xlist rencontres de moriond: electroweak interactions and unified theories new results from babar:...

XLIst Rencontres de Moriond:XLIst Rencontres de Moriond:Electroweak Interactions and Unified TheoriesElectroweak Interactions and Unified Theories

New results from BaBar:New results from BaBar:Rare Meson Decays and the Search for New Rare Meson Decays and the Search for New

PhenomenaPhenomena

Jeffrey Berryhill (UC Santa Barbara)Jeffrey Berryhill (UC Santa Barbara)

for the BaBar Collaborationfor the BaBar Collaboration

March 12, 2006March 12, 2006TM

B →K ll , K* ll B→ K K ’ T/CP/CPT Violation in B0 mixingD+

S →

All results preliminary, based on 210 fb-1 (230M B pairs)

Moriond EW 12 Mar 06 2

B B →→K K llll and B and B →→K* K* ll ll

Exclusive decays from three b→ sll penguin diagrams New physics possible for each diagram, and also new operators (scalar penguins, right-handed currents)

Three-body kinematic distributions and decay rates to measureall three (complex) penguin amplitudes

Rare process with BF ~ 10-6

Decay Rates Well-Measured; Next step: distributions and asymmetries

Photon penguin (C7) Vector EW (C9) Axial-vector EW (C10)



New set of observables: angular distributions

B→ K*ll decay kinematics uniquely described by 3 angles + dilepton mass (q2)

Cos * lepton- angle in dilepton rest frame. Forward-backward asymmetric!

due to axial vector penguin (C10) amplitude

Asymmetry AFB vs. dilepton mass q2 gives C10 evolution

relative to symmetric C9 and C7

Cos K kaon angle in K* rest frame. Gives K* polarization

B

l-

l+

*

BK

K

SM

C7 = -C7(SM)

C9C10 = -C9C10(SM)

C7 = -C7(SM),C9C10 = -C9C10(SM)


Find ~50 needles in a haystack of 500 million B’s + 2 billion light quarks

Full B decay reconstruction to charged tracks: K+ll, KSll, K*0ll, K*+ll, l = e or

Strict particle ID requirements

Veto “peaking” backgrounds of B decays similar to signal

Construct multivariate discriminants to suppress “combinatorial” backgrounds

Signal yield extraction via multi-dimensional unbinned maximum likelihood fit

B→ Kll B→ Kll

Preliminary

B →K B →K ll ll and B →K* and B →K* llll


B B →→K K ll ll Angular DistributionAngular Distribution

AFB is non-zero only for non-zero scalar penguin contribution FS

signal

bkg

total

Consistent with SMexpectation FS = AFB = 0

PreliminaryB →Kll


B →K* B →K* llll Angular Distribution Angular Distribution

•Fit FL in q2 bins with 4d (mES, E, m(K), cos K)

•Fix FL, fit AFB in q2 bins with 4d (mES, E, m(K), cos *)

All procedures validated by J/ K(*) control samples

Background shape modeled from mES,E sidebands

PreliminaryB →K*ll, q2 > 0.1 GeV2

FL fit

AFB fit


K* polarization FL

K* polarization consistent with Standard Model

Possible to excludeC7 = -C7(SM) with 1 ab-1

SM

C7 = -C7(SM)


Preliminary


Low q2 lower limit excludes SM at 98% CL (2.05)

SM

C9C10 = -C9C10(SM)

AFB

AFB =


Preliminary

At high q2, wrong-sign C9C10

is excluded at >3

SM

AFB (SM) = 0.03

AFB (SM) = 0.38 SM and alternate predictions from NNLO OPE + LCSR form factors, Ali et al. Phys. Rev. D 66 034002 (2002)Ball and Zwicky Phys. Rev. D 71 014029 (2005)


B B →→K K and Search for B and Search for B →→K K ''

B →K, K' are 3-body exclusive decays from b→ s photon penguin diagram

B+ → K+ decay observed by Belle in 2004,and 3.4 evidence for neutral K0 decay

Charged mode K+: test direct CP asymmetry for new weak phase in photon penguins

Neutral mode K0 a CP eigenstate, can measure time-dependent CPV like KS0as a SM null test (Atwood, Gershon, Hazumi, and Soni, Phys. Rev. D71 076003)

K' has never been searched for; could be enhanced like K'?

BF =



K+

K0

K+

K0

Signal extraction with multi-dimensional unbinned likelihood fit to (mES, E, Fisher, (') mass)

Require high-energy photon with E* > 1.6 GeVSeparate large qq background with Fisher discriminant of event shape data

5.3 observation of K0

K+ rate consistent with BelleACP consistent with 0

Fit projections of mES, E w/LH cut

Preliminary



No evidence for B → K ' decays

Consistent with prediction ofLipkin, Phys.Lett. B254, 247 (1991)of suppression relative to B → K

First limits for this decay mode

K+'

K0'

Preliminary

2 excess


T/CP/CPT Violation in BT/CP/CPT Violation in B00 Mixing Mixing

General complex amplitudes for neutral meson mixing:

CPT conservation → z = 0 T conservation → |q/p| = 1

CP conservation → z = 0 and |q/p| = 1

Standard Model CP violation in B0 mixing expected to give 1 - |q/p|2 ~ 10-3 or less

Measure mixing matrix via asymmetries in t distribution of B0-B0 system

t sign determined by which B flavor decayed first



Same-sign dilepton charge asymmetry: sensitive to CP or T violation in |q/p|

Traditional mixing method at Y(4S): count charge combinations where bothB’s decay semileptonically, as a function of lifetime difference t

