Study of b sand b d

Colin Jessop

SLAC

BaBar Collaboration

Conference Papers ABS864, ABS865 and ABS866(Also on hep-ex)

Physics Interest

Exclusive Measurements:

B(->*) QCD test Acp(B ->K*) Non SM CP violation B(B ->)/B(B -> K*) Constrain Vtd/Vts

Inclusive Measurements:

B(b -> s) Constrain new physicsE spectrum from b -> s Mass and Fermi motion of b

BaBar Detector

K/ separationfrom DIRC

Photons fromCsI Calorimeter

Strengths for b ->s,d studies

(NIM A 479, 1 2002)

Asymmetric e- (9 GeV) e+ (3.1 GeV) collisions at s =10.56 GeV

Event Selection - →*(K+ -)

Isolated high energy (1.5 <E* < 3.5 GeV)

Veto photons from

Note isotropic topology

(Un-vetoed are a significant background)

K+

-

Lateral profile is EM like

Continuum(qq) Background

qq, ( q =u,d,s,c) “underneath” the bb

“Jet-like” topology as qq produced above threshold

“shape” variables w.r.t to e.g. cos Thrust- ,energy flowCombinations of variables,

e.g Neural Net, help with two component background

B(B -> K* and Acp(B -> K*)

E

(* = CMS frame) 2*2*BbeamES pEM ***

beamB EEE

B(B0 -> K0*) /10-

5

B(B+ -> K+*)/10-5 Acp

Theory(avg.)

7. 5 3.0 7.5 3.0 |Acp|< 0.005

BaBarPRL 88,161805(2002)

4.230.40(stat.) 0.22(sys.)

3.83 0.62(stat.) 0.22(sys.)

-0.17 < Acp < 0.08(90 % C.L)

22.7 x106 BB

theory=hep-ph/0106081,0106067,0105302

Search for B ->

)*(

)(2

KBB

BB

V

V

ts

td

Goal is to measure and compare to Ms/Md B-mixing to over-constrain CKM

Experiment:

Challenges

Theory:

error in Vtd/Vts extraction

cf. Ms/Md 7% error

B(B -> ) ~ 1/50 B(B -> K*)K*B ->K* b->sB -> 0

backgrounds

Background Rejection

Continuum rejection variables (shape,Z,flavor tag) combined in neural net. Validate with control samples.

+ eff. of 80% with K+ miss-id of 1% removes B->*(K+ -/K+ )

bkg.

B -> result Signal Estimated with Maximum Likelihood Fit (E,MES,M)

Data: 84 x 106 BB pairsNo Signal, 90% C.L. set

a) B(B0 -> ) < 1.4 x 10-6

b) B(B+ ->) < 2.3 x 10-6

c) B(B0 -> ) < 1.2 x 10-6

Analysis was performed with signal region “blinded”

MES (GeV)

E*

GeV SM Theory: 0.49 0.16x10-6

0.76 +0.26/-0.23 x 10-6

SM Theory: 0.85 0.32x10-6

1.53 +0.53-0.46 x10-6

SM Theory: Same as (isospin sym)

Theory: hep-ph/0105302,0106081

Unitarity triangle

Using =0.7 and R=-0.25: Ali & Parkhomenko (Eur Phys. J. C23:89 (2002))

Implications for beyond SM in Ali & Lunghi hep-ph/0206242

Combined limit: (B(B0 → )= B(B0 → )=2.B(B+ → )

B(B → )< 1.9 x 10-6

047.0)*(

)(1

1

1 2

3

2*

22

KBB

BBR

Mm

Mm

V

V

BK

B

ts

td

036.0ts

td

V

V 90% C.L

Inclusive b -> s

s

b

Theory: NLO B(b->s)=3.57+ - 0.30 x 10-4 (hep-ph/0207131)

Phenomenological models of Espectrum parameterized in mb and

hep-ph/9805303)

Phenomenological Model of Xs fragmentation (JETSET) (hep-ph950891)

b

Xs

B

HQET: Quark-Hadron Duality B(b -> s) = B(B -> Xs)

Semi-Inclusive Fully Inclusive

Background Rejection

(Exclusive States) Lepton tags

Efficiency 3% 1%

Fraction of Xs states:

50% 100%

qq bkg estimation Sideband subtraction Off-resonance data

BB bkg estimation Monte Carlo M. Carlo – data validated

X-feed bkg estimation

Monte Carlo No X-feed

Spectral Resolution Mxs ~ 5 MeV E~100 MeV

Model Dependence Xs, K*/Xs, Mxs cut E

If require just bkg. ~103.Sig.

Challenge is to reduce bkg whileMinimizing stat.+sys.+model errors

Two approaches:B -> Xs BB

qq

Semi-Inclusive B -> Xsexclusive states) = K+/K0

s +up to 3 (10) , 12 states

Subtract continuum with sidebandX-feed and BB bkg with Monte Carlo

Observe discrepency in JETSETsimulation of Xs fragmentation.

Efficiency from Monte Carloweighted to correct discrepency

Correct for undetected modes

E

Data 22M BB

MES (GeV)

1.4 < MXs < 1.6 GeV

MXs (GeV)

<E>=2.35 0.04 (stat.) 0.04(sys.)

=0.37 0.09 (stat.) 0.07(sys.) 0.10(theory)(Using Ligeti et.al PRD 60, 034019 (1999)) &mb=4.79 0.08 (stat.) 0.10(sys.) 0.10(theory)(Ligeti – private comm. )

Fix mb=4.79 and fit using spectrumOf Kagan & Neubert Euro.Phys. J.C 7,5(1999)

B(B ->Xs)=4.3 0.5 (stat.) 0.8(sys.) 1.3(theory)x 10-4

B

sXB

m

mmE 2

22

MXs (GeV)

E (GeV)

from b -> s

Fully Inclusive B -> Xs

Xs

B

XcB

lepton

The tag is uncorrelated with signal B so no model dependence

5% Efficiency for x1200 reduction in background

Suppress continuum background by requiring high momentum lepton tag (Pe(P) > 1.3(1.55) GeV Additional shape variablecos(e)(cos())>-0.75(-0.7)

Missing E > 1.2 GeV (Signal leptons fromB → Xl

Fully Inclusive B -> Xs

2.1 < E < 2.7 Signal Region (from considering stat+sys+model error)

MC Expectation in 61 x 106 BB

Model Dependence of E*

BBB → Xs

qq

B -> XsBB

qq

Fully Inclusive B -> XsDominant Systematic Uncertainty is from BB bkg, subtraction

BB Background ~90% 0hadrons in EM

BB 0/Background Control Sample

MC is used for BB subtraction To Test: Same Selection as Signal sample except requireto be from 0Correct MC for integral in2.1< E* GeVby factor 0.89 ±0.17

Fully Inclusive B -> Xs

61 x 106 BB (54.6 fb-1)

Continuum Subtraction with6.4 fb-1 of “off-resonance” data

B(B -> Xs) = 3.88±0.36(stat.)±0.37(sys.)+0.43/-0.23 (theory) x 10-4

Subtract assumed 4±1.6% b -> d

BB subtraction with Monte Carlo

Signal Region was “blinded”

Br(B->Xs)

Br(B->Xs)

Conclusions

Experimental precision is approaching theoretical errors

New limits on B -> Will soon help constrain CKM

First results from BaBar on B -> Xs

New techniques for measuring B -> Xs provides competitative B(B -> Xs) and will improve rapidly ( < 10% soon)