# Presentation: 517948

## Rare B decays at Tevatron(Rare Decays of Heavy Flavor)

**Vyacheslav Krutelyov**
***University of California at Santa Barbara***
- May 24, 2006
- HCP06  Durham, NC

- Rare decays motivations
- Detectors
- Analyses/results D(), B
- Prospects & Summary

## Rare B (and charm) decays

- Rare:
- Suppressed in the Standard Model
- Small branching ratios ~<10-5
- Most likely a limit “observation”
- Rare B decays (in general):
- Charmless mesonic and baryonic
- Radiative
- Leptonic
- b(s,d) *ll* including FCNCs, LFV, LNV
- B*ll* from bs,d
- B+*l* from bu

- Rare Leptonics covered here
- Analyses of other (e, ) leptonics are in progress

**D****0************************ ****(CDF)**

**D****+******************************** ****(D****Ø****)**

**B****s(d)**************************** ****(D****Ø****)**

**B****s(d)************************ ****(CDF&D****Ø****)**

- S. Krutelyov     Rare decays at Tevatron

- 05/24/06

## Motivations (Hllh modes)

-  Probing for New Physics
- Look for excess in modes suppressed in SM
- The biggest interest is in FCNC decays:
-  A remarkable tool to search/constrain New Physics
- Charm: cu transition
- probes flavor sector not accessible in b-FCNCs
- B-FCNCs: (most often) bs transition
- bs a NP search and constraint workhorse for years
- Not easily experimentally accessible in hadron collider environment
- High sensitivity to exclusive dileptonB and Charm modes at CDF+DØ
- Dilepton (esp ) modes are clean in theory and experiment

- S. Krutelyov     Rare decays at Tevatron

- 05/24/06

## B production and detection at Tevatron

_**CDF:**_
-   Excellent silicon vertex detector
-   Good momentum and mass
-    resolutions

_**D**__**Ø**__**:**_
-   Extended muon coverage
-   New silicon detector was
-    installed in March

**Tevatron is great for heavy flavor:**
-  *b* cross-section x1000 larger than ee B factories
-  All B species are produced (B0, B, b, Bs, etc...)
**However,**
-   QCD production is even larger (x1000)
-  Triggering is a challenge:  collision rate 1.7 MHz  tape write limit ~100Hz

- S. Krutelyov     Rare decays at Tevatron

- 05/24/06

## B(and charm) detection at Tevatron: triggers

**B(and charm) detection at Tevatron: triggers**

- Dimuon trigger(s)

- Two (displaced) Track Trigger
- [charm and B]

- S. Krutelyov     Rare decays at Tevatron

- 05/24/06

## Rare Charm decays

- RPV:
- Burdman et al. hep-ph/0112235

- FCNCs: cu transition
- GIM suppression works well in SM (no top in the loop)
- Long-range effects (decays via resonances) dominate the Bratio
- B(D)~10-13    B(Dh)~10-9
- NP probes in flavor sector
- other than in bs(d) or sd
- Up-to experimental values are
- possible in R-parity violating
- or some non-universal SUSY

- FCNCs: D0D+ *ll*D+s K
- FCNC2, LFV,LNV: Dx*ll*(‘) (h)

- D+ 

- S. Krutelyov     Rare decays at Tevatron

- 05/24/06

## DØ: Rare Charm decays D+ 

- DØ: Rare Charm decays D+ 

- Use dimuon trigger sample
- MC for signal; data sidebands for bg
- Start with D+
- Maximize eff/[0.82+Nbgd1⁄2 ] for Ds  on
- vtx and  displacement significance (SD, S)
- Collinearity (vertex vs D candidate p) D
- Track Isolation of D candidate ID

- S. Krutelyov     Rare decays at Tevatron

- 05/24/06

## DØ: Rare Charm decays D+ 

- DØ: Rare Charm decays D+ 

- B[D+]=(1.75±0.7±0.5)×10-6

- +  track

- 

- Ds

- S. Krutelyov     Rare decays at Tevatron

- 05/24/06

## DØ: Rare Charm decays D+ 

- Now look off resonance
- Optimize for D+ with the same variables
- Larger D+ lifetime allows to cut tighter
- Then open signal box
- Observe 17 while expecting 21 events
- Set a limit (world best)
- B[D+]< 4.7×10-6 @ 90% CL
- PDG: 8.8*×*10-6 @ 90% CL
- New limit on RPV couplings
- kk < 0.002

