UCSD Physics Activities on BaBarProgress Report to DOE: 2004

Vivek Sharma

University of California, San Diego

2

Prize For Best PhD Dissertation At a US University or Laboratory

Citation:

"For his role in the development of the tools needed for the analysis of B factory data, including the tFIT program, a unique and comprehensive fitting framework for time-dependent analyses. The tools he developed played a key role in the observation of CP violation in the B system by the BaBar collaboration. These tools will be essential

to the ongoing program of work as the B factories continue to probe the origins of CP violation."

PhD Thesis Advisor : Vivek Sharma

2004Mitsuyoshi Tanaka Dissertation Award

to Shahram Rahatlou

University of California, San Diego

3

Outline of This Talk

• BaBar highlights from this summer

• Physics responsibilities and activities of UCSD physicists

• UCSD Physics Objectives

• Brief description of analyses pursued

• Outlook

• Enclosed with this document, for more elaborate reading:• David MacFarlane’s comprehensive review of ICHEP04 results from

Babar and Belle

• Vivek Sharma’s review talk on Rare B and D Decays at “Physics at Meson factories”, Frascati 2004.

• Daniele delRe’s talk on Vub at ICHEP04, Beijing

• Daniele delRe’s talk on Recoil-side physics at SuperBfactory workshop

• Shahram Rahatlou’s review talk on sin2+ at DPF 2004

• Shahram Rahatlou’s talk on BaBar Event Reconstruction at DPF2004

4

Reminder Of The Terminology

VtdVtb*

VudVub*

VcdVcb*

*cd cb

*td tb

V Varg

V V

*td tb

*ubud

V Varg

V V

*ubud*

cd cb

Varg

V

V

V

In a time-dependent CPV measurements:

With only one amplitude driving the decay,

Direct CP asymmetry C=0

CP CP CPf f d f d

f fA ( t) S sin m t C cos m t

f f

5

Summary Of BaBar Physics Productivity

~245 million BB pairs

3 x design

PEP-II machinecontinues to Excel !

Journal Publication

(PRL, PR(D) RC , PR(D), NIM etc

112

Papers submitted to ICHEP04 conference in Beijing

72

Parallel session speakers at ICHEP04 conference in Beijing

22

BaBar quick to analyze andprovide public results

6

BaBar Physics Highlights: Discovery of Direct CPV in B Decays

2 iSM amplitude e T P sinKA

( )A B f

2 2Bf f

B( )A B f

2 2

2 20 Direct

ff

CP

ff

A ABr B f Br B fA CPV

Br B f Br B f A A

B0K+

B0K+

CPV4.2

BABAR

signal enhanced

0.133 0.030 0.009 CPA

First Observation (4.2

Confirms at ICHEP04

0.101 0.025 0.005 CPASignal (in 274M BB pairs): 2140 53

Average 0.114 0.020 CPA

3.9BelleBelleBelleBelle

BBAABBARARBBAABBARAR

M BB Signal (in 227 pairs): 1606 51

7

BaBar Physics Highlights: Precision Measurement of sin2

sin2β = 0.722 0.040 (stat) 0.023 (sys)

B J/ψ KL (CP even) modeB (cc) KS (CP odd) modes

(2002 measurement: sin(2β) = 0.741±0.067±0.034)

Just Three years after its discovery CPV in B J/K0 is now a precision measurement

8

CP asymmetries in Penguin Dominated B Decays (sin2eff)

0B

0SK

0 0 B K

, ,u c t

0SK

0 0 B K

0B

Penguin dominated modes sensitive to New Physics in the loopWithout NP, expect “sin2” from penguin modes to be same as “sin2”

from K0 modulo corrections due to (small) contribution from other SM amplitudes

Adding Belle results, difference between measured sin2 from s-penguin and charmonium modes grows to

3.6 ??

Dif

fere

nce

is 2

.7

9

BaBar Physics Highlights: No CPV Seen in B0+ -

0 30 0.17 0 030 09 0.15 0.04

S . .C .

0 (227 pairs) B M 0 (227 pairs) B M

BaBar

100 0.21 0.070 58 0.15 0 07

S .C . .Belle

3.2

5.2

> 3 discrepancy between BABAR & Belle

10

BaBar Physics Highlights: Towards Precise Measurement of Angle

• In absence of Penguin contributions, can measure CKM angle from B0+ - or + -

• BaBar measurements show that B0+ - is most suited for measuring since

– Penguin pollution is more under control (limits on B00 0, B-- 0)

– The decay is dominated by one helicity amplitude well defined CP state

– Rate is reasonably large; first observation by BaBar (2003)

Tree

,

,

Penguin,

,

Clean tags

B0+ - Run1-3 data (122M BB)

314±34 Signal Events (205 tagged) Longitudinal polarization frac. fL=1.00±0.02

11

BaBar Physics Highlights: Towards Precise Measurement of Angle

0 19 0.33 0.110 23 0.24 0 14

long

long

S .C . .

