# Presentation: 771796

## Rare and Semileptonic Decays of B and K Mesons

***Jeffrey D. Richman***
***University of California, Santa Barbara***
***B******A******B******AR Collaboration***

**Particles and Nuclei International Conference**
**Santa Fe, Oct. 27, 2005  **

## Goals and challenges
KL0 
The “kaon revolution”: KL e- , |Vus|, and the recalibration of kaon branching fractions
Electroweak penguin/box diagram processes:                                      BK*, B, BXs  and BK l+l-, BK* l+l-
Semileptonic B decays and the measurement of |Vcb |, |Vub |, mb, mc
[Leptonic B decays: Bs+B+ ]
Perspective and conclusions

*K**L*0 
- The “kaon revolution”: *K**L* *e**-* , |*V**us*|, and the recalibration of kaon branching fractions
- Electroweak penguin/box diagram processes:                                      *B**K**, *B*, *B**X**s*  and *B**K* *l**+**l**-*, *B**K** *l**+**l**-*
- Semileptonic *B* decays and the measurement of |*V**cb *|, |*V**ub *|, *m**b*, *m**c*
- [Leptonic *B* decays: *B**s***+*******B**+*** ]
- Perspective and conclusions

- Outline

- Far too many topics to cover... my apologies!  Parallel session talks contain many
- more details (Bizjak, Godang, Koeneke, Mohapatra,...)

## Rare and Semileptonic Decays: Goals

- _Rare decay: loop/box process_
-  test SM at 1-loop level
-  new (heavy) particles can be 	produced in virtual intermediate	states; can compete with SM amps
-  search for effects of new physics

- _Semileptonic decay: tree diagram_
-  measure |*V*ij|
-  determine quark masses, QCD 	parameters

## Common theme: understanding dynamics

-  Amplitude factorizes  single 	hadronic current
-  Form factors/QCD parameters	can sometimes be 	extracted 	from data or be calculated
-  Precise rate predictions possible 	for some processes
-  Methods: HQET, heavy-quark 	expansions, 	lattice QCD,...

- Understanding dynamics is an
- important goal in itself!

##  CKM matrix: b and s decays are both suppressed!

-  CKM matrix: *b* and *s* decays are both suppressed!

- (Wolfenstein parametrization)

- 5 highlighted *V*ij:
- discuss in this talk!

- unitarity:
- 6 triangles, all
- with same area

## BABAR

*B**A**B**A**R*

## KL0

*K*L0

-  *K*L decay directly measures height of unitarity triangle)!
-  SM prediction:
-  Use *K*+0 *e*+  measurement to compute hadronic current.

- E949, PRL 93, 031801 (2004)

## Preliminary results on KL0 from KEK E391a

-  So far, only very small 	fraction 	of data used.
-  No events observed in 	signal box
-  E391a goal
-  Proposal in preparation for 	follow-on experiment at 		J-PARC

- Preliminary results on *K*L0 from KEK E391a

- 2. Reconstruct decay 	vertex assuming 	M=M(0).

- 3. Signature:
-  	*z*(vertex) and pt

- Major backgrounds

- 1. Measure  position 	and energy in CsI

## Ke , |Vus|, and the “kaon revolution”

*K*e , |*V**us*|, and the “kaon revolution”

- long distance
- rad. corrections

- I-spin corr.
- for *K*+ decay

*K**L**e*: 1
*K*+*e*:1/2

- form factor
- theory: *q*2=0
- exp’t: shape

- Review of Particle Properties, 2002

- Cirigliano et al.,
- Eur.Phys. J C35, 53 (2004)
- Andre, hep-ph/0406006

- Leutwyler & Roos,
-  Z.Phys.25, 91 (1984)

- short distance
- radiative corr.

- Sirlin, Nucl. Phys.
- B196, 83 (1982)

- +other work in
- progress

- experiment: BR, **

## Recalibration of KL branching fractions

- KTeV measured 6 largest *K**L* modes [PRL 93, 181802-1 (2004)]
-   Account for 99.93% of decays; 5 ratios of branching fractions
-   105-106 events/mode; careful treatment of radiation from electrons.
-   Measurement of *K**L* semilep form factors (1.7%-4.2% shifts) [hep-	ex/0406003, 0406006]

- E. Blucher,
- Lepton-Photon 2005

- fit to all new meas.