- S. Krutelyov     Rare decays at Tevatron

- 05/24/06

## CDF: Rare Charm decays

- FCNCs
- D0
- D+ *l**l*D+s K
- Others (FCNC2, LFV,LNV) 	Dx*ll*h

- Use two (displaced) track trigger sample
- Normalize to Dhh or Dhhh  (h=K,pi)
- Signal mode naturally comes in the same sample
- Normn Bratios are large  good statistics
- Get peak/resonant Nbg by applying h fake rates
- Get combinatoric Nbg from sidebands
- “Unblind” by looking at lepton ID
- Available results: D0for 68 pb-1
- Work on other modes is in progress and is expected with an analysis of 1 fb-1 of data
- should achieve sensitivity comparable to that available  now (PDG  BaBar/Cleo-c/Belle/Hera-B/DØ)

- S. Krutelyov     Rare decays at Tevatron

- 05/24/06

## CDF: D0search (69 pb-1)

- Normalize to *D**0********** *
- Blind from ID
-  1.840<m<1.882 GeV
- Maximize eff/[1.5+Nbg1⁄2 ] using:
- Track and vertex impact parameter
- Two-track opening angle
- D candidate isolation

- S. Krutelyov     Rare decays at Tevatron

- 05/24/06

## CDF: D0search (69 pb-1)

- Background expected:
- [1.5±0.7]combinatoric + [0.3±0.1]misID
- With ID observe 0 events

- B(*D**0***)<2.510-6 @ 90% C.L.
- _[PRD 68, 091101 2003](http://www-cdf.fnal.gov/physics/preprints/cdf6464_d0mumu_sub1.ps)_
- Now superseded by result from BaBar
- B(*D**0***)<1.310-6 @ 90% C.L.
- 	cf BSM ~ 10-13
- With 1 fb-1 expect ~*×10-20** *improvement (to ~ 1 10-7)

- Muon ID

- S. Krutelyov     Rare decays at Tevatron

- 05/24/06

## Rare B-decays

- FCNCs are suppressed in SM
- Much softer suppression than in D*ll*h
- Thanks to the top in the loop
- Probe bs(d) transition
- Up-to experimental values are possible in NP scenarios
- R-parity violating SUSY
-  numerous SUSY/2HDM scenarios with large tan
- In SUSY the contribution is up to ~ tan6/MH4
- ~tan4 in 2HDM
- Bsis becoming golden
- One of the leading (by citation) analyses at CDF and D0
- Have a chance to see NP at Tevatron

- FCNCs
- Bs(d)ee
- (B/Bs/Bb*l**l*h
- (FCNC2, LFV,LNV, etc) Bx*ll*(‘)(h)

- S. Krutelyov     Rare decays at Tevatron

- 05/24/06

## Rare B-decays: Experiment

- Common steps
- Use a normalization mode
- CDF and DØ can normalize to dimuon Hb(h)J/  for dimuon rare B modes
- CDF specific: B ee, e search uses Bhh (two track trigger samle)
- Analysis is in progress
- Benefits: smaller statistical and systematic uncertainties
- Background (mostly combinatoric) is estimated from sidebands
- Discriminate based on vertex  and dilepton ID
- Use either a likelihood or a box cut
- MC for signal
- “Blind” optimization for best sensitivity

- FCNCs
- Bs(d)ee
- (B/Bs/Bb*l**l*h
- (FCNC2, LFV,LNV, etc) Bx*ll*(‘)(h)

- S. Krutelyov     Rare decays at Tevatron

- 05/24/06

##  DØ: Search for Bs

- SM prediction (non-resonant): BR: ~1.6×10-6
- 2HDM/SUSY: enhancement possible
- depending on parameters of tan and MH+
- Prior published limit [CDF Run I]: 6.7×10-5 @ 95% C.L.
- long-term goal: investigate bs *l**l* FCNC transitions in Bs meson

