower statistics Bs
- larger *m*s

- s.l.decays larger t

- 11/3/2005

## Flavor tagging

**Flavor tagging**

**Opposite side**
- Soft-Lepton tag
-      Flavor from the sign of the lepton (*e* or ) in semileptonic decays of accompanying *b*-meson.
- 	Source of dilution: charm semi-leptonic cascade decays, oscillation in the opposite side.
- Kaon Tag:
-   	Sign of the kaon in cascade decay *b **** c **** s*
- Jet Charge
- 	Sign of the momentum-weighted average charge of opposite jet.
**Same side**
- 	Bs has preferentially a K “close by”, _B_s has a K, B0 has a  , _B_0 has a 

- 11/3/2005

## Flavor tagging

**Flavor tagging**

- D0 use “any”  for tagging, use opposite side fully reconstructed decays, semileptonic decays for high statistics

- Opposite side tagging is the same as for Bs mixing: use Dilution from
- Bd to fix this parameter for Bs.

| D2 (%) | CDF s.l. | D0 s.l. | CDF had |
| --- | --- | --- | --- |
| SST (Bd) | 1.04 ± 0.35 ± 0.06 | 1.00 ± 0.36 | ---- |
| Soft  | 0.56 ± 0.05 | 1.00 ± 0.38 | 0.46 ± 0.11 ± 0.03 |
| Soft e | 0.29 ± 0.03 | -- | 0.18 ± 0.06 ± 0.02 |
| Jet Qpt | 0.16 ± 0.03 ± 0.03 | 1 | 0.24 ± 0.09 ± 0.01 |
| Jet Qjp | 0.150 ± 0.03 ± 0.02 |  | 0.11 ± 0.06 ± 0.02 |
| Jet Qvtx | 0.26 ± 0.03 ± 0.02 |  | 0.14 ± 0.07 ± 0.01 |
| Combined | 1.429 ± 0.093 |  | 1.12 ± 0.18 ± 0.04 |

- Overall fitter

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## md measurements

******m****d**** measurements**

- NEW since la Thuile ‘05

| Exp’t | (pb) | channel | Tag | Result |
| --- | --- | --- | --- | --- |
| D0 | 250 | s.l. | combined | 0.456 ± 0.034 (stat.) ± 0.024 (syst.) |
| D0 | 460 | s.l. | o.s.t. | 0.558 ± 0.048 (stat.) ± x.xxx (syst.) |
| CDF | 355 | s.l. | o.s.t. | 0.497 ± 0.028 (stat) ± 0.015 (syst.) |
| CDF | 355 | f.r. | o.s.t. | 0.503 ± 0.063 (stat) ± 0.015 (syst.) |

- Main purpose: tagging and fitting test preparing for ms
- Best measurement HFAG md =  (0.506 ± 0.006 ± 0.008) ps

- 460 pb

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## Amplitude scan

**Amplitude scan**

- Fourier-transform method
- Fix frequency (m)
- Fit for the oscillation amplitude.
**Limit at 95%:** lowest valuemlim
-    P(A (mlim)  1) = 5%
**Sensitivity:** lowest value of m with error compatible with 1 (at 5%)
**Measurement:** (range of) amplitude(s) compatible with 1 and not compatible with 0.....value of m from asymmetry fit !
- Advantage: easier to combine results

- semileptonic

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## ms CDF sensitivity studies

******m****s**** CDF sensitivity studies**

- World average
- Limit: ms > 14.5 ps
- Sensitivity for ms < 18.3 ps

- PDG 2004 & HFAG

- CDF 2

- CDF Semileptonic:
- Bs  Ds l X ,
-           Ds  , K*K, 
- CDF hadronic
- Bs   Ds ,
-           Ds  , K*K, 