## Extraction of |Vus|

- Extraction of |*V**us*|

- Average of recent results:
-  KLOE, KTeV, NA48, 	ISTRA+
-  correlations taken into 	account

- E. Blucher, Lepton-Photon 2005

- Competing method:  (*K*++  [KLOE, hep-ex/0509045] + lattice [MILC, PRD70, 114501 (2004);  Marciano, PRL93, 231803 (2004)]

## Radiative penguin decays of  B mesons

- Radiative penguin decays of  *B* mesons

**Observation of***** B**********K* *********
- CLEO II (1993):  Loops in B decays!

- PRL 71, 674 (1993)
- cited >500 times!

- Now it’s a physics program!

## Observation of the bd decays B

- Ali, Lunghi, Parkhomenko,
- PLB 595, 323 (2004)

- Belle

- 8.2 evts

- 20.8 evts

- 5.9 evts

- Belle, 386 M BB
- hep-ex/0506079

*BABAR*, 211M BB
- PRL 94, 011801 (2005)

- good agreement
- w/global CKM fit

| Mode | BABAR (10-6) (2.1 signif.)  | Belle  (10-6)   (5.5 signif.)     |
| --- | --- | --- |
|  |  |  |
|  |  |  |
|  |  |  |

- Belle

## Inclusive BXs  Decay

-  Canonical process for testing the SM at 1 loop level
-  Provides powerful constraints on new physics models
-  Major effort by theory community to compute QCD and EW 	corrections; NLL calculation complete; NNLL calculation forseen

-  Belle, PRL93, 061803 (2004)

- fully incl.

- sum of 38 excl.
- modes

- Hurth, Lunghi, Porod, Nucl. Phys. B 704, 56 (2005); see also Neubert, Eur.Phys. J C40, 165 (2005);
-                                                                                      Buras et al., Nucl.Phys. B631, 219 (2002)

- Inclusive *B**X*s  Decay

- HFAG July 2005

## Moments of BXs  Photon Energy Spectrum

**Minimum E****γ**** (GeV)**

- hep-ex/0507001

**1****st**** Moment (GeV)**

**2****nd**** Moment (GeV****2****)**

**Minimum E****γ**** (GeV)**

- D. Benson, I.I. Bigi and N. Ultrasev Nucl. Phys. B** 710, **371-401 (2005)

- (see talk by Karsten Koeneke, Section VI.4)

- Used in determination of *m**b*, |*V**cb *|, and | *V**ub *|

## Electroweak penguins BKl+l- and BK*l+l-

- Electroweak penguins* B**Kl*+*l*- and *B**K***l*+*l*-

*BABAR* hep-ex/0507005  (229M *BB)*

- Belle prelim. hep-ex/0410006, 0508009

-  With *l*+*l*- pair, can produce both pseudoscalar and vector mesons
-  New physics can affect both rate and kinematic distributions.

## BKl+l- and BK*l+l-  : branching fractions

- Theory errors
- mainly due to
- form factors.

- (rarest observed *B* decay)

- pole at low *q*2

## BK*l+l-:  Lepton F-B Asymmetry 

*B**K***l*+*l*-**:  **Lepton F-B Asymmetry** **

- Lepton angular
- distribution in
*l**l* rest frame

- hep-ex/0508009

- Belle: lepton *A(*FB) [raw]

- 386 M BB

- SM

- NP scenarios

- constraints on Wilson coeffs describing short-distance physics

## Precision measurement of |Vcb| and the atomic physics of B mesons

*B**A**B**AR*, PRL 93, 011803 (2004)

- Observables

-  inclusive semileptonic rate
-  inclusive lepton-energy spectrum (moments)
-  inclusive recoil hadron mass spectrum (moments)

- Heavy-quark expansion theory params:

*|V**cb*|, *m**b*, *m**c*,  **, ***G *, *D *, *LS*

## |Vcb| and inclusive parameters from BXcl and BXs 

- |*V*cb| and inclusive parameters from *B**X*c*l* and *B**X*s 

- Buchmuller and Flacher; hep-ph/0507253
-  Fit to moments of inclusive distributions in *B**X*c *l*  and *B**X**s* 
-  Experiments: BABAR, Belle, CDF, CLEO, DELPHI

- <2%
- errors

*D***l*
- zero rec.