**Dilepton mass spectrum **
**in b -> s *****l l***** decay**

- J/

- ’

- S. Krutelyov     Rare decays at Tevatron

- 05/24/06

##  DØ: Search for Bs  

- 300 pb-1 of dimuon data
- normalize to resonant decay Bs  J/
- For non-resonant decay: cut out  and ’
- Blind analysis: minimize eff/[1+Nbg1⁄2] on random grid using:
- Pointing angle (collinearity)
- Decay length significance
- Isolation
- Background modeled from sidebands
- Use same cuts for Bs  J/ and off-resonance search mode

- 0.5 < M() < 4.4 GeV/c2
-  candidate: 1008<M<1032 MeV/c2
- good vertex
- pt(Bs cand.) > 5 GeV/c

- S. Krutelyov     Rare decays at Tevatron

- 05/24/06

##  DØ: Limit on Bs   

- expected background: 1.6 ± 0.4 events
- observe zero events in signal region

**BR(B****s ******** ********************)/BR(B****s ******** J********) < 4.4 × 10****-3 ****@ 95% C.L.**
- Using central value for **BR(B****s ******** J********) = 9.3×10****-4 **** PDG2004:**** **
**BR(B****s ******** ********************) < 4.1×10****-6**** @ 95% C.L.****       **_[hep-ex/0604015](http://arxiv.org/abs/hep-ex/0604015)_

- x10
- improvement
- w.r.t previous limit

- S. Krutelyov     Rare decays at Tevatron

- 05/24/06

## CDF: B-FCNCs

- Use HbJ/h mode as normalization for corresponding to Hbh
- B+J/K+ is used for Bs(d)
- Results are available for Bs(d) only
- (With some guess): for B h expect yields comparable to B-factories and sensitivity to Bs 

- The yield plots are  rough estimates of normalization signal available for analyses
- Actually optimized for lifetime analysis .. Actual numbers for this analysis can be different

- 0.5K b

- 4K BK*

- 3K BKS0

- 11K B+K+

- 1K Bs

- S. Krutelyov     Rare decays at Tevatron

- 05/24/06

## Bs(d)Search

- Still not observed:
- BSM(Bs×10-9   cf   Bexp < 1.5×10-7 @95% CL
- BSM(Bd×10-10   cf   Bexp < 4.0×10-8 @95% CL
- Normalize to B+J/ K+ decays
-     -  Construct discriminant to select Bs signal and suppress bgd
-     -  MC simulation for signal and mass sidebands for bgd estimate
-     -  Optimize on minimum expected 90% C.L. upper limit (95% CL for DØ)

- Normalization mode

- S. Krutelyov     Rare decays at Tevatron

- 05/24/06

## Bs(d)pre-selection

**Pre-selection DØ:**
- 4.5 < m< 7.0 GeV/c2
- pT()>2.5 GeV/c
- ()| < 2
- pT(Bs cand.)>5.0 GeV/c
- good vertex

- Potential sources of background:
-  continuum  Drell-Yan
-  sequential semi-leptonic b->c->s decays
-  double semi-leptonic bb-> X
-  b/c->x+fake,  fake + fake

***300 pb******-1***

**Preselection CDF:**
- 4.669 < m< 5.969 GeV/c2
- pT()>2.0  GeV/c
- pT(Bs cand.)>4.0 GeV/c
- (Bs)| < 1
- good vertex, displaced in 3D by 2

- 38k events

- DØ

- S. Krutelyov     Rare decays at Tevatron

- 05/24/06

## CDF: Bs(d) Signal vs. Bgd Discrimination

-  + mass, M
- Proper decay-length ():
- Isolation (Iso):
- (fraction of pT from B within R=(2+2)1/2 cone of 1)
- “pointing ()”:
- (3D angle between Bs momentum and decay axis)