- 

- 

- D0 Semileptonic:
- Bs  Ds l X ,  7000
-           Ds  

- 11/3/2005

## ms > 5.0 ps at 95% CL

******m****s**** D0 Preliminary results**

- Semi leptonic decays
- L = 460 pb, opposite side tag

******m****s**** > 5.0 ps******** at 95% CL**

- Limit < world average, but this is a first step in the full analysis

**Tagged 376****31**

- D = 0.47 ± 0.01

- 11/3/2005

## Otherb-physics results:

**Other*********b*****-physics results:**

- CP Asymmetry in B+  K
- 					PRL, hep-ex/0502044
- Evidence for the decay Bs 
- 			PRL, hep-ex/0502044
- CP Asymmetry in B  hh (h=,K) ICHEP’04

- ICHEP 04

- ACP (B+   K)

**B****s**** penguin-diagram decay**

- ICHEP 04

- 11/3/2005

## Conclusions

**Conclusions**

- The Tevatron can produce unique results in B Physics and confirm/complement B factories.
*m* *u,d,s,c*
- Best measurements of *b*-hadron masses, at 0.02% level
- CDF first evidence of a fully reconstructed Bc decay  **m****Bc**** = 6287.0 ****± ****4.8 ****±**** 1.1 MeV/c****2**
- Run 2 confirmation of semileptonic Bc decay
- Rare decays improve limits on new Physics.
- *m**d*
- Flavour taggers: B0 mixing as a proof of principle.
- Amplitude scan method used for B0
- *m**s*
- D0 first preliminary ms measurement from Run 2: ******m****s**** > 5.0 ps******** at 95% CL**
-  and  : see next talk
- Results improve faster than        : systematics and techniques.
- Including other decay modes, taggers, *data.... Moriond QCD*

- 11/3/2005

## Backup Slides

- Aurora Borealis at Fermilab
- 9th November 2004, 3 a.m.
- 42°N

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## Slide 24

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## Slide 25

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## Summary of cut values used:

- pT () 		> 1.8 GeV/c
- Lxy/(Lxy) 	      > 4.4
- 2(3D)  		< 9.0
- d0(Bc)  		< 65 m
- pointing angle< 0.4 radians
- 2vtx() 		< 2.6
- ct 		<  750 m

| Cut | MC Efficiency | N-1 data entries | Background rejection |
| --- | --- | --- | --- |
| Lxy/(Lxy) | 42.0% | 11930 | 96.7% |
| pT () | 62.3% | 3043 | 87.1% |
| 2(3D) | 80.5% | 762 | 48.4% |
| Pointing angle | 85.4% | 768 | 48.8% |
| 2vtx() | 92.7% | 565 | 30.4% |
| d0(Bc) | 97.5% | 448 | 12.3% |
| ct | 98.7% | 410 | 4.1% |

**CDF Fully reconstructed B****c**

- Maximized

- S = number of signal events from MC
- B = average number of background events (data) from whole region in a window  ±2- wide (60.4 MeV/c2).

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## CDF Fully reconstructed Bc

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## CDF Partially reconstructed hadronic Bc

- No pointing cuts
- Relax vertex chi2

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## D0 combined taggers, semileptonic decays, 250 pb:

- md = 0.456 ± 0.034* (stat.)* ± 0.024 *(syst.)* ps
- D0 combined opposite side taggers, semileptonic decays, 460 pb:
- md = 0.558 ± 0.048* (stat.)* ± x.xxx *(syst.)* ps
- CDF combined opposite side taggers, semileptonic decays, 355 pb :
- md = 0.497 ± 0.028 *(stat)* ± 0.015 *(syst.)* ps
- CDF combined opposide side taggers, fully reco. decays, 355 pb :
- md = 0.503 ± 0.063 *(stat)* ± 0.015 *(syst.)* ps

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## Mixing Control sample: Bu

**Mixing Control sample: B****u**

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## Mixing and CKM

**Mixing and CKM**

-  *m*s time independent CP violation in Bs (g)
-  *m*s / *m*d well theoretically understood
-  *m*s / *m*d sensitive to new Physics
- Bs oscillations: *m*s,s

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## Slide 32

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