- kinetic
- mass scheme

- all moments

- all moments

## Measuring |Vub | is hard, but the error is shrinking

- Measuring |*V**ub *| is hard, but the error is shrinking

*BABAR**      *hep-ex/0509040

*b**u*

- continuum data (off res)

*b**c* subtraction

***B*****reco**

***B*****recoil**

***X******u***

***l***

****

**e****-**

***D********

****

**e****+**

- Lepton spectrum endpoint analysis

- Fully reconstructed *B* recoil analysis

- Large *b**c* background; suppression cuts introduce dependence on theory predictions for kinematic distributions.

- Belle

- hep-ex/0505088

## |Vub | inclusive measurements

- |*V*ub | inclusive measurements

-  Key CKM constraint
-  Use *m**b* and QCD  	parameters extracted from 	inclusive *B**X**c* *l*  	and 	*B**X**s*  spectra.
-  Many methods with 	uncertainties around 10%.
-  Uncertainty from *m**b* has 	been reduced to 4.5%.
-  With more data, the |*V**ub*| 	uncertainties could be 	pushed down to 5%-6.5%.

*m**X** *vs. *q*2

*E**l* endpoint

*m**X*

*E**l** *vs. *q*2

- expt

*m**b*, theory

##  B0 l-  form-factor predictions 

- HPQCD: hep-lat/0408019

- Fermilab/MILC: hep-lat/0409116

*f*+(*q*2) is relevant
- form factor for
- B *l* l=e

- HPQCD

- Fermilab/MILC

- restricted *q*2 range

- At fixed *q*2, lepton
- momentum spectrum is
- exactly known in this
- mode, since only one
- form factor.

* **B*0* l**-** ** *form-factor predictions

- Measuring |*V*ub| using *B* *l* and lattice QCD

## B l branching fraction and q2 distribution

*B* *l* branching fraction and *q*2 distribution

- Becher and Hill, hep-ph/0509090

- Relatively flat
- distribution in spite of rapidly changing form factor.
- Consequence of *p*3 factor in decay rate.

- HFAG averages

## Search for Bs+- and B0l+l-

- _Highly suppressed in the SM_
-  *B**d*  suppressed by |*V**td*/*V**ts*|2
-  No SM signals expected at Tevatron 	or at *B* factories, but can have large 	enhancements from new physics.

|  | SM predict. | CDF | D0 | BABAR | Belle |
| --- | --- | --- | --- | --- | --- |
|  |  |  |  | - | - |
|  |  |  |  |  |  |
|  |  |  |  |  |  |

- Strong correlation with
- neutralino-proton cross
- section in mSUGRA!

- Beck,Kim,Ko hep-ph/0406033

## Perspective/Conclusions

-  Early results from 1st dedicated *K**L* experiment
-  *K**L* branching fractions re-measured: 5% to 8% shifts
-  |*V**us*| shift: +3%
-  Unitarity of 1st row of CKM matrix looks better; work in progress 	on |*V**ud*|
_*B*__ Physics_
-  *B* observed; provides interesting constraint on |*V**td*|/|*V**ts*|
-  Many *b**s* and *b**sl*+*l*- modes observed; studies of kinematic 	distributions are especially interesting
-  |*V**cb*| measured to 2% via inclusive method; *m**b* well determined
-  |*V**ub*| precision now below 10%.
-  Keep pushing inclusive vs. exclusive crosscheck!
-  Leptonic *B* decays providing interesting sensitivity to new physics
-  *B* factories will push to 1 ab-1. _Many more results to come!_

## Backup slides

## Huge program on B decays to charmless hadronic final states...

- Huge program on *B* decays to charmless hadronic final states...