- S. Krutelyov     Rare decays at Tevatron

- 05/24/06

## CDF: Bs(d) Signal vs. Bgd Discrimination

- CDF: Bs(d) Signal vs. Bgd Discrimination

- Construct Likelihood discriminant
- Mass not in the likelihood

-  **Optimal cut:  LH>0.99**

- S. Krutelyov     Rare decays at Tevatron

- 05/24/06

## DØ: Bs optimization

- optimize cuts using:
- angle between p( and Lxy vectors (pointing consistency)
- transverse decay length significance Lxy/σ(Lxy)** **
- isolation in cone around Bs candidate

-  Random Grid Search
-  maximize /(1.+B)

- S. Krutelyov     Rare decays at Tevatron

- 05/24/06

## Bs(d) results

- Bs(d) results

- CDF (780 pb-1):
- BR90% CL = 9.1×10-8
- Bs   Nbg=[1.1±0.4]comb+[0.2±0.06]Bhh
- Bd   Nbg=[1.1±0.4]comb+[1.4±0.2]Bhh
- Observe
- NBs=1  Br(Bs) < **1.0**×10-7**@ 95% CL**
**N**Bd=2 ****** **Br(Bd)< **3.0**×10-8**@ 95% CL**
- Both CDF Bs and Bd results are ~×2 better than the previous result
** **
- DØ (300 pb-1):
- observe 4, expect 4.3 ± 1.2
- DØ mass resolution is not sufficient to separate Bs from Bd. Assume no Bd contribution.
-  ****** **Br(Bs) < 4.0×10-7** @ 95% CL**
- DØ (1 fb-1) work in progress:
- Expect Br(Bs) < **2.3**×10-7**@ 95% CL**

- _[PRL 94, 071802 (2005)](http://scitation.aip.org/getpdf/servlet/GetPDFServlet?filetype=pdf&id=PRLTAO000094000007071802000001&idtype=cvips)_

- S. Krutelyov     Rare decays at Tevatron

- 05/24/06

## Bs(d) in SO(10) Grand Unification Model

- Bs(d)** in SO(10) Grand Unification Model**

**R. Dermisek *****et al*****.,  **
**hep-ph/0507233 (2005)**

- This model is especially sensitive to Br(Bs)
- With Yukawa unification tan~ 50
-  Br(Bs) is naturally enhanced
- Model allows massive neutrinos
- Consistent with  WMAP (Green)
- Excluded by theory/experiments (pink)
- Excluded by old Bs analysis (light blue)
**Red arrows indicate exclusion from our new result!!!**
**Result ****~ M****A****>0.65 TeV**
- Remaining white region is allowed

- S. Krutelyov     Rare decays at Tevatron

- 05/24/06

## Projected Sensitivity to Bs(d) 

- At Tevatron Run II: expect to go as low as Br[Bs 1-2×10-8
- Projection based on current sensitivity
-  No sensitivity to SM level branching ratio

- CMS/ATLAS have a potential to measure Bs at SM level with a couple of years of data [e.g. _[hep-ex/0509009](http://www.slac.stanford.edu/spires/find/hep/www?eprint=hepex-0509009)_ ]

- S. Krutelyov     Rare decays at Tevatron

- 05/24/06

## MSSM

-  It is possible to constrain mA or/and tan
- given an _**observation**_ of Bs
- using BR(Bs)~ tan6/mA4

- Given Minimal Flavor Violation ↔ flavor change from CKM only
- Substantial enhancement is possible in non-MFV case

- tan=50

- MFV

- S. Krutelyov     Rare decays at Tevatron

- 05/24/06

## Summary

- CDF and DØ provide new insights into the Rare decays with world best results
- Br(*B**s***)<8x10-8 at 90% C.L. (CDF 780 pb-1)
- Br(*B**d***)<2.3x10-8 at 90% C.L. (CDF 780 pb-1)
- Prospect for Br(*B**s***)~1-2×10-8 in Run II still holds
- Vital for large tan supersymmetry
- Br(*B**s***)<4.1x10-6 at 95% C.L. (DØ 0.45 fb-1) _[hep-ex/0604015](http://arxiv.org/abs/hep-ex/0604015)_
- Br(*D***)<2.4x10-6 at 90% C.L. (CDF 69 pb-1) _[PRD 68, 091101 2003](http://www-cdf.fnal.gov/physics/preprints/cdf6464_d0mumu_sub1.ps)_
-  superseded by BaBar
- Br(*D**+*****)<4.7x10-6 at 90% C.L. (DØ 1 fb-1)
- Br(*D**+***********)=(1.75±0.7±0.5)x10-6 at 90% C.L. (DØ 1 fb-1)