Time-dependent CP Asymmetry

o

( ) ( ) ( ) 96 10 4 11 stat sys peng

Can Measure more precisely

12

BaBar Physics Highlights: Measurements of Vub In Semileptonic Decay

Exclu

siv

e m

od

es

LEP

Inclu

siv

e

stu

die

s*

* Using new Belle photon spectrum f rom b s

3( )4 70 0.44 10ub stat sysWA

V . x

13

Physics Analysis Focus of The UCSD-BaBar Group

UCSD-Babar group led the measurements of sin2 from B charmonium modes between 1998-2003. These measurement has now become “routine”. UCSD group has moved on more challenging measurements.

With the large data set BaBar is accumulating our major physics focus is now on:– Search for the decay B0 D0 K0 and measurement of CKM

angle by time-dependent CP asymmetry. – Developing massive samples of fully reconstructed B mesons

for Recoil side B meson decay studies. The aim is to measure CKM element Vub from inclusive and exclusive bu l decays

– Probe CP violation in Penguin decays such as

– Measurement of production ratio

b sss0

S S SB K K K0 0(4 )

(4 )

S B B

S B B

Brief Description of UCSD analysis follows

14

UCSD Physics Activities On Babar

• David MacFarlane (PI):

– Main author of BaBar 2002 Phys. Rev. (D) on Measurement of B oscillation and CP violation.

– Measurement of inclusive bu l spectrum (with Student Ed Hill)

– Search for Time-dependent CP asymmetry in B0 KS KS KS (with student Haleh Hadavand)

– Measurement of production ratio (with student Haleh Hadavand)

– BaBar Spokesperson

0 0(4 )

(4 )

S B B

S B B

15

UCSD Physics Activities On Babar

• Vivek Sharma (PI) : – led, as co-convener, the BaBar physics group on Exclusive B decays to Open

charm ( BRECO group) between 1999 –July 2004. All analyses involving exclusive hadronic B Charm reconstruction are developed in this group. Guided thru publication 9 PRL, 2 PR(D)RC and 2 PR(D) articles and multiple conference papers including 11 papers at ICHEP04 in Beijing.

• Physics goals of the BRECO group include:– exploration of decay modes capable of measuring CKM angle and sin2+– Decay dynamics in hadronic B decays to charm– Spectroscopy of new charm mesons from their production in B decays– Develop large sample of fully reconstructed B mesons for measuring

inclusive properties of the recoiling B meson. This paradigm shifting enterprise is already contributing to several key measurements in B decays such as Vub and measurement of photon spectrum in b s decays .

• Breco group oversees the physics analysis of about 80 BaBar physicists from US, France, Italy and Germany. It is one of the largest analysis groups in Babar.

– Guiding role in BaBar observation of CP violation (sin2) in BJ/K0 . Main author of the 2001 and 2002 PRLs on measurement of Sin2

– Member (since 2002) of the Babar Publication Board.

16

UCSD Physics Activities On Babar

• Shahram Rahatlou (Post-doc):

– Major contributions to BaBar observation of CP violation in B decays to charmonium (e.g. BJ/K0). Tools and samples he developed (BrecoUser, tFIT etc) are still used in many CP violation studies. Awarded The 2004 APS Tanaka prize for the best PhD thesis at a US university or Laboratory.

– BaBar Event Reconstruction Manager since Jan 1, 2004. • The reco manager is Responsible for development and deployment of the common aspects

of reconstruction, including the reconstruction geometry & alignment calibration model & code, the overall organization of reconstruction executables, and the reco infrastructure packages. He is responsible for the system-specific aspects of the reconstruction code to the level desired by the specific system managers. The reco manager is responsible for the technical aspects of the reco software within the five systems and their integration into the whole.

• Shahram brings a unique and comprehensive knowledge of Babar analysis tools, computing and physics to this job. His leadership has been crucial in ensuring prompt and high quality event reconstruction and allowed BaBar to analyze the data collected till the end of Run 4 in mid July and present results based on it at the Beijing ICHEP04 in mid-August !

– Developing the time-dependent CP asymmetry analysis of B0 D0 K0 for measurement of sin2+ and . First results presented at ICHEP04 (hep-ex/0408052 ).

17

UCSD Physics Activities On Babar

• Daniele delRe (Post-doc):

– Primary physicist in the development of large sample of fully reconstructed hadronic B decay (Semi-exclusive B sample).

– Co-convener of the “Recoil Side Physics” forum in BaBar in charge of coordinating and assisting in the development of a variety of inclusive measurements in the decay of the B meson recoiling against the fully reconstructed B meson (in the semi-exclusive sample).