- (10-6)

- see H. Jawahery talk for
- hadronic *b**s* decays

## Observation of the bd decays B

- Observation of the* b**d**** *decays* B*

- Note: naïve expectation is (*B*++(*B*00(*B*0
*BABAR*/Belle discrepancy on *B*00; to be resolved with more data.

*BABAR*

- Belle

## BABAR

*B**A**B**AR*

## BXs  New Physics Sensitivity

-  Constraints on Two Higgs doublet models (Type II)
-  *m**H* = charged Higgs mass
-  tan = ratio of vacuum expectation values of the two doublets
-  Hou [PRD48, 2342 (1993)],  Gambino & Misiak [Nucl. Phys		B611, 338 (2001)], Neubert [Eur. Phys. J C40, 165 (2005)].

- 90% C.L. allowed
- regions (above lines)

- current *BABAR* data

- future projections

- combined

- 2 ab-1

- 0.5 ab-1

- 1 ab-1

## Search for leptonic B- decays

- Search for leptonic *B**-* decays

- Non-relativistic mesons
- (2 heavy quarks):

-  helicity suppressed
-  CKM suppressed (*V**ub*)
-  annihilation diagram
-  tree-level sensitivity to *H*-

| meson | B (e) | B () | B () |
| --- | --- | --- | --- |
|  |  |  |  |
| K+ |  |  |  |
| B+ |  |  |  |

- Predicted leptonic branching fractions: (|*V**ub*| = 0.0039, *f**B** *= 200 MeV)

## Search for B- 

|  | SM | BABAR (232 M BB) | Belle (275 M BB) |
| --- | --- | --- | --- |
| B(B+ |  |  |  |

- Belle, hep-ex/0507034

*BABAR*, hep-ex 0507069

- ___ __reconstruction: a major challenge_
-  fully reconstruct other *B* in event
-  require lepton (or pion) and no 	additional observed energy (2-3)

***e*****-**

***e*****+**

********

******e**

********

***e*****-**

**********

*E*extra

**Backgrnd**

**Backgrnd**

- Expected
- signal x10

## Search for Bs+- and B0l+l-

- _Highly suppressed in the SM_
-  *B**d*  suppressed by |*V**td*/*V**ts*|2
-  No SM signals expected at Tevatron 	or at *B* factories, but can have large 	enhancements from new physics.

|  | SM predict. | CDF | D0 | BABAR | Belle |
| --- | --- | --- | --- | --- | --- |
|  |  |  |  | - | - |
|  |  |  |  |  |  |
|  |  |  |  |  |  |

- 90% C.L.

##  Bs+-and SUSY

- Dark matter cross section (p) vs. *B*(*B**s*+-).

- Dermisek, Raby, Roszkowski,
- Ruiz de Austri, hep-ph/0507233

- Baek, Kim, Ko, hep-ph/0406033

## Experiment vs. Lattice:  DK l form factor

## Measuring |Vub| using B l 

*B**A**B**AR*

- Projection to 1 ab-1* (data taken to be on *
*BK fit curve  from present measurement).*

- PRD 72, 051102 (2005)

- In the high *q*2 region alone, we will measure the branching fraction
- with an uncertainty of (6-7)% , or (3-3.5)% uncertainty on |*V*ub |. Lattice
- theorists expect to reach 6%, so exclusive/inclusive will be similar.

## Precision measurement of |Vcb|: fits to moments of lepton spectrum and hadron recoil spectrum 

- Precision measurement of |*V*cb|: fits to moments of lepton spectrum and hadron recoil spectrum

*m**X* moments

*E**l** *moments

- ● = used, ○ = unusedin the nominal fit

- Red line: OPE fitYellow band: theory errors

*B**A**B**AR*

****2/ndf = 20/15

- BABAR PRL 93:011803 (2004)

## W-mediated b-quark transitions have several key features in common with muon decay.

  Very strong dependence of decay rate on mass!

*W*-mediated *b*-quark transitions have several key features in common with muon decay.
-   Very strong dependence of decay rate on mass!

- Muon decay: a prototype low-energy weak decay

- (ignoring QED radiative corrections)