- S. Krutelyov     Rare decays at Tevatron

- 05/24/06

## BACKUP SLIDES

- S. Krutelyov     Rare decays at Tevatron

- 05/24/06

## CDF: Fake rates K,

- The rates are measured from D* D(K) sample
- Fake rates are essential for rare D-decays
- Less so for rare B-decays due to smaller Bhh Bratios [~ (Vcb/Vcs)2~0.01 suppression]
- Can become essential for Bdue to its small value and good exp sensitivity

- S. Krutelyov     Rare decays at Tevatron

- 05/24/06

## Rare B-decays

- In SUSY/2HDM
- With the available experimental sensitivity,
- dimuons are in a sweet spot to probe (heavy) Higgs sector
- Electrons don’t couple as strong, taus are too elusive
- Bratio measurement becomes a “precision”
- challenge for Hbh
- Need to measure shapes [(a)symmetries] to probe for NP
- Bsis a powerful for large tan SUSY and models with scalar exchange
- Due to the helicity suppression in SM, NP scalar exchange can become noticeable
- Combined with trilepton mode at low tan can restrict SUSY a lot
- The mode is becoming golden
- numerous theory papers
- One of the leading (by citation) analyses at CDF and D0

- FCNCs
- Bs(d)ee
- (B/Bs/Bbl+l-h
- (FCNC2, LFV,LNV, etc) Bxll(‘)(h)

- S. Krutelyov     Rare decays at Tevatron

- 05/24/06

## Bs(d) Signal vs. Bgd Discrimination

-  +- mass, M|M-MB|<60 MeV/c2  (2.5)
- _sidebands: 2__×__0.5 GeV/c__2__ on the sides_
- _signal: |M-5279|<60 MeV/c__2__ (B__d__0__) or |M-5279|<60 MeV/c__2 __(B__s__0__)_
- Proper decay-length ():
- Isolation (Iso):
- (fraction of pT from B within R=(2+2)1/2 cone of 1)
- “pointing ()”:
- (3D angle between Bs momentum and decay axis)

- S. Krutelyov     Rare decays at Tevatron

- 05/24/06

## Bhh Contribution Summary

- Mode            Br                  <Nbkg> in Bs Window                     <Nbkg> in Bd Window
-                   (10-6)          CMU-CMU      CMU-CMX           CMU-CMU        CMU-CMX
- Bd±0.4      0.007±0.002     0.0013±0.0004     0.081±0.015      0.014±0.004
- BdK  18.9±0.7      0.004±0.001     0.0008±0.0002     0.46±0.08          0.087±0.019
- BdKK     0.2±0.2           ~0                       ~0                 0.001±0.001             ~0
- Bs7.0±7.0      0.03±0.03        0.005±0.0005       0.005±0.004       0.001±0.001
- BsK7.7±7.7      0.049±0.048     0.009±0.009        0.051±0.050       0.010±0.010
- BsKK   35.1±7.8      0.073±0.020     0.016±0.005        0.54±0.13           0.12±0.03
- Total                             0.16±0.06         0.03±0.01           1.14±0.16            0.23±0.04
- Bhh

-   Total bkg = combinatoric + Bhh
-   Modes with limits only (except BK) are negligible
-   BK limit is near theory prediction