– Led the pioneering measurement of Vub by measuring the hadronic mass spectrum in b u l from the recoil side B. Results published in PRL (92) 07180, 2004. Updated Vub results with more data (x 3) and improved observables in preparation.

– Key contributor in the migration of BaBar analysis software to the new computing model implemented since September 2003. Technical coordinator of the data and MC “skims” and tagbits for the Breco and Semileptonic Physics groups.

– Appointed co-convener of the Breco Physics group in August 2004.

18

UCSD Physics Activities On Babar

• Haleh Hadavand (PhD. Student):

– Member of BaBar charge Particle tracking group with important contributions to the Drift chamber calibration and Ks reconstruction studies. Her tracking efficiency studies provide the official BaBar “recipes” for all analyses involving branching fraction measurements.

– Primary author of the measurement of the B+/B0 production ratio from the (4s) Meson using B+J/ K+ and B0J/ Ks decays  to be published in Phys. Rev. (D).

– Primary author of the measurement of time-dependent CP asymmetry in penguin dominated mode B0 KS KS KS .

• Edward Hill (Ph.D Student):

– Drift chamber calibration.

– Migration of BaBar analysis software related to Semi-leptonic decay physics to the new computing model and data-mining for the entire semi-leptonic physics group.

– Developed algorithms for bcl background rejection for Semileptonic physics group

– Measurement of Vub from inclusive semi-leptonic decay using the photon energy spectrum from b s decays.

19

UCSD Physics: Probing CKM Angle

K K

0K0K

Look for B decays with 2 amplitudes with relative weak phase

Direct CP Asymmetry Angle

iV eub

20

• Relative size of the 2 B decay amplitudes Crucial for interference and rate of CPV

• Want rb to be large to get more interference Large CP asymmetry

– Diff. between rb=0.1 and rb=0.2 substantial for precision on

– Theory cannot calculate r reliably must measure experimentally

Left side U.T.: Ru 0.4

Color suppression: Fcs [0.2,0.5]

Expected range

Angle from B±DK±: Critical Requirement

21

Measuring rb By Reconstructing B±DK± in different D final states

ADSR

Br

BBelle : r 0.28 (90% CL)

BBaBar : r 0.23 (90% CL)68% 90

%

0 D K

Br

[d

eg

]

0.17 (90% CL) Br

0

S

B D K

K

9

0B D K

K

9

Bottomline : With low value of rb likely, need to consider multipleobservables sensitive to CKM angle B0D0K0

22

Measurement of sin(2+) with B0/B0 D(*)0K(*)0

• Interference between decay and mixing • Advantages:

• Expected large asymmetries

• Time-dependent measurement with K KS

• Probe rB in self-tagging final state KK

– Disadvantages:• Color suppressed decays: Smaller branching fractions than D• Possible competing effects from Doubly-Cabibbo-suppressed D0 decays

* A i i iub cs BrV V e e e * Acb usV V

0 0 (*)0 *

*0 0 (*)0~ 0.4ub cs

Bcb us

A B D K V Vr

V VA B D K

Strong phasedifference

b c

d d

u

s

0(*)D

0(*)K

*cbV

usV0B

b

c

d

u

s

ubV

*csV0B

b

0B

d

d

0(*)K

0(*)D

23

Study of B0/B0 DKS Decays

hep-ex/0408052

Mode BF (10-5)

BDK 6.2 ±1.2 ±0.4

BDK 4.5 ±1.9 ±0.5

124 million BB

N=64 ± 11

N=11 ± 4First Evidence

D Sidebands

Cannot distinguishB from B

Hidden strangenesswith KS in final state

Shahram Rahatlou& Vivek Sharma

24

Self-Tagging B0 D0K*0 and limit on rB

Mode BF (10-5)

BDK 6.2 ±1.4 ±0.6

BDK < 4.1 @ 90% CL

124 million BB

No Signal inVub mediatedDecay

N=45 ± 9

Charge correlation toseparate B from B

Vcb transition

Vub transition

0 0 *0

0

*0

KK

B D KD X

K

0 0 *0

0

*0 K

BXK

D KD

K

Preliminary

Results based on more data and refined analysis technique forthcoming; targeted forpublication in early 2005.