CASE I:SAME-SIGNDILEPTONS



Opposite-sign dilepton t asymmetry:t sign-asymmetry amplitude sensitive to CPT or CP violation in z Im z or Re z (fix in cosh term)

CASE II:OPPOSITE-SIGNDILEPTONS



Select dilepton events with 0.8 < P* <2.3 GeVVeto conversions and charmoniaReject b →c → l cascade bkg with neural net

Selects 1.4 million events!(1.2 M Opp. sign, 0.2 M Same sign) Sample composition:signal 81%1 cascade + 1 direct 9%2 cascade 4%1 tau cascade + 1 direct 3%other 3%continuum 3%

Cascade background t distribution wider than direct signal decay t → separate with a t fit

Neural net inputs for cascade rejection

Preliminary



Binned likelihood fit of t distribution with 11 components (10 background + signal)

Simultaneous fit over 16 samples (4 lepton flavor comb. X 4 lepton charge comb.)

Muon charge asymmetry is floating in the fit; electron asymmetry fixed from Bhabha data

Charge asymmetry largestCPV systematic

Alignment/t model largestCPTV systematic

Same signt fit Opp. sign

t fit Preliminary



Consistent with CP/T/CPT conservation

fixed to 0.005 ps-1

Re z, Im z 76% corr.

Same-sign charge asymmetry Opposite-sign t asymmetry

PreliminaryPreliminary

Re()/(1 + ||2) = (1 - |q/p|2)/4 = (+0.4 ± 1.4 ± 0.9) ×10-3 BaBar Preliminary 2006

(-1.1 ± 1.0 ± 0.7) ×10-3 D0 Preliminary 2006 (-0.3 ± 2.0 ± 1.8) ×10-3 Belle 2005



New physics constraints in CP violating B mixing

+

Less room for new weakphase in B mixing

+


Leptonic meson decay rate simply related to meson decay constants:

Leptonic decay proceeding through weak annihilation of quarks:

W , ,e

c

s

Helicity suppressed by light lepton mass: decay rate to muons ~10-3

Confidence in decay constant predictions necessary for interpretation of B, Bs mixing

DDSS → →and Decay Constant fand Decay Constant fDsDs

++=

+ + +


•D reco dramatically reduces background from u, d, s quarks and B mesons

•Signal is a peak in the variable M = M(DS*) – M(DS)

•Normalize to Ds →

•New method exploiting high statistics of e+e- → cc: “D reco” sample•Tag one c quark via full reconstruction of D(*) mesonReconstruct other signal c quark via D*S → DS →

DDSS → → and Decay Constant f and Decay Constant fDsDs


fake D tags bkg from tag D mass sidebands

Ds → signal

Ds to leptons bkg from e controlsampleSignal from binned likelihood fit of M in background-subtracted events

DDSS → → and Decay Constant f and Decay Constant fDsDs

N = 489±55

Ds → norm.Use BaBar measurement for Ds → BFfor Ds → BF

BaBar, Phys.Rev. D 71, 091104 (2005),

Normalize Ds → signal to Ds →

Preliminary Preliminary

Preliminary


DDSS →→ Decay Constant f Decay Constant fDsDs

BaBar (230 fb-1)

Lattice QCD

will improve to <5% precision with 1 ab-1

•Significant improvement on world average

•Good agreement with unquenched lattice QCD

BaBar (230 fb-1)

Validates recent QCD predictions at 10% level

Aubin et al. PRL 95 122002 (2005)

stat syst Ds →

BF, DS lifetime, and Vcs give Ds decay constant:

Preliminary


SummarySummary

•B →Kll , K*ll angular distributions test completeset of electroweak penguin amplitudes

•CP violation tested in B→ K first search forK ’ •New bounds on T/CP/CPT violation in B0 mixing

•Measurement of D+S →and fDs a precision

confirmation of lattice QCD



BaBar and Belle branching fractions agree with SM predictionsExperimental uncertainty already better than theoryDifference between BaBar and Belle becoming significant?

RAREST B DECAYS EVER OBSERVEDRAREST B DECAYS EVER OBSERVEDAlso ACP consistent with 0 at 25% level, e/ ratio consistent with unity

Preliminary


Partial branching fractions vs. dilepton mass consistent with SM + form factors


Floating fit parameters

Belle K*ll Results


Form Factor Model Dependence: AFB

Colangelo strongly disagrees with LCSR and Lattice (T3 form factor)


B B →→K K and Search for B and Search for B →→K K ’ ’

M(K+)

M(K0)

Observation of K0

New precise measurement of K+in agreement with initial Belle observation

First measurment of direct CP asymmetryin this decay

Background-subtracted M(K) has no sharp structure



No evidence for B → K ’ decays

Consistent with prediction ofLipkin, Phys.Lett. B254, 247 (1991)of suppression relative to B → K

First ever search for this decay

K+’

K0’



Observation of K0

New precise measurement of K+in agreement with initial Belle observation

First measurement of direct CP asymmetryin this decay

Background-subtracted M(K) has no sharp structure



t PDF



t PDF

Floating fit parameters

xlist rencontres de moriond: electroweak interactions and unified theories new results from babar:...

Documents

ll preliminary b

c7sm b

polarization b

ll slide

b pairs slide

b s photon penguin diagram

angular distributions

b decay reconstruction