- S. Krutelyov     Rare decays at Tevatron

- 05/24/06

## E. Lungi et al.

- gray: theory errros on MBs

- line: measurement

- hep-ph/0605177

- S. Krutelyov     Rare decays at Tevatron

- 05/24/06

## E. Lungi et al.

- gray: excluded by FCNC data

- orange: opposite sign for the b! s  amplitude

- hep-ph/0605177

- S. Krutelyov     Rare decays at Tevatron

- 05/24/06

## E. Lungi et al.

- gray: excluded by FCNC data

- orange: opposite sign for the b! s  amplitude

- hep-ph/0605177

- S. Krutelyov     Rare decays at Tevatron

- 05/24/06

## BsProspects

- Additional handles on bgd exist:
-     tighter muon ID (require CMP)
-     calorimeter isolation
-     additional 2D pointing
-     use mass resolution model in LH
- Combine with D0
- BR(Bs) ≈ 1×10-8 at 90% CL
- is possible within Run II (by 09?)
- Can be measured at SM level      by CMS at LHC
- after 2-3 years of data taking
- (by 10?)

- Simplistic: no improvement to analysis
- scale Nbg and NB+ linearly with Lumi  recalculate <BR>
-  at best ~2×10-8 at 90% CL

- BsProspects

- S. Krutelyov     Rare decays at Tevatron

- 05/24/06

## Triggers used

- Dimuon trigger
- pT>1.5GeV, pT>2GeV, 0.6<1
- pT, , muon ID used to cut on tracks
- Used for X)

- Two Track Trigger
- pT>2GeV, 
- pT, , d0 info used to cut on 2 tracks
- Used for: B,Dhadrons  ; D

- All are input to the various Level-3 triggers
- That use the offline quality information

- S. Krutelyov     Rare decays at Tevatron

- 05/24/06

## B(D): Theoretical motivations. Current limits.

- B(D): Theoretical motivations. Current limits.

- Flavor Changing Neutral Current. 	          Loop contribution only in SM.
- BrSM(Bsμ+μ- )=(3.4±0.5)  10-9
- BrSM(Bdμ+μ- )=(1.00±0.14)  10-10 (hep-ph/0303060)
- BrSM(D0μ+μ- )~3*10-13  (GIM suppressed)
- Only upper experimental limit exists:
- Brexp(Bsμ+μ- )<2.010-6  90% C.L.  CDF RunI @100/pb.
- Brexp(Bdμ+μ- )<1.610-7  90% C.L.  Belle ‘03 @78/fb.
- Brexp(D0μ+μ-)<4.1(4.2)*10-6  90% C.L. BEATRICE(E771)

- Limits are far away from the SM value: can test for   a possible new physics.
- MSSM: Br(Bμ+μ-) enhanced by tanβ>10 terms ~tan6β. Up to 100 over the SM prediction.
- R-parity violating models give tree level contributions. Not heavily constrained by other observables.
- Can be seen in Run2 (esp. Bs)
- Other models enhance less. E.g., universal extra dimensions. Up to +70% for Bsμ+μ-

- RPV

- mSUGRA,SO(10)

- S. Krutelyov     Rare decays at Tevatron

- 05/24/06

## Overlap with measured δaμ (BNL)  in mSUGRA parameter space.

Overlap with dark matter=LSP allowed region.

Eliminate large parameter space (~ all for tanβ>40), with        Br(Bsμ+μ-)~10-8 in Run2

- Overlap with measured δaμ (BNL)  in mSUGRA parameter space.
- Overlap with dark matter=LSP allowed region.
- Eliminate large parameter space (~ all for tanβ>40), with        Br(Bsμ+μ-)~10-8 in Run2

- Motivations: Bsμ+μ-  (mSUGRA)

- S. Krutelyov     Rare decays at Tevatron

- 05/24/06

## RP Violation: Br vs. m1/2

**R. Arnowitt *****et al*****.,**
**hep-ph/0203069, **
**PLB 538 (2002) 121**

***e.g.*****,***** W*****TRPV ****=*****    ***********ijk****L****i****L****j****E****k **************’****ijk****L****i****Q****j****D****k **************’’****ijk****U****i****D****j****D****k**

- RP Violation: *Br* vs. *m*1/2

- S. Krutelyov     Rare decays at Tevatron

- 05/24/06