25

New Idea: Measurement of |Vub| From Semileptonic B Decays recoiling against (large samples of) Fully Recostructed B mesons

Capitalizes on UCSD Expertise in B meson Reconstruction (Breco Samples SemiExcl Samples)

Measurement of | Vub | From Inclusive and Exclusive Final States

26

• Hermiticity, so vital for SL measurements is not the best feature of Belle/ Babar detectors due to intrusion of machine into detector

• But B-factory detectors recording ever increasing samples of BB pairs (> 250 Million BB recorded already 1000 Million soon)– At the price of modest efficiency (4%), can fully reconstruct one B decay into all

hadronic final states (Breco) and examine the other (recoiling) B decay • This “Recoil side” studies perfectly suited for many Vxb studies • Much “cleaner” and more powerful than neutrino reconstruction a la CLEO • This is the most promising way for the future Vub and other Semileptonic

measurements

Beginning of an Experimental Paradigm Shift in Vxb Measurements in Semileptonic Decays at B Factories

27

The Perfect (4S) Event: Example of Recoil Side Analysis

In this (rare) case all particles were

sprayed within fiducial volume of detector

Replace this with your Favourite Vxb modee.g: b u l

28

Require Lepton (p*>1.0GeV)

S/B~0.3

S/B~2.5

Hadronic B Decay Reconstruction Rate: 4000/ fb-1

World’s largest sample of Fully reconstructed B mesons 1,000,000 and growing!

80fb-1

Full B reconstruction on one sideprovides kinematic constraints andBackground reduction allowing Important inclusive B decay Measurements like Vub.

Largely the work of UCSD postdoc Daniele delRe

29

Brecoil

BrecoD* Y(4S) l

Xu

Reco side Recoil side

•MX reconstruction•Kinematic constraints to improve MX resolution

Y(4s)

Xu

l

BY(4s)

D*

B missing mass

squared

B Candidate Mass

Recoil Side B Decay Rate Measurement : Technique

Can measure Neutrino 3-vector

30

Resulting MX Spectrum clearly separates b c l & b u l

167 21 signal events

3 4.92 0.39 0.36 0.46 10 stat sysub theoV

2 8q

1.7Xm

31

Measurements of |Vub| from b u l

Most Measurements are systematic limited or model dependent.

The Recoil side method has the best potential for precise measurementof |Vub| with larger data samples already available

ucsd

Daniele delRe & Ed Hill (UCSD)

32

Exclusive Final States: B () l

Approach similar to the inclusive analysis but

resonances are exclusively and fully reconstructed on recoil side.

We measure, very cleanly and over large kinematic range:

In Breco SampleIn Breco Sample

As Lattice calculations become more robust, measurement of B l rate over large kinematic range may lead to one of the best measure Vub precisely.

Experimental measurement is statistics limited

0 4( ) (2.57 0.52 0.59 ) 10stat systB B l

0 4( ) (1.08 0.28 0.16 ) 10stat systB B l

B±l

B±l

B0l

B0l

0B l

33

0 0

(4 )1.006 0.036( ) 0.031( )

(4 )

S B Bstat sys

S B B

0 0

From clean samples of

/

/

SB J e e K

B J e e K

Measure ratio of branching fractions:

0 0 0

/

/ S

B J Kand

B J K

Determine production ratio

assuming isospin:

0 0 - (4 ) and Rates : Needed for all Br. Ratio MeasurementsS B B B B

Haleh HadavandDavid MacFarlane

Accepted in PR(D) RC

34

Determining KS+ - Tracking Efficiency Correction

Precise data and MC comparison

to determine efficiency correctionin bins of trans. momentum (Pt) and polar angle for various drift chamber high voltage conditionsduring data taking periods.

Algorithm and “recipe” is now a BaBar standard.

Hadavand&

MacFarlane

35

CPV In Pure s-Penguin Decay B0KS KS KS

• New probe of CPV in s-penguin decays, clean signal

• Perform Ks and B vertexing using 5 layer Silicon tracker (technique pioneered by BaBar and tested on BKs0

sample). Often one of three Ks decays inside SVT.

• Reconstructed B vertex resolution sufficient for time-dependent CPV measurement a la B J/ KS

• First analysis of its kind, currently “blind”, expect public results and publication by early 2005.

• CPV precision expected to be statistics limited, will improve with rapidly accumulating BaBar data

yx

-

~4 m

Inflated Beam

Beam~200 m

0B

+

K0s

~30 m

+-

K0s

+

-

K0s

KS

KS

KS

90 10 signalafter bkgnd subtraction

Hadavand

36

UCSD-Babar Physics Outlook

• Golden years of Babar physics productivity enabled by excellent PEP-II running and success of the new Babar computing model

• UCSD-Babar physicists continue to play a key role in BaBar productivity by contributing to physics and computing leadership, service tasks and by performing outstanding and topical analyses.

• The UCSD-Babar group’s planned near-term physics focus is on– Strategies for measurement of , particularly B0/B0 D(*)0K(*)0

– Determination of |Vub| with the novel recoil side method

• Inclusive bul measurements• Exclusive bul final states (exploring new ideas such as that of

Grinstein & Pirjol hep-ph/0404250 )

– Innovative new probe of CPV in s-penguin modes with B0 KSKSKS